Absolute total cross sections (TCSs) for electron scattering from two C3H4 isomers (allene and propyne) and from propane (C3H8) have been measured in a linear electron-beam transmission experiment for impact energy ranging from 0.5 to 370 eV. Low-energy TCS functions for C3H4 are dominated by prominent structures: a resonant-like enhancement of the cross section for allene peaks at around 2.3 and 3.4 eV for propyne, while very broad enhancement is centred at 9.5–10 and 8.0–8.5 eV for allene and propyne respectively. Some supplementary weak features are also discernible. The general shape of cross sections for both C3H4 isomers is similar except that the cross section enhancements are at different locations. In addition, the TCS for propyne has been compared with cross sections for other open-chain hydrocarbons with three carbon atoms, i.e. propene (C3H6) and propane (C3H8), and the effect of the multiplicity of the C–C bond on the low-energy scattering is demonstrated.

Absolute electron-impact total cross sections (TCSs) for C 4 H 6 isomers (1, 3butadiene and 2-butyne) and for hexafluoro-2-butyne (C 4 F 6) have been measured in a linear electron-beam transmission experiment as a function of impact energy, between 0.5 and 370 eV. For the C 4 H 6 molecule distinct differences in the shape and magnitude of TCS energy dependences of both isomers are apparent at low energies. In the 1, 3-butadiene TCS curve, the enhancement below 1.2 eV, the narrow maximum centred around 3.2 eV and the dominant broad peak at 9-9.5 eV are easily distinguishable; a very weak shoulder is located near 8 eV. The TCS energy function of 2-butyne demonstrates a remarkable resonant-like maximum located near 3.6 eV and much broader enhancement centred at 8 eV. Above 50 eV both C 4 H 6 curves merge together. The hexafluoro-2-butyne TCS has the maximum near 8 eV and very broad enhancement spanning between 20 and 80 eV; weak shoulders near 3 and 6 eV are also noticeable. The effect of perfluorination is indicated.

The absolute total cross section (TCS) for electron scattering from hexafluoro-1,3-butadiene (1,3-C 4 F 6) 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-C 4 F 6 TCS results are compared with the data for hexafluoro-2-butyne (2-C 4 F 6) and the influence of the structural differences on the electron-scattering TCS for isomers of the C 4 F 6 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 (C 2 F 4 , 1,3-C 4 F 6 , C 6 F 6) as well as in a series of their hydrocarbon counterparts (C 2 H 4 , 1,3-C 4 H 6 , C 6 H 6) are also pointed out and discussed.