Sulfur Peak Shifts

[alerner]

One additional possibility is that EPMA analysis induced redox changes in the S in glasses, so that you have an evolving peak position during measurement to some more intermediate state.

S photo-oxidation from S2- was observed by Wallace and Carmichael 1994 and Rowe et al 2007. It is less clear what happens if you have originally S6+ in glasses, as perhaps a photoreduction may occur as in X-ray synchrotron measurements (Wilke et al 2008). The integrated results of EPMA induced beam damage might be S transforming to some intermediate valence charge between the S6+ and S2-. It would be interesting to see time dependent measurements for each of these peak positions during the course of analysis, to track any peak decreases and growth over time.