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 jrkizews@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.vandenberg@techem.rub.de