Comparison of the electron impact cross section for the N-2+ first negative (0,0) band (lambda 3914 angstrom) measured by optical fluorescence, coincidence electron impact, and photoionization experiments

The cross-section for production of the N-2(+) B-2 Sigma(u)(+) state by electron impact on N-2 is one of the most important cross-sections for aeronomy because of the prominence of the N-2(+) first negative (0,0) band (B-2 Sigma(u)(+) <-- X(2) Sigma(g)(+), lambda 3914 Angstrom) in the dayglow and aurora. Recently developed electron-electron coincidence experiments have made possible the measurement of the branching ratios for ionization-excitation of N-2 by electron impact at the 100-eV maximum of the cross-section. The N total ionization cross-section, measured in other experiments, can then be used to calculate the cross-section for production of the N-2(+) B-2 Sigma(u)(+) state at 100-eV. Photoionization partial cross-sections and branching ratios from high-energy electron impact experiments are used to calculate the N-2(+) B-2 Sigma(u)(+) cross-section at 2000-eV. The 100- and 2000-eV results are compared with cross-sections from electron impact optical emission experiments at the same incident energies. The cross-sections from electron impact and photoionization experiments are 30% smaller than the optical emission cross-section of Borst and Zipf at both 100-eV and 2000-eV incident energies but within 20% of the results of the most recent optical measurement at 100-eV. A value of 14.8 x 10(-18) cm(2) for the N-2(+) B-2 Sigma(u)(+) first negative (0,0) band cross-section maximum at 100-eV is within the error bars for all the experimental measurements except one.