The object of this study is to examine fundamental interactions of electrons and positrons with atoms. Special attention is given to spin dependent effects, coherence and correlation phenomena. The project consists of two related parts; first, the reduced density matrix formalism is used to provide a systematic description of collision processes in terms of a few well defined, measurable parameters, and second, numerical calculations based on perturbative (Distorted Wave) and non- purturbative (R-matrix) techniques are used to predict these parameters.
