Derivations of the field equations and stability parameters for three operating modes of the three-dimensional quadrupole

Abstract

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, φ0, is applied to the ring electrode and -φ0 to the end caps. II. Simple: φ0 is applied to the ring and the end-caps are earthed. III. A new mode in which the dc component of φ0 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.