Lithuanian Journal of Physics article / Lietuvos fizikos žurnalo straipsnis

RADIATION DEFECTS IN NaCl MATRIX WITH REDUCED LATTICE SYMMETRY CAUSED BY LIGHT CATION DOPING AND ELASTIC UNIAXIAL DEFORMATION
Kuanyshbek Shunkeyev^a, Zhiger Ubaev^a, Aleksandr Lushchik^a,b, and Lyudmila Myasnikova^a
^aK. Zhubanov Aktobe Regional University, 34 Moldagulova Avenue, 030000 Aktobe, Kazakhstan
^bInstitute of Physics, University of Tartu, 1 W. Ostwald Street, 50411 Tartu, Estonia
Email: shunkeev@rambler.ru

Received 18 December 2020; revised 24 March 2021; accepted 24 March 2021

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, H_A(Li) centres. Subsequent thermal annealing of H_A(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 H_A(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.

Keywords: alkali halide crystal, self-trapped exciton, electronic excitation, uniaxial elastic deformation
PACS: 61.10.Ht, 61.80.Az, 78.55.Fv, 78.70.En, 78.60.-b

RADIACINIAI DEFEKTAI NaCl MATRICOJE SU DĖL NEDIDELIŲ KATIJONINIŲ PRIEMAIŠŲ IR ELASTINĖS VIENAAŠĖS DEFORMACIJOS SUMAŽINTA GARDELĖS SIMETRIJA
Kuanyshbek Shunkeyev^a, Zhiger Ubaev^a, Aleksandr Lushchik^a,b, Lyudmila Myasnikova^a

^aAktobės regioninis K. Zubanovo universitetas, Aktobė, Kazachstanas
^bTartu universiteto Fizikos institutas, Tartu, Estija

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