A mass spectrometer for the characterization of neutral species produced in the electron bombardment of gases

A mass spectrometer which permits the direct study of neutral species produced by the electron bombardment of gases is described. Functionally, it consists of an ion source with two independent electron beams, a quadrupole mass filter, and a phase-sensitive ion detector. The instrument provides for automatic scanning and recording of mass spectra and ionization efficiency data for the neutral species produced in one electron beam (pulsed at 260 Hz) and subsequently ionized in the other electron beam. The mass spectrum of the neutral species obtained from the electron bombardment of benzene, along with the ionization efficiency data for the neutral species, are presented to demonstrate the quality of the data obtained. (Auth.)