Hazra Montu K, Samanta Amit K, Chakraborty Tapas
Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India.
J Chem Phys. 2006 Dec 7;125(21):214302. doi: 10.1063/1.2363993.
The vibronically resolved electronic spectra for S(1)<-->S(0) transitions of a mixed dimer between 2-pyridone (2PY) and formamide have been measured in a supersonic free jet expansion using laser-induced fluorescence spectroscopy. Quantum chemistry method at different levels of theory has been used to optimize the geometries of the dimer for the S(0) and S(1) electronic states and also to calculate the normal vibrational modes. Assignments for the vibronic bands observed in the dispersed fluorescence spectrum of the 0(0) (0) band have been suggested with the aid of the ground state frequencies calculated by density functional theoretical method. Spectral analysis reveals that electronic excitation causes extensive mixing of the low-frequency intermolecular vibrational modes of the dimer with some of the intramolecular modes of the 2PY moiety. This spectral behavior is consistent with the complete active space self-consistent field theoretical prediction that with respect to a number of geometrical parameters the dimer geometry in S(1) is significantly distorted from the geometry of the S(0) state.
利用激光诱导荧光光谱法，在超声速自由射流膨胀中测量了2-吡啶酮（2PY）与甲酰胺混合二聚体S(1)<-->S(0)跃迁的振动电子分辨电子光谱。采用不同理论水平的量子化学方法优化了二聚体在S(0)和S(1)电子态的几何结构，并计算了其正常振动模式。借助密度泛函理论方法计算的基态频率，对0(0) (0)带的色散荧光光谱中观察到的振动电子带进行了归属。光谱分析表明，电子激发导致二聚体的低频分子间振动模式与2PY部分的一些分子内模式发生广泛混合。这种光谱行为与完全活性空间自洽场理论预测一致，即相对于一些几何参数，S(1)中的二聚体几何结构与S(0)态的几何结构有显著扭曲。
