Resonance phenomena in electron-ion and photon-ion collisions

Abstract

Intermediate autoionizing states can be formed during electron-ion and photon-ion collisions. Depending on the decay of these multiply excited states by electron and/or photon emission the associated indirect processes can contribute to net electron-ion recombination, elastic or ineleastic electron scattering, to excitation, to single or to multiple ionization of the initial ion. Intermediate states give rise to distinct features in the associated cross sections and, in particular, narrow resonances can occur. These sharp features facilitate access to level energies and transition rates of ions from which detailed information about quantum electrodynamic, relativistic, nuclear, and field effects can be extracted.