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Ultrafast Time-Domain Spectroscopy Reveals Coherent Vibronic Couplings upon Electronic Excitation in Crystalline Organic Thin Films
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Physical Insights into Light Interacting with Matter

Ultrafast Time-Domain Spectroscopy Reveals Coherent Vibronic Couplings upon Electronic Excitation in Crystalline Organic Thin Films
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  • Somayeh Souri
    Somayeh Souri
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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    Orcidhttps://orcid.org/0009-0005-7838-5718
  • Daniel Timmer
    Daniel Timmer
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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    Orcidhttps://orcid.org/0000-0001-7541-8047
  • Daniel C. Lünemann
    Daniel C. Lünemann
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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    Orcidhttps://orcid.org/0000-0003-2077-3062
  • Naby Hadilou
    Naby Hadilou
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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  • Katrin Winte
    Katrin Winte
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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  • Antonietta De Sio
    Antonietta De Sio
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    Center for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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  • Martin Esmann
    Martin Esmann
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    Center for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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    Orcidhttps://orcid.org/0000-0002-2329-9696
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    Franziska Curdt
    Institut für Biologie, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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  • Michael Winklhofer
    Michael Winklhofer
    Institut für Biologie, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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  • Sebastian Anhäuser
    Sebastian Anhäuser
    Fachbereich Physik, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, Germany
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  • Michele Guerrini
    Michele Guerrini
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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  • Ana M. Valencia
    Ana M. Valencia
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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    Orcidhttps://orcid.org/0000-0003-0095-3680
  • Caterina Cocchi
    Caterina Cocchi
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    Center for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
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  • Gregor Witte
    Gregor Witte
    Fachbereich Physik, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, Germany
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  • Christoph Lienau*
    Christoph Lienau
    Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    Center for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    Research Centre for Neurosensory Sciences, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    *[email protected]
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    Orcidhttps://orcid.org/0000-0003-3854-5025
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The Journal of Physical Chemistry Letters

Cite this: J. Phys. Chem. Lett. 2024, 15, 44, 11170–11181
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https://doi.org/10.1021/acs.jpclett.4c02711
Published October 31, 2024

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The coherent coupling between electronic excitations and vibrational modes of molecules largely affects the optical and charge transport properties of organic semiconductors and molecular solids. To analyze these couplings by means of ultrafast spectroscopy, highly ordered crystalline films with large domains are particularly suitable because the domains can be addressed individually, hence allowing azimuthal polarization-resolved measurements. Impressive examples of this are highly ordered crystalline thin films of perfluoropentacene (PFP) molecules, which adopt different molecular orientations on different alkali halide substrates. Here, we report polarization-resolved time-domain vibrational spectroscopy with 10 fs time resolution and Raman spectroscopy of crystalline PFP thin films grown on NaF(100) and KCl(100) substrates. Coherent oscillations in the time-resolved spectra reveal vibronic coupling to a high-frequency, 25 fs, in-plane deformation mode that is insensitive to the optical polarization, while the coupling to a lower-frequency, 85 fs, out-of-plane ring bending mode depends significantly on the crystalline and molecular orientation. Comparison with calculated Raman spectra of isolated PFP molecules in vacuo supports this interpretation and indicates a dominant role of solid-state effects in the vibronic properties of these materials. Our results represent a first step toward uncovering the role of anisotropic vibronic couplings for singlet fission processes in crystalline molecular thin films.

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Organic semiconductor thin films have garnered significant attention in recent years due to their potential applications in advanced flexible optoelectronic devices such as organic photovoltaics, light-emitting diodes, and field-effect transistors. (1−3) A crucial aspect of these materials is their anisotropic optical and charge transport properties, which arise from the shape anisotropy of the molecular entities causing an anisotropic molecular packing in the solid state. (4−6) This anisotropy plays a vital role in determining the efficiency and performance of devices, as they directly influence the absorption of light, charge mobility, and overall electronic behavior of the organic films.
Other important characteristics of organic semiconductors are their particular pronounced vibronic couplings, which affect not only their energy landscape but also play an important role in their excited state dynamics and transport properties. (7−9) While these characteristics have been investigated in detail, (4,5) much less is known about the effect of the molecular alignment on the coupling between electrons and vibrational modes in organic solids, since the majority of experimental studies to date have been carried out on rather disordered samples. Here, organic single crystals or thin films with large crystalline domains offer the possibility to resolve these anisotropies by performing direction- and polarization-resolved measurements. (10)
In such thin films, the anisotropic molecular arrangement is expected to result in vibronic couplings that go beyond the common Condon approximation, (11−13) in which the electronic transition dipole moment is independent of the nuclear coordinates and optical transition amplitudes are purely defined by the overlap of vibrational wave functions. Specifically, Herzberg–Teller couplings (14) are expected if derivatives of the transition dipole moment along nuclear coordinates arise from nonadiabatic mixing of several electronically excited states, (13,15) and conical intersections in the excited state potential energy surfaces may greatly influence the quantum dynamics after optical excitation. (16,17) Emerging evidence indicates that such vibronic couplings may significantly affect the singlet fission processes in organic materials, (18−23) where the role of vibronic couplings, and conical intersections in particular, are presently discussed. (24−29)
Perfluoropentacene (PFP) thin films, epitaxially grown on alkali halide substrates, are particularly interesting model systems to further extend the study of these topics. (10,30) When grown on KCl(100) and NaF(100) substrates, they exhibit the same crystal structure with the characteristic herringbone packing motif but with different molecular orientations relative to the surface normal. In fact, the PFP molecules are standing almost upright on NaF(100), their long axis is oriented almost parallel to the substrate on KCl(100). (10,30) On both substrates, the molecules form large, laterally extended domains. This structural peculiarity has enabled detailed directional polarization-resolved infrared vibrational spectroscopy and fission yield studies. (10,30) Significant differences in polarization-dependent singlet fission yields have been observed in these crystals, suggesting that their anisotropic molecular packing affects singlet fission. (31) Broadband pump–probe spectroscopy showed that the slip-stack molecular packing along the b⃗-axis of the crystals enhances singlet–triplet mixing and is favorable for singlet fission. (31) The time resolution in these measurements, (31) however, was not yet sufficient to resolve coherent vibrational motion. Therefore, little is known so far about the interplay between molecular packing and vibronic couplings in crystalline PFP thin films.
Effects of the molecular orientation on the infrared spectra of crystalline PFP films have been investigated in ref., (30) revealing vibrational Davydov splitting and collective mode polarizations as signatures of intermolecular couplings in the crystal. For the coupling to electronic excitations, however, Raman-active modes are most relevant. In case of PFP thin films, first results of Raman measurements have been obtained on highly oriented pyrolytic graphite. (32) On graphite, however, PFP forms a π-stacked phase, different from the herringbone packing on alkali halides. (33) Stronger vibronic couplings are expected for perfluorinated acenes than for nonfluorinated acenes, since the higher mass of fluorine than hydrogen enhances the reduced mass. (34) Consequently, also the carbon atoms of the backbone have a much larger vibration amplitude, making it relevant to investigate vibronic couplings in PFP films in more depth.
Here, we use time-resolved vibrational spectroscopy with 10 fs time resolution and Raman spectroscopy to study vibronic couplings upon electronic excitation in crystalline PFP thin films grown on KCl(100) and NaF(100) substrates. Our results show that vibronic couplings to high-frequency carbon–carbon-stretching modes with 25 fs period induce large amplitude modulations of the nonlinear spectra. Polarization-dependent multimode interference patterns are signatures of the effect of molecular orientation on the vibrational motion which go beyond simplified single-molecule pictures for the optical response. Our results present a step forward in studying the effects of molecular order on vibronic couplings and singlet fission in molecular crystals.
We experimentally study the optical properties of single crystalline PFP thin films epitaxially grown on NaF(100) and KCl(100) substrates with thicknesses of 200 and 100 nm, respectively. These films were prepared under high vacuum conditions by molecular beam deposition and characterized in earlier work using several techniques including X-ray diffraction (see Figure S1 in the Supporting Information), atomic force microscopy (AFM), polarized optical microscopy, as well as infrared and UV/vis spectroscopy (see also Figure S2 in the Supporting Information). (10,30) On both substrates, the PFP molecules crystallize in their bulk phase with a herringbone structure exhibiting a rectangular but slipped stacking of the two molecules in the unit cell (35) (Figure. 1a,b). In the resulting triclinic lattice, the unit vector a⃗ has a length of 15.5 Å and points approximately along the long axis of the PFP molecules. On the other hand, the b⃗ vector (4.5 Å) is aligned along the slip-stacking direction while the c⃗ vector (11.5 Å) points along the herringbone stacking direction. (30,35) On NaF (Figure. 1a), the molecules stand almost upright on the substrate and b⃗ coincides with the ⟨010⟩ azimuth direction of the substrate. On the other hand, on KCl (Figure. 1b), the molecules lie recumbently on the surface (10) and their long axis encloses a small angle of ≃8° with respect to the substrate plane. Here, b⃗ closely matches the ⟨011⟩ azimuth direction of the substrate while the c⃗ vector points toward the substrate surface plane.

Figure 1

Figure 1. Correlation between crystalline orientation and optical response of perfluoropentacene (PFP). Molecular stacking patterns of (a) a 200 nm thick single-crystalline PFP film on a NaF(100) substrate and (b) a 100 nm thick single-crystalline PFP layer on a KCl(100) substrate. On NaF(100), with upright standing molecular orientation, the (b⃗c⃗)-plane of PFP is parallel to the substrate. For KCl, with recumbent molecular orientation, the (a⃗b⃗)-plane is parallel to the substrate. (c, d) Scheme of the polarization of the co-linearly polarized pump and probe lasers used to selectively excite and probe PFP on NaF (c) and PFP on KCl (d) with light polarized along one of the crystal axes. Differential transmission (ΔT/T) map recorded for linear polarization along the (e) b⃗- and (f) c⃗-axes of PFP on NaF and along the (g) b⃗- and (h) a⃗-axes of PFP on KCl. (i) Time-averaged ΔT/T spectra obtained from the ΔT/T maps in (e-h). The polarization of laser pulses along a specific crystal orientation are color-coded as in (e-h). (j) Cross sections of the ΔT/T maps in (e-h) as a function of delay time for a fixed probe energy, indicated by the dashed lines in (e-h). The ΔT/T for polarization along a⃗, magnified by a factor of 10 in (h-j) stems from a small number of residual minority domains oriented along b⃗.

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AFM imaging and polarized microscopy experiments revealed the formation of extended, crystalline rotational domains with dimensions of several tens of microns, (10) occurring in orthogonal domains due to the surface symmetry of the alkali halide surfaces. This film structure offers unique opportunities for performing linear and nonlinear optical experiments on single-crystalline domains, even if the spatial resolution does not reach the diffraction limit. (31) Figure. 1c,d schematically illustrate the incident polarization of the pump- and probe pulses in relation to the crystal axes of the films. On NaF(100), with the molecular long axis pointing nearly perpendicular to the substrate plane, linearly polarized light at normal incidence can excite the crystalline molecular film with the axis of polarization containing the b⃗ or c⃗ vectors, depending on the azimuthal polarization. On KCl(100), with recumbent molecular orientation, the incident electric field can be polarized along the a⃗- or b⃗- axes (see Figure S2 of the Supporting Information). (31) Such an alignment of the incident polarization has a significant effect on the nonlinear optical response of the crystals. This is demonstrated in Figure. 1e-h showing the results of ultrafast pump–probe experiments. The targeted addressing of individual azimuthal domains is possible because the PFP films form laterally extended areas (<500 μm) with a preferred orientation. Polarization microscope images show that more than 90% of such areas exhibit only one azimuthal orientation with only small admixtures of the 90° rotation domains.
We use this special film geometry for time- and polarization-resolved pump–probe measurements, employing broadband pulses with a spectrum covering a range from 590 to 810 nm, i.e., 1.53 to 2.1 eV. (36) Their 10 fs pulse duration (full width at half-maximum of their intensity profile, see Section 3 of the Supporting Information) is short enough to resolve vibronic couplings to all high-frequency vibrational modes of the thin films. The pulse spectrum fully overlaps the lowest-lying singlet exciton (XS1) of the PFP crystals at about 1.8 eV and all relevant vibrational sidebands (see Figure S2 in the Supporting Information). Collinearly polarized pump–probe measurements are performed at room temperature and under ambient conditions. The pulses are focused to a spot size of around 30 μm on the sample, sufficient to isolate oriented single-crystalline domains. The pump-induced change in probe transmission ΔTT(td,ED) is recorded as a function of pump–probe time delay td and detection energy ED. More details of the experimental setup are described in previous work (see also the Methods section). (36−40) The fluence of pump and probe pulse is carefully controlled to ensure that all experiments are performed in the regime of third-order nonlinearities (Section 4 of the Supporting Information). Resulting pump–probe maps are displayed in Figure 1e-h for time delays between 200 fs and 1 ps.
For PFP on NaF(100), we first set the polarization of the pump and probe pulses parallel to the b⃗-axis of the film. To do this, we maximize a distinct excited state absorption (ESA) band that appears at energies below the singlet exciton resonance. This ESA is observed as a negative signal, ΔT/T < 0, in the range between 1.55 and 1.7 eV in Figure 1i (blue line), similar to earlier pump–probe measurements. (31) The ESA has been assigned to an excimer state with its transition dipole moment oriented along the b⃗-axis. (31) Here, we take this ESA as a marker that pump- and probe are oriented along b⃗ as it vanishes almost completely when rotating the laser polarization by 90°, i.e., when exciting and probing the sample with light that is linearly polarized along c⃗ (red curve in Figure 1i). Variation of the laser polarization confirms that the ESA is minimized for the setting shown in Figure 1f. This contrast in ESA ensures that a crystalline region with well-defined molecular orientation is excited and thereby allows for the identification of individual rotational domains in the PFP films. Not only the amplitude of the ESA but also the signature of XS1 in the pump–probe spectra changes significantly when rotating the laser polarization. All experiments show an enhanced transmission, ΔT/T > 0, near XS1. This reflects ground state bleaching (GSB) and stimulated emission (SE) from the singlet exciton. Importantly, the center of XS1 shifts spectrally from 1.78 eV for a polarization along b⃗ (blue curve in Figure 1i) to 1.74 eV for a polarization along c⃗ (red curve in Figure 1i). A similar spectral shift of 30 meV was observed in linear UV/vis spectra of PFP on NaF(100) between XS1 for excitations along b⃗ and c⃗ and assigned to an excitonic Davydov splitting in the molecular crystal (see Figure S2). (41) PFP molecules with their optical transition dipole aligned along the short axis can coherently exchange energy with their nearest neighbors within and across the unit cell by near-field dipole–dipole coupling. In the strong coupling limit, this result in a delocalization of the electronic wave function across several molecules. (42) The resulting Davydov components of the excitons are split in energy and have transition dipole moments oriented along the b⃗- and c⃗-axes, respectively. For PFP on NaF(100) both the energy splitting between the two states and the orthogonal orientation of the dipole moments are resolved in the pump–probe measurement (Figure 1e,f).
In contrast, for PFP on KCl(100), the pump and probe laser polarizations can be aligned along the a⃗- or b⃗-axes. For excitation along b⃗, the recorded pump–probe map (Figure 1g) is basically identical to that in Figure 1e (NaF substrate, b⃗-axis), except for an overall reduction in amplitude by a factor of 2 that reflects the decrease in film thickness from 200 nm on NaF(100) to 100 nm in KCl(100). For excitation along a⃗, the amplitude of the pump–probe signal largely reduced by more than one order of magnitude (note that the ΔT/T for excitation along a⃗ in Figure 1h-j are magnified by a factor of 10. In this case, XS1 cannot be excited since its dipole moment is oriented perpendicular to the laser polarization. Polarization-resolved UV–vis spectra indicate (10) (see Figure S2) that the lowest exciton resonance with dipole moment orientation along a⃗ appears at 2.8 eV, i.e., it lies outside the spectral window of the pump laser. Consequently, the pump–probe signal shown in Figure 1h probes mainly residual excitations of XS1 that are oriented along b⃗. These signals therefore likely arise from a small admixture of 90° rotation domains with exciton transition dipole moments oriented along the b⃗-axis. The relative contribution of the low-energy ESA to the signal is as large as in Figure 1e.
All pump–probe transients show substantial oscillatory modulations on top of these incoherent signal contributions, which reflect pump-induced vibrational motion in the thin films. Representative signals are shown in Figure 1j for the detection energies marked by dashed lines in Figure 1e-h. To analyze these oscillations in more detail, we first compare transient pump–probe spectra for PFP on NaF(100) for excitations along b⃗ (Figure 2a) and c⃗ (Figure 2b), respectively. On these substrates, spurious cross-phase modulations induced by coherent light scattering contributions during and shortly after the pump–probe overlap are so weak that their amplitude is less than 10% of the desired pump–probe signal. This is verified via reference measurements on the bare substrate. The detection energies are selected to maximize the modulation contrast of the oscillations with a period of 25.3 fs (164 meV, 1320 cm–1) that dominate these signals. This oscillation period agrees very well with a mode period of 24.9 fs (166 meV, 1340 cm–1) estimated from the vibronic side peaks of UV/vis spectra (see Figure S2). The modulation contrast is taken as the ratio between the peak-to-peak oscillation amplitude on the ΔT/T transients and the cycle-average of ΔT/T and directly measures the strength of the vibronic coupling to the corresponding vibrational mode. (43) For both polarizations, the data show a pronounced modulation with a period of 25 ± 1 fs. Specifically, for polarization along c⃗ the modulation contrast is ∼30%. This demonstrates that the excitonic state is strongly coupled to a high-frequency mode of the PFP molecules at 1320 cm–1 and that optical excitation of the thin film induces coherent vibrational wavepacket motion along the corresponding nuclear coordinate.

Figure 2

Figure 2. Transient differential transmission ΔT(td,ED)/T recorded for PFP on NaF(100) with pulses polarized (a) along the b⃗-axis at a detection energy of 1.78 eV and (b) along the c⃗-axis at a detection energy of ED = 1.75 eV. The polarization direction is illustrated in the insets. Both plots show a dominant modulation with 25 fs period although for polarization along b⃗, low-frequency oscillation beatings are more pronounced. The solid red and dashed blue lines are biexponential decay functions and are introduced to guide the eye.

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In a simplistic displaced harmonic oscillator (DHO) model, (43) in which the electronically excited (XS1) state couples to the vibrational mode of an individual harmonic oscillator, this modulation amplitude is expected for a dimensionless displacement of Δ ≈ 0.6 ± 0.1. This displacement corresponds to a Huang–Rhys factor S = Δ2/2 = 0.18, representing the average number of vibrational quanta involved in the electronic transition. (12,44) For an excitation along the b⃗-axis, the pump–probe transient is still predominantly modulated with a 25 fs period. Here, however, the modulation amplitude is slightly reduced, and the high frequency modulation interferes with an additional lower-frequency mode with a period of 86 ± 2 fs (48 meV, 384 cm–1). This finding already suggests that the vibronic couplings in the thin films strongly depend on the polarization direction of the incident light pulses.
For a more quantitative assessment of these vibronic couplings, we calculate residual maps of the coherent oscillations at larger delays. To do so, we fit a multiexponential decay ⟨ΔT⟩(td,ED) to the pump–probe transients for each ED (see Section 5 of the Supporting Information) and subtract it from the data. This decay characterizes the incoherent contributions to the pump–probe transients. The resulting residual map R(td,ED) = (ΔT(td,ED) - ⟨ΔT⟩(td,ED))/T is depicted in Figure 3a for PFP on NaF(100) excited with light polarized along b⃗. Pronounced oscillations in these residuals are observed in the probe energy range between 1.73 and 1.81 eV, close to the two Davydov components of the lowest energy singlet exciton (see Figure S2 in the Supporting Information). A distinct node in the modulation appears at 1.81 eV. The modulation amplitude is significantly larger for energies below 1.81 eV than for higher energies. Cross sections of the residuals in Figure 3b for energies of 1.78 eV (black) and 1.85 eV (red), chosen to maximize the oscillation amplitude on either side of the node, demonstrate this asymmetry. We emphasize that such a behavior cannot be explained based on a simple DHO model for which the analytical solutions of the pump–probe spectra are well-known. (43,45) In the DHO model, the dependence of the modulation amplitude on ED follows the first spectral derivative of the exciton resonance d(ΔT(ED)/T)/dED. For a characteristic Lorentzian or Gaussian line shape of this resonance, a symmetric variation of the modulation amplitude is predicted by the model around the central node, (45) in contrast to what is seen experimentally.

Figure 3

Figure 3. (a) Residual map showing the oscillatory modulation of the ΔT/T signals in Figure 1e, recorded for PFP on NaF for co-linearly polarized pump and probe pulses polarized along the b⃗-axis of PFP. In these residuals, slowly decaying incoherent ΔT/T signals have been subtracted from the pump–probe data to emphasize the oscillatory modulation induced by coherent lattice vibrations. The residuals are shown for waiting times between 0.12 and 2.0 ps. (b) Cross section through the residual map in (a) for two representative probe energies of 1.78 eV (black) and 1.85 eV (red), marked as dashed line in (a). The signals are dominated by a high-frequency oscillation at 25 fs and superimposed by several different beating patterns. (c-e) Cross sections through the residual maps for PFP on NaF (c⃗-axis) (c), PFP on KCl (b⃗-axis) (d) and PFP on KCl (a⃗-axis) (e). The cross sections are shown at probe energies of 1.78 eV (black) and 1.85 eV (red) and for time delays between 0.12 and 2.0 ps. In (b-e), the residuals at the two probe energies are vertically shifted by 10% for clarity.

