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For the work described in this chapter, systems with well known structures
were chosen so we could demonstrate the enhanced sensitivities of DAFS.
The goals of the DAFS analysis were to isolate the fine structure
oscillations and, from them, to obtain the detailed wavevector and site
selected XAFS-like short-range order information and XANES-like structural,
valence and empty orbital information. This section describes the methods
that we have developed to isolate the DAFS signals and to analyze the
isolated signals. The main steps are listed schematically:
The following subsections describe some of the important aspects of these
analysis methods. The detailed analysis procedures are described in
- Measure the Bragg intensities versus photon energy and apply the
standard absorption and diffraction corrections.
- (a) Measure and subtract the background.
- (b) Apply the area, Lorentz-polarization, instrument and absorption
- (c) Remove any Bragg glitches from the XAFS and determine .
- Isolate the fine structure using method 2a or 2b.
- (a) Isolate the effective fine structure term directly from
the diffracted intensity using spline methods analogous to conventional
- (b) Impose the Kramers-Kronig relation between the real and
imaginary components of the DAFS signal, and use an iterative method to
extract the real and imaginary components, f'(E) and f''(E), from the
- Use FEFF to analyze the isolated fine structure signals.