TEMPERATURE-DEPENDENCE OF THE REACTIONS OH + O-2- AND OH + HO2 IN WATER UP TO 200-DEGREES-C

Rate constants for the reactions OH + O2- and OH + HO2 have been determined in water up to 200-degrees-C by pulse radiolysis of O2-saturated solutons at pH 7.9 (O2-) and pH 2 (HO2) as measured at room temperature. The rate constants were obtained by using the computer code FACSIMILE to simulate the measured absorbance-time profiles. Good agreement between simulation and experiment could be achieved only by including HO3- and H2O3 as long-lived weakly absorbing products, and using values of the molar absorption coefficients of O2- and HO2 that have been redetermined in this work to be ca. 15% lower than the recommended values in the literature. The temperature dependence of each rate constant is less than that expected for diffusion-controlled reactions, with the effect being more marked for OH + HO2.