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For PFP on both substrates (Figure 3b-e) we find that the residuals are dominated by large amplitude 25 fs oscillations, regardless of the laser polarization. These oscillations persist for up to 6 ps, the maximum range of time delays chosen in our experiments. For excitation along b⃗, these oscillations are superimposed by lower-frequency oscillations with an 85 fs period. The same characteristic beating pattern is seen for b⃗ excitation of PFP on both NaF and on KCl substrates (Figures 3b and 3d, black lines). Also, for excitation along a⃗ on KCl(100) (Figure 3e), the same beating pattern but now much reduced in amplitude and superimposed by noise fluctuations. The amplitude is reduced since only a small admixture of 90° rotation domains with exciton transition dipole moments oriented along the b⃗-axis is excited.
A substantially different beating pattern arises when exciting and probing PFP on NaF(100) with polarization along c⃗. In this case (Figure 3c, black line), the residuals are largely dominated by the 25 fs oscillations and slower beating patterns are much weaker. Thus, for PFP on NaF(100), the oscillatory modulation of the pump–probe signal and, thus, the vibronic couplings, significantly depend on molecular orientation in the thin film. Such a pronounced anisotropy of the nonlinear response cannot be explained by a DHO model where a single electronic state is coupled to one or several harmonic oscillator modes. Instead, this response is a signature of anisotropic vibronic couplings in a molecular crystal in which delocalized, Davydov-split exciton resonances are coupled to vibrational modes in the crystalline solid.
To validate this conclusion, we present in Figure 4 the amplitude of the Fourier transforms of these residuals as a function of detection energy and mode frequency. For calculating the Fourier transform spectra, we used pump–probe transients for waiting times between 0.12 and 6 ps, except for the measurement performed on KCl with a⃗-axis excitation, where 3 ps scans were employed. Fourier transform spectra are calculated directly from the residuals, without applying any window functions. Maps of the amplitude of these spectra after integration along ED are presented as black lines in Figure 5. These data are compared with polarization-resolved spontaneous Raman scattering measurements (red lines) performed on the same samples used for pump–probe spectroscopy. The Raman spectra were recorded with off-resonant excitation at 785 nm (1.58 eV). The spatial resolution in the measurement was ∼1 μm, ensuring excitation of single-crystalline domains.

Figure 4

Figure 4. Normalized energy-resolved Fourier transform spectra obtained from the residuals of the ΔT/T maps in Figure 1e-h for excitation and probing along the (a) b⃗- and (b) c⃗-axis of PFP/NaF(100) and along the (c) b⃗- and (d) a⃗-axis of PFP/KCl(100). The amplitudes of the Fourier transform spectra are shown as a function of wavenumber and detection energy ED. The amplitude of the data in (d) is 10-times smaller than that in a-c since only a small portion of minority domains with b⃗-orientation are excited. The Fourier transform spectra are dominated by vibrational modes around 1320 cm–1, 774 cm–1, 384 cm–1 and 178 cm–1. Cross sections along ED for the 384 cm–1 mode are displayed in the insets. Note the change in spectrum of this mode for c⃗-axis excitation PFP/NaF(100) in comparison to that for excitation along b⃗.

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Figure 5

Figure 5. Fourier spectra (black lines), integrated along the probe energy in Figure 4 and recorded for excitation along the (a) b⃗- and (b) c⃗- axis of PFP/NaF(100) and along the (c) b⃗- and (d) a⃗- axis of PFP/KCl(100). As in Figures 1h and 2d, the amplitude of the spectrum in (d) is 10 times smaller since only a small portion of minority domains with b⃗-orientation are excited. Corresponding off-resonance Raman spectra recorded for linearly polarized excitation at 785 nm are shown in red. The Raman spectra have been shifted vertically by −0.3 for clarity.

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We clearly identify 9 vibrational modes in the Fourier transform spectra. Their resonance frequencies and normalized amplitudes are summarized in Table 1. The resonance frequencies are reasonably close to those deduced from the Raman measurements, while the mode amplitudes that are detected in both experiments are substantially different. Since the spectral width of our excitation pulses covers the entire absorption band of PFP, the laser profile does not significantly affect the mode amplitudes. (46) The frequencies seen in the Raman spectra agree well with those reported in ref. (32) and with Raman measurements of PFP thin films in the π-stacked phase on graphite substrates. (33) Most peaks, both in time-resolved and Raman spectroscopy, show line widths of less than 8 cm–1, corresponding to vibrational dephasing times of more than 1.5 ps. This value, partly limited by the finite scan range in the pump probe measurements and by the resolution of the Raman spectrometer, is a lower limit of the actual dephasing time. In the off-resonant Raman measurements, these narrow lines reflect long-lived vibrational wavepacket motion in the electronic ground state of the PFP crystals. We take the narrow line widths seen in the pump–probe spectra as the characteristic sign that also the persistent modulation of the pump–probe transients, lasting for up to 6 ps, probes coherent vibrational wavepacket motion in the electronic ground state of the PFP crystals.
Table 1. Vibrational Mode Frequencies and Amplitudes of Crystalline PFP Thin Films Deduced from Fourier Transforms of the Pump-Probe Residuals and from the Off-Resonant Raman Spectraa
ModeExperimental |FT| spectrumExperimental Raman spectrumExperimental ref  (32)Simulated Raman spectrum
Mode number (30)Symmetry (30)Frequency (cm–1)Amplitude (norm.)Frequency (cm–1)Amplitude (norm.)Frequency (cm–1)Frequency (cm–1)Amplitude (norm.)
#16Ag1780.321790.151781730.09
#22Ag2840.112840.102802750.04
#36B2g3840.853921.003893960.01
#42Ag4510.084530.094504420.00
#45Ag4900.144940.014924820.10
#58Ag  6730.036706910.03
#62B3g7740.237750.167707710.01
#75Ag  12100.03120711980.00
#80Ag  12380.00123612330.53
#84Ag13201.0013150.27131713551.00
#86Ag13360.38  133713840.57
#99Ag15870.0615830.08159115730.10
a

The experimentally measured mode frequencies are compared to values from ref (32) and from the DFT calculations performed in this work.

The coherent modulations of the pump–probe spectra are dominated by high-frequency vibrations around 1320 cm–1. In this frequency region, the dependence of the Fourier transform spectra on the detection energy is very similar for both substrates, and apparently does not depend on the polarization direction of the excitation laser (Figure 4). The corresponding Fourier transform spectra (Figure 5) show not only a single sharp line centered at 1320 cm–1 but also faint sidebands that can be interpreted as signatures of Davydov splittings. (30) Importantly, the Fourier transform spectrum of the 1320 cm–1 band also displays a broadband pedestal with a width of about 30 cm–1. The spectral width of the pedestal reflects a faster partial decay of the 25 fs modulation on the pump–probe transients with a damping time of about 500 fs. This partial decay is also seen in Figure 3, while it is absent in the Raman spectra. We assign it to coherent vibrational wavepacket motion in an electronically excited state of the PFP crystals that is triggered by the pump laser. The line width of the off-resonant Raman spectra is defined by the dephasing time of the vibrational wavepacket motion in the electronic ground state of PFP. (47) For off-resonant scattering, the shape of the excited state potential energy surface only affects the intensity of each Raman mode (Albrecht terms A’ and B’ in ref. (47)). In contrast, the pump laser in the transient absorption measurements is resonant with the exciton transition. It launches coherent vibrational wave packets both in the optically excited state XS1 and, by stimulated impulsive Raman scattering, (48,49) in the electronic ground state. The pump–probe measurements are sensitive to the dynamics of both wave packets. (50,51) Relaxation processes in the electronically excited state manifold may result in a rapid damping of the coherent wavepacket motion and, thus, in a broader line width in the Fourier transform spectra. (51−53) Therefore, the pump–probe measurements allow us to distinguish excited state dynamics from vibrational ground state motion.
A similar pedestal in the Fourier transform spectra, though with reduced spectral width, is also seen for the low-frequency mode at 384 cm–1 (85 fs period), which causes the beating in the pump–probe residuals in Figure 3. This band, like the frequency mode, monitors not only ground state vibrations but also excited-state wavepacket motion. More importantly, for this band, the dependence of the Fourier transform spectra on the probe energy is highly sensitive to the orientation of the PFP crystals and the laser polarization. This sensitivity is illustrated in the cross sections through the Fourier transform maps along the detection energy axis at a frequency of 384 cm–1, shown in the insets of Figure 4 a-d. While very similar intensity profiles are seen for b⃗-axis excitation of PFP on both NaF and KCl, the pattern is distinctly different for c⃗-axis excitation of PFP on NaF(100). This is likely the most striking evidence of the effects of molecular orientation on the vibronic Davydov-splitting that we find in the present data. It is worth noting that such shifts are absent for other vibrational modes. For example, the modes at 774 and 178 cm–1, show the same sharp line profile in both the Fourier transform spectra and Raman spectra. For these modes, the dependence of the Fourier transform spectra on the detection energy is independent of substrate and laser polarization.
To rationalize the experimental findings, a detailed theoretical modeling of vibronic couplings in PFP crystals is necessary. This theoretical characterization should extend the DHO model, typically used to describe vibronic couplings in molecular systems. In particular, Herzberg–Teller couplings (14,54,55) should be incorporated to account for coordinate-dependent transition dipole moments. While the theoretical framework is in principle well developed, (56−58) its effective application requires more detailed information about the excited state potential energy surfaces of the PFP crystals. Such information can be obtained from multidimensional electronic spectroscopy (37,38,44,59) and experiments in this direction are currently underway.
As an initial step toward interpreting the reported experiments, we present calculations of the Raman spectra of isolated PFP molecules in vacuo to identify the vibrational modes that mostly contribute to the measured signals. Previous calculations of the infrared-active modes of PFP crystals (30) indicated a resemblance with the vibrational modes obtained for an isolated PFP molecule in vacuo, except for expected Davydov splitting of some of the modes and small energetic shifts. This analogy confirms that single molecule calculations can provide an accurate mode assignment.
The vibrational modes of an isolated PFP molecule in vacuum are calculated in the harmonic approximation in the framework of density-functional theory. (60) For computational details, see the Methods section. The IR spectrum reported in Figure 6a (gray shaded area) indicates a predominant activity in the high-frequency region above 800 cm–1 where the C–C modes dominate. This result agrees well with the one reported in ref. (30) The calculated Raman spectrum of the PFP molecule (Figure 6b, red curve) is also dominated by an intense activity in the high-frequency region (1200–1600 cm–1) where the deformation modes of the benzene rings have their normal frequencies. These modes are ubiquitous in carbon-conjugated molecules and appear with similar intensity also in pentacene and other oligoacenes. (61)

Figure 6

Figure 6. (a) Infrared (IR, gray area) and resonant Raman spectra (red) of an isolated PFP molecule in vacuo calculated using DFT with the PBE functional. (b) Visualization of selected Raman active modes. C atoms are shown in gray and F atoms in cyan. The arrows indicate the directions of the atomic displacements. Both spectra are broadened by a Lorentzian function with a fwhm of 5 cm–1.

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The calculated Raman spectrum, however, partially contrasts with the experimental data (Figure 5), where only a single strong peak at ∼1320 cm–1 and a faint sideband at 1336 cm–1 are seen. The other Raman-active peaks predicted by the single-molecule calculation are absent in the measurements. This behavior can be understood considering the stiffness of the crystalline arrangements in which the molecular backbones hosting the C–C modes have considerably fewer degrees of freedom compared to the gas-phase. The results of the calculations indicate that the 1320 cm–1 mode is a symmetric, in-plane deformation of the fused carbon rings in which the C atoms predominantly move along the short axis of the molecule, corresponding to the direction of the HOMO–LUMO transition dipole moment of the PFP molecule (Figure 6b). The lowest energy excitation in the crystalline phase shares the same intramolecular polarization, explaining why the 1320 cm–1 mode governs the vibronic coupling of the XS1 excitons in the single crystals. Nearest-neighbor coupling between electronic transition dipole moments not only delocalizes the electronic excitation, forming two delocalized Davydov-split excitonic states with transition dipole moments oriented along the b⃗- and c⃗-axes; it also results in the formation of delocalized symmetric (Q+) and antisymmetric (Q–) vibrational modes by in-phase and out-of-phase superposition of the 1320 cm–1 mode of neighboring PFP molecules in the unit cell. (17,40,56) The variation of the potential energy of the two excitons along the Q+ and Q– modes may be most relevant for the wavepacket dynamics observed in the pump–probe experiments. Such an interpretation of the absorption spectrum of the PFP crystals may explain the detection energy dependence of the Fourier transform spectra reported in Figure 4.
The low-frequency region of the vibrational spectrum of PFP (150–500 cm–1) is characterized by C–F modes delocalized across the molecule and involving the motion of the heavier fluorine atoms. The C–F modes exhibit a lower relative intensity compared than the C–C ring deformation modes at higher frequencies (see Figure 6a). An exception is the mode at 396 cm–1, seen with low intensity in the simulations but with high intensity in the experimental spectra at 384 cm–1. We reiterate that such energetic discrepancies are expected and do not invalidate this comparison. This mode is connected to an out-of-plane ring bending visualized in Figure 6b. The comparison to the experimental data suggests that it is this out-of-plane bending motion that results in a vibronic coupling that is sensitive to the molecular orientation and, thus, induces the polarization-dependent beating pattern for the PFP film on NaF(100) that is seen in Figure 3b,c and Figure 4a,b.
The experimental spectra suggest that two additional modes at 178 and 774 cm–1 play a role in the dynamics. For both modes, the vibronic couplings observed in the experiment do not depend on the crystal orientation. The calculations reveal a Raman-active mode at 173 cm–1, which is a symmetric low-frequency stretching mode of the molecule involving also the motion of the fluorine atoms. On the other hand, the calculated Raman-active mode that appears at 771 cm–1 is an out-of-plane bending mode (Figure 6b).
Overall, the comparison between experiments and simulations suggests that the single-molecule calculation is not able to fully describe the vibronic complexity detected in the crystalline samples. Only the inclusion of long-range Coulomb interactions and of the periodic character of the wave functions in the model can lead to a quantitative agreement with the measurements and hence, to a convincing interpretation of the experimental observations. For the same reason, a simplified model including only a PFP dimer is likely equally unable to rationalize the vibronic couplings between the involved electronic transitions as well as to explain wave packet dynamics and detection energy dependence of the Fourier transform spectra. To achieve these goals, full-fledged simulations of the crystalline phase are required. (61,62) Despite these limitations, the presented calculations on the isolated PFP molecules suggest that in-plane and out-of-plane deformation vibrations of the carbon backbone play a dominant role for the vibronic couplings in the crystals and provide important qualitative indications to interpret the experiments in this direction.
In summary, we investigated coherent vibronic couplings to excitons of crystalline perfluoropentacene thin films epitaxially grown with different molecular orientation (lying vs standing) on KCl(100) and NaF(100) substrates. Our experimental results, combining ultrafast pump–probe spectroscopy with 10 fs time resolution and Raman spectroscopy, demonstrate different effects of vibronic couplings on the optical properties of these thin films. The pump–probe spectra show a Davydov splitting of ∼30 meV between the lowest-lying exciton transitions with dipole moments oriented perpendicular to the long axis of the PFP molecules. Persistent high-frequency oscillations of the pump–probe transients with a 25 fs period point to a predominant coupling of the excitonic transitions to a symmetric ring deformation mode of the carbon backbone with a dimensionless displacement of ∼0.6 that is insensitive to the molecular orientation on the film. Couplings to higher-frequency modes are largely suppressed. Vibronic couplings to a lower-frequency out-of-plane ring bending modes give rise to a characteristic interference pattern in the pump–probe transients that changes when varying the relative orientation between laser polarization and crystal axes. The polarization-dependence provides evidence that the coupling between excitons and this out-of-plane mode depends sensitively on the molecular orientation in the thin film. This points to a significant role of the molecular arrangement for the vibronic couplings and, therefore, potentially also for the fission of singlet excitons in these samples. DFT calculations of the Raman spectra of isolated PFP molecules in vacuo aid in assigning the relevant vibrational modes, although additional analysis including long-range Coulomb interactions and a detailed modeling of the crystalline samples, planned for upcoming work, is necessary for a complete interpretation of the measurements.
In essence, our results show that single-crystalline thin films of perfluoropentacene, or acenes in general, appear as interesting model systems for exploring the potential role of vibronic couplings and their dependence on molecular orientation on the dynamics and yield of singlet fission processes. They suggest that polarization-controlled time-resolved pump–probe and multidimensional coherent spectroscopies with 10 fs time resolution can sensitively probe coherent couplings to even the fastest vibrational modes in the organic crystals and their dependence on the molecular orientation. The present study demonstrates the ability of ultrafast time-resolved spectroscopy to detect coherent couplings of vibrational modes and electronic excitations in crystalline organic thin films and paves the way to analyze the role of vibronic couplings on singlet exciton fission processes.

Methods

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Sample Preparation and Sample Growth

The PFP (Kanto Denka Kogoyo, purity >99%) films are grown on crystalline NaF (001) and KCl (001) surfaces following the growth procedure described in ref. (10) The alkali halide surfaces are prepared by cleaving slices of about 2 mm thickness from a single-crystal rod (Korth Kristalle GmbH) in air. After transfer into the vacuum system, the substrates are annealed at 450 K to remove adsorbed water. Subsequently, the highly crystalline PFP thin films (100−200 nm) are prepared under ultrahigh-vacuum conditions by molecular beam deposition at a molecular flux of about 6 Å/min as monitored by a quartz crystal microbalance. To maximize the domain sizes, the PFP films are grown at a substrate temperature of 350 K. PFP forms epitaxially ordered adlayers of the bulk structure. On NaF(100) substrates, the molecules adopt an upright orientation with their b⃗- and c⃗-axes parallel to the surface. On KCl, the PFP molecules adopt a recumbent orientation, yielding the a⃗- and b⃗-axes parallel to the substrate surface. The crystalline structure of all samples is verified by X-ray diffraction, optical microscopy, and atomic force microscopy as detailed in ref. (10)

Coherent Vibrational Spectroscopy

For ultrafast and broadband coherent vibrational spectroscopy (63,64) (CVS) of PFP samples we use a home-built noncollinear optical parametric amplifier (NOPA) (36) that is based on the design in ref. (65) The NOPA is pumped by a Carbide (Light Conversion) laser system operated at 200 kHz repetition rate. The output spectrum of the NOPA is shown in Figure S3b, as recorded using a fast and sensitive line camera (Octoplus, e2v) with an acquisition rate of 100 kHz. The normalized root-mean square error (NRMSE) of 10000 consecutively recorded spectra at an acquisition rate of 100 kHz shows a high spectral stability of the NOPA that is mostly limited by detector shot-noise (see Figure S3b).
These NOPA pulses are compressed using chirped mirrors (DCM9, Laser Quantum) and used in a pump–probe setup. (36,38) Using a beam splitter, the same laser spectrum is used as the pump and the probe. An in-line interferometer based on birefringent wedges (TWINS), (66) used to generate a phase-stable excitation pulse pair, is set to a delay of zero. Additional dispersion caused by the TWINS is compensated for by using a second pair of chirped mirrors (DCM12, Laser Quantum) in the pump arm of the setup. The time delay td between pump and probe is tuned via a motorized linear translation stage (M126.DG, Physik Instrumente). Both pump and probe are focused onto the sample using an off-axis parabolic mirror (OAP) to a spot size of around 30 × 30 μm2 at their intersection. Both beams are polarized along the same direction. A broadband achromatic half-wave plate (B. Halle) is employed to simultaneously tune the polarization of the pump and probe directly before the OAP such that both beams are always polarized in the same direction. Using a 10-μm-thick beta barium borate crystal, a cross-correlation second-harmonic frequency resolved optical gating (SH-FROG) is measured between the pump and the probe at the sample position. The measured FROG trace in Figure S3a yields a retrieved pulse duration of ∼10 fs.
In the experiments, the PFP samples are placed behind the OAP and investigated in transmission geometry. The transmitted probe is sent to a grating spectrograph (Acton SP2150i, Princeton Instruments) with an attached line-camera (Octoplus, e2v) operating at 100 kHz, half of the laser repetition rate. Fast mechanical chopping of the pump is achieved by using an optical chopper system (MC2000B, Thorlabs) that uses a custom-made wheel with 500 slots. The pump is therefore chopped at 50 kHz such that the line camera can record spectra with (Son) and without (Soff) presence of the pump, each in pairs of two laser pulses. From each pair of two consecutive spectra we compute the differential transmission
ΔTT(td,ED)=Son(td,ED)−Soff(ED)Soff(ED)
(1)
as a function of the pump–probe delay td and the probe energy ED. For each delay, 5000 consecutive differential spectra are recorded and averaged. A step-size of 3 fs is used, and delays are scanned up to 6 ps for PFP on NaF. For PFP on KCl, the time delays are scanned up to 6 ps when the laser pulses are polarized along the b⃗-axis and up to 3 ps along the a⃗-axis of crystal. To increase the signal-to-noise ratio, multiple of such scans are repeated and averaged afterward.
All experiments are performed at room temperature and under ambient conditions. The half-wave plate is used to tune both pump and probe to align with the desired crystal orientation. Experiments are performed with a pump fluence of 800 μJ/cm2 for the sample on NaF substrate and 730 μJ/cm2 for KCl substrate. The probe is set to 330 μJ/cm2. During experiments, no signs of sample degradation have been observed. A study of the effect of the pump fluence on the pump–probe signal (Figure S4) ensured that all experiments are performed within the regime of χ(3) nonlinearities.

Raman Spectroscopy

Raman spectra of PFP/NaF(100) and PFP/KCl(100) were recorded using a WITec Raman microscope equipped with a UHTS-300 SMFC visible spectrometer with a 300 g/mm grating blazed at 750 nm. The excitation wavelength was 785 nm, and the incident laser was linearly polarized with a power set to 50 mW. The excitation beam was focused on the sample to a spot size of approximately one micron with a microscope objective with numerical aperture (NA) of 0.4 and 20× magnification. To record polarization-dependent Raman spectra, the polarization was varied from 0° to 350° in increments of 10° using a half-wave plate.

Analysis of Pump–Probe Data

To analyze the oscillatory modulation in the differential transmission ΔT/T maps, we isolated the oscillatory part by subtracting the slow varying background dynamics characterized by multiple exponential decays. The resulting residual maps, shown in Figure 2 of the manuscript, were normalized to the maximum ΔT/T signal at delay time of 120 fs. This process was applied to all data sets. Figure S5 illustrates the procedure for PFP/NaF, where the laser is polarized along the b⃗-axis.
Subsequently, we calculated the Fourier transform (FT) of the residuals at each detection energy to obtain the energy-resolved Fourier transform spectra for PFP on NaF and KCl that are shown in Figure 4. The resolution of the FT map, determined by the measurement time, is 6 cm–1 for PFP/NaF along both the b⃗- and c⃗-axis, as well as for the b⃗-axis of PFP/KCl. For the a⃗-axis of PFP/KCl, the resolution is 12 cm–1.

Calculation of IR and Raman Spectra

The ab initio simulations of Raman spectra on PFP molecules in vacuo were carried out in the framework of DFT as implemented in the software Gaussian 16 (67) using the PBE functional (60) and cc-pVTZ basis set. Geometry optimization of the isolated PFP molecule was performed without symmetry constraints and with a threshold for the interatomic forces of 10–8 Hartree/bohr. Vibrational modes were calculated in the harmonic approximation. The intensity of the IR-active modes depends on the derivative of the dipole moment μ with respect to the normal coordinates Qn, according to I ∝ |∑i∂μi∂Qnei|2δ(ω−ωn), while the Raman cross-section along a specific scattered direction follows the derivative of the electronic polarizability tensor χij with respect to the normal coordinates Qn, I ∝ |∑ij∂χij∂QneI,ieS,j|2δ(ω−ωn), with eI,i (eS,i) being the i-th polarization of the incident (scattered) electric field. For more details about this theory, we redirect readers to refs. (68,69) Discrepancies of the order of a few cm–1 between calculated and measured frequencies are expected and do not hamper the comparison between experiment and theory.

