The excitation of He+ by electron impact

Abstract

The wave function of the e--He+ system is expanded as a sum of close-coupling states together with a number of short-range correlation terms. The scattering matrix is evaluated in the energy range between the n = 2 and n = 3 thresholds. The convergence of the expansion of the wave function is discussed and comparison is made with recent experiments for the 1s-2s excitation cross section.