Emission cross sections for NI and NII multiplets and some molecular bands for electron impact on N 2

Abstract

Cross sections have been measured for the production of NI and NII multiplets between 500 and 10000 Å and of some a 1Π g−X 1Σ + g and p′ 1Σ + u−X 1Σ + g bands in the vacuum ultraviolet for 0.05-5 keV electrons incident on N 2. Most of the multiplet radiation was present in the vacuum ultraviolet region; considerable cascade contributions were found. The apparent emission cross sections for the a 1Π g−X 1Σ + g and p′ 1Σ + u−X 1Σ + g transitions were pressure dependent even at low gas densities. In the vacuum ultraviolet the cross sections were brought on an absolute scale by means of the branching ratio method for molecules, inelastic scattering data and experimental emission cross sections. At high impact energies (≳ 300 eV) the energy dependence of the cross sections has been analysed by means of the Bethe-Born approximation: for NI it was found that the terms involved were mainly formed via optically allowed excitation processes in the molecule; for NII optically forbidden transitions were dominant. An attempt has been made to correlate the observed dissociation fragments with intermediate molecular states. The electron impact cross sections of this work have been compared with other electron, proton and photon impact data.