PULSE-RADIOLYSIS STUDY OF THE REACTION OF SO5-CENTER-DOT- WITH HO2-CENTER-DOT

The reaction between SO5.- and HO2. in aqueous solutions has been stud ied by pulse radiolysis and found to have a rate constant of (1.7 +/- 0.1) x 10(9) dm(3) mol(-1) s(-1) at ca. 20 degrees C. This makes it a potentially important chain-terminating step in the free-radical-induc ed chain oxidation of S-IV to S-VI in cloud water. The product of the reaction has a strong optical absorption band with lambda(max) at 260 nm and epsilon(max) = 270 +/- 14 m(2) mol(-1). This product, which may be a tetroxide, undergoes a pH-dependent first-order decay and also r eacts with S-IV in a pH-dependent manner, consistent with it having a pK(a) = 4.8.