[Ifeffit] S02-Interpretation

Norbert Weiher weiher at chem.ethz.ch
Wed Apr 14 08:13:29 CDT 2004

Dear Friends,

I would like to ask a question on the interpretation of S02 in a fit. Although 
there has been some discussion on this parameter, I did not find exactly what 
I was looking for. Here it goes:

To my knowledge, S02 accounts for intrinsic as well as extrinsic losses in the 
sample. Now, if I have two samples and determined the S02 value according to 
the way which Bruce has in his supplement to the FEFFIT course, I find two 
differing values for electrochemically prepared oxide (0.74) and crystalline 
gold oxide (0.92). This difference is independent of beamlines I measured and 
I can exclude quite safely that it is just a measurement error - it comes up 
with any spectrum I recorded on these systems.

When discussing this with my colleagues, we interpreted the S02 difference as 
an indication of more disorder in case of the electrochemical system (which 
would well fit to my picture of the whole thing). 

BUT: Is there any physical reason to assign a difference in S02 (for 
"chemically equivalent" systems, where just the preparation is different) to 
a structural disorder?



Dr. rer. nat. Norbert Weiher (weiher at chem.ethz.ch)
Institute for Chemical and Bioengineering - ETH Hönggerberg
HCI E 117 - 8093 Zürich - Phone: +41 1 63 3 48 32

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