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

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.