[Ifeffit] Brain teaser

[Anatoly Frenkel]

Amazing idea. I thunk you were the only one who succeeded to use third harmonic of Si for taking EXAFS at high atomic number elements. But that does not explain the peaks and dips. 

Anatoly

> On Jun 15, 2023, at 12:22 AM, matthew marcus <mamarcus at lbl.gov> wrote:
> 
> Suppose the mono is being used at the 333 reflection (for Si), intentionally working at the 3rd harmonic.  In that case, if the fundamental isn't filtered out, you could get just what we see, with the sample doing the filtering before the beam gets to the transmission chamber.
>    mam
> 
>> On 6/14/2023 9:16 PM, Anatoly Frenkel wrote:
>> Thank you, Matthew and Robert, but I think the explanation is more simplle. The fact that there are peaks in I0 and dips in transmission is a clue that explains why transmission is almost linear while I0 curves up.
>> Anatoly
>>>> On Jun 14, 2023, at 11:34 PM, matthew marcus <mamarcus at lbl.gov> wrote:
>>> 
>>> One thing that's pretty odd is that the glitches are peaks in I0, and dips in It.  It would be much easier to explain if It was the one that increased steeply and I0 was more linear, but the presence of the edge in It shows that you didn't switch them.  Red = It.  What's that sudden drop at the end?
>>> 
>>> Could it be that the I0 chamber is misaligned so that beam is scraping one of the plates?  That could cause all sorts of odd things to happen.
>>>    mam
>>> 
>>>> On 6/14/2023 5:27 PM, Anatoly Frenkel wrote:
>>>> Hello, all. It is a low- to medium- level brain teaser.
>>>> Pt-coated collimating mirror was in place for Pd K-edge measurement, but Au L3-edge of Pd-Au alloy was measured (for testing purposes). I0 and It detectors were both Ar filled ionization chambers. Because of the energy dependence of reflectivity of the Pt mirror, I0 intensity was strongly nonlinear (blue curve). However, the transmission intensity in the It detector was almost linear (red curve). Why?
>>>> Anatoly
>>>> image.png
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