Fedorov Dmitry A, Derevianko Andrei, Varganov Sergey A
Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557-0216, USA.
Department of Physics, University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557-0220, USA.
J Chem Phys. 2014 May 14;140(18):184315. doi: 10.1063/1.4875038.
We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X(1)Σ(+) electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-ζ basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-ζ quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm(-1) for LiNa and by no more than 114 cm(-1) for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm(-1), and the discrepancies for the anharmonic correction are less than 0.1 cm(-1). We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrödinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.
我们使用包含单双激发和三激发的耦合簇方法，计算了异核碱金属二聚体XY（X、Y = Li、Na、K、Rb、Cs）在X(1)Σ(+)电子态下的势能曲线、永久偶极矩曲线以及基态和激发振动态的寿命。对于Li和Na，使用带有额外核心函数的全电子四重ζ基组；对于K、Rb和Cs，使用具有四重ζ质量基组的小核心相对论有效核心势。结果表明，包含耦合簇非微扰三激发对于获得准确的势能曲线至关重要。准确预测永久偶极矩需要一个带有额外核心函数的大的单电子基组。LiNa的离解能仅被高估14 cm(-1)，其他分子的离解能被高估不超过114 cm(-1)。实验和计算得到的简谐振动频率之间的差异小于1.7 cm(-1)，非谐校正的差异小于0.1 cm(-1)。我们表明，异核碱金属二聚体的原子电负性差异与永久偶极矩之间的相关性并不完美。为了获得振动能量和波函数，使用B样条基组方法求解振动薛定谔方程。计算了所有振动态之间的跃迁偶极矩、爱因斯坦系数以及振动态的寿命。我们根据自发发射、黑体辐射诱导的受激发射和吸收来分析振动态的衰减率。在所有研究的异核碱金属二聚体中，基态振动态的寿命比任何激发态都长得多。
