Free Radical Reactions Involving Cl•, Cl2-•, and SO4-• in the 248 nm Photolysis of Aqueous Solutions Containing S2O82- and Cl

Rate constants and other properties are reported for photochemical reactions initiated by laser photolysis (248 nm) of S2O82-(aq) in acidic solutions containing Cl-(aq) at 297 ± 2 K. The absorption spectra of SO4-•(aq) and Cl2-•(aq) are measured and compared to literature values. Equilibrium constants and rate constants involving Cl•(aq), Cl2-•(aq), H2O, SO4-•(aq), and S2O82-(aq) are determined by analyzing the formation and decay of Cl2-•(aq) and SO4-•(aq) in a self-consistent chemical mechanism. For the first time, the anticipated pH dependence is observed unambiguously in the pseudo-first-order decay rate constant of Cl2-•. The rate constants for the reactions Cl•(aq) + Cl2-•(aq) → Cl2(aq) + Cl-(aq) and Cl2-•(aq) + Cl2-•(aq) → Cl2(aq) + 2Cl-(aq) are determined; rate constants for the latter are measured as a function of temperature and ionic strength. In addition, the ionic strength dependence of the reaction SO4-•(aq) + Cl-(aq) → SO42-(aq) + Cl•(aq) is reported. Rate constants for the reactions of Cl•...