Perturbation Study Via Rotational-resolved Spectrum In The Triplet Band D～3Δ-a～3 Π(2,1) Of CO

Carbon monoxide molecule has been found in extraterrestrial sources and in a variety of experiments indicating it plays significant roles in chemical reaction process, plasma, interstellar matter, biomedicine, environmental science and other fields. Its metastable a³Î  state is the lowest excited state which has been studied by spectroscopy for many years and its configuration is known as (Ï€2p)⁴(σ2p)¹(Ï€*2p)¹. The next-higher configuration, (Ï€2p)³(σ2p)²(Ï€*2p)¹, yields the a³âˆ‘+,d³Î”, e³âˆ‘^-, I¹âˆ‘ and D¹Î” electronic states. As the Ï€2p and σ2p orbitals have similar energies, the triplet states interact reciprocally, giving rise to extensive perturbations. However, it is difficult to observe the triplet band system by conventional absorption speclroscopy due to the small transition probability. The d³Î” and a³âˆ states were usually studied via the d³Î” - X¹âˆ‘+ and a³Î  - X¹âˆ‘+ transitions instead of their direct transition.In this thesis, the metastable state of CO molecule was produced in an ac glow discharge plasma of carbon monoxide with helium as the carrier gas, and its d³Î” - a³âˆ (2, 1) absorption spectral band in the near infrared region was directly observed by employing the optical heterodyne magnetic rotation enhanced concentration modulation spectroscopic (OH-MR-CMS) technique with high signal to noise ratio, typically over 100. 562 lines were assigned to the (2, 1) band of the CO triplet d³Î” -a³âˆ system, among which 45 perturbed lines were firstly observed. The perturbations occur in the d³Î”₂ and a³âˆ₁ states at J = 6 and 7, in the d³Î”₂ and a³âˆ₀ states at J = 15, in the d³Î”₂ and a³âˆ₁ states at J = 14, in the d³Î”₂ and a³âˆ₂ stales at J = 6 and 7, and in the d³Î”₁ and a³âˆ₂ states at J = 13 and 14. It is worthy of noting here that these are observed directly in the experiment for the first time except the first one.In conclusion, the comprehensive perturbation analysis between the d³Î” (v = 2) and a³âˆ (v == 9) states was performed and a set of more precise molecular constants including those perturbation parameters was derived as well by a nonlinear least-squares procedure.