Inaccuracies in the XES as compared to XANES led us to investigate the nature of our DFT/CIS parameterization, specifically the shifting of the core orbital energies and why this procedure does not work as well for XES. One observation is that the core hole generated in the non-Aufbau XES reference state, which is an empty unrestricted orbital with β spin, is lower in energy than the corresponding α-spin 1s occupied orbital by about 0.5 E h or ∼ 10 eV. This could adversely interact with the parameterization of ∆ε, which is based on restricted (closed-shell) orbital energies, such that orbital relaxation effects on the core hole are not built into the parameterization although they are included in the XES procedure that is outlined in Section II D. We considered that this might imply that the DFT/CIS parameterization is suitable only to describe excitations out of 1s orbitals, meaning elemental K-edge spectra, and might fail to account for the differential SIE and orbital relaxation effects in the case of L-and M-edge spectra.