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Single-Color Isomer-Resolved Spectroscopy

  • Grite L. Abma
    Grite L. Abma
    Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
    More by Grite L. Abma
  • , 
  • Dries Kleuskens
    Dries Kleuskens
    Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
    More by Dries Kleuskens
  • , 
  • Siwen Wang
    Siwen Wang
    Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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  • , 
  • Michiel Balster
    Michiel Balster
    Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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  • , 
  • Andre van Roij
    Andre van Roij
    Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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  • Niek Janssen
    Niek Janssen
    Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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  • , and 
  • Daniel A. Horke*
    Daniel A. Horke
    Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
    *E-mail: [email protected]
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    Orcidhttps://orcid.org/0000-0002-9862-8108
Cite this: J. Phys. Chem. A 2022, 126, 23, 3811–3815
Publication Date (Web):June 1, 2022
https://doi.org/10.1021/acs.jpca.2c02277

Copyright © 2022 The Authors. Published by American Chemical Society. This publication is licensed under

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Abstract

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Structural isomers, such as conformers or tautomers, are of significant importance across chemistry and biology, as they can have different functionalities. In gas-phase experiments using molecular beams, formation of many different isomers cannot be prevented, and their presence significantly complicates the assignment of spectral lines. Current isomer-resolved spectroscopic techniques heavily rely on theoretical calculations or make use of elaborate double-resonance schemes. We show here that isomer-resolved spectroscopy can also be performed using a single tunable laser. In particular, we demonstrate single-color isomer-resolved spectroscopy by utilizing electrostatic deflection to spatially separate the isomers. We show that for 3-aminophenol we can spatially separate the syn and anti conformers and use these pure samples to perform high-resolution REMPI spectroscopy, making the assignment of transitions to a particular isomer trivial, without any additional a priori information. This approach allows one to add isomer specificity to any molecular-beam-based experiment.

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I. Introduction

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Chemical and biological functionality is defined through the underlying molecular structure. A special part of this structure–function relationship is the role of conformational isomerism, that is, systems that can interconvert through the rotation around a single bond. This seemingly trivial structural change can have far-reaching consequences and can lead to, for example, different chemical reactivities (1,2) or different ordering of macromolecular structures such as proteins. (3)
The occurrence of different conformers has received considerable attention with the advent of high-resolution gas-phase spectroscopy based on supersonic molecular beams. Under the collision-free and rotationally cold conditions in these sources, different conformations do not interconvert and can be considered separate molecular species. Even for small organic systems, many conformers are frequently observed in the gas phase, for example, the smallest amino acid glycine has been produced in at least four different gas-phase conformations, with the exact number still subject to intense debate. (4−6) This wide conformational sampling can be considered a blessing and a curse. The presence of many structures allows for detailed studies of intramolecular interactions and also aids in linking gas-phase spectroscopy to condensed-phase systems, where typically one conformation dominates due to intermolecular interactions with the solvent. However, extracting spectroscopic information for one particular conformation present in the supersonic expansion and assigning this to a specific molecular structure is not trivial and typically relies on ab initio theory.
The current experimental approach to conformer-resolved spectroscopy is based on double-resonance hole-burning techniques. (7) These rely on having one resonant laser to selectively ionize the ground state of a specific conformer and a second laser to drive a transition that depletes (“burns”) the ground state. The burn laser is fired first, and scanning this thus allows recording a conformer-resolved spectrum, which in favorable cases can be assigned to a specific molecular geometry with the aid of theoretical chemistry calculations. This approach, and variations thereof, is now widely used across both the IR and UV spectral regions. (8−12)
We present here an alternative approach to record conformer-resolved electronic spectra that does not rely on double-resonance techniques and does not require the calculation of theoretical spectra. In particular, we show that we can make use of the differences in the permanent dipole moment of conformers to fully separate them using electrostatic fields (13,14) and then record single-color resonance enhanced multiphoton ionization (REMPI) spectra of the conformer-pure sample. This allows the trivial and unambiguous assignment of the observed spectral lines to a molecular structure. We demonstrate this here for the syn and anti-conformers of 3-aminophenol, which have a difference in dipole moment of around 1.5 D, as shown in Figure 1. Our methodology allowed us to observe and assign several torsional modes of this system for the first time. The presented approach is generally applicable to all molecular systems where the conformations exhibit a sufficient difference in dipole moment and can add conformer specificity to any molecular-beam-based spectroscopy experiment.

Figure 1

Figure 1. Structures and permanent dipole moments of syn and anti 3-aminophenol.

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II. Methods

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3-Aminophenol (98% purity, Sigma-Aldrich) was used without further purification and introduced into a molecular beam through seeding in 28 bar of neon and expansion in a pulsed Even Lavie valve, (15) operated at 500 Hz and heated to 140 °C. The molecular beam was skimmed twice before entering a 300-mm-long electrostatic deflector. This had a rod-and-through-type electrode geometry in which the electrodes were separated by a distance of 3.4 mm. (16) The electrodes were designed such that the field gradient is nearly constant in the vertical direction while being almost zero in the horizontal direction. Polar molecules flying through the deflector therefore experience a force in the vertical direction, depending on their effective dipole moment. (14) The deflector was operated at potential differences up to 15 kV, corresponding to a maximum field gradient of around 50 kV/cm. Following the deflector, the molecular beam was skimmed once more before entering the interaction chamber. Further technical details are given in the Supporting Information. In the detection region, molecules were ionized via 1 + 1 resonance enhanced multiphoton ionization (REMPI), using the frequency doubled output of a Nd:YAG pumped dye laser (Pyrromethene-597 dye pumped at 532 nm), providing 7 ns pulses that were attenuated to 6 μJ per pulse, and operating at 50 Hz. The laser was focused using an f = 750 mm lens to a spot size of approximately 100 μm inside the center of a three-plate velocity-map imaging spectrometer, (17) operated here in ion time-of-flight mode. Spatial distributions of the molecular beam were measured by translating the laser focus through the molecular beam.
Experimental deflection measurements were complemented by trajectory simulations. For these, the Stark effect of both conformers was calculated using the freely available CMIstark software package. (18) Trajectories of individual quantum states (J = 0–15, 1000 trajectories per state) were then propagated through the experimental setup. Individual trajectories were combined to a simulated deflection profile through Boltzmann weighting, with the rotational temperature fitted to the experimental data. (14)

III. Results and Discussion

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A conventional single-color 1 + 1 REMPI spectrum of 3-aminophenol from 34 100 to 35 000 cm–1 is shown at the top of Figure 2. This is consistent with previously reported REMPI spectra, (19) with band origins for the syn and anti conformers at 34 106.8 and 34 473.3 cm–1, respectively. Assuming identical efficiencies of the REMPI process for both conformers, the origin peaks yield a syn/anti ratio of 1:2.6. A plethora of peaks from vibrational transitions is furthermore observed across this wavenumber region. In order to unambiguously assign these, we turn to the electrostatic deflection technique.

Figure 2

Figure 2. Resonance enhanced multiphoton ionization spectra of 3-aminophenol. (a) Measured in the middle of the molecular beam without deflection fields, containing a mixture of syn and anti conformers. (b) At the most deflected edge of the molecular beam, containing a pure sample of syn 3-aminophenol. (c) Mixture spectrum with the pure syn spectrum subtracted (green), as well as the spectrum collected at the undeflected edge containing a nearly pure sample of anti conformers (red).

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Applying a potential difference across the deflector electrodes leads to a shift and dispersion of the species within the molecular beam, depending on the underlying effective dipole moment to mass ratio. The deflection of both syn and anti conformers was measured at potential differences of 0 and 15 kV by measuring the intensity of the respective origin bands while scanning the laser height. In Figure 3, the resulting beam profiles as a function of laser focus position are shown (data points), while the solid lines indicate the profiles extracted from numerical trajectory simulations for a rotational temperature of 1.3 K. A clear spatial separation of the conformers was observed and was in very good agreement with simulations. At a height of ∼1.4 mm above the center of the beam we observed almost exclusively molecules in the syn conformation, while ∼0.8 mm below the center the molecular beam was almost fully depleted for the syn conformer. The inset of Figure 3 shows the fractional intensity of the syn conformer across the molecular beam deflection coordinate for a potential difference of 15 kV across the deflector. The dashed lines indicate the positions where the most pure samples of the syn and anti conformers can be probed, while still having reasonable intensity.

Figure 3

Figure 3. Measured molecular beam intensity of syn (blue) and anti 3-aminophenol (red) as a function of laser height (data points), and matching trajectory simulations (solid lines), yielding a rotational temperature of 1.3 K. The inset shows the relative purity of the syn conformer across the deflected molecular beam. The vertical lines show the positions at which the resonance enhanced multiphoton ionization spectra for the pure syn (right) and anti (left) conformers were measured.

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REMPI spectra for these pure syn and anti conformers are shown in Figure 2b,c. We furthermore show in panel c the spectrum collected in the undeflected molecular beam (panel a) with the pure syn spectrum (panel b) subtracted. It is clear from these spectra that the deflection technique creates conformer-pure samples, making assignment of lines to individual conformers trivial. This is further highlighted in Figure 4, which shows a detailed view of the spectral region 34 800 to 35 000 cm–1. The collected spectrum for the anti conformer contains a small contribution from the syn conformer, but the much reduced intensity still allows unambiguous assignment. Moreover, the very pure spectrum obtained for the syn conformer allows reconstruction of the pure-anti spectrum by subtracting the syn contribution from the collected mixture spectrum, as shown by the green line in Figure 2 and Figure 4. This further confirms that only two isomeric forms are present in the molecular beam. These fully conformer-resolved spectra based on spatial separation make it very easy to unambiguously assign all peaks to one of the conformers.

Figure 4

Figure 4. Zoom-in of the spectral region 34 800 cm–1 to 35 000 cm–1 for the spectra shown in Figure 2, highlighting the purity of the produced molecular beams and the trivial assignment of lines to conformers.

