Quadrupole mass spectrometer for the identification and characterization of neutral fragments formed by the interaction of gaseous molecules with electrons

A quadrupole mass spectrometer with a modified ion source and modified ion detection circuitry for identifying and characterizing neutral fragments formed by the interaction of electrons with gaseous molecules is described. The instrument incorporates the capability of automatic scanning and recording of neutral fragment mass spectra and neutral fragment ionization potential and appearance potential curves. The neutral fragment mass spectra were measured and compared with their corresponding positive ion mass spectra. Numerous neutral fragment ionization potentials were also measured and compared with available literature values. In addition, the neutral fragment ionization potentials, for which no literature values were available, were measured and reported.