Electron-impact ionisation cross-sections of the CClF3 and CCl3F molecules

An investigation is reported on the absolute partial ionisation cross-sections of the set of ions lay down following the collisions of electrons with CClF3 and CCl3F molecules. Experiments were carried out in a pulsed supersonic expansion inside a time-of-flight mass spectrometer. The electron kinetic energies used were in the 10-100 eV range and the electron and molecular beams arranged to cross at right angle. CF3+ ions for the CClF3 parent molecule and CCl2F+ for the CCl3F are the fragments with highest ionisation cross-sections (ICS). CClF22+ and CF32+ dications are observed in the dissociative ionisation of CClF3 and their contribution to the total ionisation cross-sections is just over 1%; in the case of the CCl3F molecule only the CCl2F2+ double ion appears and its ionisation cross-section is even smaller than those produced by electron impact on CClF3.