Fig. 1.

Optical transient absorption (TA) spectra acquired from Ca-MnO₂ in an aqueous suspension containing Nafion at 0.75 ps, 3.6 ps, and 2 ns after photoexcitation at 400 nm. The TA spectra (milli-ΔOD units; left axis) are compared with the ground-state UV-vis absorption spectra (OD units; right axis). Vertical lines at 550 nm (the maximum intensity of the ESA) and at 345 nm (ground-state bleach) indicate wavelengths chosen for kinetics analysis. The data from 390–410 nm are affected by scattering of the excitation beam. Equivalent TA data for Na-MnO₂ are given in Fig. S2A.