CS> First of all, thanks! I just put athena and ifeffit on our CS> beamline computer at MR-CAT for our users to assess data as they CS> take it. It proved to be very easy for the students and newbies CS> to figure out. That's just splendid. I am very pleased and quite flattered by the praise. Thanks! If there are features of the program the MR-CAT and its users would like to see, please let me know. CS> The question that I have is how does IFEFFIT handle continuous CS> scan data, where the point spacing is almost but not quite CS> uniform in energy all the way through the scan. Well, I am sure that Matt will correct me if I am wrong, but I think I can answer this. mu(E) data is almost never on an even grid, regardless of how it is measured. The background function is evaluated on the energy array of the data using knots that are evenly spaced in wavenumber. When the background is removed, chi(E) -- which is on the original energy grid -- is interpolated onto an even grid in k-space. CS> I have noticed the error of misordered data which can often show CS> up in the continuous scans. We will probably try to fix that CS> ourselves. Misordered data is handled in a sensible manner in recent versions of athena. It may even be handled correctly ;-) CS> What is done with the high density data when converting to CS> k-space? Do you rebin (averaging both E and mu data) or do you CS> use a smoothing fit to take advantage of the statistics present CS> in the excess data points, or do you just interpolate and throw CS> away the extra statistics? I think I answered this above. I suppose you might say that ifeffit "interpolates and throws", but even that depends on what advantage you claim to be getting by measuring on a finer grid. There are physical limits to the resolution, so in that sense a finer grid does not help. However, mesuring for one second per point on, say, a 0.25 eV grid is similar in a counting statistics sense to two measurements of one second per point on a 0.5 eV grid. That counting statistics improvement is not lost in the interpolation of chi(E) to chi(k). Or, perhaps, I'm missing your point entirely... That happens ;-) 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/