[Ifeffit] Differences between fluorescence and transmission of the same sample

[Bruce Ravel]

On Wednesday 05 May 2010 11:24:16 am Andrew Campos wrote:

> Thanks so much for the link and the advice! I appreciate it greatly. I
> will advise my lab mates as such and may have to only use the
> fluorescence data if that is indeed the case.
> 
> I also included the file where the lower temperature is included and
> you might come to the same conclusion. The samples that I ran were
> pre-sieved, and the ones included in the .prj file aren't so that
> should be pursued prior to running the experiment. If they crush the
> particle and sieve the sample, I think that we can be more certain
> that this is not the case. This was very helpful!

I would actually come to a different conclusion about your low
tempertaure data.  Those data look like they suffer from
self-absorption (or over-absorption, if you prefer).  See 

   http://xafs.org/Experiment/OverAbsorption

That is, the sample measured in the low T mesaurement appears to be
too concentrated for the fluorescence measurement, however the
transmission data in that case looks just fine.  As Anatoly said, you
could correct the fluorescence data after the fact.  Given that you
have the corresponding transmission data, this correction can be done
accurately by comparison.

I am not clear why the low and high temperature data behave
differently, but then I am not clear quite what is being measured in
each case.

As for the high temperature data -- it is hard to stress highly enough
the importance of good sample preparation.

B


-- 

 Bruce Ravel  ------------------------------------ bravel at bnl.gov

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