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A full list of the observed spectral lines for the syn and anti conformers, along with tentative assignments, are given in the Supporting Information. Assignments are based on previously published IR–UV double resonance spectroscopy experiments performed at the FELIX free-electron laser facility and the corresponding high-level theory, (20) as well as a previously published UV REMPI spectrum. (19,21) We observe several features that have not been experimentally observed or assigned previously. For example, we observe clear spectral features due to an aromatic ring out-of-plane bend at 217 and 227 cm–1 for the syn and anti conformers, respectively. This was not previously observed but agrees well with published theory. (20) We furthermore observed strong bands at 322 cm–1 (syn) and 314 cm–1(anti), which theory suggests are due to OH wagging or NH2 torsion. The previous experiments at FELIX suggest that the OH wagging shows a significantly stronger response, and we tentatively assign the observed bands to this. Interestingly, in the S1 state probed here, the band belonging to the syn conformer appears higher in energy, whereas in the S0 state accessed by double-resonance experiments, the anti band is higher (307 cm–1 for syn and 316 cm–1 for anti (20)). For the syn conformer, we further observe a strong band at 639 cm–1, which we tentatively assign to the overtone of this transition. Moreover, the 0 → 2 and 0 → 3 overtones of the NH2 wag are observed for the syn conformer at 424 and 732 cm–1, agreeing well with previous experiments and calculations. (20) In the spectrally congested region of 400–500 cm–1, we confirm several bands in both conformers that have been assigned to a strong mixing of the 6a/6b in-plane bending modes, caused by a Fermi resonance or the Duschinsky effect. (21) It is clear that the trivial and unambiguous assignment of lines to a particular isomer adds a valuable new tool for isomer-specific spectroscopy, in particular for the often closely spaced torsional modes that are difficult to assign based on theoretical considerations alone.
The presented technique of isomer-resolved spectroscopy by electrostatic separation has several advantages over the established approach based on double resonance schemes. It requires only a single table-top laser source, whereas double resonance schemes always require (at least) two tunable laser sources. Moreover, schemes based on hole burning frequently require IR “burn” pulses with significant pulse energy to achieve sufficient depletion, which are not widely available and restricted to a few IR free-electron laser sources around the world. The electrostatic separation approach furthermore allows assignments of spectral lines to individual conformers without relying on calculations, i.e., without any a priori knowledge. Which spectral features originate from the same conformational structure can be determined purely from the experimental data. Assigning features to a particular structure requires only the calculation of the associated dipole moments and Stark effect.
Our methodology is widely applicable and requires only that molecules can be entrained into a rotationally cold molecular beam, and that the isomers have a sufficient difference in dipole moment. For typical aromatic molecules with masses up to a few hundred Daltons, a difference in dipole moment of ∼1 D and a rotational temperature of a few Kelvin is sufficient to obtain a pure sample of the more polar isomer. The latter is routinely achieved in pulsed supersonic molecular beams, (22) and also within reach of new approaches to buffer-gas cooling that could provide significantly slower molecular beams, and hence increased electrostatic deflection. (23) We also note that, in principle, the production of isomer-pure samples is not required, as long as samples with different (but known) population ratios can be produced, the individual spectra can be recovered through a global analysis. (24)
While we demonstrated here the collection of pure spectra for individual conformers (rotational isomers), the approach is generally applicable to all species within a cold molecular beam, from other forms of structural isomerism to solvent–solute clusters formed during expansion. (14,25) For example, it would allow the separation and individual study of different tautomeric structures such as those of cytosine, which is known to exist in six tautomeric forms, of which three typically are present in a molecular beam. (26) These three tautomers have dipole moments of 6.15, 4.52, and 3.10 D, which is sufficient to separate and study these structures individually. In general, spatial separation of isomers in a molecular beam adds isomer specificity to techniques that by themselves lack the spectral resolution needed to distinguish isomers. This has been demonstrated for molecular collision experiments (1) and is furthermore of use to any ultrafast dynamics experiment, which, due to the inherent bandwidth in a femtosecond pulse, cannot distinguish isomers spectroscopically.

IV. Conclusion

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We presented here a technique for performing isomer-resolved spectroscopy using only a single table-top laser, and which allows the assignment of transitions to an isomer without relying on theoretical predictions or double resonance schemes. This was demonstrated for the syn and anti conformers of 3-aminophenol, and fully isomer-resolved REMPI spectra were presented and assigned, including several previously unobserved lines. The approach is widely applicable to any polar molecule with a sufficient difference in dipole moment between the isomers. It is furthermore not limited to single-color REMPI spectroscopy as adopted here, instead the physical separation of the isomers in principle allows probing by any laser-based spectroscopic method. When using REMPI, it requires only a single resonance process, in contrast to hole-burning approaches that are double-resonance spectroscopies. Its implementation requires only a static electric field and allows one to add isomer specificity to any molecular-beam-based spectroscopy experiment.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpca.2c02277.

  • Detailed description of the experimental setup and list of observed spectral lines (PDF)

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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 Author
  • Authors
    • Grite L. Abma - Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
    • Dries Kleuskens - Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
    • Siwen Wang - Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
    • Michiel Balster - Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
    • Andre van Roij - Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
    • Niek Janssen - Radboud University, Institute for Molecules and Materials, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This work was supported by The Netherlands Organization for Scientific Research (NWO) under grant numbers STU.019.009, 712.018.004, and VI-VIDI-193.037, as well as the Spectroscopy of Cold Molecules Department and the Institute for Molecules and Materials of Radboud University Nijmegen. Computational parts of this work were carried out on the Dutch national e-infrastructure with the support of SURF Cooperative.

References

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This article references 26 other publications.

