[Ifeffit] phase corrections and saving files

Bruce Ravel ravel at phys.washington.edu
Tue Nov 25 16:12:23 CST 2003


Hi folks,

I have received a few questions recently on the topic of saving data
to column data files after doing a phase corrected Fourier transform.
Both Athena and Artemis will do this.  Let me explain how it works.

** In Athena, when you save chi(R) as a column data file for the
   current group it will save the phase corrected chi(R) if the button
   for central atom phase corrections is checked for that group.

** In Artemis, you can save chi(R) for the data, the fit, or any part
   of the fit.  If a path has been chosen for the phase correction on
   the data page, then the Fourier transform will be done using that
   path's phase correction before writing out chi(R).

** Thus the rule for both programs is simple.  If you select a phase
   correction, it will be applied before writing out chi(R).

** For both programs, chi(q) will likewise be written out with the
   phase correction is the phase correction is chosen.  That is, if
   the phase correction is chosen, it will be applied to the forward
   transform and the backward transform will be done on that spectrum.

** Neither program writes out a phase corrected chi(k).

** Athena uses a central atom phase correction and no scattering atom
   correction.  Artemis uses both a central and scattering atom phase
   correction, but only that of the path selected for the correction.
   The fit in Artemis is *always* done using the non-phase-corrected
   data and the non-phase-corrected feffNNNN.dat files.

** There was a recent discussion on the mailing list about doing phase
   *and* amplitude corrections.  Neither Athena nor Artemis does that
   at this time.
   
If you observe a situation where either program does not behave as
advertised, let me know so I can fix it for the next release.

Regards,
B


-- 
 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
 Code 6134, Building 3, Room 222
 Naval Research Laboratory                          phone: (1) 202 767 5947
 Washington DC 20375, USA                             fax: (1) 202 767 1697

 NRL Synchrotron Radiation Consortium (NRL-SRC)
 Beamlines X11a, X11b, X23b
 National Synchrotron Light Source
 Brookhaven National Laboratory, Upton, NY 11973

 My homepage:    http://feff.phys.washington.edu/~ravel 
 EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/



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