Quantum-mechanical study of H + H2 reactive scattering

Abstract

The results of an approximate quantum-mechanical treatment of the H + H2 reaction are reported. Two limiting models in the distorted wave formulation (DWB) are compared; in one, the molecule is unperturbed by the incoming atom and in the other the molecule adiabatically follows the incoming atom. For thermal incident energies and the semi-empirical interaction potential employed previously for a quasi-classical trajectory analysis of the reaction, the adiabatic model seems to be more appropriate. To examine the total and differential cross section for a range of energies, a simplified (linear) version of the DWB method is used. Most of the results are similar to those obtained quasi-classically. However, the quantum total cross section has a significantly higher threshold than does the classical cross section. In agreement with the quasi-classical treatment, the differential cross section is strongly backward peaked at low energies and shifts in the forward direction as the energy increases. The calculated variation of the total cross section with final rotational state raises questions concerning the standard procedure for determining para-H2 to ortho-H2 conversion rate constants.