Theory ofF-CentergValues in Divalent Compounds

Abstract

Positive $g$ shifts in the ESR spectra of $F$ centers in some alkaline-earth compounds have been reported by Wertz, Orton, and Auzins, contrary to the theory of Adrian. A model for the $F$ center in divalent compounds is proposed which involves an admixture of a charge-transfer configuration consisting of a hole trapped on an anion adjacent to an $F^{\prime }$ center. It is shown that the charge-transfer configuration makes a positive contribution to the $g$ shift. Values of a configuration-mixing parameter $C^2$ inferred from the ESR data are compared with values calculated from a simplified model. Qualitative agreement tends to support the proposed explanation for positive $g$ shifts, but detailed quantitative agreement would require a more elaborate calculation.