Absolute partial and total electron ionization cross sections for CCl4 from threshold up to 180 eV

Electron impact ionization of carbon tetrachloride was studied as a function of electron energy from threshold up to 180 eV. A double-focusing mass spectrometer system in combination with an improved electron impact ion source was used, alleviating the problems of ion extraction from the source and the transmission of the extracted ions through the mass spectrometer system. Absolute partial ionization cross sections for the occurrence of CCl₃⁺, CCl₂⁺, CCl⁺, Cl₂⁺, Cl⁺, C⁺, CCl₃²⁺, and CCl₂²⁺ have been determined. In addition, the total ionization cross-section function of CCl₄ is reported and compared with theoretical predictions based on a classical binary encounter approximation. Using nth root extrapolation the following ionization energies of the doubly ionized fragment ions have been derived: AE(CCl₃²⁺)=30.4±0.3 eV; and AE (CCl₂²⁺)=31.8±0.3 eV. In accordance with theoretical predictions and previous results, no stable CCl₄⁺ has been detected, however, metastable dissociation processes CCl₄⁺ CCl₃⁺ have been observed.