Abstract
A coupled pseudostate approximation for calculated triple differential cross sections for electron ionisation of atomic hydrogen is presented. A partial wave formalism is developed for ionisation from any initial s state. The approximation is best suited to asymmetric geometries where one of the two electrons in the final ionised state has a much smaller energy than the other. Results are presented for ionisation of H(1s) at incident energies of 54.4, 100, 150 and 250 eV and ejected energies of 5, 10 and 14 eV. At 150 and 250 eV comparison is made with the coplanar experimental data of Ehrhardt et al. (1985), Schlemmer and Lohmann et al. (1984) with a generally satisfactory outcome, although there are some discrepancies. The coupled pseudostate approximation substantially confirms the earlier second Born/eikonal-Born series calculations of Byron et al. (1985) for high energy asymmetric coplanar geometries.