Electron impact excitation of light atoms in assorted wave approximations

Abstract

This thesis is concerned with a study of inelastic electron-atom collisions with the incident energy ranging from just above the first ionization threshold to some energy where the First Born approximation becomes valid. The main physical effects which need to be included in the theoretical treatment of such collisions are electron exchange and distortion of both the atomic system and the wave describing the external electron. A method which takes account of these effects, to be referred to as the Distorted Wave Polarized Orbital (DWPO) approximation, is described. Three models based on this approximation are developed and applied to electron collisions with the light atoms hydrogen and helium. In particular the models are applied to the following collision processes: e + H(ls) → e + H(2s, 2p, 2s + 2p); e + He(1

1S) → e+ He(n

1,3L), n = 2,3,4,5, L= S,P. Results are presented for the total (integral)and differential cross sections and also, where appropriate, for the parameters describing the orientation and alignment properties of the excited atom. The results are compared with those of other theoretical methods and with experimental measurements.