Fig. 3. Response of the catalytic system to the laser intensity and the concentration of the sacrificial donor. Graph (a), initial post-flash concentrations c relative to the starting Rubpy concentration c ₀ (50 µM) for OER (green) and e_aq˙^– (blue) as functions of the intensity I ₅₃₂ of a single green laser flash with the Asc^2– concentration as parameter. The gray curves represent a global fit for the kinetic scheme shown in (b); best-fit parameters with the effective laser pulse duration T and with the intensities I ₅₃₂ specified in mJ cm^–2, k _exc T = 6.6 × 10^–3 I ₅₃₂, T/τ = 1.7 × 10^–2, k _q T = 42 M^–1, k _rec T = 0.94, η = 0.48, k _ion T = 6.0 × 10^–4 I ₅₃₂. The ascorbate weight-in concentrations, in ascending order of the curves for each observed species, are 0.5 mM, 1 mM, 2 mM, 5 mM (open symbols and dashed curves, OER only; for clarity, the data and fit curves for e_aq˙^– have been omitted) and 10 mM, 20 mM, 50 mM, 100 mM, 250 mM (filled symbols and solid curves). Experimental temperature, 303 K. Graph (b), enhanced kinetic model used for the global fit, with ³SCRP being the spin-correlated radical pair . For further explanation, see text.