Optical detection of metastableH2−defects and photoconversion of anion vacancies in thermochemically reduced CaO crystals

The localized vibrational modes and electronic transitions of ${\mathrm{H}}^{2\mathrm{-}}$ defects in thermochemically reduced CaO crystals have been detected. The cause of the long-lived luminescence of the F center at room temperature is shown to be due directly to release of electrons from metastable ${\mathrm{H}}^{2\mathrm{-}}$ defects. Photoconversion between F and $F^{+}$ centers involves electron transfer via the reversible process ${\mathrm{H}}^{\mathrm{-}}$+${\mathrm{e}}^{\mathrm{-}}$⇆${\mathrm{H}}^{2\mathrm{-}}$. .AE