Angular distribution of N+ from dissociative ionization of N2 near threshold

Abstract

Translational kinetic energy and angular distributions of N⁺ from dissociative ionization of N₂ have been measured at electron energies close to threshold. For electron energies above 50 eV the energy distributions agree favorably with earlier measurements of Kieffer and Van Brunt. The ion energy distributions at electron energies below 50 eV are dominated by a feature peaked at a kinetic energy below 1 eV in agreement with recent measurements of Locht et al. For electron energies closest to threshold the angular distribution of N⁺ associated with this feature is consistent with the previously proposed mechanism involving excitation of the C ²Σ⁺_u state followed by predissociation. At higher electron energies the degree of anisotropy increases and then rapidly decreases suggesting a significant contribution from direct excitation to the ⁴Σ⁺_g repulsive state of N⁺₂ leading to fragments in their ground states.