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LetterJanuary 9, 2020

Revealing Ultrafast Population Transfer between Nearly Degenerate Electronic States
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Pascal Heim
Pascal Heim
Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
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Sebastian Mai
Sebastian Mai
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria
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Bernhard Thaler
Bernhard Thaler
Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
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http://orcid.org/0000-0001-5412-1519
Stefan Cesnik
Stefan Cesnik
Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
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Davide Avagliano
Davide Avagliano
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria
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Dimitra Bella-Velidou
Dimitra Bella-Velidou
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria
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Wolfgang E. Ernst
Wolfgang E. Ernst
Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
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http://orcid.org/0000-0001-8849-5658
Leticia González*
Leticia González
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria
*Email: [email protected]
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http://orcid.org/0000-0001-5112-794X
Markus Koch*
Markus Koch
Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
*Email: [email protected]
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http://orcid.org/0000-0003-0186-1614

Open PDF Supporting Information (3)

The Journal of Physical Chemistry Letters

Cite this: J. Phys. Chem. Lett. 2020, 11, 4, 1443–1449

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https://doi.org/10.1021/acs.jpclett.9b03462

Published January 9, 2020

Abstract

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The response of a molecule to photoexcitation is governed by the coupling of its electronic states. However, if the energetic spacing between the electronically excited states at the Franck–Condon window becomes sufficiently small, it is infeasible to selectively excite and monitor individual states with conventional time-resolved spectroscopy, preventing insight into the energy transfer and relaxation dynamics of the molecule. Here, we demonstrate how the combination of time-resolved spectroscopy and extensive surface hopping dynamics simulations with a global fit approach on individually excited ensembles overcomes this limitation and resolves the dynamics in the n3p Rydberg states in acetone. Photoelectron transients of the three closely spaced states n3p_x, n3p_y, and n3p_z are used to validate the theoretical results, which in turn allow retrieving a comprehensive kinetic model describing the mutual interactions of these states for the first time.

Subjects

The mechanistic understanding of the initial processes in light-induced molecular excited-state dynamics is both of fundamental interest and essential for the development of various technological applications, for example efficient light-harvesting systems (1) or molecular machines. (2) The first steps of these dynamics, which proceed in the femto- to picosecond range, are often accompanied by nonadiabatic population transfer between the excited states and can therefore be observed in real time with ultrafast time-resolved spectroscopy. (3) Such spectroscopy, in conjunction with state-of-the-art excited-state computational chemistry methods has revealed general concepts for understanding excited-state interactions in molecules (4−7) by using static (8,9) as well as dynamic (10,11) approaches. Nevertheless, following the nonadiabatic dynamics of molecules becomes rather challenging when the energy differences between excited electronic states within the Franck–Condon window becomes small. Although in polyatomic molecules the density of states is generally large, the situation can be particularly demanding in transition metal complexes, (12,13) extended biomolecules, (14) or within the Rydberg manifolds of small molecules, where not only higher-lying states in the Rydberg series are close in energy, (15) but also occasionally low-lying states, (16) especially if they have the same principal quantum number (e.g., n3p_x, n3p_y, n3p_z). Spectroscopic observation of the dynamical behavior of the individual states is then often buried under the “averaged” population decay of all states within the particular energetic region. These experimental difficulties have two reasons. First, the energetic proximity of the states in combination with the spectral width of sufficiently short laser pulses does not allow exciting single electronic states, but rather creates a complex distribution of population in multiple states. Second, simple sequential or parallel decay models, which can be routinely applied in data analysis via global fitting routines in simpler situations, (17−20) cannot accommodate complex relaxation pathways and state mixing arising from multiple couplings. These two issues obscure the nonadiabatic processes occurring within a dense set of states, requiring specialized approaches to obtain a comprehensive mechanistic understanding of the energy transfer in certain molecules.

In this work, we demonstrate that the combination of time-resolved photoelectron spectroscopy (TRPES) (21,22) and surface hopping simulations with the SHARC method (11) is able to fully characterize the dynamics in the regime of multiple nearly degenerate electronic states. Specifically, we are resolving the population transfer dynamics in the n3p Rydberg manifold of the acetone molecule after two-photon excitation. The photophysical and photochemical processes involving acetone have been in the spotlight since the early days of femtochemistry, (23−25) with a recent renaissance (15,26−30) motivated by the importance of acetone as the simplest aliphatic ketone. The difficulty of resolving light-induced processes in acetone derives from its electronic structure, characterized by series of Rydberg states that are strongly coupled to valence states, with the consequence of complex nonadiabatic relaxation dynamics where the electronic population is cascading down the ladder of Rydberg states. (15,28,30−32) As shown schematically in Figure 1a, the n3p manifold, energetically located at the lower end of the Rydberg series, consists of the three states n3p_x (A₂, 7.34 eV), n3p_y (A₁, 7.40 eV), and n3p_z (B₂, 7.45 eV), (16) lying within about 100 meV in the Franck–Condon region of the ground state. This manifold of states was investigated in time-resolved experiments and is considered to play an important role in the population transfer to lower states. (26,27,29) The energetic proximity of the three n3p states leads to significant vibrational coupling and—together with the presence of symmetry-dependent couplings with the ππ* (A₁) valence state—a complex interaction among all these states. (33−37) As a consequence, the dynamics of the individual n3p states within this dense region has evaded detailed observation to date, despite the importance of the n3p manifold as the bottleneck for the radiationless deactivation pathways of the higher-lying Rydberg states.

Figure 1. (a) Schematic overview of the relevant potential energy surfaces of acetone excited states, including the n3p and ππ* states. (b) Basic kinetic model assumed for the nonadiabatic dynamics among the acetone n3p and ππ* states with the nine considered time constants.

Here, we solve this problem and follow the transient population of the acetone n3p Rydberg states after excitation in terms of the individual nonadiabatic transition time scales between the four most important states: n3p_x, n3p_y, n3p_z, and ππ*. We note here that it was previously shown in the literature (29,32) that also other dark states (nπ* and n3s) might be involved in the dynamics. Hence, in the kinetic model fits, our label “ππ*” collectively includes also those dark states, although the ππ*, nπ*, and n3s states are explicitly present in both the experiments and the simulations. The transition time scales between the four states are summarized in Figure 1b, which shows the six inter-Rydberg time constants (τ_xy, τ_yx, τ_xz, τ_zx, τ_yz, and τ_zy) and the three Rydberg decay time constants (τ_xπ, τ_yπ, and τ_zπ) considered here. We describe the population dynamics by the following system of differential equations representing a unimolecular first-order kinetic model:

(1)

where

is the vector containing the time-dependent state populations. The coupling matrix M contains the nine time constants:

(2)

and g(t)P⃗₀ is the source term that populates the states (containing the temporal profile of the laser excitation g(t) and a state-dependent prefactor P⃗₀). The main goal of our study is to assign the numeric values of the nine time constants and to investigate their dependence on the excitation energy. This task can be achieved only by a combination of experiment and simulation. The experiment can observe only “effective” time constants τ_m, which are related to the eigenvalues λ_m of the coupling matrix M by τ_m = λ_m^–1 (in the following, m enumerates the eigenvalues of M). These effective time constants correspond to the so-called decay associated spectra (DAS), (17−20) discussed in detail in section S1 in the Supporting Information. As we do not consider the decay of the ππ* state here, one eigenvalue of M is always zero (i.e., one effective time constant is infinite), leaving in principle three time constants that could be obtained from the experiment. In contrast, appropriate nonadiabatic dynamics simulations can directly access the electronic populations of each individual state, what allows obtaining all nine individual time constants from a suitable global fit. The effective time constants derived from the simulated coupling matrix can then be compared to the experimental ones to verify the accuracy of the simulations.

In the TRPES experiments, isolated acetone molecules are excited into the n3p manifold by two-photon pump excitation (320 to 336 nm) and the transient population is probed after a variable time delay via one-photon probe photoionization (402 nm). The time-resolved photoelectron spectrum (see section S2 in the Supporting Information for details on the energy calibration) for 333 nm excitation is exemplarily shown in Figure 2 (see section S3 in the Supporting Information for results at other excitation wavelengths). In the spectrum, the n3p_x, n3p_y and n3p_z states are observed as separated photoelectron bands. The photoelectron kinetic energies (probe photon energy plus state energy minus ionization potential, see section S2 in the Supporting Information) of the three bands are centered at approximately 0.75, 0.80, and 0.84 eV, respectively. The narrow Franck–Condon envelope of the three bands indicates Rydberg state ionization to the ionic ground state with a Δν = 0 propensity rule. The n3p_y and n3p_z states are simultaneously populated at t = 0 fs and show similar signal increase and decrease. In contrast, the n3p_x signal behaves differently, building up later and decreasing much more slowly.

Figure 2. Overview of the experimental results. Measured transient photoelectron spectra (a), the 2D global fit of the spectrum (b) with corresponding DAS (c) for 333 nm pump wavelength (E_exc = 7.44 eV). Panel d shows the time constant dependence over excitation energy, including three data points from Hüter and Temps. (27) The red lines in panels a and b indicate a change of the vertical axis scale. PE, photoelectron kinetic energy; E_exc, two-photon excitation energy.

We fit the measured photoelectron spectrum S(E, t) (Figure 2a) with a 2D global fit routine to the following function: (17−20)

(3)

where Θ(t) is the Heaviside step function; τ_m = λ_m^–1 are the effective time constants, and DAS_m(E) are the decay-associated spectra (see section S1 in the Supporting Information). By varying the number of decay-associated spectra and time constants contained in the global fit, we find that m = {1, 2} (fit shown in Figure 2b) is sufficient and m = {1, 2, 3} does not increase the fit quality. This finding reflects the apparent similarity of the n3p_y and n3p_z transient signals. Hence, it appears that two of the three relevant effective time constants are very similar and that two time constants are sufficient to describe the time-resolved photoelectron spectrum. The two corresponding DAS (Figure 2c) confirm that n3p_y and n3p_z behave very similar, as given by the two peaks of the DAS corresponding to τ₂. Consequently, we can assign the larger constant τ₁ to the decay of n3p_x and the smaller constant τ₂ to the parallel decay of the n3p_y and n3p_z states. Unfortunately, the DAS does not allow uncovering more details of the complex population transfer between the different n3p states other than a population transfer from n3p_y and n3p_z to n3p_x, which is indicated by the negative DAS amplitude of the fast time constant.

The dependence of the effective time constants on the excitation energy is plotted in Figure 2d. Whereas τ₂ seems to remain constant at about 150 fs, τ₁ is strongly energy-dependent and decreases from about 1800 to 700 fs upon increasing the pump energy. At the highest excitation energy (7.75 eV), our values of τ₁ show very good agreement with the results of Hüter and Temps. (27) Moreover, time constants reported by these authors for higher energies show a consistent behavior in the energy dependence. Unfortunately, their energy resolution did not allow separating the different n3p states, so that they did not report decay constants that could be compared to our τ₂ values.

As the experiment cannot obtain the individual matrix elements of M, we performed nonadiabatic dynamics simulations using the surface hopping approach SHARC. (11,38) The potential energy surfaces were described employing a linear vibronic coupling (LVC) model (39) composed of 49 diabatic electronic states, including all states from the S₀ ground state to the ππ* state, which is the S₄₈ at the Franck–Condon geometry. We propagated (see section S4 in the Supporting Information) three independent ensembles of about 1000 trajectories each, in which the initial electronic wave function was the pure n3p_x, n3p_y, or n3p_z state. For each ensemble we monitored the population of the n3p_x, n3p_y, n3p_z, and ππ* states, resulting in a set of 12 population transients. This strategy of simulating the decay of each initial state separately is essential, because there are nine independent time constants to fit and employing only four population transients (from a single ensemble) would lead to severe overfitting.

Fitted population transients are presented in Figure 3. Panels a–c show the temporal evolution of the 12 population transients together with the fitting functions; the kinetic model fits the data excellently, with almost no systematic deviations. The obtained time constants, which are shown in Figure 3d together with their error estimates (obtained by bootstrapping), are quite interesting for the following three reasons: (i) The six inter-Rydberg time constants are relatively similar, with all constants ranging from 390 to 530 fs except τ_xy (700 fs). (ii) Population transfer toward energetically lower states proceeds faster (τ_zx, τ_zy, and τ_yx) than vice versa (τ_xz, τ_yz, and τ_xy). (iii) According to the three Rydberg decay constants, the n3p_y state decays the fastest among the n3p states (5 and 13 times faster than n3p_z and n3p_x, respectively), as previously suggested in the literature. (33−37) The time constants for the n3p_z and n3p_x states have large errors because the simulation time (1000 fs) is smaller than these estimated time constants. Especially the time constant for n3p_x is extremely large and imprecise, which indicates that this time constant is not necessary to describe the population transients. As expected, the fastest decay occurs from the n3p_y state to the ππ* state, because both states have the same symmetry (A₁) and it is sufficient to accumulate energy in one of the totally symmetric modes that lead to an avoided crossing of these states. This situation is different from the decay between states of different symmetry, which requires accumulated energy in at least two normal modes: a totally symmetric tuning mode that makes the diabatic energies equal and a nonsymmetric coupling mode of the correct irreducible representation that induces some coupling between two states. The requirement of two activated normal modes explains why all population transfer processes between states of different symmetry are slower than the same-symmetry n3p_y → ππ* transfer. In general, the magnitude of the time constants suggests that in acetone the n3p Rydberg states readily interconvert among each other because of their energetic closeness and the presence of coupling modes of all required symmetries.

Figure 3. Overview of the theoretical results obtained with the SHARC-LVC method. (a–c) Temporal evolution of the diabatic populations (thin lines) and kinetic model fits (thick lines), for the ensemble starting in (a) n3p_x, (b) n3p_y, and (c) n3p_z. (d) Scheme showing the fitted time constants and associated errors (see Figure S8 in section S4 in the Supporting Information for a similar fit enforcing detailed balance, showing that τ_xy might be overestimated and τ_xz underestimated but otherwise the time constants are consistent with detailed balance). (e) Plot of the energy dependence of the eigenvalue-derived effective time constants and comparison to the experimental and literature (27) values.

In order to obtain information about the energy dependence of the relaxation time constants, we group all trajectories into 11 subensembles based on their individual excitation energies. All fitted time constants are presented in section S5 in the Supporting Information. The energy intervals and the corresponding effective time constants obtained are shown in Figure 3e. The agreement of the energy dependence of the computed effective time constants with its experimental counterpart is very good. The simulated values shown in Figure 3e confirm that there is one strongly energy-dependent effective time constant (τ₁), being about 1600 fs for the lowest energies and about 500 fs for the highest ones. Additionally, there are two almost identical effective time constants (τ₂ and τ₃) in the range of approximately 80–200 fs, only weakly depending on energy.

In conclusion, we demonstrate how a combination of TRPES with extensive surface hopping simulations is able to reveal the details of nonadiabatic dynamics in energetically dense sets of states. Our synergistic approach allows disentangling the interconversion time scales among the three n3p states (n3p_x, n3p_y, and n3p_z) and the decay time scales to the dark ππ* state in acetone. This work constitutes the first study that resolves the highly nonsequential population flow among these nearly degenerate states. An important key of accessing the individual time constants was the simulation of multiple independent ensembles with complementary initial conditions, as otherwise the global fit is severely under-determined. Despite the known limitations of trajectory surface-hopping methods, (40−42) the results of the simulations—validated through their good agreement with the experimental effective time constants and energy dependence, see also a simulated TRPES spectrum in Figure S20 in the Supporting Information—show that the n3p_y is most strongly coupled to the ππ* state and exhibits the fastest decay, as expected from symmetry arguments. The n3p_y also acts as the gateway state for the deactivation of the n3p_x and n3p_z states, as indicated by the fact that the n3p_x/z→ n3p_y → ππ* route is faster than the direct n3p_x/z→ ππ* routes. The present results are expected to be helpful in understanding the light-driven dynamics of other aliphatic ketones and designing similar experiments. Further, they also evidence the power of using a linear vibronic coupling Hamiltonian within surface-hopping dynamics, as it allows considering large ensembles of trajectories propagating over a large number of electronic states.

