[Ifeffit] Normalization of XANES spectra

Frenkel, Anatoly frenkel at bnl.gov
Wed Oct 29 09:51:44 CDT 2008


This example may help you understand your problem: if compound a) has a small fraction of metal Cu mixed with a large fraction of oxidized Cu, while a compound b) has it the other way around, then the main (1s - 4p) absorption peak in compound a) will be smaller than in b) after edge step normalization. 

Edge step normalization allows to view all features in XANES and EXAFS regions as if caused by an x-absorption process in a singe atom located in a concentration-average environment of all species in the sample that contain that element. 

Thus, the edge step normalization does have sensitivity to the composition of the sampe. 

Or, I misunderstood your question?


----- Original Message -----
From: ifeffit-bounces at millenia.cars.aps.anl.gov <ifeffit-bounces at millenia.cars.aps.anl.gov>
To: ifeffit at millenia.cars.aps.anl.gov <ifeffit at millenia.cars.aps.anl.gov>
Sent: Wed Oct 29 10:02:54 2008
Subject: [Ifeffit] Normalization of XANES spectra

Hi everyone,

I have a general question:
I know Normalizing is something we do so that we can compare samples 
under different experimental conditions (removes the effect of different 
gains ...) but I have problems in understanding and applying 
normalization when also quantitative conclusions are needed when 
comparing different spectra.

If I have two XANES spectra (a) and (b) measure under the same 
conditions but with different concentration of the absorbing atom with 
in different molecules.If both normalized spectra show a peak 1 , but 
this peak is higher in intensity in spectrum (a) than in spectrum (b), 
does this mean that compound which produced peak 1 is also absolute 
higher in concentration in sample/spectrum (a) or do I loose this 
information after normalization?
Or can I just say: in the normalized spectrum (a) peak 1 is higher than 
peak 2 suggesting that the compound leading to peak 1 is more abundant 
(just relative proportions).But I can't say: The intensity of peak 1 in 
the also normalized spectrum 2 is lower than in spectrum one, Therefore, 
the compound leading to peak 1 is less abundant in spectrum/sample 2. ????

I hope somebody can help me to understand this issue.

Thanks a lot,


Jens Kruse
Institute for Land Use
Faculty for Agricultural and Environmental Sciences
Rostock University
Justus-von-Liebig-Weg 6
18059 Rostock GERMANY
Phone: +49(0)381-498 3190 

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