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

This work investigates theoretically triply and doubly differential cr oss sections for electron- and positron-impact ionization of atomic hy drogen. On the basis of the framework developed by Brauner et al, stru ctures in the triply differential cross section are identified and the ir contributions to the doubly differential cross section are discusse d. A novel structure in the triply differential cross section in the c ase of positron impact has been found. Results for the energy and angu lar distributions of secondary electrons are presented and compared wi th available experimental data. In general, our results are in good ag reement 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 spectr um of the secondary electrons is strongly influenced by all three two- body interactions involved in the process. In the case of electron imp act also exchange effects contribute to the shape and magnitude of the cross section. In summary we conclude that triply and doubly differen tial ionization cross sections depend sensitively on the description o f the three-body system.