Large Basis Calculation of Positron?Hydrogen Scattering at Low Energies

Abstract

Calculations of low energy positron-hydrogen scattering using the close coupling approach are reported at low energies. The channel space includes nine physical hydrogen and positronium states and in addition twelve hydrogen and positronium pseudo-states. For energies below the positronium formation threshold, phase shifts are reported for J = 0 to 6 and are believed to have an absolute accuracy of 0�0015 radian or better. Elastic scattering and positronium formation cross sections in the Ore gap for the J = 0 and J = 1 partial waves are essentially identical with previous variational calculations. Total elastic and positronium formation cross sections are reported at incident energies below the ionisation threshold. Cross sections for the excitation of the H(n=2), H(n=3) and Ps( n=2) levels are also reported over a restricted energy range, and the total reaction cross section has been computed and compared with experiment.