Schematic of x-ray absorption, emission, and RIXS processes involving valence electronic states. The upper figure shows the important energy levels in both the LMCT and MLCT we observe. and represent the energy of the incident and emitted photons, respectively. The energy transfer is labeled . Orbital symmetries are assigned with our DFT calculations as described in the text. The lower figure shows the ground and charge transfer final state electronic configurations involved in the RIXS measurements. The atomic specificity of the RIXS process, in conjunction with quantum chemical calculations, allows the covalency of the final state electron and hole orbitals to be determined.
(a) Manganese K-edge x-ray absorption spectrum of . The inset shows the area of interest in our RIXS measurements. (b) Nonresonant x-ray emission spectrum of excited with an incident energy of 7000 eV.
(a) RIXS spectra taken in the low energy transfer region. The energy transfer axis is simply the difference between the incident and emitted x-ray energies. The spectrum is split into two sections with different scalings to show features more clearly, with scaling for the left and the right panels respectively shown on the left and right sides of the color bar. Solid diagonal lines are drawn at constant emission energies corresponding to the fluorescence peaks in the NRXES. The labels , , and refer to the intermediate states excited in the RIXS process. The brackets enclose the three final state holes generated in the RIXS process for each absorption resonance. The MLCT label refers to the final state hole generated in the RIXS process when resonantly exciting the unoccupied orbital. The labels in the contour plot can be related to the transitions presented in Fig. 6. (b) Resonant emission spectra extracted from the RIXS spectrum. Starting from the bottom, the incident energies are 6539.1, 6541.4, and 6545.0 eV. A simple fit was performed assuming all features have a Gaussian line shape with the following color code: blue dots (data), red, pink, and cyan (three emission peaks with a -symmetry valence hole in the final state), yellow (residual Raman feature from detuned excitation of absorption peaks at higher incident energies), green (MLCT peak with a -symmetry valence hole in the final state), blue line (sum of all spectral components).
Calculated orbitals and orbital energy values calculated with ADF. Occupied and unoccupied orbitals are labeled o and uo, respectively. Energies reported in eV directly from the calculation. Only one orbital is shown for each degenerate level. For the level, the metal mixing is from the orbital.
(a) Normalized constant energy transfer spectra extracted from RIXS plane. The energy transfer values selected are 6.0 eV (solid) and 10.8 eV (dotted). (b) X-ray absorption spectrum (dashed) for the same incident energy range.
Summary of the electronic transitions accessed with our RIXS measurement. Labels correspond to features shown in Fig. 3(a). MLCT transition is drawn with a black dashed line. Grey dashed lines show the energy transfer observed in each transition (not drawn to scale).
Peak positions and relative intensities extracted from Gaussian fits of experimental RIXS data. Relative intensities calculated in reference to the highest intensity peak at incident energy of 6545.0 eV and energy transfer of 9.0 eV.
Energies and symmetry adapted molecular fragment percentages for DFT calculated orbitals. Unless noted in the orbital label, values reported are for spin, which are essentially degenerate with the spin orbitals.
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