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| Book/Report/Dissertation / PhD Thesis | PUBDB-2019-00851 |
; ;
2016
Verlag Deutsches Elektronen-Synchrotron
Hamburg
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Please use a persistent id in citations: doi:10.3204/PUBDB-2019-00851
Report No.: DESY-THESIS-2018-043
Abstract: This thesis deals with the further development of the method of Borrmannspectroscopy and the development of the novel method of diffractionanomalous fine structure in Laue geometry.Borrmann spectroscopy utilizes the Borrmann effect in order to enhancethe quadrupol absorption, which enables studying weak quadrupoltransitions. In the present work a model is developed, which describes thedependence of the quadrupol enhancement on temperature and anisotropyof the chemical environment. This model is used to describe the Borrmannspectroscopy results obtained from a strontium titanate single crystal.Furthermore, the influence of the mosaicity of real crystals on thequadrupole enhancement is studied by means of simulations, which arebased on the dynamical theory of diffraction and a modified structuremodel of barium titanate.The method of diffraction anomalous fine structure (DAFS) is based onthe combination of X-ray diffraction and absorption spectroscopy and allowsinvestigating the local atomic structure of centrosymmetric crystalsutilising the additional selectivity due to diffraction. In the present workthe novel method of diffraction anomalous fine struture in Laue geometry(LDAFS) is developed. It utilizes the intensity of the Laue geometrydiffracted beam, which experiences an altered absorption due to the Borrmanneffect. Its experimental applicability is verified by experiments ona barium titanate single crystal and comparison with conventional X-rayabsorption spectroscopy results.
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