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On the theory of the CO+OH reaction, including H and C kinetic isotope effects

Chen, Wei-Chen and Marcus, R. A. (2005) On the theory of the CO+OH reaction, including H and C kinetic isotope effects. Journal of Chemical Physics, 123 (9). Art. No. 094307. ISSN 0021-9606. doi:10.1063/1.2031208.

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The effect of pressure, temperature, H/D isotopes, and C isotopes on the kinetics of the OH+CO reaction are investigated using Rice-Ramsperger-Kassel-Marcus theory. Pressure effects are treated with a step-ladder plus steady-state model and tunneling effects are included. New features include a treatment of the C isotope effect and a proposed nonstatistical effect in the reaction. The latter was prompted by existing kinetic results and molecular-beam data of Simons and co-workers [J. Phys. Chem. A 102, 9559 (1998); J. Chem. Phys. 112, 4557 (2000); 113, 3173 (2000)] on incomplete intramolecular energy transfer to the highest vibrational frequency mode in HOCO*. In treating the many kinetic properties two small customary vertical adjustments of the barriers of the two transition states were made. The resulting calculations show reasonable agreement with the experimental data on (1) the pressure and temperature dependence of the H/D effect, (2) the pressure-dependent 12C/13C isotope effect, (3) the strong non-Arrhenius behavior observed at low temperatures, (4) the high-temperature data, and (5) the pressure dependence of rate constants in various bath gases. The kinetic carbon isotopic effect is usually less than 10 per mil. A striking consequence of the nonstatistical assumption is the removal of a major discrepancy in a plot of the kOH+CO/kOD+CO ratio versus pressure. A prediction is made for the temperature dependence of the OD+CO reaction in the low-pressure limit at low temperatures.

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Marcus, R. A.0000-0001-6547-1469
Additional Information:©2005 American Institute of Physics (Received 1 February 2005; accepted 15 July 2005; published online 8 September 2005) It is a pleasure to acknowledge the support of this research by the National Science Foundation. We also thank Dr. Muckerman for providing the F matrix for the structures in their paper,18 which were used to check the accuracy of rate constant calculation with our previous vibrational frequencies.
Subject Keywords:carbon compounds; oxygen compounds; molecule-molecule reactions; reaction kinetics theory; isotope effects; tunnelling; intramolecular mechanics; reaction rate constants; vibrational states
Issue or Number:9
Record Number:CaltechAUTHORS:CHEjcp05
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1919
Deposited By: Archive Administrator
Deposited On:23 Feb 2006
Last Modified:08 Nov 2021 19:43

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