Extensive ab initio study of the electronic states of BSe radical including spin-orbit coupling

The internally contracted multi-reference configuration interaction method (MRCI) with Davidson modification and the Douglas-Kroll scalar relativistic correction has been used to calculate the BSe molecule at the level of aug-cc-pV5Z basis set. The calculated electronic states, including 9 doublet and 6 quartet Λ-S states, are correlated to the dissociation limit of B((2)P(u))+Se((3)P(g)) and B((2)P(u))+Se((1)D(g)). The Spin-orbit coupling (SOC) interaction is taken into account via the state interaction approach with the full Breit-Pauli Hamiltonian operator, which causes the entire 15 Λ-S states to split into 32Ω states. This is the first time that the spin-orbit coupling calculation has been carried out on BSe. The potential energy curves of the Λ-S and Ω electronic states are depicted with the aid of the avoided crossing rule between electronic states of the same symmetry. The spectroscopic constants of the bound Λ-S and Ω states were determined, which are in good agreement with the experimental data. The transition dipole moments (TDMs) and the Franck-Condon factors (FCs) of the transitions from the low-lying bound Ω states A(2)Π(I)3/2, B(2)Π(I)1/2 and C(2)Δ(I)3/2 to the ground state X(2)Σ(+)1/2 have also been presented. Based on the previous calculations, the radiative lifetimes of the A(2)Π(I)3/2, B(2)Π(I)1/2 and C(2)Δ(I)3/2 were evaluated.