Flash photolysis (FP) coupled to resonance fluorescence (RF) was used to measure the absolute rate coefficients (k(1)) for the reaction of OH(X(2)Π) radicals with diiodomethane (CH(2)I(2)) over the temperature range 295-374 K. The experiments involved time-resolved RF detection of the OH (A(2)Σ(+)→X(2)Π transition at λ = 308 nm) following FP of the H(2)O/CH(2)I(2)/He mixtures. The OH(X(2)Π) radicals were produced by FP of H(2)O in the vacuum-UV at wavelengths λ > 120 nm. Decays of OH radicals in the presence of CH(2)I(2) are observed to be exponential, and the decay rates are found to be linearly dependent on the CH(2)I(2) concentration. The results are described by the Arrhenius expression k(1)(T) = (4.2 ± 0.5) × 10(-11) exp[-(670 ± 20)K/T] cm(3) molecule(-1) s(-1). The implications of the reported kinetic results for understanding the atmospheric chemistry of CH(2)I(2) are discussed.

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A flash photolysis resonance fluorescence technique has been employed to investigate the kinetics and mechanism of the reaction of OH(X 2 ) radicals with CH 3 I over the temperature and pressure ranges 295-390 K and 82-303 Torr of He, respectively. The experiments involved time-resolved RF detection of the OH (A 2 + → X 2 transition at λ = 308 nm) following FP of H 2 O/CH 3 I/He mixtures. The OH(X 2 ) radicals were produced by FP of H 2 O in the vacuum-UV at wavelengths λ > 115 nm using a commercial Perkin-Elmer Xe flash lamp. Decays of OH in the presence of CH 3 I are observed to be exponential, and the decay rates are found to be linearly dependent on the CH 3 I concentration. The measured rate coefficients for the reaction of OH with CH 3

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Flash photolysis (FP) coupled with resonance fluorescence (RF) was used to measure the absolute rate coefficients for the reactions of OH(X(2)Π) radicals with C(2)H(5)I (k(1)), n-C(3)H(7)I (k(2)), and iso-C(3)H(7)I (k(3)) at temperatures between 297 and 372 K in 188 Torr of He; this represents the first temperature-dependent kinetics studies for the title reactions. The experiments involved time-resolved RF detection of the OH (A(2)Σ(+) → X(2)Π transition at λ = 308 nm) radicals following FP of H(2)O/C(2)H(5)I/He, H(2)O/n-C(3)H(7)I/He, and H(2)O/iso-C(3)H(7)I/He mixtures. The OH(X(2)Π) radicals were produced by FP of H(2)O in vacuum-UV at wavelengths λ > 120 nm. Decays of OH radicals in the presence of C(2)H(5)I, n-C(3)H(7)I, and iso-C(3)H(7)I were observed to be exponential, and the decay rates were found to be linearly dependent on the C(2)H(5)I, n-C(3)H(7)I, and iso-C(3)H(7)I concentrations. The results are described by the following Arrhenius expressions (units of cm(3) molecule(-1) s(-1)): k(1)(297-372 K) = (5.55 ± 3.20) × 10(-12) exp[-(830 ± 90) K/T], k(2)(300-370 K) = (1.65 ± 0.90) × 10(-11) exp[-(780 ± 90) K/T] and k(3)(299-369 K) = (7.58 ± 3.70) × 10(-12) exp[-(530 ± 80) K/T]. Reported errors in E/R and in the pre-exponential factors are 2σ random errors, returned by the weighted (by 1/σ(2)) least-squares fits to the kinetic data. The implications of the reported kinetic results for understanding both atmospheric and nuclear safety interests of C(2)H(5)I, n-C(3)H(7)I, and iso-C(3)H(7)I are discussed.