Ionization of hydrogen, helium, lithium and beryllium by electron and proton impact

Abstract

Cross sections for the ionization of H, He, Li and Be in their ground states by electron and proton impact are calculated using Born's approximation. In each case partial wave cross sections are calculated by expanding in terms of the angular momenta of the ejected electron. Hartree-Fock wave functions are used for all the initial and final bound states of the non-hydrogenic atoms, together with an undistorted Coulomb function for the ejected electron. The relative contributions to the total cross sections from each partial wave are studied in detail, and for hydrogen and helium about two-thirds of the total arises from the partial wave cross section l = 1. In the cases where a transition from a 2s state is involved the allowed part is less important, and it is necessary to consider separately contributions to the total from all partial waves up to l = 5. In the cases where there are other theoretical calculations or experimental measurements available agreement is good in the regions of validity of the first Born approximation.