Na_2分子X^1Σ_g^+,A^1Σ_u^+和B^1Π_u态的势能函数

Potential Energy Curves of Electronic States X^1Σ_g^+,A^1Σ_u^+ and B^1Π_u of Molecule Na_2

使用SAC/SAC-CI方法,利用6-311++g,6-311g**及cc-PVTZ等基组,对Na2分子的基态(X1Σg+)、第一激发态(A1Σu+)和第二激发态(B1Πu)的平衡结构和谐振频率进行计算.通过对3个基组的计算结果的比较,得出6-311g**基组为3个基组中最优基组的结论;使用6-311g**基组,分别利用SAC的GSUM(Group Sum of Operators)方法对基态(X1Σg+),SAC-CI的GSUM方法对激发态(A1Σu+)和(B1Πu)进行单点能扫描计算,用正规方程组拟合Murrell-Sorbie函数,得到相应电子态的完整势能函数.用得到的势能函数计算与基态(X1Σg+),第一激发态(A1Σu+)和第二激发态(B1Πu)相对应的光谱常数(Be,αe,ωe和ωeχe),结果与实验数据基本吻合.

The energies, equilibrium geometries and harmonic frequencies of X^1∑g^＋ , A^1∑u^＋ and B^1Ⅱu, of molecule Na2 are calculated by the GSUM （Group Sum of Operators） method of SAC/SAC-CI using basis sets 6 - 311 ＋＋ g, 6 - 311g^＊＊ and cc-PVTZ. It is found that 6 - 311g^＊＊ is suitable for energy calculation of molecule Na2. The potential curves of ground states and excited states are scanned by the SAC/6 - 311 g^＊＊ and SAC-CI/6 - 311g^＊＊ methods, respectively. A least square is fitted to a Murrell-Sorbie function.The spectroscopy constants （ Be, ae, ωe, and ω eXe ） are calculated and show good agreement with experiment. It is believed that Murrell-Sorbie function and the SAC/SAC-CI method are suitable for ground states and for low-lying excited states as well.