Li2分子自旋一致激发态a3Σ+u和b3Πu的分析势能函数的从头算

使用对称性匹配簇-组态相互作用方法首次计算了Li₂分子自旋一致激发态a³Σ⁺_u和b³Π_u的离解能、平衡几何及其谐振频率。使用最小二乘法、利用Murrell-Sorbie函数形式拟合出了Li₂分子三重态的第一激发态a³Σ⁺_u 和第二激发态b³Π_u的完整势能函数，并计算了这两个态的光谱常数 (B_e, α_e, ω_e 和 ω_eχ_e) 和力常数 (f₂, f₃和f₄)。得到了Murrell-Sorbie函数形式既适用于基态、又适用于激发态的结论。将计算得到的激发态（a³Σ⁺_u和b³Π_u）的离解能、平衡几何及其谐振频率与实验结果及其它理论计算结果进行了比较。从比较的结果中可以清楚地看出，本文的计算结果在计算精度方面有很大的改进。

Ab initio calculation on the analytic potential energy functions for the state a3Σ+u and the state b3Πu of spin-aligned trimer3Li2

The energies, equilibrium geometries and harmonic frequencies of the triplet excited states (a³Σ⁺_uand b³Π_u of spin-aligned trimer ⁷Li₂ are firstly calculated by using a symmetry adapted cluster-configuration interaction method. The potential curves for the two excited states have least squares fitted by the Murrell--Sorbie function.The spectroscopic data (B_e, α_e, ω_e , and ω_eχ_e) and the force constants (f₂, f₃ and f₄ are calculated. It is found that the spin-aligned triplet excited state b³Π_u is more stable than the ground state X¹Σ⁺_g, and that the Murrell--Sorbie function form is suitable not only for the ground state but also for the spin-aligned triplet excited states. Comparison between the theoretical determinations of dissociation energies, equilibrium interatomic distances and harmonic frequencies with the experimental data about a³Σ⁺_u and b³Π_u clearly shows that the present work represents a significant improvement in agreement between theories and experiments.