Hi Matt,
Can you get decent results with a lower Rbkg/Rmin? No, I can not. 1.5A is around the minimum value in Chi(R) magnitude where the first peak can be separated from the others. However, the peak is a result of superposition of background, oxygen path and also the alloy structure.
MN> I think I don't understand this. What are the "others" that the MN> first peak can't be separated from?? Sorry for the confusion that I have introduced. I am doing two-data set simultaneous fit (Bruce already mentioned that in the list) where the two absorbers are Ru and Pt atoms The model structure looks like this: 1. Ru data FEFF0(Ru-Ru):feff0001 FEFF1(Ru-Pt):feff0001 FEFF2(Ru-O):feff0001 2. Pt data FEFF3(Pt-Pt):feff0001 FEFF4(Pt-Ru):feff0001 I was talking about the first part of the model that is related to Ru data. What I meant was that around 1.0-1.5A I saw a peak. According to the model that peak was a result of overlap of background and contributions from different scatterers, such that I could not say that the peak was primarily because of oxygen or any other scatterer. I think the above was what you described as:
'first shell peak', which is sometimes difficult to define for the asymmetric peak common with short metal-oxygen distances
Now if I set rmin=1.5A, the peak is not included in the R-range(it is below rmin). At lower values of rmin a part of the peak is in the range. That could be the reason why I was unable to get decent results with lower rmin. Stanislav