Data Availability

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All data supporting the findings are presented in the Letter and Supporting Information in graphic form. Experimental raw data and simulation results will be provided by the authors upon reasonable request.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpclett.4c02711.

  • X-ray diffraction of PFP films on KCl and NaF; polarization-resolved UV/vis absorption spectra of single crystalline PFP islands on KCl and NaF; pulse characterization; fluence study; data analysis (PDF)

  • Transparent Peer Review report available (PDF)

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Author Information

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  • Corresponding Author
    • Christoph Lienau - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Center for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Research Centre for Neurosensory Sciences, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Orcidhttps://orcid.org/0000-0003-3854-5025;  Email: [email protected]
  • Authors
    • Somayeh Souri - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Orcidhttps://orcid.org/0009-0005-7838-5718
    • Daniel Timmer - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Orcidhttps://orcid.org/0000-0001-7541-8047
    • Daniel C. Lünemann - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Orcidhttps://orcid.org/0000-0003-2077-3062
    • Naby Hadilou - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    • Katrin Winte - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    • Antonietta De Sio - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Center for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Orcidhttps://orcid.org/0000-0003-2363-5634
    • Martin Esmann - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Center for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Orcidhttps://orcid.org/0000-0002-2329-9696
    • Franziska Curdt - Institut für Biologie, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    • Michael Winklhofer - Institut für Biologie, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    • Sebastian Anhäuser - Fachbereich Physik, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, Germany
    • Michele Guerrini - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany
    • Ana M. Valencia - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Orcidhttps://orcid.org/0000-0003-0095-3680
    • Caterina Cocchi - Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Center for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany;  Orcidhttps://orcid.org/0000-0002-9243-9461
    • Gregor Witte - Fachbereich Physik, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, Germany;  Orcidhttps://orcid.org/0000-0003-2237-0953
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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The authors would like to acknowledge financial support from Deutsche Forschungsgemeinschaft (SFB 1372 magnetoreception and navigation in vertebrates, project number 395940726, INST 184/163-1, INST 184/164-1, Li 580/16-1, DE 3578/3-1, 223848855-SFB 1083 TP A2 and INST 184/222-1 (Confocal Raman Microscope)). We also acknowledge financial support from the Niedersächsische Ministerium für Wissenschaft und Kultur (DyNano and Wissenschaftsraum ElLiKo within the programme “zukunft.niedersachsen”), the Volkswagen Foundation (SMART). Computational resources were provided by the CARL Cluster at the Carl-von-Ossietzky University, Oldenburg, supported by the DFG and the Niedersächsisches MWK. C. C. acknowledges additional funding from the Federal Ministry of Education and Research (Professorinnenprogramm III) and from the Niedersächsische Ministerium für Wissenschaft und Kultur (Professorinnen für Niedersachsen). We thank L. Gütay for help with the Raman measurements.

References

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This article references 69 other publications.

