MRCI+Q study on the electronic structure and spectroscopy of the low-lying electronic states of HgBr including spin-orbit coupling

•The potential energies of 14 Λ-S states of HgBr are calculated by MRCI method.•The spin-orbit coupling and 5d10 correlation effects are included in the calculation.•Spectroscopic constants of bound states of HgBr are determined.•The predissociation mechanism of C2Π1/2 of HgBr are analyzed.•Radiative lifetimes of C2Π1/2, D2Π3/2 and B2Σ+1/2 states of HgBr are evaluated. Due to attractive candidate for the laser application and searching for the permanent electric dipole moment of the electron (eEDM), mercury bromide (HgBr) is of much interest to researchers. However, detailed information of the electronic structure of HgBr is still lacking, especially for spin-orbit interactions in excited states. In this work, high-level configuration interaction calculations of low-lying states correlating to the lowest two dissociation limits Hg(1S) + Br(2P) and Hg(3P) + Br(2P) of HgBr are carried out. In order to ensure good accuracy, the Davidson correction and spin-orbit coupling (SOC) effect are all taken into consideration in our computations. The potential energy curves (PECs) of 14 Λ-S states and 30 Ω states are determined. Based on the PECs, the spectroscopic constants of the bound states are obtained, most of which have not been reported in previous studies. The calculated SOC integrals of 22Σ+-22Π indicate a strong spin-orbit interaction, which can explain the apparent perturbations between B2Σ+1/2 and C2Π1/2 found in the HgBr fluorescence excitation spectrum. Finally, to reveal more detail on transition properties of excited states, transition dipole moments of C2Π1/2-X2Σ+1/2, D2Π3/2-X2Σ+1/2, and B2Σ+1/2-X2Σ+1/2 transitions and radiative lifetimes of C2Π1/2, D2Π3/2, and B2Σ+1/2 are determined. [Display omitted]