  1. 1
    Chang, Y.-P.; Długołȩcki, K.; Küpper, J.; Rösch, D.; Wild, D.; Willitsch, S. Specific Chemical Reactivities of Spatially Separated 3-Aminophenol Conformers with Cold Ca+ Ions. Science 2013, 342, 98– 101,  DOI: 10.1126/science.1242271
    Google Scholar
    1
    Specific Chemical Reactivities of Spatially Separated 3-Aminophenol Conformers with Cold Ca+ Ions
    Chang, Yuan-Pin; Dlugolecki, Karol; Kuepper, Jochen; Roesch, Daniel; Wild, Dieter; Willitsch, Stefan
    Science (Washington, DC, United States) (2013), 342 (6154), 98-101CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    Many mols. exhibit multiple rotational isomers (conformers) that interconvert thermally and are difficult to isolate. Consequently, a precise characterization of their role in chem. reactions proved challenging. The authors have probed the reactivity of specific conformers by using an exptl. technique based on their spatial sepn. in a mol. beam by electrostatic deflection. The sepd. conformers react with a target of Coulomb-crystd. ions in a trap. In the reaction of Ca+ with 3-aminophenol, a twofold larger rate const. for the cis compared with the trans conformer (differentiated by the O-H bond orientation) were found. This result is explained by conformer-specific differences in the long-range ion-mol. interaction potentials. Approach demonstrates the possibility of controlling reactivity through selection of conformational states.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhsFelsbzF&md5=16d1cac0fd5d89aac0c4cf800e488222
  2. 2
    Champenois, E. G. Conformer-Specific Photochemistry Imaged in Real Space and Time. Science 2021, 374, 178– 182,  DOI: 10.1126/science.abk3132
    Google Scholar
    2
    Conformer-specific photochemistry imaged in real space and time
    Champenois, E. G.; Sanchez, D. M.; Yang, J.; Nunes, J. P. Figueira; Attar, A.; Centurion, M.; Forbes, R.; Guhr, M.; Hegazy, K.; Ji, F.; Saha, S. K.; Liu, Y.; Lin, M.-F.; Luo, D.; Moore, B.; Shen, X.; Ware, M. R.; Wang, X. J.; Martinez, T. J.; Wolf, T. J. A.
    Science (Washington, DC, United States) (2021), 374 (6564), 178-182CODEN: SCIEAS; ISSN:1095-9203. (American Association for the Advancement of Science)
    Conformational isomers (conformers) of mols. play a decisive role in biol. and org. chem. However, exptl. methods for investigating chem. reaction dynamics are typically not conformer sensitive. We report on a gas-phase mega eV ultrafast electron diffraction investigation of a-phellandrene undergoing an electrocyclic ring-opening reaction. We directly imaged the evolution of a specific set of a-phellandrene conformers into the product isomer predicted by the Woodward-Hoffmann rules in real space and time. Our exptl. results are in quant. agreement with nonadiabatic quantum mol. dynamics simulations, which provide considerable detail of how conformation influences the time scale and quantum efficiency of photoinduced ring-opening reactions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXit1eqsbnP&md5=ec20347af136a96070ee94bf6cf4908d
  3. 3
    Dill, K. A.; MacCallum, J. L. The Protein-Folding Problem, 50 Years On. Science 2012, 338, 1042– 1046,  DOI: 10.1126/science.1219021
    Google Scholar
    3
    The protein-folding problem, 50 years on
    Dill, Ken A.; MacCallum, Justin L.
    Science (Washington, DC, United States) (2012), 338 (6110), 1042-1046CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    A review. The protein-folding problem was 1st posed about one half-century ago. The term refers to 3 broad questions: (1) What is the phys. code by which an amino acid sequence dictates a protein's native structure (2) How can proteins fold so fast and (3) Can one devise a computer algorithm to predict protein structures from their sequences. Here, the authors review progress on these problems. In a few cases, computer simulations of the phys. forces in chem. detailed models have now achieved the accurate folding of small proteins. It has been learned that proteins fold rapidly because random thermal motions cause conformational changes leading energetically downhill toward the native structure, a principle that is captured in funnel-shaped energy landscapes. And thanks in part to the large Protein Data Bank of known structures, predicting protein structures is now far more successful than was thought possible in earlier days. What began as 3 questions of basic science one half-century ago has now grown into the full-fledged research field of protein phys. science.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xhs12itrnF&md5=bd73e6103d437b24594ce4cd86ad25dc
  4. 4
    Godfrey, P. D.; Brown, R. D. Shape of Glycine. J. Am. Chem. Soc. 1995, 117, 2019– 2023,  DOI: 10.1021/ja00112a015
    Google Scholar
    4
    Shape of Glycine
    Godfrey, Peter D.; Brown, Ronald D.
    Journal of the American Chemical Society (1995), 117 (7), 2019-23CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Using a Stark-modulated free-expansion jet spectrometer, the authors have measured and subsequently analyzed the rotational spectra of the two 13C, the 15N, and the methylene-d2 isotopomers of the amino acid glycine conformers 1 and 2 and of the N,O-d3 isotopomer for conformer 2. The structural implications of the derived rotational consts., in light of published geometric parameters from elaborate post-Hartree-Fock ab initio calcns., have led to the conclusion that both of these conformers have rP structures of Cs symmetry. A twisted C1 symmetry modification of conformer 2, designated 3, is the favored prediction of elaborate ab initio calcns., but the effect of the zero-point twisting vibration would give either conformation an rP geometry of Cs symmetry. Thus there is no discrepancy between theory and expt. From a sensitive survey scan of the spectrum of the main isotopomer, an upper limit of 1/5 has been set for the abundance of the theor. conformer 4 relative to 2. This result appears to be in conflict with the most elaborate ab initio calcns., which give 4 as energetically similar to 2 and may point to the importance of conformational relaxation during the jet expansion for higher energy conformers that have suitably low barriers to isomerization.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXjs1CmsLw%253D&md5=56345df6afc9c0759d313ee2542bfe4d
  5. 5
    Godfrey, P. D.; Brown, R. D.; Rodgers, F. M. The Missing Conformers of Glycine and Alanine: Relaxation in Seeded Supersonic Jets. J. Mol. Struct. 1996, 376, 65– 81,  DOI: 10.1016/0022-2860(95)09065-7
    Google Scholar
    5
    The missing conformers of glycine and alanine: relaxation in seeded supersonic jets
    Godfrey, Peter D.; Brown, Ronald D.; Rodgers, Fiona M.
    Journal of Molecular Structure (1996), 376 (), 65-81CODEN: JMOSB4; ISSN:0022-2860. (Elsevier)
    Certain conformers of glycine and alanine that are predicted by ab initio calcns. to be among those of the lowest energy have not been detected in jet spectroscopy studies of these amino acids, although others of similar or higher predicted energy are obsd. Selective conformational relaxation of the missing conformers to lower energy species during the free jet expansion, broadly consistent with the criteria established by R. S. Ruoff et al. (1990) and by P. Felder and H. H. Geunthard (1982), has been found to provide a satisfactory explanation. Relevant regions of the mol. potential energy hypersurface have been modeled via ab initio calcns. [MP2/6-31G(d,p)] and these show that glycine conformers 4 and 7 can relax to conformer 1, leading to the conclusion, in accordance with observation, that only the latter and conformer 2 should be detected in the jet. In the case of alanine, the ab initio study of the mol. potential energy hypersurface has yielded revised data on predicted spectroscopic consts. for some conformers. Because of the combined effects of relaxation and conformational coalescence through large-amplitude vibrational motion, the revised data do not change the interpretation of the previous spectroscopic study of alanine. The barrier sepg. conformers 2 and 3 is predicted to be no more than 129 cm-1, so that in addn. conformer 1, only a single addnl. coalesced conformer (2,3), undergoing a large-amplitude motion in a double-min. potential, is expected to appear in the jet spectrum rather than two sep. species. The ab initio calcns. on alanine indicate that conformers 4 and 5 are sepd. by a low energy barrier and a similarly low barrier separates conformer 4 from the much lower energy conformer 1. The resulting coalesced conformer (4,5) is effectively a "ledge" on one wall of the potential well contg. conformer 1, and is occupied via an excited vibrational state of conformer 1. In this light, the coalesced conformer (4,5) is not expected to be obsd. in the jet, as the vibrational relaxation of low-frequency vibrational modes is known to be very efficient in free jet expansions. Overall, no conflicts are found to remain between the exptl. observations of jet spectra and the ab initio calcns. for glycine and alanine, provided that the scope of such calcns. is broadened from a narrower focus on equil. structures to consideration of the potential hypersurface. This approach should be important in the correct interpretation of the spectra of other multi-conformational species in free jet expansions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XhsVaqsLw%253D&md5=c14e19f4a27403ab8964c5bc5179cae1
  6. 6
    Barone, V.; Biczysko, M.; Bloino, J.; Puzzarini, C. Glycine Conformers: A Never-Ending Story?. Phys. Chem. Chem. Phys. 2013, 15, 1358– 1363,  DOI: 10.1039/C2CP43884D
    Google Scholar
    6
    Glycine conformers: a never-ending story?
    Barone, Vincenzo; Biczysko, Malgorzata; Bloino, Julien; Puzzarini, Cristina
    Physical Chemistry Chemical Physics (2013), 15 (5), 1358-1363CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    The structure and vibrational spectra of a marginally stable conformer of glycine (usually referred to as VIp or ttc) recently detected in low-temp. matrixes have been characterized by a state-of-the-art computational approach allowing an overall quality for bond distances, rotational consts., conformational enthalpies and vibrational frequencies well within the chem. accuracy. The high accuracy of the computational results allows us to draw a fully consistent interpretation of the available exptl. data and to obtain a more complete characterization of an elusive glycine conformer.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhsVCqug%253D%253D&md5=b501f7ccc117bad20d69c86c48814560
  7. 7
    Robertson, E. G.; Simons, J. P. Getting into shape: Conformational and supramolecular landscapes in small biomolecules and their hydrated clusters. Phys. Chem. Chem. Phys. 2001, 3, 1– 18,  DOI: 10.1039/b008225m
    Google Scholar
    7
    Getting into shape: Conformational and supramolecular landscapes in small biomolecules and their hydrated clusters
    Robertson, Evan G.; Simons, John P.
    Physical Chemistry Chemical Physics (2001), 3 (1), 1-18CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    A review, with 171 refs. The last few years have seen a very rapid growth in understanding the influence of non-bonded, particularly hydrogen-bonded interactions, on the shapes and conformations of flexible mols., including those of pharmacol. or biol. importance, and of the supramol. structures of their hydrated clusters. This has come about through the combination of a wide range of newly developed spectroscopic strategies, many of which are laser-based, coupled with powerful and widely available ab initio codes for structural computation. The consequent rapid growth of a new link between the worlds of chem. and biophysics is surveyed in a review which introduces the range of present strategies, their origins, and their application to studies of neurotransmitters, amides and peptides, amino acids and nucleic acid bases. It concludes with a prospectus for the future.
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  8. 8
    Dian, B. C.; Clarkson, J. R.; Zwier, T. S. Direct Measurement of Energy Thresholds to Conformational Isomerization in Tryptamine. Science 2004, 303, 1169– 1173,  DOI: 10.1126/science.1093731
    Google Scholar
    8
    Direct Measurement of Energy Thresholds to Conformational Isomerization in Tryptamine
    Dian, Brian C.; Clarkson, Jasper R.; Zwier, Timothy S.
    Science (Washington, DC, United States) (2004), 303 (5661), 1169-1173CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    Stimulated emission pumping (SEP)-hole filling spectroscopy and SEP-induced population transfer spectroscopy have been used to place narrow bounds on the energy thresholds for isomerization between individual reactant-product isomer pairs involving the seven conformational min. of tryptamine. The thresholds for isomerizing conformer A to all six other conformations divided into three groups at 750 wavenumbers (cm-1) (A → B, F), 1000 cm-1 [A → C(2)], and 1280 to 1320 cm-1 [A → D, E, and C(1)]. The appearance of the first band and the absence of the band below it were used to place upper and lower bounds to the barrier heights for each process. The thresholds for A → B and B → A isomerizations were also combined to det. the relative energies of these two lowest energy min. The combined data from all X → Y isomerizations identify important isomerization pathways on the potential energy surface linking the min.
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  9. 9
    Snoek, L. C.; Robertson, E. G.; Kroemer, R. T.; Simons, J. P. Conformational landscapes in amino acids: Infrared and ultraviolet ion-dip spectroscopy of phenylalanine in the gas phase. Chem. Phys. Lett. 2000, 321, 49– 56,  DOI: 10.1016/S0009-2614(00)00320-1
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    9
    Conformational landscapes in amino acids: infrared and ultraviolet ion-dip spectroscopy of phenylalanine in the gas phase
    Snoek, L. C.; Robertson, E. G.; Kroemer, R. T.; Simons, J. P.
    Chemical Physics Letters (2000), 321 (1,2), 49-56CODEN: CHPLBC; ISSN:0009-2614. (Elsevier Science B.V.)
    A full structural assignment of the most stable conformers of phenylalanine, based upon a combination of UV and IR ion-dip spectroscopy of the jet-cooled amino acid, coupled with high-level ab-initio computation is presented. The results are discussed in relation to aliph. amino acids to highlight the importance of ring side-chain interactions. The question of zwitterion formation is also discussed.
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  10. 10
    Bakker, J. M.; Mac Aleese, L.; Meijer, G.; von Helden, G. Fingerprint IR spectroscopy to probe amino acid conformations in the gas phase. Phys. Rev. Lett. 2003, 91, 203003,  DOI: 10.1103/PhysRevLett.91.203003
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    10
    Fingerprint IR Spectroscopy to Probe Amino Acid Conformations in the Gas Phase
    Bakker, Joost M.; Mac Aleese, Luke; Meijer, Gerard; von Helden, Gert
    Physical Review Letters (2003), 91 (20), 203003/1-203003/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
    The IR absorption spectra are reported of different conformational isomers of gas phase amino acid mols. in the mol. fingerprint region of 330-1500 cm-1. The IR absorption spectra for 3 conformers of the amino acid tryptophan show absorption bands that uniquely identify the conformational structure of the mol. and that are well matched by d. functional theory calcns. The present observations hold great promise for future identification of conformational folding of larger mols. by their IR absorption characteristics.
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  11. 11
    de Vries, M. S.; Hobza, P. Gas-Phase Spectroscopy of Biomolecular Building Blocks. Annu. Rev. Phys. Chem. 2007, 58, 585– 612,  DOI: 10.1146/annurev.physchem.57.032905.104722
    Google Scholar
    11
    Gas-phase spectroscopy of biomolecular building blocks
    de Vries, Mattanjah S.; Hobza, Pavel
    Annual Review of Physical Chemistry (2007), 58 (), 585-612CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews Inc.)
    A review. Gas-phase spectroscopy lends itself ideally to the study of isolated mols. and provides important data for comparison with theory. In recent years, we have seen enormous progress in the study of biomol. building blocks in the gas phase. The motivation for such work is threefold:. (a) It is important to distinguish between intrinsic mol. properties and properties that result from the biol. environment. (b) Gas-phase spectroscopy of clusters provides insights into fundamental interactions and into microsolvation. (c) Gas-phase data support quantum-chem. calcns. This review focuses on the current status of (poly)amino acids and DNA bases. Recent results help elucidate structure and hydrogen-bonded interactions, as well as showcase a successful interplay between theory and expt.
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  12. 12
    van Geenen, F. A. M. G.; Kranenburg, R. F.; van Asten, A. C.; Martens, J.; Oomens, J.; Berden, G. Isomer-Specific Two-Color Double-Resonance IR2MS3 Ion Spectroscopy Using a Single Laser: Application in the Identification of Novel Psychoactive Substances. Anal. Chem. 2021, 93, 2687– 2693,  DOI: 10.1021/acs.analchem.0c05042
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    12
    Isomer-Specific Two-Color Double-Resonance IR2MS3 Ion Spectroscopy Using a Single Laser: Application in the Identification of Novel Psychoactive Substances
    van Geenen, Fred A. M. G.; Kranenburg, Ruben F.; van Asten, Arian C.; Martens, Jonathan; Oomens, Jos; Berden, Giel
