Study On The First Negative Band (b～4∑～-_g-a～4Π_u)of O～+₂ Using The Velocity Modulation Spectroscopy Combined With The Optical Heterodyne

Oxygen ion is one of the most important and special ions in the lower ionosphere, and it has been extensively studying. 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. However, the first negative system is a quartet transition and 48 branches are involved, which 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 the ac Penning discharge with high voltage in flowing gases of oxygen and helium. About 200 spectral lines in the region of 13170-13500 cm^-1 belonging to 33 branches of the (2,6) band in the O₂⁺ b⁴∑_g^-- a⁴∏_u transition were observed for the first time to our knowledge using optical heterodyne velocity modulation spectroscopy. A rotational analysis was performed, thus, more precise molecular constants of the both states involved were obtained employing nonlinear least-squares procedure via diagnalizing the effective Hamiltonian matrices.Furthermore, the RKR potential curves of both the a and b quartet states of O₂⁺ were derived based on the latest equilibrium constants and Franck-Condon factors were listed in this thesis as well.