Electron attachment to chlorofluoromethanes using the electron-swarm method

Abstract

Electron attachment rate constants, as a function of pressure‐reduced electric field, were measured in mixtures with nitrogen for CCl₃F, CCl₂F₂, and CClF₃ using the electron swarm method. From these data total electron attachment cross sections σ_a(ε) as a function of electron energy ε were determined for the chlorofluoromethanes using the electron‐swarm unfolding technique and a new set of electron energy distribution functions for N₂. For CCl₃F and CCl₂F₂ three maxima in σ_a(ε) were found at thermal energy, 0.25 and 0.75 eV and at 0.07, 0.30, and 0.93 eV, respectively. Only one pronounced maximum in σ_a(ε) for CClF₃ was observed at 1.4 eV. The thermal values of the attachment rate constant for CCl₃F, CCl₂F₂, and CClF₃ are, respectively, 3.90×10⁸, 4.00×10⁷, and 6.05×10³ sec⁻¹ Torr⁻¹. Additionally, comparisons are made between the σ_a(ε) calculated for these and other molecules using both the new electron energy distribution functions for N₂ and those determined earlier. Substituent effects on the number and position of negative ion states and on the magnitude of σ_a(ε) for the chlorofluoromethanes are discussed.