Spectrokinetic study of SF 5 and SF 5 O 2 radicals and the reaction of SF 5 O 2 with NO

UV spectra of SF 5 and SF 5 O 2 radicals in the gas phase at 295 K have been quantified using a pulse radiolysis UV absorption technique. The absorption spectrum of SF 5 was quantified from 220 to 240 nm. The absorption cross section at 220 nm was (5.5 ± 1.7) × 10 −19 cm 2 . When SF 5 was produced in the presence of O 2 an equilibrium between SF 5 , O 2 , and SF 5 O 2 was established. The rate constant for the reaction of SF 5 radicals with O 2 was (8 ± 2) × 10 −13 cm 3 molecule −1 s −1 . The decomposition rate constant for SF 5 O 2 was (1.0 ± 0.5) × 10 5 s −1 , giving an equilibrium constant of K eq = [SF 5 O 2 ]/[SF 5 ][O 2 ] = (8.0 ± 4.5) × 10 −18 cm 3 molecule −1 . The SF 5 O 2 bond strength is (13.7 ± 2.0) kcal mol −1 . The SF 5 O 2 spectrum was broad with no fine structure and similar to the UV spectra of alkyl peroxy radicals. The absorption cross section at 230 nm was found to (3.7 ± 0.9) × 10 −18 cm 2 . The rate constant of the reaction of SF 5 O 2 with NO was measured to (1.1 ± 0.3) × 10 −11 cm 3 molecule −1 s −1 by monitoring the kinetics of NO 2 formation at 400 nm. The rate constant for the reaction of F atoms with SF 4 was measured by two relative methods to be (1.3 ± 0.3) × 10 −11 cm 3 molecule −1 s −1 . © 1994 John Wiley & Sons, Inc.