Monte Carlo quasiclassical trajectory study of Br + HBr and H + HBr: Effect of reactant vibration and rotation on reaction rates and energy transfer

Abstract

A quasiclassical trajectory study of reactive and nonreactive processes in the H+HBr and Br+HBr systems is reported in which attention is focused on the role of initial internal energy on reaction rate coefficients and on angular scattering distributions and the contribution of atom‐exchange reactions to vibrational energy transfer. For both systems the atom‐exchange mechanism is a significant contributor to the vibrational relaxation of HBr. Initial internal excitation, either vibrational or rotational, leads to an increase in the reaction rate coefficient. In the Br+HBr case the atom‐exchange product molecule is scattered in the forward direction, the distribution is insensitive to initial internal energy changes, and the trajectories are complex. On the other hand, the H+HBr reactions, abstraction and atom exchange, both proceed in a direct, uncomplicated fashion and in the case of abstraction the H₂ product is scattered backward. Where possible the results are compared with other work, principally Cl+HCl.