Cross section for the production of N2+ (X2 Σg+) ions by electron impact on N2

A combination of electron scattering and laser-induced fluorescence (LIF) techniques has been employed in the direct experimental determination of the N-2(+) (X (2)Sigma(g)(+)) ionization cross section as a function of electron energy from threshold to 200 eV. Electron impact on N-2 produces N-2(+) ground-state ions that are detected by pumping the X (2)Sigma(g)(+) --> B (2)Sigma(u)(+) (0,0) vibrational transition at 391 nm with a tunable dye laser and detecting the subsequent LIF of the B 2 Sigma u+ --> X (2)Sigma(g)(+) (0,1) vibrational transition at 428 nm. LIF spectra obtained at different electron energies yield the relative N-2(+)(X) cross section which is put on an absolute scale by normalization to the absolute cross section value of Doering and Yang [J. Geophys. Res. 102 (1996) 9683] obtained from electron-electron coincidence (e,2e) experiments at 100 eV. (C) 1999 Elsevier Science B.V.