Non-equilibrium kinetics of bimolecular reactions. Part 7: The puzzle of the H+O2 reaction

Abstract

The steady state master equation is solved to determine the population distribution of vibrationally excited O₂ while reacting with H atoms at temperatures ranging from 300 K to 8000 K. State-selected reactive rate constants are used which are consistent with the known theoretical and experimental rates of the H+O₂ reaction at all levels of detail. Known V–T energy transfer rate constants are also used. Calculations are performed for a variety of H, O₂ and Ar compositions, revealing the conditions where non-equilibrium effects can play a role. The results of the calculation show that the thermal rate coefficient at 2000 K is less than the value expected, by as much as 25%. This is due to a much distorted vibrational population distribution caused by the reaction itself. Although the predicted behaviour of the rate coefficient qualitatively mimics the experimental one, it does not quantitatively explain the observed experimental discrepancies, which have puzzled kineticists and dynamicists for the past 20 years.