Adiabatic switching factors in slow atomic collisions

Abstract

Adiabatic switching factors are introduced into the molecular model of atomic collisions. These factors are so designed as to modify the perturbed stationary-state equations only in the asymptotic region, where an analytic WKB-type solution can be found. This solution can be used to impose the correct boundary conditions at any arbitrarily large (but finite) internuclear distance. The scattering amplitudes are then uniquely defined and are readily obtained by a simple matrix transformation, once the solutions of the standard perturbed stationary state equations are known. The problem of spurious long-range couplings and of possible divergences in the cross-section calculations are thereby avoided. An application to a typical ion-atom collision such as H⁺/Li, where no meaningful result can be obtained without the introduction of translation factors, illustrates the feasibility of the approach.