Calculations using second order perturbation theory are made of the probability at or near threshold of ionization or excitation of K electrons accompanying beta decay, in order to compare the effectiveness of the shaking and collision mechanisms. The two mechanisms are found to be about equally important. In the case of positron decay interference between the two modes greatly reduces the transition probability. An earlier calculation, that of Feinberg , using first order perturbation theory with a static interaction between the beta particle and the atomic electron, led to the result that the collision effect is negligible compared to the shaking effect at or near threshold, in disagreement with the result of this thesis. Feinberg's approach is shown to be invalid.

Sharp, R. (Supervisor)