Magneto-optical Study of a Charge-Transfer Band in Vanadium-Doped MgO

A study of the magnetic circular dichroism and optical absorption associated with a band at 5.15 eV in vanadium-doped MgO is presented. The band is assigned to an electron transition from an orbital predominantly on the oxygen ligands of the ${\mathrm{V}}^{3+}$ ion to an orbital predominantly on the ${\mathrm{V}}^{3+}$ ion. Theory for the magnetic circular dichroism originating from the orbitally degenerate ground state is proposed, and the result of an analysis is found to be consistent with the presence of a dynamical Jahn-Teller effect in the ground state. A classification of the excited-state symmetry is made which implies a reversal from the conventional ordering of the $\pi t_{1u}$ and $\pi t_{2u}$ ligand-orbital energy levels.