Photofragment spectroscopy of N 2 + in the near UV

Photofragment spectroscopy of N ₂ ⁺ has been studied in the wavelength range 343–404 nm using an excimer-pumped dye laser with a spectral resolution of 0.2 cm^?1. The observed bands are assigned to transitions from thev″=23?26 levels of theX ²Σ _g ⁺ state to highlying rovibrational levels (v′≈46–48) of theB ²Σ _u ⁺ state, forming quasibound (predissociating) states above the dissociation limit N⁺(³ P)+N(⁴ S ⁰). Measurement of the photofragment kinetic energies allows to establish an absolute energy scale for the transitions with respect to the dissociation limit. Molecular constants for the lower and upper states of the observed transitions are determined. The measurements allow the first direct determination of the N ₂ ⁺ dissociation energyD ₀ ⁰ (N ₂ ⁺ ). Some high-resolution (0.04 cm^?1) measurements show the fine-structure splitting and lifetime broadening of the excitation lines.