7 Jul
2003
7 Jul
'03
1:03 p.m.
On Friday 04 July 2003 02:48 am, SCHLEGEL Michel 177447 wrote: > I think an evaluation of the spectrum noise may be obtained > from the FT contributions peaking at high 'distances' (e.g., > > 10Å). Hence, with a correct script, we should be able to: > - extract chi(k) functions from individual XAS spectra > - perform FTs for these spectra, > - perform inverse FT on the spectra over a given limit, and > calculate s from that, > - usecalculated s values to sum weight-average individual > XAS spectra. > > As I'm a very lousy IFEFFIT user (means that I've stopped > short from hitting buttons on Athena and Artemis), I would > humbly ask Bruce if there's any chance to see such a methodology > implemented on Athena one of these days (not in a hurry, though) The short answer is yes. Currently Athena sets the noise to 1 for all scans involved in the merge. However, Ifeffit offers the very handy chi_noise function, which computes the noise in a manner similar to what Michel suggests. (In fact, it computes the average of the chi(R) spectrum between 15 and 25 Å.) It would be simple matter to weight each spectrum by that number and to give the user the option of choosing how to do the weighting. I'll put it on my list of things to do, which seems to grow faster than I can shrink it! Thanks, 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/