Determination of the Rate Constant for the OH(X2II) + OH(X2II) → H2O + O(3P) Reaction Over the Temperature Range 295 to 701 K

The rate constant for the radical-radical reaction OH((XII)-I-2) + OH((XII)-I-2) -> H2O + O(P-3) has been measured over the temperature and pressure ranges 295-701 K and 2-12 Torr, respectively, in mixtures of CF4, N-20,N- and H2O. The OH radical was produced by the 193 nm laser photolysis of N2O. The resulting O(D-1) atoms reacted rapidly with H2O to produce the OH radical. The OH radical was detected by high-resolution time-resolved infrared absorption spectroscopy using a single A-doublet component of the OH(1,0) P-1e/(f)(4.5) fundamental vibrational transition. A detailed kinetic model was used to determine the reaction rate constant as a function of temperature. These experiments were conducted in a new temperature controlled reaction chamber. The values of the measured rate constants are quite similar to the previous measurements from this laboratory of Bahng and Macdonald (J. Phys. Chem. A 2007, 111, 3850-3861); however, they cover a much larger temperature range. The results of the present work do not agree with recent measurements of Sangwan and Krasnoperov (J. Phys. Chem. A 2012, 116, 11817-11822). At 295 K the rate constant of the title reaction was found to be (2.52 +/- 0.63) X 10(-12) cm(3) molecule(-1) s(-1), where the uncertainty includes both experimental scatter and an estimate of systematic errors at the temperature range of the experiments, the rate constant can be represented by k(1a) = 4.79 x 10(-18)T(1.79) exp (879.0/T) cm(3) molecule(-1) s(-1) a uncertainty of +/- 24% at the 2 sigma level, including experimental scatter and systematic error.