[Ifeffit] (Reposted) K-space vs R-spce fitting

Lezama Pacheco, Juan Salvador jlezama at slac.stanford.edu
Fri Sep 10 19:29:11 CDT 2010

Reposting, just notice no line breaks, sorry!
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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