negative ion

in mass spectrometry
https://doi.org/10.1351/goldbook.N04098
An atom, radical, molecule or molecular @[email protected] in the vapour phase which has gained one or more electrons thereby acquiring an electrically negative charge. The use of the term @[email protected] as an alternative is not recommended because of its connotations in solution chemistry.
See:
positive ion (in mass spectrometry)
Sources:
Orange Book, 2nd ed., p. 204 [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 1549 [Terms] [Paper]