Correlation of EPR and thermoluminescence in crystals of highly colored CaO:Mg: Involvement of a center containing hydrogen ions

Electron-spin-resonance measurements at \ensuremath{\sim}9 and 4 GHz have identified a center with tetragonal symmetry and S=(1/2), I=(1/2) [${g}_{?}$=1.9998(1), ${g}_{\ensuremath{\perp}}$=2.0029(1), ${A}_{?}$=0.002 03(1) ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, ${A}_{\ensuremath{\perp}}$ =0.001 34(1) ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$] in crystals of highly colored CaO:Mg. The resonances are produced by illumination at \ensuremath{\lambda}<750 nm and T<200 K and are associated with the thermoluminescence peak (${\ensuremath{\lambda}}_{\mathrm{max}=690}$ nm) at 180 K. The center involves three lattice sites along 〈100〉 with ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ at an anion-vacancy site next to the cation-vacancy site of a ${\mathrm{P}}^{\mathrm{\ensuremath{-}}}$ center. The center appears to arise as a result of crystal-growth conditions and is not specifically associated with the Mg dopant.