Laser photolysis of UF6: Reactions of the transient UF5 molecules

Abstract

Laser photolysis of UF6 at 248 nm produces vibrationally and translationally excited UF5 and F. At very low pressures (<0.1 Torr) in a long path-length reaction cell collisional stabilization is inefficient, which tends to increase the lifetime of the transient UF5 molecule. From the kinetic analysis of the UF5 absorption–decay curve and the UF6 depletion measurements the following dimerization and fluorine atom recombination rate constants were determined for 298 K. RRKM calculations were performed for the formed UF6 molecule which indicated the unimolecular decomposition rate constant to be ∼1×106 s−1. The calculated results indicate that in the primary photolysis about 2/5 of the excess energy above the threshold energy was partitioned into the relative translational energy which is in good agreement with the experimental kinetic analysis and also with the available molecular beam data. The translational energy release from the decomposition of the chemically activated UF6 molecule is small and two energetically different UF5 species are suggested.