## protonated molecule

in mass spectrometry
https://doi.org/10.1351/goldbook.P04908
An ion formed by interaction of a molecule with a @P04906@ abstracted from an ion, as often occurs in chemical @I03183@ according to the reaction: $$\text{M}+\text{XH}^{+}\rightarrow \text{MH}^{+}+\text{X}$$ . The symbolism [M + H]+ may also be used to represent the protonated molecule. The widely used term 'protonated molecular ion' to describe the MH+ ion is not recommended, since it suggests an associated product of a @P04906@ with a molecular ion.
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 1550 [Terms] [Paper]