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  • 11
    Electronic Resource
    Electronic Resource
    Calculations on the van der Waals spectrum of Ar–tetrazine (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 5875-5884 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The van der Waals bound states of Ar–tetrazine are calculated by a method which treats the tetrazine fragment as a rigid rotor, but which is otherwise exact within the Born–Oppenheimer approximation. The results are used to obtain frequencies and intensities for transitions between van der Waals states in the S1←S0 electronic spectrum of the complex. Selection rules for such transitions are derived using permutation–inversion symmetry arguments. The normal rigid molecule selection rules are relaxed due to coupling between the low frequency van der Waals vibrations and the overall rotation of the complex, leading to the possibility of observing single excitation of the nontotally symmetric van der Waals bending modes. Transition intensities for van der Waals stretching excitation are predicted much smaller than experiment and various possible explanations for this disagreement are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458357
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  • 12
    Electronic Resource
    Electronic Resource
    Vibrationally inelastic collision cross sections of He+SO2: Distorted wave approach (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3509-3515 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational excitation and relaxation cross sections of He colliding with SO2 molecule are evaluated. The results obtained rely on several approximate methods. The infinite-order-sudden approximation provides the framework for treating the rotational motion, while the vibrational processes are described using both exact close-coupling and approximate distorted wave techniques. The latter scheme permits the computations to be extended to much higher collisional energies than so far reported in the literature. Vibrational excitation and relaxation cross sections are presented over a range of collision energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456881
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  • 13
    Electronic Resource
    Electronic Resource
    Rate constant calculations on the C++HCl reaction (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7216-7228 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Calculations of the rate constant at several temperatures for the reaction C+(2P)+HCl(X 1∑+) are presented. A quantum mechanical treatment of ion–molecule reactions which combines a rotationally adiabatic capture with a centrifugal sudden approximation is used to obtain rotational state-selective cross sections and rate constants. Ab initio SCF (TZ2P) methods are employed to obtain the long- and short-range electronic potential energy surfaces. This study indicates the necessity of incorporating the multisurface nature of open-shell systems for some ion–molecule reactions. The spin–orbit interactions are treated within a semiquantitative model. Results fare better than previous calculations which used only classical electrostatic forces, and are in good agreement with CRESU and SIFT measurements at 27, 68, and 300 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456251
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  • 14
    Electronic Resource
    Electronic Resource
    Calculation of van der Waals spectra for H2HF, D2HF, and H2DF (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6334-6349 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Calculations of spectra for the excitation of the van der Waals modes in the weakly bound complexes H2HF, D2HF, and H2DF are reported. An ab initio potential energy surface has been computed using the coupled electron pair approximation with a large basis set. The rovibrational bound states for the complexes are calculated using a variational method. A self-consistent field approach is used to optimize the basis sets for bending and stretching motion in the van der Waals complex. The calculated spectra compare very well with those measured in near-infrared experiments. The computations provide a systematic analysis of the relative stability and rigidity of the different complexes, the very large zero-point energy effects, and the unusual nature of the rovibrational wave functions in these van der Waals molecules. The predicted spectra contain some new bands with surprisingly large intensities that might be detectable in experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458976
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  • 15
    Electronic Resource
    Electronic Resource
    Calculation of the electronic spectrum for Ar–OH (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3367-3378 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We calculate the rovibrational structure for the electronic transition of the Ar–OH complex between the ground and first excited electronic states, which correlate asymptotically with Ar(1S0)+OH(X 2Π) and Ar(1S0)+OH(A 2Σ+), respectively. An ab initio potential energy surface is used and the rovibrational states are calculated using a basis set method which couples the electronic spin and orbital angular momentum of the diatomic fragment with the overall rotations and vibrations of the complex. The calculated spectrum is compared with experimental results. In the low-frequency region the spectrum is found to be well ordered and assignment of spectroscopic features in terms of bending and stretching quantum numbers is possible. Close to dissociation, bend–stretch coupling leads to highly mixed states for which such assignments are no longer possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458817
