Positron scattering by the negative hydrogen ion

Results are presented for e+ scattering by H- in the impact energy range 0≤E0≤10 eV. These include integrated cross sections for Ps formation in the 1s, 2s, and 2p states, as well as in an aggregate of states with n≥3, and for direct ionization. Differential cross sections for Ps formation in the 1s, 2s, and 2p states are also exhibited. The calculations are based on a coupled pseudostate approach employing 19 Ps pseudostates centered on the e+. It is found that Ps formation in the 2p state dominates that in the 1s or 2s states below 8 eV, that formation in states with n≥3 exceeds the sum of the n=1 and n=2 cross sections above 2.5 eV, and that direct ionization outstrips total Ps formation above 6.3 eV. The threshold law (E0→0) for exothermic Ps formation, which includes the cases Ps(1s), Ps(2s), and Ps(2p), is shown to be 1/E0