Magnetic Circular Dichroism of the CaOFBand

The magnetic circular dichroism of the 3.1-eV absorption band associated with the two-electron diamagnetic $F$ center in CaO has been measured. Interpretation of the result in terms of a ${}_{}{}^1{}_{}{}^{}A_{1g}^{}{}_{}{}^{}-{}_{}{}^1{}_{}{}^{}T_{1u}^{}{}_{}{}^{}$ optical transition gives an orbital $g$ value of -0.34± 0.1 for the ${}_{}{}^1{}_{}{}^{}T_{1u}^{}{}_{}{}^{}$ excited state. This unexpected negative $g$ value may be explained in terms of a diffuse excited state, where the electron has opposing angular momentum within and outside of the vacancy.