BH分子X 1Σ+、A 1Π和B 1Σ+ 态的势能函数

利用SAC/SAC-CI方法，使用D95++、6-311++g及cc-PVTZ等基组，对BH分子的基态(X ¹Σ⁺)、第一简并激发态(A ¹Π)及第二激发态(B ¹Σ⁺)的平衡结构和谐振频率进行了优化计算． 通过对三个基组计算结果的比较，得出了cc-PVTZ基组为三个基组中的最优基组的结论；使用cc-PVTZ基组，利用SAC的GSUM(group sum of operators)方法对基态(X ¹Σ⁺)， SAC-CI的GSUM方法对激发态(A ¹Π 和B ¹Σ⁺)进行单点能扫描计算, 用正规方程组拟合Murrell-Sorbie函数，得到了相应电子态的完整势能函数；从得到的势能函数计算了与基态(X ¹Σ⁺)、第一简并的激发态(A ¹Π)和第二激发态(X ¹Σ⁺)相对应的光谱常数(Be、αe、ωe 和ωeχe)，结果与实验数据较为一致． 其中基态、第一激发态与实验数据吻合得较好．

Analytical Potential Energy Functions for the Electronic States X 1Σ+, A 1Π and B 1Σ+ of BH Molecule

The energies, equilibrium geometries and harmonic frequencies of three electronic states (the ground state X ¹Σ⁺, the first degenerate state A ¹Π and the second state B ¹Σ⁺）of BH molecule have been calculated using the GSUM (group sum of operators) method of SAC/ SAC-CI with the basis sets D95++, 6-311++g and cc-PVTZ. Comparing among the above mentioned three basis sets, the conclusion is gained that the basis set cc-PVTZ is the most suitable for the energy calculation of BH molecule. The whole potential curves for these three electronic states are further scanned using SAC/cc-PVTZ method for the ground state and SAC-CI/cc-PVTZ methods for the excited states, then having a least square fitting to Murrell-Sorbie function, and last the spectroscopy constants (Be, αe, ωe, andωeχe) are calculated, which are in better agreement with the experimental data. It is believed that Murrell-Sorbie function form and SAC/ SAC-CI method are suitable not only for the ground state, but for the low-lying excited states as well.