A two-centre convergent close-coupling approach to positron–helium collisions

A two-centre convergent close-coupling method, which includes the positronium-formation channel, has been developed for positron scattering on helium. Convergent, pseudoresonance-free cross sections have been obtained. This is only possible if complete expansions are used on both the positronium and helium centres. The method is valid for all projectile energies and all transitions, including breakup, which is associated with excitation of positive-energy helium and positronium pseudostates. Generally, good agreement between calculated cross sections and available experimental data has been found across all incident energies.