Re: [Ifeffit] Basic questions about the preliminary data processing in Athena

The calibration should be done at the beamline with a foil. Once that is done, then you don't really want to change it. Remember that just shifting the energy is not actually the correct way to do a shift. The energy shift is a non-linear function of the angle (Bragg's Law) and so when you shift energy you are really distorting Chi(k) since that is also a non-linear function of energy (E^1/2). Yes, it is usually a small effect but I prefer not to apply too many shifts in energy if possible. I assume that the calibrate function is the same as the align except the E-shift is left at zero and a correction is applied permanently to the data. Carlo On Mon, 23 Jul 2018, Haifeng Li wrote:

Hi, Carlo,

Thanks for your answer.

I may ask you more questions. Why you do not recommend to calibrate the data? Calibration is used to find the E0 and match it to the literature data. What is the real difference between calibration and alignment?

Thanks,

Haifeng

On Sun, Jul 22, 2018 at 5:30 PM, Carlo Segre wrote:

...

Hello Haifeng:

Personally, I would not calibrate the data but merely align the references of A2 and A3 to the reference of A1 and similarly align B2 and B3 references to that of B1. Once merged, you can then aligh the reference of the merged B samples to that of the merged A samples.

If you keep the references then you can always align data taken at a leter time to these data sets. If the energy of your reference is a small bit off from the tabulated value, that is OK as long as all the data being compared has aligned references.

Carlo

On Sun, 22 Jul 2018, Haifeng Li wrote:

Dear ALL,

...

I am a beginner in Athena. Recently I got the spectra and I am confusing about the data calibration and alignment. The manual shows that calibrate the reference data of one scan and align other reference data to that calibrated one.

Here I want to show examples. I have two samples A and B, Each sample has three scans with the corresponding reference data. For sample A, 1st scan is calibrated and the other two scans are aligned to 1st scan. Then merge them into merged A. The same procedures for sample B and get merged B. If I want to compare XANES of sample A and B, do I need to align the merged reference data between A and B? If so, why? My understanding is that all scans (original data and merged data) in sample A and B are calibrated to standard edge energy. Why do they need to align?

I appreciate your help.

Thanks,

Haifeng

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

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