[Ifeffit] Rebinning

Carlo U. Segre segre at iit.edu
Tue Mar 11 18:26:57 CST 2003


Jeff Terry mentioned that perhaps I did not explain myself adequately with
the last message.

The algorithm averages BOTH counts and Energy.  We do not just place the
average number of counts at the center of the bin.  Because of this, there
should be no distortion and no need to weight.


On Tue, 11 Mar 2003, Matt Newville wrote:

>Hi Carlo,
>Thanks!!  That's wonderful.  It seems like this should be an
>option in spline() and bkg_cl(), and possibly in pre_edge().  I
>admit to being still a little confused by the goal of the
>rebinning, especially with respect to loss of resolution.  It
>seems like to use this script, you need to do two things:
>  1. select an E0.   The data will be put at energies that
>     will give an even k-grid with this e0.  I think it's
>     inevitable that if e0 changes, you might want to re-bin.
>  2. assume that the k-grid is small enough that the
>     measurements at independent energies are within the
>     acceptable energy resolution that they can be
>     simply summed.
>Is that right?
>Would it be OK with you (and everyone else) to have a weighted
>average replace the boxcar average?  For example, at k=12,
>[E(k+0.05) - E(k)] = 5eV, which is larger than normal energy
>resolutions, so the boxcar average might wash out the high-k
>EXAFS, no?  It might be better to convolve the spectra with a
>lorenztian reflecting the incident energy resolution (probably
>defaulting to 1eV).  Does that seem OK or is there something eles
>going on?
>Anyway, thanks!!
>Ifeffit mailing list
>Ifeffit at millenia.cars.aps.anl.gov

Carlo U. Segre -- Professor of Physics
Associate Dean for Research, Armour College
Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
Carlo.Segre at iit.edu    http://www.iit.edu/~segre

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