This occurs when an internally supra-excited atom or molecular
moiety loses an electron spontaneously without further interaction with an energy source.
(The state of the atom or molecular
moiety is known as a pre-
ionization state.)
Source:
PAC, 1991, 63, 1541
(Recommendations for nomenclature and symbolism for mass spectroscopy (including an
appendix of terms used in vacuum technology). (Recommendations 1991))
on page 1547