POSITRONIUM FORMATION IN POSITRON HELIUM COLLISION

The authors apply the first-order target continuum distorted wave (TCDW1) approximation to electron capture by positrons from helium into the ground state of positronium. Total cross sections for positronium formation are found to be in good agreement with the measurement of Fromme et al. (1986) above 160 eV. This is the energy range in which most theoretical results disagree with the measurements and indeed in previous classical trajectory Monte Carlo (CTMC) calculations it has been suggested that the experiments incorrectly describe large-angle ionization as charge transfer. The authors elaborate on this matter.