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  • 1
    Electronic Resource
    Electronic Resource
    A new determination of the dissociation energy of acetylene (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5160-5163 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new upper bound for the dissociation energy of acetylene, D00(HCC–H) =529.89(±0.01) kJ/mol, has been determined by Stark anticrossing spectroscopy. The zero-pressure extrapolated (unimolecular) decay rates of levels of S1 (A˜ 1Au) v'3=2 and 3 (quanta of the trans-bending vibration) increase upon application of an electric field of 113 kV/cm. We attribute this increase in molecular decay rate to predissociation rather than any other Stark-induced nonradiative or radiative phenomenon. The lowest level (v'3 =2, J'=2, K'=1) from which we have observed an increase in decay rate (i.e., predissociation) has an internal energy of 44 295.65 cm−1 relative to v=0, J=0 of S0 (X˜ 1∑+g). This corresponds to a value about 24 kJ/mol lower then the consensus upper bound result from four different recent experimental determinations (including one of ours) as well as current ab initio results. The new value agrees, however, with earlier work and with recent modeling studies of acetylene pyrolysis kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457614
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  • 2
    Electronic Resource
    Electronic Resource
    On the preponderance of near-prolate rotors among polyatomic molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4100-4100 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The distribution with respect to Ray's asymmetry parameter κ of polyatomic molecules listed in the Landolt–Börstein tables is skewed towards κ=−1 (prolate rotor limit). A plausible definition of "randomly shaped'' objects leads to a prediction with this qualitative behavior but less strongly biased toward κ=−1 than the experimental distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453815
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  • 3
    Electronic Resource
    Electronic Resource
    A three-mode large-amplitude model for the ground electronic state of CH3I (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3147-3158 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A large-amplitude model is developed to describe the three A1 vibrational modes of CH3 I. The use of a relatively simple choice of curvilinear coordinates is shown to be suitable for the regions of the ground electronic state probed by resonance Raman experiments. The essentials of the earlier two-mode linear triatomic model are regained by an adiabatic separation of the symmetric C–H stretch coordinate, but with a slightly different kinetic energy operator. A potential energy surface is constructed for the CH3 umbrella and C–I stretching coordinates. The resulting two-mode levels agree with almost all of the observed transitions to within experimental uncertainty up to 9300 cm−1 . Use of all three modes allows us to approximately apply the same potential surface to CD3 I. It is also hoped that the present model will be useful in excited state calculations, and in other CX3 Y molecules as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453959
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  • 4
    Electronic Resource
    Electronic Resource
    Time domain formulation of optical spectroscopy involving three potential energy surfaces (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 4322-4340 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We consider the computation of electronic absorption and Raman scattering spectra when three potential energy surfaces are involved; namely, a ground state surface coupled radiatively to one excited state which is in turn coupled nonadiabatically to a second excited surface. Frequency domain formulas are given for both kinds of spectra under the (standard) assumption of weak radiative coupling, but with no restriction on the nonadiabatic coupling strength. These formulas are transcribed into the time domain so that the computational burden is shifted to determination of the temporal evolution of wave packets simultaneously on both excited surfaces. We show how to implement the appropriate dynamics utilizing a perturbation expansion in the nonadiabatic coupling strength. Finally, extensive numerical results are presented for a one dimensional test system. Lowest order nonvanishing perturbation theory corrections are found to account accurately for nonadiabatic effects of ∼15%. Concentrating mainly on low resolution spectra such as arise in the case of direct photodissociation, the general effect of nonadiabatic coupling is observed to be broadening of absorption spectra and suppression of Raman scattering intensities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451805
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  • 5
    Electronic Resource
    Electronic Resource
    Time-dependent analysis of the Hartley absorption band and resonance Raman spectra in ozone (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 1525-1537 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A detailed investigation is made of the short-time dynamics involved in the Hartley absorption band in ozone and the related resonance Raman spectra for low vibrational overtones. A quadratic expansion of the X 1A1 and dissociative 1B2 potential energy surfaces involved leads to an analytic calculation of three-mode vibrational correlation functions, which are then Fourier-transformed to obtain the absorption and Raman spectra. A type of time-dependent perturbation theory is used to approximate the effects of including anharmonic terms in the expansion of the upper state. It is concluded that an improvement in the description of the Raman spectra will require at the least a major modification of the parabolic barrier behavior along the antisymmetric stretch coordinate and, better, a large-amplitude-motion treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453263
