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  • 1
    Electronic Resource
    Electronic Resource
    Test of variational transition state theory and multidimensional semiclassical transmission coefficients methods against accurate quantal rate constants for H + H2/HD, D + H2, and O + H2/D2/HD, including intra- and intermolecular kinetic isotope effects (1986)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 108 (1986), S. 2876-2881 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00271a015
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  • 2
    Electronic Resource
    Electronic Resource
    Theoretical studies of surface enhanced Raman scattering (1984)
    s.l. : American Chemical Society
    Accounts of chemical research 17 (1984), S. 370-376 
    Details
    ISSN: 1520-4898
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ar00106a005
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  • 3
    Electronic Resource
    Electronic Resource
    Tunnelling in bimolecular collisions (1987)
    s.l. : American Chemical Society
    Chemical reviews 87 (1987), S. 81-89 
    Details
    ISSN: 1520-6890
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/cr00077a004
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  • 4
    Electronic Resource
    Electronic Resource
    Collisional excitation of CO by 2.3 eV H atoms (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1141-1149 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational and rotational distributions of CO excited by collisions with 2.3 eV H atoms have been obtained by monitoring the products with vacuum ultraviolet (VUV) laser induced fluorescence. Translational-to-vibrational (T→V) transfer is dominated by the dynamics of collisions occurring in the two wells on the H+CO potential energy surface, one characterizing the HCO radical and the other characterizing COH. The measured vibrational distributions agree well with the results of trajectory calculations performed on the ab initio potential energy surface of Bowman, Bittman, and Harding (BBH). The measured rotational distributions show two significant differences from the calculated ones. First, for v=0 the experiments find more population in J〈15 than predicted. This discrepancy may be due to errors in the repulsive part of the BBH surface that is outside the HCO and COH wells, but inside the van der Waals well. Second, for v=1, the experimental distribution is flat from J=0 to J=10, whereas the calculated one rises from near zero at J=0 to a peak at J=12. This discrepancy appears to be the result of an excessively high ab initio estimate (by a few tenths of an eV) of the barrier for H atom addition to CO to form COH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460020
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  • 5
    Electronic Resource
    Electronic Resource
    A centrifugal-sudden distorted-wave study of isotope effects for the reactions Cl+HCl→ClH+Cl and Cl+DCl→ClD+Cl (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5544-5551 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A quantum calculation has been performed using the centrifugal-sudden distorted-wave (CSDW) method for the three-dimensional Cl+DCl→ClD+Cl reaction. Three potential energy surfaces have been employed: two extended London–Eyring–Polanyi–Sato surfaces [denoted Bondi–Connor–Manz–Römelt (BCMR) and Persky–Kornweitz 3 (PK3)] and a scaled and fitted ab initio one (denoted sf-POLCI). Quantities calculated include: cumulative reaction probabilities, integral cross sections, rotational product distributions, and rate coefficients. Differential cross reactions are also reported for the PK3 surface, which are compared with the results from a simple semiclassical optical model (close agreement is found). We also compare the Cl+DCl results with earlier CSDW calculations for Cl+HCl→ClH+Cl. The rotational distributions are strongly perturbed by isotope substitution and are sensitive to variations in the potential surface. In contrast, the H and D rate coefficients for all three surfaces agree with experimental values, except for Cl+DCl on PK3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459624
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  • 6
    Electronic Resource
    Electronic Resource
    Nonadiabatic effects in photodissociation dynamics: A quantum mechanical study of ICN photodissociation in the A continuum (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 1634-1642 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photodissociation dynamics of ICN in the A continuum has been studied using a quantum coupled-channel method. The two-state empirical potential energy surfaces derived by Goldfield et al. are used in our calculations, and the CN bond is assumed frozen throughout the dissociation (rigid-rotor approximation). The excited state dynamics involving nonadiabatic transitions between the I and I* channels is treated in a diabatic representation. The CN rotational distributions have been obtained for several wavelengths and zero total angular momentum by calculating the appropriate Franck–Condon integral. Bimodal structure in CN rotational distributions is obtained in the quantum calculations, but the width of the peaks is narrower than in semiclassical results for the same surfaces. Discrepancies between quantum and semiclassical results are also found in the total cross-section and in the I*/I branching ratio. Comparison of our quantum results with experiment indicates that the potentials derived from the semi-classical calculations are not accurate enough to describe the ICN photodissociation dynamics. Further modifications are needed for the potential energy surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458097
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  • 7
    Electronic Resource
    Electronic Resource
    A three dimensional quantum reactive scattering study of the I+HI reaction and of the IHI− photodetachment spectrum (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4847-4854 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper, we present the results of coupled channel hyperspherical reactive scattering calculations on the reaction I+HI→IH+I using a semiempirical potential surface. Only the J=0 partial wave is considered. The bimolecular reaction probability is found to exhibit two sharp resonant peaks at energies below threshold for direct reaction. The resonances are associated with transition state quantum numbers (ν1ν2ν3)=(100) and (200), and their energies are in excellent agreement with the result of L2 calculations due to Clary and Connor, and to Bowman and Gazdy. At higher energy the reaction is dominated by rotational threshold effects, and then below the HI(ν=1) energetic threshold, additional resonances are found which correspond to quantum numbers (002), (102), (202), and (302). Franck–Condon factors associated with photodetachment of IHI− have also been calculated, and these show mainly direct scattering threshold behavior at low energies (E〈0.30 eV), with the (100) and (200) resonances contributing only slightly. Resonant behavior is dominant at higher energies (0.3–0.4 eV) where the (002) resonance especially contributes. Agreement of our calculated photodetachment spectra with experimental results due to Neumark and co-workers is good provided that an 0.08 eV energy shift is made in the calculated spectra. This shift is probably due to an incorrect energy barrier on the semiempirical surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456578
