Time-dependent close-coupling calculations of positronium formation in positron-hydrogen collisions

Abstract

Positronium-formation cross sections from positron-hydrogen collisions are calculated by solving a set of close-coupled, time-dependent partial differential equations. These cross sections are determined by propagating a time-evolving wave packet on a two-dimensional radial lattice and then projecting the wave function onto the stationary states of the atom. Calculations are performed through $L=8$ and are extrapolated for $Lg~9$ at energies of 30, 40, and 50 eV. Using distorted-wave calculations to determine ionization cross sections at these higher energies, we are able to extract approximate positronium-formation cross sections from the transfer ionization cross sections. Comparisons are made with experiment.