Semiclassical collision dynamics with multiple potential surfaces: The H(1(2)S)+N-2(+) example

A simple nonadiabatic process, the collision between an atom and a diatomic homonuclear molecular ion giving rise to different electronic states of th e ionic fragment, is considered for the case of the triatomic system N2H+, in the energy range of 3-40 eV. New correlated potential-energy surfaces, o riginating from a previous full-dimension multireference double configurati on-interaction calculation, are employed and the dynamical calculations on these surfaces are performed by applying the semiclassical multichannel S m atrix in its recent refinements. The collision is studied in a simplified a pproach where the system remains fixed in a collinear arrangement. The dyna mical coordinate is the distance between the H projectile and the N-2(+) ce nter of mass while the N-2(+) vibrations are included a posteriori in a par ametric scheme. First the conditional probabilities for the nonadiabatic pr ocesses involved are extracted from the computed S matrix and then probabil ities at different impact parameters are obtained. The corresponding total cross sections for the two main processes considered, N-2(+)(1 (2)Sigma(g)( +)) + H(1 S-2) -->N-2(+) (1 (2)Sigma(u)(+)) + H(1 S-2) and N-2(+)(1 (2)Sigm a(u)(+)) + H(1 S-2) -->N-2(+)(2 (2)Sigma(u)(+)) + H(1 S-2), are finally com puted. The nonadiabatic cross sections reveal that the formation of N-2(+) in its lowest excited state is largely preferred. An immediate application of this theoretical work is suggested in order to stimulate and direct furt her ion-molecule experiments on the H(1 S-2) + N-2(+) system. [S1050-2947(9 4)0208-3].