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  • 1
    Electronic Resource
    Electronic Resource
    Evidence of vibrational mode coupling in 2-fluoroethanol via high-resolution infrared spectroscopy in a molecular beam (1991)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 113 (1991), S. 4342-4343 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00011a054
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  • 2
    Electronic Resource
    Electronic Resource
    Time-resolved spectroscopy of tryptophan conformers in a supersonic jet (1988)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 110 (1988), S. 1352-1355 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00213a005
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrafast excited-state proton transfer in 1-naphthol (1984)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 106 (1984), S. 7286-7288 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00335a093
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  • 4
    Electronic Resource
    Electronic Resource
    Unimolecular reactions in isolated and collisional systems: Deuterium isotope effect in the photoisomerization of stilbene (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6697-6707 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The isomerization of t-stilbene (stilbene h12 ) and three deuterated derivatives has been studied in a supersonic expansion, the thermal gas phase, and solution. In the jet we find that almost all effect of full deuteration (stilbene d12 ) is produced by deuteration of the two ethylinic hydrogens only (stilbene d2 ). Complete deuteration of the phenyl rings (stilbene d10 ) has rather little influence on the decay of the jet-cooled molecule. Nonexponential decays are found at intermediate excess energies in the jet-cooled system, with the degree of nonexponentiality decreasing with increasing excess energy. The ordering of the decay rates observed in the jet is not consistent with previous RRKM calculations of the isomerization rates of stilbene h12 and d2. Using similar parameters the calculations consistently place the stilbene d2 and stilbene d10 curves in the wrong order. Our results suggest extensive but not complete vibrational relaxation in the isolated molecule. Vibrational redistribution rapidly becomes complete in the presence of buffer gas. In thermal samples the isomerization rates of stilbene h12 and stilbene d10 are identical over a wide range of solvents and temperatures. By contrast the isomerization rates in stilbene d2 and stilbene d12 are 1.4 and 1.5 times slower than in stilbene h12. Again, these ratios appear constant over a wide range of experimental conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455342
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  • 5
    Electronic Resource
    Electronic Resource
    Rotationally resolved electronic spectroscopy of tryptamine conformers in a supersonic jet (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 85-90 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have observed the high resolution fluorescence excitation spectrum of the molecule tryptamine in the gas phase. At low resolution the spectrum contains six features which have been assigned as the origins of different conformers of the tryptamine molecule. At high resolution the rotational structure in each of these features has been resolved, and the rotational structure of five of the features has been analyzed. This analysis has provided information about the geometries of the different conformers. Two conformers, labeled A and F, have the amino group of the molecule gauche to the indole ring, while conformer D has the amino group nearly eclipsed by the indole ring. Conformer B has a rotational structure identical to that of conformer A, while the rotational structure of conformer E is identical to that of conformer D. It is suggested that the pairs of conformers with identical rotational structure are related to each other by rotation about the Cα–N bond, such a rotation moving only hydrogen atoms. Feature C consists of two overlapped conformers, and it is suggested that these conformers have the amino group trans to the indole ring. The direction of the transition moment is measured for five of the conformers and is found to be identical for all conformers within the precision of the measurement. The direction of the transition moment indicates that the transition is to the 1Lb excited electronic state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455464
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  • 6
    Electronic Resource
    Electronic Resource
    High-pressure studies of rotational reorientation dynamics: The role of dielectric friction (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 5810-5821 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Picosecond, time-resolved, fluorescence depolarization spectroscopy is used to measure the rotational reorientation times of rhodamine 6G (R6G) and p-terphenyl (PTP) as a function of solvent viscosity. The viscosity is varied either by changing the solvent or by changing the pressure in a single solvent. The differences between the two molecules, PTP and R6G, provide a means of evaluating the role of solute structure and solute–solvent interactions on the dynamics of rotational reorientation. The rotational behavior of PTP is well described by simple hydrodynamic models as embodied by the Stokes–Einstein–Debye equation. In contrast, the rotational reorientation dynamics of the charged molecule R6G are not well described by these models. It is demonstrated that dielectric friction plays an important role in governing the rotational motion of charged molecules in polar solvents. When the solvent dielectric properties are varied, the dielectric friction model accurately predicts the observed experimental trends under a wide variety of experimental conditions. This model is also shown to explain anomalous effects previously attributed to the presence of solute–solvent hydrogen bonded complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449661
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  • 7
