Na_2~+离子较低电子态势能曲线和光谱常数的理论研究

通过多组态相互作用方法,结合原子有效芯势与极化势,利用非收缩的高斯基函数,计算了Na_2~+分子对应最低9个解离限的36个电子态的势能曲线.基于计算获得的束缚态势能曲线,拟合给出了相应的光谱常数,并与已有的实验和理论结果进行了比较.同时,给出了部分电子态的振动-转动能级和一些同类态避免交叉点的信息.计算获得的光谱信息对冷原子分子光谱与动力学的研究具有参考价值.

Theoretical study on potential curves and spectroscopic constants of low-lying electronic states of Na2+ cation

In this paper, high-level ab initio calculations by using multi-configuration self-consistent field method with atomic effective core potential, polarization potential, and uncontracted Gaussian basis function, are performed to compute the potential energy curves of a total of 36 low-lying ∧-S states with ∑_g,u, Π_g,u, △_g,u symmetries of Na₂⁺ cation associated with the lowest 9 dissociation limits Na (3s, 3p, 4s, 3d, 4p, 5s, 4d, 4f, 5p)+Na⁺. On the basis of the potential energy curves, the spectroscopic constants (T_e, R_e, ω_e, ω_eχ_e, B_e, α _e, D_e) of the bound states are determined, which are in good agreement with the existing available experimental and theoretical values. Our results indicate that 5²∑_g⁺-7²∑_g⁺, 3²∑_u⁺-7²∑_u⁺, 2²Π_g, 4²Π_g, 1²△_u and 2²△_u states are repulsive, which supports Berriche's results, and we report 10 electron states for the first time, that is, 8²∑_{g, u}⁺-9²∑_{g, u}⁺, 5²Π_{g, u}-7²Π_{g, u} and 3²△_{g, u}. The vibrational-rotational spectroscopic constants and lowest vibrational-rotational energy levels (ν=0-20) of the bound states are also presented. Moreover, in order to illustrate the strong state interactions of adjacent states with same symmetry, the information about the avoided crossing points is shown in detail. Finally, the transition dipole moments from a few low-lying excited states (1²Π_u-3²Π_u) to the ground state X²∑_g⁺ are computed. Therefore, it is expected that our computational results in the present calculations are significant for the molecular spectroscopy, ion-atom interaction and molecular cold collision fields.