[Ifeffit] Re: Amplitude and the EXAFS equation

Bruce Ravel ravel at phys.washington.edu
Wed Oct 30 10:40:21 CST 2002

Hi all,

Matt mentioned, but didn't expand upon, yet one more important
aspect of the difficult situation of measuring amplitudes in EXAFS.
As he pointed out, all of the effects that Matt, Scott, and I
discussed are *amplitude* effects.  By careful consideration of all
these issues, one may obtain coordination numbers to within 10%.  In
many situations, a sober estimation of uncertainty in coordination may
be quite a bit higher that 10%.

Note, though, that none of these issues are highly correlated with the
phase terms in the EXAFS equation.  Specifically, uncertainty (even
large uncertainty) in amplitude does not mean that you cannot measure
bond lengths precisely.

Even if your coordination numbers are highly uncertain, your delta_R
numbers may have nice, tight error margins.


 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, X24c, U4b
 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/

More information about the Ifeffit mailing list