Two-pulse two-laser photodissociations of molecular ions: Collisional relaxation of bromo-3-(trifluoromethyl)-benzene cation

Two-pulse techniques using high power lasers have been developed for the study of collisional deactivation of vibrationally excited molecular ions in the gas phase. Using these techniques, absolute rate constants have been determined for quenching of excited bromo-3-(trifluoromethyl)-benzene cation in a variety of bath gases. These rates are compared to the predictions of two models for collisional energy transfer in ion–molecule collisions. These studies also show that both IR photodissociation after internal conversion of a visible photon and visible photodissociation after IR multiple photon absorption can be operative mechanisms for the ‘‘IR-enhanced’’ visible photodissociation of molecular ions.