SPECTROKINETIC STUDY OF SF5 AND SF5O2 RADICALS AND THE REACTION OF SF5O2 WITH NO

UV spectra of SF5 and SF5O2 radicals in the gas phase at 295 K have be en quantified using a pulse radiolysis UV absorption technique. The ab sorption spectrum of SF5 was quantified from 220 to 240 nm. The absorp tion cross section at 220 nm was (5.5 +/- 1.7) x 10(-19) cm2. When SF5 was produced in the presence of 02 an equilibrium between SF5, O2, an d SF5O2 was established. The rate constant for the reaction of SF5 rad icals with 02 Was (8 +/- 2) x 10(-13) cm3 molecule-1 s-1. The decompos ition rate constant for SF5O2 was (1.0 +/- 0.5) x 10(5) s-1, giving an equilibrium constant of K(eq) = [SF5O2]/[SF5][O2] = (8.0 +/- 4.5) x 1 0(-18) cm3 molecule-1. The SF5-O2 bond strength is (13.7 +/- 2.0) kcal mol-1. The SF5O2 Spectrum was broad with no fine structure and simila r to the UV spectra of alkyl peroxy radicals. The absorption cross sec tion at 230 nm was found to (3.7 +/- 0.9) X 10(-18) cm2. The rate cons tant of the reaction of SF5O2 with NO was measured to (1.1 +/- 0.3) x 10(-11) cm3 molecule-1 s-1 by monitoring the kinetics of NO2 formation at 400 nm. The rate constant for the reaction of F atoms with SF4 was measured by two relative methods to be (1.3 +/- 0.3) x 10(-11) cm3 mo lecule-1 s-1. (C) 1994 John Wiley & Sons, Inc.