Zhaomo, I suspect that you have jumped right into EXAFS. You should really make use of the numerous resources available to get a better handle on data analysis. You would make far better progress in EXAFS than waiting around for answers here. Chris ******************************** Christopher J. Patridge, PhD NRC Post Doctoral Research Associate Naval Research Laboratory Washington, DC 20375 Cell: 315-529-0501 On 1/4/2013 3:48 AM, Zhaomo Tian wrote:
Dear all,
I try to analyze EXAFS data(Cu k-edge was probed) of bare Cu thin film and Cu thin film with CO gas adsorption. However, before the fitting, I found that the first main peak of bare Cu thin film appears at R around 2.2 angstrom, but the nearest neighbor distance of Cu is actually at R around 2.5 angstrom, are there something wrong with my data or is it a normal phenomenon? And when I tried phase correction in Athena or used FEFF calculated 1st path for phase correction in Artemis, the peak became closed to R=2.5 angstrom, which seemed more reasonable. But I guess phase correction is not a necessary process, then what should I do to make the 1st main peak position consistent with the right value?
I also attached other 3 data for CO adsorbed Cu(Cu 1do CO, Cu 2do CO and Cu 5do CO. 1do, 2do and 5do mean that the incident angle of X-ray on sample is 1°, 2° and 5° ), Cu is 300nm thickness thin film deposited on SiO2/Si, and CO was injected through the whole measurement and adsorbed on the Cu surface. Unfortunately, the data for Cu 5do with and without CO are generally the same, I guess this happened because C-Cu, Cu-O or C-O paths are too weak to be observed, major Cu-Cu scattering still dominant even if with CO adsorption, is this right? But Cu 1do CO and Cu 2do CO data are different with bare Cu signal, especially Cu 1do CO, in FT spectrum, it shows a small peak at R around 1.1 angstrom and a shoulder at R around 1.9 angstrom, is it possible for them to stand for C-O and C-Cu path respectively??(I checked C-O and C-Cu distance for CO adsorbed Cu in the reference, both are coincident with such values). Now I have no idea on my situation and come to ask for your he! lp..
Thanks so much!
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On Friday, January 04, 2013 05:48:24 PM Zhaomo Tian wrote:
I try to analyze EXAFS data(Cu k-edge was probed) of bare Cu thin film and Cu thin film with CO gas adsorption. However, before the fitting, I found that the first main peak of bare Cu thin film appears at R around 2.2 angstrom, but the nearest neighbor distance of Cu is actually at R around 2.5 angstrom, are there something wrong with my data or is it a normal phenomenon? And when I tried phase correction in Athena or used FEFF calculated 1st path for phase correction in Artemis, the peak became closed to R=2.5 angstrom, which seemed more reasonable. But I guess phase correction is not a necessary process, then what should I do to make the 1st main peak position consistent with the right value?
Zhaomo, I tend to agree with Chris. You seem to be asking questions that are answered in great detail and by many people in places that are easily found on the web. You should spend some quelity time following the links at http://www.xafs.org/Tutorials A google search of "exafs phase shift" turned up plenty of useful links right on the first page, including this discussion from 2004 from this very mailing list: http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2004-July/005768.html B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 Homepage: http://xafs.org/BruceRavel Software: https://github.com/bruceravel
participants (3)
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Bruce Ravel -
Christopher Patridge -
Zhaomo Tian