Low-energy electron scattering by CF₃Cl and CF₃Br: elastic scattering and vibrational excitation

Absolute differential cross sections (DCSs) for elastic and vibrationally inelastic scattering of electrons from CF₃Cl and CF₃Br have been determined by a crossed-beam experiment, in the energy range of 1.5–100 eV and over the scattering angles of 15° – 130°. The relative flow method was applied to normalize these cross sections, using helium as a standard. The present results are compared with the previous ones for CF₃H, CF₄ and CF₃I. An effect due to a long-range interaction of polar molecules has been observed in a systematic manner in elastic DCSs below 3 eV. Broad resonance structures where the vibrational cross sections are enhanced are observed at around 7 eV in both CF₃Cl and CF₃Br as experimentally confirmed previously in CF₃H, CF₄ and CF₃I. The continuum multiple-scattering method is also employed to carry out the analysis.