Collision dynamics and the thermal rate coefficient for the reaction H+O2→OH+O

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Abstract
Classical trajectory methods have been used to predict the rate of the reaction H+O2→OH+O. Both quasiclassical (QCT) and quasiclassical quantum mechanical threshold (QCT–QMT) methods were employed in the analysis. The QCT–QMT calculations are in excellent agreement with experimental results over the entire temperature range considered (250<T<2500 K). In particular, the modified Arrhenius expression from the QCT–QMT analysis k = 5.13×1016 T−0.816 exp(−16 507/RT) cm3/mol is in excellent agreement with Schott’s high temperature shock tube result k = 1.22×1017 T−0.907 exp(−16 620/RT) cm3/mol and is less than a factor of 2 too high compared with experimental results in the 250–300 K temperature regime. The negative Arrhenius curvature is found to be due to a dynamic effect associated with the L+HH mass combination of the reactants. Simple formulations of statistical models for the reaction (transition-state theory, the statisitical model for complex reactions, and the unified statistical model) are found to given incorrect dependence of the reaction cross section on relative translational energy. This incorrect dependence of σR on ET leads to positive Arrhenius curvature rather than the negative curvature obtained both experimentally and from the trajectory calculations.