Autoionization is a process by which atoms or molecules spontaneously transition from an electrically neutral state to a lower-energy ionized state.

Atoms can autoionize when the two outer electrons are both excited and, through electrostatic interactions, one of the electrons is ejected, ionizing the atom.

For an example of molecular autoionization, see self-ionization of water.

Other examples are given by the autoionization of core-excited molecules, see Auger effect, or of Rydberg atoms.

Autoionizing states are resonances.

More specifically, autoionization refers to non-redox ionization of a molecular substance. See molecular autoionization

See also

• resonance

Atomic physics | Molecular physics | Quantum chemistry | Spectroscopy