Theoretical study of the electronic structure of mono-bromide of lanthanum molecule including spin-orbit coupling...

Among the family of lanthanide halides compounds, this work is devoted to the third halogen bromine. The presented lanthanum bromide LaBr molecule has a remarkable scientific interest regarding the other molecules because it presents few experimental studies and only one theoretical study. The theoretical electronic structure of the LaBr molecule is achieved by using the post-Hartree-Fock methods manifested by the complete active space self consistent field (CAS-SCF) method and the multi reference configuration interaction with single and double excitation (MRCI-SD) method. All of these calculations are performed via the quantum chemistry software MOLPRO. We predicted for the first time in the literature, 24 lowest-lying electronic states in the representation ^2S+ 1Λ^(±) and their corresponding components in the representation Ω^(±) when taking into account the spin-orbit coupling (SOC), situated below 22,000 cm^- 1. We calculated the spectroscopic constants for both cases (without/with SOC effects) related to the 13 singlet and 11 triplet states and for their components. We drew also in this paper the potential energy curves (PEC_s in a range of internuclear distance R varying from 2.00 to 4.22 Å. Graphical AbstractPotential energy curves for 13 singlet electronic states of LaBr.