Short-lived primary radiation defects in LiF crystals

Лисицына, Л. А.; Grechkina, T. V.; Korepanov, V. I.; Лисицын, В. М.

doi:10.1134/1.1402223

Cited by 9 publications

(16 citation statements)

References 13 publications

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“…In alkali halides, the separation of intrinsic and extrinsic emissions has usually been performed on the basis of low-temperature excitation spectra for various emissions in the purest samples. Unfortunately, the excitation spectra were not measured for the emissions tentatively ascribed in [21][22][23][24] to the STE luminescence of LiF. originated from the triplet states of intrinsic STEs (see also [10,[21][22][23][24]).…”

Section: +mentioning

confidence: 99%

“…Unfortunately, the excitation spectra were not measured for the emissions tentatively ascribed in [21][22][23][24] to the STE luminescence of LiF. originated from the triplet states of intrinsic STEs (see also [10,[21][22][23][24]). Besides the 3.4 eV emission band, the emission peaked at 4.6 eV can be detected at the excitation of LiF-1 by 16.2 eV photons, which generate separated electrons and holes (see Fig.…”

Section: +mentioning

confidence: 99%

“…intrinsic STEs in nominally pure LiF crystals under electron irradiation [24]. Figure 3 also shows the excitation spectrum of 3.4 eV emissions measured at 8 K for a LiF-2 crystal that contains Na + impurity ions.…”

Section: +mentioning

confidence: 99%

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Low-temperature excitonic, electron–hole and interstitial-vacancy processes in LiF single crystals

Nakonechnyi

Kärner

Lushchik

et al. 2005

J. Phys.: Condens. Matter

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The emission spectra and the excitation spectra of various emissions have been measured in LiF crystals at 9 K using VUV radiation of 10-33 eV. Contrary to the luminescence of selftrapped excitons (3.4 eV), the efficiency of several extrinsic emissions (4.2, 4.6 and 5.8 eV) is very low in the region of an exciton absorption (12.4-14.2 eV). A single exciting photon of 28-33 eV is able to create a primary electron-hole (e-h) pair and a secondary exciton. The tunnel phosphorescence has been detected after the irradiation of LiF by an electron beam or X-rays at 6 K, and several peaks of thermally stimulated luminescence (TSL) at 12-170 K appeared at the heating of the sample. It was confirmed that the TSL at 130-150 K is related to the diffusion of self-trapped holes (V K centres). The TSL peak at ~160 K is ascribed to the thermal ionisation of F′ centres. The TSL at 20-30 K and 50-65 K is caused by the diffusion of interstitial fluorine ions (I centres) or H interstitials, respectively. The TSL peak at ~13 K, the most intense after electron or X-irradiation, cannot be detected after LiF irradiation by VUV radiation, selectively forming excitons or e-h pairs. The creation of a spatially correlated anion exciton and an e-h pair is needed for the appearance of this peak: an exciton decays into an F-H pair, a hole forms a V K and an electron transforms H into I (an F-I-V K group is formed) or an F centre into a two-electron F′ centre (an F′-H-V K group). The analysis of the elementary components of the 9-16 K TSL showed that a phonon-induced radiative tunnel recombination of F′-V K (5.6 eV), F-H (~3 eV) and F-V K (3.4 eV) occurs within these groups.Short Title: Low-temperature excitonic, electron-hole and interstitial-vacancy processes in LiF

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Section: +mentioning

confidence: 99%

Section: +mentioning

confidence: 99%

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Low-temperature excitonic, electron–hole and interstitial-vacancy processes in LiF single crystals

Nakonechnyi

Kärner

Lushchik

et al. 2005

J. Phys.: Condens. Matter

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“…The defects in the subsurface layer, unlike the defects in the bulk of the crystal does not diffuse at these temperatures [10]. This fact suggests that the activation energy of the diffusion for these defects in the subsurface layer is significantly higher than in the bulk of the crystal, where it is 1.07 eV [11,12]. The aggregation of defects in subsurface layers, which is provided by the migration of vacancies, opens possibilities for studying the kinetics of aggregation reactions at different temperatures and for determin ing the activation energy of the diffusion for vacancies in the subsurface layers.…”

