Electron-impact excitation of acetylene above 12 eV

Electron-energy-loss spectra have been measured for the acetylene molecule (X ${}_{}{}^1{}_{}{}^{}\Sigma _g^{+}{}_{}{}^{}$) in the angular range of 1°–7°. The incident energy was 1 keV, the excitation energy range was 0–50 eV, and the energy resolution was 0.6 eV (full width at half maximum). Special attention has been given to the broad and intense structures appearing at 13.3 and 15.7 eV, which have been recently studied by photoionization techniques. The generalized oscillator strengths for these transitions have been determined and extrapolated to the optical oscillator strengths. Their values are 0.21±0.03 and 0.54±0.08, respectively. A new electronic transition has also been observed at 18.7 eV.