Electron loss and excitation in atom-atom collisions

In this thesis we consider processes involving collisions of atomic Hydrogen, or a positive ion, with noble gas targets in which the projectile is excited to a discrete state or ionized. Theoretical methods based upon the first Born approximation, the impulse approximation and the pseudostate close-coupling approximation have been used. For sound theoretical reasons it is useful to distinguish between collisions in which the target remains in its ground state, (singly inelastic collisions), from those in which it is excited or ionized (doubly inelastic collisions). Particular attention has been paid to the problem of summing over all final states of the target. One form of the impulse approximation that is used in this thesis requires a knowledge of differential elastic electron-target scattering. To provide this information for noble gas targets a data base of 'best estimates' has been constructed from results published in literature. Also a computer program to calculate elastic electron-noble gas scattering in the static-exchange approximation has been devised. The theoretical basis for this program, which uses the R-matrix method, has been discussed in detail. Applications have been made to the phenomenom of electron loss to the continuum, the theoretical predictions being compared with experimental data for collisions of atomic Hydrogen and positive ions of Carbon, Oxygen and Silicon with gaseous targets of Helium and Argon. Direct excitation of H(1s) to the n = 2 and n = 3 levels in collisions with Helium, Neon, Argon, Krypton and Xenon targets has also been extensively studied. (author)