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  • 16
    Electronic Resource
    Electronic Resource
    Rotationally and vibrationally inelastic scattering of glyoxal at E=80 meV (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 287-311 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results of quantum calculations on rotationally and vibrationally inelastic scattering of 1Au(S1) trans-glyoxal by H2,He, and Ar(E=80 meV) are presented. For scattering of 00 glyoxal and 72 glyoxal by H2, a quantitative comparison with a recent crossed beam experiment is made. The calculated cross sections for rotationally inelastic scattering are in good agreement with the experimental values, and the trend that σ(72, k=0→72, k') falls off faster with k' than σ(00, k=0→00, k') is reproduced. Our calculations do not reproduce the experimental finding that, for the initial 72 level, the cross sections for the Δv7=−1 and Δv7=+1 transitions are nearly identical. The calculations on 72 glyoxal + He and Ar show important differences with 72 glyoxal + H2 in the competition of rotational excitation with vibrational excitation. Model calculations also presented here yield some interesting trends in the k' dependence of the cross sections σ(00, k=0→x1, k') on the vibrational mode x excited.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459602
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  • 17
    Electronic Resource
    Electronic Resource
    Calculations on vibrational predissociation of Ar–OH (A 2Σ+) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 8149-8165 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An R-matrix algorithm is developed for executing vibrational predissociation calculations within the Golden Rule approximation. The algorithm is used to calculate vibrational predissociation linewidths and OH product rotational distributions for the quasibound states of Ar–OH (A2 Σ+, v=1). An ab initio potential energy surface obtained with the coupled electron pair approximation is used in the computations. The theoretical results are compared with experiment. The high anisotropy of the system is found to strongly favor vibrational to rotational energy transfer and the product OH (A2 Σ+ , v=0) molecules are produced in highly excited rotational states. Quasibound states associated with excited bending levels are predicted to dissociate more rapidly than those assigned to the ground bend. For metastable states with the same bending quantum number, linewidths are predicted to decrease with increase in the intermolecular stretching quantum number.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461295
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  • 18
    Electronic Resource
    Electronic Resource
    Rovibrational spectra of open-shell van der Waals complexes: Ar–OH(X 2Π) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 4149-4160 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The infrared spectrum of Ar(1S0)–OH(X 2Π) has been predicted using an ab initio potential-energy surface. We assume that the electronic spin and orbital angular momenta remain coupled to the rotational motion of the diatom in a van der Waals complex. The rovibrational energies and wave functions are calculated using a basis-set method involving expansion of the rovibrational wave function in terms of a product basis of optimized radial and angular wave functions. Unusual features are observed due to the nonzero electronic angular momentum of the diatom in the rovibrational levels. The effect of deuterium substitution on the predicted spectra has also been studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460648
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  • 19
    Electronic Resource
    Electronic Resource
    Application of hyperspherical coordinates to four-atom reactive scattering: H2+CN→H+HCN (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4178-4190 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop the use of Delves' hyperspherical coordinates to study the reactive scattering of four-atom systems within the collinear approximation. We present quantum mechanical calculations of reaction probabilities for the collinear exothermic reaction H2+CN →H+HCN. We use a potential energy surface which reproduces the essential characteristics of the reaction. The effect of freezing the CN bondlength to its equilibrium value during the reaction is also investigated and is found to be a good approximation. It is found that HCN product vibrational states with the C–H stretch excited are produced preferentially in the reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457776
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  • 20
    Electronic Resource
    Electronic Resource
    Prediction of the infrared spectrum for the neon–ethylene van der Waals complex (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1079-1091 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The van der Waals states of Ne–C2H4 up to J=10 are calculated with the ethylene molecule in both its ground and ν7 excited vibrational states. The method involves separation of the van der Waals bending motions from the stretching motions and ethylene vibrations. The infrared spectrum of the complex is predicted in the region of the ethylene ν7 vibrational mode, and the results are compared with the calculated spectrum of free ethylene. The effect of ignoring off-diagonal Coriolis terms (which mix together different K states) in the Ne–C2H4 Hamiltonian is investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457180
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