Polyhalide photofragment spectra. II. Ultraviolet photodissociation dynamics of UF6

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Abstract
Phtotfragment spectroscopy of UF6 at a wavelength of 266 nm shows evidence for direct photodissociation to F atoms and UF5 radicals. A bimodal distribution of F‐atom flight times and nonisotropic recoil angular distributions are found. UF5 fragments are formed with two distinct internal energy distributions separated by approximately 10 kcal mole−1. Measurements of photofragment production as a function of photolyzing light intensity rule out the possibility of a sequential two photon process. Analysis in terms of the UF6 absorption spectrum suggests both UF5 internal energy distributions involve UF5 radicals that are electronically excited with different amounts of electronic and vibrational energy. Population of these two distributions could arise either from absorption to two different electronically excited states of UF6 or from a single excited state that undergoes a curve crossing in the exit channel. The nonisotropic photofragment angular distributions imply both internal energy distributions evolve from UF6 states that are not octahedral in configuration. The nature of this geometrical distortion and its relationship to vibronic transitions in UF6 are discussed.