Next: 5.1 Overview Up: AUTOBK Document Previous: 4 Energy Origin, Pre-Edge, and
Next: 5.1 Overview
Up: AUTOBK Document
Previous: 4 Energy Origin, Pre-Edge, and
term in Eq. (1) represents the absorption due to
the deep core level of an isolated absorbing atom in the solid. This
so-called embedded atom absorption will differ from the absorption for a
truly isolated atom because of the overlap of electron orbitals of
neighboring atoms. It should still be a smoothly varying function of
energy, so that it can be well-separated from the oscillatory part of the
total absorption, but its actual form is poorly known. Current
state-of-the-art calculations of can get only qualitative agreement
with experiments, and their use in analysis is not yet reliable.
The reluctantly accepted practice in XAFS analysis is to use as the
background function ``some reasonably smooth function which, in
some manner, approximates the original 
''. All background
removal techniques use this approach, and the differences between
different techniques lies in how this rather qualitative criterion is
interpreted. In this chapter I'll explain how autobk interprets the
background criterion.
The main principle of autobk is to apply information theory to the separation of the background and XAFS. This allows the qualitative background criteria to be made quantitative and codified. The bearing of information theory on XAFS will be discussed in section 5.2