A key question for the understanding of photosynthetic water oxidation is whether the four oxidizing equivalents necessary to oxidize water to dioxygen are accumulated on the four Mn ions of the oxygen evolving complex (OEC), or whether some ligand-centered oxidations take place before the formation and release of dioxygen during the S{sub 3} {r_arrow} [S{sub 4}] {r_arrow} S{sub 0} transition. Progress in instrumentation and flash sample preparation allowed us to apply Mn K{beta} X-ray emission spectroscopy (Kb XES) to this problem for the first time. The K{beta} XES results, in combination with Mn X-ray absorption near-edge structure (XANES) and electron paramagnetic resonance (EPR) data obtained from the same set of samples, show that the S{sub 2} {r_arrow} S{sub 3} transition, in contrast to the S{sub 0} {r_arrow} S{sub 1} and S{sub 1} {r_arrow} S{sub 2} transitions, does not involve a Mn-centered oxidation. This is rationalized by manganese {mu}-oxo bridge radical formation during the S{sub 2} {r_arrow} S{sub 3} transition. Using extended X-ray absorption fine structure (EXAFS) spectroscopy, the local environment of the Mn atoms in the S{sub 0} state has been structurally characterized. These results show that the Mn-Mn distance in one of the di-{mu}-oxo-bridged Mn-Mn moieties increases from 2.7 …