Methods

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Experimental Methods. Pump–probe experiments were performed with femtosecond laser pulses from a commercial Ti:sapphire laser system with 800 nm central wavelength (for details, see ref (28)). Pump pulses were frequency up-converted by combining optical parametric amplification and subsequent frequency quadrupling to a wavelength range from 320 to 336 nm (6 nm, 15 meV full width at half-maximum, fwhm). Probe pulses of 402 nm (3 nm, 60 meV fwhm) were obtained by frequency doubling with a BBO crystal. Dichroic mirrors were used in both beam paths to remove undesired wavelengths from the up-conversion process. The laser pulses were focused into the extraction region of a 0.5 m long, linear magnetic bottle time-of-flight spectrometer (43) where a small retarding field was used to increase the electron kinetic energy resolution. High-purity acetone was introduced into the chamber as background gas with a partial pressure of about 4 × 10^–6 mbar.

Computational Methods. Potential energy surfaces of all electronic states of acetone were represented with a linear vibronic coupling (LVC) model (39,44) including all 24 vibrational degrees of freedom and 49 electronic states. This large number of states is necessary in order to include the important ππ* state at the reference geometry (S₄₈). The reference harmonic potential was obtained from an optimization plus frequency calculation for the n3s state at the SOS-ADC(2) level of theory. (45) Parameters for the description of the excited-state potentials were obtained from calculations at the same level of theory. The basis set was a combination of cc-pVTZ (46) for C and O, cc-pVDZ (46) for H, and an additional 10s8p6d4f Rydberg basis set (47) at O. All electronic structure calculations were carried out with Turbomole 7.0. (48)

Initial conditions were sampled from the Wigner distribution of the SOS-ADC(2) harmonic oscillator of the ground state, generating 1000 initial geometries and velocities. Three independent sets of trajectories were simulated from these, starting in the n3p_x, n3p_y, or n3p_z diabatic state. The trajectories were propagated with SHARC2.0 (11,38) for 1000 fs using a 0.5 fs time step; the electronic coefficients were propagated with a 0.02 fs step using the local diabatization approach. (49) We applied an energy-based decoherence correction (50) and rescaled the full momentum vector during a hop.

The results were analyzed in terms of the diabatic state populations, to which the kinetic model was fitted. Additional analysis was carried out by dividing the set of trajectories into different energy windows and fitting their populations independently.

See the Supporting Information for additional computational details.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpclett.9b03462.

Discussion and derivation of the fitting functions, experimental details regarding energy calibration, additional experimental results, additional computational details, and computational results (PDF)
V₀ data in SHARC format (TXT)
LVC parameters in SHARC format (TXT)

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Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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Corresponding Authors
- Leticia González - Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria; http://orcid.org/0000-0001-5112-794X; Email: [email protected]
- Markus Koch - Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria; http://orcid.org/0000-0003-0186-1614; Email: [email protected]
Authors
- Pascal Heim - Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
- Sebastian Mai - Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria; Present Address: S.M.: Vienna University of Technology, Vienna, Austria
- Bernhard Thaler - Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria; http://orcid.org/0000-0001-5412-1519
- Stefan Cesnik - Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria
- Davide Avagliano - Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria
- Dimitra Bella-Velidou - Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria
- Wolfgang E. Ernst - Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria; http://orcid.org/0000-0001-8849-5658
Author Contributions
P.H. and S.M. contributed equally to this work.
Notes
The authors declare no competing financial interest.

Acknowledgments

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P.H., B.T., S.C., W.E.E., and M.K. thank the Austrian Science Fund (FWF) for Grant P29369-N36 and NAWI Graz for financial support. S.M., D.A., and L.G. thank the FWF (Grant I2883) and the University of Vienna for financial support. The authors also thank the European Cost Action Attosecond Chemistry (CA18222). The presented calculations were partly carried out at the Vienna Scientific Cluster (VSC3).

