STUDIES BY MEANS OF SYNCHROTRON RADIATION
STUDIES BY MEANS OF SYNCHROTRON RADIATION
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Date
1984-10
Authors
OLADIPO, OMOTOLA AFOLAYAN
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Abstract
Extended X-ray Absorption Fine Structure [EXAFS) has become known in
recent years as a technique for studying the environment of specific elements
in chemical systems. This has been related to the advent of synchrotron
radiation. The significance of the present studies is to find out how to
calculate the EXAFS spectra of our samples, otherwise called "model compounds"
(standards or calibrants) viz:
potassium bromide - KBr;
manganese( II) ammonium sulphate hexahydrate - MnSOJNH ) SO .6H O;
and strontium bromide hexahydrate - SrBr2.6H O;
from the information available to us from their crystal structures. The EXAFS
data for the samples were obtained from the Daresbury Synchrotron Radiation
Source and analysed via appropriate UMIST computer programmes. We have
assumed that the scattering factors from the Daresbury MUFPOT programme
as used in our calculations in the EXAFS region beyond - 70 eV are reliable.
The first objective of the work involved carrying out calculations in the EXAFS
regime termed "short-range" refinements for convenience.
The second objective investigated the possibility of extending these calculations
to the inner region called XANES (X-ray Absorption Near Edge Structure).
Although these calculations gave a fit in the EXAFS region, the f i t in the
inner region was not satisfactory. The final objective was to attempt to
modify the scattering factors in the XANES regime and termed "long-range"
refinements. The computer programme involved employed curve f i t t i ng by
Least Squares, and Fourier transformation techniques. The attempts to modify
the scattering factors in the XANES region were largely successful and the
results obtained from these studies will be of use in refinements determining
unknown structures of compounds with similar atoms to those in the present
investigation.
Description
A Dissertation presented to
THE FACULTY OF TECHNOLOGY
Keywords
SYNCHROTRON, RADIATION