[Ifeffit] K-space vs R-spce fitting

Lezama Pacheco, Juan Salvador jlezama at slac.stanford.edu
Fri Sep 10 19:25:35 CDT 2010

Dear All:
         First of all, nicely done you guys! This is indeed a set great of tools the community really appreciates it and I have been putting into heavy use. I have and issue though that has been making me scratch my head from time to time. I've been trying to figure out the feature of k-space and R-space fitting "relationship" for Ifeffit. I usually work out my fits in k-space although I have to admit that R-space fitting in combined approach will definitely be valuable. Now, as I am trying to work some data for Uranium (namely uranyl acetate standard) I am a little bit confused on the real independency of k-space and R-space fitting. This comes from the fact that even if I specified the fitting range in k (fitting in k space), the dk value seems to have an effect in the current fit values (changing as large as 15%).  I understand the issue if the actual fitting range is then (kmin-dk/2,kmax+dk/2) but is this the case? Then what is the real relationship-independency between k-space and R-space fitting? For q-space that is of course another story. For the record I am using ixafs 1.2 on Mac OS X 10.5.8. Perl distribution seems to crash "unexpectedly"  every time I tried the new 3.0.2, but that is another story in another thread...

Thanks so much again
Juan S Lezama

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