Journal of Physical Chemistry A, Vol.111, No.19, 3850-3861, 2007
Determination of the rate constant for the OH(X-2 Pi)+OH(X-2 Pi) -> O(P-3)+H2O reaction over the temperature range 293-373 K
The rate constant for the reaction OH(X-2 Pi) + OH(X-2 Pi) -> O(P-3) + H2O has been measured over the temperature range 293-373 K and pressure range 2.6-7.8 Torr in both Ne and Ar bath gases. The OH radical was created by 193 nm laser photolysis of N2O to produce O(D-1) atoms that reacted rapidly with H2O to produce the OH radical. The OH radical was detected by quantitative time-resolved near-infrared absorption spectroscopy using Lambda-doublet resolved rotational transitions of the first overtone of OH(2,0) near 1.47 mu m. The temporal concentration profiles of OH were simulated using a kinetic model, and rate constants were determined by minimizing the sum of the squares of residuals between the experimental profiles and the model calculations. At 293 K the rate constant for the title reaction was found to be (2.7 +/- 0.9) x 10(-12) cm(3) molecule(-1) s(-1), where the uncertainty includes an estimate of both random and systematic errors at the 95% confidence level. The rate constant was measured at 347 and 373 K and found to decrease with increasing temperature.