Electron impact dissociative ionization of the CH₂F₂molecule: cross sections, appearance potentials, nascent kinetic energy distributions and dissociation pathways

Abstract

Ions produced by crossed-beam collisions of pulsed monoenergetic electrons and supersonic expansion molecules have been analysed by time-of-flight mass spectroscopy (TOF-MS) in order to determine the appearance potentials, absolute total, dissociative and parent ionization cross sections and nascent ion kinetic energy distributions. The electron impact study was conducted at incident electron energies up to 100 eV on the parent CH2F2 molecule (and Ar/CH2F2 mixtures), a fluoromethane where the CH2F+ ion is produced at higher yields (1:18) than the parent molecule ion, CH2F2+. TOF-MS band profiles analysis has enabled us to determine the ions' nascent kinetic energy distributions, information that combined with the dissociative ionization appearance potentials, calculated molecular orbital energies and orbital bond characters, leads to improved identification of the electron impact dissociative channels.