紫外光区S2分子激光诱导荧光光谱

摘要

利用真空脉冲放电超声射流气体束(H2 S/Ar~3%混合气体)的方法产生了气相S2分子,并研究了30400~34400 cm-1范围内S2分子的时间分辨和基态振动频率分辨的激光诱导荧光光谱,获得了184支谱带的高分辨率(0.1 cm-1)和低分辨率(0.3 cm-1)转动光谱.实验观测并归属了S2分子BΣ-u-X 3Σ-g和B″3Πu-X 3Σ-g共84支振动跃迁,分析得到了激发态B 3Σ-u态ν=0~9和B″3Πu态ν=2~12的分子常数以及B 3Σ-u态的基态平衡分子构型.由于S2分子B 3Σ-u与B″3Πu态之间存在微扰,这两个电子激发态的振动能级间隔、自旋分裂常数和自旋-轨道分裂常数变化不规律,转动跃迁强度和跃迁选择定则存在异常,利用3Σ-3Π的齐次微扰哈密顿量定性地对这些异常光谱进行了解释,进一步丰富了S2分子紫外区低能电子激发态的信息.%The time-resolved and vibrational emission-resolved laser-induced fluorescence (LIF)spectra of j et-cooled supersonic diatomic sulfur molecule S2 have been studied in the range of 30400~34400 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 B 3Σ-u -X 3Σ-g and B″3Πu-X 3Σ-g ,and the molecular constants in the excited states B 3Σ-uν=0~9 and B″3Πuν=2~12,including rotational constants,spin-orbit cou-pling constants,spin-rotation coupling constants,and spin-spin coupling constants,were obtained.The equilibrium molecular geometry in the vibronic ground state of B 3Σ-u was determined by high-resolution spectrum.As there is perturbation between the B 3Σ-u and B″3Πu states of S2 molecule,the vibrational level intervals,spin-spin coupling constants and spin-orbit coupling constants of B 3Σ-u and 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 perturba-tions between 3Σ-3Πstates.