[Ifeffit] Energy Resolution

[Robert Meulenberg]

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 at maine.edu

On Wed, May 9, 2018 at 3:24 AM, Julian Ehwald <jehwald at gmail.com> 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
>
> -----Ursprüngliche Nachricht-----
> Von: Ifeffit [mailto:ifeffit-bounces at millenia.cars.aps.anl.gov] Im Auftrag
> von Carlo Segre
> Gesendet: Sonntag, 6. Mai 2018 01:07
> An: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
> 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 at iit.edu   http://phys.iit.edu/~segre   segre at debian.org
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