A hybrid BEQQ mass spectrometer for studies in gaseous ion chemistry

Abstract

A hybrid mass spectrometer of BEQQ geometry (B, magnetic sector; E, electric sector; Q, quadrupole mass filter), designed for fundamental and applied studies in gaseous ion chemistry, is described. The high-resolution (BE) stage is followed by a deceleration lens, which also shapes the ion beam, an r.f.-only quadrupole collision cell, and a quadrupole mass analyzer. This assembly allows collision processes to be studied over the laboratory energy range from 0 to 500 eV with selection of the reactant ion at high mass resolution. The instrument is also equipped with dual collision cells and a deflector electrode in the field-free region between B and E for the study of neutralization—reionization reactions as well as single collision processes at 1–8 keV collision energy. The use of the instrument is illustrated with a variety of examples involving charge stripping, charge inversion, fast neutral ionization, and neutralization—reionization processes at high collision energies, as well as collision-induced dissociation reactions at both high and low collision energies. In addition, a number of experiments involving simultaneous scanning of the electric sector and the QQ stage are reported.