References

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Schuurman, Michael S.; Stolow, Albert
Annual Review of Physical Chemistry (2018), 69 (), 427-450CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews)
A review. The nonadiabatic coupling of electronic and vibrational degrees of freedom is the defining feature of electronically excited states of polyat. mols. Once considered a theor. curiosity, conical intersections (CIs) are now generally accepted as being the dominant source of coupled charge and vibrational energy flow in mol. excited states. Passage through CIs leads to the conversion of electronic to vibrational energy, which drives the ensuing photochem., isomerization being a canonical example. It has often been remarked that the CI may be thought of as a transition state in the excited state. As such, we expect that both the direction and the velocity of approach to the CI will matter. We explore this suggestion by looking for dynamical aspects of passage through CIs and for analogies with well-known concepts from ground-state reaction dynamics. Great progress has been made in the development of both exptl. techniques and ab initio dynamics simulations, to a degree that direct comparisons may now be made. Here we compare time-resolved photoelectron spectroscopy results with on-the-fly ab initio multiple spawning calcns. of the exptl. observables, thereby validating each. We adopt a phenomenol. approach and specifically conc. on the excited-state dynamics of the C=C bond in unsatd. hydrocarbons. In particular, we make use of selective chem. substitution (such as replacing an H atom by a Me group) so as to alter the inertia of certain vibrations relative to others, thus systematically varying (mass-weighted) directions and velocities of approach to a CI. Chem. substituents, however, may affect both the nuclear and electronic components of the total wave function. The former, which we call an inertial effect, influences the direction and velocity of approach. The latter, which we call a potential effect, modifies the electronic structure and therefore the energetic location and topog. of the potential energy surfaces involved. Using a series of examples, we discuss both types of effects. We argue that there is a need for dynamical pictures and simple models of nonadiabatic dynamics at CIs and hope that the phenomenol. presented here will help inspire such developments.
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Timmers, H.; Zhu, X.; Li, Z.; Kobayashi, Y.; Sabbar, M.; Hollstein, M.; Reduzzi, M.; Martínez, T. J.; Neumark, D. M.; Leone, S. R. Disentangling conical intersection and coherent molecular dynamics in methyl bromide with attosecond transient absorption spectroscopy. Nat. Commun. 2019, 10, 3133, DOI: 10.1038/s41467-019-10789-7
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Disentangling conical intersection and coherent molecular dynamics in methyl bromide with attosecond transient absorption spectroscopy
Timmers Henry; Kobayashi Yuki; Sabbar Mazyar; Reduzzi Maurizio; Neumark Daniel M; Leone Stephen R; Zhu Xiaolei; Li Zheng; Martinez Todd J; Zhu Xiaolei; Li Zheng; Martinez Todd J; Li Zheng; Li Zheng; Hollstein Maximilian; Neumark Daniel M; Leone Stephen R; Leone Stephen R
Nature communications (2019), 10 (1), 3133 ISSN:.
Attosecond probing of core-level electronic transitions provides a sensitive tool for studying valence molecular dynamics with atomic, state, and charge specificity. In this report, we employ attosecond transient absorption spectroscopy to follow the valence dynamics of strong-field initiated processes in methyl bromide. By probing the 3d core-to-valence transition, we resolve the strong field excitation and ensuing fragmentation of the neutral σ* excited states of methyl bromide. The results provide a clear signature of the non-adiabatic passage of the excited state wavepacket through a conical intersection. We additionally observe competing, strong field initiated processes arising in both the ground state and ionized molecule corresponding to vibrational and spin-orbit motion, respectively. The demonstrated ability to resolve simultaneous dynamics with few-femtosecond resolution presents a clear path forward in the implementation of attosecond XUV spectroscopy as a general tool for probing competing and complex molecular phenomena with unmatched temporal resolution.
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Garavelli, M. Computational organic photochemistry: Strategy, achievements and perspectives. Theor. Chem. Acc. 2006, 116, 87– 105, DOI: 10.1007/s00214-005-0030-z
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Computational Organic Photochemistry: Strategy, Achievements and Perspectives
Garavelli, Marco
Theoretical Chemistry Accounts (2006), 116 (1-3), 87-105CODEN: TCACFW; ISSN:1432-881X. (Springer GmbH)
A review. In recent years, computational photochem. has achieved increasing consideration as a valid tool for the investigation of photochem. reaction mechanisms in org. chromophores. A theor. chemist can now adapt his/her "instruments" to the subject under investigation, as every other scientist does when there is a problem to study and a methodol. to be chosen. Thus, different computational strategies and tools can now be operated like a virtual spectrometer to characterize the photoinduced mol. deformation and reactivity of a given chromophore, so that a full description of the reactive process (i.e. its reaction coordinate) from energy absorption to photoproducts formation can be achieved. Here we will review the basic concepts, the computational strategy and the theor. tools, which permit this thorough description to be realized. Applications to the biol. and technol. relevant problem of photoinduced isomerizations in non-polar and highly polar conjugated polyenes will be shown, including also environment effects. Recent advances in this area (namely external charge effects) will be presented, together with new computational approaches, which allow mol. systems of biol. size (e.g. the rhodopsin photoreceptors) to be investigated at an unprecedented level of accuracy. This should open the way to the accurate investigation of sizable systems in realistic conditions, providing chemists with information that might be used in mol. technol. as a guideline for the design of artificial photoswitchable devices and the control of their photoinduced processes.
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Robb, M. A. Theoretical chemistry for electronic excited states; Theoretical and Computational Chemistry Series; The Royal Society of Chemistry, 2018; pp P001– 225.
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Lasorne, B.; Worth, G. A.; Robb, M. A. Excited-state dynamics. WIREs Comput. Mol. Sci. 2011, 1, 460– 475, DOI: 10.1002/wcms.26
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Excited-state dynamics
Lasorne, Benjamin; Worth, Graham A.; Robb, Michael A.
Wiley Interdisciplinary Reviews: Computational Molecular Science (2011), 1 (3), 460-475CODEN: WIRCAH; ISSN:1759-0884. (Wiley-Blackwell)
A review. Excited-state dynamics is the field of theor. and phys. chem. devoted to simulating mol. processes induced upon UV-visible light absorption. This involves nuclear dynamics methods to det. the time evolution of the mol. geometry used in concert with electronic structure methods capable of computing electronic excited-state potential energy surfaces. Applications concern photochem. (see Chapter CMS-030: Computational photochem.) and electronic spectroscopy. Most of the work in this field looks at unsatd. org. mols. as these provide widely used chromophores with a straightforward photochem. that can be described by a small no. (usually two) of electronic states. The electronic ground state of closed-shell org. mols. is a singlet (electronic spin zero) termed S0. Mols. are promoted to their electronic excited states through absorption of UV-visible light (200-700 nm), usually to the first or second singlet, S1 or S2. Typical examples are well represented as a one-electron transition from the π or n HOMO to a π* or σ* low-lying unoccupied MO. The photo-excited system will deactivate and return to the electronic ground state over a timescale that can be as short as about 100 fs for ultrafast mechanisms. For example, the initial event of vision is a photo-isomerization of the retinal chromophore in the rhodopsine protein that occurs in ca. 200 fs.1,2. The goal of a computational approach to the simulation of photo-induced processes is the complete description of what happens at the mol. level from the promotion to the excited electronic state to the formation of products or regeneration of reactants back in the electronic ground state.
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Mai, S.; Marquetand, P.; González, L. Nonadiabatic dynamics: The SHARC approach. WIREs Comput. Mol. Sci. 2018, 8, e1370, DOI: 10.1002/wcms.1370
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Chergui, M. On the interplay between charge, spin and structural dynamics in transition metal complexes. Dalton Trans 2012, 41, 13022– 13029, DOI: 10.1039/c2dt30764b
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On the interplay between charge, spin and structural dynamics in transition metal complexes
Chergui, Majed
Dalton Transactions (2012), 41 (42), 13022-13029CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)
A review. This perspective presents some recent results concerning ultrafast intramol. relaxation processes in metal-based mol. complexes. Ultrafast electronic/vibrational relaxation at sub-vibrational time scales, ultrafast intersystem crossing processes and ultrafast structure changes are discussed, stressing the questions that still need to be solved to arrive at a rationale that describes these processes. Some new techniques, based on core-level spectroscopies, can provide new insights into the ultrafast intramol. relaxation in these systems.
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Atkins, A. J.; González, L. Trajectory surface-hopping dynamics including intersystem crossing in [Ru(bpy)₃]²⁺. J. Phys. Chem. Lett. 2017, 8, 3840– 3845, DOI: 10.1021/acs.jpclett.7b01479
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Trajectory Surface-Hopping Dynamics Including Intersystem Crossing in [Ru(bpy)3]2+
Atkins, Andrew J.; Gonzalez, Leticia
Journal of Physical Chemistry Letters (2017), 8 (16), 3840-3845CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
Surface-hopping dynamics coupled to linear response TDDFT and explicit nonadiabatic and spin-orbit couplings have been used to model the ultrafast intersystem crossing (ISC) dynamics in [Ru(bpy)3]2+. Simulations using an ensemble of trajectories starting from the singlet metal-to-ligand charge transfer (1MLCT) band show that the manifold of 3MLCT triplet states is first populated from high-lying singlet states within 26 ± 3 fs. ISC competes with an intricate internal conversion relaxation process within the singlet manifold to the lowest singlet state. Normal-mode anal. and principal component anal., combined with further dynamical simulations where the nuclei are frozen, unequivocally demonstrate that it is not only the high d. of states and the large spin-orbit couplings of the system that promote ISC. Instead, geometrical relaxation involving the nitrogen atoms is required to allow for state mixing and efficient triplet population transfer.
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Nogueira, J. J.; Plasser, F.; González, L. Electronic delocalization, charge transfer and hypochromism in the UV absorption spectrum of polyadenine unravelled by multiscale computations and quantitative wavefunction analysis. Chem. Sci. 2017, 8, 5682– 5691, DOI: 10.1039/C7SC01600J
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Electronic delocalization, charge transfer and hypochromism in the UV absorption spectrum of polyadenine unravelled by multiscale computations and quantitative wavefunction analysis
Nogueira, Juan J.; Plasser, Felix; Gonzalez, Leticia
Chemical Science (2017), 8 (8), 5682-5691CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
The characterization of the electronically excited states of DNA strands populated upon solar UV light absorption is essential to unveil light-induced DNA damage and repair processes. We report a comprehensive anal. of the electronic properties of the UV spectrum of single-stranded polyadenine based on theor. calcns. that include excitations over eight nucleobases of the DNA strand and environmental effects by a multiscale quantum mechanics/mol. mechanics scheme, conformational sampling by mol. dynamics, and a meaningful interpretation of the electronic structure by quant. wavefunction anal. We show that electronic excitations are extended mainly over two nucleobases with addnl. important contributions of monomer-like excitations and excitons delocalized over three monomers. Half of the spectral intensity derives from locally excited and Frenkel exciton states, while states with partial charge-transfer character account for the other half and pure charge-transfer states represent only a minor contribution. The hypochromism obsd. when going from the isolated monomer to the strand occurs independently from delocalization and charge transfer and is instead explained by long-range environmental perturbations of the monomer states.
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Koch, M.; Thaler, B.; Heim, P.; Ernst, W. E. The role of Rydberg-valence coupling in the ultrafast relaxation dynamics of acetone. J. Phys. Chem. A 2017, 121, 6398– 6404, DOI: 10.1021/acs.jpca.7b05012
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The Role of Rydberg-Valence Coupling in the Ultrafast Relaxation Dynamics of Acetone
Koch, Markus; Thaler, Bernhard; Heim, Pascal; Ernst, Wolfgang E.
Journal of Physical Chemistry A (2017), 121 (34), 6398-6404CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
The electronic structure of excited states of acetone is represented by a Rydberg manifold that is coupled to valence states which provide very fast and efficient relaxation pathways. We observe and characterize the transfer of population from photoexcited Rydberg states (6p, 6d, 7s) to a whole series of lower Rydberg states (3p to 4d) and a simultaneous decay of population from these states. We obtain these results with time-resolved photoelectron-photoion coincidence (PEPICO) detection in combination with the application of Bayesian statistics for data anal. Despite the expectedly complex relaxation behavior, we find that a simple sequential decay model is able to describe the obsd. PEPICO transients satisfactorily. We obtain a slower decay (∼320 fs) from photoexcited states compared to a faster decay (∼100 fs) of states that are populated by internal conversion, demonstrating that different relaxation dynamics are active. Within the series of Rydberg states populated by internal conversion the decay dynamics seem to be similar, and a trend of slower decay from lower states indicates an increasingly higher energy barrier along the decay pathway for lower states. The presented results agree all in all with previous relaxation studies within the Rydberg manifold. The state-resolved observation of transient population ranging from 3p to 4d can serve as ref. for time-dependent simulations.
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Nobre, M.; Fernandes, A.; da Silva, F. F.; Antunes, R.; Almeida, D.; Kokhan, V.; Hoffmann, S. V.; Mason, N.; Eden, S.; Limão-Vieira, P. The VUV electronic spectroscopy of acetone studied by synchrotron radiation. Phys. Chem. Chem. Phys. 2008, 10, 550– 560, DOI: 10.1039/B708580J
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The VUV electronic spectroscopy of acetone studied by synchrotron radiation
Nobre, M.; Fernandes, A.; Ferreira da Silva, F.; Antunes, R.; Almeida, D.; Kokhan, V.; Hoffmann, S. V.; Mason, N. J.; Eden, S.; Limao-Vieira, P.
Physical Chemistry Chemical Physics (2008), 10 (4), 550-560CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
The electronic state spectroscopy of acetone Me2CO was studied using high-resoln. vacuum UV (VUV) photoabsorption spectroscopy at energies 3.7-10.8 eV. New vibronic structure was obsd., notably in the low energy absorption band assigned to the 11A1 → 11A2 (ny → π*) transition. The local absorption max. at 7.85 eV was tentatively attributed to the 41A1 (π → π*) transition. Six Rydberg series converging to the lowest ionization energy (9.708 eV) were assigned as well as a newly-resolved ns Rydberg series converging to the 1st ionic excited state (12.590 eV). Rydberg orbitals of each series were classified according to the magnitude of the quantum defect (δ) and are extended to higher quantum nos. than in the previous analyses.
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Holzapfel, W.; Finkele, U.; Kaiser, W.; Oesterhelt, D.; Scheer, H.; Stilz, H. U.; Zinth, W. Initial electron-transfer in the reaction center from Rhodobacter sphaeroides. Proc. Natl. Acad. Sci. U. S. A. 1990, 87, 5168– 5172, DOI: 10.1073/pnas.87.13.5168
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Initial electron transfer in the reaction center from Rhodobacter sphaeroides
Holzapfel, W.; Finkele, U.; Kaiser, W.; Oesterhelt, D.; Scheer, H.; Stilz, H. U.; Zinth, W.
Proceedings of the National Academy of Sciences of the United States of America (1990), 87 (13), 5168-72CODEN: PNASA6; ISSN:0027-8424.
The initial transfer steps in the photosynthetic reaction center of the purple bacterium R. sphaeroides have been investigated by fs time-resolved spectroscopy. The exptl. data taken at various wavelengths demonstrate the existence of at least 4 intermediate states within the first ns. The difference spectra of the intermediates and transient photodichlorism data are fully consistent with a sequential 4-step model of the primary electron transfer: light absorption by the special pair P leads to the state P*. From the excited primary donor P*, the electron is transferred within 3.5 ± 0.4 ps to the accessory bacteriochlorophyll B. State P+B- decays with a time const. of 0.9 ± 0.3 ps passing the electron to the bacteriopheophytin H. Finally, the electron is transferred from H- to the quinone QA within 220 ± 40 ps.
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van Stokkum, I. H.; Larsen, D. S.; van Grondelle, R. Global and target analysis of time-resolved spectra. Biochim. Biophys. Acta, Bioenerg. 2004, 1657, 82– 104, DOI: 10.1016/j.bbabio.2004.04.011
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Global and target analysis of time-resolved spectra
van Stokkum, Ivo H. M.; Larsen, Delmar S.; van Grondelle, Rienk
Biochimica et Biophysica Acta, Bioenergetics (2004), 1657 (2-3), 82-104CODEN: BBBEB4; ISSN:0005-2728. (Elsevier B.V.)
A review. In biol./bioenergetics research the response of a complex system to an externally applied perturbation is often studied. Spectroscopic measurements at multiple wavelengths are used to monitor the kinetics. These time-resolved spectra are considered as an example of multiway data. In this paper, the methodol. for global and target anal. of time-resolved spectra is reviewed. To fully ext. the information from the overwhelming amt. of data, a model-based anal. is mandatory. This anal. is based upon assumptions regarding the measurement process and upon a physicochem. model for the complex system. This model is composed of building blocks representing scientific knowledge and assumptions. Building blocks are the instrument response function (IRF), the components of the system connected in a kinetic scheme, and anisotropy properties of the components. The combination of a model for the kinetics and for the spectra of the components results in a more powerful spectrotemporal model. The model parameters, like rate consts. and spectra, can be estd. from the data, thus providing a concise description of the complex system dynamics. This spectrotemporal modeling approach is illustrated with an elaborate case study of the ultrafast dynamics of the photoactive yellow protein.
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Wu, G.; Boguslavskiy, A. E.; Schalk, O.; Schuurman, M. S.; Stolow, A. Ultrafast non-adiabatic dynamics of methyl substituted ethylenes: The π3s Rydberg state. J. Chem. Phys. 2011, 135, 164309, DOI: 10.1063/1.3652966
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Ultrafast non-adiabatic dynamics of methyl substituted ethylenes: The π3s Rydberg state
Wu, Guorong; Boguslavskiy, Andrey E.; Schalk, Oliver; Schuurman, Michael S.; Stolow, Albert
Journal of Chemical Physics (2011), 135 (16), 164309/1-164309/10CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
Excited state unimol. reactions of some polyenes exhibit localization of their dynamics at a single ethylenic double bond. Here we present studies of the fundamental photophys. processes in the ethylene unit itself. Combined femtosecond time-resolved photoelectron spectroscopy (TRPES) and ab initio quantum chem. calcns. was applied to the study of excited state dynamics in cis-butene, trans-butene, trimethylethylene, and tetramethylethylene, following initial excitation to their resp. π3s Rydberg states. The wavelength dependence of the π3s Rydberg state dynamics of tetramethylethylene was investigated in more detail. The π3s Rydberg to ππ* valence state decay rate varies greatly with substituent: the 1,2-di- and tri-Me substituted ethylenes (cis-butene, trans-butene, and trimethylethylene) show an ultrafast decay (∼20 fs), whereas the fully methylated tetramethylethylene shows a decay rate of 2 to 4 orders of magnitude slower. These observations are rationalized in terms of topog. trends in the relevant potential energy surfaces, as found from ab initio calcns.: (1) the barrier between the π3s state and the ππ* state increases with increasing methylation, and (2) the π3s/ππ* min. energy conical intersection displaces monotonically away from the π3s Franck-Condon region with increasing methylation. The use of systematic methylation in combination with TRPES and ab initio computation is emerging as an important tool in discerning the excited state dynamics of unsatd. hydrocarbons. (c) 2011 American Institute of Physics.
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Schalk, O.; Boguslavskiy, A. E.; Stolow, A. Substituent effects on dynamics at conical intersections: Cyclopentadienes. J. Phys. Chem. A 2010, 114, 4058– 4064, DOI: 10.1021/jp911286s
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Substituent Effects on Dynamics at Conical Intersections: Cyclopentadienes
