E/2 mass spectrum

https://doi.org/10.1351/goldbook.M03751
Processes of the charge-
stripping
type: M++XM2++X+e occuring in a collision cell (containing a gas, X) located in a field-free region preceding a magnetic and electric sector combination placed in either order, may be detected as follows. If the instrument slits are wide and if the electric sector field E is set to half the value required to transmit the main ion-beam, the only ions to be transmitted will be those with a
kinetic energy
/charge ratio half, or almost exactly half, that of the main ion beam. The product ions of the charge-
stripping
process fulfil this condition. If the magnetic field B is scanned, a mass spectrum of such doubly-charged product ions, and thus of their singly-charged precursors, is obtained. Such a spectrum is called an E2 mass spectrum. Interference from product ions from processes of the type: M1++XM2++X+M3 where m1, m2, and (m1m2) are the masses of M1+, M2+ and M3, respectively, and where m2=0.5 m1, can arise in E2 mass spectra.
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 1552 [Terms] [Paper]