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

• The PECs of the 15 Λ–S states have been calculated for the first time.
• The PECs of the 32 Ω states arising from 15 Λ-S states have been calculated.
• The energy degeneracy among B2Σ + (II), C2Δ(I) and 2Σ−(I) states has been analyzed.
• The double wells of C2Δ(I) ,2Σ−(I), 2Π(II) and 2Π(III) states have been studied.

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(2Pu) + Se(3Pg) and B(2Pu) + Se(1Dg). 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 32 Ω 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 A2Π(I)3/2, B2Π(I)1/2 and C2Δ(I)3/2 to the ground state X2Σ+1/2 have also been presented. Based on the previous calculations, the radiative lifetimes of the A2Π(I)3/2, B2Π(I)1/2 and C2Δ(I)3/2 were evaluated.

The amplified view of the energy degeneracy of B2Σ+(II), C2Δ(I), 2Σ−(I), 2Δ(II) and 2Σ−(II) states.Figure optionsDownload as PowerPoint slide