[Ifeffit] Re: Ifeffit Digest, Vol 46, Issue 7

[Bruce Ravel]

On Wednesday 13 December 2006 22:19, Mehdi Ali wrote:
> I have a question what does Rbkg option in athena does. What is its
> physical significance. I am new to exaf data analysis.

There is a ton of information about exafs analysis at http://xafs.org.  In
particular, check out the Tutorials section.  The meaning of Rbkg is covered
with pretty pictures in the first of Shelly Kelly's tutorials around page 30.

In short (and I recommend you look at the figure on page 30 of Shelly's
presentation), Rbkg is the cutoff in Fourier space between the part of the
measured spectrum that is the background and the part that is data.  The
oscillatory chi(k) function has frequencies that are related to inter-atomic
distances.  Frequencies below some value, then, are associated with the
background function.  The spline is adjusted such that the Fourier components
below Rbkg are minimized.

A typical value for Rbkg is about half the near neighbor distance.

HTH
B

-- 
 Bruce Ravel  ---------------------------------------------- bravel at anl.gov

 Molecular Environmental Science Group, Building 203, Room E-165
 MRCAT, Sector 10, Advanced Photon Source, Building 433, Room B007

 Argonne National Laboratory         phone and voice mail: (1) 630 252 5033
 Argonne IL 60439, USA                                fax: (1) 630 252 9793

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