Sulphur

Table 1. S 2p3/2 binding energies compiled from the NIST database [1] and other sources.

Notes: 2p3/2 - 2p1/2 doublet separation = 1.18eV, peaks constrained to a 2:1 area ratio (2p3/2 : 2p1/2), generally one sets both peaks to an equal FWHM for ease of use although in pure samples this may not be the case.

Smart et al. [2] and Pratt et al. [3] give an excellent overview of binding energy ranges for the study of mineral surfaces. These ranges can be used with other sulphur containing systems as well. Of particular interest is the assignment for polysulphides eg. (S4)2- = 162.0-163.0 eV, (S5)2- = 161.9 - 163.2 eV, (Sx)2-) = 163.7 eV. Surface species can also play a role in XPS, especially for in-situ fractured sulphide mineral species [4].

[a] Nesbitt et al. [6] give a value of 162.2 eV for the disulphide in arsenopyrite.
[b] A more detailed look at organic sulphur species can be found here.

In a recent paper from Sarah Harmer's group at Flinders University, synchrotron XPS is used to convincingly elucidate surface 3-coordinate, bulk and surface 4-coordinate and bulk 5-coordinate sulfur in the chalcogenide (Fe,Ni)9S8.  This work shows that sulfide coordination changes can be seen by XPS [7].

A Na2S2O3.5H2O (sodium thiosulphite cooled to -130C during analysis) reference sample gave S 2p3/2 peak positions of 162.1 eV and 168.1 eV for S*SO3 and SS*O3 moieties, respectively.

There is a lot of confusion in the literature when presenting the data for sulphur. Some papers mention S 2p when they really mean S 2p3/2, these are not interchangeable! Please remember to be specific about the exact peak you are referring to.

References:

[1] C.D. Wagner, A.V. Naumkin, A. Kraut-Vass, J.W. Allison, C.J. Powell, J.R.Jr. Rumble, NIST Standard Reference Database 20, Version 3.4 (web version) (http:/srdata.nist.gov/xps/) 2003.
[2] R.St.C. Smart, W.M. Skinner and A.R. Gerson, Surface and Interface Analysis, 28, 101-105, 1999.

[3] A.R. Pratt, I.J. Muir and H.W. Nesbitt, Geochimica et Cosmochimica Acta, 58 (2), 827-841, 1994.

[4] H.W. Nesbitt, M. Scaini, H. Hochst, G.M. Bancroft, A.G. Schaufuss and R. Szargan, American Mineralogist, 85, 850-857, 2000.
[5] A.R. Pratt, H.W. Nesbitt, American Mineralogist, 85, 619-622, 2000.
[6] H.W. Nesbitt, I.J. Muir, A.R. Pratt, Geochimica et Cosmochimica Acta, 59 (9), 1773-1786, 1995.
[7] Z.E. Pettifer, J.S. Quinton, W.M. Skinner and S.L. Harmer, 504, 144458, 2020.