[Ifeffit] copper 1st shell coordination number

[Sven L. M. Schroeder]

Dear Zhaomo Tian

 

Yes, there’s a high likelihood that you have a strong self-absorption effect in your fluorescence-yield spectrum. Perhaps compare your spectrum to a Cu foil transmission spectrum as well. Pay attention particularly to the XANES distortions as you go over the ionisation threshold (edge step): features below the edge should have exaggerated amplitudes and features above the edge should have reduced amplitudes. The EXAFS amplitudes should be, at least in a first approximation, reduced by a constant factor, which is what your 1st shell fit seems to confirm. The pre-edge background probably curves upwards ‘too early’ as well, i.e., at lower photon energies compared the transmission spectrum.

 

The strength of the self-absorption effect depends on the X-ray incidence angle relative to your Cu film plane and the angle at which your detector was placed: maximum self-absorption for  grazing incidence/normal detection, minimum for normal incidence/grazing detection.

 

Best wishes

 

Sven

 

--

Sven L.M. Schroeder ( <mailto:s.schroeder at manchester.ac.uk> mailto:s.schroeder at manchester.ac.uk)

 

Professor of Applied Physical Chemistry

School of Chemical Engineering and Analytical Science (CEAS)

The University of Manchester, Manchester M13 9PL, United Kingdom

 

 <http://www.slmslab.info/> http://www.slmslab.info

 

Also at:

School of Chemistry, The University of Manchester, Manchester M13 9PL, United Kingdom

 

Tel +44 (161) 306 4502

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From: ifeffit-bounces at millenia.cars.aps.anl.gov [mailto:ifeffit-bounces at millenia.cars.aps.anl.gov] On Behalf Of Zhaomo Tian
Sent: 02 January 2013 05:58
To: ifeffit
Subject: [Ifeffit] copper 1st shell coordination number

 

Dear all, 

Thanks for your answer,Scott Calvin! 

I guess the value of sigma2 is normal, which is 0.0075. 
But your suggestion about the existing of modest degree of oxidation or other impurities is possible, I will think over it ^^ 

Actually this morning I improved this situation and got a reasonable CN value by trying self absorption correction to my data in Athena ( because I used fluorescence measurement). I think it is because the amplitude of my data increased after self absorption correction, so the CN of 1st shell also increased from around 8 to around12, which is more reasonable. So I really want to know if this self absorption correction really makes sense, or it might be just an accident?? 

Thanks a lot~ 

  <http://mail.postech.ac.kr/mail/PutAck.jsp?ack_args=c2VudF9maWxlPXpoYW9tbzE5ODlAcG9zdGVjaC5hYy5rci8uU2VudC8xMzU3MTA2MjgyMDY1Ljc1MzMucG9zdGVjaCZzZW5kX2RhdGU9MjAxMzAxMDIxNDU4MDImc3ViamVjdD1jb3BwZXIgMXN0IHNoZWxsIGNvb3JkaW5hdGlvbiBudW1iZXI=&to_email=ifeffit@millenia.cars.aps.anl.gov_____________________________________________________________________________________________________________________> 

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