[Ifeffit] Ratio of peak amplitudes in R-space

[Matt Newville]

Hi Jatin, Scott, Chris,

Just to add to Chris's and Scott's response:  analyzing the peak
height of the magnitude of the Fourier transform of an EXAFS spectra
would be collapsing an entire spectra to a single value.  We know that
EXAFS is a complicated function of k and R, and such a simplistic
analysis are bound to be error-prone.

You might be able to find a set of spectra (say, a temperature
dependence with no coordination number change and a tiny distance
change) where the change in peak height would map well to sigma2.
But if that works, so would a very simple modeling of the system.  The
danger is that there is no way to tell when such a simplistic analysis
is failing.

In short: don't do it.

--Matt