    Analytical Chemistry (Washington, DC, United States) (2021), 93 (4), 2687-2693CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    The capability of an ion trap mass spectrometer to store ions for an arbitrary amt. of time allows the use of a single IR laser to perform two-color double resonance IR-IR spectroscopic expts. on mass-to-charge (m/z) selected ions. In this single-laser IR2MS3 scheme, one IR laser frequency is used to remove a selected set of isomers from the total trapped ion population and the second IR laser frequency, from the same laser, is used to record the IR spectrum of the remaining precursor ions. This yields isomer-specific vibrational spectra of the m/z-selected ions, which can reveal the structure and identity of the initially co-isolated isomeric species. The use of a single laser greatly reduces the exptl. complexity of two-color IR2MS3 and enhances its application in fields employing anal. MS. In this work, we demonstrate the methodol. by acquiring single-laser IR2MS3 spectra in a forensic context, identifying two previously unidentified isomeric novel psychoactive substances (NPS) from a sample that was confiscated by the Amsterdam Police.
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  13. 13
    Filsinger, F.; Küpper, J.; Meijer, G.; Hansen, J. L.; Maurer, J.; Nielsen, J. H.; Holmegaard, L.; Stapelfeldt, H. Pure samples of individual conformers: the separation of stereo-isomers of complex molecules using electric fields. Angew. Chem., Int. Ed. 2009, 48, 6900– 6902,  DOI: 10.1002/anie.200902650
    Google Scholar
    13
    Pure samples of individual conformers: The separation of stereoisomers of complex molecules using electric fields
    Filsinger, Frank; Kuepper, Jochen; Meijer, Gerard; Hansen, Jonas L.; Maurer, Jochen; Nielsen, Jens H.; Holmegaard, Lotte; Stapelfeldt, Henrik
    Angewandte Chemie, International Edition (2009), 48 (37), 6900-6902CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The authors demonstrate that electrostatic deflection, a classic mol. beam manipulation method that dates back to the 1920s, allows the spatial sepn. of the conformers of a neutral mol. when it is applied to intense beams of rotationally cold mols. produced by a state-of-the-art pulsed supersonic expansion source. The cis and trans conformers of 3-aminophenol are used herein as prototypical structural isomers of complex mols. From the precisely known rotational consts. and dipole moments, the energies of the rotational states of cis-3-aminophenol and trans-3-aminophenol are calcd. as a function of elec. field strength.
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  14. 14
    Chang, Y.-P.; Horke, D. A.; Trippel, S.; Küpper, J. Spatially-controlled complex molecules and their applications. Int. Rev. Phys. Chem. 2015, 34, 557– 590,  DOI: 10.1080/0144235X.2015.1077838
    Google Scholar
    14
    Spatially-controlled complex molecules and their applications
    Chang, Yuan-Pin; Horke, Daniel A.; Trippel, Sebastian; Kuepper, Jochen
    International Reviews in Physical Chemistry (2015), 34 (4), 557-590CODEN: IRPCDL; ISSN:0144-235X. (Taylor & Francis Ltd.)
    The understanding of mol. structure and function is at the very heart of the chem. and mol. sciences. Expts. that allow for the creation of structurally pure samples and the investigation of their mol. dynamics and chem. function have developed tremendeously over the last few decades, although 'there's plenty of room at the bottom' for better control as well as further applications. Here, we describe the use of inhomogeneous elec. fields for the manipulation of neutral mols. in the gas-phase, i.e. for the sepn. of complex mols. according to size, structural isomer, and quantum state. For these complex mols., all quantum states are strong-field seeking, requiring dynamic fields for their confinement. Current applications of these controlled samples are summarised and interesting future applications discussed.
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  15. 15
    Even, U. Pulsed Supersonic Beams from High Pressure Source: Simulation Results and Experimental Measurements. Adv. Chem. 2014, 2014, 636042,  DOI: 10.1155/2014/636042
    Google Scholar
    There is no corresponding record for this reference.
  16. 16
    de Nijs, A. J.; Bethlem, H. L. On deflection fields, weak-focusing and strong-focusing storage rings for polar molecules. Phys. Chem. Chem. Phys. 2011, 13, 19052– 8,  DOI: 10.1039/c1cp21477b
    Google Scholar
    16
    On deflection fields, weak-focusing and strong-focusing storage rings for polar molecules
    de Nijs, Adrian J.; Bethlem, Hendrick L.
    Physical Chemistry Chemical Physics (2011), 13 (42), 19052-19058CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    In this paper, we analyze elec. deflection fields for polar mols. in terms of a multipole expansion and derive a simple but rather insightful expression for the force on the mols. Ideally, a deflection field exerts a strong, const. force in one direction, while the force in the other directions is zero. We show how, by a proper choice of the expansion coeffs., this ideal can be best approximated. We present a design for a practical electrode geometry based on this anal. By bending such a deflection field into a circle, a simple storage ring can be created; the direct analog of a weak-focusing cyclotron for charged particles. We show that for realistic parameters a weak-focusing ring is only stable for mols. with a very low velocity. A strong-focusing (alternating-gradient) storage ring can be created by arranging many straight deflection fields in a circle and by alternating the sign of the hexapole term between adjacent deflection fields. The acceptance of this ring is numerically calcd. for realistic parameters. Such a storage ring might prove useful in expts. looking for an EDM of elementary particles.
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  17. 17
    Eppink, A. T. J. B.; Parker, D. H. Velocity map imaging of ions and electrons using electrostatic lenses: Application in photoelectron and photofragment ion imaging of molecular oxygen. Rev. Sci. Instrum. 1997, 68, 3477– 3484,  DOI: 10.1063/1.1148310
    Google Scholar
    17
    Velocity map imaging of ions and electrons using electrostatic lenses: Application in photoelectron and photofragment ion imaging of molecular oxygen
    Eppink, Andre T. J. B.; Parker, David H.
    Review of Scientific Instruments (1997), 68 (9), 3477-3484CODEN: RSINAK; ISSN:0034-6748. (American Institute of Physics)
    The application of electrostatic lenses is demonstrated to give a substantial improvement of the two-dimensional (2D) ion/electron imaging technique. This combination of ion lens optics and 2D detection makes "velocity map imaging" possible, i.e., all particles with the same initial velocity vector are mapped onto the same point on the detector. Whereas the more common application of grid electrodes leads to transmission redn., severe trajectory deflections and blurring due to the non-point source geometry, these problems are avoided with open lens electrodes. A three-plate assembly with aperture electrodes has been tested and its properties are compared with those of grid electrodes. The photodissocn. processes occurring in mol. oxygen following the two-photon 3dπ(3Σ1g-)(v=2, N=2)←X(3Σg-) Rydberg excitation around 225 nm are presented here to show the improvement in spatial resoln. in the ion and electron images. Simulated trajectory calcns. show good agreement with expt. and support the appealing properties of this velocity mapping technique.
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  18. 18
    Chang, Y.-P.; Filsinger, F.; Sartakov, B.; Küpper, J. CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields. Comput. Phys. Commun. 2014, 185, 339– 349,  DOI: 10.1016/j.cpc.2013.09.001
    Google Scholar
    18
    CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields
    Chang, Yuan-Pin; Filsinger, Frank; Sartakov, Boris G.; Kuepper, Jochen
    Computer Physics Communications (2014), 185 (1), 339-349CODEN: CPHCBZ; ISSN:0010-4655. (Elsevier B.V.)
    The Controlled Mol. Imaging group (CMI) at the Center for Free Electron Laser Science (CFEL) has developed the CMISTARK software to calc., view, and analyze the energy levels of adiabatic Stark energy curves of linear, sym. top and asym. top mols. The program exploits the symmetry of the Hamiltonian to generate fully labeled adiabatic Stark energy curves. CMISTARK is written in Python and easily extendable, while the core numerical calcns. make use of machine optimized BLAS and LAPACK routines. Calcd. energies are stored in HDF5 files for convenient access and programs to ext. ASCII data or to generate graphical plots are provided.
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  19. 19
    Xie, Y.; Su, H.; Tzeng, W. B. Rotamers of m-aminophenol cation studied by mass analyzed threshold ionization spectroscopy and theoretical calculations. Chem. Phys. Lett. 2004, 394, 182– 187,  DOI: 10.1016/j.cplett.2004.07.005
    Google Scholar
    19
    Rotamers of m-aminophenol cation studied by mass analyzed threshold ionization spectroscopy and theoretical calculations
    Xie, Yan; Su, Huawei; Tzeng, Wen Bih
    Chemical Physics Letters (2004), 394 (1-3), 182-187CODEN: CHPLBC; ISSN:0009-2614. (Elsevier B.V.)
    The vibrationally resolved spectra of selected rotamers of m-aminophenol were recorded by mass analyzed threshold ionization spectroscopy in connection with two-color resonant two-photon excitation scheme. The adiabatic ionization energies of the cis and trans rotamers are 61,460 ± 5 and 61,734 ± 5 cm-1, resp. The frequencies of modes 1 (breathing) and 18a (in-plane CH bending) are 744 and 1097 cm-1 for the cis, and 736 and 1104 cm-1 for the trans rotamer, resp. Different orientation of the OH with respect to the NH2 substituent only slightly influences these two modes.
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  20. 20
    Yatsyna, V.; Bakker, D. J.; Feifel, R.; Rijs, A. M.; Zhaunerchyk, V. aminophenol isomers unraveled by conformer-specific far-IR action spectroscopy. Phys. Chem. Chem. Phys. 2016, 18, 6275– 6283,  DOI: 10.1039/C5CP07426F
    Google Scholar
    20
    Aminophenol isomers unraveled by conformer-specific far-IR action spectroscopy
    Yatsyna, Vasyl; Bakker, Daniel J.; Feifel, Raimund; Rijs, Anouk M.; Zhaunerchyk, Vitali
    Physical Chemistry Chemical Physics (2016), 18 (8), 6275-6283CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Spectroscopic studies of mol. structure can strongly benefit from extending the conventional mid-IR range to the far-IR and THz regions, as low-frequency mol. vibrations provide unique fingerprints and high sensitivity to intra- and intermol. interactions. The gas-phase conformer specific far-IR spectra of aminophenol isomers, recorded in the spectral range of 220-800 cm-1 at the free-electron laser lab. FELIX in Nijmegen (the Netherlands), are reported. Many distinct far-IR vibrational signatures which are specific for the mol. structure of the different aminophenol isomers are revealed and assigned. The obsd. far-IR transitions of the NH2 wagging (inversion) motion were treated with a double-min. harmonic well potential model that has enabled us to obtain the inversion barrier values. Also, the limitations and capability of conventional DFT frequency calcns. to describe the far-IR vibrational modes are discussed.
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  21. 21
    Shinozaki, M.; Sakai, M.; Yamaguchi, S.; Fujioka, T.; Fujii, M. S1 ←S0 electronic spectrum of jet-cooled m-aminophenol. Phys. Chem. Chem. Phys. 2003, 5, 5044– 5050,  DOI: 10.1039/B309461H
    Google Scholar
    21
    S1-S0 Electronic spectrum of jet-cooled m-aminophenol
    Shinozaki, Minako; Sakai, Makoto; Yamaguchi, Shigeru; Fujioka, Tomoo; Fujii, Masaaki
    Physical Chemistry Chemical Physics (2003), 5 (22), 5044-5050CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    The S1 and S0 states of m-aminophenol were studied using laser induced fluorescence and dispersed fluorescence spectroscopy in a supersonic jet. The dispersed fluorescence spectra, obtained by exciting the bands at 34,109 and 34,469 cm-1, show the same vibronic structure, which suggests the coexistence of rotational isomers in m-aminophenol. A quantum chem. calcn. also supports the coexistence of rotational isomers. From the relative intensities in the spectrum and the calcd. stabilization energies of isomers, the bands are assigned to the origin of the cis- and trans-isomers, resp. The dispersed fluorescence spectra obtained by exciting the S1 vibronic bands were analyzed by comparing with the calcd. vibrational frequencies and IR and Raman spectra. From the anal., the S1 vibronic bands were assigned. A 1-to-one correspondence between the S1 and S0 vibrations is broken, and vibrational mixing due to Fermi resonance or the Duschinsky effect is suggested.
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  22. 22
    Even, U.; Jortner, J.; Noy, D.; Lavie, N.; Cossart-Magos, N. Cooling of large molecules below 1 K and He clusters formation. J. Chem. Phys. 2000, 112, 8068– 8071,  DOI: 10.1063/1.481405
    Google Scholar
    22
    Cooling of large molecules below 1 K and He clusters formation
    Even, U.; Jortner, J.; Noy, D.; Lavie, N.; Cossart-Magos, C.
    Journal of Chemical Physics (2000), 112 (18), 8068-8071CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
    We present here the design details of a high-pressure pulsed valve that generates intense supersonic jets. The measured rotational contours of aniline indicate that temps. <0.5 K can be achieved before the formation of clusters with the He carrier gas. The spectral shifts and vibronic structure of anthracene-Hen clusters (n = 1-6) are showing some surprising features.
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  23. 23
    Hutzler, N. R.; Lu, H.-I.; Doyle, J. M. The buffer gas beam: An intense, cold, and slow source for atoms and molecules. Chem. Rev. 2012, 112, 4803– 4827,  DOI: 10.1021/cr200362u
    Google Scholar
    23
    The Buffer Gas Beam: An Intense, Cold, and Slow Source for Atoms and Molecules
    Hutzler, Nicholas R.; Lu, Hsin-I.; Doyle, John M.
    Chemical Reviews (Washington, DC, United States) (2012), 112 (9), 4803-4827CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. The authors discuss the properties of buffer gas beams, compare them with more std. beam techniques, and discuss both existing and proposed applications. The ability of this technique to deliver cold, slow, and intense beams of atoms and mols., including those that are difficult to produce with effusive or supersonic techniques, is fueling adoption of this technique for a wide range of applications. However, this beam prodn. technique is still relatively new and has not been as thoroughly characterized and developed as others.
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  24. 24
    Liu, J.; Koenig, J. L. Data Processing Techniques to Extract Pure-Component Spectra from Mixture Spectra and Their Application to Polymeric Systems. Anal. Chem. 1987, 59, 2609– 2615,  DOI: 10.1021/ac00148a017
    Google Scholar
    24
    Data processing techniques to extract pure-component spectra from mixture spectra and their application to polymeric systems
    Liu, Juwhan; Koenig, Jack L.
    Analytical Chemistry (1987), 59 (21), 2609-15CODEN: ANCHAM; ISSN:0003-2700.
    A nonlinear optimization technique was developed to ext. pure-component spectra from the mixt. spectra. The absorbances of the pure spectra and the concns. are variables to be optimized in the algorithm proposed. As constraints, nonnegativities of absorbances and concns. are applied where the concns. are used in terms of fractions. Through tests, three "pure" rotational isomer spectra of poly(ethylene terephthalate) were obtained. A least-squares procedure was utilized to expand the scope of the proposed method. This technique was applicable to all systems described by the Beer-Lambert law.
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  25. 25
    Trippel, S.; Chang, Y.-P.; Stern, S.; Mullins, T.; Holmegaard, L.; Küpper, J. Spatial separation of state- and size-selected neutral clusters. Phys. Rev. A 2012, 86, 033202,  DOI: 10.1103/PhysRevA.86.033202
    Google Scholar
    25
    Spatial separation of state- and size-selected neutral clusters
    Trippel, Sebastian; Chang, Yuan-Pin; Stern, Stephan; Mullins, Terry; Holmegaard, Lotte; Kuepper, Jochen
    Physical Review A: Atomic, Molecular, and Optical Physics (2012), 86 (3-A), 033202/1-033202/6CODEN: PLRAAN; ISSN:1050-2947. (American Physical Society)
    We demonstrate the spatial sepn. of the prototypical indole(H2O) clusters from the various species present in the supersonic expansion of mixts. of indole and water. The major mol. constituents of the resulting mol. beam are H2O, indole, indole(H2O), and indole(H2O)2. It is a priori not clear whether such floppy systems are amenable to strong manipulation using elec. fields. Here, we have exploited the cold supersonic mol. beam and the electrostatic deflector to sep. indole(H2O) from the other mol. species as well as the helium seed gas. The exptl. results are quant. explained by trajectory simulations, which also demonstrate that the quantum-state selectivity of the process leads to samples of indole(H2O) in low-lying rotational states. The prepd. clean samples of indole(H2O) are ideally suited for investigations of the stereodynamics of this complex system, including time-resolved half-collision and diffraction expts. of fixed-in-space clusters. Our findings clearly demonstrate that the hydrogen bonded indole(H2O) complex behaves as a rigid mol. under our exptl. conditions and that it can be strongly deflected.
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  26. 26
    Franz, J.; Gianturco, F. A. Low-Energy Positron Scattering from DNA Nucleobases: The Effects from Permanent Dipoles. Eur. Phys. J. D 2014, 68, 279,  DOI: 10.1140/epjd/e2014-50072-0
    Google Scholar
    There is no corresponding record for this reference.

