Temperature dependence of the reactions OH + O –2 and OH + HO2 in water up to 200 °C

Abstract

Rate constants for the reactions OH + O^–₂ and OH + HO₂ have been determined in water up to 200 °C by pulse radiolysis of O₂-saturated solutons at pH 7.9 (O^–₂) 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 HO^–₃ and H₂O₃ as long-lived weakly absorbing products, and using values of the molar absorption coefficients of O^–₂ 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.