Analysis of Fe 2p Core-Hole Resonances in Fe2O3 and Fe3O4 Photoemission Spectra Using Asymmetric Coupled-Resonance Peak-Fitting

Abstract

The quantitative analysis of Fe 2p spectra remains challenging because multiplet splitting, strong asymmetry, satellite intensity, and extended background contributions overlap over a broad binding energy range. Here, we revisit the Fe 2p spectra of hematite Fe₂O₃ and magnetite Fe₃O₄, using the Coupled Resonances (CR) line shape combined with the Narrow Shirley (NS) background and a Tougaard extrinsic background. Among the tested approaches, CR Type III provides the best balance between spectral fidelity, integrability, and quantitative stability. It reproduces the main Fe 2p doublet, multiplet-related structure, and satellite region without relying on empirical asymmetric tails or nonintegrable profiles. The extracted resonance energies, lifetime widths, and interference terms show that Fe 2p asymmetry arises from coupling between overlapping final-state resonances. This interference produces a CR-induced shift that accounts for the steep low-binding-energy onset and extended high-binding-energy decay of the Fe 2p envelope. Comparison with cluster-model calculations shows that CR fitting complements multiplet simulations by grouping unresolved final states into experimentally constrained resonances. The Fe₂O₃ composition analysis further shows that recovering nominal stoichiometry does not validate a quantification strategy by itself. The calculated Fe/O ratio depends on O 1s component selection, background implementation, end point definition, and photoionization correction scheme. Overall, CR Type III plus NS analysis provides a mechanistically interpretable and quantitatively stable framework for Fe 2p modeling and Fe/O assessment in iron oxides.