Electron transfer and ionization in proton-helium collisions studied using a Sturmian basis

Abstract

Cross sections have been calculated for electron transfer into all states of hydrogen and for ionization in collisions between protons and helium atoms at proton energies from 50 to 200 keV. Cross sections for electron transfer into individual states up to 3${\mathit{d}}_2$, as well as the z component of the average electric dipole moment and of the cross product between the angular momentum and the Runge-Lenz vector for the n=2 and 3 levels, have also been determined. A coupled-state approach is taken using bases of about 50 Sturmian functions, extending earlier work on one-electron systems. The full two-electron interaction is included, neglecting, however, interatomic exchange. Detailed tests of convergence with respect to the size of basis have been carried out. It is found that the results for capture into all states and the individual states 1s, 2s, and 3s, as well as the results for ionization, are converged to at least about 10%. There is excellent agreement with experimental results at least at the highest energy, where interatomic exchange is unimportant. Quantities involving p and d levels, on the other hand, are much more sensitive to the size of basis, and the agreement of the present and other coupled-state results with experimental results is less satisfactory.