Title: electron ionization
Long Title: IUPAC Gold Book - electron ionization
DOI: 10.1351/goldbook.E01999
Status: current

Definition
This is the term used to describe ionization of any species by electrons. The process may, for example, be written:   for atoms or molecules: \[\rm{M} + e \rightarrow \rm{M}^{+\cdot } + 2e\]   for radicals: \[\rm{M}^{\cdot}  + e \rightarrow \rm{M}^{+} + 2e\]   The term 'electron impact' should not be used.

Related Terms
- ionization: https://goldbook.iupac.org//terms/view/I03183
- photoionization: https://goldbook.iupac.org//terms/view/P04620
- radical ion: https://goldbook.iupac.org//terms/view/R05073

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 (https://doi.org/10.1351/pac199163101541)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/E01999/html
- json: https://goldbook.iupac.org/terms/view/E01999/json
- xml: https://goldbook.iupac.org/terms/view/E01999/xml

Citation: Citation: 'electron ionization' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.E01999
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Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-04-20T22:39:23+00:00