Isomer effects on the total cross section for electron scattering from C₄F₆molecules

Abstract

The absolute total cross section (TCS) for electron scattering from hexafluoro-1,3-butadiene (1,3-C4F6) was obtained in a transmission experiment for electron impact energies from 0.6 to 370 eV. The TCS energy function has two pronounced enhancements separated by a deep minimum located near 2.6 eV: a low-energy hump around 1 eV and a dominant very broad enhancement centred near 30 eV. The 1,3-C4F6 TCS results are compared with the data for hexafluoro-2-butyne (2-C4F6) and the influence of the structural differences on the electron-scattering TCS for isomers of the C4F6 molecule (isomeric effect) is explicitly indicated. The most pronounced role of the molecular geometry on the magnitude and shape of the TCS energy dependence is observed at the lowest energies studied. Above 40 eV the TCSs for both isomers are close to each other. Some conformities of TCSs within a series of perfluorocarbons (C2F4, 1,3-C4F6, C6F6) as well as in a series of their hydrocarbon counterparts (C2H4, 1,3-C4H6, C6H6) are also pointed out and discussed.