Threshold phenomena in electron-molecule scattering

The performance of an electron energy loss spectrometer with hemispherical energy selectors has been improved in terms of low energy capacity, resolution, response function correction at low energies, sensitivity, and extension of the angular range to 180 degrees. The extended capacity permitted a more detailed observation of threshold peaks and near threshold structures in halogen halides, observation of near threshold structures in CO2, N2O and CS2 and the observation of selectivity in the excitation of Fermi-coupled vibrations by the (2)Pi(u) shape resonance in CO2.