Antihydrogen formation in antiproton collisions with positronium: the adiabatic approach

The cross section for antihydrogen formation in collision of an antiproton with ground-state positronium has been calculated using the adiabatic hidde ncrossing method. At collision velocities below the cross section maximum ( 3 keV) it is shown that the adiabatic approach provides a very simple descr iption of the positron transfer process, in that capture occurs by a two-st ate mechanism involving coupling between the 1s sigma and 2p sigma potentia l curves only. Good numerical agreement with previous estimates is obtained .