[Ifeffit] Large Amplitude Values

Scott Calvin SCalvin at slc.edu
Sat Jul 31 05:52:35 CDT 2010

Hi Gavin,

What are the uncertainties on the high S02 values?

Fluorescence is unlikely to be the culprit. While it can affect your  
ability to normalize properly, you're unlikely to account for a factor  
of 2 by normalization if the data is relatively decent. And self- 
absorption tends to suppress S02, not exaggerate it.

Why did you switch to fluorescence on just the handful of data sets?  
That might provide us a clue.

--Scott Calvin
Sarah Lawrence College

On Jul 30, 2010, at 10:47 PM, Gavin Garside wrote:

> Fellow X-Ray Absorption Enthusiasts,
> I have recently compiled a model that gives excellent visual fits in  
> R, q, and k space for bond spacing in a BCC structure.  This model  
> gives bond spacings that make sense, and are very close to what  
> would be expected from this set.  The R factors are very low, and  
> the enot values correspond quite well to the edge.  However, our  
> amplitude values are much larger than typically expected.  They come  
> in at the range of 1.8 up to 5.0, but only on a few data sets.  On  
> all the rest the amplitude values are 0.4 to 1.0.  Could this  
> increase in amplitude be attributed to the fact that we ran  
> florescence measurements instead of transmission, and have a weaker  
> signal coming to the detector?  What else could be causing this in  
> only one data set? All samples used in this model have the same  
> structure.  Thanks in advance to any replies, your help and time is  
> appreciated.

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