  1. 1
    Klauk, H. Organic Electronics: Materials, Manufacturing and Applications; Wiley-VCH, 2006.
    Google Scholar
    There is no corresponding record for this reference.
  2. 2
    Brédas, J. L.; Marder, S. R. The WSPC Reference on Organic Electronics: Organic Semiconductors; World Scientific, 2016.
    Google Scholar
    There is no corresponding record for this reference.
  3. 3
    Ostroverkhova, O. Organic Optoelectronic Materials: Mechanisms and Applications. Chem. Rev. 2016, 116 (22), 13279– 13412,  DOI: 10.1021/acs.chemrev.6b00127
    Google Scholar
    3
    Organic Optoelectronic Materials: Mechanisms and Applications
    Ostroverkhova, Oksana
    Chemical Reviews (Washington, DC, United States) (2016), 116 (22), 13279-13412CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. Org. (opto)electronic materials have received considerable attention due to their applications in thin-film-transistors, light-emitting diodes, solar cells, sensors, photorefractive devices, and many others. The technol. promises include low cost of these materials and the possibility of their room-temp. deposition from soln. on large-area and/or flexible substrates. The article reviews the current understanding of the phys. mechanisms that det. the (opto)electronic properties of high-performance org. materials. The focus of the review is on photoinduced processes and on electronic properties important for optoelectronic applications relying on charge carrier photogeneration. Addnl., it highlights the capabilities of various exptl. techniques for characterization of these materials, summarizes top-of-the-line device performance, and outlines recent trends in the further development of the field. The properties of materials based both on small mols. and on conjugated polymers are considered, and their applications in org. solar cells, photodetectors, and photorefractive devices are discussed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xhs1egsLnM&md5=4ab815e1951d3749bf2a5bbd93106a9b
  4. 4
    Rand, B. P.; Cheyns, D.; Vasseur, K.; Giebink, N. C.; Mothy, S.; Yi, Y.; Coropceanu, V.; Beljonne, D.; Cornil, J.; Brédas, J.-L. The Impact of Molecular Orientation on the Photovoltaic Properties of a Phthalocyanine/Fullerene Heterojunction. Adv. Funct. Mater. 2012, 22 (14), 2987– 2995,  DOI: 10.1002/adfm.201200512
    Google Scholar
    4
    The Impact of Molecular Orientation on the Photovoltaic Properties of a Phthalocyanine/Fullerene Heterojunction
    Rand, Barry P.; Cheyns, David; Vasseur, Karolien; Giebink, Noel C.; Mothy, Sebastien; Yi, Yuanping; Coropceanu, Vaeceslav; Beljonne, David; Cornil, Jerome; Bredas, Jean-Luc; Genoe, Jan
    Advanced Functional Materials (2012), 22 (14), 2987-2995CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The anisotropy inherent to many planar org. mols. leads to a high sensitivity of various fundamental processes to the orientation of mols. within films and at heterojunctions. Such processes include absorption, charge and exciton transport, energy levels, and charge transfer, all of which are crit. to org. solar cell operation. Here,an in-depth study of bilayer cells consisting of a donor/acceptor interface between zinc phthalocyanine (ZnPc) and fullerene (C60) is conducted and devices with the typically deposited standing up (edge-on) orientation are compared to those with ZnPc lying flat (face-on). The face-on ZnPc-based device allows for an increase in all solar cell parameters, substantially increasing power conversion efficiency from 1.5% to 2.8%. Spectrally resolved photocurrent measurements reveal a >50% increase in ZnPc signal, from which only 12% is accounted for by the increase in absorption assocd. with the face-on orientation. The increase in internal quantum efficiency is accounted for via an improved charge transfer. The results of this study indicate that proper consideration of the orientation between donor and acceptor needs to be taken to fully optimize the numerous processes required for photovoltaic energy conversion.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xls1elsr4%253D&md5=8bf9b0dffbdcb55f4bf37f16b543b34b
  5. 5
    Karl, N. Charge Carrier Transport in Organic Semiconductors. Synth. Met. 2003, 133–134, 649– 657,  DOI: 10.1016/S0379-6779(02)00398-3
    Google Scholar
    5
    Charge carrier transport in organic semiconductors
    Karl, N.
    Synthetic Metals (2003), 133-134 (), 649-657CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier Science B.V.)
    A review. To understand charge carrier transport in org. semiconductors the magnitude and anisotropy, as well as the temp. and eventual elec. field dependence of the electron and of the hole mobility are fundamental parameters. A no. of tech. applications require high mobilities. A brief review is given on different exptl. methods that can either directly measure charge carrier mobilities, or at least lead to an est. For high purity single crystals, a steep increase of mobilities towards low temp. with the consequence of nonlinear transport and final velocity satn. at elevated elec. fields was found and traced back to temp.-dependent electron and hole masses approaching the free electron mass at low temp. This, and addnl. recent reports in literature on ultrahigh mobilities-with a no. of exciting consequences, such as integer and fractional quantum Hall effect and even supercond. in such materials as anthracene, tetracene, pentacene, and C60-are clear indications of band transport. With rising temp. electron-phonon coupling, and therefore the effective masses, increase and coherent band transport is gradually destroyed; polaron-hopping transport evolves as a parallel channel and dominates at sufficiently high temp. For crystals with orientational disorder of the mols. band transport is precluded.
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  6. 6
    Podzorov, V.; Menard, E.; Borissov, A.; Kiryukhin, V.; Rogers, J. A.; Gershenson, M. E. Intrinsic Charge Transport on the Surface of Organic Semiconductors. Phys. Rev. Lett. 2004, 93 (8), 086602,  DOI: 10.1103/PhysRevLett.93.086602
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    6
    Intrinsic Charge Transport on the Surface of Organic Semiconductors
    Podzorov, V.; Menard, E.; Borissov, A.; Kiryukhin, V.; Rogers, J. A.; Gershenson, M. E.
    Physical Review Letters (2004), 93 (8), 086602/1-086602/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    The air-gap field-effect technique enabled realization of the intrinsic (not limited by static disorder) polaronic transport on the surface of rubrene (C42H28) crystals over a wide temp. range. The signatures of this intrinsic transport are the anisotropy of the carrier mobility, μ, and the growth of μ with cooling. Anisotropy of μ vanishes in the activation regime at low temps., where the transport is dominated by shallow traps. The deep traps, introduced by x-ray radiation, increase the field-effect threshold without affecting μ, an indication that the filled traps do not scatter polarons.
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  7. 7
    Repp, J.; Liljeroth, P.; Meyer, G. Coherent Electron–Nuclear Coupling in Oligothiophene Molecular Wires. Nat. Phys. 2010, 6 (12), 975– 979,  DOI: 10.1038/nphys1802
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    There is no corresponding record for this reference.
  8. 8
    Du, S.; Yoshida, K.; Zhang, Y.; Hamada, I.; Hirakawa, K. Terahertz Dynamics of Electron–Vibron Coupling in Single Molecules with Tunable Electrostatic Potential. Nat. Photonics. 2018, 12 (10), 608– 612,  DOI: 10.1038/s41566-018-0241-1
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    8
    Terahertz dynamics of electron-vibron coupling in single molecules with tunable electrostatic potential
    Du, Shaoqing; Yoshida, Kenji; Zhang, Ya; Hamada, Ikutaro; Hirakawa, Kazuhiko
    Nature Photonics (2018), 12 (10), 608-612CODEN: NPAHBY; ISSN:1749-4885. (Nature Research)
    Clarifying electronic and vibronic properties at the individual mol. level provides key insights for future chem., nanoelectronics and quantum information technologies. However, information obtained by conventional single-mol. transport measurements is based on time-averaged properties. Here, we report on terahertz (THz) spectroscopy of single fullerene mols. by using a single-mol. transistor geometry. From the time-domain THz autocorrelation measurements, we obtained THz spectra assocd. with the THz-induced center-of-mass oscillation of the mols. The obsd. spectra reflect the potential profile experienced by the mol. on the metal surface when the no. of electrons on the mol. fluctuates by one during the single-electron tunnelling process. Such an ultra-high sensitivity to the electronic/vibronic structures of a single mol. on the addn./removal of a single electron has been achieved as a result of using THz spectroscopy in the single-mol. transistor geometry. This scheme provides an opportunity to investigate the ultrafast THz dynamics of subnanometre-scale systems.
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  9. 9
    Kong, F.-F.; Tian, X.-J.; Zhang, Y.; Yu, Y.-J.; Jing, S.-H.; Zhang, Y.; Tian, G.-J.; Luo, Y.; Yang, J.-L.; Dong, Z.-C. Probing Intramolecular Vibronic Coupling Through Vibronic-State Imaging. Nat. Commun. 2021, 12 (1), 1280,  DOI: 10.1038/s41467-021-21571-z
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    9
    Probing intramolecular vibronic coupling through vibronic-state imaging
    Kong, Fan-Fang; Tian, Xiao-Jun; Zhang, Yang; Yu, Yun-Jie; Jing, Shi-Hao; Zhang, Yao; Tian, Guang-Jun; Luo, Yi; Yang, Jin-Long; Dong, Zhen-Chao; Hou, J. G.
    Nature Communications (2021), 12 (1), 1280CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)
    Vibronic coupling is a central issue in mol. spectroscopy. Here we investigate vibronic coupling within a single pentacene mol. in real space by imaging the spatial distribution of single-mol. electroluminescence via highly localized excitation of tunneling electrons in a controlled plasmonic junction. The obsd. two-spot orientation for certain vibronic-state imaging is found to be evidently different from the purely electronic 0-0 transition, rotated by 90°, which reflects the change in the transition dipole orientation from along the mol. short axis to the long axis. Such a change reveals the occurrence of strong vibronic coupling assocd. with a large Herzberg-Teller contribution, going beyond the conventional Franck-Condon picture. The emergence of large vibration-induced transition charges oscillating along the long axis is found to originate from the strong dynamic perturbation of the anti-sym. vibration on those carbon atoms with large transition d. populations during electronic transitions.
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  10. 10
    Breuer, T.; Witte, G. Epitaxial Growth of Perfluoropentacene Films with Predefined Molecular Orientation: A Route for Single-Crystal Optical Studies. Phys. Rev. B 2011, 83 (15), 155428,  DOI: 10.1103/PhysRevB.83.155428
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    There is no corresponding record for this reference.
  11. 11
    Condon, E. A Theory of Intensity Distribution in Band Systems. Phys. Rev. 1926, 28 (6), 1182– 1201,  DOI: 10.1103/PhysRev.28.1182
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    11
    Theory of intensity distribution in band systems
    Condon, Edward
    Physical Review (1926), 28 (), 1182-1201CODEN: PHRVAO; ISSN:0031-899X.
    There is no expanded citation for this reference.
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  12. 12
    Spano, F. C. Excitons in Conjugated Oligomer Aggregates, Films, and Crystals. Annu. Rev. Phys. Chem. 2006, 57, 217– 243,  DOI: 10.1146/annurev.physchem.57.032905.104557
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    12
    Excitons in conjugated oligomer aggregates, films, and crystals
    Spano, Frank C.
    Annual Review of Physical Chemistry (2006), 57 (), 217-243CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews Inc.)
    A review. Recent exptl. and theor. investigations of excitons in conjugated oligomer nanoaggregates, thin films, and crystals are reviewed. The review focuses on the technol. important unsubstituted oligo(phenylene vinylene)s (OPVn) and oligothiophenes (OTn), which exhibit side-by-side herringbone crystal packing. Many of the salient photophys. properties displayed by OPVn and OTn solid phases, including the large Davydov splitting, the rich variety of peaks due to vibronic coupling in both absorption and emission, and the unusual behavior of the emission origin, are accounted for in a model including excitonic coupling between mols., linear exciton-phonon coupling, and disorder.
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  13. 13
    Wykes, M.; Parambil, R.; Beljonne, D.; Gierschner, J. Vibronic Coupling in Molecular Crystals: A Franck-Condon Herzberg-Teller Model of H-Aggregate Fluorescence Based on Quantum Chemical Cluster Calculations. J. Chem. Phys. 2015, 143 (11), 114116,  DOI: 10.1063/1.4930606
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    13
    Vibronic coupling in molecular crystals: A Franck-Condon Herzberg-Teller model of H-aggregate fluorescence based on quantum chemical cluster calculations
    Wykes, M.; Parambil, R.; Beljonne, D.; Gierschner, J.
    Journal of Chemical Physics (2015), 143 (11), 114116/1-114116/12CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    Here, the authors present a general approach to treating vibronic coupling in mol. crystals based on atomistic simulations of large clusters. Such clusters comprise model aggregates treated at the quantum chem. level embedded within a realistic environment treated at the mol. mechanics level. As the authors calc. ground and excited state equil. geometries and vibrational modes of model aggregates, approach is able to capture effects arising from coupling to intermol. degrees of freedom, absent from existing models relying on geometries and normal modes of single mols. Using the geometries and vibrational modes of clusters, the authors are able to simulate the fluorescence spectra of aggregates for which the lowest excited state bears negligible oscillator strength (as is the case, e.g., ideal H-aggregates) by including both Franck-Condon (FC) and Herzberg-Teller (HT) vibronic transitions. The latter terms allow the adiabatic excited state of the cluster to couple with vibrations in a perturbative fashion via derivs. of the transition dipole moment along nuclear coordinates. While vibronic coupling simulations employing FC and HT terms are well established for single-mols., to knowledge this is the first time they are applied to mol. aggregates. Here, the authors apply this approach to the simulation of the low-temp. fluorescence spectrum of para-distyrylbenzene single-crystal H-aggregates and draw comparisons with coarse-grained Frenkel-Holstein approaches previously extensively applied to such systems. (c) 2015 American Institute of Physics.
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  14. 14
    Small, G. J. Herzberg-Teller Vibronic Coupling and Duschinsky Effect. J. Chem. Phys. 1971, 54 (8), 3300,  DOI: 10.1063/1.1675343
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    14
    Herzberg-Teller vibronic coupling and the Duschinsky effect
    Small, Gerald J.
    Journal of Chemical Physics (1971), 54 (8), 3300-6CODEN: JCPSA6; ISSN:0021-9606.
    The assumption that the difference in compn., in terms of symmetry coordinates, between the normal vibrational motions of the ground and 1st excited state (Duschinsky effect) can be neglected in the Herzberg-Teller theory of absorption and fluorescence vibronic intensities is crit. examd. A theory of the Duschinsky effect is described which involves expansion of the potential energy of the fluorescent state in terms of the ground state normal coordinate displacements. Off-diagonal quadratic contributions arise in the expansion whenever there is a coupling between the crude Born-Oppenheimer electronic wavefunctions of the fluorescent and other excited states through 2 or more ground state normal motions of the same symmetry. The importance of the Duschinsky effect depends on the magnitudes of the Herzberg-Teller vibronic matrix elements and the frequency differences between the fundamentals which effect vibronic perturbations. Inclusion of the Duschinsky effect in the Herzberg-Teller theory for 2 or more nontotally symmetric perturbing vibrations introduces a constructive-destructive interference problem, involving the "forbidden" transition moments similar to the one that arises in the theory of Craig and Small on totally symmetric vibrational perturbations. The interferences can lead to a breakdown in mirror symmetry between the absorption and fluorescence spectra. The theory presented for a 2 vibrational model enables the relative signs of the 2 forbidden moments to be detd. by comparison of the relative intensities of 2 vibronic bands in absorption and fluorescence. In the case of naphthalene the forbidden moments assocd. with 509 and 938 cm-b3g modes are antiparallel. Calcns. for phenanthrene suggest that, although the Duschinsky effect should be included in any attempt at accurate vibronic intensity calcns., the constructive-destructive interference effects described by Craig and Small are primarily responsible for the gross deviations from mirror symmetry exptl. obsd. Illustrative calcns. show that the Duschinsky effect should not be neglected in the Herzberg-Teller theory of both fluorescence and absorption vibronic intensities.
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  15. 15
    Kundu, S.; Roy, P. P.; Fleming, G. R.; Makri, N. Franck–Condon and Herzberg–Teller Signatures in Molecular Absorption and Emission Spectra. J. Phys. Chem. B 2022, 126 (15), 2899– 2911,  DOI: 10.1021/acs.jpcb.2c00846
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    There is no corresponding record for this reference.
  16. 16
    Kim, W.; Musser, A. J. Tracking Ultrafast Reactions in Organic Materials Through Vibrational Coherence: Vibronic Coupling Mechanisms in Singlet Fission. Adv. Phys. X. 2021, 6 (1), 1918022,  DOI: 10.1080/23746149.2021.1918022
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    There is no corresponding record for this reference.
  17. 17
    De Sio, A.; Sommer, E.; Nguyen, X. T.; Gross, L.; Popovic, D.; Nebgen, B. T.; Fernandez-Alberti, S.; Pittalis, S.; Rozzi, C. A.; Molinari, E. Intermolecular Conical Intersections in Molecular Aggregates. Nat. Nanotechnol 2021, 16 (1), 63– 68,  DOI: 10.1038/s41565-020-00791-2
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    There is no corresponding record for this reference.
  18. 18
    Singh, S.; Jones, W. J.; Siebrand, W.; Stoicheff, B. P.; Schneider, W. G. Laser Generation of Excitons and Fluorescencence in Anthracene Crystals. J. Chem. Phys. 1965, 42 (1), 330– 342,  DOI: 10.1063/1.1695695
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    There is no corresponding record for this reference.
  19. 19
    Smith, M. B.; Michl, J. Singlet Fission. Chem. Rev. 2010, 110 (11), 6891– 6936,  DOI: 10.1021/cr1002613
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    19
    Singlet Fission
    Smith, Millicent B.; Michl, Josef
    Chemical Reviews (Washington, DC, United States) (2010), 110 (11), 6891-6936CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. A theory of singlet fission is discussed along with its relation to photovoltaics. The literature is reviewed dealing with singlet fission in org. chromophores from the time of initial discovery of singlet fission to the present day.
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  20. 20
    Smith, M. B.; Michl, J. Recent Advances in Singlet Fission. Annu. Rev. Phys. Chem. 2013, 64, 361– 386,  DOI: 10.1146/annurev-physchem-040412-110130
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    20
    Recent advances in singlet fission
    Smith, Millicent B.; Michl, Josef
    Annual Review of Physical Chemistry (2013), 64 (), 361-386CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews Inc.)
    A review. A survey is provided of recent progress in the understanding of singlet fission, a spin-allowed process in which a singlet excited mol. shares its energy with a ground-state neighbor to produce two triplet excited mols. It has been obsd. to occur in single-crystal, polycryst., and amorphous solids, on timescales from 80 fs to 25 ps, producing triplet yields as high as 200%. Photovoltaic devices using the effect have shown external quantum efficiencies in excess of 100%. Almost all the efficient materials are alternant hydrocarbons of the acene series or their simple derivs., and it is argued that a wider structural variety would be desirable. The current state of the development of mol. structure design rules, based on first-principles theor. considerations, is described along with initial examples of implementation.
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  21. 21
    Monahan, N.; Zhu, X. Y. Charge Transfer-Mediated Singlet Fission. Annu. Rev. Phys. Chem. 2015, 66, 601– 618,  DOI: 10.1146/annurev-physchem-040214-121235
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    21
    Charge transfer-mediated singlet fission
    Monahan, N.; Zhu, X.-Y.
    Annual Review of Physical Chemistry (2015), 66 (), 601-618CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews)
    Singlet fission, the splitting of a singlet exciton into two triplet excitons in mol. materials, is interesting not only as a model many-electron problem, but also as a process with potential applications in solar energy conversion. Here we discuss limitations of the conventional four-electron and mol. dimer model in describing singlet fission in cryst. org. semiconductors, such as pentacene and tetracene. We emphasize the need to consider electronic delocalization, which is responsible for the decisive role played by the Mott-Wannier exciton, also called the charge transfer (CT) exciton, in mediating singlet fission. At the strong electronic coupling limit, the initial excitation creates a quantum superposition of singlet, CT, and triplet-pair states, and we present exptl. evidence for this interpretation. We also discuss the most recent attempts at translating this mechanistic understanding into design principles for CT state-mediated intramol. singlet fission in oligomers and polymers.
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  22. 22
    Walker, B. J.; Musser, A. J.; Beljonne, D.; Friend, R. H. Singlet Exciton Fission in Solution. Nat. Chem. 2013, 5 (12), 1019– 1024,  DOI: 10.1038/nchem.1801
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    22
    Singlet exciton fission in solution
    Walker, Brian J.; Musser, Andrew J.; Beljonne, David; Friend, Richard H.
    Nature Chemistry (2013), 5 (12), 1019-1024CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
    Singlet exciton fission, the spin-conserving process that produces two triplet excited states from one photoexcited singlet state, is a means to circumvent the Shockley-Queisser limit in single-junction solar cells. Although the process through which singlet fission occurs is not well characterized, some local order is thought to be necessary for intermol. coupling. Here, we report a triplet yield of 200% and triplet formation rates approaching the diffusion limit in solns. of bis(triisopropylsilylethynyl (TIPS)) pentacene. We observe a transient bound excimer intermediate, formed by the collision of one photoexcited and one ground-state TIPS-pentacene mol. The intermediate breaks up when the two triplets sep. to each TIPS-pentacene mol. This efficient system is a model for future singlet-fission materials and for disordered device components that produce cascades of excited states from sunlight.
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  23. 23
    Wilson, M. W.; Rao, A.; Ehrler, B.; Friend, R. H. Singlet Exciton Fission in Polycrystalline Pentacene: From Photophysics Toward Devices. Acc. Chem. Res. 2013, 46 (6), 1330– 1338,  DOI: 10.1021/ar300345h
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    23
    Singlet Exciton Fission in Polycrystalline Pentacene: From Photophysics toward Devices
    Wilson, Mark W. B.; Rao, Akshay; Ehrler, Bruno; Friend, Richard H.
    Accounts of Chemical Research (2013), 46 (6), 1330-1338CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
    A review. Singlet exciton fission is the process in conjugated org. mols. by which a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers 1st reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These studies used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest was recently re-kindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating addnl. photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chem., and small-mol. device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycryst. thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, the authors review the results of recent transient absorption and device-based studies of polycryst. pentacene. The authors address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins conclusion that singlet fission in pentacene is extraordinarily rapid (∼80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, demonstration that triplet excitons generated via singlet fission in pentacene can be dissocd. at an interface with a suitable electron acceptor, such as fullerenes and IR-absorbing inorg. semiconducting quantum dots are discussed. The authors highlight recent reports of a pentacene/PbSe hybrid solar cell with a power conversion efficiency of 4.7% and of a pentacene/PbSe/amorphous Si photovoltaic device. Although substantive challenges remain, both to better understanding of the mechanism of singlet exciton fission and to optimize device performance, this realization of a solar cell where photocurrent is simultaneously contributed from a blue-absorbing fission-capable material and an IR-absorbing conventional cell is an important step towards a dual-bandgap, single-junction, fission-enhanced photovoltaic device, which could 1 day surpass the Shockley-Queisser limit.
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  24. 24
    Musser, A. J.; Liebel, M.; Schnedermann, C.; Wende, T.; Kehoe, T. B.; Rao, A.; Kukura, P. Evidence for Conical Intersection Dynamics Mediating Ultrafast Singlet Exciton Fission. Nat. Phys. 2015, 11 (4), 352– 357,  DOI: 10.1038/nphys3241
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    24
    Evidence for conical intersection dynamics mediating ultrafast singlet exciton fission
    Musser, Andrew J.; Liebel, Matz; Schnedermann, Christoph; Wende, Torsten; Kehoe, Tom B.; Rao, Akshay; Kukura, Philipp
    Nature Physics (2015), 11 (4), 352-357CODEN: NPAHAX; ISSN:1745-2473. (Nature Publishing Group)
    Singlet exciton fission is the process in org. semiconductors through which a spin-singlet exciton converts into a pair of spin-triplet excitons residing on different chromophores, entangled in an overall spin-zero state. For some systems, singlet fission has been shown to occur on the 100 fs timescale and with a 200% quantum yield, but the mechanism of this process remains uncertain. Here we study a model singlet fission system, TIPS-pentacene, using ultrafast vibronic spectroscopy. We observe that vibrational coherence in the initially photogenerated singlet state is transferred to the triplet state and show that this behavior is effectively identical to ultrafast internal conversion for polyenes in soln. This similarity in vibronic dynamics suggests that both multi-mol. singlet fission and single-mol. internal conversion are mediated by the same underlying relaxation processes, based on strong coupling between nuclear and electronic degrees of freedom. In its most efficient form this leads to a conical intersection between the coupled electronic states.
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  25. 25
    Chan, W.-L.; Ligges, M.; Jailaubekov, A.; Kaake, L.; Miaja-Avila, L.; Zhu, X.-Y. Observing the Multiexciton State in Singlet Fission and Ensuing Ultrafast Multielectron Transfer. Science 2011, 334 (6062), 1541– 1545,  DOI: 10.1126/science.1213986
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    25
    Observing the Multiexciton State in Singlet Fission and Ensuing Ultrafast Multielectron Transfer
    Chan, Wai-Lun; Ligges, Manuel; Jailaubekov, Askat; Kaake, Loren; Miaja-Avila, Luis; Zhu, X.-Y.
    Science (Washington, DC, United States) (2011), 334 (6062), 1541-1545CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    Two for One Conventional solar cells create a charge carrier each time a photon of light at or above a certain energy threshold is absorbed. Any energy embedded in short-wavelength photons that exceeds the threshold is largely wasted. Semonin et al. (p. ) now demonstrate a nanoparticulate lead selenide solar cell that channels a fraction of the excess energy into current. Chan et al. (p. ) explored the fundamental dynamics of multiple carrier generation in an org. (rather than inorg.) absorber and characterized a short-lived state that bridges the high-energy single carrier state and two discrete lower-energy carrier states. Multiple exciton generation (MEG) refers to the creation of two or more electron-hole pairs from the absorption of one photon. Although MEG holds great promise, it proved challenging to implement, and questions remain about the underlying photo-phys. dynamics in nanocryst. as well as mol. media. Using the model system of pentacene/fullerene bilayers and femtosecond nonlinear spectroscopies, the authors directly obsd. the multiexciton (ME) state ensuing from singlet fission (a mol. manifestation of MEG) in pentacene. Probably the state exists in coherent superposition with the singlet populated by optical excitation. Also multiple electron transfer from the ME state to the fullerene occurs on a subpicosecond time scale, which is one order of magnitude faster than that from the triplet exciton state.
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  26. 26
    Duan, H.-G.; Jha, A.; Li, X.; Tiwari, V.; Ye, H.; Nayak, P. K.; Zhu, X.-L.; Li, Z.; Martinez, T. J.; Thorwart, M. Intermolecular Vibrations Mediate Ultrafast Singlet Fission. Sci. Adv. 2020, 6 (38), eabb0052  DOI: 10.1126/sciadv.abb0052
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    There is no corresponding record for this reference.
  27. 27
    Seiler, H.; Krynski, M.; Zahn, D.; Hammer, S.; Windsor, Y. W.; Vasileiadis, T.; Pflaum, J.; Ernstorfer, R.; Rossi, M.; Schwoerer, H. Nuclear Dynamics of Singlet Exciton Fission in Pentacene Single Crystals. Sci. Adv. 2021, 7 (26), eabg0869  DOI: 10.1126/sciadv.abg0869
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    There is no corresponding record for this reference.
  28. 28
    Neef, A.; Beaulieu, S.; Hammer, S.; Dong, S.; Maklar, J.; Pincelli, T.; Xian, R. P.; Wolf, M.; Rettig, L.; Pflaum, J. Orbital-Resolved Observation of Singlet Fission. Nature 2023, 616 (7956), 275– 279,  DOI: 10.1038/s41586-023-05814-1
    Google Scholar
    There is no corresponding record for this reference.
  29. 29
    Kim, J.; Bain, D. C.; Ding, V.; Majumder, K.; Windemuller, D.; Feng, J.; Wu, J.; Patil, S.; Anthony, J.; Kim, W. Coherent photoexcitation of entangled triplet pair states. Nat. Chem. 2024, 16, 1680– 1686,  DOI: 10.1038/s41557-024-01556-3
    Google Scholar
    There is no corresponding record for this reference.
  30. 30
    Breuer, T.; Celik, M. A.; Jakob, P.; Tonner, R.; Witte, G. Vibrational Davydov Splittings and Collective Mode Polarizations in Oriented Organic Semiconductor Crystals. J. Phys. Chem. C 2012, 116 (27), 14491– 14503,  DOI: 10.1021/jp304080g
    Google Scholar
    30
    Vibrational Davydov Splittings and Collective Mode Polarizations in Oriented Organic Semiconductor Crystals
    Breuer, Tobias; Celik, Mehmet A.; Jakob, Peter; Tonner, Ralf; Witte, Gregor
    Journal of Physical Chemistry C (2012), 116 (27), 14491-14503CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Vibrational properties of highly ordered cryst. perfluoropentacene (PFP) films epitaxially grown on KCl(100) and NaF(100) substrates were studied by transmission IR spectroscopy and d. functional theory. The different mol. orientations adopted by PFP on both substrates (standing vs. lying) and their epitaxial ordering enable precise polarization-resolved measurements along individual crystallog. directions and thus allow an unambiguous exptl. detn. of the polarization of the IR modes. Computations of the vibrational spectra beyond the single-mol. approxn. were employed at the periodic dispersion-cor. d. functional level (PBE-D2PBC) and compared with nonperiodic calcns. (PBE-D2/def2-TZVPP). Thereby, a detailed mode assignment based on vibrational energies and polarization information was attained. A microscopic explanation for the exptl. obsd. Davydov splitting of some modes and the IR inactivity of others was derived based on the mutual coupling of the dynamical dipole moments of the 2 mols. within the unit cell. Exptl. obsd. modes not covered by theor. anal. were identified as combination bands of IR-active modes coupled to totally sym. modes of similar displacement patterns. These findings have important implications for future studies on structure and charge transport in org. semiconductors and the validation of theor. approaches for the modeling of vibrational spectra.
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  31. 31
    Kolata, K.; Breuer, T.; Witte, G.; Chatterjee, S. Molecular Packing Determines Singlet Exciton Fission in Organic Semiconductors. ACS Nano 2014, 8 (7), 7377– 7383,  DOI: 10.1021/nn502544d
    Google Scholar
    31
    Molecular Packing Determines Singlet Exciton Fission in Organic Semiconductors
    Kolata, Kolja; Breuer, Tobias; Witte, Gregor; Chatterjee, Sangam
    ACS Nano (2014), 8 (7), 7377-7383CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
    Carrier multiplication by singlet exciton fission enhances photovoltaic conversion efficiencies in org. solids. This decay of 1 singlet exciton into 2 triplet states allows the extn. of ≤2 electrons per harvested photon and promises to overcome the Shockley-Queisser limit. The microscopic mechanism of singlet exciton fission, esp. the relation between mol. packing and electronic response, remains unclear, which therefore hampers the systematic improvement of org. photovoltaic devices. For the model system perfluoropentacene, exptl. singlet exciton fission is greatly enhanced for a slip-stacked mol. arrangement by addressing different crystal axes featuring different packing schemes. This reveals that the fission process strongly depends on the intermol. coupling: slip-stacking favors delocalization of excitations and allows for efficient exciton fission, while face-to-edge mol. orientations commonly found in the prevailing herringbone mol. stacking patterns even suppress it. The controversially debated role of excimer states as intermediary rather than competitive or precursory is clarified. The findings serve as a guideline for the design of next-generation mol. materials for application in future org. light-harvesting devices exploiting singlet exciton fission.
