The Absorption Spectrum In The A²∏_u-X²Σ_g⁺ System Of ¹⁴N₂⁺ Cation

Molecular ions are important in the field of chemistry, physics, astronomy and plasma. The spectrum of molecular ion is also the foundation for many subjects. In the laboratory, transient particles can be obtained through low-pressure glow discharge. The spectra of transient particles are difficult to analysis because of their short lifetime, low density and strong chemical activity.Nitrogen is the most abundant gas in the atmosphere. The molecular ion N2+ exists in the ionosphere of atmosphere, astrospace, combustion process and plasma discharge. The spectrum of N2+is often used in trace gas detection and thus attract wide study.The absorption spectrum of N2+ was measured using Optical Heterodyne Detected Velocity Modulation Laser Spectroscopy (OH-VMS) in the rage from 11 250 cm-1 to 12 900 cm-1. The 986 absorption lines were assigned to the (3,1), (4,2), (5,3), (8,5) bands in the A2Πu-X2Σg+ system. The (5,3) band was studied for the first time. A group fitting was performed including the fourteen bands (0,0), (0,1), (1,0), (1,2), (2,0), (2,5), (3,3), (4,4), (4,0), (6,1), (7,2), (7,4), (8,3), (9,4) bands in literatures together with ours. Totally 3497 lines were fitted to exact 91 molecular constants. The vibration energy levels of A2Πu (v’=0-9) and X2Σg+(v"= 0-5) state were studied to obtain the equilibrium constants.