All:

Recently our group was at the APS collecting Pb L(III) spectra on an ID line using quick XAFS. Data was collected from -200 to +800 eV for Pb L(III) at 0.2 eV steps with a count rate of 0.025 seconds. Each scan took about 2.5 minutes to complete. During our measurements we began noting issues with the linearity of scans collected in the extended region of the same sample. After poking around in the data we noticed that Io was not linear throughout the measurement for a portion of the scans. This was not always the true (see Athena project attached to the email, and images attache to the email). I was always under the impression that Io should ideally remain linear throughout the energy region scanned, or at least remain unchanged between replicate scans. We worked with the beamline scientists to try alleviate/fix the issue, but it kept persisting. I realize this is not an IFEFFIT issue, but I was hoping someone might be able to help me understand what was going on and why this was happening? If I have not included enough information for the question please let me know.