[Ifeffit] question about S02 (passive electron reduction factor)

[Scott Calvin]

Hi Yu-Chuan,

There are several possibilities. One is sample prep. If you have an
extremely uneven sample (lots of pinholes, etc.) in transmission it can
lead to results like you're describing. Another is normalization. If you're
using Athena for background subtraction make sure you look at the pre-edge
line and post-edge curve and see that they look reasonable. Sometimes if
the background has a funny shape to it Athena can create a post-edge curve
that shoots way up at the edge energy; this could also lead to the effect
you're describing. Finally, look at the correlation between S02 and
sigma2...if it is very high (say 0.95 or above) it may simply be coming up
with low estimates for each. There are, of course, other possibilities as
well, but in my experience those are the most common.

--Scott Calvin
Sarah Lawrence College

>This is Yu-Chuan. I am now trying to fit my sample, magnesium
orthovanadate.  
>I try to follow Bruce's Cu example and Scott's ZnO example steps and I
found a 
>problem come to my fitting. At the beginning of the fitting, the S02(amp)
are 
>far away from 0.9 (just about 0.3). It's much different than Bruce's and 
>Scott's examples. For Cu and ZnO examples, the fitting results of amp are 
>close to 0.9 at the beginning even if you set just four parameters
(guess:amp, 
>e0, delr, and ss). Also, John have said that the S02 value should be around 
>0.9. That's why I am wondering if there is anything wrong with my data 
>processing? Does anyone happen to have this kind of problem? Thank you for 
>your help.
>