Figure 4.

(A) Absorption spectra of the radicals CO₃·⁻, Cl₂·⁻, and SO₄·⁻ produced by laser flash photolysis of 2.5 mM H₂O₂ + 0.1 M Na₂CO₃ (CO₃·⁻), of 2.5 mM H₂O₂ + 0.01 M NaCl (pH 3, adjusted with HClO₄) (Cl₂·⁻), and of 10 mM Na₂S₂O₈ (SO₄·⁻). The absorbance signals were taken soon after the laser pulse. Laser irradiation at 266 nm, 35 mJ·pulse⁻¹; (B) First-order decay constants of the studied radical species (SO₄·⁻, Cl₂·⁻, CO₃·⁻) as a function of MA concentration. The radical species were obtained by laser irradiation of 10 mM Na₂S₂O₈ (SO₄·⁻), of 2.5 mM H₂O₂ + 0.01 M NaCl at pH 3 (Cl₂·⁻), and of 2.5 mM H₂O₂ + 0.1 M Na₂CO₃ (CO₃·⁻). The slopes of the lines give the second-order reaction rate constants between the relevant radicals and MA (Stern-Volmer approach).