摘要 : A combination of electron scattering and laser-induced fluorescence (LIF) techniques has been employed in an absolute experimental determination of the N2+ (X 2Σg+) ionization cross section as a function of electron energy from th... 展开 A combination of electron scattering and laser-induced fluorescence (LIF) techniques has been employed in an absolute experimental determination of the N2+ (X 2Σg+) ionization cross section as a function of electron energy from threshold to 200 eV. N2+ ground-state ions, resulting from electron impact on N2, are detected by laser-induced fluorescence of the N2+ X 2Σg+ -> B 2Σu+ transition at 391 nm. The relative ionization cross section obtained from LIF spectra taken at different electron energies is put on an absolute scale by calibration relative to the well known electron-impact cross section for the formation of helium atoms in the 2 3S state from the 1 1S ground state. The He 2 3S atoms are probed via LIF of the 2 3S -> 3 3P transition at 389 nm in the same apparatus using the same detection equipment and laser-induced fluorescence technique at essentially the same wavelength that is used in the measurement of the N2+(X) cross section. The cross section peaks at 60 eV with a maximum value of 80 × 10-18 cm2. At 100 eV, our cross section value is (74.9 ± 7.5) × 10-18 cm2, which is in good agreement with the value of (86.9 ± 7.0) × 10-18 cm2 reported by Doering and Yang (1996 J. Geophys. Res. 102 9683) who used a different experimental technique. 收起