112,112 research outputs found
Unraveling Pr3+ 5d-4f emission in LiLa9(SiO4)6O2 crystals doped with Pr3+ ions
No full textLiLa9(SiO4)(6)O-2 (LLSO) crystals doped with Pr3+ ions were grown using the slow cooling flux method. The crystals were characterized by means of luminescence and optical spectroscopy and luminescence decay measurements upon excitation in UV, VUV and X-ray range including using synchrotron radiation sources. The spectroscopic data revealed the presence Pr3+ 5d <-> 4f emission and excitation bands related to Pr3+ ions replacing La3+ i n two nonequivalent positions, and features related Pr3+ 4f -> 4f emission. The photon cascade emission is not observed in LLSO:Pr3+, since Pr3+ S-1(0) state is above the bottom of 4f(n-1)5d mixed-states band. Apart from the emission features related to Pr3+, a defect-related emission was observed upon UV, VUV, and ionizing radiation excitation. Presence of the defects was shown with thermoluminescence measurements and suggested to be the main reason for suppression the 5d -> 4f emission. Peculiarities of host-to-impurity energy transfer are analyzed and discussed
Luminescence of Pr3+ Impurity Centers and Defects in Sr9Sc (PO4)7:Pr3+
No full textThe spectroscopic characteristics and luminescence decay kinetics of Sr9Sc(PO4)(7):Pr3+(1%) were investigated using synchrotron radiation of ultraviolet (UV), vacuum ultraviolet (VUV) and X-ray ranges, as well as pulsed cathodoluminescence (PCL) methods at temperatures of 10, 90, and 295 K. The luminescence spectra contain three groups of bands and lines. In the UV range, the observed bands correspond to interconfigurational 5d 4f transitions in Pr3+ ions. In the visible spectrum, the wide luminescence band of defects dominates, as well as narrow lines associated with intraconfigurational 4f 4f transitions in Pr3+ ions. When excited by an electron beam (5 Hz), the main component with a decay time approximate to 17 ns dominates in the decay kinetics of the 5d 4f luminescence. The decay kinetics of 5d 4f luminescence upon excitation with high-frequency ( approximate to 8 MHz) synchrotron radiation of the X-ray range contains a fast component ( approximate to 15 ns) against the background of the slow component of the s-range. An effective nonradiative energy transfer is observed from impurity centers to defects, as well as from the host to Pr3+ ions and defects
Luminescence Spectroscopy and Decay Kinetics of Pr3+ Ions in K3LuSi2O7:Pr3+
No full textThe luminescent characteristics of K3LuSi2O7:Pr3+ (1%), which is a promising optical material for the use as a scintillator, have been studied using a set of techniques. The luminescence spectra of K3LuSi2O7:Pr3+ (1%) contain two bands in the UV-range with peaks at 284 and 330 nm, which correspond intraconfigurational 5d 4f transitions in the Pr3+ ions. The radiation in the visible and near IR range (480-850nm) has been represented by the intraconfigurational 4f 4f transitions. The kinetics of 5d 4f-luminescence contains a build-up stage ((rise) approximate to 7-12 ns), nonexponential decay stage ((1/2) approximate to 60 ns), and a slow component of the s-range when excited by high-frequency (approximate to 8 MHz) synchrotron radiation of the X-ray range. The fast component of the decay ( = 54 ns) dominates in the decay kinetics of luminescence along with the build-up stage while the contribution of the s decay component is less than 0.5% at the excitation by an pulse electron beam (5Hz). The excitation spectra of d-f- and f-f-photoluminescence in the ultraviolet and vacuum ultraviolet range that are measured using synchrotron radiation reveal features that are caused by both intracenter transitions and processes related to the energy transfer from the intrinsic electronic excitations to the impurity center
Phase Transition, Radio- and Photoluminescence of K3Lu(PO4)2 Doped with Pr3+ Ions
No full textLuminescent characteristics of K3Lu(PO4)2:Pr3+ (1 and 5 mol.%) microcrystalline powders, a promising optical material for scintillation applications, were investigated using various experimental techniques. The material shows emission features connected with both high intensity interconfigurational 4f15d→4f2 transitions (broad UV emission bands) and intraconfigurational 4f2→4f2 transitions (weak emission lines in the visible range). The output of X-ray excited 4f15d→4f2 emission of Pr3+ increases with a temperature rise from 90 K to room temperature and higher depending on the Pr3+ ions concentration. The high 5% concentration of Pr3+ ions is found to be favourable for the stabilization of a monoclinic phase (P21/m space group) over a trigonal one (P3‾ space group) while emission properties of the material reveal that a phase transition occurs at higher temperatures. Decay kinetics of Pr3+ 4f15d→4f2 emission are recorded upon excitation with high repetition rate X-ray synchrotron excitation and pulse cathode ray excitation. Issues related to a non-exponential decay of luminescence and presence of slow decay components are discussed in