Section: Introductionmentioning

confidence: 93%

“…These characteristics for nanocrystals can not be measured using electrical methods, for exam ple, by detecting the electric current provided by the motion of ions in the samples. In this situation, it is promising to use optical methods, in particular, the recording of the kinetics of aggregation defects by the fluorescence or absorption methods [11,12]. In the post radiation period, the aggregation of surface defects was observed in LiF subsurface layers.…”

Section: Introductionmentioning

confidence: 99%

Diffusion and aggregation of subsurface radiation defects in lithium fluoride nanocrystals

et al. 2015

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Lithium fluoride nanocrystals were irradiated by gamma rays at a temperature below the temper ature corresponding to the mobility of anion vacancies. The kinetics of the aggregation of radiation induced defects in subsurface layers of nanocrystals during annealing after irradiation was elucidated. The processes that could be used to determine the activation energy of the diffusion of anion vacancies were revealed. The value of this energy in subsurface layers was obtained. For subsurface layers, the concentrations ratio of vacan cies and defects consisting of one vacancy and two electrons was found. The factors responsible for the differ ences in the values of the activation energies and concentration ratios in subsurface layers and in the bulk of the crystals were discussed.

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Determination of γ-ray flux in a stopped VVR-SM reactor from the color-center formation in LiF

2006

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The absorption and photoluminescence of LiF crystals, irradiated by γ radiation from a stopped reactor and a wet repository, are studied and compared with the corresponding spectra obtained by irradiation with 60 Co γ rays with known power. The contribution of neutron and γ radiation of the reactor to the formation of point and complex radiation defects is determined. The dose dependences of the optical bands are used to determine the intensity of the γ radiation from the reactor and the repository.Wide-spectrum γ radiation accompanying the neutron flux from a reactor causes radiation heating of materials and is ordinarily detected with a calorimeter placed inside the core. The indications of the ionic current in ionization chambers placed above the core of an operating reactor are proportional to the total flux of γ radiation and high-energy neutrons. Ordinarily, the ionization chambers are connected in a scheme which eliminates the contribution of γ radiation and detects only the fast-neutron flux. Solid-state dosimeters based on germanium-doped SiO 2 for determining the absorbed dose of neutron and γ radiation are also used [1]. The intensity of the γ-ray flux can be determined with a silicon detector according to the change in the resistance of neutron-doped silicon [2].Experiments have shown that ~1.25 MeV 60 Co γ rays create structural defects in wide-gap dielectric materials by an inelastic mechanism [3,4]. Consequently, high-energy electromagnetic radiation from a reactor also makes a substantial contribution to the ionization of materials together with neutron fluxes with energy above 0.1 MeV, creates defects in the crystal structure, and changes the electronic structure. To develop a radiation technology for modifying the structure and properties of solids and for safe operation of reactors, it is of great importance to determine the contribution of γ radiation to defect formation during irradiation of materials in reactors by mixed fluxes of neutrons and γ rays.The objective of the present investigation is to separate the γ component from the neutron flux after VVR-SM is shut down and to determine the intensity of γ radiation, using an ionization chamber and a known dosimetric crystal, and by comparing with the effect of 60 Co γ rays with known flux and dose.Experimental Part. Colorless and impurity-free dielectric LiF crystals with the widest band gap 14 eV and an ionic chemical bond were chosen as the objects of investigation. The optical characteristics of the radiation-induced color centers have been well studied for such crystals [2][3][4][5][6][7][8]. For LiF with low atomic numbers, the photoelectric effect is weak and the Compton scattering mechanism prevails. It is known that under ionizing irradiation stable and unstable electronic centers (F n -) and hole-type centers (V n -), both single and multiplet, form when the single centers merge, accumulate in the structure of LiF [9]. A fluorine vacancy, capturing an electron is a well-known stable F center, induced by the radiolysis mechanism in L...

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Short-lived primary radiation defects in LiF crystals

Cited by 9 publications

References 13 publications

Low-temperature excitonic, electron–hole and interstitial-vacancy processes in LiF single crystals

Low-temperature excitonic, electron–hole and interstitial-vacancy processes in LiF single crystals

Diffusion and aggregation of subsurface radiation defects in lithium fluoride nanocrystals

Determination of γ-ray flux in a stopped VVR-SM reactor from the color-center formation in LiF

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