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

The oscillator strengths of the f-f hypersensitive transitions of lanthanide tribromides (LnBr3; Ln = Pr through Tm except for Gd) were calculated by the multi-reference spin–orbit configuration interaction method. To examine previously proposed mechanisms, the Judd–Ofelt intensity parameters τ2 based on the dynamic-coupling model were evaluated and compared with those by the CI calculations. The calculated intensity parameters had a similar magnitude, implying that the dynamic-coupling model has a dominant contribution to the intensities. The difference between the two parameters is discussed in terms of the effects of polarization shielding and ligand-to-metal charge transfer.