Modern Spectroscopy

318 8 PHOTOELECTRON AND RELATED SPECTROSCOPIES
Figure 8.22 Cylindrical analyser used in an Auger spectrometer
Various types of energy analysers have been used for the Auger electrons but one of the
most successful is that shown in Figure 8.22. There are two coaxial cylindrical plates, the
inner one earthed and the outer having a variable negative voltage applied to it. Some Auger
electrons emanating from the target (sample) pass through spaces in the inner plate and,
when a voltage V is applied to the outer plate, only electrons for which the kinetic energies
correspond to that value of V will pass through the second set of spaces and be focused onto
the detector. The Auger electron spectrum is then the number of electrons reaching the
detector as a function of V . With this type of analyser Auger electrons are collected over a
360 angle.
8.2.1.2 Processes in Auger electron ejection
A common example of an Auger process involves the ejection of a photoelectron, as shown
in Figure 8.23, from the K shell (i.e. a 1s electron), with energy E P; which is not considered
further. Following the ejection of a K electron it is common for an electron from the L shell,
specifically from the L 1 (or 2s) orbital, to fill the vacancy releasing an amount of energy
Figure 8.23 Illustration of a KL IL II Auger process