On May 7, 2009, at 3:39 PM, Leigh Allen wrote:
I collected at 1.0809A, which was the optimal wavelength for the beam at NSLS-X29. I will model them as MSEs. I guess the better question to ask is if I should be concerned with not having these negative peaks. Will it negatively affect my R-work/R-free if I continue to work with the data that's not been scaled to keep F+/F- separate?
At that wavelength f' is approximately -2 and f'' is 0.6, which are much less than at the Se K edge: http://skuld.bmsc.washington.edu/scatter/data/Se.dat I would expect R/Rfree to improve slightly if you refine against F+/ F-, but if you do this and still see negative peaks, I wouldn't worry about them. (Note: you still need to scale your data, just don't average F+/F- - in HKL2000 clicking the "Anomalous" box in the scaling window is sufficient.) -------------------- Nathaniel Echols Lawrence Berkeley Lab 510-486-5136 [email protected]