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  • 1
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    Interplay of intra- and intermolecular H-bonding in a progressively solvated macrocyclic peptide (2012)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2012-04-21
    Description: Studying solvation of a large molecule on an atomic level is challenging because of the transient character and inhomogeneity of hydrogen bonding in liquid water. We studied water clusters of a protonated macrocyclic decapeptide, gramicidin S, which were prepared in the gas phase and then cooled to cryogenic temperatures. The experiment spectroscopically tracked fine structural changes of the clusters upon increasing the number of attached water molecules from 1 to 50 and distinguished vibrational fingerprints of different conformers. The data indicate that only the first two water molecules induce a substantial change of the gramicidin S structure by breaking two intramolecular noncovalent bonds. The peptide structure remains largely intact upon further solvation, reflecting the interplay between the strong intramolecular and weaker intermolecular hydrogen bonds.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nagornova, Natalia S -- Rizzo, Thomas R -- Boyarkin, Oleg V -- New York, N.Y. -- Science. 2012 Apr 20;336(6079):320-3. doi: 10.1126/science.1218709.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Laboratoire de Chimie Physique Moleculaire, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22517854" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Gramicidin/*chemistry ; Hydrogen Bonding ; Nuclear Magnetic Resonance, Biomolecular ; Physicochemical Processes ; Protein Conformation ; Solubility ; Spectrophotometry, Infrared ; Spectrophotometry, Ultraviolet ; Water/chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
    Electronic Resource
    Electronic Resource
    Torsion–rotation analysis of OH stretch overtone–torsion combination bands in methanol (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 91-100 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report rotationally resolved spectra of jet-cooled methanol for the OH stretch overtones, 2v1 and 3v1, and for the torsional combinations, 2v1+v12, 2v1+2v12, 3v1+v12, and 3v1+2v12. The spectra are obtained by direct excitation from the vibrational ground state with an infrared laser pulse. Population in the resulting upper state levels is detected by infrared laser assisted photofragment spectroscopy (IRLAPS). Global fits of the spectra to the Herbst Hamiltonian yield the torsional and rotational parameters, including F, ρ, V3, and V6, for each OH stretch excited state. For each quantum of OH stretch excitation, we find that the torsional barrier height V3 increases by 40.9±1.9 cm−1 and the torsional inertial F decreases by 0.89±0.02 cm−1. With reference to ab initio calculations, we explain the increase in V3 in terms of changes in the electronic structure of methanol as the OH bond is elongated. For Δv12=1 we observe only transitions with ΔK=±1, and for Δv12=2 we observe only ΔK=0. We present a Franck–Condon model to explain these apparent selection rules and the overall pattern of intensity. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1421357
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  • 3
    Electronic Resource
    Electronic Resource
    Intramolecular energy transfer in highly vibrationally excited methanol. III. Rotational and torsional analysis (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 11359-11367 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report here torsional analysis of rotationally resolved spectra of the 3ν1, 5ν1, and 6ν1 (OH stretch) bands of jet-cooled methanol. The upper states are reached by a double resonance excitation scheme involving the selection of single rotational states in the ν1 fundamental band. Detection of the overtone transitions (nν1←ν1) is by infrared laser assisted photofragment spectroscopy (IRLAPS). The torsional tunneling frequency declines monotonically from 9.1 cm−1 in the vibrational ground state to 1.6 cm−1 at 6ν1. For the available rotational levels at 3ν1 (K=0–3) and 6ν1 (K=0,1), the pattern of torsional energies is approximately regular. To obtain the vibrational dependence of the torsional barrier V3, it was necessary to use the OH radical and HOOH as models for the vibrational dependence of the torsional inertial constant F. The assumed linear dependence of V3 on ν1 accounts for the torsional tunneling splittings at v1=0, 3, and 6 and for the pattern of the torsional energies. V3 increases by 40–45 cm−1 per quantum of OH excitation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479076
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  • 4
    Electronic Resource
    Electronic Resource
    Intramolecular energy transfer in highly vibrationally excited methanol. II. Multiple time scales of energy redistribution (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 11346-11358 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: State-selected spectra of the OH stretch overtones of methanol in the range of v1=3–8 reveal spectral splittings and broadenings that result from vibrational couplings within the molecule. We employ a two-color excitation technique in which an infrared pulse promotes jet-cooled methanol molecules to a single rotational state in v1=1 or 2 and a second visible or near-infrared laser pulse is scanned to record a vibrational overtone spectrum. The final vibrationally excited species are detected by infrared laser assisted photofragment spectroscopy. The implications of the spectra for vibrational dynamics in the time domain can be understood in terms of a hypothetical coherent excitation of relevant portions of the spectrum. The observed splittings and widths correspond to three time scales. The largest splittings imply subpicosecond oscillation of energy between the OH stretch and a combination with the C–H stretch (5ν1(if and only if)4ν1+ν2 and 6ν1(if and only if)5ν1+ν2) or a combination with the COH bend (7ν1(if and only if)6ν1+2ν6). Secondary time scales correspond to finer splittings and are thought to arise from low-order resonances with other vibrational states. We argue that the nonmonotonic energy dependence of the presence and extent of such secondary structure throughout the recorded spectra reflects the requirement of resonance with important zeroth-order states. The third time scale, represented by the widths of the narrowest features at each overtone level, reflects the onset of vibrational energy randomization. These widths increase exponentially with vibrational energy in the range 2ν1 up to 8ν1. At the highest energy (25 000 cm−1) the three time scales begin to converge, implying an irreversible decay of the OH stretch overtone in 300 fs. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479075
