Re: [Ifeffit] Energy Resolution

Hi Carlo Thank you for your answer. I have completely different question as well: I just started using Artemis, and have a question regarding the amplitude reduction factor: I use different So^2 for different elements, correct? If I start fitting and have paths involving the same kind of atom but once at distance 2A, and once maybe 3A, is this then the same So^2 or am I supposed to model the behaviour of So^2 somehow? Similar for \Delta R: If I don’t have a nice simple cubic structure and can’t use isotropic expansion similar like alpha*R_eff, what would be a smart(or physically correct) way to connect \Delta R (as well as sigma^2) for the same element for different distances? The material I am looking at is Li2O2 and Li2IrO3, which don’t have a very simple structure. I am aware that maybe I am asking a bit much, but if you could help me in any way I would be very delighted. Best, Julian -----Ursprüngliche 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