[Ifeffit] Amplitude and sigma square

[Carlo Segre]

Hi Abdul:

You have significant self absorption effects.  YOu can see this by loading 
both transmission and fluorescence data and comparing them.

The trick I use when I have more than one shell close to each other is to 
constrain the sigma squared values to be equal for both paths.  This will 
give you an average between the two.  The real question is what is the 
sigma squared when you just use a single path?

Carlo


On Tue, 29 May 2018, Abdul Ahad wrote:

> Hi all,
>
> Thanks to Professor Pierre, Prof. Segre and Prof. Scott, for make some
> beautiful comments.
>
> One thing i wish to mention here that i have both Fluorescence and
> Transmission data, with the same model transmission data give Amplitude
> around 0.72 but Fluorescence gives 0.15, Is this self absorption problem,
> as prof. Segre suggested. Also i have tried with one shell with N=6 and
> then 4 and 2 and i got the genuine trend on average under limit of error.
> But the for N=2 the sigma goes to 0.0001 order while for N=4 it is usual
> 0.001 order (this both have simultaneously taken in a one fit). Also N=6
> gives all variable fine.
>
> thanks
>

-- 
Carlo U. Segre -- Duchossois Leadership Professor of Physics
Interim Chair, Department of Chemistry
Director, Center for Synchrotron Radiation Research and Instrumentation
Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
segre at iit.edu   http://phys.iit.edu/~segre   segre at debian.org