A spectrokinetic study of CH 2 I and CH 2 IO 2 radicals

The UV absorption spectrum and kinetics of CH 2 I and CH 2 IO 2 radicals have been studied in the gasphase at 295 K using a pulse radiolysis UV absorption spectroscopic technique. UV absorption spectra of CH 2 I and CH 2 IO 2 radicals were quantified in the range 220–400 nm. The spectrum of CH 2 I has absorption maxima at 280 nm and 337.5 nm. The absorption cross‐section for the CH 2 I radicals at 337.5 nm was (4.1 ± 0.9) × 10 −18 cm 2 molecule −1 . The UV spectrum of CH 2 IO 2 radicals is broad. The absorption cross‐section at 370 nm was (2.1 ± 0.5) × 10 −18 cm 2 molecule −1 . The rate constant for the self reaction of CH 2 I radicals, k = 4 × 10 −11 cm 3 molecule −1 s −1 at 1000 mbar total pressure of SF 6 , was derived by kinetic modelling of experimental absorbance transients. The observed self‐reaction rate constant for CH 2 IO 2 radicals was estimated also by modelling to k = 9 × 10 −11 cm 3 molecule −1 s −1 . As part of this work a rate constant of (2.0 ± 0.3) × 10 −10 cm 3 molecule −1 s −1 was measured for the reaction of F atoms with CH 3 I. The branching ratios of this reaction for abstraction of an I atom and a H atom were determined to (64 ± 6)% and (36 ± 6)%, respectively. © 1994 John Wiley & Sons, Inc.