Accurate ab initio study on the A2Π, 1(4)Σ+, 1(4)Π, 2(4)Π and 1(6)Σ+ electronic states of AlO radical including...

The potential energy curves (PECs) of 15 Ω states generated from five Λ-S states (A2Π, 1(4)Σ+, 1(4)Π, 2(4)Π and 1(6)Σ+) of AlO radical are studied in detail using high level ab initio quantum chemical method for the first time. All 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 (MRCI+Q). The spin-orbit coupling effect is included by the Breit-Pauli Hamiltonian with the aug-cc-pCVTZ basis set. Convergent behavior is discussed and excellent convergence has been observed with respect to the basis sets and level of theory. To improve the quality of PECs, core-valence correlation and scalar relativistic corrections are taken into account. Core-valence correlation corrections are included employing a cc-pCVQZ 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 by the total-energy extrapolation scheme. With these PECs including all the corrections used here, on the one hand, the spectroscopic parameters of all the Λ-S and Ω states are calculated, which are in reasonable agreement with the experimental and other theoretical results; on the other hand, the vibrational levels and inertial rotation constants of X2Σ+, A2Π, B2Σ+ Λ-S states as well as A2Π3/2 and A2Π1/2 Ω states are determined, which also agree well with the measurements. The vibrational levels and inertial rotation constants of A(2)Π3/2 and A2Π1/2 Ω states as well as the spectroscopic parameters of four Λ-S states (1(4)Σ+, 1(4)Π, 2(4)Π and 1(6)Σ+) and their corresponding 13 Ω states can be expected to be reliable predicted ones.