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Exact and Approximate Quantum Mechanical Reaction Probabilities and Rate Constants for the Collinear H + H2 Reaction

Truhlar, Donald G. and Kuppermann, Aron (1972) Exact and Approximate Quantum Mechanical Reaction Probabilities and Rate Constants for the Collinear H + H2 Reaction. Journal of Chemical Physics, 56 (5). pp. 2232-2252. ISSN 0021-9606. doi:10.1063/1.1677525.

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We present numerical quantum mechanical scattering calculations for the collinear H+H2 reaction on a realistic potential energy surface with an 0.424 eV (9.8 kcal) potential energy barrier. The reaction probabilities and rate constants are believed to be accurate to within 2% or better. The calculations are used to test the approximate theories of chemical dynamics. The reaction probabilities for ground vibrational state reagents agree well with the vibrationally adiabatic theory for energies below the lowest threshold for vibrational excitation, except when the reaction probability is less than about 0.1. For these low reaction probabilities no simple one-mathematical dimensional theory gives accurate results. These low reaction probabilities occur at low energy and are important for thermal reactions at low temperatures. Thus, transition state theory is very inaccurate at these low temperatures. However, it is accurate within 40% in the higher temperature range 450–1250°K. The reaction probabilities for hot atom collisions of ground vibrational state reagents with translational energies in the range 0.58 to 0.95 eV agree qualitatively with the predictions of the statistical phase space theory. For vibrationally excited reagents the vibrational adiabatic theory is not accurate as for ground vibrational state reagents. The lowest translational energy of vibrationally excited reagents above which statistical behavior manifests itself is less than 1.0 eV.

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Additional Information:©1972 The American Institute of Physics. Received 13 September 1971. The authors are grateful to Dr. Dennis J. Diestler, Dr. Nicholas W. Winter, Dr. Merle E. Riley, and Dr. L.M. Delves for valuable discussions or correspondence concerning the method used to solve the Schrödinger equation. We are grateful to Dr. John T. Adams, Joel M. Bowman, and Baruch Kuppermann for performing some of the computer calculations. We would also like to thank Dr. Winter, Dr. Christopher A. Parr, F.P. Roullard III, and the Caltech Booth Computing Center consulting staff (under the direction of Kiku Matsumoto) for help with difficulties involved in the calculations reported here and elsewhere and for useful computer subprograms. We are grateful to Professor William H. Miller for discussions of the results. The work reported here was finished and this article was written while one of the authors (D.G.T.) was in the Department of Chemistry of the University of Minnesota. We are grateful to the University of Minnesota Computing Center for a computing time subsidy. Supported in part by the United States Atomic Energy Commission, Report Code CALT-767-P4-84. Arthur Amos Noyes Laboratory of Chemical Physics, Contribution No. 4334.
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University of MinnesotaUNSPECIFIED
Atomic Energy CommissionCALT-767P4-84
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Arthur Amos Noyes Laboratory of Chemical Physics4334
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ID Code:11749
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Deposited On:22 Sep 2008 23:34
Last Modified:08 Nov 2021 22:02

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