Radiation defects in nacl matrix with reduced lattice symmetry caused by light cation doping and elastic uniaxial deformation
Radiaciniai defektai nacl matricoje su dėl nedidelių katijoninių priemaišų ir elastinės vienaašės deformacijos sumažinta gardelės simetrija
Shunkeyev K. Ubaev Z. Lushchik A. Myasnikova L.
11 October 2021Lithuanian Physical Society
Lithuanian Journal of Physics
2021#61Issue 3151 - 160 pp.
The processes of radiation defect creation and radiative relaxation of electronic excitations under applied local or/and uniaxial elastic deformation have been studied in NaCl crystals by means of optical absorption, luminescence and thermoactivation spectroscopy methods. In NaCl:Li at 80 K, X-ray-induced absorption bands peaked around 3.35 and 4.6 eV have been detected and ascribed to interstitial halide atoms located nearby Li impurity cations, HA (Li) centres. Subsequent thermal annealing of HA (Li) centres leads to the formation of polyhalide centres responsible for the absorption band at 5.35 eV. In an X-irradiated and stressed NaCl:Li crystal (degree of uniaxial elastic deformation of ε = 0.9%), the peak of thermally stimulated luminescence at ~115 K is composed of the ~2.7-eV emission appearing, in our opinion, due to the recombination of the electron, thermally released from an F′ centre, with a hole-type HA (Li) centre. The applied uniaxial elastic stress facilitates the self-trapping of anion excitons in regular regions of a NaCl lattice and impedes the energy transfer by mobile excitons to impurities/defects and, in turn, attenuates the Br-related luminescence peaked at 3.95 eV with respect to the π-emission of self-trapped excitons (~3.35 eV). The 3.95 eV emission has been detected in a natural NaCl crystal containing homologous Br impurity ions.
Alkali halide crystal , Electronic excitation , Self-trapped exciton , Uniaxial elastic deformation
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Institute of Physics
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