Charge and mass transfer involving hydrogen in MgO crystals thermochemically reduced at high temperatures

Optical-absorption measurements show that ${\mathrm{H}}^{-}$ ions are thermally much more stable than anion vacancies when thermochemically reduced MgO samples are annealed in a reducing atmosphere. At 1900 K all anion vacancies are annihilated, but the concentration of ${\mathrm{H}}^{-}$ ions remains unchanged. Results of electron irradiations on a crystal annealed at 1900 K demonstrate unambiguously that the infrared-absorption peaks previously attributed to ${\mathrm{H}}^{-}$ ions are indeed due to protons in anion sublattice sites. ${\mathrm{H}}^{-}$ concentrations can be obtained from the infrared absorbance of the ${\mathrm{H}}^{-}$ ions. The lifetime of the 2.3-eV $F$-center phosphorescence is shown to be affected by the relative concentrations of ${\mathrm{H}}^{-}$ ions to anion vacancy. Decreasing the anion-vacancy concentration by thermal annealing, thereby increasing the relative concentration of ${\mathrm{H}}^{-}$ ions to anion vacancies, leads to an enhancement of the lifetime of the phosphorescence.