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    Figure 1

    Figure 1. Structures and permanent dipole moments of syn and anti 3-aminophenol.

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    Figure 2

    Figure 2. Resonance enhanced multiphoton ionization spectra of 3-aminophenol. (a) Measured in the middle of the molecular beam without deflection fields, containing a mixture of syn and anti conformers. (b) At the most deflected edge of the molecular beam, containing a pure sample of syn 3-aminophenol. (c) Mixture spectrum with the pure syn spectrum subtracted (green), as well as the spectrum collected at the undeflected edge containing a nearly pure sample of anti conformers (red).

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    Figure 3

    Figure 3. Measured molecular beam intensity of syn (blue) and anti 3-aminophenol (red) as a function of laser height (data points), and matching trajectory simulations (solid lines), yielding a rotational temperature of 1.3 K. The inset shows the relative purity of the syn conformer across the deflected molecular beam. The vertical lines show the positions at which the resonance enhanced multiphoton ionization spectra for the pure syn (right) and anti (left) conformers were measured.

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    Figure 4

    Figure 4. Zoom-in of the spectral region 34 800 cm–1 to 35 000 cm–1 for the spectra shown in Figure 2, highlighting the purity of the produced molecular beams and the trivial assignment of lines to conformers.

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    This article references 26 other publications.