Schalk, Oliver; Boguslavskiy, Andrey E.; Stolow, Albert
Journal of Physical Chemistry A (2010), 114 (12), 4058-4064CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
Substituent effects on dynamics at conical intersections are investigated by means of femtosecond time-resolved photoelectron spectroscopy for cyclopentadiene and its substituted analogs 1,2,3,4-tetramethylcyclopentadiene, 1,2,3,4,5-pentamethylcyclopentadiene, and 1,2,3,4-tetramethyl-5-propylcyclopentadiene. By UV excitation to the S2 (11B2) state, the influence of these substitutions on dynamics for the initially excited S2 (11B2) surface and the spectroscopically dark S1 (21A1) surface were investigated. We obsd. that the dynamics depend only on a small no. of specific vibrations. Whereas dynamics at the S2/S1-conical intersection are independent of substitution at the 5-position, internal conversion dynamics on the S1 (21A1) surface slow down as the inertia of the 5-substituent increases. Contrary to the expectations of simple models of radiationless transitions, an increasing d. of states does not lead to faster processes, suggesting that a true dynamical picture of vibrational motions at conical intersections will be required.
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Stolow, A.; Bragg, A. E.; Neumark, D. M. Femtosecond time-resolved photoelectron spectroscopy. Chem. Rev. 2004, 104, 1719– 1758, DOI: 10.1021/cr020683w
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Femtosecond Time-Resolved Photoelectron Spectroscopy
Stolow, Albert; Bragg, Arthur E.; Neumark, Daniel M.
Chemical Reviews (Washington, DC, United States) (2004), 104 (4), 1719-1757CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
A review on time-resolved photoelectron spectroscopy as applied to the dynamics of gas-phase neutral and anionic mols. and clusters is given. TRPES and its variants are powerful, relatively new techniques that lend themselves to highly detailed time-resolved studies of inter- and intramol. dynamics. A special attention was paid to applications for studying a variety of fundamental photochem. and photophys. processes. Such subjects as photoionization, electronic and nuclear coupling,rotational wave packets are discussed.
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Hertel, I. V.; Radloff, W. Ultrafast dynamics in isolated molecules and molecular clusters. Rep. Prog. Phys. 2006, 69, 1897, DOI: 10.1088/0034-4885/69/6/R06
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Ultrafast dynamics in isolated molecules and molecular clusters
Hertel, I. V.; Radloff, W.
Reports on Progress in Physics (2006), 69 (6), 1897-2003CODEN: RPPHAG; ISSN:0034-4885. (Institute of Physics Publishing)
A review. During the past decade the understanding of photo-induced ultrafast dynamics in mol. systems has improved at an unforeseen speed and a wealth of detailed insight into the fundamental processes has been obtained. This review summarizes our present knowledge on ultrafast dynamics in isolated mols. and mol. clusters evolving after excitation with femtosecond pulses as studied by pump-probe anal. in real time. Exptl. tools and methods as well as theor. models are described which have been developed to glean information on primary, ultrafast processes in photophysics, photochem. and photobiol. The relevant processes are explained by way of example-from wave packet dynamics in systems with a few atoms all the way to internal conversion via conical intersections in bio-chromophores. A systematic overview on characteristic systems follows, starting with diat. and including larger org. mols. as well as various types of mol. clusters, such as micro-solvated chromophore mols. For conciseness the focus is on mol. systems which remain unperturbed by the laser pulses-apart from the excitation and detection processes as such. Thus, only some aspects of controlling and manipulating mol. reactions by shaped and/or very intense laser pulses are discussed briefly for particularly instructive examples, illustrating the perspectives of this prospering field. The material presented in this review comprises some prototypical examples from earlier pioneering work but emphasizes studies from recent years and covers the most important and latest developments until Jan. 2006.
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Kim, S. K.; Pedersen, S.; Zewail, A. H. Direct femtosecond observation of the transient intermediate in the α-cleavage reaction of (CH₃)₂CO to 2CH₃+CO: Resolving the issue of concertedness. J. Chem. Phys. 1995, 103, 477, DOI: 10.1063/1.469614
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Direct femtosecond observation of the transient intermediate in the α-cleavage reaction of (CH3)2CO to 2CH3 + CO. Resolving the issue of concertedness
Kim, Sang Kyu; Pedersen, Soren; Zewail, Ahmed H.
Journal of Chemical Physics (1995), 103 (1), 477-80CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
For the elementary α-cleavage of acetone, we report the femtosecond resoln. of the intermediates using mass spectrometry. The results show the nonconcertedness of the reaction, provide the times for the primary and secondary C-C breakage, and indicate the role of electronic structure (σ*, antibonding impulse) and the vibrational motions involved.
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Shibata, T.; Suzuki, T. Photofragment ion imaging with femtosecond laser pulses. Chem. Phys. Lett. 1996, 262, 115– 119, DOI: 10.1016/0009-2614(96)01024-X
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Photofragment ion imaging with femtosecond laser pulses
Shibata, Takeshi; Suzuki, Toshinori
Chemical Physics Letters (1996), 262 (1,2), 115-119CODEN: CHPLBC; ISSN:0009-2614. (Elsevier)
Photofragment ion imaging with femtosecond real-time clocking has been applied to α-bond cleavage from 1(n, π*) states of acetyl chloride and acetone. It is shown that dissocn. occurs within the time comparable with laser pulse duration of 200 fs in acetyl chloride, whereas the reaction time is longer than 15 ps in acetone. The dissocn. in the neutral state and the fragmentation in the ionic state are discriminated from images of photofragment ion distributions.
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Buzza, S. A.; Snyder, E. M.; Castleman, A. W. Further direct evidence for stepwise dissociation of acetone and acetone clusters. J. Chem. Phys. 1996, 104, 5040, DOI: 10.1063/1.471133
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Further direct evidence for stepwise dissociation of acetone and acetone clusters
Buzza, S. A.; Snyder, E. M.; Castleman, A. W., Jr.
Journal of Chemical Physics (1996), 104 (13), 5040-7CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
The (pre)dissocn. of acetone and acetone clusters after excitation to states corresponding to upper {S1,T1} and 3s Rydberg states of the acetone monomer are investigated through femtosecond pump-probe expts. coupled with mol. beam time-of-flight mass spectrometry techniques. Upon excitation to either state, [(CH3)2CO]n* dissocs. rapidly. Acetyl fragments, [(CH3)2CO]n-1CH3CO+ may arise from ionization of an excited species formed by (pre)dissocn. of intact precursors or by dissocn. after the intact species has been ionized. The method employed to sep,. these two channels is discussed herein; the resulting transients are fit to a kinetic model to elucidate intermediate lifetimes and dissocn. mechanisms. The present expts. establish that a stepwise dissocn. mechanism is operative upon excitation to the 3s Rydberg state for the acetone monomer and dimer, with their corresponding acetyl fragments having lifetimes on the order of picoseconds. Larger cluster species, [(CH3)2CO]n (n > 2), do not exhibit the predissocn. behavior evident in the monomer and dimer. Conversely, dissocn. upon excitation to the {S1,T1} state exhibits an initial loss of a Me unit, with the acetyl intermediate being considerably more stable than those created by dissocn. of acetone from higher lying states. A strong dependence on the internal energy available after the dissocn. event is noted.
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Rusteika, N.; Møller, K. B.; Sølling, T. I. New insights on the photodynamics of acetone excited with 253–288nm femtosecond pulses. Chem. Phys. Lett. 2008, 461, 193– 197, DOI: 10.1016/j.cplett.2008.06.079
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New insights on the photodynamics of acetone excited with 253-288 nm femtosecond pulses
Rusteika, Nerijus; Moller, Klaus B.; Solling, Theis I.
Chemical Physics Letters (2008), 461 (4-6), 193-197CODEN: CHPLBC; ISSN:0009-2614. (Elsevier B.V.)
The authors have performed time-resolved photoelectron spectroscopy and mass spectrometry expts. to address the dynamics that result when gaseous acetone mols. are excited with femtosecond pulses in the 253-288 nm wavelength range. There are several previous examples of time-resolved mass spectrometry expts. and the authors results are in line with previously published data. However, the results of the photoelectron spectroscopy expts. allow one to show that the ultrafast dynamics related to the S1 state can be attributed entirely to photophys. processes. In essence, the dynamics that is induced by a one-photon excitation is governed by the motion out of the Franck-Condon region on the S1 surface to the relaxed geometry in less than 30 fs. The relaxed S1 species does not decay in 100 ps and actual C-C bond breakage must take place on a longer time scale.
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Hüter, O.; Temps, F. Ultrafast α–CC bond cleavage of acetone upon excitation to 3p and 3d Rydberg states by femtosecond time-resolved photoelectron imaging. J. Chem. Phys. 2016, 145, 214312, DOI: 10.1063/1.4971243
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Ultrafast α -CC bond cleavage of acetone upon excitation to 3p and 3d Rydberg states by femtosecond time-resolved photoelectron imaging
Hueter, O.; Temps, F.
Journal of Chemical Physics (2016), 145 (21), 214312/1-214312/12CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
The radiationless electronic relaxation and α -CC bond fission dynamics of jet-cooled acetone in the S1 (nπ*) state and in high-lying 3p and 3d Rydberg states have been investigated by femtosecond time-resolved mass spectrometry and photoelectron imaging. The S1 state was accessed by absorption of a UV pump photon at selected wavelengths between λ = 320 and 250 nm. The obsd. acetone mass signals and the S1 photoelectron band decayed on sub-picosecond time scales, consistent with a recently proposed ultrafast structural relaxation of the mols. in the S1 state away from the Franck-Condon probe window. No direct signatures could be obsd. by the expts. for CC dissocn. on the S1 potential energy hypersurface in up to 1 ns. The obsd. acetyl mass signals at all pump wavelengths turned out to be assocd. with absorption by the mols. of one or more addnl. pump and/or probe photons. In particular, absorption of a second UV pump photon by the S1 (nπ*) state was found to populate a series of high-lying states belonging to the n = 3 Rydberg manifold. The resp. transitions are favored by much larger cross sections compared to the S1 ← S0 transition. The characteristic energies revealed by the photoelectron images allowed for assignments to the 3p and 3dyz states. At two-photon excitation energies higher than 8.1 eV, an ultrafast reaction pathway for breaking the α -CC bond in 50-90 fs via the 3dyz Rydberg state and the elusive ππ* state was obsd., explaining the formation of acetyl radicals after femtosecond laser excitation of acetone at these wavelengths. (c) 2016 American Institute of Physics.
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Maierhofer, P.; Bainschab, M.; Thaler, B.; Heim, P.; Ernst, W. E.; Koch, M. Disentangling multichannel photodissociation dynamics in acetone by time-resolved photoelectron-photoion coincidence spectroscopy. J. Phys. Chem. A 2016, 120, 6418– 6423, DOI: 10.1021/acs.jpca.6b07238
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Disentangling Multichannel Photodissociation Dynamics in Acetone by Time-Resolved Photoelectron-Photoion Coincidence Spectroscopy
Maierhofer, Paul; Bainschab, Markus; Thaler, Bernhard; Heim, Pascal; Ernst, Wolfgang E.; Koch, Markus
Journal of Physical Chemistry A (2016), 120 (32), 6418-6423CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
For the study of photoinduced dynamics in mols. with time-resolved pump-probe photoionization spectroscopy, it is essential to obtain unequivocal information about the fragmentation behavior induced by the laser pulses. The authors present time-resolved photoelectron-photoion coincidence (PEPICO) expts. to study the excited-state dynamics of isolated acetone mols. triggered by 2-photon (269 nm) excitation. In the complex situation of different relaxation pathways, the authors unambiguously identify three distinct pump-probe ionization channels. The high selectivity of PEPICO detection allows one to observe the fragmentation behavior and to follow the time evolution of each channel sep. For channels leading to fragment ions, the authors quant. obtain the fragment-to-parent branching ratio and are able to det. exptl. whether dissocn. occurs in the neutral mol. or in the parent ion. These results highlight the importance of coincidence detection for the interpretation of time-resolved photochem. relaxation and dissocn. studies if multiple pathways are present.
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Couch, D. E.; Kapteyn, H. C.; Murnane, M. M.; Peters, W. K. Uncovering highly-excited state mixing in acetone using ultrafast VUV pulses and coincidence imaging techniques. J. Phys. Chem. A 2017, 121, 2361– 2366, DOI: 10.1021/acs.jpca.7b01112
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Uncovering Highly-Excited State Mixing in Acetone Using Ultrafast VUV Pulses and Coincidence Imaging Techniques
Couch, David E.; Kapteyn, Henry C.; Murnane, Margaret M.; Peters, William K.
Journal of Physical Chemistry A (2017), 121 (12), 2361-2366CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
Understanding the ultrafast dynamics of highly excited electronic states of small mols. is crit. for a better understanding of atm. and astrophys. processes, as well as for designing coherent control strategies for manipulating chem. dynamics. In highly excited states, nonadiabatic coupling, electron-electron interactions, and the high d. of states govern dynamics. However, these states are computationally and exptl. challenging to access. Fortunately, new sources of ultrafast vacuum UV pulses, in combination with electron-ion coincidence spectroscopies, provide new tools to unravel the complex electronic landscape. Here the authors report time-resolved photoelectron-photoion coincidence expts. using 8 eV pump photons to study the highly excited states of acetone. The authors uncover for the first time direct evidence that the resulting excited state consists of a mixt. of both ny → 3p and π → π* character, which decays with a time const. of 330 fs. In the future, this approach can inform models of VUV photochem. and aid in designing coherent control strategies for manipulating chem. reactions.
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Uenishi, R.; Horio, T.; Suzuki, T. Time-resolved photoelectron imaging of acetone with 9.3 eV photoexcitation. J. Phys. Chem. A 2019, 123, 6848– 6853, DOI: 10.1021/acs.jpca.9b05179
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Time-Resolved Photoelectron Imaging of Acetone with 9.3 eV Photoexcitation
Uenishi, Ryuta; Horio, Takuya; Suzuki, Toshinori
Journal of Physical Chemistry A (2019), 123 (32), 6848-6853CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
Ultrafast electronic relaxation following 9.3 eV photoexcitation of gaseous acetone was investigated with time-resolved photoelectron imaging spectroscopy. An intense photoionization signal due to a transition from the 41A1(π,π*) state to the D1(π-1) cationic state diminishes within 50 fs, owing to vibrational wave packet motion leaving our observation energy window. Addnl. photoionization signals were assigned to transitions from Rydberg states with principal quantum nos. of 3-8 to the D0(n-1) cationic state, created by strong vibronic couplings with the bright 41A1(π,π*) state. The deactivation processes of the 41A1(π,π*) and Rydberg states are discussed based on their decay profiles obtained from a time-energy map of photoelectron kinetic energy distributions.
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Koch, M.; Heim, P.; Thaler, B.; Kitzler, M.; Ernst, W. E. Direct observation of a photochemical activation energy: a case study of acetone photodissociation. J. Phys. B: At., Mol. Opt. Phys. 2017, 50, 125102, DOI: 10.1088/1361-6455/aa6a71
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Direct observation of a photochemical activation energy: a case study of acetone photodissociation
Koch, Markus; Heim, Pascal; Thaler, Bernhard; Kitzler, Markus; Ernst, Wolfgang E.
Journal of Physics B: Atomic, Molecular and Optical Physics (2017), 50 (12), 125102/1-125102/8CODEN: JPAPEH; ISSN:0953-4075. (IOP Publishing Ltd.)
The ability to observe and quantify the conversion of electronic potential energy to vibrational kinetic energy in a mol. after photoexcitation is essential to understand and control the outcome of photoinduced mol. fragmentation. We exploit the high selectivity of photoelectron-photoion coincidence detection to distinguish different relaxation channels and observe the fragmentation behavior of each channel. We demonstrate the concept by investigating the fragmentation of gas-phase acetone mols. initiated by three-photon excitation to high lying Rydberg states between 9.0 and 9.5 eV above the ground state. By applying variations of the photon energy, pulse duration (100-200 fs) and pulse energy, we are able to fully characterize the fragmentation process. Rydberg states between 5s and 8s are populated, which undergo ultrafast internal conversion to lower states. The corresponding nonadiabatic dynamics in the neutral mol. cause the conversion of electronic to vibrational energy, leading to fragmentation. Our scheme allows us to directly measure the activation energy for fragmentation of acetone to an acetyl ion and a Me radical, which we det. to be (0.79±0.04) eV. Longer laser pulses result in an increased fragment-to-parent ratio, representing a higher probability for relaxation because the relaxation time consts. are comparable to the pulse duration. Upon excitation to Rydberg states at 9.5 eV we surprisingly observe reduced fragmentation, although ∼2 eV are coupled into vibrational energy, indicating that different relaxation pathways become active, which results in a change of the redistribution of vibrational energy within the mol. Fragmentation due to subsequent excitation of the cation is found to play a minor role.
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Sølling, T. I.; Diau, E. W.-G.; Kötting, C.; De Feyter, S.; Zewail, A. H. Femtochemistry of Norrish Type I reactions: IV. Highly excited ketones—Experimental. ChemPhysChem 2002, 3, 79– 97, DOI: 10.1002/1439-7641(20020118)3:1<79::AID-CPHC79>3.0.CO;2-#
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Femtochemistry of Norrish type-I reactions: IV. Highly excited ketones-experimental
Solling, Theis I.; Diau, Eric W.-G.; Kotting, Carsten; De Feyter, Steven; Zewail, Ahmed H.
ChemPhysChem (2002), 3 (1), 79-97CODEN: CPCHFT; ISSN:1439-4235. (Wiley-VCH Verlag GmbH)
The two α-CC bonds in a series of cyclic and acyclic ketone were obsd. to cleave in a stepwise and nonstatistical manner. The first bond breakage occurs in 60 - 290 fs and leads to a linear excited-state acyl radical. The further decompn. of this species is up to an order of magnitude slower. The initial configuration of the acyl radical dets. whether the second bond breakage proceeds via a slow (blue) or a fast (red) trajectory.
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Thakur, S. N.; Guo, D.; Kundu, T.; Goodman, L. Two-photon photoacoustic spectroscopy of acetone 3p Rydberg states. Chem. Phys. Lett. 1992, 199, 335– 340, DOI: 10.1016/0009-2614(92)80128-X
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Two-photon photoacoustic spectroscopy of acetone 3p Rydberg states
Thakur, Surya N.; Guo, Ding; Kundu, Tapanendu; Goodman, Lionel
Chemical Physics Letters (1992), 199 (3-4), 335-40CODEN: CHPLBC; ISSN:0009-2614.
Two-photon photoacoustic spectra of acetone-h6 and -d6 were recorded using a pulsed laser in the 3p←n Rydberg transition region (332.2-338.7 nm for two-photon excitation). Comparison of the acetone-h6 and -d6 photoacoustic and two-photon resonance enhanced multiphoton ionization spectra shows an intensity reversal between the (3py←n)1A1 and (3px←n)1A2 transition origins. The dramatic increase in the 1A1 state - and to a lesser extent for the 1B2 state - photoacoustic signals requires efficient radiationless/dissociative channels for these states, not present for 1A2. The intensity effects are interpreted through the 1A1 state having substantial π*←π valence character in contrast to almost pure Rydberg character for the 1A2 state.
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Xing, X.; McDiarmid, R.; Philis, J. G.; Goodman, L. Vibrational assignments in the 3p Rydberg states of acetone. J. Chem. Phys. 1993, 99, 7565– 7573, DOI: 10.1063/1.465686
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Vibrational assignments in the 3p Rydberg states of acetone
Xing, Xing; McDiarmid, Ruth; Philis, John G.; Goodman, Lionel
Journal of Chemical Physics (1993), 99 (10), 7565-73CODEN: JCPSA6; ISSN:0021-9606.
The 2 and 3 photon resonantly enhanced multiphoton ionization spectra of the 3p Rydberg ← ~X transitions of acetone and acetone-d6 were remeasured and reanalyzed. Seven of the 8 a1 and 1 b1 vibrational modes were assigned. From these assigned fundamental frequencies the anomalous isotope shift of the origin of the A1 transition was rationalized, the contribution of the nonbonding electrons to the scissors force const. was demonstrated, and a location for the A1 ππ* valence excited transition was proposed.
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Merchán, M.; Roos, B. O.; McDiarmid, R.; Xing, X. A combined theoretical and experimental determination of the electronic spectrum of acetone. J. Chem. Phys. 1996, 104, 1791, DOI: 10.1063/1.470976
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A combined theoretical and experimental determination of the electronic spectrum of acetone