terms of energy transfer dynamics. The presence of defects was revealed with thermoluminescence measurements and these are suggested to be the mainly responsible for delayed recombination of charge carriers on the Pr3+ 4f15d states. Some peculiarities of host-to-impurity energy transfer are discussed. © 2020 Elsevier B.V.The work was partially supported by the Ministry of Science and Higher Education of the Russian Federation (through the basic part of the government mandate, project No. FEUZ-2020-0060), Act 211 Government of the Russian Federation (contract № 02.A03.21.0006), STSM grant from COST Action TD1401 ″FAST” as well as by Estonian Research Council (project PRG629) and Estonian Center of Excellence in Research “Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics” TK141 (project No. 2014-2020.4.01.15-0011) by the ERDF funding in Estonia. The time-resolved X-ray excited measurements were performed at the Shared research center SSTRC based on the NovoFEL/VEPP-4 - VEPP-2000 facilities at Budker Institute of Nuclear Physics (Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia) while using experimental equipment funded by RFMEFI62119X0022 project. Authors thank Erica Viviani (University of Verona) for assistance in the synthesis of the samples and Yulya Khatchenko (UrFU, Ekaterinburg) for assistance in the processing the experimental data. F. P. and M. B. thank the Facility “Centro Piattaforme Tecnologiche” of the University of Verona for access to the Thermo ARL X’TRA powder diffractometer
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
Impurity and defect-related luminescence of Ce3+ doped LiLa9(SiO4)6O2 crystals upon UV-VUV, X-ray and cathode ray excitation
No full textWe report on the synthesis and comprehensive characterization of Ce3+ doped LiLa9(SiO4)(6)O-2 (LLSO) crystals, grown using the slow cooling flux method. The luminescence and optical spectroscopic properties and luminescence decay kinetics were studied upon excitation with UV, VUV, X-ray photons and cathode rays. Two impurity Ce3+ centres substituting for La3+ - ions in two nonequivalent crystal positions are observed in LLSO:Ce3+. They are well distinguished spectroscopically in the UV range both in emission and excitation spectra. Apart from emission associated with Ce3+ 5d -> 4f interconfigurational transitions, a low-temperature defect-related emission has been observed upon UV-VUV and higher energy X-ray excitation. Processes lying behind the temperature quenching and host-to-impurity energy transfer are analyzed and discussed
Energy conversion in LiSrPO4 doped with Pr3+ ions
No full textWe report on the time-resolved luminescence spectroscopic characterization of LiSrPO4 doped with Pr3+-ions, that we found potentially attractive for scintillation applications. The spectroscopic study included measurements of photoluminescence, X-ray excited luminescence, thermally stimulated luminescence and time-resolved pulse cathodoluminescence spectra. In addition, luminescence decay kinetics were studied upon high-frequency X-ray and pulse cathode beam excitation. LiSrPO4:Pr3+ showed Pr3+ emission connected with intraconfigurational 4f(2)-> 4f(2) and interconfigurational 4f(1)5d -> 4f(2) transitions. The presence of defects was shown with thermoluminescence measurements and suggested to be the main reason for delayed recombination of charge carriers on Pr3+ 4f(1)5d states. Some peculiarities of host-to-impurity energy transfer are discussed
Problems and prospects of factoring market development in Russia
No full textUnder the conditions of the economic crisis and fierce competition, companies are able to efficiently use affordable financial resources such as factoring, which is a competitive business financing tool that meets international standards. The benefits of factoring can be seen in all participants of this service. It is beneficial for suppliers in terms of increasing sales, turnover, and reducing cash gaps. Due to the factoring, buyers obtain commodity loans and provide the optimal use of working capital. Commission merchants increase in their revenues and the number of customers, and strengthen their market positions. In the global market, an increase in factoring regardless of the presence or absence of a crisis leads to an increase in the volume of trade flows. In Russia, the popularity of the factoring is low compared to bank loans, especially among small and medium-sized businesses. The paper analyses the composition of the players in this market, examines the dynamics of the volumes of financing provided, the weighted average cost of factoring in comparison with the interest on loans, the number of participants, and financing by industry and region of the country. Based on an analysis of the current situation and long-term market data, the paper summarizes the problems of factoring in Russia, and identifies key factors for factoring market growth in the future.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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