Correlation between Fe, Cr, and the broad red emission band inγ-ray-irradiated MgO

Absorption and luminescence spectra for MgO have been obtained during $\gamma$-ray irradiation and subsequent thermal annealing. The growth and annealing of the ${\mathrm{Fe}}^{3+}$ band is attributed to the existence of various electron-trapping centers. A clear correlation is observed between Fe and Cr, with ${\mathrm{Cr}}^{3+}$ acting as an electron trap during irradiation. In addition, the results indicate that the broadband emission at 700 nm is most likely due to ${\mathrm{Fe}}^{2+}$, arising from reactions of the type ${\mathrm{Fe}}^{3+}+e^{-}$ and $V+{\mathrm{Fe}}^{1+}$.