Emission of Radiation in the Vacuum Ultraviolet by Impact of Electrons on Carbon Monoxide

We have measured relative cross sections for emission of radiation in the vacuum ultraviolet in the case of 0.1–5-keV electrons on CO. The molecular transitions studied are the fourth positive band system A 1Π−X 1Σ+ and the Hopfield–Birge band systems B 1Σ+−X 1Σ+ and C 1Σ+−X 1Σ+. Absolute values for the cross sections are obtained by normalization on those evaluated from inelastic scattering experiments of Lassettre and co-workers. The apparent cross sections for the transitions which combine with the zero vibrational level of X 1Σ+ are found to depend strongly on the gas pressure. This is probably caused by trapping of resonance radiation. There are indications in our results, that the electronic transition moment is not constant for the different transitions in the fourth positive band system. Dissociative excitation processes have been studied by observation of atomic radiation of fragment atoms and ions. Applications in the intensity calibration in the vacuum ultraviolet wavelength region are discussed.