The CEM spectrum can be obtained either by collecting essentially all the electrons leaving the surface (integral technique), or by selecting the ones in a given energy range by means of a beta ray spectrometer (differential or depth selective CEMS).
This method allows the use of simple and inexpensive detecting equipment, mainly flow-type proportional detectors in which large counting rates can be obtained.
The information furnished by the integral measurements can be increased by using various angles of incidence or by depositing thin layers of inert material on the sample.
The nuclear de-excitation following the resonant absorption takes place by emission of either a gamma ray or an internal conversion (IC) electron.
In the latter case, the atom is left in an ‘excited’ state with a hole in an inner shell; the energy excess is given away with emission of Auger electrons and/or X-rays.