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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•...

A frequency doubled tunable dye laser system with ∼0.4 cm−1 resolution was used to measure the integrated absorption cross sections of more than 20 rotational transitions in the O2 Herzberg I (A 3Σ+u←X 3Σ−g) 8‐0 and 9‐0 vibrational bands near 248 nm and 249 nm. Oxygen pressures from 200 to 800 Torr and path lengths from 5 to 25 m were employed. The measured absorbances were fitted using a nonlinear least squares analysis and Beer’s Law to obtain absolute values for the individual transition integrated cross sections in good agreement with a recent spectral simulation and experimental data. By using the spectral simulation in conjunction with the present experimental results, total oscillator strengths in reasonable agreement with literature values were estimated for the 8‐0 and 9‐0 vibrational bands.

Sulfate radical anion SO4- was generated by 248 nm laser flash photolysis of K2S2O8 solutions and monitored by time-resolved multipass absorbance at 454 nm. The 320−520 nm absorption spectrum of SO4- was unaffected by up to 2 M added HClO4, under the experimental conditions. Three reactions were investigated: (a) SO4- + SO4- → S2O82-, (b) SO4- + H2O → HSO4- + OH, and (c) SO4- + S2O82- → products. Rate constant kc was too slow to be measured, and only an upper limit was determined: kc ≤ 104 M-1 s-1. Arrhenius parameters were determined at low ionic strength over the range 11.8−74.4 °C: 2ka /e = (4.8 ± 2.0) × 105 exp(−1.7 ± 1.1 kJ mol-1/RT) cm s-1 and kb = (4.7 ± 0.1) × 103 exp(−15.5 ± 0.6 kJ mol-1/RT) M-1 s-1, where e is the SO4- absorption coefficient at 454 nm. At 296 K, the values are in good agreement with literature values: 2ka/e = (2.5 ± 0.2) × 105 cm s-1 and kb[H2O] = 440 ± 50 s-1. Rate constants ka and kb were found to increase strongly and nonlinearly with increasing ionic strength (added NaCl...