Kinetics of formation and unimolecular decomposition of the FS(O-2)OOO radical

The kinetics and mechanism of the 193 nm laser flash photolysis of FSO2OF in the presence of O-2 and the bath gases N-2 and CF4 were studied at 295 and 383 K. FSO3 radicals and F atoms are formed in the primary photolytic process. Subsequently, the FO2 radicals, produced by the combination of F with O-2, react with FSO3 leading to the intermediate trioxide FS(O-2)OOOF. To explain the build-up of the room-temperature, 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 FO2, is proposed. FS(O-2)OOO then dissociates unimolecularly on a millisecond timescale into FSO3 and O-2. This radical is not formed by recombination of FSO3 with O-2. At 383 K, the faster thermal decomposition of FO2 radicals precludes the formation of FS(O-2)OOO. (C) 1997 Elsevier Science S.A. All rights reserved.