Indeed the XFH method manages to produce a steeper potential for the |F1s -1 6a 1 1g state, than the TD-DFT and DFT-ROCIS, see FIG. . We also see that when the XFH potential energy cut is used to compute the vibrational profile of the XA spectrum, a broader spectrum is achieved though it still fails to match the experimental broadness, see FIG. . Hence the |F1s -1 6a 1 1g core-excited state computed with the XFH is used for computing the dynamical effects of F 5 S-F bond dissociation on the RIXS spectra, with both DFT-ROCIS and TD-DFT valence-excited states. Emission along the vertical polarization was found to be twice the horizontal polarization for the elastic line, which is reflected in the vibrational tail in the experimental spectrum at energies lower that 687 eV.