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  • 6
    Electronic Resource
    Electronic Resource
    Recurrences in the autocorrelation function governing the ultraviolet absorption spectra of O3 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7638-7653 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The approximate dipole–dipole autocorrelation function corresponding to UV photoabsorption in the Huggins and Hartley bands of ozone is obtained by Fourier transformation of the T=195 K data measured by Freeman, Yoshino, Esmond, and Parkinson [Planet. Space Sci. 32, 239 (1984)]. Weak structure seen at vibrational resolution in the broad absorption bands, previously unassigned, is shown to correspond predominantly to 4–5 small recurrent features in the autocorrelation function during the first 130 fs. These time-dependent features are each assigned to particular types of unstable periodic or nearly periodic orbits in the classical dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457234
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  • 7
    Electronic Resource
    Electronic Resource
    Evidence of quantum ergodicity in stimulated emission pumping spectra of acetylene (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 466-475 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the stimulated emission pumping (SEP) spectra of the acetylene X˜ 1∑+g state near 27 900 cm−1 of vibrational excitation for evidence of quantum ergodicity. The spectra consists of clumps of narrowly spaced lines which arise from transitions into levels with the same lower state J‘ value. Thus, the structure within each clump is purely vibrational. We apply criteria for spectral ergodicity and examine nearest-neighbor spacing distributions to test the spectra for signs of ergodic molecular dynamics. The criteria applied suggest that the molecular dynamics is nearly ergodic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449561
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  • 8
    Electronic Resource
    Electronic Resource
    Resonance Raman spectroscopy in the dissociative A band of nitrosyl chloride (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 6631-6640 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Resonance Raman spectra measured for ClNO photoexcited at 212.5, 219, and 222 nm produce evidence that the strong transition at the vacuum ultraviolet end of the merged A band system dominates to wavelengths as long as 222 nm. The spectral resolution is sufficient to enable definitive assignments of excited vibrational levels in the ground electronic state, several of which have not been previously observed. A curvilinear coordinate model of the ground state potential surface around the Franck–Condon region has been constructed. This model yields vibrational eigenvalues in excellent agreement with all known transitions. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1355656
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  • 9
    Electronic Resource
    Electronic Resource
    Fluorescence and stimulated emission S1 → S0 spectra of acetylene: Regular and ergodic regions (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 453-465 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The S1 → S0 transition of acetylene has been studied by spontaneous and stimulated emission. In the spontaneous emission studies, we report new data on low-resolution dispersed fluorescence from an unrelaxed single rotational level of S1. Transitions into S0 levels from the zero-point level up to ∼28 000 cm−1 of vibrational energy are reported. Earlier investigations of the emission from relaxed acetylene in a neon matrix and of partially relaxed fluorescence from a radio frequency discharge in acetylene have been reexamined and reinterpreted in the light of the present work. The stimulated emission study employed stimulated emission pumping (SEP) for high-resolution investigations of two regions of S0 energies, one near 9550 cm−1 and another near 27 900 cm−1. Definite vibrational assignments were possible for most of the features observed in the lower energy region. This allowed the determination of two new vibrational constants, y224 and y244. The region near 27 900 cm−1 reveals a hitherto unobserved kind of vibrational behavior. A series of broad features (∼1.5 cm−1 wide) appear at intervals of ∼10 cm−1 in broadband SEP scans. At higher resolution, each of these is found to consist of many individual lines with DUMP-laser limited linewidths. This structure is discussed in terms of the Franck–Condon principle for the S1 → S0 transition and the possible relevance of the observed behavior to theories of ergodicity in quantum systems. A detailed treatment of the data, using various measures of quantum ergodicity, appears in the following paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449560
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  • 10
    Electronic Resource
    Electronic Resource
    Wavelets in curvilinear coordinate quantum calculations: H2+ electronic states (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 3548-3557 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Multiscale wavelets are used to solve the quantum eigenvalue equations for the hydrogen molecular ion H2+ in the Born–Oppenheimer approximation. Normally restricted to Cartesian systems, "wavelets on the interval" (a normal wavelet family augmented by special edge functions) have recently been applied to such boundary value problems as the hydrogen atom in spherical polar coordinates [J. Mackey, J. L. Kinsey, and B. R. Johnson, J. Comp. Phys. 168, 356 (2001)]. These methods are extended here to ground and excited electronic states of the simplest molecule, for which the electronic Hamiltonian is separable in confocal elliptic coordinates. The set of curvilinear coordinate quantum systems for which wavelet bases have been applied is thus enlarged. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1494798
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