Ion-molecule charge exchange: He+ and Ar+ on H2 and N2

Charge exchange in He+ and Ar+ collisions with H2 (D2) and N2 is studied at small angles. This work extends our earlier studies which primarily emphasized the direct inelastic scattering at low keV energies. Using time-of-flight techniques for energy analysis of the scattered atoms, it is directly shown, for the first time, that in Ar+ + H2, Ar+ + N2, and He+ + N2 the dominant small-angle charge-exchange process is quasiresonant (Q approx. = 0). In He+ + H2 there is no available quasiresonant channel, and here the dominant final channels are associated with energy losses from 13 to 18 eV. A simple model is proposed