Low-Energy, Large-Angle Electron-Impact Spectrum of Ethylene

The electron-impact spectrum of ethylene has been measured at primary energies of 35, 50, and 70 eV and a fixed scattering angle of 90°. The most intense inelastic peak was found to be at 8 eV. This peak corresponds to a number of unresolved allowed transitions which are observed in the vacuum-ultraviolet absorption spectrum. A peak was observed at 4.6 eV which was assigned to a forbidden singlet—triplet transition. The 6.5-eV ``ultraviolet mystery band'' transition was not observed. Neither was any peak observed in the spectrum which could be assigned to a large inelastic process at the ionization limit.