The application of coincidence detection techniques produces a dramati
c increase in the information obtained from particle and photon scatte
ring studies. A clear illustration of this is given by Anger Photoelec
tron Coincidence Spectroscopy (APECS), By coincident detection of the
ejected photoelectron and the resulting Auger electron during x-ray ex
cited Auger spectroscopy, it is possible to distinguish the true origi
n of peaks and satellites within the Auger spectra. For example, it be
comes possible to separate standard Auger processes from those occurri
ng in conjunction with Coster-Kronig transitions and from those either
followed or preceded by shake-off or shake-up transitions. In additio
n, the technique often allows the separation of overlapping series of
Auger peaks, thus permitting the study of individual elements within c
ompounds and alloys, These possibilities will be illustrated primarily
by reference to APECS studies of 3d transition metal elements.