Stable[Li]0Defects in MgO Single Crystals

The ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ center has been formed in lithium-doped single crystals of MgO by high temperature quenching. In contrast to the ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ center formed by low-temperature $\gamma$ irradiation, the center formed by quenching is stable at room temperature. A heavy electron irradiation also produces stable ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ centers. Investigations using EPR and electron-nuclear double resonance techniques have established that, in all three cases, the ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ center has the same local configuration. The increased stability has enabled us to observe the motionally averaged ${\mathrm{}\left[\mathrm{Li}\right]\mathrm{}}^0$ spectrum for the first time. Optical absorption data indicate that the center is associated with an absorption band at 1.83 eV.