STUDY OF ATOMIC COLLISIONS IN GLAUBER APPROXIMATION

Abstract

The work reported in this thesis is author=s attempt to study the collision processes,at high and intermediate ener-gieslin which a beam of charged particles (e.g. electrons) is bombarded onto an atomic or ionic target. Throughout this work, the eikonal or the Glauber approximation (the latter is an special case of the former) has been the main tool of investigation. In the first chapter, various quantal, classical and semi-classical approaches for the study of these collision processes have been briefly reviewed. The eikonal multiple scattering expansion and its relationship with the Born series have also been discussed. The second chapter is devoted to the details of the Glauber approximation. This chapter basically describes (i) the underlying assumptions and the expected range of validity of the approximation and (ii) its alternative forms for the scattering wavefunction and amplitude. In the third chapter, a method for the Glauber predicted scattering amplitudes in a one-dimensional integral form for e-H(ls) scattering has been proposed to study the excitation of atomic hydrogen to highly excited states from a low lying state. Earlier expressions C.K. Thomas and E. Gerjuoy, J.Maths. Phys. 12, 1567(1971).1 were a bit cumbersome due to the appearance of an increasing number of hypergeometric functions depending on the principal quantum number cf the excited state. In the fourth chapter the Glauber approximation -iv- has been applied to the study of elastic and inelastic scattering of electrons by lithium atom by explicitly treating all the three electrons by suitably adapting Francois procedure [Phys. Rev. Lett. 26, 1088(1971)]. The percentage polarization of the resulting resonance line (2p 2s) emitted from °Li and 7Li following electron excitation has also been obtained. The fifth chapter is devoted to the study of elastic scattering of electrons by helium like ions (such as Er and Li+ ) using the optical model approach in eikonal approximation. In the sixth chapter an attempt has been made in a very simple way to improve upon the Glauber (straight-line) approximation at large scattering angles. It has been used to study e-H(ls) elastic scattering and the results have been compared with other approaches and the recent experimental data. The seventh chapter summarizes the work reported in earlier chapters and contains some comments, pointing out the drawbacks and the suggestions for their elimination.