Time-Resolved Vacuum Ultraviolet Spectroscopy of Er3+ ions in the SrF2 Crystal

The photoluminescence and photoexcitation spectra as well as the luminescence decay kinetics of Er3+ ions in the visible ultraviolet and vacuum ultraviolet (VUV) regions have been studied by the method of low-temperature, time-resolved VUV-spectroscopy on excitation by synchrotron radiation. In the VUV spectral region of the luminescence of SrF2:1% Er3+, the 146.5-nm band with a time of decay of less than 0.6 nsec was revealed together with the well-known emission band at 164.3 nm (decay constant in the microsecond range). Its possible nature is discussed. The specific features of the formation of photoexcitation spectra of the f-f and f-d transitions in the Er3+ ion are considered. Competition between the processes of excitation of f-f and d-f luminescence has been revealed. It manifests itself in the inverse relationship of their photoexcitation spectra in a range of energies of incident photons that are close to the position of the 4fn-15d configuration levels. © 2005 Springer Science+Business Media, Inc.This work was carried out with the support of grants from the Russian Fundamental Research Foundation (05-02-16530), "Universities of Russia (UR 02.01.433), Ural Scientific Center Promising Materials" CRDF (EK-005-XI), and partially from BMBF (05KS8GMD/1)

Vacuum Ultraviolet Excitation of Rare-Earth ion Luminescence in Strontium Fluoride Crystals

The photoexcitation spectra (70-280 nm) of the Eu 3+, Tb 3+, Dy 3+, Er 3+, and Tm 3+ ion luminescence in strontium fluoride crystals are studied at 8 and 295 K by vacuum ultraviolet spectroscopy using synchrotron-radiation excitation. The processes of transfer of the excitation energy to the impurity centers as well as the relaxation mechanisms of the excited high-energy states of the rare-earth ions are analyzed. The bands corresponding to the interconfiguration 4f-5d transitions and the charge-transfer bands are identified in the photoexcitation luminescence spectra. ©2005 Springer Science+Business Media, Inc.The present work was supported in part by the Russian Foundation for Basic Research (Grant 05-02-16530), by the Program “Russian Universities” (Grant UR.02.01.433), by REC-005 (ЕК-005-XI), and BMBF (05KS8GMD/1)

Luminescence mechanism and energy transfer in cesium metavanadate CsVO 3

Photoluminescence properties and relaxation dynamics of electronic excitations in cesium vanadate CsVO 3 have been studied upon pulse laser excitation in the wide temperature range of 6.5–300 K. A vibronic structure observed in low-temperature PL spectra is considered and interpreted. Peculiarities of luminescence relaxation dynamics and emission spectra of CsVO 3 along with the appearance of the vibronic structure are explained in terms of strong electron-phonon coupling of excited electronic states and centrosymmetric vibrational modes in [VO 4 ] 3- center. A new approach in an interpretation of luminescence processes in vanadates is demonstrated. © 2019 Elsevier Ltd16.5186.2017/8.9The work was supported by Act 211 Government of the Russian Federation , contract № 02.A03.21.0006 . I.A.W. thanks for financial support Minobrnauki initiative research project № 16.5186.2017/8.9 . Authors thank Dr. Mathijs de Jong (Utrecht University) for his kind assistance in laser experiments and Prof. Boris V. Shulgin for fruitful discussions of this work

Phase Transition, Radio- and Photoluminescence of K3Lu(PO4)2 Doped with Pr3+ Ions

Luminescent 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

Testing Performance of Pr3+-doped KLuP2O7 upon UV-, Synchrotron X-Ray and Cathode-Ray Excitation

The luminescent characteristics of the double phosphate KLuP2O7 doped with Pr3+ ions, a promising optical material for scintillator applications, were investigated using various experimental spectroscopic techniques. KLuP2O7:Pr3+ shows Pr3+ emission associated with interconfigurational 4f15d1→4f2 transitions located in the UV range (250–320 nm), intraconfigurational 4f2→4f2 transitions (weak lines in the visible spectral range) and defect-related luminescence. The light output of X-ray or cathode ray excited Pr3+ 4f15d1→4f2 luminescence is found to be nearly independent of temperature in the range of 90–400 K. The output of pulsed cathode luminescence shows thermal quenching above 450 K characterized by an activation energy of about 0.5 eV. Upon excitation with pulsed cathode rays or high-frequency (~8 MHz) X-ray synchrotron radiation, the luminescence decay kinetics of Pr3+ 4f15d1→4f2 transitions are dominated by a decay component with lifetime of about 20 ns. An additional slower decay component with lifetime of 75 ns was observed upon cathode ray excitation and was shown to result from delayed host-to-impurity energy transfer. The latter, in turn, originates from re-trapping of charge carriers at defect-related traps whose presence was demonstrated by thermoluminescence measurements. Parameters of the trapping centers were estimated. Peculiarities of host-to-impurity energy transfer are analysed and 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 ) and RFMEFI62117X0012 project as well as by Estonian Research Council (project PRG629 ) and Estonian Centre of Excellence in Research “Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics” TK141 (2014-2020.4.01.15-0011) . E. Trofimva is thankful for support by European Regional Development Fund (Dora Plus program). 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. The support of Department of Biotechnology, Univ. Verona (FUR funding scheme) is gratefully acknowledged

Intrinsic electronic excitations and impurity luminescent centres in NaMgF3 and MgF2 doped with Yb2+

The relaxation pathways of states in the energy region of the fundamental absorption of NaMgF3:Yb2+ and MgF2:Yb2+ are investigated using time-resolved vacuum ultraviolet spectroscopy. For NaMgF3:Yb2+, excitation into intrinsic free exciton states or above the band gap results in emission features associated with self-trapped excitons and impurity-trapped excitons. Excitation into host-related states of MgF2:Yb2+ similarly exhibits self-trapped exciton emission as well as emission from Yb2+ 4f135d states. The excitation features related to Yb2+ 4f14→4f135d transitions are interpreted using semi-empirical crystal field models. For both materials, the interplay between intrinsic distortions and Yb impurity centres, as the excitation wavelength and sample temperature are varied, is presented and analysed. © 2019 Elsevier B.V

VUV-UV 5d-4f interconfigurational transitions of Nd3+ in BaMgF4 ferroelectric crystals

BaMgF4 single crystals doped with Nd3+ are of great interest as possible active media for VUV-UV and mid-IR all solid-state lasers. The luminescence spectroscopy and the excited state dynamics of these crystals are investigated for the first time upon VUV excitation using synchrotron radiation. The material shows fast Nd3+ 5d-4f emission upon direct VUV excitation into Nd3+ 5d levels. The decay kinetics of the Nd 3+ 5d-4f emission in this host lattice upon direct VUV excitation of 5d levels is characterized by a lifetime of about 14 ns with no significant rise after the excitation pulse. No significant temperature dependence of the lifetime is observed within the range 8-300 K. © 2014 Elsevier B.V