Merchan, Manuela; Roos, Bjorn O.; McDiarmid, ruth; Xing, Xing
Journal of Chemical Physics (1996), 104 (5), 1791-804CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
A combined ab initio and exptl. investigation has been performed of the main features of the electronic spectrum of acetone. Vertical transition energies have been calcd. from the ground to the ny → π*, π→π*, and the n = 3 Rydberg states. In addn., the 1A1 energy surfaces have been studied as functions of the CO bond length. The 1A1 3p and 3d states were found to be heavily perturbed by the π→π* state. Resonant multiphoton ionization and polarization-selected photoacoustic spectra of acetone have been measured and obsd. transitions were assigned on internal criteria. The calcd. vertical transition energies to the ny→π* and all Rydberg states were found to be in agreement with expt. This includes the 3s-, all three 3p-, and the A1, B1, and B2 3d-Rydberg states. By contrast, there is little agreement between the calcd. and exptl. relative intensities of the A1 and B2 3d-Rydberg transitions. In addn., anomalously intense high vibrational overtone bands of one of the 3p-Rydberg transitions have been obsd. These results confirm the strong perturbation of the 3p-Rydberg states by the π→π* state found in the theor. calcn. and support the calcd. position of this unobserved state.
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ter Steege, D. H. A.; Wirtz, A. C.; Buma, W. J. Vibronic coupling in excited states of acetone. J. Chem. Phys. 2002, 116, 547– 560, DOI: 10.1063/1.1423946
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Vibronic coupling in excited states of acetone
ter Steege, D. H. A.; Wirtz, A. C.; Buma, W. J.
Journal of Chemical Physics (2002), 116 (2), 547-560CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
Photoelectron spectroscopy of Rydberg states of acetone-h6 and -d6 populated by two- or three-photon excitation was employed to unravel the vibronic description of excited-state levels. For the 3p Rydberg states vibronic transitions were reanalyzed, leading to various reassignments and the observation of hitherto non-reported transitions. In addn., several ionic vibrational frequencies could be detd. At higher excitation energies previously identified, and in the present study newly identified, members of two Rydberg series were characterized. The ns Rydberg series was explored up to the 8s state, the nd series up to the 7d state. Based upon the unambiguous assignments of vibronic character that the authors obtain for excited-state levels, various valence-Rydberg and Rydberg-Rydberg vibronic coupling pathways come to light and are analyzed.
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McDiarmid, R.; Xing, X. Nonadiabatic coupling of the 3p Rydberg and ππ* valence states of acetone. J. Chem. Phys. 1997, 107, 675– 679, DOI: 10.1063/1.475152
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Nonadiabatic coupling of the 3p Rydberg and ππ* valence states of acetone
McDiarmid, Ruth; Xing, Xing
Journal of Chemical Physics (1997), 107 (3), 675-679CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
The 3p Rydberg region of the spectra of acetone and acetone-d6 was studied by resonantly enhanced multiphoton ionization and photoacoustic spectroscopies. Differences between the spectra of cold and room temp. samples, between REMPI and PA spectral measurements, and between the laser power dependences of the different 3p ← ~X origins arise from a nonadiabatic coupling of the A1 3p Rydberg and A1 ππ* states of acetone. The coupling is proposed to arise from a seam of conical intersection between these 2 A1 states on the CO stretch-C2CO pyramidalization plane. An analogous seam is proposed to exist between the A1 3d Rydberg and A1 ππ* states.
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Mai, S.; Richter, M.; Heindl, M.; Menger, M. F. S. J.; Atkins, A. J.; Ruckenbauer, M.; Plasser, F.; Oppel, M.; Marquetand, P.; González, L. SHARC2.0: Surface Hopping Including Arbitrary Couplings – program package for non-adiabatic dynamics; sharc-md.org, 2018.
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Plasser, F.; Gómez, S.; Mai, S.; González, L. Highly efficient surface hopping dynamics using a linear vibronic coupling model. Phys. Chem. Chem. Phys. 2019, 21, 57– 69, DOI: 10.1039/C8CP05662E
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Highly efficient surface hopping dynamics using a linear vibronic coupling model
Plasser, Felix; Gomez, Sandra; Menger, Maximilian F. S. J.; Mai, Sebastian; Gonzalez, Leticia
Physical Chemistry Chemical Physics (2019), 21 (1), 57-69CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
We report an implementation of the linear vibronic coupling (LVC) model within the surface hopping dynamics approach and present utilities for parameterizing this model in a blackbox fashion. This results in an extremely efficient method to obtain qual. and even semi-quant. information about the photodynamical behavior of a mol., and provides a new route toward benchmarking the results of surface hopping computations. The merits and applicability of the method are demonstrated in a no. of applications. First, the method is applied to the SO2 mol. showing that it is possible to compute its absorption spectrum beyond the Condon approxn., and that all the main features and timescales of previous on-the-fly dynamics simulations of intersystem crossing are reproduced while reducing the computational effort by three orders of magnitude. The dynamics results are benchmarked against exact wavepacket propagations on the same LVC potentials and against a variation of the electronic structure level. Four addnl. test cases are presented to exemplify the broader applicability of the model. The photodynamics of the isomeric adenine and 2-aminopurine mols. are studied and it is shown that the LVC model correctly predicts ultrafast decay in the former and an extended excited-state lifetime in the latter. Futhermore, the method correctly predicts ultrafast intersystem crossing in the modified nucleobase 2-thiocytosine and its absence in 5-azacytosine while it fails to describe the ultrafast internal conversion to the ground state in the latter.
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Subotnik, J. E.; Jain, A.; Landry, B.; Petit, A.; Ouyang, W.; Bellonzi, N. Understanding the surface hopping view of electronic transitions and decoherence. Annu. Rev. Phys. Chem. 2016, 67, 387– 417, DOI: 10.1146/annurev-physchem-040215-112245
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Understanding the Surface Hopping View of Electronic Transitions and Decoherence
Subotnik, Joseph E.; Jain, Amber; Landry, Brian; Petit, Andrew; Ouyang, Wenjun; Bellonzi, Nicole
Annual Review of Physical Chemistry (2016), 67 (), 387-417CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews)
We present a current, up-to-date review of the surface hopping methodol. for solving nonadiabatic problems, 25 years after Tully published the fewest switches surface hopping algorithm. After reviewing the original motivation for and failures of the algorithm, we give a detailed examn. of modern advances, focusing on both theor. and practical issues. We highlight how one can partially derive surface hopping from the Schrodinger equation in the adiabatic basis, how one can change basis within the surface hopping algorithm, and how one should understand and apply the notions of decoherence and wavepacket bifurcation. The question of time reversibility and detailed balance is also examd. at length. Recent applications to photoexcited conjugated polymers are discussed briefly.
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Wang, L.; Akimov, A.; Prezhdo, O. V. Recent progress in surface hopping: 2011–2015. J. Phys. Chem. Lett. 2016, 7, 2100– 2112, DOI: 10.1021/acs.jpclett.6b00710
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Recent Progress in Surface Hopping: 2011-2015
Wang, Linjun; Akimov, Alexey; Prezhdo, Oleg V.
Journal of Physical Chemistry Letters (2016), 7 (11), 2100-2112CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
A review. Developed 25 years ago, Tully's fewest switches surface hopping (FSSH) has proven to be the most popular approach for simulating quantum-classical dynamics in a broad variety of systems, ranging from the gas phase, to the liq. and solid phases, to biol. and nanoscale materials. FSSH is widely adopted as the fundamental platform to introduce modifications as needed. Significant progress has been made recently to enhance the accuracy and efficiency of the surface hopping technique. Various limitations of the std. FSSH-assocd. with quantum nuclear effects, interference and decoherence, trivial or "unavoided" crossings, superexchange, and representation dependence-have been lifted. These advances are needed to allow one to treat many important phenomena in chem., physics, materials, and related disciplines. Examples include charge transport in extended systems such as org. solids, singlet fission in mol. aggregates, Auger-type exciton multiplication, recombination and relaxation in quantum dots and other nanoscale materials, Auger-assisted charge transfer, nonradiative luminescence quenching, and electron-hole recombination. This Perspective summarizes recent advances in the surface hopping formulation of nonadiabatic dynamics and provides an outlook on the future of surface hopping.
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Plasser, F.; Mai, S.; Fumanal, M.; Gindensperger, E.; Daniel, C.; González, L. Strong influence of decoherence corrections and momentum rescaling in surface hopping dynamics of transition metal complexes. J. Chem. Theory Comput. 2019, 15, 5031– 5045, DOI: 10.1021/acs.jctc.9b00525
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Strong Influence of Decoherence Corrections and Momentum Rescaling in Surface Hopping Dynamics of Transition Metal Complexes
Plasser, Felix; Mai, Sebastian; Fumanal, Maria; Gindensperger, Etienne; Daniel, Chantal; Gonzalez, Leticia
Journal of Chemical Theory and Computation (2019), 15 (9), 5031-5045CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)
The reliability of different parameters in the surface hopping method is assessed for a vibronic coupling model of a challenging transition metal complex, where a large no. of electronic states of different multiplicities are met within a small energy range. In particular, the effect of two decoherence correction schemes and of various strategies for momentum rescaling and treating frustrating hops during the dynamics is investigated and compared against an accurate quantum dynamics simulation. The results show that surface hopping is generally able to reproduce the ref. but also that small differences in the protocol used can strongly affect the results. We find a clear preference for momentum rescaling along only one degree of freedom, using either the nonadiabatic coupling or the gradient difference vector, and trace this effect back to an enhanced no. of frustrated hops. Furthermore, reflection of the momentum after frustrated hops is shown to work better than to ignore the process completely. The study also highlights the importance of the decoherence correction but neither of the two methods employed, energy based decoherence or augmented fewest switches surface hopping, performs completely satisfactory and we trace this effect back to a lack of size-consistency. Finally, the effect of different methods for analyzing the populations is highlighted. More generally, the study emphasizes the importance of the often neglected parameters in surface hopping and shows that there is still need for simple, robust, and generally applicable correction schemes.
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Kruit, P.; Read, F. Magnetic field paralleliser for 2π electron-spectrometer and electron-image magnifier. J. Phys. E: Sci. Instrum. 1983, 16, 313, DOI: 10.1088/0022-3735/16/4/016
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Magnetic field parallelizer for 2π electron spectrometer and electron-image magnifier
Kruit, P.; Read, F. H.
Journal of Physics E: Scientific Instruments (1983), 16 (4), 313-24CODEN: JPSIAE; ISSN:0022-3735.
An electron spectrometer is described in which electrons originally emitted over 2π steradians from a region of small vol. are formed into a beam of half-angle 2°. The instrument uses a magnetic field that diverges from 1 to 10-3T. Parallelized electrons of energy 0-3 eV were measured with a time-of-flight technique, and gave energy resolns. as low as 15 meV. Addn. of an elec. field near the source permits selection of a solid angle of 0-4π steradians. The device can also act as an electron-image magnifier, giving a spatial resoln. of a few μm in the source plane.
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Fumanal, M.; Plasser, F.; Mai, S.; Daniel, C.; Gindensperger, E. Interstate vibronic coupling constants between electronic excited states for complex molecules. J. Chem. Phys. 2018, 148, 124119, DOI: 10.1063/1.5022760
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Interstate vibronic coupling constants between electronic excited states for complex molecules
Fumanal, Maria; Plasser, Felix; Mai, Sebastian; Daniel, Chantal; Gindensperger, Etienne
Journal of Chemical Physics (2018), 148 (12), 124119/1-124119/11CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
In the construction of diabatic vibronic Hamiltonians for quantum dynamics in the excited-state manifold of mols., the coupling consts. are often extd. solely from information on the excited-state energies. Here, a new protocol is applied to get access to the interstate vibronic coupling consts. at the time-dependent d. functional theory level through the overlap integrals between excited-state adiabatic auxiliary wavefunctions. We discuss the advantages of such method and its potential for future applications to address complex systems, in particular, those where multiple electronic states are energetically closely lying and interact. We apply the protocol to the study of prototype rhenium carbonyl complexes [Re(CO)3(N,N)(L)]n+ for which non-adiabatic quantum dynamics within the linear vibronic coupling model and including spin-orbit coupling have been reported recently. (c) 2018 American Institute of Physics.
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Dreuw, A.; Wormit, M. The algebraic diagrammatic construction scheme for the polarization propagator for the calculation of excited states. WIREs Comput. Mol. Sci. 2015, 5, 82– 95, DOI: 10.1002/wcms.1206
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The algebraic diagrammatic construction scheme for the polarization propagator for the calculation of excited states
Dreuw, Andreas; Wormit, Michael
Wiley Interdisciplinary Reviews: Computational Molecular Science (2015), 5 (1), 82-95CODEN: WIRCAH; ISSN:1759-0884. (Wiley-Blackwell)
The algebraic diagrammatic construction (ADC) scheme for the polarization propagator provides a series of ab initio methods for the calcn. of excited states based on perturbation theory. In recent years, the second-order ADC(2) scheme has attracted attention in the computational chem. community because of its reliable accuracy and reasonable computational effort in the calcn. of predominantly singly excited states. Owing to their size-consistency, ADC methods are suited for the investigation of large mols. In addn., their Hermitian structure and the availability of the intermediate state representation (ISR) allow for straightforward computation of excited-state properties. Recently, an efficient implementation of ADC(3) has been reported, and its high accuracy for typical valence excited states of org. chromophores has been demonstrated. In this review, the origin of ADC-based excited-state methods in propagator theory is described, and an intuitive route for the derivation of algebraic expressions via the ISR is outlined and comparison to other excited-state methods is made. Existing computer codes and implemented ADC variants are reviewed, but most importantly the accuracy and limits of different ADC schemes are critically examd. WIREs Comput Mol Sci 2015, 5:82-95. doi: 10.1002/wcms.1206 Conflict of interest: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the .
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Dunning, T. H. Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen. J. Chem. Phys. 1989, 90, 1007– 1023, DOI: 10.1063/1.456153
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Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen
Dunning, Thom H., Jr.
Journal of Chemical Physics (1989), 90 (2), 1007-23CODEN: JCPSA6; ISSN:0021-9606.
Guided by the calcns. on oxygen in the literature, basis sets for use in correlated at. and mol. calcns. were developed for all of the first row atoms from boron through neon, and for hydrogen. As in the oxygen atom calcns., the incremental energy lowerings, due to the addn. of correlating functions, fall into distinct groups. This leads to the concept of correlation-consistent basis sets, i.e., sets which include all functions in a given group as well as all functions in any higher groups. Correlation-consistent sets are given for all of the atoms considered. The most accurate sets detd. in this way, [5s4p3d2f1g], consistently yield 99% of the correlation energy obtained with the corresponding at.-natural-orbital sets, even though the latter contains 50% more primitive functions and twice as many primitive polarization functions. It is estd. that this set yields 94-97% of the total (HF + 1 + 2) correlation energy for the atoms neon through boron.
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Kaufmann, K.; Baumeister, W.; Jungen, M. Universal Gaussian basis sets for an optimum representation of Rydberg and continuum wavefunctions. J. Phys. B: At., Mol. Opt. Phys. 1989, 22, 2223, DOI: 10.1088/0953-4075/22/14/007
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Universal Gaussian basis sets for an optimum representation of Rydberg and continuum wave functions
Kaufmann, Karl; Baumeister, Werner; Jungen, Martin
Journal of Physics B: Atomic, Molecular and Optical Physics (1989), 22 (14), 2223-40CODEN: JPAPEH; ISSN:0953-4075.
A universal-Gaussian-basis-set concept for the calcn. of Rydberg and continuum states by pure L2 methods is presented. It is based on the generation of optimized sequences of Gaussian exponents by maximizing the overlap with a series of Slater-type functions characterized by a const. exponent and a variable principal quantum no. In this way, linear combinations of Gaussian basis functions can be found which are ideally suited to imitate Laguerre-Slater functions. It is thus possible to obtain optimum representations of Rydberg orbitals or of complete orthonormal systems of Laguerre functions playing an important role in the L2 expansion of continuum functions. The basis sets were tested with the hydrogen atom. The effectiveness of the basis is illustrated by the calcn. of quantum defects assocd. with the s, p and d Rydberg series of the alkali metal atoms Li and Na. The phase shifts detd. in the ionization continua of these systems nicely fit the series below the ionization limit, as is finally demonstrated by an Edlen plot.
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TURBOMOLE V7.0, A development of University of Karlsruhe and Forschungszentrum Karlsruhe GmbH, 2015.
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Granucci, G.; Persico, M.; Toniolo, A. Direct semiclassical simulation of photochemical processes with semiempirical wave functions. J. Chem. Phys. 2001, 114, 10608– 10615, DOI: 10.1063/1.1376633
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Direct semiclassical simulation of photochemical processes with semiempirical wave functions
Granucci, G.; Persico, M.; Toniolo, A.
Journal of Chemical Physics (2001), 114 (24), 10608-10615CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
The authors describe a new method for the simulation of excited state dynamics, based on classical trajectories and surface hopping, with direct semiempirical calcn. of the electronic wave functions and potential energy surfaces (DTSH method). Semiempirical self-consistent-field MOs (SCF MO's) are computed with geometry-dependent occupation nos., in order to ensure correct homolytic dissocn., fragment orbital degeneracy, and partial optimization of the lowest virtuals. Electronic wave functions are of the MO active space CI type, for which analytic energy gradients have been implemented. The time-dependent electronic wave function is propagated by means of a local diabatization algorithm which is inherently stable also in the case of surface crossings. The method is tested for the problem of excited ethylene nonadiabatic dynamics, and the results are compared with recent quantum mech. calcns.
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50
Critical appraisal of the fewest switches algorithm for surface hopping
Granucci, Giovanni; Persico, Maurizio
Journal of Chemical Physics (2007), 126 (13), 134114/1-134114/11CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
In this paper the authors address the problem of internal consistency in trajectory surface hopping methods, i.e., the requirement that the fraction of trajectories running on each electronic state equals the probabilities computed by the electronic time-dependent Schroedinger equation, after averaging over all trajectories. They derive a formula for the hopping probability in Tully's "fewest switches" spirit that would yield a rigorously consistent treatment. They show the relationship of Tully's widely used surface hopping algorithm with the "exact" prescription that cannot be applied when running each trajectory independently. They also bring out the connection of the consistency problem with the coherent propagation of the electronic wave function and the artifacts caused by coherent Rabi-type oscillations of the state probabilities in weak coupling regimes. A real mol. (azobenzene) and two ad hoc models serve as examples to illustrate the above theor. arguments. Following a proposal by Truhlar's group [Zhu [et al.], J. Chem. Phys. 121, 7658 (2004) Zhu [et al.], J. Chem. Theory Comput. 1, 527 (2005)], they apply a decoherence correction to the state probabilities, in conjunction with Tully's algorithm, and they obtain satisfactory results in terms of internal consistency and of agreement with the outcomes of quantum wave packet calcns.

