auto-ionization 

in mass spectrometry
https://doi.org/10.1351/goldbook.A00526
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.)
Sources:
Orange Book, 2nd ed., p. 206 [Terms] [Book]
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 [Terms] [Paper]
Citation: 'auto-ionization' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.A00526 RIS BibTex EndNote
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Last revised: February 24, 2014