State-Resolved Collision-Induced Electronic Transitions

Laser and molecular beam techniques have enabled researchers to determine the rovibrational levels populated in collision-induced electronic transitions from specified initial levels of several diatomic molecules. As exemplified by the N2+- and CN-rare-gas systems, such measurements, in combination with theoretical calculations of cross sections for these state-to-state collisional processes, provide a means to understand in detail the dynamics of these electronic quenching and energy transfer processes. The present article reviews state-to-state studies of collision-induced electronic transitions. The various collision systems studied provide examples of both perturbation-assisted "gateways" between the initial and final electronic states and perturbation-independent transitions enabled by nonadiabatic mixing induced by the collision partner.