[Ifeffit] Is it legitimate to merge transmission data with fluorescence data?

[Bruce Ravel]

On Monday 10 August 2009 06:13:32 pm jrkizews at 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



-- 

 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

 My homepage:    http://xafs.org/BruceRavel
 EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/