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

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