An ab initio study on the f-f hypersensitive transition intensities of lanthanide tribromide molecules

► Oscillator strengths and Judd-Ofelt intensity parameters of LnBr3 are calculated with multi-reference spin-orbit CI method. ► Intensities of f-f hypersensitive transitions are dominated by the dynamic-coupling model. ► The intensities calculated with the dynamic-coupling model are overestimated due to the neglect of the polarization shielding effect. ► Ligand to metal charge transfer to an empty 4f orbital cannot be neglected especially in EuBr3.