The multiple-collision region in non-reactive atom-diatom collisions

Abstract

We investigate the complex region, consisting of complex (multiple-collision) trajectories, arising in the non-reactive vibrational excitation of a classical collinear atom-diatom system. The excitation pattern for the diatom (the final state as a function of the initial conditions) is seen to have a well-defined, though complicated, piecewise continuous structure, and we show that this structure has a clear physical interpretation. Groups of complex trajectories with similar properties are found, and the outcome of collisions with zero initial relative velocity is seen to be related to the type of excitation pattern in the complex region. The numerical instability of complex trajectories and interference effects (in semi-classical theory) are also discussed.