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





On Jun 14, 2023, at 7:27 PM, Anatoly Frenkel <anatoly.frenkel@stonybrook.edu> 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