Journal of Physical Studies 16(1/2), Article 1602 [8 pages] (2012) DOI: https://doi.org/10.30970/jps.16.1602 FD-CENTERS IN FLUORITE CRYSTALS DOPED WITH ALKALI METALS Z. P. Chornij1, I. B. Pirko2, V. M. Salapak1, M. R. Panasyuk3 {1}Department of Physics, National Forestry University of Ukraine, 103 Gen. Chuprynky St., Lviv, UA--79057, Ukraine {2}Department of Computer Engineering and Modeling Processes, National Forestry University of Ukraine, 103, Gen. Chuprynky St., Lviv, UA--79057, Ukraine {3}Scientific-Technical and Education Centre of Low Temperature Studies, Ivan Franko National University of Lviv, 50, Drahomanov St., Lviv, UA--79005, Ukraine

In fluorite crystals doped with alkali metals a new electronic $F_{D}$-center colouring has been discovered. This center is an $F$-center located in the vicinity of the impurity vacancy dipole. The $F_{D}$-center occurs in the repeated exposure of optically discoloured crystals in $M_{A}^{+}$-lines of absorption and is formed due to the localization of zone electrons in the band of two vacancy complexes: $e^{-}+V^{\bullet}_{a}Me^{\prime}V^{\bullet}_{a}\rightarrow V^{0}_{a}Me^{\prime}V^{\bullet}_{a}$ where $e^{-}$ is a band electron; $V^{\bullet}_{a}$ is an anion vacancy; $Me^{\prime}$ is an alkali metal ion; $V^{0}_{a}$ is an $F$-center; $V^{0}_{a}Me^{\prime}V^{\bullet}_{a}$ is an $F_{D}$-center. $F_{D}$-centers are thermally stable at the temperatures of $T T_{r}$ $F_{D}$-centers are transformed into $M_{A}^{+}$-centers: $V^{0}_{a}Me^{\prime}V^{\bullet}_{a} _{\overrightarrow{T≈ T_{r}}}^{KT}$ $Me^{\prime}V^{\bullet}_{a}V^{0}_{a}=M_{A}^{+}$.

PACS number(s): 61.80.-x, 61.72.jd, 78.40.-q

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