SEMICLASSICAL DESCRIPTION OF ANTIPROTON CAPTURE ON ATOMIC HELIUM

A semiclassical, many-body atomic model incorporating a momentum-dependent Heisenberg core to stabilize atomic electrons is used to study antiproton capture on helium. Details of the antiproton collisions leading to eventual capture are presented, including the energy and angular-momentum states of incident antiprotons which result in capture via single- or double-electron ionization, i.e., into He2+ pBAR or He+ pBAR, and the distribution of energy and angular-momentum states following the Auger cascade. These final states are discussed in light of recently reported, anomalously long-lived antiproton states observed in liquid He [Iwasaki et al., Phys Rev. Lett. 67, 1246 (1991)].