And yet, the documentation for the CORRECTIONS keyword says:

"The real energy shift vrcorr moves E0 in the final \chi(k) and the imaginary energy shift vicorr adds broadening to the result. The real energy shift is useful to correct the error in FEFF's Fermi level estimate and the imaginary part can be used to correct for experimental resolution or errors in the core-hole lifetime."

And a couple of sentences later:

"The imaginary energy is typically used to correct for instrument broadening or as a correction to the mean free path calculated by feff."

Perhaps the document should be updated to explain more clearly what CORRECTIONS actually does. Thank you Bruce. I will try to clear up the documentation. Let me state more clearly how these two cards can be used to change the broadening of the spectrum. In the EXCHANGE card, the user can use negative values to offset the core hole broadening. The CORRECTIONS card can only be used to add to the total (previous) broadening, which is given by the half width at half max, Gamma_CH/2 + vi, where vi is the broadening from the EXCHANGE card and Gamma_CH is the core hole broadening. The benefit of using the CORRECTIONS card is that it is very fast since you can skip the matrix inversion for the FMS calculation. Thus a good way to use the two cards together is to reduce the broadening via EXCHANGE by a bit too much (use an overestimate as a first try), then use the CORRECTIONS card to fine tune the broadening. Cheers, Josh correctly. 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

My homepage: http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/

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End of Ifeffit Digest, Vol 76, Issue 8 **************************************