ONE-ELECTRON AND 2-ELECTRON CAPTURE IN COLLISIONS OF SLOW B4+ AND BE4+ IONS WITH HELIUM

One-electron and two-electron capture in slow B4+-He and Be4+-He collisions are studied within the semiclassical close-coupling description with two-electron atomic basis sets. For B4+-He collisions, we find large two-electron capture cross sections to 2l2l' doubly excited projectile states. Double-capture cross sections to 2s(2)1S(e), 2s2p P-1(o), and 2p(2)1D(e) states and the relative M distributions are found to be in good agreement with recent experiments. Earlier data on B3+ production are found to contain large portions of double transfer followed by autoionization. For the Be4+-He system, the summed cross sections from this work agree with an earlier theoretical study within the adiabatic model. Discrepancies remain, however, for this system in the distribution of double transfer over final states.