Electron capture in collisions of Al2+ ions with He atoms at intermediate energies - art. no. 032717

Electron capture resulting from collisions of Al2+ ions with He atoms from 0.15 to 1000 keV/u is investigated using a molecular-orbital representation within a semiclassical frame. Molecular electronic states and correspondin g couplings are determined by the ALCHEMY program. Sixteen molecular states all connecting to single-electron-capture processes are included, and henc e radial and rotational couplings among these channels are fully considered . The trajectory effect arising from the straight-line, Coulomb, and ground -state potential trajectories for electron-capture and excitation processes is carefully assessed. The electron-capture cross section by ground-state Al2+ (S-2) ions slowly increases before it reaches a maximum of 1.3 X 10(-1 6) cm(2) at 100 keV/u. Those for metastable Al2+ (P-2) ions sharply increas e with increasing energy, and reach a peak at 1 keV/u with a value of 1.5 X 10(-16) cm(2). The earlier experimental data are found to be larger by an order of magnitude although their energy dependence is in good accord with the present result. Excitation cross sections for both the ground and metas table states are found to be much larger by a factor of 2-3 than correspond ing capture cross sections above 1 keV/u although they become comparable be low this energy.