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  32. 32
    Fujii, K.; Himcinschi, C.; Toader, M.; Kera, S.; Zahn, D.; Ueno, N. Vibrational Properties of Perfluoropentacene Thin Film. J. Electron Spectrosc. Relat. Phenom. 2009, 174 (1–3), 65– 69,  DOI: 10.1016/j.elspec.2009.01.002
    Google Scholar
    There is no corresponding record for this reference.
  33. 33
    Salzmann, I.; Moser, A.; Oehzelt, M.; Breuer, T.; Feng, X. L.; Juang, Z. Y.; Nabok, D.; Della Valle, R. G.; Duhm, S.; Heimel, G. Epitaxial Growth of π-Stacked Perfluoropentacene on Graphene-Coated Quartz. ACS Nano 2012, 6 (12), 10874– 10883,  DOI: 10.1021/nn3042607
    Google Scholar
    33
    Epitaxial Growth of π-Stacked Perfluoropentacene on Graphene-Coated Quartz
    Salzmann, Ingo; Moser, Armin; Oehzelt, Martin; Breuer, Tobias; Feng, Xinliang; Juang, Zhen-Yu; Nabok, Dmitrii; Della Valle, Raffaele G.; Duhm, Steffen; Heimel, Georg; Brillante, Aldo; Venuti, Elisabetta; Bilotti, Ivano; Christodoulou, Christos; Frisch, Johannes; Puschnig, Peter; Draxl, Claudia; Witte, Gregor; Muellen, Klaus; Koch, Norbert
    ACS Nano (2012), 6 (12), 10874-10883CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
    Chem.-vapor-deposited large-area graphene is employed as the coating of transparent substrates for the growth of the prototypical org. n-type semiconductor perfluoropentacene (PFP). The graphene coating is found to cause face-on growth of PFP in a yet unknown substrate-mediated polymorph, which is solved by combining grazing-incidence X-ray diffraction with theor. structure modeling. In contrast to the otherwise common herringbone arrangement of PFP in single crystals and "standing" films, the authors report a π-stacked arrangement of coplanar mols. in "flat-lying" films, which exhibit an exceedingly low π-stacking distance of only 3.07 Å, giving rise to significant electronic band dispersion along the π-stacking direction, as evidenced by UPS. The study underlines the high potential of graphene for use as a transparent electrode in (opto-)electronic applications, where optimized vertical transport through flat-lying conjugated org. mols. is desired.
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  34. 34
    Zeiser, C.; Moretti, L.; Geiger, T.; Kalix, L.; Valencia, A. M.; Maiuri, M.; Cocchi, C.; Bettinger, H. F.; Cerullo, G.; Broch, K. Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene. J. Phys. Chem. Lett. 2021, 12 (31), 7453– 7458,  DOI: 10.1021/acs.jpclett.1c01805
    Google Scholar
    34
    Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene
    Zeiser, Clemens; Moretti, Luca; Geiger, Thomas; Kalix, Lukas; Valencia, Ana M.; Maiuri, Margherita; Cocchi, Caterina; Bettinger, Holger F.; Cerullo, Giulio; Broch, Katharina
    Journal of Physical Chemistry Letters (2021), 12 (31), 7453-7458CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Singlet fission (SF), the photophys. process in which 1 singlet exciton is transformed into 2 triplets, depends inter alia on the coupling of electronic states. Here, the authors use fluorination and the resulting changes in partial charge distribution across the chromophore backbone as a particularly powerful tool to control this parameter in pentacene. The introduction of a permanent dipole moment leads to an enhanced coupling of Frenkel exciton and charge transfer states and to an increased SF rate which the authors probed using ultrafast transient absorption spectroscopy. These findings are contrasted with H-aggregate formation and a significantly reduced triplet-pair state lifetime in a fluorinated pentacene for which the different partial charge distribution leads to a negligible dipole moment.
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  35. 35
    Sakamoto, Y.; Suzuki, T.; Kobayashi, M.; Gao, Y.; Fukai, Y.; Inoue, Y.; Sato, F.; Tokito, S. Perfluoropentacene: High-Performance P–N Junctions and Complementary Circuits with Pentacene. JACS. 2004, 126 (26), 8138– 8140,  DOI: 10.1021/ja0476258
    Google Scholar
    35
    Perfluoropentacene: High-Performance p-n Junctions and Complementary Circuits with Pentacene
    Sakamoto, Youichi; Suzuki, Toshiyasu; Kobayashi, Masafumi; Gao, Yuan; Fukai, Yasushi; Inoue, Youji; Sato, Fumio; Tokito, Shizuo
    Journal of the American Chemical Society (2004), 126 (26), 8138-8140CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The authors report the synthesis and characterization of perfluoropentacene as an n-type semiconductor for org. field-effect transistors (OFETs). Perfluoropentacene is a planar and cryst. material that adopts a herringbone structure as obsd. for pentacene. OFETs with perfluoropentacene were constructed using top-contact geometry, and an electron mobility of 0.11 cm2 V-1 s-1 was obsd. Bipolar OFETs with perfluoropentacene and pentacene function at both neg. and pos. gate voltages. The improved p-n junctions are probably due to the similar d-spacings of both acenes. Complementary inverter circuits were fabricated, and the transfer characteristics exhibit a sharp inversion of the output signal with a high-voltage gain.
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  36. 36
    Timmer, D.; Gittinger, M.; Quenzel, T.; Cadore, A. R.; Rosa, B. L. T.; Li, W. S.; Soavi, G.; Lünemann, D. C.; Stephan, S.; Silies, M. Ultrafast Coherent Exciton Couplings and Many-Body Interactions in Monolayer WS. Nano Lett. 2024, 24, 8117– 8125,  DOI: 10.1021/acs.nanolett.4c01991
    Google Scholar
    There is no corresponding record for this reference.
  37. 37
    Timmer, D.; Lünemann, D. C.; Riese, S.; Sio, A. D.; Lienau, C. Full Visible Range Two-Dimensional Electronic Spectroscopy with High Time Resolution. Opt. Express 2024, 32 (1), 835– 847,  DOI: 10.1364/OE.511906
    Google Scholar
    There is no corresponding record for this reference.
  38. 38
    Timmer, D.; Gittinger, M.; Quenzel, T.; Stephan, S.; Zhang, Y.; Schumacher, M. F.; Lützen, A.; Silies, M.; Tretiak, S.; Zhong, J.-H. Plasmon Mediated Coherent Population Oscillations in Molecular Aggregates. Nat. Commun. 2023, 14 (1), 8035,  DOI: 10.1038/s41467-023-43578-4
    Google Scholar
    There is no corresponding record for this reference.
  39. 39
    Quenzel, T.; Timmer, D.; Gittinger, M.; Zablocki, J.; Zheng, F. L.; Schiek, M.; Lutzen, A.; Frauenheim, T.; Tretiak, S.; Silies, M. Plasmon-Enhanced Exciton Delocalization in Squaraine-Type Molecular Aggregates. ACS Nano 2022, 16 (3), 4693– 4704,  DOI: 10.1021/acsnano.1c11398
    Google Scholar
    39
    Plasmon-Enhanced Exciton Delocalization in Squaraine-Type Molecular Aggregates
    Quenzel, Thomas; Timmer, Daniel; Gittinger, Moritz; Zablocki, Jennifer; Zheng, Fulu; Schiek, Manuela; Luetzen, Arne; Frauenheim, Thomas; Tretiak, Sergei; Silies, Martin; Zhong, Jin-Hui; De Sio, Antonietta; Lienau, Christoph
    ACS Nano (2022), 16 (3), 4693-4704CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
    Enlarging exciton coherence lengths in mol. aggregates is crit. for enhancing the collective optical and transport properties of mol. thin film nanostructures or devices. We demonstrate that the exciton coherence length of squaraine aggregates can be increased from 10 to 24 mol. units at room temp. when prepg. the aggregated thin film on a metallic rather than a dielec. substrate. Two-dimensional electronic spectroscopy measurements reveal a much lower degree of inhomogeneous line broadening for aggregates on a gold film, pointing to a reduced disorder. The result is corroborated by simulations based on a Frenkel exciton model including exciton-plasmon coupling effects. The simulation shows that localized, energetically nearly resonant excitons on spatially well sepd. segments can be radiatively coupled via delocalized surface plasmon polariton modes at a planar mol.-gold interface. Such plasmon-enhanced delocalization of the exciton wave function is of high importance for improving the coherent transport properties of mol. aggregates on the nanoscale. Addnl., it may help tailor the collective optical response of org. materials for quantum optical applications.
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  40. 40
    Timmer, D.; Zheng, F.; Gittinger, M.; Quenzel, T.; Lünemann, D. C.; Winte, K.; Zhang, Y.; Madjet, M. E.; Zablocki, J.; Lützen, A. Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes. JACS. 2022, 144 (41), 19150– 19162,  DOI: 10.1021/jacs.2c08682
    Google Scholar
    There is no corresponding record for this reference.
  41. 41
    Breuer, T. Preparation and Characterization of Thin Films of Organic Semiconductors and their Heterostructures. Ph.D. Thesis, University of Marburg, Marburg, Germany, 2013.
    Google Scholar
    There is no corresponding record for this reference.
  42. 42
    Cocchi, C.; Breuer, T.; Witte, G.; Draxl, C. Polarized Absorbance and Davydov Splitting in Bulk and Thin-Film Pentacene Polymorphs. Phys. Chem. Chem. Phys. 2018, 20 (47), 29724– 29736,  DOI: 10.1039/C8CP06384B
    Google Scholar
    42
    Polarized absorbance and Davydov splitting in bulk and thin-film pentacene polymorphs
    Cocchi, Caterina; Breuer, Tobias; Witte, Gregor; Draxl, Claudia
    Physical Chemistry Chemical Physics (2018), 20 (47), 29724-29736CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Pentacene is one of the most studied org. materials and in particular its optical properties have been the subject of intense research during the last two decades. In spite of such a widespread interest and of the extensive knowledge achieved so far, a no. of issues are still debated. One of the most relevant questions concerns the role of polymorphism and how it affects the lowest-energy exciton, which appears in the visible region and is subject to a sizable Davydov splitting. We address this problem in a combined theor. and exptl. work, where the optical absorption properties of three pentacene polymorphs are investigated within the whole energy range of visible light. Optical spectra computed from first principles in the framework of many-body perturbation theory are directly compared with the polarization-resolved absorbance, measured for three different pentacene phases (the two bulk polymorphs and the thin-film phase). In this way, we unambiguously identify the two Davydov components of the first exciton and the optical fingerprints of each considered phase. With very good agreement between theory and expt., we show that all polymorphs exhibit common features at the absorption onset, while phase-dependent characteristics appear only above 2 eV. We discuss the character of the lowest-lying singlet and triplet excitons, including dark ones, highlighting the contributions from the electronic bands and the role of the electron-hole interaction and of the local-field effects.
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  43. 43
    Kumar, A. T. N.; Rosca, F.; Widom, A.; Champion, P. M. Investigations of Amplitude and Phase Excitation Profiles in Femtosecond Coherence Spectroscopy. J. Chem. Phys. 2001, 114 (2), 701– 724,  DOI: 10.1063/1.1329640
    Google Scholar
    43
    Investigations of amplitude and phase excitation profiles in femtosecond coherence spectroscopy
    Kumar, Anand T. N.; Rosca, Florin; Widom, Allan; Champion, Paul M.
    Journal of Chemical Physics (2001), 114 (2), 701-724CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    We present an effective linear response approach to pump-probe femtosecond coherence spectroscopy in the well-sepd. pulse limit. The treatment presented here is based on a displaced and squeezed state representation for the nonstationary states induced by an ultrashort pump laser pulse or a chem. reaction. The subsequent response of the system to a delayed probe pulse is modeled using closed form nonstationary linear response functions, valid for a multimode vibronically coupled system at arbitrary temp. When pump-probe signals are simulated using the linear response functions, with the mean nuclear positions and momenta obtained from a rigorous moment anal. of the pump induced (doorway) state, the signals are found to be in excellent agreement with the conventional third-order response approach. The key advantages offered by the moment anal.-based linear response approach include a clear phys. interpretation of the amplitude and phase of oscillatory pump-probe signals, a dramatic improvement in computation times, a direct connection between pump-probe signals and equil. absorption and dispersion lineshapes, and the ability to incorporate coherence assocd. with rapid nonradiative surface crossing. We demonstrate these aspects using numerical simulations, and also apply the present approach to the interpretation of exptl. amplitude and phase measurements on reactive and nonreactive samples of the heme protein myoglobin. The role played by inhomogeneous broadening in the obsd. amplitude and phase profiles is discussed in detail. We also investigate overtone signals in the context of reaction driven coherent motion.
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  44. 44
    Nguyen, X. T.; Winte, K.; Timmer, D.; Rakita, Y.; Ceratti, D. R.; Aharon, S.; Ramzan, M. S.; Cocchi, C.; Lorke, M.; Jahnke, F. Phonon-Driven Intra-Exciton Rabi Oscillations in CsPbBr3 Halide Perovskites. Nat. Commun. 2023, 14 (1), 1047,  DOI: 10.1038/s41467-023-36654-2
    Google Scholar
    44
    Phonon-driven intra-exciton Rabi oscillations in CsPbBr3 halide perovskites
    Nguyen, Xuan Trung; Winte, Katrin; Timmer, Daniel; Rakita, Yevgeny; Ceratti, Davide Raffaele; Aharon, Sigalit; Ramzan, Muhammad Sufyan; Cocchi, Caterina; Lorke, Michael; Jahnke, Frank; Cahen, David; Lienau, Christoph; De Sio, Antonietta
    Nature Communications (2023), 14 (1), 1047CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)
    Coupling electromagnetic radiation with matter, e.g., by resonant light fields in external optical cavities, is highly promising for tailoring the optoelectronic properties of functional materials on the nanoscale. Here, we demonstrate that even internal fields induced by coherent lattice motions can be used to control the transient excitonic optical response in CsPbBr3 halide perovskite crystals. Upon resonant photoexcitation, two-dimensional electronic spectroscopy reveals an excitonic peak structure oscillating persistently with a 100-fs period for up to ≈2 ps which does not match the frequency of any phonon modes of the crystals. Only at later times, beyond 2 ps, two low-frequency phonons of the lead-bromide lattice dominate the dynamics. We rationalize these findings by an unusual exciton-phonon coupling inducing off-resonant 100-fs Rabi oscillations between 1s and 2p excitons driven by the low-frequency phonons. As such, prevailing models for the electron-phonon coupling in halide perovskites are insufficient to explain these results. We propose the coupling of characteristic low-frequency phonon fields to intra-excitonic transitions in halide perovskites as the key to control the anharmonic response of these materials in order to establish new routes for enhancing their optoelectronic properties.
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  45. 45
    Polli, D.; Antognazza, M. R.; Brida, D.; Lanzani, G.; Cerullo, G.; De Silvestri, S. Broadband Pump-Probe Spectroscopy with Sub-10-fs Resolution for Probing Ultrafast Internal Conversion and Coherent Phonons in Carotenoids. Chem. Phys. 2008, 350 (1–3), 45– 55,  DOI: 10.1016/j.chemphys.2007.12.021
    Google Scholar
    There is no corresponding record for this reference.
  46. 46
    Andrzejak, M.; Mazur, G.; Musser, A. J.; Petelenz, P.; Skóra, T. Properties of Coherent Vibrational Wavepackets Critically Depend on the Method of Their Generation. J. Phys. Chem. C 2024, 128 (24), 9837– 9846,  DOI: 10.1021/acs.jpcc.4c01485
    Google Scholar
    There is no corresponding record for this reference.
  47. 47
    Albrecht, A. C. Theory of Raman Intensities. J. Chem. Phys. 1961, 34 (5), 1476– 1484,  DOI: 10.1063/1.1701032
    Google Scholar
    There is no corresponding record for this reference.
  48. 48
    Ruhman, S.; Joly, A. G.; Nelson, K. A. Coherent Molecular Vibrational Motion Observed in the Time Domain Through Impulsive Stimulated Raman-Scattering. IEEE J. Quantum Electron. 1988, 24 (2), 460– 469,  DOI: 10.1109/3.146
    Google Scholar
    There is no corresponding record for this reference.
  49. 49
    Banin, U.; Bartana, A.; Ruhman, S.; Kosloff, R. Impulsive Excitation of Coherent Vibrational Motion Ground Surface Dynamics Induced by Intense Short Pulses. J. Chem. Phys. 1994, 101 (10), 8461– 8481,  DOI: 10.1063/1.468108
    Google Scholar
    49
    Impulsive excitation of coherent vibrational motion ground surface dynamics induced by intense short pulses
    Banin, Uri; Bartana, Allon; Ruhman, Sanford; Kosloff, Ronnie
    Journal of Chemical Physics (1994), 101 (10), 8461-81CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    A framework for understanding impulsively photoinduced vibrational coherent motion on the ground electronic surface is presented. In particular strong resonant excitation to a directly dissociative electronic surface is considered. Three distinct approaches are employed. A two surface Fourier wavepacket method explicitly including the field explores this process in isolated mols. A coordinate dependent two-level system is employed to develop a novel anal. approx. to the photoinduced quantum dynamics. The negligible computational requirements make it a powerful interactive tool for reconstructing the impulsive photoexcitation stage. Its anal. nature provides closed from expressions for the photoinduced changes in the material. Finally the full simulation of the process including the solvent effects is carried out by a numerical propagation of the d. operator. In all three techniques the excitation field is treated to all orders, allowing an anal. of current expts. using strong fields, resulting in substantial photoconversion. The emerging picture is that the impulsive excitation carves a coherent dynamic "hole" out of the ground surface d. A rigorous definition of the dynamic "hole" is constructed and used to define a measure of its coherence. In particular all photoinduced time dependence in the system can be directly related to the dynamic "hole". All three techniques are used to simulate the pump probe expt. on the sym. stretch mode of I3-3, including electronic and vibrational dephasing.
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  50. 50
    Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P. Principles and Applications of Broadband Impulsive Vibrational Spectroscopy. J. Phys. Chem. A 2015, 119, 9506,  DOI: 10.1021/acs.jpca.5b05948
    Google Scholar
    50
    Principles and Applications of Broadband Impulsive Vibrational Spectroscopy
    Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P.
    Journal of Physical Chemistry A (2015), 119 (36), 9506-9517CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    An exptl. setup is presented for recording vibrational coherences and Raman spectra of mols. in their ground and excited electronic states at 50-3000 cm-1 using broadband impulsive vibrational spectroscopy. The approach relies on the combination of a <10 fs excitation pulse with an uncompressed white light continuum probe, which drastically reduces exptl. complexity compared to frequency domain based techniques. The parameters detg. vibrational coherence amplitudes, outline how to optimize the exptl. setup including approaches aimed at conclusively assigning vibrational coherences to specific electronic states, and provide a clear comparison with existing techniques are discussed. To demonstrate the applicability of the spectroscopic approach, several examples reveal the evolution of vibrational coherence in rhodopsin and β-carotene.
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  51. 51
    Rather, S. R.; Fu, B.; Kudisch, B.; Scholes, G. D. Interplay of Vibrational Wavepackets during an Ultrafast Electron Transfer Reaction. Nat. Chem. 2021, 13 (1), 70– 76,  DOI: 10.1038/s41557-020-00607-9
    Google Scholar
    There is no corresponding record for this reference.
  52. 52
    Liebel, M.; Schnedermann, C.; Kukura, P. Vibrationally Coherent Crossing and Coupling of Electronic States during Internal Conversion in β-Carotene. Phys. Rev. Lett. 2014, 112 (19), 198302,  DOI: 10.1103/PhysRevLett.112.198302
    Google Scholar
    52
    Vibrationally coherent crossing and coupling of electronic states during internal conversion in β-carotene
    Liebel, M.; Schnedermann, C.; Kukura, P.
    Physical Review Letters (2014), 112 (19), 198302/1-198302/5, 5 pp.CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    Coupling of nuclear and electronic degrees of freedom mediates energy flow in mols. after optical excitation. The assocd. coherent dynamics in polyat. systems, however, remain exptl. unexplored. Here, we combined transient absorption spectroscopy with electronic population control to reveal nuclear wave packet dynamics during the S2 → S1 internal conversion in β-carotene. We show that passage through a conical intersection is vibrationally coherent and thereby provides direct feedback on the role of different vibrational coordinates in the breakdown of the Born-Oppenheimer approxn.
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  53. 53
    Falke, S. M.; Rozzi, C. A.; Brida, D.; Maiuri, M.; Amato, M.; Sommer, E.; De Sio, A.; Rubio, A.; Cerullo, G.; Molinari, E. Coherent Ultrafast Charge Transfer in an Organic Photovoltaic Blend. Science 2014, 344 (6187), 1001– 1005,  DOI: 10.1126/science.1249771
    Google Scholar
    53
    Coherent ultrafast charge transfer in an organic photovoltaic blend
    Falke, Sarah Maria; Rozzi, Carlo Andrea; Brida, Daniele; Maiuri, Margherita; Amato, Michele; Sommer, Ephraim; De Sio, Antonietta; Rubio, Angel; Cerullo, Giulio; Molinari, Elisa; Lienau, Christoph
    Science (Washington, DC, United States) (2014), 344 (6187), 1001-1005CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    Blends of conjugated polymers and fullerene derivs. are prototype systems for org. photovoltaic devices. The primary charge-generation mechanism involves a light-induced ultrafast electron transfer from the light-absorbing and electron-donating polymer to the fullerene electron acceptor. Here, the authors elucidate the initial quantum dynamics of this process. Exptl., the authors obsd. coherent vibrational motion of the fullerene moiety after impulsive optical excitation of the polymer donor. Comparison with 1st-principle theor. simulations evidences coherent electron transfer between donor and acceptor and oscillations of the transferred charge with a 25-fs period matching that of the obsd. vibrational modes. The authors' results show that coherent vibronic coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer in a noncovalently bound ref. system.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXosFSmur0%253D&md5=07e4c1b7dbaf8e4bf8d63a4d190a98e7
  54. 54
    Orlandi, G.; Siebrand, W. Theory of Vibronic Intensity Borrowing - Comparison of Herzberg-Teller and Born-Oppenheimer Coupling. J. Chem. Phys. 1973, 58 (10), 4513– 4523,  DOI: 10.1063/1.1679014
    Google Scholar
    There is no corresponding record for this reference.
  55. 55
    Avila Ferrer, F. J.; Barone, V.; Cappelli, C.; Santoro, F. Duschinsky, Herzberg-Teller, and Multiple Electronic Resonance Interferential Effects in Resonance Raman Spectra and Excitation Profiles. The Case of Pyrene. J. Chem. Theory. Comput. 2013, 9 (8), 3597– 3611,  DOI: 10.1021/ct400197y
    Google Scholar
    55
    Duschinsky, Herzberg-Teller, and Multiple Electronic Resonance Interferential Effects in Resonance Raman Spectra and Excitation Profiles. The Case of Pyrene
    Avila Ferrer, Francisco J.; Barone, Vincenzo; Cappelli, Chiara; Santoro, Fabrizio
    Journal of Chemical Theory and Computation (2013), 9 (8), 3597-3611CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)
    A recently developed time-independent approach for the calcn. of vibrational resonance Raman (vRR) spectra is able to describe Duschinsky and Herzberg-Teller (HT) effects acting on a single resonant state, together with interferential contributions arising from multiple electronic resonances, allowing one to study in detail how their interplay dets. both the vRR spectra at selected wavelengths and the Raman excitation profiles. The authors apply this methodol. to the study of the spectra of pyrene in MeCN, an ideal system since it exhibits 3 close-lying electronic transitions that are bright but also subjected to HT effects. To single out the different contributions to vRR line shapes the authors adopted 2 different adiabatic models for resonant-state potential energy surfaces, namely, Adiabatic Shift (only accounting from equil. geometry displacements) and Adiabatic Hessian (AH, including also the Duschinsky effects), and Franck-Condon (FC) or HT approxns. for the transition dipole. On balance, FC+HT calcns. within the AH model provide the best agreement with expt. Also, the methodol. permits to individuate bands in the exptl. spectra due to the simultaneous contribution of >1 resonant state and to point out and analyze interferential effects between the FC and HT terms in each resonance Raman process, together with FC-HT and HT-HT interferences between different electronic states.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXpsFGmtb0%253D&md5=4f68741ea896d01b5efffe08c008b3ae
  56. 56
    Petelenz, P.; Andrzejak, M. Vibronic Interpretation of the Low-Energy Absorption Spectrum of the Sexithiophene Single Crystal. J. Chem. Phys. 2000, 113 (24), 11306– 11314,  DOI: 10.1063/1.1290026
    Google Scholar
    There is no corresponding record for this reference.
  57. 57
    Witkowski, A.; Moffitt, W. Electronic Spectra of Dimers - Derivation of the Fundamental Vibronic Equations. J. Chem. Phys. 1960, 33 (3), 872– 875,  DOI: 10.1063/1.1731278
    Google Scholar
    There is no corresponding record for this reference.
  58. 58
    Zgierski, M. Z.; Pawlikowski, M. Absorption and Circular-Dichroism Spectra of Dimeric Systems - Extended Dimer Model. J. Chem. Phys. 1983, 79 (4), 1616– 1633,  DOI: 10.1063/1.446033
    Google Scholar
    There is no corresponding record for this reference.
  59. 59
    Bizimana, L. A.; Carbery, W. P.; Gellen, T. A.; Turner, D. B. Signatures of Herzberg-Teller Coupling in Three-Dimensional Electronic Spectroscopy. J. Chem. Phys. 2017, 146 (8), 084311,  DOI: 10.1063/1.4976995
    Google Scholar
    There is no corresponding record for this reference.
  60. 60
    Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77 (18), 3865– 3868,  DOI: 10.1103/PhysRevLett.77.3865
    Google Scholar
    60
    Generalized gradient approximation made simple
    Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
    Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XmsVCgsbs%253D&md5=55943538406ee74f93aabdf882cd4630
  61. 61
    Günder, D.; Valencia, A. M.; Guerrini, M.; Breuer, T.; Cocchi, C.; Witte, G. Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN: PFP Cocrystalline Films: Limits of Nonperiodic Modeling. J. Phys. Chem. Lett. 2021, 12 (40), 9899– 9905,  DOI: 10.1021/acs.jpclett.1c02761
    Google Scholar
    There is no corresponding record for this reference.
  62. 62
    Valencia, A. M.; Bischof, D.; Anhäuser, S.; Zeplichal, M.; Terfort, A.; Witte, G.; Cocchi, C. Excitons in Organic Materials: Revisiting Old Concepts with New Insights. Electron. Struct. 2023, 5 (3), 033003,  DOI: 10.1088/2516-1075/acf2d4
    Google Scholar
    There is no corresponding record for this reference.
  63. 63
    Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P. Principles and Applications of Broadband Impulsive Vibrational Spectroscopy. J. Phys. Chem. A 2015, 119 (36), 9506– 9517,  DOI: 10.1021/acs.jpca.5b05948
    Google Scholar
    63
    Principles and Applications of Broadband Impulsive Vibrational Spectroscopy
    Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P.
    Journal of Physical Chemistry A (2015), 119 (36), 9506-9517CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
    An exptl. setup is presented for recording vibrational coherences and Raman spectra of mols. in their ground and excited electronic states at 50-3000 cm-1 using broadband impulsive vibrational spectroscopy. The approach relies on the combination of a <10 fs excitation pulse with an uncompressed white light continuum probe, which drastically reduces exptl. complexity compared to frequency domain based techniques. The parameters detg. vibrational coherence amplitudes, outline how to optimize the exptl. setup including approaches aimed at conclusively assigning vibrational coherences to specific electronic states, and provide a clear comparison with existing techniques are discussed. To demonstrate the applicability of the spectroscopic approach, several examples reveal the evolution of vibrational coherence in rhodopsin and β-carotene.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlSmt7rJ&md5=0099060f0280493b160d6570da65c8de
  64. 64
    Lanzani, G.; Cerullo, G.; De Silvestri, S. Coherent Vibrational Dynamics; CRC Press, 2007.
    Google Scholar
    There is no corresponding record for this reference.
  65. 65
    Grupp, A.; Budweg, A.; Fischer, M. P.; Allerbeck, J.; Soavi, G.; Leitenstorfer, A.; Brida, D. Broadly Tunable Ultrafast Pump-Probe System Operating at Multi-kHz Repetition Rate. J. Opt. 2018, 20 (1), 014005,  DOI: 10.1088/2040-8986/aa9b07
    Google Scholar
    There is no corresponding record for this reference.
  66. 66
    Brida, D.; Manzoni, C.; Cerullo, G. Phase-Locked Pulses for Two-Dimensional Spectroscopy by a Birefringent Delay Line. Opt. Lett. 2012, 37 (15), 3027– 3029,  DOI: 10.1364/OL.37.003027
    Google Scholar
    66
    Phase-locked pulses for two-dimensional spectroscopy by a birefringent delay line
    Brida Daniele; Manzoni Cristian; Cerullo Giulio
    Optics letters (2012), 37 (15), 3027-9 ISSN:.
    We introduce the translating wedge-based identical pulses encoding system, a novel device for the generation of collinear, interferometrically locked ultrashort pulse pairs. By means of birefringent wedges, we are able to control the pulse delay with attosecond precision and stability better that λ/360, without affecting the pulse duration and in a spectral range that spans from UV to mid-IR. This device is expected to dramatically simplify two-dimensional spectroscopy experiments.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC38flt1Sqsg%253D%253D&md5=774e1891ccbfb9f8581dab50436ee22e
  67. 67
    Frisch, M. e.; Trucks, G.; Schlegel, H. B.; Scuseria, G.; Robb, M.; Cheeseman, J.; Scalmani, G.; Barone, V.; Petersson, G.; Nakatsuji, H. Gaussian 16; Gaussian, Inc.: Wallingford, CT, 2016.
    Google Scholar
    There is no corresponding record for this reference.
  68. 68
    Lee, S. Y.; Heller, E. J. Time-Dependent Theory of Raman Scattering. J. Chem. Phys. 1979, 71 (12), 4777– 4788,  DOI: 10.1063/1.438316
    Google Scholar
    68
    Time-dependent theory of Raman scattering
    Lee, Soo-Y.; Heller, E. J.
    Journal of Chemical Physics (1979), 71 (12), 4777-88CODEN: JCPSA6; ISSN:0021-9606.
    A time-dependent picture of vibrational Raman scattering in the weak field limit is presented. From this viewpoint the static effects, due to the coordinate dependence of the electronic transition dipole, can be sepd. from the dynamic effects that arise from wave packet propagation on the Born-Oppenheimer surfaces. Away from resonance, the energy uncertainty relation gives the propagation time necessary to obtain the cross section as being inversely proportional to the mismatch of the excitation frequency with the excited surface. The wave packet, given by the initial vibrational wave function times the transition dipole, hardly moves on the excited surface when the excitation frequency is far from resonance. As the excitation frequency is tuned closer to resonance, the propagated wave packet samples a larger portion of the surface. By using the short time approxn. to the propagator, formulas were obtained for the cross section that are applicable for Raman scattering by polyatomics. The short time approxn. is expected to be good away from resonance independent of the nature of the surface, and also on resonance with a repulsive surface. For an attractive surface, the approxn. gives the av. resonant cross section useful in the case when the vibrational structures cannot be obsd.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3cXms12ltA%253D%253D&md5=4233d1d72a3c69c20cb74a9e7c27ef2a
  69. 69
    Porezag, D.; Pederson, M. R. Infrared Intensities and Raman-Scattering Activities Within Density-Functional Theory. Phys. Rev. B 1996, 54 (11), 7830,  DOI: 10.1103/PhysRevB.54.7830
    Google Scholar
    69
    Infrared intensities and Raman-scattering activities within density-functional theory
    Porezag, Dirk; Pederson, Mark R.
    Physical Review B: Condensed Matter (1996), 54 (11), 7830-7836CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
    The computational complexity assocd. with the d.-functional-based detn. of IR intensities and nonresonant Raman scattering activities is the same as that required for vibrational modes. Further, the authors use extremely large basis sets to det. the intrinsic accuracy for calcg. such phenomena within the d.-functional theory. The authors present benchmark calcns. on CH4, H2O, C2H2, C2H4, and C2H6 within both the local-d. approxn. (LDA) and the generalized gradient approxn. (GGA). Tests of the reliability and numerical stability of the theor. scheme are presented. To obtain reliable results, appropriate polarization basis functions and well-converged wave functions are necessary. While most of the Raman spectra predicted by LDA agree very well with exptl. data, some of the IR intensities show substantial errors. The GGA functional overcomes most of these deficiencies, leading to an overall good agreement with expt.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XmtVWrtb0%253D&md5=284a618dbda84734a287f7affa0eea2b

