Collision of an Atom and a Diatomic. The Distorted Wave Expansion

Abstract

Higher‐order terms are considered in Mott and Jackson's distorted wave treatment of the atom‐diatomic collision problem. In addition to the physically realistic requirement of a soft interaction, it is shown that the expansion is best for light incident atom with low kinetic energy. It is also shown that for an n‐quantum transition, it is necessary to go to at least the nth order in the expansion in order to obtain a reasonably accurate result. A simple second‐order formula is given for two‐quantum transitions. Numerical evaluation of the second‐ and third‐order terms has been carried out for a number of transitions and the results compared with Secrest and Johnson's exact values. A rearrangement of the distorted wave expansion for one‐quantum transitions which leads to a wider range of applicability is presented.