SO2分子的532nm双光子激发及退激发过程

Process of two-photon excitation and de-excitation of SO_2 molecule in 532 nm

以纳秒Nd:YAG脉冲激光器的2倍频输出532nm激光作为激发源,采用双光子激发激光诱导色散荧光光谱方法对SO2分子第一激发带粒子的荧光辐射与碰撞弛豫相结合的复杂退激发过程进行了实验研究.结果表明,以215,337nm处荧光包络分别归属于C1B2,B1B1基振动能级到基电子态X1 A1不同振动能级的荧光跃迁,而425nm处荧光包络包既包含有a3B1基振动能级向基电子态X1 A1的荧光跃迁,同时还包含有C1B2基振动能级向A1 A2的荧光跃迁;由规则序列的实验数据可以计算出SO2分子相应电子态的对称振动和弯曲振动模式的基振动角频率及非谐性常数.所得结果对大气污染物SO2的探测及分子物理学研究具有重要意义.

The complicated de-excitation process of the first-excited band of SO2 molecule, including fluorescence radiation and collision relaxation, has been studied with the techniques of two-photon laser induced dispersive fluorescence（LIDF） spectroscopy, in which the duple harmonic output （532 nm） of a nan- osecond pulsed Nd： YAG laser was used as excitation sources. The results showed that the fluorescence spectrum envelopes centered in 215 nm and 337 nm in the laser induced dispersive fluorescence spectra （LIDFS） were attributed to transitions to the different vibrational levels of ground electronic state X^1A1 from low vibrational levels of C^1B2 ,B^1B1 and in 425 nm in the LIDFS were attributed to transitions to the different vibrational levels of ground electronic state X^1 A1 from low vibrational levels of a^3 B1 and to the different vibrational levels of electronic state A^1A2 from low vibrational levels of C^1B2. The harmonic fre- quencies of the symmetry stretch vibration and the bend vibration and the anharmonic constants of stretch vibration mode and the bend vibration mode of X^1 A1, C^1 B2, A^1 A2 state were also calculated from the experimental data. The results presented in this paper are believed to be of great important to the detection of SO2 and the study of the molecular physics.