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  • Abstract

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    Figure 1

    Figure 1. Correlation between crystalline orientation and optical response of perfluoropentacene (PFP). Molecular stacking patterns of (a) a 200 nm thick single-crystalline PFP film on a NaF(100) substrate and (b) a 100 nm thick single-crystalline PFP layer on a KCl(100) substrate. On NaF(100), with upright standing molecular orientation, the (b⃗c⃗)-plane of PFP is parallel to the substrate. For KCl, with recumbent molecular orientation, the (a⃗b⃗)-plane is parallel to the substrate. (c, d) Scheme of the polarization of the co-linearly polarized pump and probe lasers used to selectively excite and probe PFP on NaF (c) and PFP on KCl (d) with light polarized along one of the crystal axes. Differential transmission (ΔT/T) map recorded for linear polarization along the (e) b⃗- and (f) c⃗-axes of PFP on NaF and along the (g) b⃗- and (h) a⃗-axes of PFP on KCl. (i) Time-averaged ΔT/T spectra obtained from the ΔT/T maps in (e-h). The polarization of laser pulses along a specific crystal orientation are color-coded as in (e-h). (j) Cross sections of the ΔT/T maps in (e-h) as a function of delay time for a fixed probe energy, indicated by the dashed lines in (e-h). The ΔT/T for polarization along a⃗, magnified by a factor of 10 in (h-j) stems from a small number of residual minority domains oriented along b⃗.

