Investigation of multiplet splitting of Fe 2p XPS spectra and bonding in iron compounds

TLDR

The study used XPS to assess whether calculated multiplet peaks can accurately fit high‑resolution Fe 2p 3/2 spectra of high‑spin Fe²⁺ and Fe³⁺ compounds. Calculated multiplet peaks, combined with surface and shake‑up satellite contributions, accurately fit most high‑resolution Fe 2p 3/2 spectra—including Fe₃O₄—and showed that binding energies increase with greater ionic bond character and ligand electronegativity, while the energy gap to shake‑up satellites also widens, with extrinsic loss spectra uniquely characterizing each ion oxide. © 2004 John Wiley & Sons, Ltd.

Abstract

Abstract Ferrous (Fe 2+ ) and ferric (Fe 3+ ) compounds were investigated by XPS to determine the usefulness of calculated multiplet peaks to fit high‐resolution iron 2p 3/2 spectra from high‐spin compounds. The multiplets were found to fit most spectra well, particularly when contributions attributed to surface peaks and shake‐up satellites were included. This information was useful for fitting of the complex Fe 2p 3/2 spectra for Fe 3 O 4 where both Fe 2+ and Fe 3+ species are present. It was found that as the ionic bond character of the iron —ligand bond increased, the binding energy associated with either the ferrous or ferric 2p 3/2 photoelectron peak also increased. This was determined to be due to the decrease in shielding of the iron cation by the more increasingly electronegative ligands. It was also observed that the difference in energy between a high‐spin iron 2p 3/2 peak and its corresponding shake‐up satellite peak increased as the electronegativity of the ligand increased. The extrinsic loss spectra for ion oxides are also reported; these are as characteristic of each species as are the photoelectron peaks. Copyright © 2004 John Wiley & Sons, Ltd.