The ratio of the maximum ion current recorded at a mass \(m\) to the ion current arising from the same species recorded at an adjacent mass (\(m\pm 1\)).
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 1554 [Terms] [Paper]