[Ifeffit] Estimation of S02
Hiroshi Oji
oji-h at spring8.or.jp
Thu Oct 9 06:27:58 CDT 2008
Hi Leandro,
Thank you for telling me the reference relating to my question. I'll
take a look at them. It will take a little bit long time to understand
these references, but I hope I will be able to find the good way to
determine S02 in my case. My question seems to be FAQ, so I should
check throughly the archive of the mailing list at first. I am sorry
for that.
Thanks again for your cooporation,
best regards,
Hiroshi
Leandro Araujo wrote:
> Hi Hiroshi,
>
> questions very similar to yours have already been asked in the mailing
> list and I still think the best answers are those available at:
> 1- Sections 4,8, 11-13 at http://cars9.uchicago.edu/iffwiki/FAQ/FeffitModeling
> 2- This previous thread from the mailing list:
> http://www.mail-archive.com/ifeffit@millenia.cars.aps.anl.gov/msg00182.html
> 3- This one as well:
> http://www.mail-archive.com/ifeffit@millenia.cars.aps.anl.gov/msg00368.html
>
> As Bruce, Matt, Scott and many others have said, there is no "one fits
> all" solution, so I suggest you start from the considerations found in
> the links above to select the best approach to your specific system.
> And take a good look at other previous threads in the mailing list -
> seek and thou shall find...
>
> As far as correlations are concerned, "That is the nature of the exafs
> fitting problem. A correlation of 0.8 for either of those pairs
> (amp/MSRD and E0/dr) is quite common." (quoting
> http://www.mail-archive.com/ifeffit@millenia.cars.aps.anl.gov/msg00523.html).
> Excellent pieces of advice on how to handle this problem can be found
> in the links mentioned above and the best I can do is direct you to
> them. Sorry if this is not the straight answer you were hoping for.
>
> Regarding your Athena project, I suggest tweaking the position of E0
> and the k and R windows according to the advice provided in the links
> above. The experimental data looks nice and clean up to k~14.5 A-1.
>
> Best of luck,
> Leandro
>
>
>
> 2008/10/9 Hiroshi Oji <oji-h at spring8.or.jp>:
>> Hi Matthias and Leandro,
>>
>> Thank you very much for your reply.
>>
>> I checked the DW-factor (MSRD) and found it also varies significantly
>> depending on Fit k-weight as follows.
>>
>> kw amp ss
>> 1 0.8145660 +/- 0.0486470 0.0073230 +/- 0.0005240
>> 2 0.9230700 +/- 0.0673820 0.0082070 +/- 0.0005070
>> 3 1.0439100 +/- 0.0854950 0.0089560 +/- 0.0005100
>> 1,2,3 0.9081570 +/- 0.0722180 0.0081660 +/- 0.0005920
>>
>> The correation between these variables reported by Artemis are very
>> strong, especially for kw=3.
>>
>> kw corration between amp and ss
>> 1 0.8469
>> 2 0.8992
>> 3 0.9543
>> 1,2,3 0.8543
>>
>> So, it seems to me that the amps obtaied by kw=1 and 1,2,3 with less
>> degree are more reliable.
>>
>> If the DW-factor is fixed, for example, to ss = 0.008, the variation of
>> amp become small as follows,
>>
>> kw amp ss
>> 1 0.8674610 +/- 0.0296350 0.008 (fixed)
>> 2 0.8984650 +/- 0.0260200 0.008 (fixed)
>> 3 0.8998030 +/- 0.0327720 0.008 (fixed)
>> 1,2,3 0.8898850 +/- 0.0325530 0.008 (fixed)
>>
>> But I don't know how to determine the appropriate DW-factor. Could you
>> give me advice or comment on this problem?
>>
>> By the way, I attached the Athena project file of Zr-foil which I
>> analyzed. I am glad if you kindly check it.
>>
>> Thank you for your coopration in advance,
>> Best regards,
>>
>> Hiroshi
>>
>> Matthias Bauer wrote:
>>> hi hiroshi,
>>> i did not have a look at the attached project, but what paramteres did
>>> you vary? even if you use different k-weightings, there is still the
>>> strong correlation of N,S02 and the Debye-Waller like factor. so as long
>>> as you do not keep two of these three on a certain value, your S02 might
>>> vary to some extend, which will be more significant for shells beyond
>>> the first one. anyway, it would be a great thing to hear some comment on
>>> a S02 value higher than one, which is by definition of S02 not possible.
>>> in most analyses the electron mean free path is not iterated, which can
>>> be an explanation of unphysical values of S02, but than it should be
>>> considered as a "net" factor accounting for both intrinsic and extrinsic
>>> losses. am i right?
>>> best regards
>>> matthias
>>>
>>> Leandro Araujo wrote:
>>>> Hi Hiroshi,
>>>>
>>>> your variation in SO2 does sound a bit too big, so I'll try to help
>>>> adding my 50c and hopefully more people will jump in.
