[Ifeffit] Very large exafs amplitude in collected data - cause unknown
bravel at bnl.gov
Tue Jun 4 09:00:39 CDT 2013
On 06/04/2013 12:25 AM, Jason F. Alvino wrote:
> We have collected fluorescence data of PPh3 protected Au nanoparticles
> supported on an anatase surface at the Au L3 edge, which provides some
> decent looking exafs and seems to fit a bulk gold model rather well (there
> seems to be agglomeration on the surface, even with our low loadings).
> We have tried to fit the data using both XFIT and EXAFSPAK, but the strange
> thing is that the exafs oscillations have a huge amplitude, up to 80 in
> some cases. Because of this, the only way to fit the data while
> maintaining sensible Debye-Waller factors is to allow SO2 to become quite
> large, or to allow the coordination numbers to become very large.
> We have spoken to a few others in the field and they have yet to be able to
> rationalize why there is such a large signal.
> I have attached an example of one of the data sets with very large
> amplitude, if anyone would be willing to take a look at the data it would
> be much appreciated.
I think it's interesting that a user of two different software packages
that do not rely upon Ifeffit turns to the Ifeffit mailing list for
help. That's great! This list obviously fills an important gap.
There are rather a lot of columns (189!) in each of your data files and
the header is not very clear about what's what. You might consider
reducing those large, unwieldy, complex, poorly documented files into a
more easily digested form. I have no clue how to turn the contents of
those files into plottable data. Given that you are asking someone to
volunteer their time to help you solve a problem, it seems unkind to
make it so very difficult for a willing volunteer to understand the
nature of your problem.
Bruce Ravel ------------------------------------ bravel at bnl.gov
National Institute of Standards and Technology
Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
Upton NY, 11973
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