Re: [Ifeffit] Ifeffit Digest, Vol 183, Issue 9

yes i m talking about the jahn teller type distortion, any hint to include in atom *A. Ahad* *--------------------* *Abdul Ahad* Junior Research Fellow *Dept of Physics* *Aligarh Muslim University* *Aligarh 202002 (U.P.), India* *http://www.researcherid.com/rid/G-8198-2018 http://www.researcherid.com/rid/G-8198-2018* *Email: a_ahad.rs@amu.ac.in , ahad@mailaps.org * On Wed, May 9, 2018 at 8:30 PM, wrote:

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Today's Topics:

1. Re: Energy Resolution (Julian Ehwald) 2. Re: Energy Resolution (Robert Meulenberg) 3. 4+2 model for distortion (Abdul Ahad) 4. Re: 4+2 model for distortion (Anatoly Frenkel)

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Message: 1 Date: Wed, 9 May 2018 09:24:27 +0200 From: "Julian Ehwald" To: "'Carlo Segre'" , "'XAFS Analysis using Ifeffit'" Subject: Re: [Ifeffit] Energy Resolution Message-ID: <006901d3e766$c4284410$4c78cc30$@gmail.com> Content-Type: text/plain; charset="iso-8859-1"

Hi Carlo

Thank you very much for your answer! If you say it is sufficient to use dk=0.05, that means I would be able to collect a full EXAFS spectra (k=0 to 12) in only 250 datapoints? That would save us a lot of time!

Best, Julian

-----Urspr?ngliche Nachricht----- Von: Ifeffit [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] Im Auftrag von Carlo Segre Gesendet: Sonntag, 6. Mai 2018 01:07 An: XAFS Analysis using Ifeffit Betreff: Re: [Ifeffit] Energy Resolution

Hi Julian:

With an edge energy of 543 eV, your monochromator resolution should be at least 0.1 eV. If you are interested in XANES, you need to take data at this resolution or maybe even better. ONce past the edge, there is no need to keep that step size. If your beamline permits an EXAFS-type step scan with steps in k-space, you want to use a dk of 0.05 which is what IFEFFIT interpolates to. Smaller step sizes are not really useful.

Carlo

On Sat, 5 May 2018, Julian Ehwald wrote:

...

Dear all,

This might be a very general question, but: I was wondering what energy resolution you typically use at beamlines to obtain your raw data for exafs. Since we have limited Beamtime only and other experiments that we want to carry out, I was wondering what kind of resolution is common. Or differently: Is it predictable what happens if I for example change from steps of 0.2eV to 0.4eV? We want to obtain spectra up to 500eV above Oxygen K, if that is of relevance.

Best, Julian

-- 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

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Message: 2 Date: Wed, 9 May 2018 08:54:31 -0400 From: Robert Meulenberg To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] Energy Resolution Message-ID: Content-Type: text/plain; charset="utf-8"

Julian,

Keep in mind that to get to k=12, you will need to go out to ~1100 eV. At these energies, you will encounter just about every 1st row transition metal L edge, and a handful of other M-edges for heavier elements. So if you have anything else in your sample, EXAFS will probably not be possible. That is usually why people don't try to do EXAFS analysis at the soft x-ray energies.

Regards,

Rob

Robert W. Meulenberg Associate Professor of Physics Laboratory for Surface Science and Technology Department of Physics and Astronomy University of Maine Orono, ME 04469 phone: 207-581-2245 email: robert.meulenberg@maine.edu

On Wed, May 9, 2018 at 3:24 AM, Julian Ehwald wrote:

...

Hi Carlo

Thank you very much for your answer! If you say it is sufficient to use dk=0.05, that means I would be able to collect a full EXAFS spectra (k=0 to 12) in only 250 datapoints? That would save us a lot of time!

Best, Julian

-----Urspr?ngliche Nachricht----- Von: Ifeffit [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] Im Auftrag von Carlo Segre Gesendet: Sonntag, 6. Mai 2018 01:07 An: XAFS Analysis using Ifeffit Betreff: Re: [Ifeffit] Energy Resolution

Hi Julian:

With an edge energy of 543 eV, your monochromator resolution should be at least 0.1 eV. If you are interested in XANES, you need to take data at this resolution or maybe even better. ONce past the edge, there is no need to keep that step size. If your beamline permits an EXAFS-type step scan with steps in k-space, you want to use a dk of 0.05 which is what IFEFFIT interpolates to. Smaller step sizes are not really useful.

Carlo

On Sat, 5 May 2018, Julian Ehwald wrote:

...

Dear all,

This might be a very general question, but: I was wondering what energy resolution you typically use at beamlines to obtain your raw data for exafs. Since we have limited Beamtime only and other experiments that we want to carry out, I was wondering what kind of resolution is common. Or differently: Is it predictable what happens if I for example change from steps of 0.2eV to 0.4eV? We want to obtain spectra up to 500eV above Oxygen K, if that is of relevance.

Best, Julian

-- 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

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