Electron impact ionization cross-sections of toluene

Electron impact ionization of toluene is studied using mass spectrometry. Cross-sections for the formation of molecular ions and ionic fragments are measured between 10 and 78 eV with a total cross-section of 1.5 × 10 - 15 cm 2 towards 60 eV. C 7 H 8 + and C 7 H 7 + contribute to 75% of the total cross-section at 78 eV. The molecular ion is the most abundant below 25 eV. Four ionic fragments: C 5 H 5 + , C 4 H 3 + , C 5 H 3 + and C 3 H 3 + , are detected above 20 eV. Enthalpy considerations can lead to think that C 5 H 5 + is issued directly from the molecular ion, whereas the three other species result from two step pathways.