J = 0 reactivity and cross-section in the H + O 2 reaction: is there a pronounced maximum as a function of energy?

Abstract

Trajectory calculations of the total reactivity for the H + O 2 reaction, out of the vibrational-rotational states ( v, j) = (0, 1) and (3, 1), with the total angular momentum kept at J = 0, are shown to agree well with quantum mechanical reactivities calculated on the same (DMBE IV) potential energy surface. Trajectory calculations of the total reactive cross-sections are also reported. A simple hybrid model (QCT/QM-UJ) to calculate the total cross-section from the (0, 1) quantum mechanical reactivity, using the assumption of a uniform- J distribution in which the cut-off value of the total angular momentum is obtained quasiclassically, is also suggested and tested. Agreement with recent cross-section measurements is reasonable but, unlike experiment, no sharp maximum is observed on the reaction cross-section as a function of translational energy, leaving its origin unexplained.