On Fri, Sep 17, 2010 at 10:00 AM,
<ifeffit-request@millenia.cars.aps.anl.gov> wrote:
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Today's Topics:
1. Re: Bkg removal problem (Alfred Hummer)
2. Mathematical expressions for the path parameters in Fitting
(sumitk@barc.gov.in)
3. Re: Mathematical expressions for the path parameters in
Fitting (Shelly Kelly)
4. Re: Mathematical expressions for the path parameters in
Fitting (Brandon Reese)
----------------------------------------------------------------------
Message: 1
Date: Thu, 16 Sep 2010 19:58:53 +0200
From: Alfred Hummer <alfred.hummer@univie.ac.at>
To: ifeffit@millenia.cars.aps.anl.gov
Subject: Re: [Ifeffit] Bkg removal problem
Message-ID: <4C925ADD.90306@univie.ac.at>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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@millenia.cars.aps.anl.gov:
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> Today's Topics:
>
> 1. Re: Bkg removal problem (Bruce Ravel)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 14 Sep 2010 14:07:55 -0400
> From: Bruce Ravel<bravel@bnl.gov>
> To: XAFS Analysis using Ifeffit<ifeffit@millenia.cars.aps.anl.gov>
> Subject: Re: [Ifeffit] Bkg removal problem
> Message-ID:<201009141407.55193.bravel@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@netzero.com
>>
>> On Fri, Sep 10, 2010 at 8:42 AM, Alfred Hummer
>>
>> <alfred.hummer@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
>>>
>>>
>>> _______________________________________________
>>> Ifeffit mailing list
>>> Ifeffit@millenia.cars.aps.anl.gov
>>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>>
>> _______________________________________________
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>> Ifeffit@millenia.cars.aps.anl.gov
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>>
>
------------------------------
Message: 2
Date: Fri, 17 Sep 2010 11:31:34 +0530
From: sumitk@barc.gov.in
To: ifeffit@millenia.cars.aps.anl.gov
Subject: [Ifeffit] Mathematical expressions for the path parameters in
Fitting
Message-ID:
<edb6390523394cc867a1b7e12aa03d81.squirrel@bts.barc.gov.in>
Content-Type: text/plain;charset=UTF-8
Hello,
In EXAFS data modeling carried out by fitting excercise, we develop
mathematical expressions for different path parametrs as functions of a
smaller set of fitting parameters that can be adjusted to achieve to best
fit to the data. I am carrying out EXAFS analysis of Eu(III) sorbed on
different environmentally relevent mineral oxides. In conection of this i
also analysed some reference standard compounds. In developing expression
for different path parameters, though i developed the expressions using my
own understanding and taking help from one of Shelly's tutorial regarding
SnO2 case, i am not confident. Basically SS2, and deltaE expressions
puzzle me.
Could someone help me in understanding basic approach in developing their
expressions(for reference Eu2O3 structure could be taken).
Regards,
Sumit
------------------------------
Message: 3
Date: Fri, 17 Sep 2010 10:40:14 -0500
From: Shelly Kelly <dr.sdkelly@gmail.com>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] Mathematical expressions for the path
parameters in Fitting
Message-ID:
<AANLkTim40RLMwFRFm1JN0becDx7MM7Lthqmw_xu=Jsk-@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Hi Sumit:
There are a lot of different ways to constrain the EXAFS parameters in
a fitting model. Mostly they are determined by physically meaningful
relationships or through trial and error of "what works". I just sent
you my book chapter and you will find detailed discussion on many of
the common constraints in there. Another good place to look is in the
literature to find out what people have done for systems similar to
yours.
HTH,
Shelly
On Fri, Sep 17, 2010 at 1:01 AM, <sumitk@barc.gov.in> wrote:
> Hello,
> In EXAFS data modeling carried out by fitting excercise, we develop
> mathematical expressions for ?different path parametrs as functions of a
> smaller set of fitting parameters that can be adjusted to achieve to best
> fit to the data. I am carrying out EXAFS analysis of Eu(III) sorbed on
> different environmentally relevent mineral oxides. In conection of this i
> also analysed some reference standard compounds. In developing expression
> for different path parameters, though i developed the expressions using my
> own ?understanding and taking help from one of Shelly's tutorial regarding
> SnO2 case, i am not confident. Basically SS2, and deltaE expressions
> puzzle me.
> Could someone help me in understanding basic approach in developing their
> expressions(for reference Eu2O3 structure could be taken).
> Regards,
> Sumit
>
>
>
> _______________________________________________
> Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>
------------------------------
Message: 4
Date: Fri, 17 Sep 2010 10:54:21 -0600
From: Brandon Reese <bjreese@gmail.com>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] Mathematical expressions for the path
parameters in Fitting
Message-ID:
<AANLkTikQG0L=-QWp_EX51XSuOYvN7_JZvESh5o9LSDp6@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hi Shelly,
I am also looking into different ways to constrain my EXAFS fits. If you
wouldn't mind, I would also be very interested in a copy of your book
chapter.
Thanks,
Brandon
On Fri, Sep 17, 2010 at 9:40 AM, Shelly Kelly <dr.sdkelly@gmail.com> wrote:
> Hi Sumit:
>
> There are a lot of different ways to constrain the EXAFS parameters in
> a fitting model. Mostly they are determined by physically meaningful
> relationships or through trial and error of "what works". I just sent
> you my book chapter and you will find detailed discussion on many of
> the common constraints in there. Another good place to look is in the
> literature to find out what people have done for systems similar to
> yours.
>
> HTH,
> Shelly
>
> On Fri, Sep 17, 2010 at 1:01 AM, <sumitk@barc.gov.in> wrote:
> > Hello,
> > In EXAFS data modeling carried out by fitting excercise, we develop
> > mathematical expressions for different path parametrs as functions of a
> > smaller set of fitting parameters that can be adjusted to achieve to best
> > fit to the data. I am carrying out EXAFS analysis of Eu(III) sorbed on
> > different environmentally relevent mineral oxides. In conection of this i
> > also analysed some reference standard compounds. In developing expression
> > for different path parameters, though i developed the expressions using
> my
> > own understanding and taking help from one of Shelly's tutorial
> regarding
> > SnO2 case, i am not confident. Basically SS2, and deltaE expressions
> > puzzle me.
> > Could someone help me in understanding basic approach in developing their
> > expressions(for reference Eu2O3 structure could be taken).
> > Regards,
> > Sumit
> >
> >
> >
> > _______________________________________________
> > Ifeffit mailing list
> > Ifeffit@millenia.cars.aps.anl.gov
> > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
> >
>
> _______________________________________________
> Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov
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