Electron-impact ionization of CClF3 and CHClF2: absolute cross sections and fragmentation dynamics

Abstract

We report experimental absolute total and partial ionization cross sections for electron collisions with chlorotrifluorocarbon (CFC-13, CClF₃) and chlorodifluoromethane (HCFC-22, CHClF₂) in the energy range from 20 to 1000 eV. For CClF₃ the ionic fragments CF₃⁺ and CClF₂⁺ were identified to have the highest ionization cross sections, indicating a high release of chlorine and fluorine atoms. CHClF₂ dissociates primarily into C(H)F₂⁺, C(H)ClF⁺, and C(H)Cl⁺ with the release of Cl and/or F atoms. For CHClF₂ single and double charged species, adiabatic ionization and partial potential energy surface calculations were performed to obtain insights into the formation-dynamics of neutral chlorine and fluorine and the pathways for the formation of metastable dications. While CHClF₂²⁺ is formed in a single-step double-electron emission, unstable CClF₃²⁺ dissociates and CClF₂²⁺ is observed. Both metastable dications have a triangular planar-like shape and show enhanced dipole moments.