Electron scattering from C4H6 and C4F6 molecules

Absolute electron-impact total cross sections (TCSs) for C4H6 isomers (1, 3-butadiene and 2-butyne) and for hexafluoro-2-butyne (C4F6) have been,measured in a linear electron-beam transmission experiment as a function of impact energy, between 0.5 and 370 eV For the C4H6 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 C4H6 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.