State-selected reactive collisions of diatomic molecular ions by a coincidence technique

A technique which utilizes coincidence measurements of ion-molecule rearrangement products with threshold electrons ejected when reactant ions were produced by photoionization of parent molecules has been applied to investigate the state-selected reaction cross sections for H2+(v)+H2→H3++H and CO+(v)+D2→COD++D. In the former reaction, it has been found that the cross section decreases with increasing vibrational energy (up to v=5) at low collision energies (e.g. at 0.11 eV CM) but is almost independent of vibrational energy at high collision energies (e.g. at 0.93 eV CM). In the latter reaction the cross sections for v=0 and 1 were almost the same even at the lowest collision energy studied (approximately 0.04 eV CM). (Auth.)