An ion formed either when a chemical species exists in the vapour as a dimer and can be detected as such, or when a molecular ion can attach to a neutral molecule within the ion source to form an ion such as
[M2]+.
where M
represents the molecule.
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
Transformed and rewritten from PDF version (entry
http://www.iupac.org/goldbook/D01743.pdf)
by: Miloslav Nic, Jiri Jirat, Bedrich Kosata, ICT Prague, Czech Republic