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

作者：Shi, Deheng^*; Li, Peiling; Sun, Jinfeng; Zhu, Zunlue

来源：Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy , 2014, 117: 109-119.

DOI：10.1016/j.saa.2013.07.093

• Spin-orbit coupling
• Potential energy curve
• Spectroscopic parameter
• Relativistic correction
• Core-valence correlation correction

The potential energy curves (PECs) of 28 Omega states generated from 9 Lambda-S states (x(2)Pi, 1(4)Pi, 1(6)Pi. 1(2)Sigma(+), 1(4)Sigma(+), 1(6)Sigma(+), 1(4)Sigma(-), 2(4)Pi and 1(4)Delta) are studied for the first time using an ab initio quantum chemical method. All the 9 Lambda-S states correlate to the first two dissociation limits, N(S-4(u)) + Se(P-3(g)) and N(S-4(u)) + Se(D-3(g)), of NSe radical. Of these Lambda-S states, the 1(6)Sigma(+), 1(4)Sigma(+), 1(6)Pi, 2(4)Pi and 1(4)Delta are found to be rather weakly bound states. The 1(2)Sigma(+) is found to be unstable and has double wells. And the 1(6)Sigma(+), 1(4)Sigma(+), 1(4)Pi and 1(6)Pi 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 A-S states with one shallow well on each PEC. The spectroscopic parameters of 9 Lambda-S and 28 Omega states are determined by fitting the first ten vibrational levels whenever available, which are calculated by solving the rovibrational Schrodinger equation with Humerov's method. The splitting energy in the X-2 Pi Lambda-S state is determined to be about 864.92 cm(-1), which agrees favorably with the measurements of 891.80 cm(-1). Moreover, other spectroscopic parameters of Lambda-S and Omega 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.

• 出版日期2014-1-3
• 单位河南师范大学