On Tue, Jan 22, 2013 at 1:15 PM, Matt Newville
<newville@cars.uchicago.edu> wrote:
Hi Soma,
> 2) A lot of times we find So2 from the respective metal foil and fix it
> when we fit the sample data for the same element. Is there any reference for
> this one?
>
> I know about the book by Shelly, Hesterberg and Ravel.
> Would appreciate if I get some more references.
I'm not aware of a truly thorough study of this convention. Several of
the early UWXAFS papers mention using this approach. Probably the
clearest statement is from
E A Stern, et al "The UWXAFS Analysis Package - Philosophy and Details",
Physica B208 pp 117-120 (1995)
[DOI: 10.1016/0921-4526(94)00826-H]
which states (full paragraph):
The set of parameters that most frequently have a strong
enough correlation to give difficulty in obtaining their
values separately are S02, the passive electron overlap
constant[13], sigma^2, the disorder about the optimal
distance, and N, the number of atoms in a particular
coordination shell. The most reliable way to separate out
sigma^2 from the other two parameters is to measure the
temperature dependence of sigma^2 and vary the product S02*N
so as to obtain a fit to an Einstein oscillator, particularly
the zero point value. Since S02 is dependent essentially on
only the center atom, it can be found in known structures and
N determined from the S02*N value.
Here Reference 13 is to Stern and Heald's chapter in the Handbook of
Synchrotron Radiation Vol 1 (1983).
Cheers,
--Matt