First studies of state-selective electron capture in collisions of state-prepared ions with atomic hydrogen; the case of C2+-H(1s)

The technique of double translational energy spectroscopy has been used for the first time with an atomic hydrogen target. We have carried out measure ments of state-selective one-electron capture in 6 keV C2+-H(1s) collisions which avoid the ambiguities in interpretation of previous experiments and allow separate identification of the collision channels associated with eit her C2+(2s(2))S-1 ground-state or C2+(2s2p)P-3(o) metastable primary ions. In a theoretical counterpart, partial cross sections for both reactions hav e been calculated using a semiclassical molecular approach. There is good a greement between experiment and calculations.