>>>> It seems to me that your window in k-space is going a bit lower than
>>>> it should - you seem to be including signal from the xanes region in
>>>> your fit and that is not a good thing.
>>>> I did some really quick fits using your project and just changing the
>>>> window from k ~ 2-14 to k ~ 4.8-14. Then I got the following values:
>>>> kw amp
>>>> 1 1.0065350+/-0.0788250
>>>> 2 1.0359800+/-0.0888140
>>>> 3 1.0749950+/-0.0946640
>>>> 1-3 1.0322490+/-0.0866650
>>>> That seems a more reasonable variation to me. But maybe I'm being
>>>> tricked by the fact that you have a split first shell and the MSRDs
>>>> are not supposed to be very similar...
>>>> I would also suggest opening the r-window to the right side a little
>>>> bit. (By the way, that "bump" in the FT at ~ 1 Angstrom seems
>>>> unexpected for a Zr foil. Maybe check the background removal in
>>>> Athena?)
>>>>
>>>> The above comments obviously do not address the fundamental questions
>>>> "why does SO2 change with k-weighting?" and "what's the best way to
>>>> determine SO2?". This was intentional, since much better qualified
>>>> people have previously written about it.
>>>> My guess is that you will find something if you search previous
>>>> threads in this mailing list. I would also suggest you check these
>>>> sites:
>>>> http://xafs.org/Tutorials
>>>> http://cars9.uchicago.edu/iffwiki/FAQ/FeffitModeling
>>>>
>>>> Hope this helps,
>>>> Leandro
>>>>
>>>>
>>>> 2008/10/7 Hiroshi Oji <oji-h at spring8.or.jp>:
>>>>
>>>>> Dear all,
>>>>>
>>>>> Could you give me some advice on estimating the intrinsic loss factor (S02)?
>>>>>
>>>>> I am trying to estimate the S02 value in the curve-fitting analysis for
>>>>> Zr K-edge EXAFS.
>>>>>
>>>>> To do this, I did the curve-fitting analysis on the first shell of
>>>>> Fourier transform of Zr-K EXAFS of Zr-foil by Artemis. However, there
>>>>> was a marked difference between the amps obtained by the fitting,
>>>>> depending on the "Fit k-weights" as follows.
>>>>>
>>>>> kw amp
>>>>> 1 0.8145660 +/- 0.0486470
>>>>> 2 0.9230700 +/- 0.0673820
>>>>> 3 1.0439100 +/- 0.0854950
>>>>> 1,2,3 0.9081570 +/- 0.0722180
>>>>>
>>>>> Is this a usual thing? I can't find the reasonable explanation why S02
>>>>> depends on "Fit k-weights".
>>>>>
>>>>> I attached the Artemis project file.
>>>>>
>>>>> Thank you in advance for your cooperation.
>>>>>
>>>>> Hiroshi Oji
>>>>>
>>>>> =========================================================
>>>>> Hiroshi Oji, Dr.
>>>>> Industrial Application Division
>>>>> Japan Synchrotron Radiation Research Institute (JASRI)
>>>>> 1-1-1 Kouto, Sayo-cho
>>>>> Sayo-gun, Hyogo 679-5198
>>>>> JAPAN
>>>>> E-mail oji-h at spring8.co.jp
>>>>> =========================================================
>>>>>
>>>>> _______________________________________________
>>>>> Ifeffit mailing list
>>>>> Ifeffit at millenia.cars.aps.anl.gov
>>>>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>>>>>
>>>>>
>>>>>
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>>
>> --
>> =========================================================
>> 陰地 宏
>> （財）高輝度光科学研究センター（JASRI）
>> 産業利用推進室
>> 〒679-5198兵庫県佐用郡佐用町光都1-1-1
>> TEL(PHS): 0791-58-0802-3713
>> または 0791-58-0803-3713
>> FAX: 0791-58-0830
>> E-mail: oji-h at spring8.or.jp
>>
>> Hiroshi Oji, Dr.
>> Industrial Application Division
>> Japan Synchrotron Radiation Research Institute (JASRI)
>> 1-1-1 Kouto, Sayo-cho
>> Sayo-gun, Hyogo 679-5198
>> JAPAN
>> E-mail oji-h at spring8.co.jp
>> =========================================================
>>
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>>
>>
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--
=========================================================
陰地 宏
（財）高輝度光科学研究センター（JASRI）
産業利用推進室
〒679-5198兵庫県佐用郡佐用町光都1-1-1
TEL(PHS): 0791-58-0802-3713
または 0791-58-0803-3713
FAX: 0791-58-0830
E-mail: oji-h at spring8.or.jp
Hiroshi Oji, Dr.
Industrial Application Division
Japan Synchrotron Radiation Research Institute (JASRI)
1-1-1 Kouto, Sayo-cho
Sayo-gun, Hyogo 679-5198
JAPAN
E-mail oji-h at spring8.co.jp
=========================================================
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