The high energy scattering of photons and alpha particles by hydrogen atoms

Abstract

The major part of the thesis I concerned with the methods used to obtain approximate values of cross sections for rearrangement processes in which protons and alpha particles are scattered from hydrogen atoms. Some of the relevant experiments are briefly described in Chapter 1 and time dependant scattering theory used n Chapter 2 to derive an exact depression for the cross section. Born expansions of the transition amplitude are introduced and in Chapter 3 some OBK and Born approximation calculations are discussed. Distorted wave, impact parameter and second order methods are considered in Chapters 4, 5 and 6, numerical results being given where possible. A new integral equation for the transition amplitude. The impulse approximation forms the subject of Chapters 7 and 8. A new derivation, due to Coleman, is given and calculations for the process. H(^+) + H (1s) →H(2p, 3s or 3p) + H(^+), H(^+) + H (2s) → H (2p) + H(^+), and He(^++) + H(1s) →He(^+) (2p or 3s) +H(^+), are described. The results are compared with those obtained by other workers. They are used to calculate the polarization of Lyman-alpha radiation emitted by 2p hydrogen atoms formed by capture and to investigate the n(^-3) rule by which estimates of total cross sections are often obtained. The asymptotic form of the electron capture cross section as the velocity of the incident particle tends to infinity is discussed in Chapter 9. A brief survey is given of the forms predicted by the various theories described in previous chapters. The high energy form of the modified first Born approximation derived in Chapter 4 is then considered. It is found that, with the approximations made, it is the same as that of Drisko's Second Born approximation.