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Experimental and Theoretical Developments in Extended X-Ray Absorption Fine Structure (EXAFS) Spectroscopy


Boland, John James (1985) Experimental and Theoretical Developments in Extended X-Ray Absorption Fine Structure (EXAFS) Spectroscopy. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/YGM3-F114.


To obtain accurate information from a structural tool it is necessary to have an understanding of the physical principles which govern the interaction between the probe and the sample under investigation. In this thesis a detailed study of the physical basis for Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy is presented. A single scattering formalism of EXAFS is introduced which allows a rigorous treatment of the central atom potential. A final state interaction formalism of EXAFS is also discussed. Multiple scattering processes are shown to be significant for systems of certain geometries. The standard single scattering EXAFS analysis produces erroneous results if the data contain a large multiple scattering contribution. The effect of thermal vibrations on such multiple scattering paths is also discussed. From symmetry considerations it is shown that only certain normal modes contribute to the Debye-Waller factor for a particular scattering path. Furthermore, changes in the scattering angles induced by thermal vibrations produces additional EXAFS components called modification factors. These factors are shown to be small for most systems.

A study of the physical basis for the determination of structural information from EXAFS data is also presented. An objective method of determining the background absorption and the threshold energy is discussed and involves Gaussian functions. In addition, a scheme to determine the nature of the scattering atom in EXAFS experiments is introduced. This scheme is based on the fact that the phase intercept is a measure of the type of scattering atom. A method to determine bond distances is also discussed and does not require the use of model compounds or calculated phase shifts. The physical basis for this method is the absence of a linear term in the scattering phases. Therefore, it is possible to separate these phases from the linear term containing the distance information in the total phase.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:EXAFS, theory, multiple scattering, Debye-Waller factors, scattering phase
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Kuppermann, Aron
Thesis Committee:
  • Kuppermann, Aron (chair)
  • Baldeschwieler, John D.
  • Dervan, Peter B.
  • Weinberg, William Henry
  • McGill, Thomas C.
Defense Date:4 June 1984
Non-Caltech Author Email:jboland (AT)
Record Number:CaltechTHESIS:07232014-143633362
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8597
Deposited By: Bianca Rios
Deposited On:23 Jul 2014 22:16
Last Modified:21 Dec 2019 04:53

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