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. B -- Bruce Ravel ----------------------------------- ravel@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/