Introduction

Abstract

The theory of atomic collisions was given a fresh incentive towards the end of the nineteen twenties, immediately after the advent of quantum mechanics. The first edition of the celebrated book by Mott and Massey, The Theory of Atomic Collisions appeared in 1933 [1.1]. Since then, the theory has greatly advanced. Yet the only part which is relatively complete (at least in principle) seems to be that dealing with slow collisions in which the velocity of the atoms is substantially smaller than the velocity of the electrons in the atoms. This condition makes it possible to formulate the collision problem correctly, and since the scattering equations are well known, the solution of such a problem with a computer would cause no great difficulty. However, a solely numerical solution of any problem leaves a certain discontent, since the mechanism of the process studied remains obscure. Therefore, it appears to be desirable to obtain more analytical results although this is possible only under additional drastic simplifications.