ELECTRON INDUCED ELASTIC AND INELASTIC PROCESSES OF ATOMIC SYSTEMS

Abstract

The study of electron-atom scattering has been one of the subjects that received considerable attention of both the theorists and experimentalists. It is still active area of research of increasing interest in the field of atomic and molecular collision physics. The specific interest in such a subject has been due to its fundamental importance and numerous applications in various fields e.g. plasma physics, astrophysics, laser physics etc. The processes, which may result due to electron impact on atomic systems can be broadly put into two categories viz. elastic and inelastic processes. We consider and discuss here the elastic and two important inelastic processes i.e. electron impact (i) excitation and (ii) single ionization (e, 2e) of atomic systems. The recent progress in the field of electron-atom scattering can be attributed to the advances in the quality of experimental technology with the help of which it has become possible to perform sophisticated atomic physics experiments. Now one can prepare the pure states of the colliding projectile and target partners and can study their interaction. The advantage of such experiments is to improve and develop powerful theoretical models on the basis of their ability to explain the experimental data. The introduction of electron-photon-coincidence technique it has been possible to get full information about the dynamics of an electron-atom excitation/ ionization process which was not possible to gain through the traditional total cross section measurements. Also the experiments involving super-elastic scattering of electrons from the laser excited atoms can provide equally valuable similar information. With such experiments, alignment and orientation of the excited atom after electron excitation process can be easily determined and angular correlations of the outgoing electrons in the (e, 2e) process can be studied. The pres'ent thesis deals with the theoretical work in the light of some such recent experiments. Most of the earlier studies on electron impact excitation of atoms have focused on the lighter atoms like hydrogen, helium etc. but recent experimental activity has shown interests in the relatively heavier atoms. While lighter atoms could be described in LS-coupling scheme for relatively heavier atoms departures from LS-coupling scheme sometimes become important during the scattering process and relativistic effects through spin-orbit and (or) exchange interactions may play role. The work in the thesis explores this aspect and theoretically investigates the importance of relativistic effects in the study of electron impact excitation of atom.