Electron-impact ionisation cross-sections of the CClF 3 and CCl 3F molecules

Abstract

An investigation is reported on the absolute partial ionisation cross-sections of the set of ions lay down following the collisions of electrons with CClF 3 and CCl 3F 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. CF 3 + ions for the CClF 3 parent molecule and CCl 2F + for the CCl 3F are the fragments with highest ionisation cross-sections (ICS). CClF 2 2+ and CF 3 2+ dications are observed in the dissociative ionisation of CClF 3 and their contribution to the total ionisation cross-sections is just over 1%; in the case of the CCl 3F molecule only the CCl 2F 2+ double ion appears and its ionisation cross-section is even smaller than those produced by electron impact on CClF 3.