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An approximate theory of the ozone isotopic effects: Rate constant ratios and pressure dependence

Gao, Yi Qin and Marcus, R. A. (2007) An approximate theory of the ozone isotopic effects: Rate constant ratios and pressure dependence. Journal of Chemical Physics, 127 (24). Art. No. 244316. ISSN 0021-9606. doi:10.1063/1.2806189.

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The isotopic effects in ozone recombination reactions at low pressures are studied using an approximate theory which yields simple analytic expressions for the individual rate constant ratios, observed under “unscrambled” conditions. It is shown that the rate constant ratio between the two competing channels XYZ-->X+YZ and XYZ-->XY+Z is mainly determined by the difference of the zero-point energies of diatomic molecules YZ and XY and by the efficiency of the deactivation of the newly formed excited ozone molecules, whereas the mass-independent fractionation depends on a “nonstatistical” symmetry factor eta and the collisional deactivation efficiency. Formulas for the pressure effects on the enrichment and on the rate constant ratios are obtained, and the calculated results are compared with experiments and more exact calculations. In all cases, ratios of isotope rates and the pressure dependence of enrichments, the agreement is good. While the initial focus was on isotope effects in the formation of O3, predictions are made for isotope effects on ratios of rate constants in other reactions such as O+CO-->CO2, O+NO-->NO2, and O+SO-->SO2.

Item Type:Article
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Marcus, R. A.0000-0001-6547-1469
Additional Information:©2007 American Institute of Physics. Received 12 July 2007; accepted 15 October 2007; published 28 December 2007. It is a pleasure to acknowledge the support of this research by the Dreyfus Foundation (Y.Q.G.) and the National Science Foundation (R.A.M.). Y.Q.G is a 2006 Searle Scholar.
Subject Keywords:atom-molecule reactions, isotope effects, ozone, reaction kinetics theory, reaction rate constants
Issue or Number:24
Record Number:CaltechAUTHORS:GAOjcp07
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9426
Deposited By: Archive Administrator
Deposited On:30 Dec 2007
Last Modified:08 Nov 2021 20:59

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