[Ifeffit] Bkg removal problem

Alfred Hummer alfred.hummer at univie.ac.at
Thu Sep 16 12:58:53 CDT 2010

Thx for the detailed answer. Helped me a lot.
Also tested it with other programs using smoothed splines, leading to 
similar results.

And you are right, I don't expect a peak at about 1A in the FT. The 
first peak at 1.5A in the FT should represent a mixed 1st shell of 3O/3N 
atoms at about 2A distance.

best regards Alfred

Am 15.09.2010 19:00, schrieb ifeffit-request at millenia.cars.aps.anl.gov:
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>     1. Re: Bkg removal problem (Bruce Ravel)
> ----------------------------------------------------------------------
> Message: 1
> Date: Tue, 14 Sep 2010 14:07:55 -0400
> From: Bruce Ravel<bravel at bnl.gov>
> To: XAFS Analysis using Ifeffit<ifeffit at millenia.cars.aps.anl.gov>
> Subject: Re: [Ifeffit] Bkg removal problem
> Message-ID:<201009141407.55193.bravel at bnl.gov>
> Content-Type: Text/Plain;  charset="iso-8859-1"
> Alfred,
> I certainly encourage you to look at Shelly's book chapter. It's very
> useful.
> The question you ask is one that we hear frequently on this mailing
> list.  I don't mean anything bad by saying that -- in fact, it's an
> excellent question that every practitioner of XAS needs to come to
> terms with early on in his or her XAS career.  Indeed, I am pleased
> that you are insightful enough to recognize your confusion and wise
> enough to ask for help.
> That said, I am a bit weary of answering questions about Rbkg on the
> mailing list.  Yours ain't the first! ;-)
> Rather than answering here, I decided to write up a wiki page on the
> topic.  That way, I'll have something to point to the next time
> someone asks about Rbkg.
> Here it is:
>    http://xafs.org/TheoryAnalysis/BackgroundRemovalWithAutobk
> Hope it helps,
> B
> On Friday 10 September 2010 10:25:50 am Shelly Kelly wrote:
>> Hi Alfred:
>> You should take a look at my book chapter. I go through a lot of
>> details on how to remove the background. If you want a copy just send
>> me an email directly and I'll send you a pdf.
>> Cheers,
>> Shelly
>> exafs at netzero.com
>> On Fri, Sep 10, 2010 at 8:42 AM, Alfred Hummer
>> <alfred.hummer at univie.ac.at>  wrote:
>>> Hello,
>>> Currently I am working on a Ga XAS spectrum.
>>> I'm trying to extract the EXAFS data but I'm not sure if the background
>>> function is right, or how to set the right values.
>>> I played around with different setting for kmin and Rbkg.
>>> So far I know that Rbkg defines the cutoff for the bkg frequencies in the
>>> FT optimization and setting it to high leads to loss in information, as
>>> more high frequencies are included in the bkg.
>>> I also read that it is advisable to exclude strong white lines from the
>>> spline range (increasing kmin?). Would this a strategy in my case?
>>> I attached the project file.
>>> Maybe someone has a clue. The more I tried the bigger my uncertainty.
>>> best regards
>>> Alfred
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