[Ifeffit] data after rebinning look worse in k-space than before?
edmund.welter at desy.de
Wed Jun 27 09:51:49 CDT 2018
do you also measure as fast as possible in the sense that for two
consecutive scans the points on the energy axis are not at the same
positions? This is what happens at my beamline. The differences are
typically very small but there are differences and one should not just
add all the first points and all the second points and so on because
they are not necessarily exactly at the same energy. Sometimes the
beamline computer is doing something else in parallel (whatever that
might be) and the distance between points A and B is significantly
larger than the distance between B and C.
So, the problem is, at which point does it make sense to merge several
spectra of the same sample? I presume that Athena is taking care of this
when I use it to merge spectra, but it can only do so by interpolating
the points in the spectrum onto a common grid before summing up the spectra.
The best solution might be to rebin/interpolate the spectra onto a fixed
grid before they are imported into Athena (or any other program),
depends on what Athena is exactly doing when it is rebinning data.
Another aspect is that Athena is not very happy about 8600
points/spectrum anyway, at least as long as it using Ifeffit.
On 27.06.2018 15:14, Carlo Segre wrote:
> Hi Ilya:
> We always take data in this mode at APS Sector 10 and I have also find
> that the rebinning function is not working satisfactorily at this
> time. I find that for the current version of the software it is
> better to merge your data and let IFEFFIT interpolate to the dk=0.05
> grid that it uses.
> On Wed, 27 Jun 2018, Ilya Sinev wrote:
>> Hi all,
>> I have a question regarding the chi(k) function isolation and rebinning
>> processes. I have some data recorded in ?quasi channel-cut? modus,
>> i.e. with
>> the mono constantly moving and the data points collected with the
>> possible rate. With 180 sec measurement in yields to a spectrum of
>> ca. 8600
>> point, which obviously needs to be rebinned. The rebinned data, however,
>> does not look good in k-space even if multiple data are merged.
>> Moreover, I
>> have an impression that the raw spectrum in k-space does not have those
>> 8000+ points anymore but significantly less. Is there any reduction
>> of the
>> data points number that is not seen (e.g. as a preparation step for FT)?
>> Since the unbinned data has higher quality, does it then make more
>> sense to
>> keep using it for EXAFS analysis?
>> Thank you
>> Ilya Sinev
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