Thanks, My understanding is that he has X-ray data where he went through both the MnL2 and MnL3 edges... (to me it looks kinda like XPS data as opposed to EXAFS spectra)... he wants to simulate what it should look like from Mn of different valences (Mn+2, Mn+3, Mn+4, etc.) so that he can try to determine a ratio within his sample.... if that makes sense. It is a very different use for FEFF than what I'm used to but I'm trying to help him out. When we pulled up his data in Athena it looked very weird since it looked like Athena was expecting it to be over a range of energies applicable for EXAFS. thanks for the input! -Kristine ==============Original message text=============== On Thu, 22 Jan 2004 3:48:54 pm CST Bruce Ravel wrote: On Thursday 22 January 2004 04:28 pm, k-kupiecki@northwestern.edu wrote:
We were also trying to figure out a way to remove the background from his experimental absorption spectra -- can Athena do this (or does Athena only work on EXAFS spectra)? If not, does anyone do this type of thing and have suggestions?
I'm a little confused. Could you be more explicit about what kind of data you are talking about? In general, though, if the problem of removing background from data can be expressed in the terms of the autobk algorithm, that is removing the low frequency Fouirer components and leaving the high frequency ones, then probably Athena will handle is ok. You could always just read the data in and see what 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 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/ ===========End of original message text===========
On Thursday 22 January 2004 04:56 pm, k-kupiecki@northwestern.edu wrote:
When we pulled up his data in Athena it looked very weird since it looked like Athena was expecting it to be over a range of energies applicable for EXAFS.
I presume that what you mean by this is that the grid spacings in the x-axis array are not something consistent with exafs -- i.e. they are not of the order of 1. Possibly, your data is in the form of wavenumbers, i.e. backwards from what Athena expects as well as with spacing != O(1). You could try using a little script or a spreadsheet to change the x-axis array so that each step is of order 1. It need not start at a value in the 1000s. Athena reads, for example, dispersive data taken on a position sensitive detector just fine. In that case, the data starts at 1 and is on a uniform, integer grid. After Athena is done, you could then use a script or a spreadsheet to convert it back to the original x-axis grid. This actually raises an interesting point about a feature that is missing from Athena. Athena gives you no ability to preprocess the x-axis grid (other than automatically detecting and converting from keV to eV). It would be very nice to be able to specify a math expression for converting a data array to an energy grid. That would be useful, for instance, if you wanted to read an array of encoder valuess and use that as your energy array. That sort of generic data preprocessing has long been on Athena's list of things to do. IIRC, Sam's SixPack has a feature like this. Perhaps that and Sam's interface to the Autobk algorithm would do the trick for you. Worth looking into, in any case. 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 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/
participants (2)
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Bruce Ravel -
k-kupiecki＠northwestern.edu