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J. Patrick Zobel, Moritz Heindl, Felix Plasser, Sebastian Mai, Leticia González. Surface Hopping Dynamics on Vibronic Coupling Models. Accounts of Chemical Research 2021, 54 (20) , 3760-3771. https://doi.org/10.1021/acs.accounts.1c00485
Ruaridh Forbes, Simon P. Neville, Martin A. B. Larsen, Anja Röder, Andrey E. Boguslavskiy, Rune Lausten, Michael S. Schuurman, Albert Stolow. Vacuum Ultraviolet Excited State Dynamics of the Smallest Ketone: Acetone. The Journal of Physical Chemistry Letters 2021, 12 (35) , 8541-8547. https://doi.org/10.1021/acs.jpclett.1c02612
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Abstract
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Figure 1
Figure 1. (a) Schematic overview of the relevant potential energy surfaces of acetone excited states, including the n3p and ππ* states. (b) Basic kinetic model assumed for the nonadiabatic dynamics among the acetone n3p and ππ* states with the nine considered time constants.
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Figure 2
Figure 2. Overview of the experimental results. Measured transient photoelectron spectra (a), the 2D global fit of the spectrum (b) with corresponding DAS (c) for 333 nm pump wavelength (E_exc = 7.44 eV). Panel d shows the time constant dependence over excitation energy, including three data points from Hüter and Temps. (27) The red lines in panels a and b indicate a change of the vertical axis scale. PE, photoelectron kinetic energy; E_exc, two-photon excitation energy.
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Figure 3
Figure 3. Overview of the theoretical results obtained with the SHARC-LVC method. (a–c) Temporal evolution of the diabatic populations (thin lines) and kinetic model fits (thick lines), for the ensemble starting in (a) n3p_x, (b) n3p_y, and (c) n3p_z. (d) Scheme showing the fitted time constants and associated errors (see Figure S8 in section S4 in the Supporting Information for a similar fit enforcing detailed balance, showing that τ_xy might be overestimated and τ_xz underestimated but otherwise the time constants are consistent with detailed balance). (e) Plot of the energy dependence of the eigenvalue-derived effective time constants and comparison to the experimental and literature (27) values.
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References
This article references 50 other publications.
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  A review. In recent years, computational photochem. has achieved increasing consideration as a valid tool for the investigation of photochem. reaction mechanisms in org. chromophores. A theor. chemist can now adapt his/her "instruments" to the subject under investigation, as every other scientist does when there is a problem to study and a methodol. to be chosen. Thus, different computational strategies and tools can now be operated like a virtual spectrometer to characterize the photoinduced mol. deformation and reactivity of a given chromophore, so that a full description of the reactive process (i.e. its reaction coordinate) from energy absorption to photoproducts formation can be achieved. Here we will review the basic concepts, the computational strategy and the theor. tools, which permit this thorough description to be realized. Applications to the biol. and technol. relevant problem of photoinduced isomerizations in non-polar and highly polar conjugated polyenes will be shown, including also environment effects. Recent advances in this area (namely external charge effects) will be presented, together with new computational approaches, which allow mol. systems of biol. size (e.g. the rhodopsin photoreceptors) to be investigated at an unprecedented level of accuracy. This should open the way to the accurate investigation of sizable systems in realistic conditions, providing chemists with information that might be used in mol. technol. as a guideline for the design of artificial photoswitchable devices and the control of their photoinduced processes.
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  Surface-hopping dynamics coupled to linear response TDDFT and explicit nonadiabatic and spin-orbit couplings have been used to model the ultrafast intersystem crossing (ISC) dynamics in [Ru(bpy)3]2+. Simulations using an ensemble of trajectories starting from the singlet metal-to-ligand charge transfer (1MLCT) band show that the manifold of 3MLCT triplet states is first populated from high-lying singlet states within 26 ± 3 fs. ISC competes with an intricate internal conversion relaxation process within the singlet manifold to the lowest singlet state. Normal-mode anal. and principal component anal., combined with further dynamical simulations where the nuclei are frozen, unequivocally demonstrate that it is not only the high d. of states and the large spin-orbit couplings of the system that promote ISC. Instead, geometrical relaxation involving the nitrogen atoms is required to allow for state mixing and efficient triplet population transfer.
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  Electronic delocalization, charge transfer and hypochromism in the UV absorption spectrum of polyadenine unravelled by multiscale computations and quantitative wavefunction analysis
  Nogueira, Juan J.; Plasser, Felix; Gonzalez, Leticia
  Chemical Science (2017), 8 (8), 5682-5691CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
  The characterization of the electronically excited states of DNA strands populated upon solar UV light absorption is essential to unveil light-induced DNA damage and repair processes. We report a comprehensive anal. of the electronic properties of the UV spectrum of single-stranded polyadenine based on theor. calcns. that include excitations over eight nucleobases of the DNA strand and environmental effects by a multiscale quantum mechanics/mol. mechanics scheme, conformational sampling by mol. dynamics, and a meaningful interpretation of the electronic structure by quant. wavefunction anal. We show that electronic excitations are extended mainly over two nucleobases with addnl. important contributions of monomer-like excitations and excitons delocalized over three monomers. Half of the spectral intensity derives from locally excited and Frenkel exciton states, while states with partial charge-transfer character account for the other half and pure charge-transfer states represent only a minor contribution. The hypochromism obsd. when going from the isolated monomer to the strand occurs independently from delocalization and charge transfer and is instead explained by long-range environmental perturbations of the monomer states.
15. 15
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  van Stokkum, Ivo H. M.; Larsen, Delmar S.; van Grondelle, Rienk
  Biochimica et Biophysica Acta, Bioenergetics (2004), 1657 (2-3), 82-104CODEN: BBBEB4; ISSN:0005-2728. (Elsevier B.V.)
  A review. In biol./bioenergetics research the response of a complex system to an externally applied perturbation is often studied. Spectroscopic measurements at multiple wavelengths are used to monitor the kinetics. These time-resolved spectra are considered as an example of multiway data. In this paper, the methodol. for global and target anal. of time-resolved spectra is reviewed. To fully ext. the information from the overwhelming amt. of data, a model-based anal. is mandatory. This anal. is based upon assumptions regarding the measurement process and upon a physicochem. model for the complex system. This model is composed of building blocks representing scientific knowledge and assumptions. Building blocks are the instrument response function (IRF), the components of the system connected in a kinetic scheme, and anisotropy properties of the components. The combination of a model for the kinetics and for the spectra of the components results in a more powerful spectrotemporal model. The model parameters, like rate consts. and spectra, can be estd. from the data, thus providing a concise description of the complex system dynamics. This spectrotemporal modeling approach is illustrated with an elaborate case study of the ultrafast dynamics of the photoactive yellow protein.
19. 19
  Wu, G.; Boguslavskiy, A. E.; Schalk, O.; Schuurman, M. S.; Stolow, A. Ultrafast non-adiabatic dynamics of methyl substituted ethylenes: The π3s Rydberg state. J. Chem. Phys. 2011, 135, 164309, DOI: 10.1063/1.3652966
  19
  Ultrafast non-adiabatic dynamics of methyl substituted ethylenes: The π3s Rydberg state
  Wu, Guorong; Boguslavskiy, Andrey E.; Schalk, Oliver; Schuurman, Michael S.; Stolow, Albert
  Journal of Chemical Physics (2011), 135 (16), 164309/1-164309/10CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  Excited state unimol. reactions of some polyenes exhibit localization of their dynamics at a single ethylenic double bond. Here we present studies of the fundamental photophys. processes in the ethylene unit itself. Combined femtosecond time-resolved photoelectron spectroscopy (TRPES) and ab initio quantum chem. calcns. was applied to the study of excited state dynamics in cis-butene, trans-butene, trimethylethylene, and tetramethylethylene, following initial excitation to their resp. π3s Rydberg states. The wavelength dependence of the π3s Rydberg state dynamics of tetramethylethylene was investigated in more detail. The π3s Rydberg to ππ* valence state decay rate varies greatly with substituent: the 1,2-di- and tri-Me substituted ethylenes (cis-butene, trans-butene, and trimethylethylene) show an ultrafast decay (∼20 fs), whereas the fully methylated tetramethylethylene shows a decay rate of 2 to 4 orders of magnitude slower. These observations are rationalized in terms of topog. trends in the relevant potential energy surfaces, as found from ab initio calcns.: (1) the barrier between the π3s state and the ππ* state increases with increasing methylation, and (2) the π3s/ππ* min. energy conical intersection displaces monotonically away from the π3s Franck-Condon region with increasing methylation. The use of systematic methylation in combination with TRPES and ab initio computation is emerging as an important tool in discerning the excited state dynamics of unsatd. hydrocarbons. (c) 2011 American Institute of Physics.
20. 20
  Schalk, O.; Boguslavskiy, A. E.; Stolow, A. Substituent effects on dynamics at conical intersections: Cyclopentadienes. J. Phys. Chem. A 2010, 114, 4058– 4064, DOI: 10.1021/jp911286s
  20
  Substituent Effects on Dynamics at Conical Intersections: Cyclopentadienes
  Schalk, Oliver; Boguslavskiy, Andrey E.; Stolow, Albert
  Journal of Physical Chemistry A (2010), 114 (12), 4058-4064CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
  Substituent effects on dynamics at conical intersections are investigated by means of femtosecond time-resolved photoelectron spectroscopy for cyclopentadiene and its substituted analogs 1,2,3,4-tetramethylcyclopentadiene, 1,2,3,4,5-pentamethylcyclopentadiene, and 1,2,3,4-tetramethyl-5-propylcyclopentadiene. By UV excitation to the S2 (11B2) state, the influence of these substitutions on dynamics for the initially excited S2 (11B2) surface and the spectroscopically dark S1 (21A1) surface were investigated. We obsd. that the dynamics depend only on a small no. of specific vibrations. Whereas dynamics at the S2/S1-conical intersection are independent of substitution at the 5-position, internal conversion dynamics on the S1 (21A1) surface slow down as the inertia of the 5-substituent increases. Contrary to the expectations of simple models of radiationless transitions, an increasing d. of states does not lead to faster processes, suggesting that a true dynamical picture of vibrational motions at conical intersections will be required.
21. 21
  Stolow, A.; Bragg, A. E.; Neumark, D. M. Femtosecond time-resolved photoelectron spectroscopy. Chem. Rev. 2004, 104, 1719– 1758, DOI: 10.1021/cr020683w
  21
  Femtosecond Time-Resolved Photoelectron Spectroscopy
  Stolow, Albert; Bragg, Arthur E.; Neumark, Daniel M.
  Chemical Reviews (Washington, DC, United States) (2004), 104 (4), 1719-1757CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
  A review on time-resolved photoelectron spectroscopy as applied to the dynamics of gas-phase neutral and anionic mols. and clusters is given. TRPES and its variants are powerful, relatively new techniques that lend themselves to highly detailed time-resolved studies of inter- and intramol. dynamics. A special attention was paid to applications for studying a variety of fundamental photochem. and photophys. processes. Such subjects as photoionization, electronic and nuclear coupling,rotational wave packets are discussed.
22. 22
  Hertel, I. V.; Radloff, W. Ultrafast dynamics in isolated molecules and molecular clusters. Rep. Prog. Phys. 2006, 69, 1897, DOI: 10.1088/0034-4885/69/6/R06
  22
  Ultrafast dynamics in isolated molecules and molecular clusters
  Hertel, I. V.; Radloff, W.
  Reports on Progress in Physics (2006), 69 (6), 1897-2003CODEN: RPPHAG; ISSN:0034-4885. (Institute of Physics Publishing)
  A review. During the past decade the understanding of photo-induced ultrafast dynamics in mol. systems has improved at an unforeseen speed and a wealth of detailed insight into the fundamental processes has been obtained. This review summarizes our present knowledge on ultrafast dynamics in isolated mols. and mol. clusters evolving after excitation with femtosecond pulses as studied by pump-probe anal. in real time. Exptl. tools and methods as well as theor. models are described which have been developed to glean information on primary, ultrafast processes in photophysics, photochem. and photobiol. The relevant processes are explained by way of example-from wave packet dynamics in systems with a few atoms all the way to internal conversion via conical intersections in bio-chromophores. A systematic overview on characteristic systems follows, starting with diat. and including larger org. mols. as well as various types of mol. clusters, such as micro-solvated chromophore mols. For conciseness the focus is on mol. systems which remain unperturbed by the laser pulses-apart from the excitation and detection processes as such. Thus, only some aspects of controlling and manipulating mol. reactions by shaped and/or very intense laser pulses are discussed briefly for particularly instructive examples, illustrating the perspectives of this prospering field. The material presented in this review comprises some prototypical examples from earlier pioneering work but emphasizes studies from recent years and covers the most important and latest developments until Jan. 2006.
23. 23
  Kim, S. K.; Pedersen, S.; Zewail, A. H. Direct femtosecond observation of the transient intermediate in the α-cleavage reaction of (CH₃)₂CO to 2CH₃+CO: Resolving the issue of concertedness. J. Chem. Phys. 1995, 103, 477, DOI: 10.1063/1.469614
  23
  Direct femtosecond observation of the transient intermediate in the α-cleavage reaction of (CH3)2CO to 2CH3 + CO. Resolving the issue of concertedness
  Kim, Sang Kyu; Pedersen, Soren; Zewail, Ahmed H.
  Journal of Chemical Physics (1995), 103 (1), 477-80CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  For the elementary α-cleavage of acetone, we report the femtosecond resoln. of the intermediates using mass spectrometry. The results show the nonconcertedness of the reaction, provide the times for the primary and secondary C-C breakage, and indicate the role of electronic structure (σ*, antibonding impulse) and the vibrational motions involved.
24. 24
  Shibata, T.; Suzuki, T. Photofragment ion imaging with femtosecond laser pulses. Chem. Phys. Lett. 1996, 262, 115– 119, DOI: 10.1016/0009-2614(96)01024-X
  24
  Photofragment ion imaging with femtosecond laser pulses
  Shibata, Takeshi; Suzuki, Toshinori
  Chemical Physics Letters (1996), 262 (1,2), 115-119CODEN: CHPLBC; ISSN:0009-2614. (Elsevier)
  Photofragment ion imaging with femtosecond real-time clocking has been applied to α-bond cleavage from 1(n, π*) states of acetyl chloride and acetone. It is shown that dissocn. occurs within the time comparable with laser pulse duration of 200 fs in acetyl chloride, whereas the reaction time is longer than 15 ps in acetone. The dissocn. in the neutral state and the fragmentation in the ionic state are discriminated from images of photofragment ion distributions.
25. 25
  Buzza, S. A.; Snyder, E. M.; Castleman, A. W. Further direct evidence for stepwise dissociation of acetone and acetone clusters. J. Chem. Phys. 1996, 104, 5040, DOI: 10.1063/1.471133
  25
  Further direct evidence for stepwise dissociation of acetone and acetone clusters
  Buzza, S. A.; Snyder, E. M.; Castleman, A. W., Jr.
  Journal of Chemical Physics (1996), 104 (13), 5040-7CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  The (pre)dissocn. of acetone and acetone clusters after excitation to states corresponding to upper {S1,T1} and 3s Rydberg states of the acetone monomer are investigated through femtosecond pump-probe expts. coupled with mol. beam time-of-flight mass spectrometry techniques. Upon excitation to either state, [(CH3)2CO]n* dissocs. rapidly. Acetyl fragments, [(CH3)2CO]n-1CH3CO+ may arise from ionization of an excited species formed by (pre)dissocn. of intact precursors or by dissocn. after the intact species has been ionized. The method employed to sep,. these two channels is discussed herein; the resulting transients are fit to a kinetic model to elucidate intermediate lifetimes and dissocn. mechanisms. The present expts. establish that a stepwise dissocn. mechanism is operative upon excitation to the 3s Rydberg state for the acetone monomer and dimer, with their corresponding acetyl fragments having lifetimes on the order of picoseconds. Larger cluster species, [(CH3)2CO]n (n > 2), do not exhibit the predissocn. behavior evident in the monomer and dimer. Conversely, dissocn. upon excitation to the {S1,T1} state exhibits an initial loss of a Me unit, with the acetyl intermediate being considerably more stable than those created by dissocn. of acetone from higher lying states. A strong dependence on the internal energy available after the dissocn. event is noted.