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    Figure 2

    Figure 2. Transient differential transmission ΔT(td,ED)/T recorded for PFP on NaF(100) with pulses polarized (a) along the b⃗-axis at a detection energy of 1.78 eV and (b) along the c⃗-axis at a detection energy of ED = 1.75 eV. The polarization direction is illustrated in the insets. Both plots show a dominant modulation with 25 fs period although for polarization along b⃗, low-frequency oscillation beatings are more pronounced. The solid red and dashed blue lines are biexponential decay functions and are introduced to guide the eye.

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    Figure 3

    Figure 3. (a) Residual map showing the oscillatory modulation of the ΔT/T signals in Figure 1e, recorded for PFP on NaF for co-linearly polarized pump and probe pulses polarized along the b⃗-axis of PFP. In these residuals, slowly decaying incoherent ΔT/T signals have been subtracted from the pump–probe data to emphasize the oscillatory modulation induced by coherent lattice vibrations. The residuals are shown for waiting times between 0.12 and 2.0 ps. (b) Cross section through the residual map in (a) for two representative probe energies of 1.78 eV (black) and 1.85 eV (red), marked as dashed line in (a). The signals are dominated by a high-frequency oscillation at 25 fs and superimposed by several different beating patterns. (c-e) Cross sections through the residual maps for PFP on NaF (c⃗-axis) (c), PFP on KCl (b⃗-axis) (d) and PFP on KCl (a⃗-axis) (e). The cross sections are shown at probe energies of 1.78 eV (black) and 1.85 eV (red) and for time delays between 0.12 and 2.0 ps. In (b-e), the residuals at the two probe energies are vertically shifted by 10% for clarity.

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    Figure 4

    Figure 4. Normalized energy-resolved Fourier transform spectra obtained from the residuals of the ΔT/T maps in Figure 1e-h for excitation and probing along the (a) b⃗- and (b) c⃗-axis of PFP/NaF(100) and along the (c) b⃗- and (d) a⃗-axis of PFP/KCl(100). The amplitudes of the Fourier transform spectra are shown as a function of wavenumber and detection energy ED. The amplitude of the data in (d) is 10-times smaller than that in a-c since only a small portion of minority domains with b⃗-orientation are excited. The Fourier transform spectra are dominated by vibrational modes around 1320 cm–1, 774 cm–1, 384 cm–1 and 178 cm–1. Cross sections along ED for the 384 cm–1 mode are displayed in the insets. Note the change in spectrum of this mode for c⃗-axis excitation PFP/NaF(100) in comparison to that for excitation along b⃗.

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    Figure 5

    Figure 5. Fourier spectra (black lines), integrated along the probe energy in Figure 4 and recorded for excitation along the (a) b⃗- and (b) c⃗- axis of PFP/NaF(100) and along the (c) b⃗- and (d) a⃗- axis of PFP/KCl(100). As in Figures 1h and 2d, the amplitude of the spectrum in (d) is 10 times smaller since only a small portion of minority domains with b⃗-orientation are excited. Corresponding off-resonance Raman spectra recorded for linearly polarized excitation at 785 nm are shown in red. The Raman spectra have been shifted vertically by −0.3 for clarity.

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    Figure 6

    Figure 6. (a) Infrared (IR, gray area) and resonant Raman spectra (red) of an isolated PFP molecule in vacuo calculated using DFT with the PBE functional. (b) Visualization of selected Raman active modes. C atoms are shown in gray and F atoms in cyan. The arrows indicate the directions of the atomic displacements. Both spectra are broadened by a Lorentzian function with a fwhm of 5 cm–1.

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  • References

    This article references 69 other publications.

