A theoretical study of the P++SH2 reaction:: Potential energy surfaces and reaction dynamics

A theoretical study of the reaction of P+ with SH2 has been carried out. We employed an approximate classical trajectory method to deal with the capture process and a RRKM-type approach to analyze the evolution of the (PSH2)(+) complex. The trajectory computations allowed for nonadiabatic transitions whose probabilities were computed through the Landau-Zener and Rosen-Zener-Demkov models. The potential energy surfaces were computed with the G2(QCI) method for the local minima and with the MR-AQCC and PMP2 methods for the energy profiles. This reaction is interesting from the theoretical point of view, for it generates electron-transfer products as well as two other products. The corresponding reaction paths are identified, and estimates of the reaction rates are given. The experimental values of the PSH+/PS+ branching ratio could not be explained without considering the major role of the singlet potential energy surface. The results even point to a HPSH+-((1)A') species, which is the global minimum of the potential surface, as the reaction intermediate from which both products are generated.