Temperature and pressure dependence of the reaction of OH and CO: Master equation modeling on a high-level potential energy surface

The temperature and pressure dependence of the reaction of OH+CO has been modeled using the (energy-resolved) master equation and RRKM theory. These calculations are based on the coupled-cluster potential energy surface of Yu and co-workers (Chem Phys Lett 349, 547-554, 2001). As is well known, this reaction shows a strong non-Arrhenius behavior at moderate and low temperatures because of the stabilization of the HOCO intermediate. Kinetic simulations are in excellent agreement with experiments at temperatures above 300 K, but the agreement is only modest at temperatures below 250 K. Our calculations indicate that the contribution of tunneling to the rate constant is marginal, given the small energy difference between the transition states corresponding to formation and decomposition of the HOCO intermediate. Parametric fits to the calculated rate constants are provided for modeling purposes. (C) 2003 Wiley Periodicals, Inc.