[Ifeffit] weights data processing

Bruce Ravel ravel at phys.washington.edu
Mon Jul 26 08:06:13 CDT 2004


I wanted to add a coupe more comments on Stafano's questions regarding
k-weighting in Athena and Artemis.

Regarding k-weights in Athena: Athena's default for the k-weight using
background removal is 1.  I chose that pretty much for the reason that
Scott gave.  Ifeffit's default is 0, so this is a situation where
Athena and Ifeffit have different default behavior.  As for the
insensitivity of your data to this value, I would say that it is
situational.  Sometimes, the k-weight can have a dramatic influence on
the background removal.  Stability of the background removal and its
impact on subsequent analysis has been a frequent topic of discussion
in this forum.  k-weight, then, is yet another parameter that can
impact the stability of your spline.

Rgearding k-weights in Artemis:  Scott and Matt covered the "why" of
k-weights.  How k-weights are actually used by Artemis when fitting
and plotting is a bit complicated.  See section 5.8.4 of the
(incomplete) artemis document for a detailed explanation of how
k-weighting is used in Artemis.
   http://leonardo.phys.washington.edu/~ravel/software/exafs/doc/artemis.pdf

B

-- 
 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
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 Naval Research Laboratory                          phone: (1) 202 767 2268
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 NRL Synchrotron Radiation Consortium (NRL-SRC)
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 National Synchrotron Light Source
 Brookhaven National Laboratory, Upton, NY 11973

 My homepage:    http://feff.phys.washington.edu/~ravel 
 EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/




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