On 09/06/2016 10:55 AM, Irina Pi wrote:
Thank you for the quick answer. Which range should I have for the EXAFS analysis to be meaningful? Like 200eV above the edge?
I am always uncomfortable when newcomers ask for "rules". Having a rule without understanding when and why it might apply seems counter-productive. Firstly, lets discuss the relation ship between "energy above the edge" and photoelectron wave number. The conversion constant between energy and wavenumber is k = sqrt( ETOK * (E-E0) ) where ETOK is the appropriate combination of fundamental constants (2m_e / hbar^2, where m_e is the mass of the electron and hbar is Planck's constant) about equal to 1 / 3.81. So, 10 inverse Angstroms is about 381 volts above the edge. The extent of the signal in k determines how well you can interpret an EXAFS signal in a quantitative sense. See this page in the Athena manual: http://bruceravel.github.io/demeter/documents/Athena/plot/krange.html Scott Calvin discusses this in his book. There is more information about EXAFS data reduction among the tutorials at http://xafs.org/Tutorials. As Fred and Robert have said, you need "enough" data range to make a useful interpretation of the EXAFS. 200 eV is not a lot -- that will leave you with only a small handful of independent measurements in your data, possibly not even enough to reliably determine a first shell bond length. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Science Group at NSLS-II Building 743, Room 114 Upton NY, 11973 Homepage: http://bruceravel.github.io/home/ Software: https://github.com/bruceravel Demeter: http://bruceravel.github.io/demeter/