中文摘要：

依据杨-泰勒效应理论,利用群论和对称性分析的方法探讨了具有Td对称性构型的C42＋分子的Tt2系统的杨-泰勒效应.利用幺正平移变换将这一系统变换到了无声子激发的空间中,由此计算出了杨-泰勒畸变之后系统的基态与激发态及其能量.利用群论进一步探讨了C42＋分子的杨-泰勒畸变方向与能级分裂.结果表明,由于电声耦合作用的缘故,在系统的势能面上形成了4个对称性为C3v的势阱.无论系统处在哪一个势阱中,系统的三重简并的能级都会分裂成两条能级,其中一条非简并的能级是系统的基态,另一条二重简并的能级是系统的激发态.C42＋分子的杨-泰勒畸变方向是Td→C3v,其能级T2的分裂方式为T2→A1＋E.而且系统的能级分裂大小会随着其电声耦合强度的增大而增大.

英文摘要：

According to the theory of the Jahn-Teller effect,the Jahn-Teller effect of the Tt2 system for C42＋ molecules with Td symmetry configuration is studied in this paper using the methods of group theory and symmetry analyses.The ground states and the excited states and their energy of the system in all minima are obtained using unitary shift transformation,it is found that there are four minima on the potential energy surface of the system because of the vibronic coupling.No matter which minimum the system is in,the ground energy level of the system is split into two energy levels after the Jahn-Teller distortion and the electronic degeneracy of the system is partly lifted.The distortion direction and the energy level splitting of the system are further studied using group theory,it is found that the distortion direction for C42＋ molecules should be Td→C3v,and the fission pattern of the electronic state T2 is T2→A1＋E.The greater the vibronic coupling of the system is,the greater the energy level fission after the distortion is.