Cathodoluminescence of Single-Crystalline and Pressed CaF[2]:Yb{2+}, Yb{3+}
Автор(ы): Korepanov V. I.*Bekmyrza K. Zh.*Lisitsyn V. M.*Garibin E. A.*Gusev P. E.*Demidenko A. A.*Krutov M. A.*Mironovc I. A.*Reiterov V. M.*Baktybekov K. S.*
Реферат: We have studied the pulsed cathodoluminescence spectra and kinetics of CaF[2]:Yb{2+}, Yb{3+} (3 mol % YbF[3]) single crystals and pressed samples under excitation with nanosecond electron pulses and determined the characteristic times and intensities of nanosecond and microsecond emission decay components at temperatures from 15 to 300 K. The results demonstrate that deformation pressing in vacuum at 1150 C followed by annealing in a CF[4] atmosphere at 1180 C has an insignificant effect on the emissive properties of CaF[2]:Yb{2+},Yb{3+}.
Ab initio calculations of the atomic and electronic structure of MgF[2] (011) and (111) surfaces
Автор(ы): Vassilyeva A. F.*Eglitis R. I.*Kotomin E. A.*Dauletbekova A. K.*
Объем документа: С. 515-518
МРНТИ: 29.19.16
Ключевые слова: атомная структура фторида магния*расчеты неэмпирические*оптические свойства фторида магния*полярные поверхности*
Реферат: The results of ab initio slab calculations of surface relaxations, rumplings and charge distribution for the different terminations of the MgF[2] (011) and (111) polar surfaces are presented and discussed. We have employed the computer code CRYSTAL with the Gaussian basis set and the hybrid B3PW exchange-correlation functional. Despite the ionic nature of the chemical bonding at both surfaces, a considerable decrease of the optical band gap is predicted (1.3 eV or 10%) for the (111) surface as compared to the bulk.
Luminescent mesoporous colloidal silica: A nanoporous substrate for photosensitization of lanthanide ions
Реферат: Nearly monodisperse, mesoporous, colloidal silica spheres were treated with aminopropyltriethoxysilane and subsequently calcined to generate luminescent mesoporouscolloidal silica (LMCS), with broad bimodal visible emission and high surface areas exceeding 700 m2/g. The combination of high surface area and localization of luminescence centers at the surface provides opportunities for exploring new efficient photophysical/photochemical relaxation processes with the metal-free/dye-free luminescent silica sol-gel materials. Addition of LMCS to solutions of TbCl3 or EuCl3 results in efficient lanthanide sensitization. The enhancement in lanthanide emission is accompanied by a quenching of LMCS emission.
Pulsed Cathodoluminescence of F2 Centers in Undoped and Doped LiF Crystals
Реферат: This work examines the generation of F[2] centers in LiF, LiF(O,OH), and LiF:U(O,OH) crystals by electron pulses at 300 K. We discuss nanosecond and microsecond mechanisms for the excitation of pulsed cathodoluminescence of F[2] centers in the crystals.
Activated Cathodoluminescence of Oxygen-Containing LiF Crystals
Автор(ы): Lisitsyna L. A.*Korepanov V. I.*Lisitsyn V. M.*Eliseev A. E.*Timoshenko N. N.*Dauletbekova A. K.*
Реферат: Cathodoluminescence of oxygen_containing LiF crystals (LiF-O, LiF-O,OH, LiF-WO3) is studied by pulsed spectrometry with nanosecond resolution upon excitation of crystals by a single electron beam pulse at 15K.
Recombination Luminescence of CaSO4: Tb3+and CaSO4 : Gd3+ Phosphors
Реферат: A comparative study of the excitation of luminescence by VUV radiation as well as of thermally and photostimulated luminescence has been carried out for CaSO4:Tb3+ and CaSO4:Gd3+ phosphors, where Na+ or F? ions are used for charge compensation. The distinction in hole processes for the phosphors with Na+ or F? compensators is determined by the differing thermal stability of the holes localized at/near Tb3+Na+ and Gd3+Na+ (up to 100-160 K) or at/near Tb3+F? V Ca and Gd3+F? V Ca centers involving also a cation vacancy (up to 400-550 K). Tunnel luminescence in the pairs of localized electrons and holes nearby Tb3+ or Gd3+ has been detected. The mechanisms of electron-hole, hole-electron and tunnel recombination luminescence as well as a subsequent released energy transfer to RE3+ ions are considered.
Pure kinetic K-essence as the Cosmis speed-up
Автор(ы): Tsyba P. Y.*Kulnazarov I. I.*Yerzhanov K. K.*Myrzakulov R.*
Объем документа: С. 1876-1886
МРНТИ: 29.05.03
Ключевые слова: модели расширения Вселенной*темная энергия*космология*квантовая теория поля*
Реферат: In this paper, we consider three types of k-essence. These k-essence models were presented in the parametric forms. The exact analytical solutions of the corresponding equations of motion are found. It is shown that these k-essence models for the presented solutions can give rise to cosmic acceleration.
Further investigation of the elastic scattering of 16O, 14N and 12C on the nucleus of 27Al at low energies
Автор(ы): Amangeldy N.*Hamada Sh.*Burtebayev N.*Gridnev K. A.*
Реферат: The angular distribution for the elastic scattering of O, N and C on Al was measured at an energy of 1.75 MeV per nucleon in the DC-60 INP NNC (Institute of Nuclear Physics, National Nuclear Centre) cyclotron located in Astana in order to study the elastic scattering mechanism in these nuclear systems. The experimental results were analyzed with the help of the optical potential code SPI-GENOA. Good agreement between the experimental data and the theoretical calculations was obtained by using suitable optical potential parameters. The elastic scattering of O, N and C on Al does not reveal any unusual features or threshold anomaly at this energy.
Pulsed Photo- and Cathodoluminescence of LiF Crystals Doped with Tungsten Oxide
Автор(ы): Lisitsyna L. A.*Korepanov V. I.*Timoshenko N. N.*Dauletbekova A. K.*
Объем документа: С. 175-181
МРНТИ: 29.31.23
Ключевые слова: методы импульсной спектрометрии*наносекундное разрешение*активированные катодолюминесценции*кристаллы оксида вольфрама*
Реферат: We have studied the spectral and kinetic characteristics of activated photo- and cathodoluminescence of LiF-O and LiF-WO3 crystals in the spectral range of 3.6-1.6 eV using methods of pulsed spectrometry with nanosecond time resolution in the temperature range of 15-300 K and in the range of ionizing radiation dose absorbed by crystals of 102-2 x 103 Gy.
Antiproton scattering off He and He nuclei at low and intermediate energies
Автор(ы): Uziko Yu. N.*Haidenbauer J.*Prmantayeva B. A.*
Реферат: Antiproton scattering off He and He targets is considered at beam energies below 300 MeV within the Glauber-Sitenko approach, utilizing the N-N amplitudes of the Julich model as input. A good agreement with available data on differential p{-4}He cross sections and on p{-3}He and p{-4}He reaction cross sections is obtained. Predictions for polarized total p{-3}He cross sections are presented, calculated within the single-scattering approximation and including Coulomb-nuclear interference effects. The kinetics of the polarization buildup is discussed.
