[Ifeffit] Normalization in Athena

[Bruce Ravel]

It is a little hard to evaluate your results, Lisa, without an
example.  It may help to attach a small project file which
demonstrates your question.

Without an actual example, I would have to guess that the bottom line
is an odd choice of parameters.  This page from the document might be
helpful:

http://cars9.uchicago.edu/~ravel/software/doc/Athena/html/bkg/norm.html

B


On Monday 26 October 2009 10:27:28 am Kropf, Arthur Jeremy wrote:
> Shelly,
>
> I agree that Athena applies its (her) algorithm correctly.  Whether that
> algorithm is correct may be a matter of opinion.  The apparent
> discrepency Lisa sees is due to Athena's algorithm:
>
> i.e., fit preedge line, fit postedge function to normalization range,
> extrapolate both functions to edge energy to find edge step.
>
> Another option would be to fit predge line and subtract it.  After that,
> fit the post edge normalization range.
>
> With Athena, if there is a non-zero slope to the preedge line and you
> choose norm order 1, you get Lisa's result.  With normalization order 2
> or 3, the results should either be the same, or at least, much closer.
>
> Jeremy
>
> > -----Original Message-----
> > From: ifeffit-bounces at millenia.cars.aps.anl.gov
> > [mailto:ifeffit-bounces at millenia.cars.aps.anl.gov] On Behalf
> > Of Kelly, Shelly
> > Sent: Monday, October 26, 2009 9:08 AM
> > To: XAFS Analysis using Ifeffit
> > Subject: Re: [Ifeffit] Normalization in Athena
> >
> > Hi Lisa,
> >
> > Be sure that Athena has been rigorously tested and she does
> > know how to normalize data. It is much more likely that the
> > default values are not the "best" ones for your data.
> >
> > My book chapter goes over how Athena normalizes data in
> > detail.  If you send me your email address I'll send you a
> > copy. In particular see figure 14-16.
> >
> > Cheers,
> > Shelly
> > dr.sdkelly at gmail.com
> >
> > > -----Original Message-----
> > > From: ifeffit-bounces at millenia.cars.aps.anl.gov [mailto:ifeffit-
> > > bounces at millenia.cars.aps.anl.gov] On Behalf Of Gudrun Bovenkamp
> > > Sent: Monday, October 26, 2009 8:42 AM
> > > To: ifeffit at millenia.cars.aps.anl.gov
> > > Subject: [Ifeffit] Normalization in Athena
> > >
> > > Hey everybody,
> > >
> > > while I try to figure what effect normalization has on Linear
> > > combination fitting in my lead L3 edge XANES system, I came accross
> > > this problem:
> > > Athena does not normalize correctly:
> > >
> > > Normalization in Athena (post-edge): using 1.order
> >
> > normalization, no
> >
> > > flattening (which in this case is irrelevant anyway),
> >
> > points +199 eV
> >
> > > and +200 eV above E0.
> > >
> > > Normalization in Origin (post-edge): using point 13235 eV (+200 eV
> > > above E0); dividing the spectrum column by that value.
> > >
> > > See the two examples in the attachment.
> > >
> > > In both examples the normalized spectrum imported from
> >
> > Athena does not
> >
> > > have the norm value of 1 at 13235 eV. Why is that? The
> >
> > offset is also
> >
> > > not the same for every spectrum. That undoes the normalization
> > > routine.
> > >
> > > Greetings,
> > > Lisa
> >
> > _______________________________________________
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>
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-- 

 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

 My homepage:    http://xafs.org/BruceRavel
 EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/