    Electronic Resource
    Electronic Resource
    High resolution infrared spectroscopy of pyrazine and naphthalene in a molecular beam (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 4077-4086 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The high resolution infrared spectrum of pyrazine and naphthalene were measured in a molecular beam in the vicinity of the C–H stretching transition. The rotational structure in the spectrum of pyrazine from 3065–3073 cm−1 reveals that the C–H stretch is coupled to one other vibrational mode in the molecule. The mode coupling is manifested in the spectrum as two overlapping vibrational bands. Each of these two bands are well modeled by an asymmetric top/rigid rotor Hamiltonian. The lack of any angular momentum dependence on the coupling indicates that the vibrations are coupled by an anharmonic mechanism. The magnitude of the coupling matrix element was determined to be 0.36 cm−1. The rotational structure in the spectrum of naphthalene from 3063–3067 cm−1 reveals that except for several local perturbations, the spectrum is well modeled by an asymmetric top/rigid rotor Hamiltonian. The local perturbations include transitions that are split into doublets as well as transitions that have been shifted from their expected positions. The magnitude of the average coupling matrix element for the doublets was determined to be 0.0016 cm−1. A comparison between the vibrational mode coupling in pyrazine and naphthalene indicates that mode coupling does not correlate with the density of states in the two molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466345
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  • 8
    Electronic Resource
    Electronic Resource
    Linking structure and vibrational mode coupling using high-resolution infrared spectroscopy: A comparison of gauche and trans 1-chloro-2-fluoroethane (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 75-89 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The high-resolution infrared spectrum of 1-chloro-2-fluoroethane in a molecular beam was collected over the 2975–2994 cm−1 spectral region. The spectral region of 2975–2981 cm−1 contains a symmetric C–H stretching vibrational band of the gauche conformer containing the 35Cl isotope. The spectral region of 2985–2994 cm−1 contains three vibrational bands of the trans conformer. Two of the three bands are assigned as an antisymmetric C–H stretch of each of the two different chlorine isotopes. The third band is assigned as a symmetric C–H stretch of the 35Cl isotope. The gauche conformer of 1-chloro-2-fluoroethane showed doublet patterns similar to those previously observed in 1,2-difluoroethane. The model for 1,2-difluoroethane is further refined in the present work. These refinements suggest that the coupling dark state in 1,2-difluoroethane is composed of 1 quantum C–H bend, 1 quantum C–C stretch, and 12 quanta of torsion. For 1-chloro-2-fluoroethane the dark state could not be identified due to a small data set. The trans conformer of 1-chloro-2-fluoroethane showed no evidence of mode coupling in the three vibrational bands. Including 2-fluoroethanol in this series of molecules, the extent of vibrational mode coupling did not correlate with the density of states available for coupling. Therefore, density of states alone is insufficient to explain the observed trend. A correlation was observed between the degree of intramolecular interaction and vibrational mode coupling. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469447
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  • 9
    Electronic Resource
    Electronic Resource
    Optothermal detection of nonradiative relaxation channels in electronically excited molecules (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 145-154 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Optothermal detection has been used to observe nonradiative relaxation channels in aniline, p-bromoaniline, and trans-stilbene. p-Bromoaniline has no detectable fluorescence due to a heavy atom effect which increases the rate of intersystem crossing to the triplet state. An optothermal spectrum of p-bromoaniline was observed with the origin at 32 625 cm−1. For trans-stilbene, the differences between the laser excitation spectrum and the optothermal spectrum of the S1 state clearly show the onset of isomerization at ∼1250 cm−1 above the origin. Absolute quantum yields of fluorescence, Franck–Condon factors, nonradiative rates, and radiative rates have been obtained for a series of vibronic transitions. For low energy vibrational states, there is good agreement between the current study and previous work. For vibrational energies above the barrier of isomerization, predicted quantum yields do not agree with our experimental results. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469385
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  • 10
    Electronic Resource
    Electronic Resource
    High resolution infrared spectroscopy of cyclobutane: A study of vibrational mode coupling involving large amplitude, low frequency modes (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 8590-8601 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The high resolution IR spectrum of cyclobutane in a supersonic molecular beam was obtained for the region of 2981 to 2991 cm−1. The spectrum reveals four overlapping bands suggestive of vibrational mode coupling in the C–H stretching region. Ground state combination differences demonstrate that these bands originate from two different ground states, the symmetric and asymmetric ring puckering states. Evidence of vibrational mode coupling is present in all four bands. The coupling depends on both J and the symmetry of the puckering state. A model coupling scheme involving two qualitatively different types of couplings is developed to explain the observed spectrum. Symmetry restrictions and the interaction between molecular rotation and ring puckering qualitatively accounts for the dramatically different coupling behavior between the two ring puckering states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466763
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