POSITRONIUM AND ANTIHYDROGEN FORMATION IN THE E+-H AND PS-(P)OVER-BAR SYSTEMS

The close coupling equations for the e+-H and Ps-p- systems are solved for a model calculation comprising three hydrogen H(1s,2s,2p) and three positronium Ps(1s,2s,2p) states. The summed cross section for Ps formation in the Ps(1s), Ps(2s), and Ps(2p) states for e++H- Ps+p reaction achieves a peak of 2.7pia0(2) and is smaller than the only existing set of experimental data. The cross section for antihydrogen formation in the Ps + pBAR --> e+ + HBAR reaction reaches a maximum of (13-14)pia0(2) for incident antiproton energies between 6.5 and 11 keV.