Cross beam experiment for the scattering of low-energy electrons from methane

Differential scattering for e-CH4 collisions have been investigated with the crossed beam technique in the energy range below 10 eV. Cross sections have been measured for vibrationally elastic ( Delta nu =0) scattering and vibrational excitation. Vibrationally elastic scattering is characterised by a pronounced Ramsauer-Townsend minimum below 1 eV and a broad shape resonance in the 5 eV region, the latter being dominated by the l=2 partial wave. In vibrational excitations a steep onset and a narrow peak are observed at threshold. This feature is interpreted as an experimental evidence, in addition to the case of SF6, for the possibility of threshold structures in non-polar molecules.