MULTI-PHOTON INDUCED INVERSE ELECTRONIC RELAXATION

High-order infrared multiphoton excitation in the ground electronic state of collision free CrO//2Cl//2 has resulted in visible fluorescence. The prompt fluorescence has been studied as a function of laser fluence, pulse duration, under collisional and collison-free conditions and was shown to arise from a spontaneous one-photon radiative decay of molecular eigenstates. Intramolecular scrambling of vibronic levels corresponding to the ground state electronic manifold with a discrete level(s) belonging to the low lying excited electronic state is believed to be the origin of such eigenstates. This fluorescent channel is shown to compete with a dissociative channel forming CrO//2Cl plus Cl; the radical further dissociates to the stable product CrO//2. The threshold for fluorescence versus dissociation is discussed and a branching ratio, and consequent chemical mechanism are suggested.