Abstract:
An experimental technique is described, and the relative cross sections of the single and dissociative electron-impact ionizations of the freon-12 molecule (CCl$_2$F$_2$) in the near-threshold energy range are obtained. The experiment is performed on a device that provides the mass separation and recording of ions with a monopole mass spectrometer. The mass spectrum of the freon-12 molecule is measured at various ionizing-electron energies, and the relative cross sections of dissociative ionization are measured for the most intense ion fragments, including isotope-containing fragments. The threshold dependences of these cross sections are used to determine the appearance potentials of the ion fragments. The isotope shift in the thresh-old appearance energies of ion fragments [C$^{35}$ClF$_2$]$^+$ and [C$^{37}$ClF$_2$]$^+$ is measured for the first time.
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