Self-Absorption corrections in Fluorescence EXAFS
Master thesis
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http://hdl.handle.net/11250/2406048Utgivelsesdato
2016-06-13Metadata
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Sammendrag
Variation of the absorption properties as a function of energy across, or near, an absorption edge is known as
EXAFS (Extended X-ray Absorption Fine Structure). This technique implies scanning over an absorptionedge
and simultaneously record the (fluorescent in this case) signal by a suitable detector. This signal
contains, among other things, information of the local chemical coordination (interatomic distances etc.) of
the compound observed. It is a well-known and much used technique. However, one issue which has not
been considered well enough, is the question of influence by the sample geometry. As a first approximation
one always assumes a sample of ”infinite size”, or only one finite thickness parameter. The department’s
research group, has been working with improving this, by taking into consideration the sample geometry in
terms of a cylinder or a sphere. The theory dealing with these geometries has been established. There was
also collected absorption coefficient’s data sets for this, using copper sulphate as the reference sample. The
purpose of the work is to analyze the data sets and perform the developed self absorption corrections and
evaluate whether it is possible to establish a new correction tool. The data processing and the execution of the
correction models confirm the dependency of the self-absorption effect on parameters such as concentration
and thickness (by inner radius) of the sample, and a good agreement between the first order approximation
and complete numerically evaluated corrections for both spherical and cylindrical cases.
Beskrivelse
Master's thesis in Mathematics and Physics