Accurate theoretical spectroscopic investigations of the 20 Λ-S and 58 Ω states of O₂⁺ cation including the spin–orbit coupling effect

Abstract

The potential energy curves (PECs) are calculated for the 20 Λ-S states (X²Π_g, A²Π_u, B²Σ⁻_g, a⁴Π_u, b⁴Σ⁻_g, b′⁴Π_g, c⁴Σ⁻_u, 1²Σ⁺_g, 1²Σ⁺_u, 1²Σ⁻_u, 1⁴Σ⁺_g, 1⁴Σ⁺_u, 1⁴Δ_g, 1⁴Δ_u, 1⁶Σ⁺_g, 1⁶Σ⁺_u, 1⁶Π_g, 1⁶Π_u, 2⁴Π_g and 2⁴Π_u) of O₂⁺ cation and their corresponding 58 Ω states. Of these 20 Λ-S states, the 1⁶Π_u state is found to be repulsive. The 1²Σ⁺_g, 1⁴Σ⁺_u, c⁴Σ⁻_u and 1⁴Δ_u states are found to possess the double well. The b⁴Σ⁻_g, 1⁶Σ⁺_g, 1⁴Σ⁺_u, a⁴Π_u, A²Π_u, 1⁶Π_g and 2⁴Π_g states are found to be inverted with the spin–orbit coupling effect included. The b′⁴Π_g, 1⁶Π_g, 1⁶Σ⁺_g, 1⁴Σ⁺_u and 1⁴Δ_u states, and the second well of the 1²Σ⁺_g state are found to be the weakly bound states. The b′⁴Π_g state is found to possess one well with one barrier. The PECs are calculated by the complete active space self-consistent field method, which is followed by the internally contracted multireference configuration interaction approach with the Davidson correction in combination with the aug-cc-pV6Z basis set. The core–valence correlation and scalar relativistic corrections are included. The convergent behaviour of present calculations is discussed with respect to the basis set and theoretical level. The spin–orbit coupling effect is accounted for. The PECs are extrapolated to the complete basis set limit. The spectroscopic parameters are evaluated, and compared with available measurements. It demonstrates that the spectroscopic parameters reported here can be expected to be reliably predicted ones.

Keywords:

• potential energy curve
• spectroscopic parameter
• vibrational property
• spin–orbit coupling effect
• core–valence correlation correction

Additional information

Funding

This work was sponsored by the National Natural Science Foundation of China [grant number 11274097]; Natural Science Foundation of Education Bureau of Henan Province in China [grant number 2010B140013] ; the Program for Science & Technology of Henan Province in China [grant number 142300410201].