Hi Hashem You can copy-paste the respective EXAFS data in Athena and compare the backtransforms over the first shell, the first+second shell, the second shell. By comparison of the backtransforms with each other and with the measured EXAFS, you can see where the second-shell contribution has its origin in k-space (note that the backtransform is not corrected for the window function). For instance, if the second-shell signal adds to the spectrum in the low-k range (where noise should not be a problem), it is likely real and might result, e.g., from multiple scattering among first-shell O atoms. If the second-shell signal in the backtransform mainly contributes in the high-k range (where noise or glitches may be a problem), you may be able to see whether it falls together with obvious artefacts (such as glitches), or whether the backtransform matches spectral features that you consider to be real. Andreas ----------------------------------------------- Andreas Voegelin, PhD Soil Chemistry Group Inst. of Biogeochemistry and Pollutant Dynamics Dept. of Environmental Sciences ETH Zurich Universitätstrasse 16, CHN F24 CH-8092 Zürich, Switzerland Phone: +41 44 633 61 47 Fax: +41 44 633 11 18 E-Mail: voegelin@env.ethz.ch www: http://www.ibp.ethz.ch/people/andreavo
-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of mstiet2@lsu.edu Sent: Mittwoch, 14. Januar 2009 14:12 To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] distinguishing between actual shells and artifacts
Dear all,
I am currently fitting first and second shells with Zn-O and Zn-Zn paths,respectively. I get second shell features that could be fit quite well, but I am not certain if they are actually second shell features or possibly artifacts. For some samples I get second shell features that I know should not be present. What criteria would you use to distinguish between artifacts and actual shells?
Your assistance is appreciated.
Hashem Stietiya
Louisiana State University