FIG. 4.

Mn L_3,2-edge partial-fluorescence yield x-ray absorption spectra of PS II and inorganic high-spin model complexes as measured in solution (see Fig. 1 for molecular structures). Top to bottom: 500 mM Mn²⁺_aq solution [the Mn²⁺_aq spectrum is the same as in Fig. 2(b)], three inorganic Mn₃CaO_x model complexes with Mn concentrations of 6–15 mM (structures are given in Fig. 1), and the Mn₄CaO₅ cluster in PS II with a Mn concentration of 0.8 mM measured for the S₁ dark resting state (green circles, black line) and an illuminated PS II sample (2 F, meaning that it was illuminated with two optical flashes) in an S₃-enriched state (orange circles, red line). The solid lines for the PS II measurements are the original data binned to energy regions of 0.8 eV.