COUPLED QUANTUM TREATMENT OF VIBRATIONALLY INELASTIC AND VIBRONIC CHARGE-TRANSFER IN PROTON-O2 COLLISIONS

A three-dimensional quantum-mechanical study of vibrational, state-resolved differential cross sections (DCS) for the direct inelastic and for the charge-transfer scattering channels has been carried out for the H++O2 system. The collision energy considered was Ec.m.=23.0 eV, which is the same as that examined by Noll and Toennies in their experiments [J. Chem. Phys. 85, 3313 (1986)]. The scattering treatment employed was the charge-transfer infinite-order sudden approximation (CT IOSA) with the vibrational states correctly expanded over the relevant adiabatic basis for each of the two electronic channels. The state-to-state DCS are found to follow closely the behavior of the experimental quantities, both in the inelastic and the charge-transfer channels. Moreover, a careful comparison between the measured relative probabilities and computed values allows us to test in minute detail the efficiency of the scattering model and the reliability of the potential-energy surfaces employed. It is found that vibrational energy transfer is overestimated in the vibrational inelastic channels while in the charge-transfer inelastic channels the same energy transfer is slightly underestimated by the calculations. The total flux distribution, however, is found to be in very good accord with experiments. Angular distributions are also well reproduced both by the DCS and by the average energy-transfer values. The study of some of the CT IOSA quantities also allows us to establish clearly the importance of nonadiabatic transitions in enhancing vibrational inelasticity in the present system.