A process whereby an electron is removed from a molecule in its ground or an
excited state so rapidly that a positive ion is produced without change in the positions or momenta
of the atoms. The resultant ion is often in an
excited 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 1548