Theoretical description of the low-lying electronic states of LuBr located below 41,700 cm−1

•Quantum Chemistry calculations on the electronic structure of LuBr are presented.•The spin-orbit coupling has been included.•Potential energy curves and spectroscopic constants are presented for 21 2S+1Λ(+/-) molecular states (without the spin-orbit coupling) and for 42 Ω(±) states (with the spin-orbit coupling).

A theoretical investigation of the lowest molecular states of LuBr located below 41,700 cm−1 in the 2S+1Λ(+/−) and Ω(±) representations when including the spin-orbit effects, has been performed through SA-CASSCF and MRCI calculations. Potential energy curves have been determined for 21 2S+1Λ(+/−) and 42 Ω(±) molecular states in the range of 1.70 to 3.50 Å and the spectroscopic constants (Re, Te, ωe and ωeχe) have been deduced. Transition Dipole Moments have been computed for various allowed ΔΛ=0,±1 on the same range of internuclear distances. In the case of the ground state and the two expected lowest singlet excited states (1)1Π and (2)1Σ+, a good agreement with the experimental results is obtained while new results are reported for the not yet observed 18 2S+1Λ(+/−) and 42 Ω(±) states. A comparison with previous studies on the Lutetium mono-halides LuF, LuCl and LuI is presented, leading to trends in transition energies, equilibrium distances and dipole moments.