Quantum study of the redistribution of flux during inelastic collisions

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Abstract
A new method is presented for the study of the mechanism of inelastic atomic and molecular collisions. This involves the determination of the current density associated with, separately, the incoming and outgoing scattering wave functions in either an asymptotic (diabatic) or locally adiabatic basis. This yields a picture of how the incoming flux, initially associated with a given internal state, redistributes itself as a function of the interparticle separation both as the particles approach, and, subsequently, as the particles recede. It is shown that the separation into incoming and outgoing flux, which is valid asymptotically, continues to be valid as the collision partners approach, without mixing of the contributions from the incoming and outgoing waves. A simple extension of our linear-reference-potential, log-derivative propagation technique can be used to compute the redistribution of the initial flux. It is argued that analysis in a fully adiabatic basis, which corresponds to the local eigenvectors of the collision system, provides the most meaningful physical insight. A simple stabilization correction can be introduced, which prevents adiabatically closed channels from numerically contaminating the determination of flux redistribution among the locally open channels. Application is made to a pedagogical two-state problem, to a multistate collision system involving four different electronic potential curves, and to a second multistate collision system involving a closed-channel resonance.