[Ifeffit] Question about shift in E0

Mon Jun 6 05:40:44 CDT 2011

hi,
please don't think wrong about my question, but from my experience 
sometimes problems are on the other side of analysis... Simply, I want 
to be clearly sure what you did.
as I understand: you aligned and calibrated spectra in Athena (by 
reference sample) and than you imported the apj file to Artemis? Then 
you fitted your experimental data to the model of the unit cell? If you 
say "fitted E0 in Artemis" you mean usually named  "delE0" in path or 
"Enot" fitting parameter from "Guess, Def, Set" window?
I asked about changes of the set-up of beamline, simply because I had 
met with such problems...
kicaj

W dniu 11-06-06 10:17, Brandon Reese pisze:
> Ahh, it sounds I wasn't entirely clear on what I doing. The 
> measurements were at the In edge, so I aligned all the scans such that 
> the peak in the first derivative of the reference foil was at 27940 
> eV. The peak of the first derivative in the samples was ~27944 eV. The 
> 1st derivative peaks of samples grown without additional oxygen 
> ("conducting") compared to the samples grown with additional oxygen 
> ("intrinsic") were ~0.5 eV different or less.
>
> Using the peak of the first derivative in Athena for the background 
> subtraction, the refined E0 in Artemis was ~7 eV for conducting 
> samples and ~5.5 eV for intrinsic samples. I also tried setting the E0 
> in Athena to the peak of the whiteline, which was about 27950 eV. 
> Again the spread between the white line peak values was ~0.5 eV 
> between samples.  With this value for the background subtraction in 
> Athena, Artemis refined the E0's to be ~1.5 eV for the conducting 
> samples and ~0 eV for the intrinsic samples.
>
> Another piece of information is that the refined CN's for the samples 
> had an inverse correlation to shift in E0. So the conducting samples 
> with a higher E0 (by 1.5 eV) had a lower CN of about 0.1. The 
> calculated correlation in Artemis for the two variables was ~35%.
>
> I didn't intentionally change anything on the beamline setup. I 
> measured all of the conducting samples and then all of the intrinsic 
> samples. So if there was a sudden change in *something* in between the 
> sample groups, it would be consistent. The sample changes took ~10 
> minutes at most, so the change would have to happen on that time 
> scale. The only other consistency I noticed is the conducting samples 
> had to be shifted ~0.7 eV to get the metal foil to line up, and the 
> intrinsic samples only had to be shifted about 0.1 eV.
>
> Brandon
>
> 2011/6/6 "Dr. Dariusz A. Zając" <kicaj at ifj.edu.pl 
> <mailto:kicaj at ifj.edu.pl>>
>
>     Hi Brandon,
>     before someone gives you correct answer, could you shortly inform
>     us, what is the E0 for reference foil, for each experimental data.
>     As I understand you have a shift of 7eV between samples, but
>     measured on samples, thus would be nice to see what is the shift
>     for reference.
>     The second question comes for me automatically - have you done
>     something with the beamline set-up between experiments ?
>     kicaj
>
>     W dniu 11-06-06 08:56, Brandon Reese pisze:
>>     Hi all,
>>
>>     I am looking at EXAFS of thin film metal oxides.  I am varying
>>     both metal content and the oxygen content of the films. I aligned
>>     the scans with a metal reference foil collected simultaneously. 
>>     In Artemis, I have noticed that when changing between films with
>>     no extra oxygen versus those with extra oxygen there is a shift
>>     in the fitted E0 of ~1.5 eV (after aligning to the foil). I tried
>>     setting the E0 in Athena to the peak of the 1st derivative and
>>     the peak of the white line with the same result (~7 eV
>>     difference). I was a little surprised by the offset because in
>>     Athena the E0 values varied by <0.5 eV. I am not sure if the
>>     argument could be made that this shift is a result in a changing
>>     oxidation state because it doesn't show up in the XANES (at least
>>     qualitatively).  Are there other experimental effects that could
>>     cause a shift like this, or is this likely something real in my
>>     material? If anyone want to see a representative group of data,
>>     let me know.
>>
>>     I also have an unrelated quick (I think) question on the EXAFS
>>     equation. In some references I see a term 1/(k R)^2 and in others
>>     it is 1/(k R^2). I couldn't really see any reason for the
>>     difference, unless it is to correct for subtle differences in how
>>     the other terms are defined.
>>
>>     Thanks
>>     Brandon
>>
>>
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