[Ifeffit] Basic questions on XANES

[Ashley Harvey]

Dear ifeffit users,

This posting is with quite basic questions on XANES data processing.
I am a somewhat new XANES experimentalist, in a group that does not  
typically use XANES, so I am lacking some basic knowledge.

For normalization of XANES, my impression is that people generally  
normalize the spectra from ca. 50 eV up to 100 eV or more after the  
edge onset.  Is there a standard acceptable normalization range for K  
edges?  I have noticed that when I change the start of the  
normalization window by even a few eV, this can make substantial  
differences in the XANES when comparing two similar spectra (for  
example, change in peak and pre-edge peak intensities between XANES  
of one sample at two temperatures).  I keep second-guessing my choice  
of normalization range.

Second, I am also looking at the effect of the various ways to set  
E0.  When I start with ifeffit's default (how is this determined?)  
and then proceed to set E0 to the zero-crossing of 2nd derivative,  
I'll get value X.  When I change it to a set fraction of the edge  
step (is this legitimate?) I typically get a lower value, and then  
when I proceed again to set it to the 2nd derivative zero-crossing, I  
get a value different from the first time it was set to the zero- 
crossing.
For example, the E0 at an Fe K edge:
ifeffit default = 7128.9 eV
2nd derivative zero = 7128.8
set fraction = 7125.1
2nd derivative zero = 7125.5
The value given by the 2nd derivative zero-crossing is dependent on  
the previous E0 setting.

I am having a hard time to move on to the actual interpretation of  
the data while I am still uncertain about such details.
Thanks for your patience with some simple questions.

Best,
Ashley