    1. 1
      Chang, Y.-P.; Długołȩcki, K.; Küpper, J.; Rösch, D.; Wild, D.; Willitsch, S. Specific Chemical Reactivities of Spatially Separated 3-Aminophenol Conformers with Cold Ca+ Ions. Science 2013, 342, 98– 101,  DOI: 10.1126/science.1242271
      Google Scholar
      1
      Specific Chemical Reactivities of Spatially Separated 3-Aminophenol Conformers with Cold Ca+ Ions
      Chang, Yuan-Pin; Dlugolecki, Karol; Kuepper, Jochen; Roesch, Daniel; Wild, Dieter; Willitsch, Stefan
      Science (Washington, DC, United States) (2013), 342 (6154), 98-101CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      Many mols. exhibit multiple rotational isomers (conformers) that interconvert thermally and are difficult to isolate. Consequently, a precise characterization of their role in chem. reactions proved challenging. The authors have probed the reactivity of specific conformers by using an exptl. technique based on their spatial sepn. in a mol. beam by electrostatic deflection. The sepd. conformers react with a target of Coulomb-crystd. ions in a trap. In the reaction of Ca+ with 3-aminophenol, a twofold larger rate const. for the cis compared with the trans conformer (differentiated by the O-H bond orientation) were found. This result is explained by conformer-specific differences in the long-range ion-mol. interaction potentials. Approach demonstrates the possibility of controlling reactivity through selection of conformational states.
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    2. 2
      Champenois, E. G. Conformer-Specific Photochemistry Imaged in Real Space and Time. Science 2021, 374, 178– 182,  DOI: 10.1126/science.abk3132
      Google Scholar
      2
      Conformer-specific photochemistry imaged in real space and time
      Champenois, E. G.; Sanchez, D. M.; Yang, J.; Nunes, J. P. Figueira; Attar, A.; Centurion, M.; Forbes, R.; Guhr, M.; Hegazy, K.; Ji, F.; Saha, S. K.; Liu, Y.; Lin, M.-F.; Luo, D.; Moore, B.; Shen, X.; Ware, M. R.; Wang, X. J.; Martinez, T. J.; Wolf, T. J. A.
      Science (Washington, DC, United States) (2021), 374 (6564), 178-182CODEN: SCIEAS; ISSN:1095-9203. (American Association for the Advancement of Science)
      Conformational isomers (conformers) of mols. play a decisive role in biol. and org. chem. However, exptl. methods for investigating chem. reaction dynamics are typically not conformer sensitive. We report on a gas-phase mega eV ultrafast electron diffraction investigation of a-phellandrene undergoing an electrocyclic ring-opening reaction. We directly imaged the evolution of a specific set of a-phellandrene conformers into the product isomer predicted by the Woodward-Hoffmann rules in real space and time. Our exptl. results are in quant. agreement with nonadiabatic quantum mol. dynamics simulations, which provide considerable detail of how conformation influences the time scale and quantum efficiency of photoinduced ring-opening reactions.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXit1eqsbnP&md5=ec20347af136a96070ee94bf6cf4908d
    3. 3
      Dill, K. A.; MacCallum, J. L. The Protein-Folding Problem, 50 Years On. Science 2012, 338, 1042– 1046,  DOI: 10.1126/science.1219021
      Google Scholar
      3
      The protein-folding problem, 50 years on
      Dill, Ken A.; MacCallum, Justin L.
      Science (Washington, DC, United States) (2012), 338 (6110), 1042-1046CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      A review. The protein-folding problem was 1st posed about one half-century ago. The term refers to 3 broad questions: (1) What is the phys. code by which an amino acid sequence dictates a protein's native structure (2) How can proteins fold so fast and (3) Can one devise a computer algorithm to predict protein structures from their sequences. Here, the authors review progress on these problems. In a few cases, computer simulations of the phys. forces in chem. detailed models have now achieved the accurate folding of small proteins. It has been learned that proteins fold rapidly because random thermal motions cause conformational changes leading energetically downhill toward the native structure, a principle that is captured in funnel-shaped energy landscapes. And thanks in part to the large Protein Data Bank of known structures, predicting protein structures is now far more successful than was thought possible in earlier days. What began as 3 questions of basic science one half-century ago has now grown into the full-fledged research field of protein phys. science.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xhs12itrnF&md5=bd73e6103d437b24594ce4cd86ad25dc
    4. 4
      Godfrey, P. D.; Brown, R. D. Shape of Glycine. J. Am. Chem. Soc. 1995, 117, 2019– 2023,  DOI: 10.1021/ja00112a015
      Google Scholar
      4
      Shape of Glycine
      Godfrey, Peter D.; Brown, Ronald D.
      Journal of the American Chemical Society (1995), 117 (7), 2019-23CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Using a Stark-modulated free-expansion jet spectrometer, the authors have measured and subsequently analyzed the rotational spectra of the two 13C, the 15N, and the methylene-d2 isotopomers of the amino acid glycine conformers 1 and 2 and of the N,O-d3 isotopomer for conformer 2. The structural implications of the derived rotational consts., in light of published geometric parameters from elaborate post-Hartree-Fock ab initio calcns., have led to the conclusion that both of these conformers have rP structures of Cs symmetry. A twisted C1 symmetry modification of conformer 2, designated 3, is the favored prediction of elaborate ab initio calcns., but the effect of the zero-point twisting vibration would give either conformation an rP geometry of Cs symmetry. Thus there is no discrepancy between theory and expt. From a sensitive survey scan of the spectrum of the main isotopomer, an upper limit of 1/5 has been set for the abundance of the theor. conformer 4 relative to 2. This result appears to be in conflict with the most elaborate ab initio calcns., which give 4 as energetically similar to 2 and may point to the importance of conformational relaxation during the jet expansion for higher energy conformers that have suitably low barriers to isomerization.
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    5. 5
      Godfrey, P. D.; Brown, R. D.; Rodgers, F. M. The Missing Conformers of Glycine and Alanine: Relaxation in Seeded Supersonic Jets. J. Mol. Struct. 1996, 376, 65– 81,  DOI: 10.1016/0022-2860(95)09065-7
      Google Scholar
      5
      The missing conformers of glycine and alanine: relaxation in seeded supersonic jets
      Godfrey, Peter D.; Brown, Ronald D.; Rodgers, Fiona M.
      Journal of Molecular Structure (1996), 376 (), 65-81CODEN: JMOSB4; ISSN:0022-2860. (Elsevier)
      Certain conformers of glycine and alanine that are predicted by ab initio calcns. to be among those of the lowest energy have not been detected in jet spectroscopy studies of these amino acids, although others of similar or higher predicted energy are obsd. Selective conformational relaxation of the missing conformers to lower energy species during the free jet expansion, broadly consistent with the criteria established by R. S. Ruoff et al. (1990) and by P. Felder and H. H. Geunthard (1982), has been found to provide a satisfactory explanation. Relevant regions of the mol. potential energy hypersurface have been modeled via ab initio calcns. [MP2/6-31G(d,p)] and these show that glycine conformers 4 and 7 can relax to conformer 1, leading to the conclusion, in accordance with observation, that only the latter and conformer 2 should be detected in the jet. In the case of alanine, the ab initio study of the mol. potential energy hypersurface has yielded revised data on predicted spectroscopic consts. for some conformers. Because of the combined effects of relaxation and conformational coalescence through large-amplitude vibrational motion, the revised data do not change the interpretation of the previous spectroscopic study of alanine. The barrier sepg. conformers 2 and 3 is predicted to be no more than 129 cm-1, so that in addn. conformer 1, only a single addnl. coalesced conformer (2,3), undergoing a large-amplitude motion in a double-min. potential, is expected to appear in the jet spectrum rather than two sep. species. The ab initio calcns. on alanine indicate that conformers 4 and 5 are sepd. by a low energy barrier and a similarly low barrier separates conformer 4 from the much lower energy conformer 1. The resulting coalesced conformer (4,5) is effectively a "ledge" on one wall of the potential well contg. conformer 1, and is occupied via an excited vibrational state of conformer 1. In this light, the coalesced conformer (4,5) is not expected to be obsd. in the jet, as the vibrational relaxation of low-frequency vibrational modes is known to be very efficient in free jet expansions. Overall, no conflicts are found to remain between the exptl. observations of jet spectra and the ab initio calcns. for glycine and alanine, provided that the scope of such calcns. is broadened from a narrower focus on equil. structures to consideration of the potential hypersurface. This approach should be important in the correct interpretation of the spectra of other multi-conformational species in free jet expansions.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XhsVaqsLw%253D&md5=c14e19f4a27403ab8964c5bc5179cae1
    6. 6
      Barone, V.; Biczysko, M.; Bloino, J.; Puzzarini, C. Glycine Conformers: A Never-Ending Story?. Phys. Chem. Chem. Phys. 2013, 15, 1358– 1363,  DOI: 10.1039/C2CP43884D
      Google Scholar
      6
      Glycine conformers: a never-ending story?
      Barone, Vincenzo; Biczysko, Malgorzata; Bloino, Julien; Puzzarini, Cristina
      Physical Chemistry Chemical Physics (2013), 15 (5), 1358-1363CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      The structure and vibrational spectra of a marginally stable conformer of glycine (usually referred to as VIp or ttc) recently detected in low-temp. matrixes have been characterized by a state-of-the-art computational approach allowing an overall quality for bond distances, rotational consts., conformational enthalpies and vibrational frequencies well within the chem. accuracy. The high accuracy of the computational results allows us to draw a fully consistent interpretation of the available exptl. data and to obtain a more complete characterization of an elusive glycine conformer.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhsVCqug%253D%253D&md5=b501f7ccc117bad20d69c86c48814560
    7. 7
      Robertson, E. G.; Simons, J. P. Getting into shape: Conformational and supramolecular landscapes in small biomolecules and their hydrated clusters. Phys. Chem. Chem. Phys. 2001, 3, 1– 18,  DOI: 10.1039/b008225m
      Google Scholar
      7
      Getting into shape: Conformational and supramolecular landscapes in small biomolecules and their hydrated clusters
      Robertson, Evan G.; Simons, John P.
      Physical Chemistry Chemical Physics (2001), 3 (1), 1-18CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      A review, with 171 refs. The last few years have seen a very rapid growth in understanding the influence of non-bonded, particularly hydrogen-bonded interactions, on the shapes and conformations of flexible mols., including those of pharmacol. or biol. importance, and of the supramol. structures of their hydrated clusters. This has come about through the combination of a wide range of newly developed spectroscopic strategies, many of which are laser-based, coupled with powerful and widely available ab initio codes for structural computation. The consequent rapid growth of a new link between the worlds of chem. and biophysics is surveyed in a review which introduces the range of present strategies, their origins, and their application to studies of neurotransmitters, amides and peptides, amino acids and nucleic acid bases. It concludes with a prospectus for the future.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXovFSgurY%253D&md5=73875e11c28ca6c604205d9a5fb6ca1d
    8. 8
