Total Cross Sections for the Excitation of the Triplet States in Molecular Nitrogen

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Abstract
A consistent set of total cross sections for electron impact excitation of the AΣu+3, BΠg3, WΔu3, B′Σu−3, CΠu3, EΣg+3, and DΣu+3 triplet states of molecular nitrogen from the XΣg+1 state has been calculated quantum mechanically for incident electron energies from threshold to 80 eV. The Ochkur-Rudge exchange scattering and Franck-Condon approximations were employed to obtain these cross sections. Minimum and double-minimum basis-set LCAO-MO wave functions centered on the nuclei were used, and the multicenter terms in the scattering amplitude were evaluated using a ζ-function expansion. Rotationally averaged cross sections were calculated for excitation from v′′=0 to individual v′ levels of the excited electronic states. The calculated total cross section for excitation of the BΠg3 state is in good agreement with that deduced from recent experimental data for the process. The cross section for excitation of the CΠu3 state agrees well with one pair of experimental measurements and is a factor of 2 larger than another pair of measurements and about a factor of 4 larger than a fifth experimental determination and the previous calculations. The calculated cross section for excitation of the AΣu+3 state is a good deal larger than previous theoretical and experimental estimates. However, a comparison with recent experimental differential cross-section data indicates that the theoretical AΣu+3 total cross section is correct for incident energies greater than about 35 eV. The relative magnitude of these excitation cross sections leads to interesting predictions concerning N2 processes in the upper atmosphere.