Pulse radiolysis study of the reaction of SO5˙– with HO2˙

Abstract

The reaction between SO₅˙^– and HO₂˙ in aqueous solutions has been studied by pulse radiolysis and found to have a rate constant of (1.7 ± 0.1)× 10⁹ dm³ mol^–1 s^–1 at ca. 20 °C. This makes it a potentially important chain-terminating step in the free-radical-induced chain oxidation of S^IV to S^VI in cloud water. The product of the reaction has a strong optical absorption band with λ_max at 260 nm and ε_max= 270 ± 14 m² mol^–1. This product, which may be a tetroxide, undergoes a pH-dependent first-order decay and also reacts with S^IV in a pH-dependent manner, consistent with it having a pK_a= 4.8.