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Vasil'Ev A.N.,Moscow State University | Gektin A.V.,Institute for Scintillation Materials of Ukraine
IEEE Transactions on Nuclear Science

This work is directed to analysis and description of the factors which determine the efficiency of inorganic scintillators. The interconnection of different stages of track formation and relaxation is analyzed. The hierarchy of the scales of different processes in scintillators is discussed. The main attention is paid on the evolution of energy and spatial distribution of excitations in the excited region in scintillators. Different types of recombination - geminate and stochastic - and their features are considered, both in cases of low and high concentration of excitations and impurities. The spatial structure of the track after thermalization is discussed, with discriminating high-energy and low-energy part of the track of ionizing particle. Main features of thermalization and formation of thermalization length in different types of crystals with simple and complex structure and with different phonon spectrum are considered. The peculiarities of these processes in binary and complex halides and the estimation of limits of scintillator efficiency in these crystals are reviewed. Possible mechanism based on Auger relaxation of core hole which enhances the yield in CsI is proposed. The estimations of limiting factors for traditional alkali halide crystals and the perspectives of complex halides are discussed. © 2013 IEEE. Source

Klochkov V.,Institute for Scintillation Materials of Ukraine
Journal of Photochemistry and Photobiology A: Chemistry

Photocatalytic activity of aqueous colloidal solutions of nanoparticles of different nature at UV-irradiation was determined. 2 nm GdYVO4:Eu, 8 × 25 nm GdVO4:Eu, 6 × 40 nm LaVO4:Eu, 2 and 9 nm CeO2, 5 × 10 nm CePO4:Tb and 62 nm C60 nanoparticles were used. Rare earth orthovanadate nanoparticles as well as fullerenes induce radical formation in water. It was shown that intensity of photocatalytic process increases with increase of the linear sizes of orthovanadate nanocrystals. Rare earth orthophosphate nanoparticles do not participate in photocatalytic processes at all. Cerium dioxide nanocrystals inactivate radicals in the water playing a role of a radical sponge. ©2015 Elsevier B.V. All rights reserved. Source

Malyukin Y.V.,Institute for Scintillation Materials of Ukraine
International Conference on Oxide Materials for Electronic Engineering - Fabrication, Properties and Applications, OMEE 2014 - Book of Conference Proceedings

Luminescence and scintillation processes in nanomaterials can differ sufficiently from the same processes in bulk crystals. A range of effects providing such a difference (confinement of electronic and phonon states, Purcell's effect, migration of defects to the surface) are discussed in the paper. © 2014 IEEE. Source

Gektin A.V.,Institute for Scintillation Materials of Ukraine | Belsky A.N.,University Claude Bernard Lyon 1 | Vasil'Ev A.N.,Moscow State University
IEEE Transactions on Nuclear Science

Analysis of the last years theoretical studies and track simulations to conclusion that primary stages (electron scattering and e-h thermalization) play the key role in the following scintillator efficiency. The long thermalization length comparing to Onsager radius is the main reason for geminate pair concentration decrease and later luminescence losses. The easiest way for thermalization length decrease is the scintillation crystal doping or even transfer to the mixed crystals (solid solution). The simple model of modification of electrons scattering and e-h pairs thermalization for the mixed crystals is proposed. It is shown that solid solutions have higher light output independently on the crystal type. Analysis of experimental data confirmed this conclusion. This phenomenon is found for halide, oxide and sulfates scintillators. The similar behavior is typical for mixed anion and/or cation systems. The key role of initial track formation stages is illustrated by the same trend for activated scintillators and pure crystal with intrinsic luminescence. These estimations and experimental data lead to the conclusion that the scintillation efficiency improvement by mixed crystal use can play an important role in the search and development of new scintillators. © 2013 IEEE. Source

Gektin A.,Institute for Scintillation Materials of Ukraine | Shiran N.,Institute for Scintillation Materials of Ukraine | Belsky A.,University Claude Bernard Lyon 1 | Vasyukov S.,Institute for Scintillation Materials of Ukraine
Optical Materials

The work is aimed to research of CsI:Eu single crystals' luminescence at different excitations in the wide temperature range (from 8 to 300 K) and admixture concentration from 10 -4% up to 10 -1% of Eu 2+ ions. This study was directed to separation of different luminescence mechanisms and luminescence quenching explore. It is found that due to the temperature quenching the room temperature yield is decreased in order of magnitude even for heavy Eu doped CsI crystals. Intense low temperature luminescence band at 441-448 nm connected with Eu 2+ 4f 6 5d → 4f 7 radiative transition is observed. The results obtained show that the excitonic mechanism plays the main role in energy transfer process to Eu 2+ ions and this is the reason for relatively low light yield of this emission at RT. The nature of the additional emission bands (410, 450, 480 and 500 nm) are apparently caused by the significant non-isomorphism of cations and/or by the presence of oxygen-containing admixtures. © 2012 Elsevier Ltd. All rights reserved. Source

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