An atom, radical, molecule or molecular
moiety in the vapour phase which has gained one or more electrons thereby acquiring an electrically
negative charge. The use of the term
anion as an alternative is not recommended because of its connotations in solution chemistry.
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 1549