26. 26
  Rusteika, N.; Møller, K. B.; Sølling, T. I. New insights on the photodynamics of acetone excited with 253–288nm femtosecond pulses. Chem. Phys. Lett. 2008, 461, 193– 197, DOI: 10.1016/j.cplett.2008.06.079
  26
  New insights on the photodynamics of acetone excited with 253-288 nm femtosecond pulses
  Rusteika, Nerijus; Moller, Klaus B.; Solling, Theis I.
  Chemical Physics Letters (2008), 461 (4-6), 193-197CODEN: CHPLBC; ISSN:0009-2614. (Elsevier B.V.)
  The authors have performed time-resolved photoelectron spectroscopy and mass spectrometry expts. to address the dynamics that result when gaseous acetone mols. are excited with femtosecond pulses in the 253-288 nm wavelength range. There are several previous examples of time-resolved mass spectrometry expts. and the authors results are in line with previously published data. However, the results of the photoelectron spectroscopy expts. allow one to show that the ultrafast dynamics related to the S1 state can be attributed entirely to photophys. processes. In essence, the dynamics that is induced by a one-photon excitation is governed by the motion out of the Franck-Condon region on the S1 surface to the relaxed geometry in less than 30 fs. The relaxed S1 species does not decay in 100 ps and actual C-C bond breakage must take place on a longer time scale.
27. 27
  Hüter, O.; Temps, F. Ultrafast α–CC bond cleavage of acetone upon excitation to 3p and 3d Rydberg states by femtosecond time-resolved photoelectron imaging. J. Chem. Phys. 2016, 145, 214312, DOI: 10.1063/1.4971243
  27
  Ultrafast α -CC bond cleavage of acetone upon excitation to 3p and 3d Rydberg states by femtosecond time-resolved photoelectron imaging
  Hueter, O.; Temps, F.
  Journal of Chemical Physics (2016), 145 (21), 214312/1-214312/12CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  The radiationless electronic relaxation and α -CC bond fission dynamics of jet-cooled acetone in the S1 (nπ*) state and in high-lying 3p and 3d Rydberg states have been investigated by femtosecond time-resolved mass spectrometry and photoelectron imaging. The S1 state was accessed by absorption of a UV pump photon at selected wavelengths between λ = 320 and 250 nm. The obsd. acetone mass signals and the S1 photoelectron band decayed on sub-picosecond time scales, consistent with a recently proposed ultrafast structural relaxation of the mols. in the S1 state away from the Franck-Condon probe window. No direct signatures could be obsd. by the expts. for CC dissocn. on the S1 potential energy hypersurface in up to 1 ns. The obsd. acetyl mass signals at all pump wavelengths turned out to be assocd. with absorption by the mols. of one or more addnl. pump and/or probe photons. In particular, absorption of a second UV pump photon by the S1 (nπ*) state was found to populate a series of high-lying states belonging to the n = 3 Rydberg manifold. The resp. transitions are favored by much larger cross sections compared to the S1 ← S0 transition. The characteristic energies revealed by the photoelectron images allowed for assignments to the 3p and 3dyz states. At two-photon excitation energies higher than 8.1 eV, an ultrafast reaction pathway for breaking the α -CC bond in 50-90 fs via the 3dyz Rydberg state and the elusive ππ* state was obsd., explaining the formation of acetyl radicals after femtosecond laser excitation of acetone at these wavelengths. (c) 2016 American Institute of Physics.
28. 28
  Maierhofer, P.; Bainschab, M.; Thaler, B.; Heim, P.; Ernst, W. E.; Koch, M. Disentangling multichannel photodissociation dynamics in acetone by time-resolved photoelectron-photoion coincidence spectroscopy. J. Phys. Chem. A 2016, 120, 6418– 6423, DOI: 10.1021/acs.jpca.6b07238
  28
  Disentangling Multichannel Photodissociation Dynamics in Acetone by Time-Resolved Photoelectron-Photoion Coincidence Spectroscopy
  Maierhofer, Paul; Bainschab, Markus; Thaler, Bernhard; Heim, Pascal; Ernst, Wolfgang E.; Koch, Markus
  Journal of Physical Chemistry A (2016), 120 (32), 6418-6423CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
  For the study of photoinduced dynamics in mols. with time-resolved pump-probe photoionization spectroscopy, it is essential to obtain unequivocal information about the fragmentation behavior induced by the laser pulses. The authors present time-resolved photoelectron-photoion coincidence (PEPICO) expts. to study the excited-state dynamics of isolated acetone mols. triggered by 2-photon (269 nm) excitation. In the complex situation of different relaxation pathways, the authors unambiguously identify three distinct pump-probe ionization channels. The high selectivity of PEPICO detection allows one to observe the fragmentation behavior and to follow the time evolution of each channel sep. For channels leading to fragment ions, the authors quant. obtain the fragment-to-parent branching ratio and are able to det. exptl. whether dissocn. occurs in the neutral mol. or in the parent ion. These results highlight the importance of coincidence detection for the interpretation of time-resolved photochem. relaxation and dissocn. studies if multiple pathways are present.
29. 29
  Couch, D. E.; Kapteyn, H. C.; Murnane, M. M.; Peters, W. K. Uncovering highly-excited state mixing in acetone using ultrafast VUV pulses and coincidence imaging techniques. J. Phys. Chem. A 2017, 121, 2361– 2366, DOI: 10.1021/acs.jpca.7b01112
  29
  Uncovering Highly-Excited State Mixing in Acetone Using Ultrafast VUV Pulses and Coincidence Imaging Techniques
  Couch, David E.; Kapteyn, Henry C.; Murnane, Margaret M.; Peters, William K.
  Journal of Physical Chemistry A (2017), 121 (12), 2361-2366CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
  Understanding the ultrafast dynamics of highly excited electronic states of small mols. is crit. for a better understanding of atm. and astrophys. processes, as well as for designing coherent control strategies for manipulating chem. dynamics. In highly excited states, nonadiabatic coupling, electron-electron interactions, and the high d. of states govern dynamics. However, these states are computationally and exptl. challenging to access. Fortunately, new sources of ultrafast vacuum UV pulses, in combination with electron-ion coincidence spectroscopies, provide new tools to unravel the complex electronic landscape. Here the authors report time-resolved photoelectron-photoion coincidence expts. using 8 eV pump photons to study the highly excited states of acetone. The authors uncover for the first time direct evidence that the resulting excited state consists of a mixt. of both ny → 3p and π → π* character, which decays with a time const. of 330 fs. In the future, this approach can inform models of VUV photochem. and aid in designing coherent control strategies for manipulating chem. reactions.
30. 30
  Uenishi, R.; Horio, T.; Suzuki, T. Time-resolved photoelectron imaging of acetone with 9.3 eV photoexcitation. J. Phys. Chem. A 2019, 123, 6848– 6853, DOI: 10.1021/acs.jpca.9b05179
  30
  Time-Resolved Photoelectron Imaging of Acetone with 9.3 eV Photoexcitation
  Uenishi, Ryuta; Horio, Takuya; Suzuki, Toshinori
  Journal of Physical Chemistry A (2019), 123 (32), 6848-6853CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
  Ultrafast electronic relaxation following 9.3 eV photoexcitation of gaseous acetone was investigated with time-resolved photoelectron imaging spectroscopy. An intense photoionization signal due to a transition from the 41A1(π,π*) state to the D1(π-1) cationic state diminishes within 50 fs, owing to vibrational wave packet motion leaving our observation energy window. Addnl. photoionization signals were assigned to transitions from Rydberg states with principal quantum nos. of 3-8 to the D0(n-1) cationic state, created by strong vibronic couplings with the bright 41A1(π,π*) state. The deactivation processes of the 41A1(π,π*) and Rydberg states are discussed based on their decay profiles obtained from a time-energy map of photoelectron kinetic energy distributions.
31. 31
  Koch, M.; Heim, P.; Thaler, B.; Kitzler, M.; Ernst, W. E. Direct observation of a photochemical activation energy: a case study of acetone photodissociation. J. Phys. B: At., Mol. Opt. Phys. 2017, 50, 125102, DOI: 10.1088/1361-6455/aa6a71
  31
  Direct observation of a photochemical activation energy: a case study of acetone photodissociation
  Koch, Markus; Heim, Pascal; Thaler, Bernhard; Kitzler, Markus; Ernst, Wolfgang E.
  Journal of Physics B: Atomic, Molecular and Optical Physics (2017), 50 (12), 125102/1-125102/8CODEN: JPAPEH; ISSN:0953-4075. (IOP Publishing Ltd.)
  The ability to observe and quantify the conversion of electronic potential energy to vibrational kinetic energy in a mol. after photoexcitation is essential to understand and control the outcome of photoinduced mol. fragmentation. We exploit the high selectivity of photoelectron-photoion coincidence detection to distinguish different relaxation channels and observe the fragmentation behavior of each channel. We demonstrate the concept by investigating the fragmentation of gas-phase acetone mols. initiated by three-photon excitation to high lying Rydberg states between 9.0 and 9.5 eV above the ground state. By applying variations of the photon energy, pulse duration (100-200 fs) and pulse energy, we are able to fully characterize the fragmentation process. Rydberg states between 5s and 8s are populated, which undergo ultrafast internal conversion to lower states. The corresponding nonadiabatic dynamics in the neutral mol. cause the conversion of electronic to vibrational energy, leading to fragmentation. Our scheme allows us to directly measure the activation energy for fragmentation of acetone to an acetyl ion and a Me radical, which we det. to be (0.79±0.04) eV. Longer laser pulses result in an increased fragment-to-parent ratio, representing a higher probability for relaxation because the relaxation time consts. are comparable to the pulse duration. Upon excitation to Rydberg states at 9.5 eV we surprisingly observe reduced fragmentation, although ∼2 eV are coupled into vibrational energy, indicating that different relaxation pathways become active, which results in a change of the redistribution of vibrational energy within the mol. Fragmentation due to subsequent excitation of the cation is found to play a minor role.
32. 32
  Sølling, T. I.; Diau, E. W.-G.; Kötting, C.; De Feyter, S.; Zewail, A. H. Femtochemistry of Norrish Type I reactions: IV. Highly excited ketones—Experimental. ChemPhysChem 2002, 3, 79– 97, DOI: 10.1002/1439-7641(20020118)3:1<79::AID-CPHC79>3.0.CO;2-#
  32
  Femtochemistry of Norrish type-I reactions: IV. Highly excited ketones-experimental
  Solling, Theis I.; Diau, Eric W.-G.; Kotting, Carsten; De Feyter, Steven; Zewail, Ahmed H.
  ChemPhysChem (2002), 3 (1), 79-97CODEN: CPCHFT; ISSN:1439-4235. (Wiley-VCH Verlag GmbH)
  The two α-CC bonds in a series of cyclic and acyclic ketone were obsd. to cleave in a stepwise and nonstatistical manner. The first bond breakage occurs in 60 - 290 fs and leads to a linear excited-state acyl radical. The further decompn. of this species is up to an order of magnitude slower. The initial configuration of the acyl radical dets. whether the second bond breakage proceeds via a slow (blue) or a fast (red) trajectory.
33. 33
  Thakur, S. N.; Guo, D.; Kundu, T.; Goodman, L. Two-photon photoacoustic spectroscopy of acetone 3p Rydberg states. Chem. Phys. Lett. 1992, 199, 335– 340, DOI: 10.1016/0009-2614(92)80128-X
  33
  Two-photon photoacoustic spectroscopy of acetone 3p Rydberg states
  Thakur, Surya N.; Guo, Ding; Kundu, Tapanendu; Goodman, Lionel
  Chemical Physics Letters (1992), 199 (3-4), 335-40CODEN: CHPLBC; ISSN:0009-2614.
  Two-photon photoacoustic spectra of acetone-h6 and -d6 were recorded using a pulsed laser in the 3p←n Rydberg transition region (332.2-338.7 nm for two-photon excitation). Comparison of the acetone-h6 and -d6 photoacoustic and two-photon resonance enhanced multiphoton ionization spectra shows an intensity reversal between the (3py←n)1A1 and (3px←n)1A2 transition origins. The dramatic increase in the 1A1 state - and to a lesser extent for the 1B2 state - photoacoustic signals requires efficient radiationless/dissociative channels for these states, not present for 1A2. The intensity effects are interpreted through the 1A1 state having substantial π*←π valence character in contrast to almost pure Rydberg character for the 1A2 state.
34. 34
  Xing, X.; McDiarmid, R.; Philis, J. G.; Goodman, L. Vibrational assignments in the 3p Rydberg states of acetone. J. Chem. Phys. 1993, 99, 7565– 7573, DOI: 10.1063/1.465686
  34
  Vibrational assignments in the 3p Rydberg states of acetone
  Xing, Xing; McDiarmid, Ruth; Philis, John G.; Goodman, Lionel
  Journal of Chemical Physics (1993), 99 (10), 7565-73CODEN: JCPSA6; ISSN:0021-9606.
  The 2 and 3 photon resonantly enhanced multiphoton ionization spectra of the 3p Rydberg ← ~X transitions of acetone and acetone-d6 were remeasured and reanalyzed. Seven of the 8 a1 and 1 b1 vibrational modes were assigned. From these assigned fundamental frequencies the anomalous isotope shift of the origin of the A1 transition was rationalized, the contribution of the nonbonding electrons to the scissors force const. was demonstrated, and a location for the A1 ππ* valence excited transition was proposed.
35. 35
  Merchán, M.; Roos, B. O.; McDiarmid, R.; Xing, X. A combined theoretical and experimental determination of the electronic spectrum of acetone. J. Chem. Phys. 1996, 104, 1791, DOI: 10.1063/1.470976
  35
  A combined theoretical and experimental determination of the electronic spectrum of acetone
  Merchan, Manuela; Roos, Bjorn O.; McDiarmid, ruth; Xing, Xing
  Journal of Chemical Physics (1996), 104 (5), 1791-804CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  A combined ab initio and exptl. investigation has been performed of the main features of the electronic spectrum of acetone. Vertical transition energies have been calcd. from the ground to the ny → π*, π→π*, and the n = 3 Rydberg states. In addn., the 1A1 energy surfaces have been studied as functions of the CO bond length. The 1A1 3p and 3d states were found to be heavily perturbed by the π→π* state. Resonant multiphoton ionization and polarization-selected photoacoustic spectra of acetone have been measured and obsd. transitions were assigned on internal criteria. The calcd. vertical transition energies to the ny→π* and all Rydberg states were found to be in agreement with expt. This includes the 3s-, all three 3p-, and the A1, B1, and B2 3d-Rydberg states. By contrast, there is little agreement between the calcd. and exptl. relative intensities of the A1 and B2 3d-Rydberg transitions. In addn., anomalously intense high vibrational overtone bands of one of the 3p-Rydberg transitions have been obsd. These results confirm the strong perturbation of the 3p-Rydberg states by the π→π* state found in the theor. calcn. and support the calcd. position of this unobserved state.
36. 36
  ter Steege, D. H. A.; Wirtz, A. C.; Buma, W. J. Vibronic coupling in excited states of acetone. J. Chem. Phys. 2002, 116, 547– 560, DOI: 10.1063/1.1423946
  36
  Vibronic coupling in excited states of acetone
  ter Steege, D. H. A.; Wirtz, A. C.; Buma, W. J.
  Journal of Chemical Physics (2002), 116 (2), 547-560CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  Photoelectron spectroscopy of Rydberg states of acetone-h6 and -d6 populated by two- or three-photon excitation was employed to unravel the vibronic description of excited-state levels. For the 3p Rydberg states vibronic transitions were reanalyzed, leading to various reassignments and the observation of hitherto non-reported transitions. In addn., several ionic vibrational frequencies could be detd. At higher excitation energies previously identified, and in the present study newly identified, members of two Rydberg series were characterized. The ns Rydberg series was explored up to the 8s state, the nd series up to the 7d state. Based upon the unambiguous assignments of vibronic character that the authors obtain for excited-state levels, various valence-Rydberg and Rydberg-Rydberg vibronic coupling pathways come to light and are analyzed.
37. 37
  McDiarmid, R.; Xing, X. Nonadiabatic coupling of the 3p Rydberg and ππ* valence states of acetone. J. Chem. Phys. 1997, 107, 675– 679, DOI: 10.1063/1.475152
  37
  Nonadiabatic coupling of the 3p Rydberg and ππ* valence states of acetone
  McDiarmid, Ruth; Xing, Xing
  Journal of Chemical Physics (1997), 107 (3), 675-679CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  The 3p Rydberg region of the spectra of acetone and acetone-d6 was studied by resonantly enhanced multiphoton ionization and photoacoustic spectroscopies. Differences between the spectra of cold and room temp. samples, between REMPI and PA spectral measurements, and between the laser power dependences of the different 3p ← ~X origins arise from a nonadiabatic coupling of the A1 3p Rydberg and A1 ππ* states of acetone. The coupling is proposed to arise from a seam of conical intersection between these 2 A1 states on the CO stretch-C2CO pyramidalization plane. An analogous seam is proposed to exist between the A1 3d Rydberg and A1 ππ* states.
38. 38
  Mai, S.; Richter, M.; Heindl, M.; Menger, M. F. S. J.; Atkins, A. J.; Ruckenbauer, M.; Plasser, F.; Oppel, M.; Marquetand, P.; González, L. SHARC2.0: Surface Hopping Including Arbitrary Couplings – program package for non-adiabatic dynamics; sharc-md.org, 2018.
  There is no corresponding record for this reference.
39. 39
  Plasser, F.; Gómez, S.; Mai, S.; González, L. Highly efficient surface hopping dynamics using a linear vibronic coupling model. Phys. Chem. Chem. Phys. 2019, 21, 57– 69, DOI: 10.1039/C8CP05662E
  39
  Highly efficient surface hopping dynamics using a linear vibronic coupling model