      Dian, B. C.; Clarkson, J. R.; Zwier, T. S. Direct Measurement of Energy Thresholds to Conformational Isomerization in Tryptamine. Science 2004, 303, 1169– 1173,  DOI: 10.1126/science.1093731
      Google Scholar
      8
      Direct Measurement of Energy Thresholds to Conformational Isomerization in Tryptamine
      Dian, Brian C.; Clarkson, Jasper R.; Zwier, Timothy S.
      Science (Washington, DC, United States) (2004), 303 (5661), 1169-1173CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      Stimulated emission pumping (SEP)-hole filling spectroscopy and SEP-induced population transfer spectroscopy have been used to place narrow bounds on the energy thresholds for isomerization between individual reactant-product isomer pairs involving the seven conformational min. of tryptamine. The thresholds for isomerizing conformer A to all six other conformations divided into three groups at 750 wavenumbers (cm-1) (A → B, F), 1000 cm-1 [A → C(2)], and 1280 to 1320 cm-1 [A → D, E, and C(1)]. The appearance of the first band and the absence of the band below it were used to place upper and lower bounds to the barrier heights for each process. The thresholds for A → B and B → A isomerizations were also combined to det. the relative energies of these two lowest energy min. The combined data from all X → Y isomerizations identify important isomerization pathways on the potential energy surface linking the min.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXhsVWgtLc%253D&md5=b92b6927f1a123a20750b361eaf59b6e
    9. 9
      Snoek, L. C.; Robertson, E. G.; Kroemer, R. T.; Simons, J. P. Conformational landscapes in amino acids: Infrared and ultraviolet ion-dip spectroscopy of phenylalanine in the gas phase. Chem. Phys. Lett. 2000, 321, 49– 56,  DOI: 10.1016/S0009-2614(00)00320-1
      Google Scholar
      9
      Conformational landscapes in amino acids: infrared and ultraviolet ion-dip spectroscopy of phenylalanine in the gas phase
      Snoek, L. C.; Robertson, E. G.; Kroemer, R. T.; Simons, J. P.
      Chemical Physics Letters (2000), 321 (1,2), 49-56CODEN: CHPLBC; ISSN:0009-2614. (Elsevier Science B.V.)
      A full structural assignment of the most stable conformers of phenylalanine, based upon a combination of UV and IR ion-dip spectroscopy of the jet-cooled amino acid, coupled with high-level ab-initio computation is presented. The results are discussed in relation to aliph. amino acids to highlight the importance of ring side-chain interactions. The question of zwitterion formation is also discussed.
      >> More from SciFinder ®
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    10. 10
      Bakker, J. M.; Mac Aleese, L.; Meijer, G.; von Helden, G. Fingerprint IR spectroscopy to probe amino acid conformations in the gas phase. Phys. Rev. Lett. 2003, 91, 203003,  DOI: 10.1103/PhysRevLett.91.203003
      Google Scholar
      10
      Fingerprint IR Spectroscopy to Probe Amino Acid Conformations in the Gas Phase
      Bakker, Joost M.; Mac Aleese, Luke; Meijer, Gerard; von Helden, Gert
      Physical Review Letters (2003), 91 (20), 203003/1-203003/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)
      The IR absorption spectra are reported of different conformational isomers of gas phase amino acid mols. in the mol. fingerprint region of 330-1500 cm-1. The IR absorption spectra for 3 conformers of the amino acid tryptophan show absorption bands that uniquely identify the conformational structure of the mol. and that are well matched by d. functional theory calcns. The present observations hold great promise for future identification of conformational folding of larger mols. by their IR absorption characteristics.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXovF2mtbg%253D&md5=ae93ee38a07e1ff12429298c81a49c71
    11. 11
      de Vries, M. S.; Hobza, P. Gas-Phase Spectroscopy of Biomolecular Building Blocks. Annu. Rev. Phys. Chem. 2007, 58, 585– 612,  DOI: 10.1146/annurev.physchem.57.032905.104722
      Google Scholar
      11
      Gas-phase spectroscopy of biomolecular building blocks
      de Vries, Mattanjah S.; Hobza, Pavel
      Annual Review of Physical Chemistry (2007), 58 (), 585-612CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews Inc.)
      A review. Gas-phase spectroscopy lends itself ideally to the study of isolated mols. and provides important data for comparison with theory. In recent years, we have seen enormous progress in the study of biomol. building blocks in the gas phase. The motivation for such work is threefold:. (a) It is important to distinguish between intrinsic mol. properties and properties that result from the biol. environment. (b) Gas-phase spectroscopy of clusters provides insights into fundamental interactions and into microsolvation. (c) Gas-phase data support quantum-chem. calcns. This review focuses on the current status of (poly)amino acids and DNA bases. Recent results help elucidate structure and hydrogen-bonded interactions, as well as showcase a successful interplay between theory and expt.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXlslSit7Y%253D&md5=7d018c406624c9f6e19913c9a15ab5fa
    12. 12
      van Geenen, F. A. M. G.; Kranenburg, R. F.; van Asten, A. C.; Martens, J.; Oomens, J.; Berden, G. Isomer-Specific Two-Color Double-Resonance IR2MS3 Ion Spectroscopy Using a Single Laser: Application in the Identification of Novel Psychoactive Substances. Anal. Chem. 2021, 93, 2687– 2693,  DOI: 10.1021/acs.analchem.0c05042
      Google Scholar
      12
      Isomer-Specific Two-Color Double-Resonance IR2MS3 Ion Spectroscopy Using a Single Laser: Application in the Identification of Novel Psychoactive Substances
      van Geenen, Fred A. M. G.; Kranenburg, Ruben F.; van Asten, Arian C.; Martens, Jonathan; Oomens, Jos; Berden, Giel
      Analytical Chemistry (Washington, DC, United States) (2021), 93 (4), 2687-2693CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      The capability of an ion trap mass spectrometer to store ions for an arbitrary amt. of time allows the use of a single IR laser to perform two-color double resonance IR-IR spectroscopic expts. on mass-to-charge (m/z) selected ions. In this single-laser IR2MS3 scheme, one IR laser frequency is used to remove a selected set of isomers from the total trapped ion population and the second IR laser frequency, from the same laser, is used to record the IR spectrum of the remaining precursor ions. This yields isomer-specific vibrational spectra of the m/z-selected ions, which can reveal the structure and identity of the initially co-isolated isomeric species. The use of a single laser greatly reduces the exptl. complexity of two-color IR2MS3 and enhances its application in fields employing anal. MS. In this work, we demonstrate the methodol. by acquiring single-laser IR2MS3 spectra in a forensic context, identifying two previously unidentified isomeric novel psychoactive substances (NPS) from a sample that was confiscated by the Amsterdam Police.
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    13. 13
      Filsinger, F.; Küpper, J.; Meijer, G.; Hansen, J. L.; Maurer, J.; Nielsen, J. H.; Holmegaard, L.; Stapelfeldt, H. Pure samples of individual conformers: the separation of stereo-isomers of complex molecules using electric fields. Angew. Chem., Int. Ed. 2009, 48, 6900– 6902,  DOI: 10.1002/anie.200902650
      Google Scholar
      13
      Pure samples of individual conformers: The separation of stereoisomers of complex molecules using electric fields
      Filsinger, Frank; Kuepper, Jochen; Meijer, Gerard; Hansen, Jonas L.; Maurer, Jochen; Nielsen, Jens H.; Holmegaard, Lotte; Stapelfeldt, Henrik
      Angewandte Chemie, International Edition (2009), 48 (37), 6900-6902CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The authors demonstrate that electrostatic deflection, a classic mol. beam manipulation method that dates back to the 1920s, allows the spatial sepn. of the conformers of a neutral mol. when it is applied to intense beams of rotationally cold mols. produced by a state-of-the-art pulsed supersonic expansion source. The cis and trans conformers of 3-aminophenol are used herein as prototypical structural isomers of complex mols. From the precisely known rotational consts. and dipole moments, the energies of the rotational states of cis-3-aminophenol and trans-3-aminophenol are calcd. as a function of elec. field strength.
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    14. 14
      Chang, Y.-P.; Horke, D. A.; Trippel, S.; Küpper, J. Spatially-controlled complex molecules and their applications. Int. Rev. Phys. Chem. 2015, 34, 557– 590,  DOI: 10.1080/0144235X.2015.1077838
      Google Scholar
      14
      Spatially-controlled complex molecules and their applications
      Chang, Yuan-Pin; Horke, Daniel A.; Trippel, Sebastian; Kuepper, Jochen
      International Reviews in Physical Chemistry (2015), 34 (4), 557-590CODEN: IRPCDL; ISSN:0144-235X. (Taylor & Francis Ltd.)
      The understanding of mol. structure and function is at the very heart of the chem. and mol. sciences. Expts. that allow for the creation of structurally pure samples and the investigation of their mol. dynamics and chem. function have developed tremendeously over the last few decades, although 'there's plenty of room at the bottom' for better control as well as further applications. Here, we describe the use of inhomogeneous elec. fields for the manipulation of neutral mols. in the gas-phase, i.e. for the sepn. of complex mols. according to size, structural isomer, and quantum state. For these complex mols., all quantum states are strong-field seeking, requiring dynamic fields for their confinement. Current applications of these controlled samples are summarised and interesting future applications discussed.
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    15. 15
      Even, U. Pulsed Supersonic Beams from High Pressure Source: Simulation Results and Experimental Measurements. Adv. Chem. 2014, 2014, 636042,  DOI: 10.1155/2014/636042
      Google Scholar
      There is no corresponding record for this reference.
    16. 16
      de Nijs, A. J.; Bethlem, H. L. On deflection fields, weak-focusing and strong-focusing storage rings for polar molecules. Phys. Chem. Chem. Phys. 2011, 13, 19052– 8,  DOI: 10.1039/c1cp21477b
      Google Scholar
      16
      On deflection fields, weak-focusing and strong-focusing storage rings for polar molecules
      de Nijs, Adrian J.; Bethlem, Hendrick L.
      Physical Chemistry Chemical Physics (2011), 13 (42), 19052-19058CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      In this paper, we analyze elec. deflection fields for polar mols. in terms of a multipole expansion and derive a simple but rather insightful expression for the force on the mols. Ideally, a deflection field exerts a strong, const. force in one direction, while the force in the other directions is zero. We show how, by a proper choice of the expansion coeffs., this ideal can be best approximated. We present a design for a practical electrode geometry based on this anal. By bending such a deflection field into a circle, a simple storage ring can be created; the direct analog of a weak-focusing cyclotron for charged particles. We show that for realistic parameters a weak-focusing ring is only stable for mols. with a very low velocity. A strong-focusing (alternating-gradient) storage ring can be created by arranging many straight deflection fields in a circle and by alternating the sign of the hexapole term between adjacent deflection fields. The acceptance of this ring is numerically calcd. for realistic parameters. Such a storage ring might prove useful in expts. looking for an EDM of elementary particles.
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    17. 17
      Eppink, A. T. J. B.; Parker, D. H. Velocity map imaging of ions and electrons using electrostatic lenses: Application in photoelectron and photofragment ion imaging of molecular oxygen. Rev. Sci. Instrum. 1997, 68, 3477– 3484,  DOI: 10.1063/1.1148310
      Google Scholar
      17
      Velocity map imaging of ions and electrons using electrostatic lenses: Application in photoelectron and photofragment ion imaging of molecular oxygen
