Kinetics of formation and unimolecular decomposition of the FS(O2)OOO radical

Abstract The kinetics and mechanism of the 193 nm laser flash photolysis of FSO 2 OF in the presence of O 2 and the bath gases N 2 and CF 4 were studied at 295 and 383 K. FSO 3 radicals and F atoms are formed in the primary photolytic process. Subsequently, the FO 2 radicals, produced by the combination of F with O 2 , react with FSO 3 leading to the intermediate trioxide FS(O 2 )OOOF. To explain the build-up of the roomtemperature, time-resolved absorption signals observed at 450 nm, the formation of the novel FS(O 2 )OOO radical, via F atom abstraction from the trioxide by FO 2 , is proposed. FS(O 2 )OOO then dissociates unimolecularly on a millisecond timescale into FSO 3 and O 2 . This radical is not formed by recombination of FSO 3 with O 2 . At 383 K, the faster thermal decomposition of FO 2 radicals precludes the formation of FS(O 2 )OOO.