STURMIAN TREATMENT OF EXCITATION AND IONIZATION IN HIGH-ENERGY PROTON-HELIUM COLLISIONS

Cross sections have been calculated for excitation of the (2s2) 1S, 2 1S, and 2 1P states and ionization of helium by MeV -energy protons. The sensitivity to couplings among these excitation and ionization channels is studied using the Sturmian-pseudostate approach applied previously by Winter [Phys. Rev. A 35, 3799 (1987)] to one-electron systems. The inclusion of many states greatly lowers the 2s2 cross section and brings it closer to the recent experimental result of Giese et al. [Phys. Rev. A 42, 1231 (1990)].