[Ifeffit] fitting sulphur using standards by Athena

Bruce Ravel bravel at bnl.gov
Tue Feb 14 08:07:45 CST 2012

On Tuesday, February 14, 2012 07:55:54 am 陈娟 wrote:
> As I known, the spectra for standard diluted with BN and non-diluted are
> different. The peak of the non-diluted is low due to self-absorption, as
> shown in the figure below. S1 is non-diluted and s1_10 is diluted sulphur
> to about 3%. For dilution, the position of the peak is also changed.
> Therefore the non-diluted s1 spectra isnot the real spectra of
> dibenzothiophene. The question is what percentage should I dilute the
> standard to get the credible spectra for the standards?and how to explain
> the peak position change? 

Although this sort of thing can be approximated from tables of
absorption coefficients, the advice I usually give to my users is to
prepare a series of samples of diminishing concetrations and measure

Having a good intuition for sample preparation and the effects of poor
sample preparation is always important and even more so for low energy
edges.  The best way to develop that intuition is by doing the
experiment yourself.

> Can I use Athena to counteract the self-absorption and get the
> credible spectra for sdandards?

Yes it can -- in principle.  Doing a good job of self absorption
correction requires a lot of knowledge about your sample and its
matrix -- often more than one has.

The use of the self absorption tool is explained in the Athena
document.  I have also written a lecture on this topic.  Go to 


and download the "selfabs.pdf" file.



 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
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