Interactions of electrons with matter

Abstract

[eng] The interaction of electrons with matter has been a subject of intense work since the beginning of the century. Although we know that the interaction is purely electromagnetic, its theoretical description is complicated by two different reasons. On the one hand, the number of particles that participate in the interaction may be very large. Even when the target is a single hydrogen atom, the collision is a three body problem for which only approximate solutions of the wave equation are known. Therefore, the interaction can only be treated by using approximate many-body methods. In particular, scattering of fast electrons by single atoms can be reasonably well understood on the basis of independent particle models. On the other hand, when the medium where the projectile moves extends over a. large volume, the projectile may interact repeatedly with the medium. The proper tools to deal with problems involving electron penetration in matter are multiple scattering theories and/or Monte Carlo simulation. The aim of this thesis is to provide a consistent basis for the development of Monte Carlo simulation algorithms which are more accurate than the ones presently available. In fact, a high-energy simulation code based on relevant parts of this thesis is already operable; and a program to simulate electron transport at intermediate and low energies (below about 100 keV) is currently being developed from the theory presented in this work. The reliability of the simulation results obtained with these codes will offer the ultimate demonstration of the correctness and effectiveness of the approaches described here. The thesis is structured in four chapters. Chapter 1 is devoted to the evaluation of reliable single elastic scattering cross sections for high energies. Multiple elastic scattering is considered in detail in chapter 2. Chapter 3 is devoted o the inelastic scattering of low-energy electrons in solids. In chapter4 we consider the energy loss of high-energy electrons and positrons in matter.