      Eppink, Andre T. J. B.; Parker, David H.
      Review of Scientific Instruments (1997), 68 (9), 3477-3484CODEN: RSINAK; ISSN:0034-6748. (American Institute of Physics)
      The application of electrostatic lenses is demonstrated to give a substantial improvement of the two-dimensional (2D) ion/electron imaging technique. This combination of ion lens optics and 2D detection makes "velocity map imaging" possible, i.e., all particles with the same initial velocity vector are mapped onto the same point on the detector. Whereas the more common application of grid electrodes leads to transmission redn., severe trajectory deflections and blurring due to the non-point source geometry, these problems are avoided with open lens electrodes. A three-plate assembly with aperture electrodes has been tested and its properties are compared with those of grid electrodes. The photodissocn. processes occurring in mol. oxygen following the two-photon 3dπ(3Σ1g-)(v=2, N=2)←X(3Σg-) Rydberg excitation around 225 nm are presented here to show the improvement in spatial resoln. in the ion and electron images. Simulated trajectory calcns. show good agreement with expt. and support the appealing properties of this velocity mapping technique.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXmtVantLo%253D&md5=a83796aa42f608d71271f5d397906508
    18. 18
      Chang, Y.-P.; Filsinger, F.; Sartakov, B.; Küpper, J. CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields. Comput. Phys. Commun. 2014, 185, 339– 349,  DOI: 10.1016/j.cpc.2013.09.001
      Google Scholar
      18
      CMIstark: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields
      Chang, Yuan-Pin; Filsinger, Frank; Sartakov, Boris G.; Kuepper, Jochen
      Computer Physics Communications (2014), 185 (1), 339-349CODEN: CPHCBZ; ISSN:0010-4655. (Elsevier B.V.)
      The Controlled Mol. Imaging group (CMI) at the Center for Free Electron Laser Science (CFEL) has developed the CMISTARK software to calc., view, and analyze the energy levels of adiabatic Stark energy curves of linear, sym. top and asym. top mols. The program exploits the symmetry of the Hamiltonian to generate fully labeled adiabatic Stark energy curves. CMISTARK is written in Python and easily extendable, while the core numerical calcns. make use of machine optimized BLAS and LAPACK routines. Calcd. energies are stored in HDF5 files for convenient access and programs to ext. ASCII data or to generate graphical plots are provided.
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    19. 19
      Xie, Y.; Su, H.; Tzeng, W. B. Rotamers of m-aminophenol cation studied by mass analyzed threshold ionization spectroscopy and theoretical calculations. Chem. Phys. Lett. 2004, 394, 182– 187,  DOI: 10.1016/j.cplett.2004.07.005
      Google Scholar
      19
      Rotamers of m-aminophenol cation studied by mass analyzed threshold ionization spectroscopy and theoretical calculations
      Xie, Yan; Su, Huawei; Tzeng, Wen Bih
      Chemical Physics Letters (2004), 394 (1-3), 182-187CODEN: CHPLBC; ISSN:0009-2614. (Elsevier B.V.)
      The vibrationally resolved spectra of selected rotamers of m-aminophenol were recorded by mass analyzed threshold ionization spectroscopy in connection with two-color resonant two-photon excitation scheme. The adiabatic ionization energies of the cis and trans rotamers are 61,460 ± 5 and 61,734 ± 5 cm-1, resp. The frequencies of modes 1 (breathing) and 18a (in-plane CH bending) are 744 and 1097 cm-1 for the cis, and 736 and 1104 cm-1 for the trans rotamer, resp. Different orientation of the OH with respect to the NH2 substituent only slightly influences these two modes.
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    20. 20
      Yatsyna, V.; Bakker, D. J.; Feifel, R.; Rijs, A. M.; Zhaunerchyk, V. aminophenol isomers unraveled by conformer-specific far-IR action spectroscopy. Phys. Chem. Chem. Phys. 2016, 18, 6275– 6283,  DOI: 10.1039/C5CP07426F
      Google Scholar
      20
      Aminophenol isomers unraveled by conformer-specific far-IR action spectroscopy
      Yatsyna, Vasyl; Bakker, Daniel J.; Feifel, Raimund; Rijs, Anouk M.; Zhaunerchyk, Vitali
      Physical Chemistry Chemical Physics (2016), 18 (8), 6275-6283CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Spectroscopic studies of mol. structure can strongly benefit from extending the conventional mid-IR range to the far-IR and THz regions, as low-frequency mol. vibrations provide unique fingerprints and high sensitivity to intra- and intermol. interactions. The gas-phase conformer specific far-IR spectra of aminophenol isomers, recorded in the spectral range of 220-800 cm-1 at the free-electron laser lab. FELIX in Nijmegen (the Netherlands), are reported. Many distinct far-IR vibrational signatures which are specific for the mol. structure of the different aminophenol isomers are revealed and assigned. The obsd. far-IR transitions of the NH2 wagging (inversion) motion were treated with a double-min. harmonic well potential model that has enabled us to obtain the inversion barrier values. Also, the limitations and capability of conventional DFT frequency calcns. to describe the far-IR vibrational modes are discussed.
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    21. 21
      Shinozaki, M.; Sakai, M.; Yamaguchi, S.; Fujioka, T.; Fujii, M. S1 ←S0 electronic spectrum of jet-cooled m-aminophenol. Phys. Chem. Chem. Phys. 2003, 5, 5044– 5050,  DOI: 10.1039/B309461H
      Google Scholar
      21
      S1-S0 Electronic spectrum of jet-cooled m-aminophenol
      Shinozaki, Minako; Sakai, Makoto; Yamaguchi, Shigeru; Fujioka, Tomoo; Fujii, Masaaki
      Physical Chemistry Chemical Physics (2003), 5 (22), 5044-5050CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      The S1 and S0 states of m-aminophenol were studied using laser induced fluorescence and dispersed fluorescence spectroscopy in a supersonic jet. The dispersed fluorescence spectra, obtained by exciting the bands at 34,109 and 34,469 cm-1, show the same vibronic structure, which suggests the coexistence of rotational isomers in m-aminophenol. A quantum chem. calcn. also supports the coexistence of rotational isomers. From the relative intensities in the spectrum and the calcd. stabilization energies of isomers, the bands are assigned to the origin of the cis- and trans-isomers, resp. The dispersed fluorescence spectra obtained by exciting the S1 vibronic bands were analyzed by comparing with the calcd. vibrational frequencies and IR and Raman spectra. From the anal., the S1 vibronic bands were assigned. A 1-to-one correspondence between the S1 and S0 vibrations is broken, and vibrational mixing due to Fermi resonance or the Duschinsky effect is suggested.
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    22. 22
      Even, U.; Jortner, J.; Noy, D.; Lavie, N.; Cossart-Magos, N. Cooling of large molecules below 1 K and He clusters formation. J. Chem. Phys. 2000, 112, 8068– 8071,  DOI: 10.1063/1.481405
      Google Scholar
      22
      Cooling of large molecules below 1 K and He clusters formation
      Even, U.; Jortner, J.; Noy, D.; Lavie, N.; Cossart-Magos, C.
      Journal of Chemical Physics (2000), 112 (18), 8068-8071CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)
      We present here the design details of a high-pressure pulsed valve that generates intense supersonic jets. The measured rotational contours of aniline indicate that temps. <0.5 K can be achieved before the formation of clusters with the He carrier gas. The spectral shifts and vibronic structure of anthracene-Hen clusters (n = 1-6) are showing some surprising features.
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    23. 23
      Hutzler, N. R.; Lu, H.-I.; Doyle, J. M. The buffer gas beam: An intense, cold, and slow source for atoms and molecules. Chem. Rev. 2012, 112, 4803– 4827,  DOI: 10.1021/cr200362u
      Google Scholar
      23
      The Buffer Gas Beam: An Intense, Cold, and Slow Source for Atoms and Molecules
      Hutzler, Nicholas R.; Lu, Hsin-I.; Doyle, John M.
      Chemical Reviews (Washington, DC, United States) (2012), 112 (9), 4803-4827CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. The authors discuss the properties of buffer gas beams, compare them with more std. beam techniques, and discuss both existing and proposed applications. The ability of this technique to deliver cold, slow, and intense beams of atoms and mols., including those that are difficult to produce with effusive or supersonic techniques, is fueling adoption of this technique for a wide range of applications. However, this beam prodn. technique is still relatively new and has not been as thoroughly characterized and developed as others.
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    24. 24
      Liu, J.; Koenig, J. L. Data Processing Techniques to Extract Pure-Component Spectra from Mixture Spectra and Their Application to Polymeric Systems. Anal. Chem. 1987, 59, 2609– 2615,  DOI: 10.1021/ac00148a017
      Google Scholar
      24
      Data processing techniques to extract pure-component spectra from mixture spectra and their application to polymeric systems
      Liu, Juwhan; Koenig, Jack L.
      Analytical Chemistry (1987), 59 (21), 2609-15CODEN: ANCHAM; ISSN:0003-2700.
      A nonlinear optimization technique was developed to ext. pure-component spectra from the mixt. spectra. The absorbances of the pure spectra and the concns. are variables to be optimized in the algorithm proposed. As constraints, nonnegativities of absorbances and concns. are applied where the concns. are used in terms of fractions. Through tests, three "pure" rotational isomer spectra of poly(ethylene terephthalate) were obtained. A least-squares procedure was utilized to expand the scope of the proposed method. This technique was applicable to all systems described by the Beer-Lambert law.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXlsFGis74%253D&md5=4336746e7721abbaf3d81c76adbc70cf
    25. 25
      Trippel, S.; Chang, Y.-P.; Stern, S.; Mullins, T.; Holmegaard, L.; Küpper, J. Spatial separation of state- and size-selected neutral clusters. Phys. Rev. A 2012, 86, 033202,  DOI: 10.1103/PhysRevA.86.033202
      Google Scholar
      25
      Spatial separation of state- and size-selected neutral clusters
      Trippel, Sebastian; Chang, Yuan-Pin; Stern, Stephan; Mullins, Terry; Holmegaard, Lotte; Kuepper, Jochen
      Physical Review A: Atomic, Molecular, and Optical Physics (2012), 86 (3-A), 033202/1-033202/6CODEN: PLRAAN; ISSN:1050-2947. (American Physical Society)
      We demonstrate the spatial sepn. of the prototypical indole(H2O) clusters from the various species present in the supersonic expansion of mixts. of indole and water. The major mol. constituents of the resulting mol. beam are H2O, indole, indole(H2O), and indole(H2O)2. It is a priori not clear whether such floppy systems are amenable to strong manipulation using elec. fields. Here, we have exploited the cold supersonic mol. beam and the electrostatic deflector to sep. indole(H2O) from the other mol. species as well as the helium seed gas. The exptl. results are quant. explained by trajectory simulations, which also demonstrate that the quantum-state selectivity of the process leads to samples of indole(H2O) in low-lying rotational states. The prepd. clean samples of indole(H2O) are ideally suited for investigations of the stereodynamics of this complex system, including time-resolved half-collision and diffraction expts. of fixed-in-space clusters. Our findings clearly demonstrate that the hydrogen bonded indole(H2O) complex behaves as a rigid mol. under our exptl. conditions and that it can be strongly deflected.
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    26. 26
      Franz, J.; Gianturco, F. A. Low-Energy Positron Scattering from DNA Nucleobases: The Effects from Permanent Dipoles. Eur. Phys. J. D 2014, 68, 279,  DOI: 10.1140/epjd/e2014-50072-0
      Google Scholar
      There is no corresponding record for this reference.

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