Orbitals and Energies #
Note – these are listed in BINDING ENERGY
S 2p ≈ 165 eV
S 2s ≈ 225 eV
S 1s ≈ 2480 eV (HAXPES)
Doublet Separations #
S 2p = 1.19 eV
Common Overlaps for S 2p #
Bi 4f – Cs 4p – Rn 5p – Ac 5p – Te 4s – Er 4d – Se 3p
Theory and Background #
The predominant photoemission for sulfur is the 2p region, which consists of a doublet with a reasonable doublet separation (1.16 eV – Figure 1). This region may overlap with Bi 4f and Se 3p. Distinction of C-S and S-S bonds not possibly by analysis of core levels, but obtaining S LMM / C KLL augers it can be achieved.
Conductive forms of sulfur, such as S8, and some chalcogenides, may exhibit a small amount of asymmetry which should be accounted for for best fitting.
Experimental Advice #
Since binding energy shifts may be small for organic sulfurs and polysulfides, the S 2p:LMM auger parameter may make state identification simpler.(1) Si 2s plasmons can overlap with the S 2p region and render appropriate background simulation difficult in the cases of low S:Si ratio. Recording an extended background, for both Si 2s and Si 2p, can help properly assess the rising background post Si peak.
Data Analysis Guidance #
Si 2s plasmons can overlap with the S 2p region and render appropriate background simulation difficult in the cases of low S:Si ratio. Often an extrapolated Shirley, or even a quadratic background (If [Si] >>> [S]), can help correctly assess the rising Si emission.
A quadratic background function can help mimic this.
References #
- Spectra recorded by HarwellXPS
- Fantauzzi, M., et al. (2014). “A contribution to the surface characterization of alkali metal sulfates.” Journal of Electron Spectroscopy and Related Phenomena 193: 6-15. Read it online here.
- Fantauzzi, M., et al. (2015). “Exploiting XPS for the identification of sulfides and polysulfides.” RSC advances 5(93): 75953-75963. Read it online here.
- Wilson, K., et al. (2002). “Structure and reactivity of sol–gel sulphonic acid silicas.” Applied Catalysis A: General 228(1-2): 127-133. Read it online here.
- Sun, S., et al. (2006). “Fabrication of gold micro-and nanostructures by photolithographic exposure of thiol-stabilized gold nanoparticles.” Nano letters 6(3): 345-350. Read it online here.
- Isaacs, M. A., et al. (2019). “Unravelling mass transport in hierarchically porous catalysts.” Journal of Materials Chemistry A 7(19): 11814-11825. Read it online here.
- Rabee, A. I., et al. (2017). “Acidity-reactivity relationships in catalytic esterification over ammonium sulfate-derived sulfated zirconia.” Catalysts 7(7): 204. Read it online here.
- Vasquez, R. (1998). “CuSO4 by XPS.” Surface Science Spectra 5(4): 279-284. Read it online here.
