中文摘要：

依据Jahn-Teller效应理论与量子理论,利用群论和对称性分析的方法探讨了C42＋分子的Eg b1g系统的Jahn-Teller效应及其各向异性现象,构建了Eg b1g系统的电声耦合哈密顿量,借助幺正平移变换计算出了系统的电子基态与激发态及其能量.结果表明,由于电声耦合作用的缘故,系统发生了Jahn-Teller畸变,畸变使得系统在其势能面上形成了两个具有D2h对称性势阱.无论系统处在哪一个势阱中,系统的二重简并的电子基态能级都将发生分裂,因此畸变导致系统电子基态的简并性完全被消除.经过Jahn-Teller畸变,C42＋分子就会从D4h对称性降低到D2h对称性,同时C42＋分子的振动频率发生分解,频率的分解就意味着C42＋分子的各向同性遭到破坏而呈现出各向异性.

英文摘要：

Based on Jahn-Teller effect theory and quantum theory,the Jahn-Teller effect and anisotropic phenomena of the Eg b1g system for C2＋4 molecules are discussed in this paper using the methods of group theory and symmetry analyses.The vibronic Hamiltonian of the Eg b1g system is constructed,the ground electronic states and their energies of the system in each minimum are obtained using unity shift transformation,and the excited electronic states and their energies in each minimum are also derived further.It is found that there are two potential energy minima on the potential energy surface of the system because of the vibronic coupling.No matter which minimum the system is in,the original 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 completely lifted.The distortion should cause that the symmetry of C2＋4 molecules is lowered to D2h from D4h and the vibrational frequencies of C2＋4 molecules is split.The anisotropy of C2＋4 molecules should appear after the Jahn-Teller distortion.