Host and defect-related luminescence in Rb 2 KTiOF 5 oxyfluoride crystals irradiated by fast electrons

The paper presents a comparative analysis of RKTF crystals (full name single crystals Rb 2 KTiOF 5 ), and RKTF + e crystals, single crystals irradiated on a cyclotron by fast electrons Rb 2 KTiOF 5 . The crystals were grown by slow solidification method. The study was conducted at a temperature from 7 to 400 K for various types of optical and radiation effects. Spectra of photoluminescence (PL) and X-ray excited luminescence (XRL) in region of 1.5-5.5 eV, time-resolved pulse cathode-luminescence (PCL) spectra, the temperature depending of the XRL, luminescence decay kinetics were studied. Single crystal RKTF are transparent from microwave up to the edge of the long-wave fundamental absorption (near UV range). We detected three luminescence bands for RKTF, in the visible spectral region, that were attributed to radiative annihilation of intrinsic excitons (2.25 eV), recombinaion-type luminescence (2.1 eV) and luminescence of higher TiOF 5 complexes (1.9 eV), for all emission bands characterized by great (∼1.5-1.8 eV) Stokes shift. The exponential component with lifetime of approximately 19 μs was found in the PCL decay kinetics at 2.25 eV. In the crystal RKTF + e we detected new luminescence bands 2.6 eV and 3.2 eV and the disappearance of the RKTF luminescence bands. Stokes shift of the band 3.2 eV of the RKTF + e crystal is much smaller and is equal to 0.7 eV. Excitation of the band 3.2 eV occurs in the field of crystal transparency, which indicates the defective nature of the glow. PCL decay kinetics at 2.0 and 2.5 eV has a complex nature and consists of at least two components with a life time of 0.5 ms and 6 ms, that significantly more in comparison with RKTF. Irradiation by fast electrons of crystals Rb 2 KTiOF 5 led to entirely new optical properties and suppression of self-luminescence of the crystals. © Published under licence by IOP Publishing Ltd.This work has been partially supported by the Ministry of Education and Science of the Russian Federation – basic part of the government mandate (project No. 3.8302.2017/8.9) and Act 211 Government of the Russian Federation (contract No. 02.A03.21.0006, the Center of Excellence “Radiation and Nuclear Technologies”) and COST Action TD1401 "FAST”. The authors thank to Dr. S. Omelkov (University of Tartu, Estonia) for help in PCL experiments and M. Sarychev (UrFU) for support in low temperature measurements

Luminescence spectroscopy of K3WO3F3 oxyfluoride crystals

Spectra of photoluminescence (PL) in region of 1.5-5.5 eV, PL excitation spectra (3-22 eV), PL decay kinetics, the temperature dependence of the PL were measured for single crystals and ceramics K3WO3F3 as well as irradiate ceramics K3WO3F3. Synchrotron radiation was used for low temperature PL experiments with time resolution. Single crystals are transparent in microwave, visible and near UV range, inter-band transition energy is Eg = 4.3 eV. The intrinsic luminescence of tungstates is usually ascribed to the radiative relaxation of exciton-like excitations localized on WO6 octahedra or WO4 tetrahedra. In K3WO3F3 the wide band luminescence in the region of 2.5 eV with the Stokes shift of 1.5 eV with the microsecond decay kinetics is connected with luminescence of triplet self-trapped excitons (STE). This luminescence is formed by electronic transitions in [WO3F3] octahedron. Different distortion of KWOF crystal lattice is manifested in the change of the Stokes shift of STE luminescence band. The 3.2 eV emission band in low-temperature PL spectrum with decay times of 1.8 ns and 11 ns corresponds to singlet STE luminescence. A new 2.9 eV emission band is discovered in low-temperature PL spectrum in the samples irradiated by fast electrons (E = 10 MeV, D = 160 kGy). This emission band is excited not intracenter mechanism, and through the creation of excitons bound on the defects. It is suggested that it is F-like centers of anionic sublattice induced by the mechanism of elastic collision. © 2016 Author(s)

Theoretical and Methodological Approaches to the Supply Chain Strategies Role and Analysis of Seaport Competitiveness in the Far East of Russia

Under market conditions, competitiveness is the main quality of any subject, whether it is an enterprise or such a complex structure as a seaport. Competitiveness was considered by many authors abroad and in Russia from different positions: cost approach, innovative approach, supply chain. Each author endured a certain aspect as the main one for analysis. The article is based on the analysis of different points of view and study object features, substantiates the essence of competitiveness through an integrated approach, since the seaport, performing a complex of specific services, fights for demand at different levels: from international to intra-port. The aim of the study was the systematization of theoretical and methodological approaches to the analysis of seaport competitiveness in the Russian Far East for the further development of proposals on competitiveness improvement. Based on the analysis, they substantiated the significance of seaports in the modern world economy and the economy of the Russian Far East. They evaluated the development potential of the Far Eastern ports. On the basis of an integrated supply chain, the competitiveness of the seaports of the Far East of Russia was assessed

Luminescence of Li6Gd(BO3)3 crystals upon ultraviolet and inner-shell excitations

The paper presents the results of the study on luminescence and electronic excitations in Li6Gd(BO3)3 single crystals. The optical and luminescence spectroscopy with a sub-nanosecond time resolution upon selective photoexcitation in the energy range from 3.0 to 650 eV was used to investigate in detail the luminescence of both the Gd3+ host ions and Ce3+ impurity ions as well as the processes of energy transfer between them. The intrinsic ultraviolet emission at 3.95-3.97 eV due to Pj6→S7/28 transitions in the Gd3+ host ion and the fast luminescence at 2.8-3.0 eV due to 5d→4f1 dipole-allowed transitions in the Ce3+ impurity ion were studied upon excitations through the intracenter, charge transfer, band-to-band, and inner-shell transitions. The specificity of the energy transfer upon excitation of photoluminescence in the energy range of absorption of the inner shells of different atoms of the crystal, as well as in the energy region of the giant resonance of 4d-4f transitions was revealed. On the basis of the experimental data, the bandgap Eg=9.3 eV, the minimum energy of the 5d→4 f1 and charge transfer transitions were determined. The expected positions of the ground states of the 4fn and 4fn-15d levels of trivalent lanthanide ions as well as the 4fn+1 and 4f n5d levels of divalent ions were calculated for all the lanthanide ions in Li6Gd(BO3)3 host crystal. © 2012 Elsevier B.V. All rights reserved