Electron Decay Processes

An excited quasi-discrete state which is embedded in the continuum of the next higher charge state of the system is called an autoionizing or an Auger state (more generally a resonance state). It can decay either by electron emission (nonradiative transition) or by emission of radiation, the former is by far the dominant decay mode unless the transition energy is large (> 5 keV) or selection rules hinder the nonradiative transition. The radiationless decay mode (electron emission) is called either an autoionizing or an Auger transition, depending on whether the quasi-discrete state is caused by only an excitation of one or more electrons or by ionization of at least one electron (in an inner-shell). Quasidiscrete states of a negative ion (autodetaching states) decaying by electron emission into the continuum of the neutral atom will not be treated in this lecture.