Fig. 3: Analysis of dd-excitations in Cu₂OSeO₃.

a–p Resonant inelastic X-ray scattering (RIXS) spectra (dots), in the 0.8–2.5 eV region, as a function of incident energy across the Cu L₃ edge. The error bars are defined assuming a Poisson distribution of the single-photon counted events. The fitted components are colored in aquamarine for the Cu-I dd-excitations (E1 and E3), and in purple for the Cu-II dd-excitations (E2, E4, E5, and E6). The sum of the fitted components is represented as a pink, thick solid line. q, r Summary of the fitted dd-excitation energies across the Cu L₃ edge, with the assigned orbital character following density functional theory (DFT) calculations. s Site-resolved dd-excitation amplitudes A^CuI (aquamarine dots) and A^CuII (blue dots). The error bars, extracted from the fitting through the error propagation method, are contained within the marker size. The smoothed lines underneath are a guide for the eyes. The sum of the A^CuI and A^CuII amplitudes is displayed by the pink dots. A rescaled total fluorescence yield (TFY) profile is plotted in the same figure using a blue solid line. Vertical dotted lines mark the resonant energy extracted for Cu-I ion at 930.6 eV and Cu-II ion at 931.15 eV.