LAUSR

Abstract This work explored the spectroscopic parameters and vibrational properties of 12 states of BrO radical. The 12 states were X 2 Π, A 2 Π, 1 2 Δ, 1 2 Σ + , 1 2 Σ − , 2 2 Σ − , a 4 Σ − , 2 4 Σ − , 1 4 Σ + , 1 4 Δ, 1 4 Π, and 2 4 Π, which were generated from the first dissociation limit, Br( 2 P u ) + O( 3  P g ). The potential energy curves were calculated with the CASSCF method, which was followed by the icMRCI approach with Davidson correction. Of the 12 electronic states, the 2 4 Π state was repulsive. Each state had the single well and only the A 2 Π state had one barrier. The 1 2 Δ, 1 2 Σ + , 1 2 Σ − , 2 2 Σ − , 2 4 Σ − , 1 4 Σ + , 1 4 Δ and 1 4 Π states had only several vibrational levels and were very weakly-bound states, which well depths were less than 110 cm −1 . To improve the quality of potential energy curves, core-valence correlation and scalar relativistic corrections as well as the extrapolation to the complete basis set limit were included. The spectroscopic parameters and vibrational properties were determined. The transition dipole moments between two electronic states and Franck-Condon factors of some transitions were evaluated. The spin-orbit coupling effect on the spectroscopic parameters of the X 2 Π and A 2 Π states was discussed. The spectroscopic parameters and vibrational properties reported in this paper can be expected to be reliably predicted ones.