Quantum dynamics of the H+O(2)-->O+OH reaction.

Quantum scattering calculations of the H+O(2)-->O+OH reaction are presented using two different representations of the electronically adiabatic potential energy surface of the HO(2) system. The calculations have been performed using a three-dimensional time-independent quantum reactive scattering program based on hyperspherical coordinates. The effect of vibrational and rotational excitations of the O(2) molecule on the reactivity is investigated by carrying out calculations for vibrational quantum numbers v=0-8 and rotational quantum numbers j=1-9 for both potential surfaces. While the energy threshold for the reaction is lowered with increase in vibrational or rotational excitation of the molecule the overall energy dependence of the reaction probability remained largely unaffected with rovibrational excitations. Vibrational excitation was found to wash out resonances in the reaction probabilities. The sensitivity of the rate coefficients to the initial vibrational level of the O(2) molecule is investigated and it is found that the rate coefficient is a strong function of the vibrational quantum number of the O(2) molecule. The effect is more pronounced at low temperatures with the rate coefficient at 400 K increasing by about eight orders of magnitude when the vibrational level of O(2) is increased from 0 to 6. Thermal rate coefficients of the reaction calculated using cumulative reaction probabilities within a J-shifting approximation have been found to be in reasonable agreement with experimental results. Results show that vibrational excitation of the O(2) molecule needs to be considered in evaluating thermal rate coefficients of the reaction.