## Wikipedia - Molekül molecular ion

in mass spectrometry
https://doi.org/10.1351/goldbook.M03988
An ion formed by the removal from (positive ions) or addition to (negative ions) a molecule of one or more electrons without @F02506@ of the molecular structure. The mass of this ion corresponds to the sum of the masses of the most abundant naturally occuring @I03331@ of the various atoms that make up the molecule (with a correction for the masses of the electron(s) lost or gained). For example, the mass of the molecular ion of ethyl bromide C2H579Br will be $$2\times 12$$ plus $$5\times 1.0078246$$ plus 78.91839 minus the mass of the electron ($$m_{\text{e}}$$). This is equal to $$107.95751\ \text{u}-m_{\text{e}}$$, $$u$$ being the @U06554@ based on the standard that the mass of the isotope 12C = $$12\ \text{u}$$ exactly.
Sources:
Orange Book, 2nd ed., p. 205 [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]