Dear All,
Just picking up on Bruce's point about self-absorption. If you are using
Viper <http://www.cells.es/Beamlines/CLAESS/software/viper.html>, I know
that there is a way of correcting the measured fluorescence data for
self-absorption. This correction is based on work by Tro"ger
<http://prola.aps.org/abstract/PRB/v46/i6/p3283_1> et al., and is quite
easy to perform, using the "corrections" button in the "get chi" box of
Viper. Of course the correction is based on an /estimation/ of the
"real" self-absorption...
Best wishes,
Maurits.
Bruce Ravel wrote:
On Monday 10 August 2009 06:13:32 pm jrkiz...@ncsu.edu wrote:
Dear XAFS community members,
I have a question concerning data merge. We normally collect XAFS data in
both transmission mode and fluorescence mode. We normally have to merge a
few scans to enhance signal-to-noise ratio. For one particular sample, I
want to know if it is legitimate to merge its transmission scans with its
fluorescence scans to improve data quality?
Hi Fiona,
There is no a priori reason not to do so and certainly not a numerical
reason. From a numerical perspective, you can merge anything with
anything!
My one concern is that the fluorescence and transmission data are
really equivalent. That is, if the fluo data are affected by
significant self-absorption attenuation or if the transmission data
suffer from significant pin-hole effects, then you run the risk of
degrading the entire data set by doing the merge. But if the data are
merely noisy, then I think you are safe doing so.
Think about it this way: when you use a multi-element detector, you
are making several measurements which are presumed to be identical.
We routinely merge the channels of an MED. You situation is, from a
measurement theory perspective, analogous. Assuming your data do not
suffer from the problems mentioned above, it seems all right to me.
B
--
Dr. M.W.E. van den Berg
Ruhr Universitaet Bochum
Lehrstuhl fuer Technische Chemie
Gebaeude NBCF-Sued 04/686
Universitaetsstrasse 150
44780 Bochum
Germany
Tel.: +49-234-3226907
Fax: +49-234-3214115
E-mail: maurits.vandenb...@techem.rub.de
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