Production of electronically excited N₂⁺ ions by electron impact on N₂ molecules

Measurements of the optical emission cross sections for the N₂⁺ D² Π_g→A ²Π_u emission bands produced by electron impact on N₂ are reported. From these optical data, estimates of the apparent cross sections for the electron-impact production of N₂⁺ (D ²Π_g) in the vibrational states v=4, 7, and 9 are obtained. Combining these data with similar cross sections for the ²Π_u→X ²Σ_g⁺ and ²Σ_u⁺→X ²Σ_g⁺ bands and with ionization cross sections of N₂ enables us to analyze the systematics of the cross sections for producing N₂⁺ in the X ²Σ_g⁺, A ²Π_u, ²Σ_u⁺, and D ²Π_g states. Two different kinds of excitation behaviors are found and are discussed in reference to the electronic structure of the N₂⁺ ion.