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Dissociation and isomerization of vibrationally excited species. II. Unimolecular reaction rate theory and its application

Wieder, Grace M. and Marcus, R. A. (1962) Dissociation and isomerization of vibrationally excited species. II. Unimolecular reaction rate theory and its application. Journal of Chemical Physics, 37 (8). pp. 1835-1852. ISSN 0021-9606. doi:10.1063/1.1733376.

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Data on quasi-unimolecular reactions have usually been compared with theoretical equations based on classical treatments, because the expressions are simpler than those obtained on the basis of a quantum model. The quantum reformulation of the RRK theory in Part I is used to compute the pressure dependence of the rate constants and the limiting low-pressure rates for a variety of unimolecular reactions without employing adjustable parameters. An asymptotic expansion of the integral for the limiting low-pressure second-order rate constant provides a very simple expression for this quantity.The errors inherent in corresponding classical calculations are estimated by comparing these results with those obtained from the theory in its classical limit. The error is temperature dependent and at low pressures increases from a factor of about three (under typical experimental conditions) for small reactants such as O3 and N2O to 105 or more for large molecules such as cyclopropane, C2H6, and N2O5. In most cases the rates calculated from the quantum form are in reasonable agreement with those obtained experimentally when all of the reactant oscillators are assumed effective in intramolecular energy transfer.

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Marcus, R. A.0000-0001-6547-1469
Additional Information:© 1962 American Institute of Physics. Received May 31, 1962. The authors would like to express their appreciation to Dr. B.S. Rabinovitch for his most helpful comments. Abstracted in part from the doctoral dissertation of Grace M. Wiedler, Polytechnic Institute of Brooklyn, June 1961. Presented in part at the American Chemical Society Meeting, New York, September 1960. Part I of the present paper appeared under a somewhat different title in J. Chem. Phys. 20, 359 (1952). The investigation reported herein was supported in part by the U.S. Atomic Energy Commission. [R.A.M. was an] Alfred P. Sloan Fellow.
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Atomic Energy CommissionUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Issue or Number:8
Record Number:CaltechAUTHORS:WIEjcp62
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ID Code:12235
Deposited By: Tony Diaz
Deposited On:13 Nov 2008 03:38
Last Modified:08 Nov 2021 22:26

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