Accurate calculations on 9 螞-S and 28 惟 states of NSe radical in the gas phase: Potential energy curves, spectroscopic parameters and spin-orbit couplings

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• 作者：Deheng Shi ; Peiling Li ; Jinfeng Sun ; Zunlue Zhu
• 关键词：Spin-orbit coupling ; Potential energy curve ; Spectroscopic parameter ; Relativistic correction ; Core-valence correlation correction
• 刊名：Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
• 出版年：3 January, 2014
• 年：2014
• 卷：117
• 期：Complete
• 页码：109-119
• 全文大小：1109 K

文摘

The potential energy curves (PECs) of 28 惟 states generated from 9 螞-S states (X²螤, 1⁴螤, 1⁶螤, 1²危⁺, 1⁴危⁺, 1⁶危⁺, 1⁴危^-, 2⁴螤 and 1⁴螖) are studied for the first time using an ab initio quantum chemical method. All the 9 螞-S states correlate to the first two dissociation limits, N(⁴S_u) + Se(³P_g) and N(⁴S_u) + Se(³D_g), of NSe radical. Of these 螞-S states, the 1⁶危⁺, 1⁴危⁺, 1⁶螤, 2⁴螤 and 1⁴螖 are found to be rather weakly bound states. The 1²危⁺ is found to be unstable and has double wells. And the 1⁶危⁺, 1⁴危⁺, 1⁴螤 and 1⁶螤 are found to be the inverted ones with the SO coupling included. The PEC calculations are made by the complete active space self-consistent field method, which is followed by the internally contracted multireference configuration interaction approach with the Davidson modification. The spin-orbit coupling is accounted for by the state interaction approach with the Breit-Pauli Hamiltonian. The convergence of the present calculations is discussed with respect to the basis set and the level of theory. Core-valence correlation corrections are included with a cc-pCVTZ basis set. Scalar relativistic corrections are calculated by the third-order Douglas-Kroll Hamiltonian approximation at the level of a cc-pV5Z basis set. All the PECs are extrapolated to the complete basis set limit. The variation with internuclear separation of spin-orbit coupling constants is discussed in brief for some 螞-S states with one shallow well on each PEC. The spectroscopic parameters of 9 螞-S and 28 惟 states are determined by fitting the first ten vibrational levels whenever available, which are calculated by solving the rovibrational Schr枚dinger equation with Numerov鈥檚 method. The splitting energy in the X²螤 螞-S state is determined to be about 864.92 cm^鈭?, which agrees favorably with the measurements of 891.80 cm^鈭?. Moreover, other spectroscopic parameters of 螞-S and 惟 states involved here are also in fair agreement with available measurements. It demonstrates that the spectroscopic parameters reported here can be expected to be reliable predicted ones.