STRUCTURES IN TRIPLY AND DOUBLY DIFFERENTIAL IONIZATION CROSS-SECTIONS OF ATOMIC-HYDROGEN

This work investigates theoretically triply and doubly differential cross sections for electron- and positron-impact ionization of atomic hydrogen. On the basis of the framework developed by Brauner et al, structures in the triply differential cross section are identified and their contributions to the doubly differential cross section are discussed. A novel structure in the triply differential cross section in the case of positron impact has been found. Results for the energy and angular distributions of secondary electrons are presented and compared with available experimental data. In general, our results are in good agreement with the experiment. However, discrepancies between experiment and our theory exist for electrons ejected into the forward direction. It turns out that at low impact energy the angular and energy spectrum of the secondary electrons is strongly influenced by all three two-body interactions involved in the process. In the case of electron impact also exchange effects contribute to the shape and magnitude of the cross section. In summary we conclude that triply and doubly differential ionization cross sections depend sensitively on the description of the three-body system.