[Ifeffit] Aligning EXAFS E0 to Theory

Carlo Segre segre at iit.edu
Thu Jun 5 14:41:25 CDT 2014

Hi Abney:

What you need to do is

1. Import the data for each scan.

2. if you have multiple scans for each sample, verify that they are all 
aligned (that is that the monochromator energy calibration has not 
changed) by comparing the edge of all of the reference channels (if you 
have reference) or the data scans themselves.

3. If they all align, just skip to step 5 below, if they do not, then ...

4. Align all the scans by aligning the derivatives or whatever method you 
want to us (experiment...)

5. Merge all the data

6. take the merged data set and make sure that the edge position is where 
you want it, usually at the peak in the first derivative of the edge jump.

That is it.  When you are doing the fitting, allow E0 to vary and if it is 
too big, go back to the data and adjust it because it is likely that you 
assined it incorrectly.


On Thu, 5 Jun 2014, Carter Abney wrote:

> Edmund & Drew, thanks for your insights on the matter.  I think between the combination of your responses, things are making more sense.
> Edmund, your question "Why?" is valid.  The answer is: "I misunderstood what was being done in the tutorials/literature."  There is plenty of documentation discussing E0 correction, I'm just new to EXAFS and thought this is what I was trying to do in the alignment menu (and thought this is what they were asking for in the tutorials, etc).  Drew, as you pointed out I don't actually want to adjust the whole spectrum in energy, just the position of E0 to better align the experimental data to the theoretical first shell.
> So, to answer my own question (and make sure I'm actually understanding you):  1.)  I imported the data acceptably, but 2.) should adjust the E0 value for the experimental data by changing the pre-edge range, normalization range, and Rbkg.  I should be able to see the effects of these changes by plotting in k-space with my imported theoretical first shell.
> Someone please (re)correct me if I'm still not getting it right.  Thanks again for the help.
> - Carter
> _______________________________________________
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

Carlo U. Segre -- Duchossois Leadership Professor of Physics
Director, Center for Synchrotron Radiation Research and Instrumentation
Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
segre at iit.edu   http://phys.iit.edu/~segre   segre at debian.org

More information about the Ifeffit mailing list