[Ifeffit] How to do with diffraction peak

Bruce Ravel bravel at bnl.gov
Wed Dec 12 17:06:05 CST 2012

On Wednesday, December 12, 2012 03:00:41 PM Matthew Marcus wrote:
> Hmm.  Another possible way to do it is to delete the bad data points and
> then do a "slow" FT, which would be a fit of  the data, at the points given
> with no interpolation, to a sum of sines and cosines.  This would have the
> nice feature of using the data as it is and ignoring the bad
> stuff.  Filtering would involve multiplying  the sines and cosines by some
> window function (in R space) and evaluating them *at the given k-points*,
> not on a regular grid.  This of course means that evaluating FEFF paths and
> the like is likely to be slow because you don't get to use recursion
> relations to evaluate sin(2*R*k(i)+delta) as you would if k(i) are
> uniformly tabulated.  Now that computers are a bazillion times faster than
> they were when EXAFS analysis traditions were established, maybe that's the
> way to go.  What do you think?

I think data should be measured correctly in the first place if at all
possible!  ;)

That said, your suggestion seems completely valid to me.  And, just to
be clear, it's completely impossible with Ifeffit.  Larch, on the
other hand....



 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

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