[Ifeffit] Logical range for Amplitude Reduction Factor in EXAFS fitting results

[Matt Newville]

Hi Esmael,

Can you give specifics for what you see as "extremely large"?   In
principle, the amplitude reduction factor should be in the range of 0.7 to
1.0, but values a bit outside that range could certainly be believable.

In lots of EXAFS analyses S02 is used to compensate for several data
measurement and processing challenges, including the energy resolution of
the measurement and normalization by the edge step in addition to the
intended purpose of accounting for the not-quite-perfect estimate of the
S02 factor in the EXAFS calculations.

There is also the sort of inherent room for confusion about where the
coordination number is folded into the overall amplitude -- sometimes one
wants to fix the coordination number and sometimes one wants to vary it,
and what gets reported as "amplitude" can vary quite a bit.

--Matt

On Tue, Jan 24, 2023 at 8:41 AM Esmael Balaghi <
esmael.balaghi at fit.uni-freiburg.de> wrote:

> Dear All,
> I noticed that some published works have reported extremely large values
> for the amplitude reduction factor. This seems a bit unusual, as the
> amplitude reduction factor is typically expected to be in the range of 0 to
> 1. I am curious to know what could be the reasons behind it to get such
> large values for the amplitude reduction factor during EXAFS fitting.
>
> Thank you in advance for your insights.
>
> Esmael
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