E2 mass spectrum

Processes of the charge-stripping type:

$M + + X → M 2 + + X + e$

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 $E 2$ mass spectrum. Interference from product ions from processes of the type:

$M 1 + + X → M 2 + + X + M 3$

where $m 1$ , $m 2$ , and ( $m 1 − m 2$ ) are the masses of $M 1 +$ , $M 2 +$ and $M 3$ , respectively, and where $m 2 = 0.5 m 1$ , can arise in $E 2$ 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