Rotational Analysis of A²Π_u-X²Σ⁺_g System of ¹⁴N₂⁺

The absorption spectrum of N₂⁺ has been studied using optical-heterodyne velocity mod-ulation spectroscopy in the near-infrared region. The observed spectral lines were assigned to the (3,1), (4,2), (5,3), (8,5) bands of the A²Π_u-X²Σ⁺_g system and the line lists were provided. The (5,3) band was studied for the first time. Fourteen rotational-resolved bands in literatures were fitted together with our observed bands and the molecular constants were obtained for υ_A=0-9 and υ_X=0-5.