Derivations of the field equations and stability parameters of a quadrupole ion trap, operating in different modes, are given in detail and discussed. The modes considered are: I. Conventional, analogous to the mass filter: a combination voltage, ??0, is applied to the ring electrode and -??0 to the end caps. II. Simple: ??0 is applied to the ring and the end-caps are earthed. III. A new mode in which the dc component of ??0 is applied to the end-caps and the rf component to the ring. Possible applications of mode III to studies of ion-molecule reaction pathways are also given. ?? 1977.
Bonner, R. F. (1977). Derivations of the field equations and stability parameters for three operating modes of the three-dimensional quadrupole. International Journal of Mass Spectrometry and Ion Physics, 23(4), 249–257. https://doi.org/10.1016/0020-7381(77)87002-2