Sulfur 1s NEXAFS spectroscopy is sensitive to sulfur speciation; however, the overlapping energy position of the white line in the spectra of thiols and disulfides can be problematic for speciation. We have acquired highly resolved sulfur 1s NEXAFS spectra of a group of disulfides with aliphatic and unsaturated ligand groups. Spectral transitions were assigned by the aid of Improved Virtual Orbital (IVO) ab initio calculations. These results confirm how molecular symmetry and the ligand group can affect the NEXAFS spectra, and show how the NEXAFS spectra of thiols and disulfides can be used for chemical speciation. (C) 2013 Elsevier B.V. All rights reserved.