To highlight the fitting capabilities of SpectraFit, the previously published X-ray spectroscopic data on iron-sulfur model complexes for Nitrogenase by DeBeer and coworkers is analyzed in the following section; see also the 'Notice to the Reader' at the end of the publication. Figure displays the chosen complexes for this demonstration, two diiron clusters [L2Fe2] and [L2Fe2]{DMAP}, which are labeled as 1 and 2. Both clusters 1 and 2 have ligand (L = {[Ph2P(S)]2C} 2-), while complex 2 is additionally substituted by DMAP (DMAP = [4-dimethylpyridin]). Complex 1 is an all-ferrous dimer 2Fe II , while complex 2 has mixed-valence Fe II Fe III . 7 X-ray absorption spectroscopy (XAS) , high energy resolution fluorescence detected (HERFD) XAS , and 1s3p Resonant Inelastic X-ray Scattering (RIXS) , also known as resonant X-ray Emission Spectroscopy (RXES) , were used to measure both complexes; for the purpose of this study, we are focusing on the XAS results.