Re: [Ifeffit] Brain teaser

Hi Anatoly, maybe the high voltage of the I0 chamber is off? All the best, Kirill Dr. Kirill A. Lomachenko Scientist at BM23/ID24 beamlines European Synchrotron Radiation Facility 71 avenue des Martyrs CS 40220 38043 Grenoble Cedex 9, France Tel: +33 438 88 19 14 www.esrf.eu On 15/06/2023 08:09, ifeffit-request@millenia.cars.aps.anl.gov wrote:

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Today's Topics:

1. Re: Brain teaser (Anatoly Frenkel) 2. Re: [Ext] Brain teaser (Jeffrey Terry) 3. Re: [Ext] Brain teaser (matthew marcus)

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Message: 1 Date: Thu, 15 Jun 2023 00:30:41 -0400 From: Anatoly Frenkel To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] Brain teaser Message-ID: <866EACCF-DAD2-4486-AAE0-AC3F6B28023E@stonybrook.edu> Content-Type: text/plain; charset=utf-8

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

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On Jun 15, 2023, at 12:22 AM, matthew marcus 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

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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

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On Jun 14, 2023, at 11:34 PM, matthew marcus 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

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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 _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit

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Message: 2 Date: Thu, 15 Jun 2023 00:17:35 -0500 From: Jeffrey Terry To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] [Ext] Brain teaser Message-ID: Content-Type: text/plain; charset="utf-8"

Well, I?ll take a shot. Looks like the mirror angle is totally fubared, you are getting Bragg peaks from the coating or substrate that are giving you the peaks in Io. Since you have no idea what angle those are going through Io, they are unlikely to make it into either the sample or It. Since those photons are removed from the beam hitting the sample, they would show up as intensity dips in It. I?d bet that most (all?) of the reflected beam is not going into the sample. I?m kind of surprised It signal is as clean as it is, but then I don?t know the gains on either measurement amplifiers. I couldn?t find a flat mirror angle that would cause the cutoff at 12870? eV but since it is a collimating mirror who knows what range of angles were actually being hit.

Jeff Terry Interim Chair, Department of Biology Interim Chair, Department of Social Sciences Professor of Physics Professor of Mechanical, Materials, and Aerospace Engineering Editor, Applied Surface Science Illinois Institute of Technology 3101 S. Dearborn St. Chicago IL 60616 630-252-9708

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On Jun 14, 2023, at 7:27 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

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