Dynamical bottleneck in the reaction H+O2→OH+O at high collision energies

Abstract

The nascent rotational and λ-doublet state distributions of OH produced in the reaction H+O2→OH(N,v,f )+O were probed by fast atom–laser induced fluorescence experiments at average collision energies E=100, 183, 200, 220, and 243 kJ/mol. With increasing E, the rotational product distributions become increasingly nonstatistical with a narrow peak at high rotational states, in good agreement with quasiclassical trajectory calculations on an ab initio potential energy surface. The calculations show the narrow product rotational peak to be due to an increasing specifity of the initial H–O2 configurations leading to reactions. At high E the impact parameters and initial polar angles are confined to a rather small range allowing reaction only for an optimal approach. The OH λ-doublet distributions show preference for the Π(A′) component probed by R lines at all collision energies investigated. This suggests a planar reaction path and little importance of out of plane rotation of the HO2 complex at the high collision energies of the experiment. The experimental λ-doublet distributions are quantitatively compared with the degree of in-plane scattering obtained from the trajectory calculations.