Study On Near-infrared Laser Spectroscopy Of O₂～+

Oxygen ion is one of the most important ions in the lower ionosphere, and it has been extensively studied. It exists in the courses of chemical reaction and combustion prevalently. However its presence is difficult to detect because of inherent high reactivity and short lifetime. Its high-resolution spectrum provides extremely reliable means of unraveling the nature of its structure and monitoring the distribution over quantum states. The First Negative band system (b⁴∑_g^- - a⁴∏_u) often happens in the ionization processes of oxygen molecules and in the chemical reaction intermediates of oxidation. It is a quartet transition and 48 branches are involved. The second negative system (A²âˆ_g - X²âˆ_g) is a doublet transition and 12 branches are involved. The superposition of the band system makes the assignment extraordinarily difficult.In this paper, the laser source was a single-mode Ti:sapphire laser (Coherent Ring 899-29) pumped by a compact diode-laser-pumped Nd:YVO₄ laser (Coherent Verdi 10, at 532 nm). The O₂⁺ ion was produced by an ac high voltage Penning discharging the flowing gases of oxygen and helium. The spectrum was calculated adopting the constants obtained by Prasad for the experimental spetral assignment by employing effective Hamilotonian method. About 150 spectral lines of (5, 21) band in the O₂⁺ A²âˆ_u - X²âˆ_g systeim were, for the first time, observed in the region of 11370-11800 cm^-1 using optical heterodyne velocity modulation spectroscopy. A rotational analysis was performed, thus, more precise molecular constants of the lower states X²âˆ_g(v' =21) were obtained employing nonlinear least-squares procedure via diagnalizing the effective Hamiltonian matrices. Additionally, the equilibrium moleculat constants of the ground electronic state (X²âˆ_g) were calculated adopting the obtained molecular contants together with those of previous published.Meanwhile, excluding the spectral lines of the second negative bands, 366 spectral lines in the region of 12200 ～12800 cm^-1 belonging to the (2,7) band in the O₂⁺ b⁴∑_g^- -a⁴∏_u transition were observed for the first time to our knowledge using optical heterodyne velocity modulation spectroscopy. And also more precise molecular constants of the states involved were obtained employing nonlinear least-squares procedure via diagnalizing the effective Hamiltonian matrices.