Positron-hydrogen collisions at low energies

The Harris-Nesbet algebraic method was used to carry out a large coupled-state calculation of e⁺ -H scattering at energies below the first excitation threshold of hydrogen. The six-state (1s,2s,2p H--1s,2s,2p Ps) coupling scheme was extended to include an adequate number of short-ranged functions of both hydrogenic and positroniumic types and the H 3p-bar pseudostate. Phase shifts and cross sections of partial waves from L=0 to 6 were obtained for e⁺ -H (1s) scattering as well as for Ps(1s)-p scattering. Our results are to be compared with those obtained by other research groups with some large-scale calculations employing, however, different numerical methods of approach. Our results agree excellently with the values calculated with a variational method by Bhatia et al. and by Humberston and co-workers and with the 21-state close-coupling approximation by Mitroy and co-workers.