A semiclassical study of the photodissociation dynamics of a coupled two-surface model of HCl+ by an intense laser field in the long-wavelength limit

The photodissociation of HCl+ on two coupled potential surfaces is studied in the long wavelength regime with a semiclassical method employing classical trajectories and a hopping algorithm. Dissociation probabilities, product kinetic energy distributions, and branching ratios are presented. In addition, two mechanisms are introduced to explain trends in these properties. One mechanism produces large product kinetic energies and is an extension to two-coupled surfaces of the "wagging tail" mechanism seen in a previous one-surface study [M. Thachuk and D. M. Wardlaw, J. Chem. Phys. 102, 7462 (1995)]. The other mechanism is an extended barrier-suppression mechanism and accounts for the bulk of the product kinetic energy distribution, and in particular rationalizes the low energy part of these distributions as well as the branching ratios. It is shown that most of the trajectories undergo at most one nontrivial hop before dissociating so that the dynamics is dominated by the motion near the barrier to dissociation. This provides a simple, intuitive model for understanding the overall dynamics. (C) 2000 American Institute of Physics. [S0021-9606(00)00130-6].