Kinetic study of the reaction of OH with CH2I2

Flash photolysis (FP) coupled to resonance fluorescence (RF) was used to measure the absolute rate coefficients (k1) for the reaction of OH(X2P) radicals with diiodomethane (CH2I2) over the temperature range 295374 K. The experiments involved time-resolved RF detection of the OH (A2∑+→X2Π transition at λ = 308 nm) following FP of the H2O/CH2I 2/He mixtures. The OH(X2Π) radicals were produced by FP of H2O in the vacuum-UV at wavelengths l 4 120 nm. Decays of OH radicals in the presence of CH2I2 are observed to be exponential, and the decay rates are found to be linearly dependent on the CH2I 2 concentration. The results are described by the Arrhenius expression k1(T) = (4.2 ± 0.5) × 1011 exp[-(670 ± 20)K/T] cm3 molecule-1 s-1. The implications of the reported kinetic results for understanding the atmospheric chemistry of CH2I2 are discussed. © 2011 the Owner Societies