Fig. 4. Generating (a) and using (b) e˙–aq with the mechanism of Fig. 2a. (a) Main plot, concentration traces of Py˙^2– (red) and e˙–aq (blue) in an experiment with the pulse scheme displayed above the traces, on the solution of Fig. 3b with 30 mM SDS; Py˙^2– trace after the second pulse corrected with the procedure of ESI-4.1.† Inset 1, e˙–aq formation as function of Py˙^2– bleaching, with the concentration changes –Δ[Py˙^2–]_rel and [e˙–aq]_rel taken relative to the concentration of Py˙^2– immediately before the second pulse. Inset 2, relative actinometry of green-light ionization of Py˙^2– with excitation of [Ru(bpy)₃]²⁺ (formation of the emissive state ³[Ru(bpy)₃]²⁺) as reference reaction. Blue data points, [e˙–aq]_rel as in Inset 1 as function of the intensity I₅₃₂ of the second laser pulse. The monoexponential fit by the blue curve, 1 – exp[–I₅₃₂/(558 mJ cm^–2)], validates the monophotonic ionization mechanism. Orange data points and fit curve 1 – exp[–I₅₃₂/(187 mJ cm^–2)], intensity dependence of ³[Ru(bpy)₃]²⁺ emission normalized to maximum. The ratio of these best-fit constants times the ratio of the molar absorption coefficients of the species excited with 532 nm (³[Ru(bpy)₃]²⁺, 1000 M^–1 cm^–1; Py˙^2–, 6200 M^–1 cm^–1) gives the photoionization quantum yield, 0.054. (b) Decomposition of the model compound chloroacetate CICH₂COO^– by e˙–aq generated as in (a). Main plot, decay of e˙–aq in the presence of variable amounts of CICH₂COO^–; inset, resulting Stern–Volmer plot. The same colour coding of the concentrations has been used in the main plot and in the inset. Further explanation, see text and ESI-4.† .