DOUBLE-ELECTRON CAPTURE IN ION-ATOM COLLISIONS AT HIGH-IMPACT VELOCITIES

Theoretical total cross sections for double electron transfer collisio ns A(q+) + He(1s2) --> A(q-2)+ (SIGMAnl,n'l') + He-2+ (A(q+ is H+, He- 2+, Li-3+ or B-5+) are analysed in the Continuum Distorted Wave approx imation using either an Independent Electron Approximation or a 4-body model. Comparing theoretical results to some available experimental d ata sheds some light on the relevance of both models. The 4-body model predictions agree with experiments for Z(p) = 1 while those correspon ding to the independent electron approximation show reasonable agreeme nt for Z(p) = 2. However, this last model overestimates double capture for Z(p) greater-than-or-equal-to 3.