中文摘要：

获得了硫脲在水和乙腈溶液中A吸收带的芪振拉曼光谱，通过B3LYP／6-311＋＋Gf3df，3pd）和RCIS／6．311＋＋G（3df,3pd）分别对硫脲的电子跃迁和2^1A激发态鞍点结构进行了研究．对共振拉曼光谱进行了归属，并通过含时波包理论对吸收光谱和芪振拉曼光谱进行拟合，结果表明硫脲动态结构特征主要沿着：c=s伸缩振动v6（｜△｜=0．95）、H5N3H6＋H8N4H7弯曲振动v5（｜△｜=0．19）、NCN对称伸缩振动＋C=S伸缩振动＋N3H6＋H8N4弯曲振动1／4（｜△｜=0．18）．v15倍频2v15和4v15强度主要归因于v15激发态频率的改变而不是简正模位移量的变化．对S=CN2面外变形振动V15倍频出现的机理进行了探究，结果表明Franck-Condon区域势能面鞍点是标准A项共振拉曼散射里的二次声子机制的驱动力，导致碳原子中心的锥形化，并使硫脲在20A激发态发生几何结构扭曲．

英文摘要：

The A-band resonance Raman spectra of thiourea were obtained in water and acetonitrile solution. B3LYP/6-311＋＋G（3df,3pd） and RCIS/6-311＋＋G（3df,3pd） calculations were done to elucidate the ultraviolet electronic transitions, the distorted geometry structure and the saddle point of thiourea in 21A excited state, respectively. The resonance Raman spectra were assigned. The absorption spectrum and resonance Raman intensities were modeled using Heller＇s time-dependent wavepacket approach to resonance Raman scattering. The results indicate that largest change in the displacement takes place with the C--S stretch mode u6 （｜△｜=0.95） and noticeable changes appear in the H5N3H6＋H8N4H7 wag v5 （｜△｜=0.19）, NCN symmetric stretch~-C--S stretch＋N3H6＋H8N4 wag v4 （｜△｜=0.18）, while the moderate intensities of 2-15 and 4-15 are mostly due to the large excited state frequency changes of v15, but not due to its significant change in the normal mode displacement. The mechanism of the appearance of even overtones of the S-CN2 out of plane deformation is explored. The results indicate that a Franck-Condon region saddle point is the driving force for the quadric phonon mechanism within the standard A-term of resonance Raman scattering, which leads to the pyramidalization of the carbon center and the geometry distortion of thiourea molecule in 21A excited state.