The Laser-Induced Fluorescence Spectrum of Jet-Cooled Diatomic Sulfur in Ultraviolet Region
WANG Shu-long1, 2，XIANG Qian-lan3，ZHAO Dong-mei1，MA Xin-wen1，YANG Jie1*
1. Institute of Modern Physics，Chinese Academy of Sciences，Lanzhou 730000，China
2. University of Chinese Academy of Sciences，Beijing 100039，China
3. Xianyang Normal University，Xianyang 712000，China
Abstract：The time-resolved and vibrational emission-resolved laser-induced fluorescence (LIF) spectra of jet-cooled supersonic diatomic sulfur molecule S2 have been studied in the range of 30 400~34 400 cm-1, and 184 bands were observed with high (0.1 cm-1) and low (0.3 cm-1) resolutions. 84 vibrational transitions were assigned to the Ｂ3Σ-ｕ-Ｘ3Σ-ｇand Ｂ″ 3Πｕ-Ｘ3Σ-ｇ, and the molecular constants in the excited states Ｂ3Σ-ｕν=0～9and Ｂ″ 3Πｕν=2～12, including rotational constants, spin-orbit coupling constants, spin-rotation coupling constants, and spin-spin coupling constants, were obtained. The equilibrium molecular geometry in the vibronic ground state of Ｂ3Σ-ｕ was determined by high-resolution spectrum. As there is perturbation between the Ｂ3Σ-ｕand Ｂ″ 3Πｕ states of S2 molecule, the vibrational level intervals, spin-spin coupling constants and spin-orbit coupling constants of Ｂ3Σ-ｕand Ｂ″ 3Πｕ states are anomalous variation, as well as the intensity of rotational transition and the transition selection rules. The anomalous behavior of the rovibrational spectra was qualitatively explained by the homogeneous perturbations between 3Σ-3Π states.
Key words：Diatomic sulfur molecule；Laser-induced fluorescence spectroscopy；Low energy excited state；Electronic state structure；Homogeneous perturbation
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