Theoretical analysis of the kinetics of low-temperature defect recombination in alkali halide crystals

We analyzed carefully the experimental kinetics of the low-temperature diffusion-controlled F, H center recombination in a series of irradiated alkali halides and extracted the migration energies and pre-exponential parameters for the hole H centers. The migration energy for the complementary electronic F centers in NaCl was obtained from the colloid formation kinetics observed above room temperature. The obtained parameters were compared with data available from the literature

Accumulation of radiation defects and modification of micromechanical properties under MgO crystal irradiation with swift 132Xe ions

This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. A.A. also acknowledges support via the project GF AP05134257 of Ministry of Education and Science of the Republic of Kazakhstan .Accumulation of F-type defects under irradiation of MgO crystals by 0.23-GeV 132Xe ions with fluence varying by three orders of magnitude has been investigated via the spectra of optical absorption and low-temperature cathodoluminescence. The number of single centers continuously increases with fluence without any marks of saturation. At the highest fluence, a mean volume concentration of 3.1 × 1019 and 3.35 × 1019 cm−3 is reached for F and F+ centers, respectively. The F+ emission strongly dominates in the cathodoluminescence of irradiated MgO and its enhancement with fluence is detected. However, the creation efficiency of the F2 aggregate centers is very low and fluence dependence has a complicated shape. Radiation-induced changes of micro-mechanical properties of the same samples have been analysed; the depth profiles of hardening correlate with the ion energy loss. A joint contribution of ionization and impact mechanisms in the formation of structural defects under MgO irradiation with Xe ions is considered.H2020 Euratom 2019-2020,633053,2014-2018,GF AP05134257; Ministry of Education and Science of the Republic of Kazakhstan GF AP05134257; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Low-temperature creation of Frenkel defects via hot electron-hole recombination in highly pure NaCl single crystals

The creation spectrum of stable F centres (being part of F-H pairs of Frenkel defects) by synchrotron radiation of 7–40 eV has been measured for highly pure NaCl single crystals at 12 K using a highly sensitive luminescent method. It is shown that the efficiency of F centre creation in a closely packed NaCl is low at the decay of anion or cation excitons (7.8–8.4 and 33.4 eV, respectively) or at the recombination of relaxed conduction electrons and valence holes. Only the recombination of nonrelaxed (hot) electrons with holes provides the energy exceeding threshold value EFD, which is sufficient for the creation of Frenkel defects at low temperature

Nano-scale radiation effects in wide-gap crystals under irradiation by VUV photons

The creation spectra of F centres by synchrotron radiation of 5-35 eV have been measured for Na6Al6Si6O24(NaI)(2x) and Na6Al6Si6O24(NaBr)(2x) optical ceramics at 8 and 80 K. The exciting photons cause the excitation and ionization of halogen ions (6-8 eV) and of an aluminosilicate carcass (8.5-31 eV) or the excitation of Na+ ions (32-35 eV). An exciting photon of 20-26 and 27-31 eV creates two or three electron-hole pairs, respectively. Besides the electron-hole creation mechanism of F centres with the participation of pre-irradiation defects, the basic interstitial-vacancy creation mechanism of Frenkel defect pairs is realized in socialites at high doses of irradiation at 300 K. A Br-0 atom formed at the irradiation in a regular beta-cage can penetrate into a neighbouring cage. As a result, an F centre and a Br-2(-) molecule (H centre) are formed and the interdefect distance in this pair is about I nm. The efficiency of F-H pair creation is especially high under the conditions of multiplication of electron-hole pairs. In contrast to alkali halides the crowdion configuration of interstitials does not exist in sodalites and F-H pairs are stable up to 450 K