Ab initio study of collisions between Li+ or H+ ions and H2 (D2, DT, T2) molecules

We evaluate single-capture cross sections in collisions of H+ or Li+ ions with H2 (D2, DT, T2) molecules in a range of impact energies of 50 eV amu-1-6.25 keV amu-1. We present the first theoretical treatment for Li+ projectiles, we extend the energy range of previous treatments for H+ and we test the accuracy of simplified approaches, such as the Franck-Condon approximation and a new angle-averaging procedure. For H+ + H2, a significant enhancement of the capture cross section is predicted when the H2 target is initially in its first excited vibrational state. (author)