MULTITRAJECTORY SEMICLASSICAL METHOD FOR THE TREATMENT OF NONADIABATIC ATOM-MOLECULE COLLISIONS

The problem of the choice of a trajectory in the time-dependent semiclassical treatment of nonadiabatic molecular collisions is reconsidered. The purpose of the work is to improve the semiclassical description of vibronic transitions in conditions where quantal calculations are hardly feasible. In order to bring out our proposal, the investigation is carried out in the framework of the infinite-order sudden approximation where quantal calculations are tractable and thereby provide a reliable testing ground. The way in which a classical trajectory emerges when deriving the time-dependent equations from the quantal ones is reexamined. Specific features are pinpointed which draw one's attention to the idea of a multitrajectory approach. A proposal is formulated and applied to vibronic charge transfer in the H+ + O2 collision. The proposed multitrajectory treatment is found to be superior to the other semiclassical treatments based on a simple common trajectory.