Fig. 3. Electronic and spin effects on RIXS spectral features. (a) RIXS spectra of the three relevant electronic species GS-RIXS, LMCT-RIXS and Quartet-RIXS simulated within the optimized structure of the GS. (b) Molecular orbital type assignments of the dominant electronic transitions for the marked RIXS spectral features. Absorption resonances a, b and c are shown with black arrows. Elastic features, enumerated with subscript 0, are marked with gray text and shown with gray arrows. Inelastic features, enumerated with positive subscripts, are marked with green text and shown with green arrows. Anti-Stokes features (negative energy loss) are instead indexed with negative subscripts (the b_–1 transition by a nominal two-electron transition, as indicated by the two green arrows). Core-excited electrons (from the RIXS probe) are shown in black, whereas valence excited electrons (due to the pump and subsequent excited-state dynamics) are shown in orange.