Fig. 2.

Kβ X-ray emission spectra of Mn oxides (adapted from Bergmann et al. [28]). The Kβ spectra consist of two main features: the Kβ′ peak at ~6475 eV and the Kβ_1,3 peak at ~6490 eV. The separation of these two features is due to the exchange interaction of the unpaired 3d electrons with the 3p hole, which is formed as a final state after the core hole is filled by a 3p→1s fluorescence transition. The spin of the unpaired 3d valence electrons can be either parallel (Kβ′) or antiparallel (Kβ_1,3) to the hole in the 3p level. The splitting between the Kβ′ and Kβ_1,3 peaks becomes smaller for higher oxidation states because fewer 3d electrons interact with the 3p hole. Thus, in contrast to the inflection points of the XANES edges, the Kβ_1,3 peaks shift to lower energy with higher oxidation states, as is seen above with the Mn oxides. The magnitude of the Kβ_1,3 peak first-moment shift for ${\text{Mn}}_2^{\text{III}}{\mathrm{O}}_3\to {\text{Mn}}^{\text{IV}}{\mathrm{O}}_2$ is roughly a factor of four larger than the first-moment shift for the S₁→S₂ transition, where only one Mn out of four is being oxidized.