Excimer laser-induced temperature jump-measurements on the recombination kinetics of the gas-phase FSO3 + FSO3 ? F2S2O6 equilibrium between 415 and 525 K

The kinetics of the recombination reaction corresponding to the FSO 3 +FSO 3 ⇔F 2 S 2 O 6 equilibrium system has been studied. A time-resolved absorption spectroscopy technique was employed to monitor the appearance of thermally generated FSO 3 radicals at 450 nm following a small temperature jump induced after partial laser photodissociation of F 2 S 2 O 6 at 193 nm. The recombination rate constants have been determined over the temperature range 415-525 K and a N 2 pressure range 10-600 torr.The reaction was found to be in its first order regime. The resulting limiting high pressure rate constants were combined with previous values measured in this laboratory at lower temperatures yielding the expression k rec,x =(4.5±0.2)×10 −14 (T/300) (1.0±0.1) cm 3 molecule −1 s −1 betweem 293 and 525 K. The temperature coefficient of k rec,x is smaller than the one derived from strady-state experiments of the thermal dissociation of F 2 S 2 O 6 and the equilibrium constant of the system. A recently formulated version of the canonical statistical adiabatic channel model was used to interprete the rate constants