This transition is also observed in the homoleptic structure (394.0 nm)
where, due to the symmetry of the molecule, a lower change in the dipole
moments is produced with respect to the carbonate-hydroxide complex. The
substitution of one carbonate ligand by two hydroxyl ligands affects
directly the transition dipole moment, resulting in an increase of the
transition probability from 0.231 to 0.263 a.u. for the carbonate and
carbonate-hydroxide complexes, respectively. This could explain the
shoulder observed in the spectrum of the heteroleptic complex (Fig.2).
Multiconfigurational
calculations
The Bk(IV) free ion, considering a scalar relativistic limit and Hund’s
rule, has an 8S ground state (L=0, S = 7/2) followed
by a first excited multiplet 6P ~
26500 cm-1 higher in energy. The spin-orbit coupling
(SOC) removes the state degeneracy resulting in a series of multiplets
characterized by the total angular momentum quantum number (J), with the
ground term being (in a Russell-Saunders
notation) 8S7/2. If the ion is now
placed in a ligand environment, the effect of the ligand field produces
the split of the 2J+1 degenerate state and the mixing of states with
different mJ values. This picture, based on a single
ion structure, can be used in molecular systems where mixing between
metal and ligand is negligible.