Chemical Sensitivity of the Sulfur K-Edge X-ray Absorption Spectra of Organic Disulfides.

Sulfur K-edge X-ray absorption spectroscopy increasingly is used as a tool to provide speciation information about the sulfur chemical form in complex samples, with applications ranging from fossil fuels to soil science to health research. As part of an ongoing program of systematic investigations of the factors that affect the variability of sulfur K near-edge spectra, we have examined the X-ray absorption spectra of a series of organic symmetric disulfide compounds. We have used polarized sulfur K-edge spectra of single crystals of dibenzyl disulfide to confirm the assignments of the major transitions in the spectrum as 1s → (S-S)σ* and 1s → (S-C)σ*. We also have examined the solution spectra of an extended series of disulfides and show that the spectra change in a systematic and predictable manner with the nature of the external group.