[Ifeffit] C and N NEXAFS normalization

[Peter Nico]

Hello All,

I am looking for thoughts and opinions regarding the best way to 
approach post-edge fitting and normalization of C and N NEXAFS data.  I 
know soft x-rays aren't exactly the focus of the list, but it is still 
the best access to a lot of people with a lot of XAS knowledge, and I 
would be very interested in your opinions.

Obviously, linear or quad curve fitting followed by normalization is 
standard and well accepted for hard x-ray spectra.
 
However, as far as I can tell there is no such accepted norm of C and N 
NEXAFS treatment.  I have seen that some groups use a single point 
normalization, e.g. 310 for the case of C, and simply divide through the 
entire spectrum with this value.  Other groups take the min and max 
value of the spectrum and map it onto a 0 to 1 scale.   Neither of these 
approaches seems satisfactory to me for data with obvious backgrounds 
like those attached.  While these data are not perfect, it seems like 
they should definitely be useable.

My thought is why not do a 'standard' hard x-ray type normalization like 
that shown with an e0 set to the theoretical ionization potential for C 
or N.  I understand that this has problems with the potential of 
including tailing sigma* transitions or first EXAFS oscillations in the 
background region because it doesn't extend far enough beyond the edge.  
However, it seems to me an approach like this must be 'less-wrong' than 
the more simplistic methods mentioned above and capable of yielding 
useful data.

Thoughts, comments, jeers?  --Peter






-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20100608/8fb0ae8b/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: moz-screenshot-4.jpg
Type: image/jpeg
Size: 43168 bytes
Desc: not available
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20100608/8fb0ae8b/attachment.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: moz-screenshot-5.jpg
Type: image/jpeg
Size: 41841 bytes
Desc: not available
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20100608/8fb0ae8b/attachment-0001.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Iffefit_question.ppt
Type: application/vnd.ms-powerpoint
Size: 113664 bytes
Desc: not available
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20100608/8fb0ae8b/attachment.ppt>