[Ifeffit] Very large exafs amplitude in collected data - cause unknown

Matt Newville newville at cars.uchicago.edu
Wed Jun 5 12:06:07 CDT 2013

Hi Jason,

I didn't try to use the original data (and, like Bruce's rant, once I
saw that it was a spec file with multiple scans [er file and with 100+
columns, I didn't even try).   But from looking at the spectra Bruce
posted, it's hard to see what the problem might be.   It's hard to say
that the data is clearly wrong.  It does look a lot like Au foil, but
with a much, much lower sigma2, or much higher energy resolution or
mean-free-path or something else to increase the amplitude in a
k-dependent way .    It's hard to see how any measurement problem
would give such an artifact, but we don't know a lot about how the
measurements were made.

Obviously, a clearer data file would be helpful, as would more
information about the sample and measurements.   What values do you
get for sigma2?   You said the values were not sensible, but you
didn't say what that was.  You also said the amplitude was "huge, up
to 80 in some cases".   I have no idea what that means...

Was the sample cold?  Do you have multiple measurements that show the
same amplitude behavior?


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