Abstract
Differences between the recent pseudostate calculations of Callaway (1985), Bransden et al. (1985) and van Wyngaarden and Walters (1985) of the total 1s to 2p and 1s to 2s cross sections at 54.4 eV are explained; it is shown that the cross sections of van Wyngaarden and Walters are probably the most reliable. The importance of d-state couplings is highlighted. A tabulation of the 2p cross section by Callaway in the energy range 12.2-54.4 eV is revised and an analytic fit to the 2p cross section above 12.2 eV is given. It is shown that the revised tabulation and the cross sections of van Wyngaarden and Walters at 100 and 200 eV are in quite good agreement with the relative experimental measurements of Long et al. (1968) at energies between 13.4 and 200 eV. In contrast, the absolute measurement of the 2p cross section by Williams (1981) at 54.4 eV is in disagreement with theory.