Relativistic (e, 2e) processes

Abstract

In this report we review the experimental and theoretical development in the study of relativistic (e, 2e) processes. In these (e, 2e) experiments one observes electron impact ionization processes where both the ejected and scattered electrons are detected in coincidence after angular and energy analysis. This allows a complete determination of the collision kinematics and hence provides a sensitive test of theoretical models. The goal of the investigations, reviewed here, is the basic understanding of the inner-shell ionization process by relativistic electrons up to the highest atomic numbers, probing the quantum mechanical Coulomb problem in the regime of high energies (up to 500 keV) and strong fields. (e, 2e) experiments with polarized electron beams represent an important step towards the ideal of a quantum mechanical complete analysis of the ionization process. In the calculation of the pertinent triply differential cross section we will show that only a fully relativistic theory where the strong distorting effects of the heavy atom are properly included in both the incident and final channels can approach a realistic description of the problem and that the simplest viable approximation is the relativistic distorted-wave Born approximation.