A laser photolysis-resonance fluorescence study of the reactions: I+O-3 -> IO+O-2, O+I-2 -> IO+I, and I+NO2+M -> INO2+M at 298 K

Laser. ash photolysis coupled to resonance-fluorescence detection of I atoms was used to measure the rate coefficients for the reactions: I + O-3 -> IO + O-2 (R1), O + I-2 -> IO + I (R6) and I + NO2 + M -> INO2 + M (R7). All experiments were conducted under pseudo first-order conditions, and the accuracy of the results was enhanced by online determination of reagent concentrations by optical absorption. Bimolecular rate coefficients for reactions (R1) and (R6) were determined to be k(1) = (1.28 +/- 0.06) x 10(-12) and k(6) = (1.2 +/- 0.1) x 10(-10) cm(3) molecule(-1) s(-1) at 298 +/- 2 K, independent of pressure. Rate coefficients for the termolecular reaction (R7), also at 298 +/- 2 K, were found to be in the falloff region between 3rd and 2nd order behaviour and, when combined with other datasets obtained at higher and lower pressures, were adequately described by a simplified Troe function with the parameters: k(7,0)(He, 330 K) = 1.48 x 10(-31) cm(6) molecule(-2) s(-1), FC(He) = 0.43, and k(7,infinity) = 1.1 x 10(-10) cm(3) molecule(-1) s(-1) for He as bath gas. In N-2 (or air) the following parameters were obtained k(7,0)(N-2, 300 K) = 3.2 x 10(-31) cm(6) molecule(-2) s(-1), F-C(N-2) = 0.48, with k(7)infinity, set to 1.1 x 10(-10) cm(3) molecule(-1) s(-1) as obtained from analysis of the falloff curve obtained in He.