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  • 5
    Electronic Resource
    Electronic Resource
    Secondary time scales of intramolecular vibrational energy redistribution in CF3H studied by vibrational overtone spectroscopy (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6285-6292 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally resolved vibrational overtone spectra of several CH stretch bands of CF3H have been obtained using a combination of jet-cooling, infrared-optical double-resonance, and infrared laser assisted photofragment spectroscopy detection. The high selectivity and sensitivity of this combination allows measurement of spectral splittings that determine the secondary time scales of vibrational energy redistribution. The spectroscopic results show that in the energy region of the vCH=3–5 CH stretch levels, the vibrational energy would remain localized in the mixed CH stretch–bend states on time scales longer than 13–130 ps if coherently excited. This is as much as 2500 times longer than the time scale for energy transfer between the CH stretch and the HCF bend vibrations. Moreover, the results confirm that the energy redistribution dynamics are sensitive to the character of the bath states and not simply to the total vibrational energy. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472482
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  • 6
    Electronic Resource
    Electronic Resource
    Intramolecular energy transfer in highly vibrationally excited methanol. I. Ultrafast dynamics (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 8409-8422 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational overtone excitation of jet-cooled methanol, in combination with infrared laser assisted photofragment spectroscopy (IRLAPS) detection, reveals OH stretch bands that are significantly simplified with respect to room-temperature spectra. The simplification afforded by jet-cooling permits the observation of spectral splitting on the order of 50 cm−1 in the region of the 5ν1 OH stretch overtone band. Tracking this splitting as a function of OH stretch vibrational level in combination with isotopic substitution studies allows us to identify the perturbing state as the combination level involving four quanta of OH stretch and one quantum of CH asymmetric stretch, 4ν1+ν2. Careful examination of the spectra reveals that this strong interaction arises from a fourth-order anharmonic term in the Hamiltonian that couples the OH and CH ends of the molecule. These frequency domain results indicate that subsequent to coherent excitation of the 5ν1 band, methanol would undergo energy redistribution to the methyl part of the molecule on a time scale of ∼130 fs. This work also suggests that similar strong resonances may occur more generally in molecules that possess two different high-frequency oscillators in close proximity. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475041
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  • 7
    Electronic Resource
    Electronic Resource
    Rotational state selected vibrational overtone spectroscopy of jet-cooled molecules (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 1985-1988 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The combination of infrared-optical double resonance excitation with infrared laser assisted photofragment spectroscopy (IRLAPS) detection permits the measurement of rotationally resolved vibrational overtone spectra of jet-cooled CF3H. The IRLAPS detection technique is sufficiently selective to be able to discriminate against the dissociation of molecules in the ground state and the vCH=1 level used as an intermediate in the double resonance scheme. The combination of this selective detection technique with both supersonic cooling and double resonance produces J state resolved overtone spectra of the 42 vibrational overtone band. These spectra put a limit on the homogeneous linewidths of the rovibrational transitions of ∼0.5 cm−1. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469723
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  • 8
    Electronic Resource
    Electronic Resource
    IR spectrum of highly vibrationally excited osmium tetraoxide in the region of strong nonlinear interaction of vibrational modes (1990)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 94 (1990), S. 1294-1297 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100367a018
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  • 9
    Electronic Resource
    Electronic Resource
    Highly efficient optically pumped NH3 laser with near diffraction limited output (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 4041-4043 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present the design of a highly efficient, pulsed ammonia laser which is optically pumped by a commercial TEA CO2 laser and is line tunable in the spectral range of 780–930 cm−1. The power, spectral, and temporal characteristics of the laser have been investigated for different configurations of the optical cavity. Using a stable resonator, the laser operates with an efficiency of 24% (940 mJ) in a multiline configuration and 16.5% on a single line. Changing the resonator to an unstable configuration produces a diffraction limited output on a single line with an efficiency of 13%. These output characteristics make this laser suitable for experiments in the field of infrared multiphoton dissociation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149247
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  • 10
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    Highly efficient optically pumped NH3 laser with near diffraction limited output (1998)
    American Institute of Physics
    Details
    Publication Date: 1998-12-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics
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