  Plasser, Felix; Gomez, Sandra; Menger, Maximilian F. S. J.; Mai, Sebastian; Gonzalez, Leticia
  Physical Chemistry Chemical Physics (2019), 21 (1), 57-69CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
  We report an implementation of the linear vibronic coupling (LVC) model within the surface hopping dynamics approach and present utilities for parameterizing this model in a blackbox fashion. This results in an extremely efficient method to obtain qual. and even semi-quant. information about the photodynamical behavior of a mol., and provides a new route toward benchmarking the results of surface hopping computations. The merits and applicability of the method are demonstrated in a no. of applications. First, the method is applied to the SO2 mol. showing that it is possible to compute its absorption spectrum beyond the Condon approxn., and that all the main features and timescales of previous on-the-fly dynamics simulations of intersystem crossing are reproduced while reducing the computational effort by three orders of magnitude. The dynamics results are benchmarked against exact wavepacket propagations on the same LVC potentials and against a variation of the electronic structure level. Four addnl. test cases are presented to exemplify the broader applicability of the model. The photodynamics of the isomeric adenine and 2-aminopurine mols. are studied and it is shown that the LVC model correctly predicts ultrafast decay in the former and an extended excited-state lifetime in the latter. Futhermore, the method correctly predicts ultrafast intersystem crossing in the modified nucleobase 2-thiocytosine and its absence in 5-azacytosine while it fails to describe the ultrafast internal conversion to the ground state in the latter.
40. 40
  Subotnik, J. E.; Jain, A.; Landry, B.; Petit, A.; Ouyang, W.; Bellonzi, N. Understanding the surface hopping view of electronic transitions and decoherence. Annu. Rev. Phys. Chem. 2016, 67, 387– 417, DOI: 10.1146/annurev-physchem-040215-112245
  40
  Understanding the Surface Hopping View of Electronic Transitions and Decoherence
  Subotnik, Joseph E.; Jain, Amber; Landry, Brian; Petit, Andrew; Ouyang, Wenjun; Bellonzi, Nicole
  Annual Review of Physical Chemistry (2016), 67 (), 387-417CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews)
  We present a current, up-to-date review of the surface hopping methodol. for solving nonadiabatic problems, 25 years after Tully published the fewest switches surface hopping algorithm. After reviewing the original motivation for and failures of the algorithm, we give a detailed examn. of modern advances, focusing on both theor. and practical issues. We highlight how one can partially derive surface hopping from the Schrodinger equation in the adiabatic basis, how one can change basis within the surface hopping algorithm, and how one should understand and apply the notions of decoherence and wavepacket bifurcation. The question of time reversibility and detailed balance is also examd. at length. Recent applications to photoexcited conjugated polymers are discussed briefly.
41. 41
  Wang, L.; Akimov, A.; Prezhdo, O. V. Recent progress in surface hopping: 2011–2015. J. Phys. Chem. Lett. 2016, 7, 2100– 2112, DOI: 10.1021/acs.jpclett.6b00710
  41
  Recent Progress in Surface Hopping: 2011-2015
  Wang, Linjun; Akimov, Alexey; Prezhdo, Oleg V.
  Journal of Physical Chemistry Letters (2016), 7 (11), 2100-2112CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
  A review. Developed 25 years ago, Tully's fewest switches surface hopping (FSSH) has proven to be the most popular approach for simulating quantum-classical dynamics in a broad variety of systems, ranging from the gas phase, to the liq. and solid phases, to biol. and nanoscale materials. FSSH is widely adopted as the fundamental platform to introduce modifications as needed. Significant progress has been made recently to enhance the accuracy and efficiency of the surface hopping technique. Various limitations of the std. FSSH-assocd. with quantum nuclear effects, interference and decoherence, trivial or "unavoided" crossings, superexchange, and representation dependence-have been lifted. These advances are needed to allow one to treat many important phenomena in chem., physics, materials, and related disciplines. Examples include charge transport in extended systems such as org. solids, singlet fission in mol. aggregates, Auger-type exciton multiplication, recombination and relaxation in quantum dots and other nanoscale materials, Auger-assisted charge transfer, nonradiative luminescence quenching, and electron-hole recombination. This Perspective summarizes recent advances in the surface hopping formulation of nonadiabatic dynamics and provides an outlook on the future of surface hopping.
42. 42
  Plasser, F.; Mai, S.; Fumanal, M.; Gindensperger, E.; Daniel, C.; González, L. Strong influence of decoherence corrections and momentum rescaling in surface hopping dynamics of transition metal complexes. J. Chem. Theory Comput. 2019, 15, 5031– 5045, DOI: 10.1021/acs.jctc.9b00525
  42
  Strong Influence of Decoherence Corrections and Momentum Rescaling in Surface Hopping Dynamics of Transition Metal Complexes
  Plasser, Felix; Mai, Sebastian; Fumanal, Maria; Gindensperger, Etienne; Daniel, Chantal; Gonzalez, Leticia
  Journal of Chemical Theory and Computation (2019), 15 (9), 5031-5045CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)
  The reliability of different parameters in the surface hopping method is assessed for a vibronic coupling model of a challenging transition metal complex, where a large no. of electronic states of different multiplicities are met within a small energy range. In particular, the effect of two decoherence correction schemes and of various strategies for momentum rescaling and treating frustrating hops during the dynamics is investigated and compared against an accurate quantum dynamics simulation. The results show that surface hopping is generally able to reproduce the ref. but also that small differences in the protocol used can strongly affect the results. We find a clear preference for momentum rescaling along only one degree of freedom, using either the nonadiabatic coupling or the gradient difference vector, and trace this effect back to an enhanced no. of frustrated hops. Furthermore, reflection of the momentum after frustrated hops is shown to work better than to ignore the process completely. The study also highlights the importance of the decoherence correction but neither of the two methods employed, energy based decoherence or augmented fewest switches surface hopping, performs completely satisfactory and we trace this effect back to a lack of size-consistency. Finally, the effect of different methods for analyzing the populations is highlighted. More generally, the study emphasizes the importance of the often neglected parameters in surface hopping and shows that there is still need for simple, robust, and generally applicable correction schemes.
43. 43
  Kruit, P.; Read, F. Magnetic field paralleliser for 2π electron-spectrometer and electron-image magnifier. J. Phys. E: Sci. Instrum. 1983, 16, 313, DOI: 10.1088/0022-3735/16/4/016
  43
  Magnetic field parallelizer for 2π electron spectrometer and electron-image magnifier
  Kruit, P.; Read, F. H.
  Journal of Physics E: Scientific Instruments (1983), 16 (4), 313-24CODEN: JPSIAE; ISSN:0022-3735.
  An electron spectrometer is described in which electrons originally emitted over 2π steradians from a region of small vol. are formed into a beam of half-angle 2°. The instrument uses a magnetic field that diverges from 1 to 10-3T. Parallelized electrons of energy 0-3 eV were measured with a time-of-flight technique, and gave energy resolns. as low as 15 meV. Addn. of an elec. field near the source permits selection of a solid angle of 0-4π steradians. The device can also act as an electron-image magnifier, giving a spatial resoln. of a few μm in the source plane.
44. 44
  Fumanal, M.; Plasser, F.; Mai, S.; Daniel, C.; Gindensperger, E. Interstate vibronic coupling constants between electronic excited states for complex molecules. J. Chem. Phys. 2018, 148, 124119, DOI: 10.1063/1.5022760
  44
  Interstate vibronic coupling constants between electronic excited states for complex molecules
  Fumanal, Maria; Plasser, Felix; Mai, Sebastian; Daniel, Chantal; Gindensperger, Etienne
  Journal of Chemical Physics (2018), 148 (12), 124119/1-124119/11CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  In the construction of diabatic vibronic Hamiltonians for quantum dynamics in the excited-state manifold of mols., the coupling consts. are often extd. solely from information on the excited-state energies. Here, a new protocol is applied to get access to the interstate vibronic coupling consts. at the time-dependent d. functional theory level through the overlap integrals between excited-state adiabatic auxiliary wavefunctions. We discuss the advantages of such method and its potential for future applications to address complex systems, in particular, those where multiple electronic states are energetically closely lying and interact. We apply the protocol to the study of prototype rhenium carbonyl complexes [Re(CO)3(N,N)(L)]n+ for which non-adiabatic quantum dynamics within the linear vibronic coupling model and including spin-orbit coupling have been reported recently. (c) 2018 American Institute of Physics.
45. 45
  Dreuw, A.; Wormit, M. The algebraic diagrammatic construction scheme for the polarization propagator for the calculation of excited states. WIREs Comput. Mol. Sci. 2015, 5, 82– 95, DOI: 10.1002/wcms.1206
  45
  The algebraic diagrammatic construction scheme for the polarization propagator for the calculation of excited states
  Dreuw, Andreas; Wormit, Michael
  Wiley Interdisciplinary Reviews: Computational Molecular Science (2015), 5 (1), 82-95CODEN: WIRCAH; ISSN:1759-0884. (Wiley-Blackwell)
  The algebraic diagrammatic construction (ADC) scheme for the polarization propagator provides a series of ab initio methods for the calcn. of excited states based on perturbation theory. In recent years, the second-order ADC(2) scheme has attracted attention in the computational chem. community because of its reliable accuracy and reasonable computational effort in the calcn. of predominantly singly excited states. Owing to their size-consistency, ADC methods are suited for the investigation of large mols. In addn., their Hermitian structure and the availability of the intermediate state representation (ISR) allow for straightforward computation of excited-state properties. Recently, an efficient implementation of ADC(3) has been reported, and its high accuracy for typical valence excited states of org. chromophores has been demonstrated. In this review, the origin of ADC-based excited-state methods in propagator theory is described, and an intuitive route for the derivation of algebraic expressions via the ISR is outlined and comparison to other excited-state methods is made. Existing computer codes and implemented ADC variants are reviewed, but most importantly the accuracy and limits of different ADC schemes are critically examd. WIREs Comput Mol Sci 2015, 5:82-95. doi: 10.1002/wcms.1206 Conflict of interest: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the .
46. 46
  Dunning, T. H. Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen. J. Chem. Phys. 1989, 90, 1007– 1023, DOI: 10.1063/1.456153
  46
  Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen
  Dunning, Thom H., Jr.
  Journal of Chemical Physics (1989), 90 (2), 1007-23CODEN: JCPSA6; ISSN:0021-9606.
  Guided by the calcns. on oxygen in the literature, basis sets for use in correlated at. and mol. calcns. were developed for all of the first row atoms from boron through neon, and for hydrogen. As in the oxygen atom calcns., the incremental energy lowerings, due to the addn. of correlating functions, fall into distinct groups. This leads to the concept of correlation-consistent basis sets, i.e., sets which include all functions in a given group as well as all functions in any higher groups. Correlation-consistent sets are given for all of the atoms considered. The most accurate sets detd. in this way, [5s4p3d2f1g], consistently yield 99% of the correlation energy obtained with the corresponding at.-natural-orbital sets, even though the latter contains 50% more primitive functions and twice as many primitive polarization functions. It is estd. that this set yields 94-97% of the total (HF + 1 + 2) correlation energy for the atoms neon through boron.
47. 47
  Kaufmann, K.; Baumeister, W.; Jungen, M. Universal Gaussian basis sets for an optimum representation of Rydberg and continuum wavefunctions. J. Phys. B: At., Mol. Opt. Phys. 1989, 22, 2223, DOI: 10.1088/0953-4075/22/14/007
  47
  Universal Gaussian basis sets for an optimum representation of Rydberg and continuum wave functions
  Kaufmann, Karl; Baumeister, Werner; Jungen, Martin
  Journal of Physics B: Atomic, Molecular and Optical Physics (1989), 22 (14), 2223-40CODEN: JPAPEH; ISSN:0953-4075.
  A universal-Gaussian-basis-set concept for the calcn. of Rydberg and continuum states by pure L2 methods is presented. It is based on the generation of optimized sequences of Gaussian exponents by maximizing the overlap with a series of Slater-type functions characterized by a const. exponent and a variable principal quantum no. In this way, linear combinations of Gaussian basis functions can be found which are ideally suited to imitate Laguerre-Slater functions. It is thus possible to obtain optimum representations of Rydberg orbitals or of complete orthonormal systems of Laguerre functions playing an important role in the L2 expansion of continuum functions. The basis sets were tested with the hydrogen atom. The effectiveness of the basis is illustrated by the calcn. of quantum defects assocd. with the s, p and d Rydberg series of the alkali metal atoms Li and Na. The phase shifts detd. in the ionization continua of these systems nicely fit the series below the ionization limit, as is finally demonstrated by an Edlen plot.
48. 48
  TURBOMOLE V7.0, A development of University of Karlsruhe and Forschungszentrum Karlsruhe GmbH, 2015.
  There is no corresponding record for this reference.
49. 49
  Granucci, G.; Persico, M.; Toniolo, A. Direct semiclassical simulation of photochemical processes with semiempirical wave functions. J. Chem. Phys. 2001, 114, 10608– 10615, DOI: 10.1063/1.1376633
  49
  Direct semiclassical simulation of photochemical processes with semiempirical wave functions
  Granucci, G.; Persico, M.; Toniolo, A.
  Journal of Chemical Physics (2001), 114 (24), 10608-10615CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  The authors describe a new method for the simulation of excited state dynamics, based on classical trajectories and surface hopping, with direct semiempirical calcn. of the electronic wave functions and potential energy surfaces (DTSH method). Semiempirical self-consistent-field MOs (SCF MO's) are computed with geometry-dependent occupation nos., in order to ensure correct homolytic dissocn., fragment orbital degeneracy, and partial optimization of the lowest virtuals. Electronic wave functions are of the MO active space CI type, for which analytic energy gradients have been implemented. The time-dependent electronic wave function is propagated by means of a local diabatization algorithm which is inherently stable also in the case of surface crossings. The method is tested for the problem of excited ethylene nonadiabatic dynamics, and the results are compared with recent quantum mech. calcns.
50. 50
  Granucci, G.; Persico, M. Critical appraisal of the fewest switches algorithm for surface hopping. J. Chem. Phys. 2007, 126, 134114, DOI: 10.1063/1.2715585
  50
  Critical appraisal of the fewest switches algorithm for surface hopping
  Granucci, Giovanni; Persico, Maurizio
  Journal of Chemical Physics (2007), 126 (13), 134114/1-134114/11CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
  In this paper the authors address the problem of internal consistency in trajectory surface hopping methods, i.e., the requirement that the fraction of trajectories running on each electronic state equals the probabilities computed by the electronic time-dependent Schroedinger equation, after averaging over all trajectories. They derive a formula for the hopping probability in Tully's "fewest switches" spirit that would yield a rigorously consistent treatment. They show the relationship of Tully's widely used surface hopping algorithm with the "exact" prescription that cannot be applied when running each trajectory independently. They also bring out the connection of the consistency problem with the coherent propagation of the electronic wave function and the artifacts caused by coherent Rabi-type oscillations of the state probabilities in weak coupling regimes. A real mol. (azobenzene) and two ad hoc models serve as examples to illustrate the above theor. arguments. Following a proposal by Truhlar's group [Zhu [et al.], J. Chem. Phys. 121, 7658 (2004) Zhu [et al.], J. Chem. Theory Comput. 1, 527 (2005)], they apply a decoherence correction to the state probabilities, in conjunction with Tully's algorithm, and they obtain satisfactory results in terms of internal consistency and of agreement with the outcomes of quantum wave packet calcns.
Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpclett.9b03462.
- Discussion and derivation of the fitting functions, experimental details regarding energy calibration, additional experimental results, additional computational details, and computational results (PDF)
- V₀ data in SHARC format (TXT)
- LVC parameters in SHARC format (TXT)
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Revealing Ultrafast Population Transfer between Nearly Degenerate Electronic States
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Revealing Ultrafast Population Transfer between Nearly Degenerate Electronic States
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