Antihydrogen formation in low-energy antiproton collisions with excited-state positronium atoms

Abstract

The convergent close-coupling method is used to obtain cross sections for antihydrogen formation in low-energy antiproton collisions with positronium (Ps) atoms in specified initial excited states with principal quantum numbers ni ≤ 5. The threshold behaviour as a function of the Ps kinetic energy, E, is consistent with the 1/E law expected from threshold theory for all initial states. We find that the increase in the cross sections is muted above ni = 3 and that here their scaling is roughly consistent with ${n_{i}^{2}}$ , rather than the classically expected increase as ${n_{i}^{4}}$ .