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  • 8
    Electronic Resource
    Electronic Resource
    Theoretical studies of collisional energy transfer in highly excited molecules: The importance of intramolecular vibrational redistribution in successive collision modeling of He+CS2 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 770-779 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we present a new method for studying the collisional relaxation of highly excited molecules in low density gases known as the redistributed successive collisions (RSC) method, and we apply it to the relaxation of CS2 by He at 300 K in the vibrational energy range E=32 640–3180 cm−1. The RSC method involves calculating sequences of collisions, subject to the assumption that rapid vibrational redistribution occurs between each collision. As a result, initial conditions for each trajectory in a sequence are sampled from a microcanonical ensemble that is defined by the final energy and angular momentum of the previous trajectory. The application to He+CS2 leads to 〈ΔE〉's that vary linearly with E over the entire energy range considered. The agreement of these 〈ΔE〉's with measured values is good, but there is a qualitative difference in the E dependence of 〈ΔE〉 over part of the range of E's. We also examine a second successive collision method that is more appropriate for high-density gases in which the internal coordinates and momenta are conserved (i.e., not redistributed) between collisions (CSC method). We find that a substantial fraction of the CSC ensembles (∼50%) exhibit extremely slow relaxation which in some cases is not complete even after 80 000 collisions. This unphysical result appears to be a classical artifact, and it leads to very small 〈ΔE〉's at medium to low E and a stronger dependence of 〈ΔE〉 on E (close to quadratic) at high E. Omission of these slowly relaxing ensembles from the CSC ensemble average leads to CSC 〈ΔE〉's which are nearly identical to those from the RSC calculation. An analysis of the distribution of energy among vibrational modes in the CSC calculations indicates that the slow relaxation arises from energy becoming frozen in the asymmetric stretch of CS2. The influence of the CS2 intramolecular dynamics on the collisional relaxation is considered, and we find evidence of abrupt collision induced intramolecular energy redistribution due to nonlinear resonance formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455200
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  • 9
    Electronic Resource
    Electronic Resource
    Phase space bottlenecks: A comparison of quantum and classical intramolecular dynamics for collinear OCS (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 3263-3272 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We compare quantum and classical mechanics for a collinear model of OCS at an energy (20 000 cm−1) where Davis [J. Chem. Phys. 83, 1016 (1985)] had previously found that phase space bottlenecks associated with golden mean tori inhibit classical flow between different chaotic regions in phase space. Accurate quantum eigenfunctions for this two mode system are found by diagonalizing a large basis of complex Gaussian functions, and these are then used to study the evolution of wave packets which have 20 000 cm−1 average energies. By examining phase space (Husimi) distributions associated with the wave functions, we conclude that these golden mean tori do indeed act as bottlenecks which constrain the wave packets to evolve within one (or a combination of) regions. The golden mean tori do not completely determine the boundaries between regions, however. Bottlenecks associated with resonance trapping and with separatrix formation are also involved. The analysis of the Husimi distributions also indicates that each exact eigenstate is nearly always associated with just one region, and because of this, superpositions of eigenstates that are localized within a region remain localized in that region at all times. This last result differs from the classical picture at this energy where flow across the bottlenecks occurs with a 2–4 ps lifetime. Since the classical phase space area through which flux must pass to cross the bottlenecks is small compared to (h-dash-bar) for OCS, the observed difference between quantum and classical dynamics is not surprising. Examination of the time development of normal mode energies indicates little or no energy flow quantum mechanically for wave packet initial conditions. Classical trajectory bundles constructed from the wave packet phase space distributions also show little or no energy flow even though noticeable flow is observed for more localized bundles chosen from the turnstile associated with flow through the bottleneck.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451985
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  • 10
    Electronic Resource
    Electronic Resource
    A centrifugal-sudden distorted wave study of the Cl+HCl→ClH+Cl reaction using a "tight-bend'' potential energy surface (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4893-4898 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quantum calculations of product rotational distributions, cross sections and rate coefficients have been performed for the Cl+HCl→ClH+Cl reaction using the centrifugal-sudden distorted-wave (CSDW) technique. The CSDW method has been shown to be nearly exact at low total energies where the total reaction probability for each partial wave is small. The potential energy surface used is the extended London–Eyring–Polanyi–Sato surface No. 3 of Persky and Kornweitz. This surface has a tighter bending potential near the saddle point than many of the other commonly used Cl+HCl potentials. This difference in bending potential is found to have a profound influence on the product rotational distributions, producing much colder HCl molecules than is the case for the other potentials. In contrast, quantities such as rate coefficients and cumulative reaction probabilities are found to be only weakly sensitive to the strength of the bending potential. Comparison with quasiclassical trajectory results shows reasonable agreement with respect to the shape of the rotational distributions, but the magnitudes of the cross sections and rate coefficients are substantially different.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457706
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