MRCI study of spectroscopic and molecular properties of X-2 Pi(g), a(4)Pi(u), A(2)Pi(u), b(4)Sigma(-)(g), D-2 Delta(g) and B-2 Sigma(-)(g) electronic states of O-2(+) ion

作者：Zhang, Xiaoniu; Shi, Deheng^*; Sun, Jinfeng; Zhu, Zunlue

来源：Molecular Physics, 2011, 109(12): 1627-1638.

DOI：10.1080/00268976.2011.578593

• core-valence correlation correction
• relativistic correction
• spectroscopic parameter
• molecular constant
• extrapolation

The potential energy curves (PECs) of six low-lying electronic states (X-2 Pi(g), a(4)Pi(u), A(2)Pi(u), b(4)Sigma(-)(g), D-2 Delta(g) and B-2 Sigma(-)(g)) of O-2(+) ion were studied by the ab initio quantum chemical method. The calculations were carried out with the full valence complete active space self-consistent field (CASSCF) method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with large correlation-consistent basis sets. Effects on the PECs of the core-valence correlation and relativistic corrections are taken into account. The way to consider the relativistic correction is to use the second-order Douglas-Kroll Hamiltonian (DKH2) approximation. The core-valence correlation correction is carried out with the cc-pCVQZ basis set, and the relativistic correction is performed at the level of cc-pVQZ basis set. To obtain more reliable results, the PECs determined by the MRCI calculations are also corrected for size-extensivity errors by means of the Davidson modification (MRCI+Q). These PECs are extrapolated to the complete basis set (CBS) limit by the two-point total-energy extrapolation scheme. With these PECs, the spectroscopic parameters (T-e, D-e, D-0, R-e, omega(e), omega(e)x(e), alpha(e) and B-e) are determined and compared with those reported in the literature. The conclusion can be reached that the effect on the spectroscopic parameters of the core-valence correlation correction is larger than that of the relativistic correction. With the PECs obtained by the MRCI+Q/CV+DK56 calculations, the vibrational levels and inertial rotation constants of the first 26 vibrational states are determined for these electronic states of non-rotating O-2(+) ion. Comparison with the experimental data shows that the present spectroscopic parameters and molecular constants are accurate.

• 出版日期2011
• 单位河南师范大学