A perturbative calculation of the rovibrational energy levels of methane.
A perturbative calculation of the rovibrational energy levels of methane.
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DOI：
10.1016/s1386-1425(01)00674-6
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发表时间：
2002-03
期刊：
影响因子：
--
通讯作者：
Xiao-Gang Wang;E. Sibert
中科院分区：
文献类型：
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作者：
Xiao-Gang Wang;E. Sibert
甲烷的旋转振动能级由一个四次从头算势能力场确定，其中伸展的扩展坐标为莫尔斯坐标，弯曲的扩展坐标为莫尔斯坐标。能量是用正则范弗莱克微扰理论计算的。得到了用曲线法坐标和直线法坐标表示的旋转振动哈密顿量的结果。将二阶、四阶和六阶曲线结果与实验结果进行比较，并将直线哈密顿量和曲线哈密顿量的四阶结果进行比较。在低J能级下，计算得到的振动能级与实验值吻合较好。计算得到的旋转能级劈裂与实验结果更加吻合。特别地，基态四面体分裂小至10−4cm−1，我们的计算在六阶上可以很好地再现。
The rovibrational energy levels of methane are determined from a quartic ab initio potential energy force field where the expansion coordinates are the Morse coordinates for the stretches and extension coordinates for the bends. Energies are calculated using canonical Van Vleck perturbation theory. Results are obtained for both rotation–vibration Hamiltonians expressed as functions of curvilinear and rectilinear normal coordinates. Second, fourth, and sixth order curvilinear results are compared with experimental results, and fourth order results for the rectilinear and curvilinear Hamiltonian are compared to each other. The calculated rovibrational levels are in good agreement with the experimental values for low J levels. The calculated rotational level splittings are in even better agreement with the experiment. In particular, the ground state tetrahedral splittings, which are as small as 10−4cm−1, are well reproduced by our calculations at sixth order.