Convergent close-coupling calculations of positron–helium scattering at intermediate to high energies

The single-centred convergent close-coupling method has been applied to positron–helium scattering at energies from the first ionization threshold to 1 keV for calculating one-electron excitation and ionization processes. Total scattering, positronium formation plus single ionization (unresolved), and target excitation cross sections have been calculated. It is found that the often-used frozen-core approximation for the target structure leads to a small but systematic overestimation of the cross sections. Generally, the agreement between the present and most recent calculations, as well as experiment, is satisfactory.