    1. 1
      Klauk, H. Organic Electronics: Materials, Manufacturing and Applications; Wiley-VCH, 2006.
      There is no corresponding record for this reference.
    2. 2
      Brédas, J. L.; Marder, S. R. The WSPC Reference on Organic Electronics: Organic Semiconductors; World Scientific, 2016.
      There is no corresponding record for this reference.
    3. 3
      Ostroverkhova, O. Organic Optoelectronic Materials: Mechanisms and Applications. Chem. Rev. 2016, 116 (22), 13279– 13412,  DOI: 10.1021/acs.chemrev.6b00127
      3
      Organic Optoelectronic Materials: Mechanisms and Applications
      Ostroverkhova, Oksana
      Chemical Reviews (Washington, DC, United States) (2016), 116 (22), 13279-13412CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. Org. (opto)electronic materials have received considerable attention due to their applications in thin-film-transistors, light-emitting diodes, solar cells, sensors, photorefractive devices, and many others. The technol. promises include low cost of these materials and the possibility of their room-temp. deposition from soln. on large-area and/or flexible substrates. The article reviews the current understanding of the phys. mechanisms that det. the (opto)electronic properties of high-performance org. materials. The focus of the review is on photoinduced processes and on electronic properties important for optoelectronic applications relying on charge carrier photogeneration. Addnl., it highlights the capabilities of various exptl. techniques for characterization of these materials, summarizes top-of-the-line device performance, and outlines recent trends in the further development of the field. The properties of materials based both on small mols. and on conjugated polymers are considered, and their applications in org. solar cells, photodetectors, and photorefractive devices are discussed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xhs1egsLnM&md5=4ab815e1951d3749bf2a5bbd93106a9b
    4. 4
      Rand, B. P.; Cheyns, D.; Vasseur, K.; Giebink, N. C.; Mothy, S.; Yi, Y.; Coropceanu, V.; Beljonne, D.; Cornil, J.; Brédas, J.-L. The Impact of Molecular Orientation on the Photovoltaic Properties of a Phthalocyanine/Fullerene Heterojunction. Adv. Funct. Mater. 2012, 22 (14), 2987– 2995,  DOI: 10.1002/adfm.201200512
      4
      The Impact of Molecular Orientation on the Photovoltaic Properties of a Phthalocyanine/Fullerene Heterojunction
      Rand, Barry P.; Cheyns, David; Vasseur, Karolien; Giebink, Noel C.; Mothy, Sebastien; Yi, Yuanping; Coropceanu, Vaeceslav; Beljonne, David; Cornil, Jerome; Bredas, Jean-Luc; Genoe, Jan
      Advanced Functional Materials (2012), 22 (14), 2987-2995CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The anisotropy inherent to many planar org. mols. leads to a high sensitivity of various fundamental processes to the orientation of mols. within films and at heterojunctions. Such processes include absorption, charge and exciton transport, energy levels, and charge transfer, all of which are crit. to org. solar cell operation. Here,an in-depth study of bilayer cells consisting of a donor/acceptor interface between zinc phthalocyanine (ZnPc) and fullerene (C60) is conducted and devices with the typically deposited standing up (edge-on) orientation are compared to those with ZnPc lying flat (face-on). The face-on ZnPc-based device allows for an increase in all solar cell parameters, substantially increasing power conversion efficiency from 1.5% to 2.8%. Spectrally resolved photocurrent measurements reveal a >50% increase in ZnPc signal, from which only 12% is accounted for by the increase in absorption assocd. with the face-on orientation. The increase in internal quantum efficiency is accounted for via an improved charge transfer. The results of this study indicate that proper consideration of the orientation between donor and acceptor needs to be taken to fully optimize the numerous processes required for photovoltaic energy conversion.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xls1elsr4%253D&md5=8bf9b0dffbdcb55f4bf37f16b543b34b
    5. 5
      Karl, N. Charge Carrier Transport in Organic Semiconductors. Synth. Met. 2003, 133–134, 649– 657,  DOI: 10.1016/S0379-6779(02)00398-3
      5
      Charge carrier transport in organic semiconductors
      Karl, N.
      Synthetic Metals (2003), 133-134 (), 649-657CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier Science B.V.)
      A review. To understand charge carrier transport in org. semiconductors the magnitude and anisotropy, as well as the temp. and eventual elec. field dependence of the electron and of the hole mobility are fundamental parameters. A no. of tech. applications require high mobilities. A brief review is given on different exptl. methods that can either directly measure charge carrier mobilities, or at least lead to an est. For high purity single crystals, a steep increase of mobilities towards low temp. with the consequence of nonlinear transport and final velocity satn. at elevated elec. fields was found and traced back to temp.-dependent electron and hole masses approaching the free electron mass at low temp. This, and addnl. recent reports in literature on ultrahigh mobilities-with a no. of exciting consequences, such as integer and fractional quantum Hall effect and even supercond. in such materials as anthracene, tetracene, pentacene, and C60-are clear indications of band transport. With rising temp. electron-phonon coupling, and therefore the effective masses, increase and coherent band transport is gradually destroyed; polaron-hopping transport evolves as a parallel channel and dominates at sufficiently high temp. For crystals with orientational disorder of the mols. band transport is precluded.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXhvFWhu78%253D&md5=ff758217b810ffedeeb3ce430c424a52
    6. 6
      Podzorov, V.; Menard, E.; Borissov, A.; Kiryukhin, V.; Rogers, J. A.; Gershenson, M. E. Intrinsic Charge Transport on the Surface of Organic Semiconductors. Phys. Rev. Lett. 2004, 93 (8), 086602,  DOI: 10.1103/PhysRevLett.93.086602
      6
      Intrinsic Charge Transport on the Surface of Organic Semiconductors
      Podzorov, V.; Menard, E.; Borissov, A.; Kiryukhin, V.; Rogers, J. A.; Gershenson, M. E.
      Physical Review Letters (2004), 93 (8), 086602/1-086602/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      The air-gap field-effect technique enabled realization of the intrinsic (not limited by static disorder) polaronic transport on the surface of rubrene (C42H28) crystals over a wide temp. range. The signatures of this intrinsic transport are the anisotropy of the carrier mobility, μ, and the growth of μ with cooling. Anisotropy of μ vanishes in the activation regime at low temps., where the transport is dominated by shallow traps. The deep traps, introduced by x-ray radiation, increase the field-effect threshold without affecting μ, an indication that the filled traps do not scatter polarons.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXmvVCmu70%253D&md5=0c17a1860622a0c0b61a44b8fd2b2c86
    7. 7
      Repp, J.; Liljeroth, P.; Meyer, G. Coherent Electron–Nuclear Coupling in Oligothiophene Molecular Wires. Nat. Phys. 2010, 6 (12), 975– 979,  DOI: 10.1038/nphys1802
      There is no corresponding record for this reference.
    8. 8
      Du, S.; Yoshida, K.; Zhang, Y.; Hamada, I.; Hirakawa, K. Terahertz Dynamics of Electron–Vibron Coupling in Single Molecules with Tunable Electrostatic Potential. Nat. Photonics. 2018, 12 (10), 608– 612,  DOI: 10.1038/s41566-018-0241-1
      8
      Terahertz dynamics of electron-vibron coupling in single molecules with tunable electrostatic potential
      Du, Shaoqing; Yoshida, Kenji; Zhang, Ya; Hamada, Ikutaro; Hirakawa, Kazuhiko
      Nature Photonics (2018), 12 (10), 608-612CODEN: NPAHBY; ISSN:1749-4885. (Nature Research)
      Clarifying electronic and vibronic properties at the individual mol. level provides key insights for future chem., nanoelectronics and quantum information technologies. However, information obtained by conventional single-mol. transport measurements is based on time-averaged properties. Here, we report on terahertz (THz) spectroscopy of single fullerene mols. by using a single-mol. transistor geometry. From the time-domain THz autocorrelation measurements, we obtained THz spectra assocd. with the THz-induced center-of-mass oscillation of the mols. The obsd. spectra reflect the potential profile experienced by the mol. on the metal surface when the no. of electrons on the mol. fluctuates by one during the single-electron tunnelling process. Such an ultra-high sensitivity to the electronic/vibronic structures of a single mol. on the addn./removal of a single electron has been achieved as a result of using THz spectroscopy in the single-mol. transistor geometry. This scheme provides an opportunity to investigate the ultrafast THz dynamics of subnanometre-scale systems.
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    9. 9
      Kong, F.-F.; Tian, X.-J.; Zhang, Y.; Yu, Y.-J.; Jing, S.-H.; Zhang, Y.; Tian, G.-J.; Luo, Y.; Yang, J.-L.; Dong, Z.-C. Probing Intramolecular Vibronic Coupling Through Vibronic-State Imaging. Nat. Commun. 2021, 12 (1), 1280,  DOI: 10.1038/s41467-021-21571-z
      9
      Probing intramolecular vibronic coupling through vibronic-state imaging
      Kong, Fan-Fang; Tian, Xiao-Jun; Zhang, Yang; Yu, Yun-Jie; Jing, Shi-Hao; Zhang, Yao; Tian, Guang-Jun; Luo, Yi; Yang, Jin-Long; Dong, Zhen-Chao; Hou, J. G.
      Nature Communications (2021), 12 (1), 1280CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)
      Vibronic coupling is a central issue in mol. spectroscopy. Here we investigate vibronic coupling within a single pentacene mol. in real space by imaging the spatial distribution of single-mol. electroluminescence via highly localized excitation of tunneling electrons in a controlled plasmonic junction. The obsd. two-spot orientation for certain vibronic-state imaging is found to be evidently different from the purely electronic 0-0 transition, rotated by 90°, which reflects the change in the transition dipole orientation from along the mol. short axis to the long axis. Such a change reveals the occurrence of strong vibronic coupling assocd. with a large Herzberg-Teller contribution, going beyond the conventional Franck-Condon picture. The emergence of large vibration-induced transition charges oscillating along the long axis is found to originate from the strong dynamic perturbation of the anti-sym. vibration on those carbon atoms with large transition d. populations during electronic transitions.
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    10. 10
      Breuer, T.; Witte, G. Epitaxial Growth of Perfluoropentacene Films with Predefined Molecular Orientation: A Route for Single-Crystal Optical Studies. Phys. Rev. B 2011, 83 (15), 155428,  DOI: 10.1103/PhysRevB.83.155428
      There is no corresponding record for this reference.
    11. 11
      Condon, E. A Theory of Intensity Distribution in Band Systems. Phys. Rev. 1926, 28 (6), 1182– 1201,  DOI: 10.1103/PhysRev.28.1182
      11
      Theory of intensity distribution in band systems
      Condon, Edward
      Physical Review (1926), 28 (), 1182-1201CODEN: PHRVAO; ISSN:0031-899X.
      There is no expanded citation for this reference.
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    12. 12
      Spano, F. C. Excitons in Conjugated Oligomer Aggregates, Films, and Crystals. Annu. Rev. Phys. Chem. 2006, 57, 217– 243,  DOI: 10.1146/annurev.physchem.57.032905.104557
      12
      Excitons in conjugated oligomer aggregates, films, and crystals
      Spano, Frank C.
      Annual Review of Physical Chemistry (2006), 57 (), 217-243CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews Inc.)
      A review. Recent exptl. and theor. investigations of excitons in conjugated oligomer nanoaggregates, thin films, and crystals are reviewed. The review focuses on the technol. important unsubstituted oligo(phenylene vinylene)s (OPVn) and oligothiophenes (OTn), which exhibit side-by-side herringbone crystal packing. Many of the salient photophys. properties displayed by OPVn and OTn solid phases, including the large Davydov splitting, the rich variety of peaks due to vibronic coupling in both absorption and emission, and the unusual behavior of the emission origin, are accounted for in a model including excitonic coupling between mols., linear exciton-phonon coupling, and disorder.
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    13. 13
      Wykes, M.; Parambil, R.; Beljonne, D.; Gierschner, J. Vibronic Coupling in Molecular Crystals: A Franck-Condon Herzberg-Teller Model of H-Aggregate Fluorescence Based on Quantum Chemical Cluster Calculations. J. Chem. Phys. 2015, 143 (11), 114116,  DOI: 10.1063/1.4930606
      13
      Vibronic coupling in molecular crystals: A Franck-Condon Herzberg-Teller model of H-aggregate fluorescence based on quantum chemical cluster calculations
      Wykes, M.; Parambil, R.; Beljonne, D.; Gierschner, J.
      Journal of Chemical Physics (2015), 143 (11), 114116/1-114116/12CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      Here, the authors present a general approach to treating vibronic coupling in mol. crystals based on atomistic simulations of large clusters. Such clusters comprise model aggregates treated at the quantum chem. level embedded within a realistic environment treated at the mol. mechanics level. As the authors calc. ground and excited state equil. geometries and vibrational modes of model aggregates, approach is able to capture effects arising from coupling to intermol. degrees of freedom, absent from existing models relying on geometries and normal modes of single mols. Using the geometries and vibrational modes of clusters, the authors are able to simulate the fluorescence spectra of aggregates for which the lowest excited state bears negligible oscillator strength (as is the case, e.g., ideal H-aggregates) by including both Franck-Condon (FC) and Herzberg-Teller (HT) vibronic transitions. The latter terms allow the adiabatic excited state of the cluster to couple with vibrations in a perturbative fashion via derivs. of the transition dipole moment along nuclear coordinates. While vibronic coupling simulations employing FC and HT terms are well established for single-mols., to knowledge this is the first time they are applied to mol. aggregates. Here, the authors apply this approach to the simulation of the low-temp. fluorescence spectrum of para-distyrylbenzene single-crystal H-aggregates and draw comparisons with coarse-grained Frenkel-Holstein approaches previously extensively applied to such systems. (c) 2015 American Institute of Physics.
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    14. 14
      Small, G. J. Herzberg-Teller Vibronic Coupling and Duschinsky Effect. J. Chem. Phys. 1971, 54 (8), 3300,  DOI: 10.1063/1.1675343
      14
      Herzberg-Teller vibronic coupling and the Duschinsky effect
      Small, Gerald J.
      Journal of Chemical Physics (1971), 54 (8), 3300-6CODEN: JCPSA6; ISSN:0021-9606.
      The assumption that the difference in compn., in terms of symmetry coordinates, between the normal vibrational motions of the ground and 1st excited state (Duschinsky effect) can be neglected in the Herzberg-Teller theory of absorption and fluorescence vibronic intensities is crit. examd. A theory of the Duschinsky effect is described which involves expansion of the potential energy of the fluorescent state in terms of the ground state normal coordinate displacements. Off-diagonal quadratic contributions arise in the expansion whenever there is a coupling between the crude Born-Oppenheimer electronic wavefunctions of the fluorescent and other excited states through 2 or more ground state normal motions of the same symmetry. The importance of the Duschinsky effect depends on the magnitudes of the Herzberg-Teller vibronic matrix elements and the frequency differences between the fundamentals which effect vibronic perturbations. Inclusion of the Duschinsky effect in the Herzberg-Teller theory for 2 or more nontotally symmetric perturbing vibrations introduces a constructive-destructive interference problem, involving the "forbidden" transition moments similar to the one that arises in the theory of Craig and Small on totally symmetric vibrational perturbations. The interferences can lead to a breakdown in mirror symmetry between the absorption and fluorescence spectra. The theory presented for a 2 vibrational model enables the relative signs of the 2 forbidden moments to be detd. by comparison of the relative intensities of 2 vibronic bands in absorption and fluorescence. In the case of naphthalene the forbidden moments assocd. with 509 and 938 cm-b3g modes are antiparallel. Calcns. for phenanthrene suggest that, although the Duschinsky effect should be included in any attempt at accurate vibronic intensity calcns., the constructive-destructive interference effects described by Craig and Small are primarily responsible for the gross deviations from mirror symmetry exptl. obsd. Illustrative calcns. show that the Duschinsky effect should not be neglected in the Herzberg-Teller theory of both fluorescence and absorption vibronic intensities.
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    15. 15
      Kundu, S.; Roy, P. P.; Fleming, G. R.; Makri, N. Franck–Condon and Herzberg–Teller Signatures in Molecular Absorption and Emission Spectra. J. Phys. Chem. B 2022, 126 (15), 2899– 2911,  DOI: 10.1021/acs.jpcb.2c00846
      There is no corresponding record for this reference.
    16. 16
      Kim, W.; Musser, A. J. Tracking Ultrafast Reactions in Organic Materials Through Vibrational Coherence: Vibronic Coupling Mechanisms in Singlet Fission. Adv. Phys. X. 2021, 6 (1), 1918022,  DOI: 10.1080/23746149.2021.1918022
      There is no corresponding record for this reference.
    17. 17
      De Sio, A.; Sommer, E.; Nguyen, X. T.; Gross, L.; Popovic, D.; Nebgen, B. T.; Fernandez-Alberti, S.; Pittalis, S.; Rozzi, C. A.; Molinari, E. Intermolecular Conical Intersections in Molecular Aggregates. Nat. Nanotechnol 2021, 16 (1), 63– 68,  DOI: 10.1038/s41565-020-00791-2
      There is no corresponding record for this reference.
    18. 18
      Singh, S.; Jones, W. J.; Siebrand, W.; Stoicheff, B. P.; Schneider, W. G. Laser Generation of Excitons and Fluorescencence in Anthracene Crystals. J. Chem. Phys. 1965, 42 (1), 330– 342,  DOI: 10.1063/1.1695695
      There is no corresponding record for this reference.
    19. 19
      Smith, M. B.; Michl, J. Singlet Fission. Chem. Rev. 2010, 110 (11), 6891– 6936,  DOI: 10.1021/cr1002613
      19
      Singlet Fission
      Smith, Millicent B.; Michl, Josef
      Chemical Reviews (Washington, DC, United States) (2010), 110 (11), 6891-6936CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. A theory of singlet fission is discussed along with its relation to photovoltaics. The literature is reviewed dealing with singlet fission in org. chromophores from the time of initial discovery of singlet fission to the present day.
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    20. 20
      Smith, M. B.; Michl, J. Recent Advances in Singlet Fission. Annu. Rev. Phys. Chem. 2013, 64, 361– 386,  DOI: 10.1146/annurev-physchem-040412-110130
      20
      Recent advances in singlet fission
      Smith, Millicent B.; Michl, Josef
      Annual Review of Physical Chemistry (2013), 64 (), 361-386CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews Inc.)
      A review. A survey is provided of recent progress in the understanding of singlet fission, a spin-allowed process in which a singlet excited mol. shares its energy with a ground-state neighbor to produce two triplet excited mols. It has been obsd. to occur in single-crystal, polycryst., and amorphous solids, on timescales from 80 fs to 25 ps, producing triplet yields as high as 200%. Photovoltaic devices using the effect have shown external quantum efficiencies in excess of 100%. Almost all the efficient materials are alternant hydrocarbons of the acene series or their simple derivs., and it is argued that a wider structural variety would be desirable. The current state of the development of mol. structure design rules, based on first-principles theor. considerations, is described along with initial examples of implementation.
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    21. 21
      Monahan, N.; Zhu, X. Y. Charge Transfer-Mediated Singlet Fission. Annu. Rev. Phys. Chem. 2015, 66, 601– 618,  DOI: 10.1146/annurev-physchem-040214-121235
      21
      Charge transfer-mediated singlet fission
      Monahan, N.; Zhu, X.-Y.
      Annual Review of Physical Chemistry (2015), 66 (), 601-618CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews)
      Singlet fission, the splitting of a singlet exciton into two triplet excitons in mol. materials, is interesting not only as a model many-electron problem, but also as a process with potential applications in solar energy conversion. Here we discuss limitations of the conventional four-electron and mol. dimer model in describing singlet fission in cryst. org. semiconductors, such as pentacene and tetracene. We emphasize the need to consider electronic delocalization, which is responsible for the decisive role played by the Mott-Wannier exciton, also called the charge transfer (CT) exciton, in mediating singlet fission. At the strong electronic coupling limit, the initial excitation creates a quantum superposition of singlet, CT, and triplet-pair states, and we present exptl. evidence for this interpretation. We also discuss the most recent attempts at translating this mechanistic understanding into design principles for CT state-mediated intramol. singlet fission in oligomers and polymers.
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    22. 22
      Walker, B. J.; Musser, A. J.; Beljonne, D.; Friend, R. H. Singlet Exciton Fission in Solution. Nat. Chem. 2013, 5 (12), 1019– 1024,  DOI: 10.1038/nchem.1801
      22
      Singlet exciton fission in solution
      Walker, Brian J.; Musser, Andrew J.; Beljonne, David; Friend, Richard H.
      Nature Chemistry (2013), 5 (12), 1019-1024CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)
      Singlet exciton fission, the spin-conserving process that produces two triplet excited states from one photoexcited singlet state, is a means to circumvent the Shockley-Queisser limit in single-junction solar cells. Although the process through which singlet fission occurs is not well characterized, some local order is thought to be necessary for intermol. coupling. Here, we report a triplet yield of 200% and triplet formation rates approaching the diffusion limit in solns. of bis(triisopropylsilylethynyl (TIPS)) pentacene. We observe a transient bound excimer intermediate, formed by the collision of one photoexcited and one ground-state TIPS-pentacene mol. The intermediate breaks up when the two triplets sep. to each TIPS-pentacene mol. This efficient system is a model for future singlet-fission materials and for disordered device components that produce cascades of excited states from sunlight.
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    23. 23
      Wilson, M. W.; Rao, A.; Ehrler, B.; Friend, R. H. Singlet Exciton Fission in Polycrystalline Pentacene: From Photophysics Toward Devices. Acc. Chem. Res. 2013, 46 (6), 1330– 1338,  DOI: 10.1021/ar300345h
      23
      Singlet Exciton Fission in Polycrystalline Pentacene: From Photophysics toward Devices
      Wilson, Mark W. B.; Rao, Akshay; Ehrler, Bruno; Friend, Richard H.
      Accounts of Chemical Research (2013), 46 (6), 1330-1338CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
      A review. Singlet exciton fission is the process in conjugated org. mols. by which a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers 1st reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These studies used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest was recently re-kindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating addnl. photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chem., and small-mol. device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycryst. thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, the authors review the results of recent transient absorption and device-based studies of polycryst. pentacene. The authors address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins conclusion that singlet fission in pentacene is extraordinarily rapid (∼80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, demonstration that triplet excitons generated via singlet fission in pentacene can be dissocd. at an interface with a suitable electron acceptor, such as fullerenes and IR-absorbing inorg. semiconducting quantum dots are discussed. The authors highlight recent reports of a pentacene/PbSe hybrid solar cell with a power conversion efficiency of 4.7% and of a pentacene/PbSe/amorphous Si photovoltaic device. Although substantive challenges remain, both to better understanding of the mechanism of singlet exciton fission and to optimize device performance, this realization of a solar cell where photocurrent is simultaneously contributed from a blue-absorbing fission-capable material and an IR-absorbing conventional cell is an important step towards a dual-bandgap, single-junction, fission-enhanced photovoltaic device, which could 1 day surpass the Shockley-Queisser limit.
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    24. 24
      Musser, A. J.; Liebel, M.; Schnedermann, C.; Wende, T.; Kehoe, T. B.; Rao, A.; Kukura, P. Evidence for Conical Intersection Dynamics Mediating Ultrafast Singlet Exciton Fission. Nat. Phys. 2015, 11 (4), 352– 357,  DOI: 10.1038/nphys3241
      24
      Evidence for conical intersection dynamics mediating ultrafast singlet exciton fission
      Musser, Andrew J.; Liebel, Matz; Schnedermann, Christoph; Wende, Torsten; Kehoe, Tom B.; Rao, Akshay; Kukura, Philipp
      Nature Physics (2015), 11 (4), 352-357CODEN: NPAHAX; ISSN:1745-2473. (Nature Publishing Group)
      Singlet exciton fission is the process in org. semiconductors through which a spin-singlet exciton converts into a pair of spin-triplet excitons residing on different chromophores, entangled in an overall spin-zero state. For some systems, singlet fission has been shown to occur on the 100 fs timescale and with a 200% quantum yield, but the mechanism of this process remains uncertain. Here we study a model singlet fission system, TIPS-pentacene, using ultrafast vibronic spectroscopy. We observe that vibrational coherence in the initially photogenerated singlet state is transferred to the triplet state and show that this behavior is effectively identical to ultrafast internal conversion for polyenes in soln. This similarity in vibronic dynamics suggests that both multi-mol. singlet fission and single-mol. internal conversion are mediated by the same underlying relaxation processes, based on strong coupling between nuclear and electronic degrees of freedom. In its most efficient form this leads to a conical intersection between the coupled electronic states.
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    25. 25
      Chan, W.-L.; Ligges, M.; Jailaubekov, A.; Kaake, L.; Miaja-Avila, L.; Zhu, X.-Y. Observing the Multiexciton State in Singlet Fission and Ensuing Ultrafast Multielectron Transfer. Science 2011, 334 (6062), 1541– 1545,  DOI: 10.1126/science.1213986
      25
      Observing the Multiexciton State in Singlet Fission and Ensuing Ultrafast Multielectron Transfer
      Chan, Wai-Lun; Ligges, Manuel; Jailaubekov, Askat; Kaake, Loren; Miaja-Avila, Luis; Zhu, X.-Y.
      Science (Washington, DC, United States) (2011), 334 (6062), 1541-1545CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      Two for One Conventional solar cells create a charge carrier each time a photon of light at or above a certain energy threshold is absorbed. Any energy embedded in short-wavelength photons that exceeds the threshold is largely wasted. Semonin et al. (p. ) now demonstrate a nanoparticulate lead selenide solar cell that channels a fraction of the excess energy into current. Chan et al. (p. ) explored the fundamental dynamics of multiple carrier generation in an org. (rather than inorg.) absorber and characterized a short-lived state that bridges the high-energy single carrier state and two discrete lower-energy carrier states. Multiple exciton generation (MEG) refers to the creation of two or more electron-hole pairs from the absorption of one photon. Although MEG holds great promise, it proved challenging to implement, and questions remain about the underlying photo-phys. dynamics in nanocryst. as well as mol. media. Using the model system of pentacene/fullerene bilayers and femtosecond nonlinear spectroscopies, the authors directly obsd. the multiexciton (ME) state ensuing from singlet fission (a mol. manifestation of MEG) in pentacene. Probably the state exists in coherent superposition with the singlet populated by optical excitation. Also multiple electron transfer from the ME state to the fullerene occurs on a subpicosecond time scale, which is one order of magnitude faster than that from the triplet exciton state.
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    26. 26
      Duan, H.-G.; Jha, A.; Li, X.; Tiwari, V.; Ye, H.; Nayak, P. K.; Zhu, X.-L.; Li, Z.; Martinez, T. J.; Thorwart, M. Intermolecular Vibrations Mediate Ultrafast Singlet Fission. Sci. Adv. 2020, 6 (38), eabb0052  DOI: 10.1126/sciadv.abb0052
      There is no corresponding record for this reference.
    27. 27
      Seiler, H.; Krynski, M.; Zahn, D.; Hammer, S.; Windsor, Y. W.; Vasileiadis, T.; Pflaum, J.; Ernstorfer, R.; Rossi, M.; Schwoerer, H. Nuclear Dynamics of Singlet Exciton Fission in Pentacene Single Crystals. Sci. Adv. 2021, 7 (26), eabg0869  DOI: 10.1126/sciadv.abg0869
      There is no corresponding record for this reference.
    28. 28
      Neef, A.; Beaulieu, S.; Hammer, S.; Dong, S.; Maklar, J.; Pincelli, T.; Xian, R. P.; Wolf, M.; Rettig, L.; Pflaum, J. Orbital-Resolved Observation of Singlet Fission. Nature 2023, 616 (7956), 275– 279,  DOI: 10.1038/s41586-023-05814-1
      There is no corresponding record for this reference.
    29. 29
      Kim, J.; Bain, D. C.; Ding, V.; Majumder, K.; Windemuller, D.; Feng, J.; Wu, J.; Patil, S.; Anthony, J.; Kim, W. Coherent photoexcitation of entangled triplet pair states. Nat. Chem. 2024, 16, 1680– 1686,  DOI: 10.1038/s41557-024-01556-3
      There is no corresponding record for this reference.
    30. 30
      Breuer, T.; Celik, M. A.; Jakob, P.; Tonner, R.; Witte, G. Vibrational Davydov Splittings and Collective Mode Polarizations in Oriented Organic Semiconductor Crystals. J. Phys. Chem. C 2012, 116 (27), 14491– 14503,  DOI: 10.1021/jp304080g
      30
      Vibrational Davydov Splittings and Collective Mode Polarizations in Oriented Organic Semiconductor Crystals
      Breuer, Tobias; Celik, Mehmet A.; Jakob, Peter; Tonner, Ralf; Witte, Gregor
      Journal of Physical Chemistry C (2012), 116 (27), 14491-14503CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Vibrational properties of highly ordered cryst. perfluoropentacene (PFP) films epitaxially grown on KCl(100) and NaF(100) substrates were studied by transmission IR spectroscopy and d. functional theory. The different mol. orientations adopted by PFP on both substrates (standing vs. lying) and their epitaxial ordering enable precise polarization-resolved measurements along individual crystallog. directions and thus allow an unambiguous exptl. detn. of the polarization of the IR modes. Computations of the vibrational spectra beyond the single-mol. approxn. were employed at the periodic dispersion-cor. d. functional level (PBE-D2PBC) and compared with nonperiodic calcns. (PBE-D2/def2-TZVPP). Thereby, a detailed mode assignment based on vibrational energies and polarization information was attained. A microscopic explanation for the exptl. obsd. Davydov splitting of some modes and the IR inactivity of others was derived based on the mutual coupling of the dynamical dipole moments of the 2 mols. within the unit cell. Exptl. obsd. modes not covered by theor. anal. were identified as combination bands of IR-active modes coupled to totally sym. modes of similar displacement patterns. These findings have important implications for future studies on structure and charge transport in org. semiconductors and the validation of theor. approaches for the modeling of vibrational spectra.
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    31. 31
      Kolata, K.; Breuer, T.; Witte, G.; Chatterjee, S. Molecular Packing Determines Singlet Exciton Fission in Organic Semiconductors. ACS Nano 2014, 8 (7), 7377– 7383,  DOI: 10.1021/nn502544d
      31
      Molecular Packing Determines Singlet Exciton Fission in Organic Semiconductors
      Kolata, Kolja; Breuer, Tobias; Witte, Gregor; Chatterjee, Sangam
      ACS Nano (2014), 8 (7), 7377-7383CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
      Carrier multiplication by singlet exciton fission enhances photovoltaic conversion efficiencies in org. solids. This decay of 1 singlet exciton into 2 triplet states allows the extn. of ≤2 electrons per harvested photon and promises to overcome the Shockley-Queisser limit. The microscopic mechanism of singlet exciton fission, esp. the relation between mol. packing and electronic response, remains unclear, which therefore hampers the systematic improvement of org. photovoltaic devices. For the model system perfluoropentacene, exptl. singlet exciton fission is greatly enhanced for a slip-stacked mol. arrangement by addressing different crystal axes featuring different packing schemes. This reveals that the fission process strongly depends on the intermol. coupling: slip-stacking favors delocalization of excitations and allows for efficient exciton fission, while face-to-edge mol. orientations commonly found in the prevailing herringbone mol. stacking patterns even suppress it. The controversially debated role of excimer states as intermediary rather than competitive or precursory is clarified. The findings serve as a guideline for the design of next-generation mol. materials for application in future org. light-harvesting devices exploiting singlet exciton fission.
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    32. 32
      Fujii, K.; Himcinschi, C.; Toader, M.; Kera, S.; Zahn, D.; Ueno, N. Vibrational Properties of Perfluoropentacene Thin Film. J. Electron Spectrosc. Relat. Phenom. 2009, 174 (1–3), 65– 69,  DOI: 10.1016/j.elspec.2009.01.002
      There is no corresponding record for this reference.
    33. 33
      Salzmann, I.; Moser, A.; Oehzelt, M.; Breuer, T.; Feng, X. L.; Juang, Z. Y.; Nabok, D.; Della Valle, R. G.; Duhm, S.; Heimel, G. Epitaxial Growth of π-Stacked Perfluoropentacene on Graphene-Coated Quartz. ACS Nano 2012, 6 (12), 10874– 10883,  DOI: 10.1021/nn3042607
      33
      Epitaxial Growth of π-Stacked Perfluoropentacene on Graphene-Coated Quartz
      Salzmann, Ingo; Moser, Armin; Oehzelt, Martin; Breuer, Tobias; Feng, Xinliang; Juang, Zhen-Yu; Nabok, Dmitrii; Della Valle, Raffaele G.; Duhm, Steffen; Heimel, Georg; Brillante, Aldo; Venuti, Elisabetta; Bilotti, Ivano; Christodoulou, Christos; Frisch, Johannes; Puschnig, Peter; Draxl, Claudia; Witte, Gregor; Muellen, Klaus; Koch, Norbert
      ACS Nano (2012), 6 (12), 10874-10883CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
      Chem.-vapor-deposited large-area graphene is employed as the coating of transparent substrates for the growth of the prototypical org. n-type semiconductor perfluoropentacene (PFP). The graphene coating is found to cause face-on growth of PFP in a yet unknown substrate-mediated polymorph, which is solved by combining grazing-incidence X-ray diffraction with theor. structure modeling. In contrast to the otherwise common herringbone arrangement of PFP in single crystals and "standing" films, the authors report a π-stacked arrangement of coplanar mols. in "flat-lying" films, which exhibit an exceedingly low π-stacking distance of only 3.07 Å, giving rise to significant electronic band dispersion along the π-stacking direction, as evidenced by UPS. The study underlines the high potential of graphene for use as a transparent electrode in (opto-)electronic applications, where optimized vertical transport through flat-lying conjugated org. mols. is desired.
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    34. 34
      Zeiser, C.; Moretti, L.; Geiger, T.; Kalix, L.; Valencia, A. M.; Maiuri, M.; Cocchi, C.; Bettinger, H. F.; Cerullo, G.; Broch, K. Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene. J. Phys. Chem. Lett. 2021, 12 (31), 7453– 7458,  DOI: 10.1021/acs.jpclett.1c01805
      34
      Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene
      Zeiser, Clemens; Moretti, Luca; Geiger, Thomas; Kalix, Lukas; Valencia, Ana M.; Maiuri, Margherita; Cocchi, Caterina; Bettinger, Holger F.; Cerullo, Giulio; Broch, Katharina
      Journal of Physical Chemistry Letters (2021), 12 (31), 7453-7458CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Singlet fission (SF), the photophys. process in which 1 singlet exciton is transformed into 2 triplets, depends inter alia on the coupling of electronic states. Here, the authors use fluorination and the resulting changes in partial charge distribution across the chromophore backbone as a particularly powerful tool to control this parameter in pentacene. The introduction of a permanent dipole moment leads to an enhanced coupling of Frenkel exciton and charge transfer states and to an increased SF rate which the authors probed using ultrafast transient absorption spectroscopy. These findings are contrasted with H-aggregate formation and a significantly reduced triplet-pair state lifetime in a fluorinated pentacene for which the different partial charge distribution leads to a negligible dipole moment.
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    35. 35
      Sakamoto, Y.; Suzuki, T.; Kobayashi, M.; Gao, Y.; Fukai, Y.; Inoue, Y.; Sato, F.; Tokito, S. Perfluoropentacene: High-Performance P–N Junctions and Complementary Circuits with Pentacene. JACS. 2004, 126 (26), 8138– 8140,  DOI: 10.1021/ja0476258
      35
      Perfluoropentacene: High-Performance p-n Junctions and Complementary Circuits with Pentacene
      Sakamoto, Youichi; Suzuki, Toshiyasu; Kobayashi, Masafumi; Gao, Yuan; Fukai, Yasushi; Inoue, Youji; Sato, Fumio; Tokito, Shizuo
      Journal of the American Chemical Society (2004), 126 (26), 8138-8140CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The authors report the synthesis and characterization of perfluoropentacene as an n-type semiconductor for org. field-effect transistors (OFETs). Perfluoropentacene is a planar and cryst. material that adopts a herringbone structure as obsd. for pentacene. OFETs with perfluoropentacene were constructed using top-contact geometry, and an electron mobility of 0.11 cm2 V-1 s-1 was obsd. Bipolar OFETs with perfluoropentacene and pentacene function at both neg. and pos. gate voltages. The improved p-n junctions are probably due to the similar d-spacings of both acenes. Complementary inverter circuits were fabricated, and the transfer characteristics exhibit a sharp inversion of the output signal with a high-voltage gain.
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    36. 36
      Timmer, D.; Gittinger, M.; Quenzel, T.; Cadore, A. R.; Rosa, B. L. T.; Li, W. S.; Soavi, G.; Lünemann, D. C.; Stephan, S.; Silies, M. Ultrafast Coherent Exciton Couplings and Many-Body Interactions in Monolayer WS. Nano Lett. 2024, 24, 8117– 8125,  DOI: 10.1021/acs.nanolett.4c01991
      There is no corresponding record for this reference.
    37. 37
      Timmer, D.; Lünemann, D. C.; Riese, S.; Sio, A. D.; Lienau, C. Full Visible Range Two-Dimensional Electronic Spectroscopy with High Time Resolution. Opt. Express 2024, 32 (1), 835– 847,  DOI: 10.1364/OE.511906
      There is no corresponding record for this reference.
    38. 38
      Timmer, D.; Gittinger, M.; Quenzel, T.; Stephan, S.; Zhang, Y.; Schumacher, M. F.; Lützen, A.; Silies, M.; Tretiak, S.; Zhong, J.-H. Plasmon Mediated Coherent Population Oscillations in Molecular Aggregates. Nat. Commun. 2023, 14 (1), 8035,  DOI: 10.1038/s41467-023-43578-4
      There is no corresponding record for this reference.
    39. 39
      Quenzel, T.; Timmer, D.; Gittinger, M.; Zablocki, J.; Zheng, F. L.; Schiek, M.; Lutzen, A.; Frauenheim, T.; Tretiak, S.; Silies, M. Plasmon-Enhanced Exciton Delocalization in Squaraine-Type Molecular Aggregates. ACS Nano 2022, 16 (3), 4693– 4704,  DOI: 10.1021/acsnano.1c11398
      39
      Plasmon-Enhanced Exciton Delocalization in Squaraine-Type Molecular Aggregates
      Quenzel, Thomas; Timmer, Daniel; Gittinger, Moritz; Zablocki, Jennifer; Zheng, Fulu; Schiek, Manuela; Luetzen, Arne; Frauenheim, Thomas; Tretiak, Sergei; Silies, Martin; Zhong, Jin-Hui; De Sio, Antonietta; Lienau, Christoph
      ACS Nano (2022), 16 (3), 4693-4704CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)
      Enlarging exciton coherence lengths in mol. aggregates is crit. for enhancing the collective optical and transport properties of mol. thin film nanostructures or devices. We demonstrate that the exciton coherence length of squaraine aggregates can be increased from 10 to 24 mol. units at room temp. when prepg. the aggregated thin film on a metallic rather than a dielec. substrate. Two-dimensional electronic spectroscopy measurements reveal a much lower degree of inhomogeneous line broadening for aggregates on a gold film, pointing to a reduced disorder. The result is corroborated by simulations based on a Frenkel exciton model including exciton-plasmon coupling effects. The simulation shows that localized, energetically nearly resonant excitons on spatially well sepd. segments can be radiatively coupled via delocalized surface plasmon polariton modes at a planar mol.-gold interface. Such plasmon-enhanced delocalization of the exciton wave function is of high importance for improving the coherent transport properties of mol. aggregates on the nanoscale. Addnl., it may help tailor the collective optical response of org. materials for quantum optical applications.
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    40. 40
      Timmer, D.; Zheng, F.; Gittinger, M.; Quenzel, T.; Lünemann, D. C.; Winte, K.; Zhang, Y.; Madjet, M. E.; Zablocki, J.; Lützen, A. Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes. JACS. 2022, 144 (41), 19150– 19162,  DOI: 10.1021/jacs.2c08682
      There is no corresponding record for this reference.
    41. 41
      Breuer, T. Preparation and Characterization of Thin Films of Organic Semiconductors and their Heterostructures. Ph.D. Thesis, University of Marburg, Marburg, Germany, 2013.
      There is no corresponding record for this reference.
    42. 42
      Cocchi, C.; Breuer, T.; Witte, G.; Draxl, C. Polarized Absorbance and Davydov Splitting in Bulk and Thin-Film Pentacene Polymorphs. Phys. Chem. Chem. Phys. 2018, 20 (47), 29724– 29736,  DOI: 10.1039/C8CP06384B
      42
      Polarized absorbance and Davydov splitting in bulk and thin-film pentacene polymorphs
      Cocchi, Caterina; Breuer, Tobias; Witte, Gregor; Draxl, Claudia
      Physical Chemistry Chemical Physics (2018), 20 (47), 29724-29736CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Pentacene is one of the most studied org. materials and in particular its optical properties have been the subject of intense research during the last two decades. In spite of such a widespread interest and of the extensive knowledge achieved so far, a no. of issues are still debated. One of the most relevant questions concerns the role of polymorphism and how it affects the lowest-energy exciton, which appears in the visible region and is subject to a sizable Davydov splitting. We address this problem in a combined theor. and exptl. work, where the optical absorption properties of three pentacene polymorphs are investigated within the whole energy range of visible light. Optical spectra computed from first principles in the framework of many-body perturbation theory are directly compared with the polarization-resolved absorbance, measured for three different pentacene phases (the two bulk polymorphs and the thin-film phase). In this way, we unambiguously identify the two Davydov components of the first exciton and the optical fingerprints of each considered phase. With very good agreement between theory and expt., we show that all polymorphs exhibit common features at the absorption onset, while phase-dependent characteristics appear only above 2 eV. We discuss the character of the lowest-lying singlet and triplet excitons, including dark ones, highlighting the contributions from the electronic bands and the role of the electron-hole interaction and of the local-field effects.
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    43. 43
      Kumar, A. T. N.; Rosca, F.; Widom, A.; Champion, P. M. Investigations of Amplitude and Phase Excitation Profiles in Femtosecond Coherence Spectroscopy. J. Chem. Phys. 2001, 114 (2), 701– 724,  DOI: 10.1063/1.1329640
      43
      Investigations of amplitude and phase excitation profiles in femtosecond coherence spectroscopy
      Kumar, Anand T. N.; Rosca, Florin; Widom, Allan; Champion, Paul M.
      Journal of Chemical Physics (2001), 114 (2), 701-724CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      We present an effective linear response approach to pump-probe femtosecond coherence spectroscopy in the well-sepd. pulse limit. The treatment presented here is based on a displaced and squeezed state representation for the nonstationary states induced by an ultrashort pump laser pulse or a chem. reaction. The subsequent response of the system to a delayed probe pulse is modeled using closed form nonstationary linear response functions, valid for a multimode vibronically coupled system at arbitrary temp. When pump-probe signals are simulated using the linear response functions, with the mean nuclear positions and momenta obtained from a rigorous moment anal. of the pump induced (doorway) state, the signals are found to be in excellent agreement with the conventional third-order response approach. The key advantages offered by the moment anal.-based linear response approach include a clear phys. interpretation of the amplitude and phase of oscillatory pump-probe signals, a dramatic improvement in computation times, a direct connection between pump-probe signals and equil. absorption and dispersion lineshapes, and the ability to incorporate coherence assocd. with rapid nonradiative surface crossing. We demonstrate these aspects using numerical simulations, and also apply the present approach to the interpretation of exptl. amplitude and phase measurements on reactive and nonreactive samples of the heme protein myoglobin. The role played by inhomogeneous broadening in the obsd. amplitude and phase profiles is discussed in detail. We also investigate overtone signals in the context of reaction driven coherent motion.
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    44. 44
      Nguyen, X. T.; Winte, K.; Timmer, D.; Rakita, Y.; Ceratti, D. R.; Aharon, S.; Ramzan, M. S.; Cocchi, C.; Lorke, M.; Jahnke, F. Phonon-Driven Intra-Exciton Rabi Oscillations in CsPbBr3 Halide Perovskites. Nat. Commun. 2023, 14 (1), 1047,  DOI: 10.1038/s41467-023-36654-2
      44
      Phonon-driven intra-exciton Rabi oscillations in CsPbBr3 halide perovskites
      Nguyen, Xuan Trung; Winte, Katrin; Timmer, Daniel; Rakita, Yevgeny; Ceratti, Davide Raffaele; Aharon, Sigalit; Ramzan, Muhammad Sufyan; Cocchi, Caterina; Lorke, Michael; Jahnke, Frank; Cahen, David; Lienau, Christoph; De Sio, Antonietta
      Nature Communications (2023), 14 (1), 1047CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)
      Coupling electromagnetic radiation with matter, e.g., by resonant light fields in external optical cavities, is highly promising for tailoring the optoelectronic properties of functional materials on the nanoscale. Here, we demonstrate that even internal fields induced by coherent lattice motions can be used to control the transient excitonic optical response in CsPbBr3 halide perovskite crystals. Upon resonant photoexcitation, two-dimensional electronic spectroscopy reveals an excitonic peak structure oscillating persistently with a 100-fs period for up to ≈2 ps which does not match the frequency of any phonon modes of the crystals. Only at later times, beyond 2 ps, two low-frequency phonons of the lead-bromide lattice dominate the dynamics. We rationalize these findings by an unusual exciton-phonon coupling inducing off-resonant 100-fs Rabi oscillations between 1s and 2p excitons driven by the low-frequency phonons. As such, prevailing models for the electron-phonon coupling in halide perovskites are insufficient to explain these results. We propose the coupling of characteristic low-frequency phonon fields to intra-excitonic transitions in halide perovskites as the key to control the anharmonic response of these materials in order to establish new routes for enhancing their optoelectronic properties.
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    45. 45
      Polli, D.; Antognazza, M. R.; Brida, D.; Lanzani, G.; Cerullo, G.; De Silvestri, S. Broadband Pump-Probe Spectroscopy with Sub-10-fs Resolution for Probing Ultrafast Internal Conversion and Coherent Phonons in Carotenoids. Chem. Phys. 2008, 350 (1–3), 45– 55,  DOI: 10.1016/j.chemphys.2007.12.021
      There is no corresponding record for this reference.
    46. 46
      Andrzejak, M.; Mazur, G.; Musser, A. J.; Petelenz, P.; Skóra, T. Properties of Coherent Vibrational Wavepackets Critically Depend on the Method of Their Generation. J. Phys. Chem. C 2024, 128 (24), 9837– 9846,  DOI: 10.1021/acs.jpcc.4c01485
      There is no corresponding record for this reference.
    47. 47
      Albrecht, A. C. Theory of Raman Intensities. J. Chem. Phys. 1961, 34 (5), 1476– 1484,  DOI: 10.1063/1.1701032
      There is no corresponding record for this reference.
    48. 48
      Ruhman, S.; Joly, A. G.; Nelson, K. A. Coherent Molecular Vibrational Motion Observed in the Time Domain Through Impulsive Stimulated Raman-Scattering. IEEE J. Quantum Electron. 1988, 24 (2), 460– 469,  DOI: 10.1109/3.146
      There is no corresponding record for this reference.
    49. 49
      Banin, U.; Bartana, A.; Ruhman, S.; Kosloff, R. Impulsive Excitation of Coherent Vibrational Motion Ground Surface Dynamics Induced by Intense Short Pulses. J. Chem. Phys. 1994, 101 (10), 8461– 8481,  DOI: 10.1063/1.468108
      49
      Impulsive excitation of coherent vibrational motion ground surface dynamics induced by intense short pulses
      Banin, Uri; Bartana, Allon; Ruhman, Sanford; Kosloff, Ronnie
      Journal of Chemical Physics (1994), 101 (10), 8461-81CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      A framework for understanding impulsively photoinduced vibrational coherent motion on the ground electronic surface is presented. In particular strong resonant excitation to a directly dissociative electronic surface is considered. Three distinct approaches are employed. A two surface Fourier wavepacket method explicitly including the field explores this process in isolated mols. A coordinate dependent two-level system is employed to develop a novel anal. approx. to the photoinduced quantum dynamics. The negligible computational requirements make it a powerful interactive tool for reconstructing the impulsive photoexcitation stage. Its anal. nature provides closed from expressions for the photoinduced changes in the material. Finally the full simulation of the process including the solvent effects is carried out by a numerical propagation of the d. operator. In all three techniques the excitation field is treated to all orders, allowing an anal. of current expts. using strong fields, resulting in substantial photoconversion. The emerging picture is that the impulsive excitation carves a coherent dynamic "hole" out of the ground surface d. A rigorous definition of the dynamic "hole" is constructed and used to define a measure of its coherence. In particular all photoinduced time dependence in the system can be directly related to the dynamic "hole". All three techniques are used to simulate the pump probe expt. on the sym. stretch mode of I3-3, including electronic and vibrational dephasing.
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    50. 50
      Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P. Principles and Applications of Broadband Impulsive Vibrational Spectroscopy. J. Phys. Chem. A 2015, 119, 9506,  DOI: 10.1021/acs.jpca.5b05948
      50
      Principles and Applications of Broadband Impulsive Vibrational Spectroscopy
      Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P.
      Journal of Physical Chemistry A (2015), 119 (36), 9506-9517CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      An exptl. setup is presented for recording vibrational coherences and Raman spectra of mols. in their ground and excited electronic states at 50-3000 cm-1 using broadband impulsive vibrational spectroscopy. The approach relies on the combination of a <10 fs excitation pulse with an uncompressed white light continuum probe, which drastically reduces exptl. complexity compared to frequency domain based techniques. The parameters detg. vibrational coherence amplitudes, outline how to optimize the exptl. setup including approaches aimed at conclusively assigning vibrational coherences to specific electronic states, and provide a clear comparison with existing techniques are discussed. To demonstrate the applicability of the spectroscopic approach, several examples reveal the evolution of vibrational coherence in rhodopsin and β-carotene.
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    51. 51
      Rather, S. R.; Fu, B.; Kudisch, B.; Scholes, G. D. Interplay of Vibrational Wavepackets during an Ultrafast Electron Transfer Reaction. Nat. Chem. 2021, 13 (1), 70– 76,  DOI: 10.1038/s41557-020-00607-9
      There is no corresponding record for this reference.
    52. 52
      Liebel, M.; Schnedermann, C.; Kukura, P. Vibrationally Coherent Crossing and Coupling of Electronic States during Internal Conversion in β-Carotene. Phys. Rev. Lett. 2014, 112 (19), 198302,  DOI: 10.1103/PhysRevLett.112.198302
      52
      Vibrationally coherent crossing and coupling of electronic states during internal conversion in β-carotene
      Liebel, M.; Schnedermann, C.; Kukura, P.
      Physical Review Letters (2014), 112 (19), 198302/1-198302/5, 5 pp.CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      Coupling of nuclear and electronic degrees of freedom mediates energy flow in mols. after optical excitation. The assocd. coherent dynamics in polyat. systems, however, remain exptl. unexplored. Here, we combined transient absorption spectroscopy with electronic population control to reveal nuclear wave packet dynamics during the S2 → S1 internal conversion in β-carotene. We show that passage through a conical intersection is vibrationally coherent and thereby provides direct feedback on the role of different vibrational coordinates in the breakdown of the Born-Oppenheimer approxn.
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    53. 53
      Falke, S. M.; Rozzi, C. A.; Brida, D.; Maiuri, M.; Amato, M.; Sommer, E.; De Sio, A.; Rubio, A.; Cerullo, G.; Molinari, E. Coherent Ultrafast Charge Transfer in an Organic Photovoltaic Blend. Science 2014, 344 (6187), 1001– 1005,  DOI: 10.1126/science.1249771
      53
      Coherent ultrafast charge transfer in an organic photovoltaic blend
      Falke, Sarah Maria; Rozzi, Carlo Andrea; Brida, Daniele; Maiuri, Margherita; Amato, Michele; Sommer, Ephraim; De Sio, Antonietta; Rubio, Angel; Cerullo, Giulio; Molinari, Elisa; Lienau, Christoph
      Science (Washington, DC, United States) (2014), 344 (6187), 1001-1005CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      Blends of conjugated polymers and fullerene derivs. are prototype systems for org. photovoltaic devices. The primary charge-generation mechanism involves a light-induced ultrafast electron transfer from the light-absorbing and electron-donating polymer to the fullerene electron acceptor. Here, the authors elucidate the initial quantum dynamics of this process. Exptl., the authors obsd. coherent vibrational motion of the fullerene moiety after impulsive optical excitation of the polymer donor. Comparison with 1st-principle theor. simulations evidences coherent electron transfer between donor and acceptor and oscillations of the transferred charge with a 25-fs period matching that of the obsd. vibrational modes. The authors' results show that coherent vibronic coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer in a noncovalently bound ref. system.
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    54. 54
      Orlandi, G.; Siebrand, W. Theory of Vibronic Intensity Borrowing - Comparison of Herzberg-Teller and Born-Oppenheimer Coupling. J. Chem. Phys. 1973, 58 (10), 4513– 4523,  DOI: 10.1063/1.1679014
      There is no corresponding record for this reference.
    55. 55
      Avila Ferrer, F. J.; Barone, V.; Cappelli, C.; Santoro, F. Duschinsky, Herzberg-Teller, and Multiple Electronic Resonance Interferential Effects in Resonance Raman Spectra and Excitation Profiles. The Case of Pyrene. J. Chem. Theory. Comput. 2013, 9 (8), 3597– 3611,  DOI: 10.1021/ct400197y
      55
      Duschinsky, Herzberg-Teller, and Multiple Electronic Resonance Interferential Effects in Resonance Raman Spectra and Excitation Profiles. The Case of Pyrene
      Avila Ferrer, Francisco J.; Barone, Vincenzo; Cappelli, Chiara; Santoro, Fabrizio
      Journal of Chemical Theory and Computation (2013), 9 (8), 3597-3611CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)
      A recently developed time-independent approach for the calcn. of vibrational resonance Raman (vRR) spectra is able to describe Duschinsky and Herzberg-Teller (HT) effects acting on a single resonant state, together with interferential contributions arising from multiple electronic resonances, allowing one to study in detail how their interplay dets. both the vRR spectra at selected wavelengths and the Raman excitation profiles. The authors apply this methodol. to the study of the spectra of pyrene in MeCN, an ideal system since it exhibits 3 close-lying electronic transitions that are bright but also subjected to HT effects. To single out the different contributions to vRR line shapes the authors adopted 2 different adiabatic models for resonant-state potential energy surfaces, namely, Adiabatic Shift (only accounting from equil. geometry displacements) and Adiabatic Hessian (AH, including also the Duschinsky effects), and Franck-Condon (FC) or HT approxns. for the transition dipole. On balance, FC+HT calcns. within the AH model provide the best agreement with expt. Also, the methodol. permits to individuate bands in the exptl. spectra due to the simultaneous contribution of >1 resonant state and to point out and analyze interferential effects between the FC and HT terms in each resonance Raman process, together with FC-HT and HT-HT interferences between different electronic states.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXpsFGmtb0%253D&md5=4f68741ea896d01b5efffe08c008b3ae
    56. 56
      Petelenz, P.; Andrzejak, M. Vibronic Interpretation of the Low-Energy Absorption Spectrum of the Sexithiophene Single Crystal. J. Chem. Phys. 2000, 113 (24), 11306– 11314,  DOI: 10.1063/1.1290026
      There is no corresponding record for this reference.
    57. 57
      Witkowski, A.; Moffitt, W. Electronic Spectra of Dimers - Derivation of the Fundamental Vibronic Equations. J. Chem. Phys. 1960, 33 (3), 872– 875,  DOI: 10.1063/1.1731278
      There is no corresponding record for this reference.
    58. 58
      Zgierski, M. Z.; Pawlikowski, M. Absorption and Circular-Dichroism Spectra of Dimeric Systems - Extended Dimer Model. J. Chem. Phys. 1983, 79 (4), 1616– 1633,  DOI: 10.1063/1.446033
      There is no corresponding record for this reference.
    59. 59
      Bizimana, L. A.; Carbery, W. P.; Gellen, T. A.; Turner, D. B. Signatures of Herzberg-Teller Coupling in Three-Dimensional Electronic Spectroscopy. J. Chem. Phys. 2017, 146 (8), 084311,  DOI: 10.1063/1.4976995
      There is no corresponding record for this reference.
    60. 60
      Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77 (18), 3865– 3868,  DOI: 10.1103/PhysRevLett.77.3865
      60
      Generalized gradient approximation made simple
      Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
      Physical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XmsVCgsbs%253D&md5=55943538406ee74f93aabdf882cd4630
    61. 61
      Günder, D.; Valencia, A. M.; Guerrini, M.; Breuer, T.; Cocchi, C.; Witte, G. Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN: PFP Cocrystalline Films: Limits of Nonperiodic Modeling. J. Phys. Chem. Lett. 2021, 12 (40), 9899– 9905,  DOI: 10.1021/acs.jpclett.1c02761
      There is no corresponding record for this reference.
    62. 62
      Valencia, A. M.; Bischof, D.; Anhäuser, S.; Zeplichal, M.; Terfort, A.; Witte, G.; Cocchi, C. Excitons in Organic Materials: Revisiting Old Concepts with New Insights. Electron. Struct. 2023, 5 (3), 033003,  DOI: 10.1088/2516-1075/acf2d4
      There is no corresponding record for this reference.
    63. 63
      Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P. Principles and Applications of Broadband Impulsive Vibrational Spectroscopy. J. Phys. Chem. A 2015, 119 (36), 9506– 9517,  DOI: 10.1021/acs.jpca.5b05948
      63
      Principles and Applications of Broadband Impulsive Vibrational Spectroscopy
      Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P.
      Journal of Physical Chemistry A (2015), 119 (36), 9506-9517CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      An exptl. setup is presented for recording vibrational coherences and Raman spectra of mols. in their ground and excited electronic states at 50-3000 cm-1 using broadband impulsive vibrational spectroscopy. The approach relies on the combination of a <10 fs excitation pulse with an uncompressed white light continuum probe, which drastically reduces exptl. complexity compared to frequency domain based techniques. The parameters detg. vibrational coherence amplitudes, outline how to optimize the exptl. setup including approaches aimed at conclusively assigning vibrational coherences to specific electronic states, and provide a clear comparison with existing techniques are discussed. To demonstrate the applicability of the spectroscopic approach, several examples reveal the evolution of vibrational coherence in rhodopsin and β-carotene.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlSmt7rJ&md5=0099060f0280493b160d6570da65c8de
    64. 64
      Lanzani, G.; Cerullo, G.; De Silvestri, S. Coherent Vibrational Dynamics; CRC Press, 2007.
      There is no corresponding record for this reference.
    65. 65
      Grupp, A.; Budweg, A.; Fischer, M. P.; Allerbeck, J.; Soavi, G.; Leitenstorfer, A.; Brida, D. Broadly Tunable Ultrafast Pump-Probe System Operating at Multi-kHz Repetition Rate. J. Opt. 2018, 20 (1), 014005,  DOI: 10.1088/2040-8986/aa9b07
      There is no corresponding record for this reference.
    66. 66
      Brida, D.; Manzoni, C.; Cerullo, G. Phase-Locked Pulses for Two-Dimensional Spectroscopy by a Birefringent Delay Line. Opt. Lett. 2012, 37 (15), 3027– 3029,  DOI: 10.1364/OL.37.003027
      66
      Phase-locked pulses for two-dimensional spectroscopy by a birefringent delay line
      Brida Daniele; Manzoni Cristian; Cerullo Giulio
      Optics letters (2012), 37 (15), 3027-9 ISSN:.
      We introduce the translating wedge-based identical pulses encoding system, a novel device for the generation of collinear, interferometrically locked ultrashort pulse pairs. By means of birefringent wedges, we are able to control the pulse delay with attosecond precision and stability better that λ/360, without affecting the pulse duration and in a spectral range that spans from UV to mid-IR. This device is expected to dramatically simplify two-dimensional spectroscopy experiments.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC38flt1Sqsg%253D%253D&md5=774e1891ccbfb9f8581dab50436ee22e
    67. 67
      Frisch, M. e.; Trucks, G.; Schlegel, H. B.; Scuseria, G.; Robb, M.; Cheeseman, J.; Scalmani, G.; Barone, V.; Petersson, G.; Nakatsuji, H. Gaussian 16; Gaussian, Inc.: Wallingford, CT, 2016.
      There is no corresponding record for this reference.
    68. 68
      Lee, S. Y.; Heller, E. J. Time-Dependent Theory of Raman Scattering. J. Chem. Phys. 1979, 71 (12), 4777– 4788,  DOI: 10.1063/1.438316
      68
      Time-dependent theory of Raman scattering
      Lee, Soo-Y.; Heller, E. J.
      Journal of Chemical Physics (1979), 71 (12), 4777-88CODEN: JCPSA6; ISSN:0021-9606.
      A time-dependent picture of vibrational Raman scattering in the weak field limit is presented. From this viewpoint the static effects, due to the coordinate dependence of the electronic transition dipole, can be sepd. from the dynamic effects that arise from wave packet propagation on the Born-Oppenheimer surfaces. Away from resonance, the energy uncertainty relation gives the propagation time necessary to obtain the cross section as being inversely proportional to the mismatch of the excitation frequency with the excited surface. The wave packet, given by the initial vibrational wave function times the transition dipole, hardly moves on the excited surface when the excitation frequency is far from resonance. As the excitation frequency is tuned closer to resonance, the propagated wave packet samples a larger portion of the surface. By using the short time approxn. to the propagator, formulas were obtained for the cross section that are applicable for Raman scattering by polyatomics. The short time approxn. is expected to be good away from resonance independent of the nature of the surface, and also on resonance with a repulsive surface. For an attractive surface, the approxn. gives the av. resonant cross section useful in the case when the vibrational structures cannot be obsd.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3cXms12ltA%253D%253D&md5=4233d1d72a3c69c20cb74a9e7c27ef2a
    69. 69
      Porezag, D.; Pederson, M. R. Infrared Intensities and Raman-Scattering Activities Within Density-Functional Theory. Phys. Rev. B 1996, 54 (11), 7830,  DOI: 10.1103/PhysRevB.54.7830
      69
      Infrared intensities and Raman-scattering activities within density-functional theory
      Porezag, Dirk; Pederson, Mark R.
      Physical Review B: Condensed Matter (1996), 54 (11), 7830-7836CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)
      The computational complexity assocd. with the d.-functional-based detn. of IR intensities and nonresonant Raman scattering activities is the same as that required for vibrational modes. Further, the authors use extremely large basis sets to det. the intrinsic accuracy for calcg. such phenomena within the d.-functional theory. The authors present benchmark calcns. on CH4, H2O, C2H2, C2H4, and C2H6 within both the local-d. approxn. (LDA) and the generalized gradient approxn. (GGA). Tests of the reliability and numerical stability of the theor. scheme are presented. To obtain reliable results, appropriate polarization basis functions and well-converged wave functions are necessary. While most of the Raman spectra predicted by LDA agree very well with exptl. data, some of the IR intensities show substantial errors. The GGA functional overcomes most of these deficiencies, leading to an overall good agreement with expt.
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  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpclett.4c02711.

    • X-ray diffraction of PFP films on KCl and NaF; polarization-resolved UV/vis absorption spectra of single crystalline PFP islands on KCl and NaF; pulse characterization; fluence study; data analysis (PDF)

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