Transition properties between low-lying electronic states of SiO⁺

In this work, we investigate the potential energy curves (PECs), transition dipole moments (TDMs) and spin-orbit couplings for low-lying electronic states of SiO⁺ based on ab initio calculations. The PECs of seventeen low-lying electronic states are calculated by the internally contracted multireference configuration interaction (icMRCI) method with the Davidson correction, as well as the basis set extrapolation, core-valence (CV) correction and scalar relativistic correction. The Schrödinger equation of nuclear movement is solved over the PEC to obtain the rotational and vibrational energy levels, which are used to fit the spectroscopic parameters. The Einstein coefficients, Franck-Condon factors and oscillator strengths for dipole-allowed transitions are calculated with the PECs and TDMs. The radiative lifetimes of some excited states are also obtained. Our calculated radiative lifetime of 67.8 ns for B²Σ⁺(υ′ = 0) is in excellent agreement with the recent experimental measurement of 66 ± 2 ns. The spin-orbit coupling integrals related to the X²Σ⁺, A²Π, B²Σ⁺, 1⁴Σ⁺, 1⁴Π and 1⁴Σ⁻ states are calculated using the Breit-Pauli Hamiltonian. In addition, the effects of spin-orbit couplings on the potential energies of the Λ-S electronic states are discussed.