Electron spin resonance study on Mo-SiO₂ and Mo-TiO₂ with adsorbed benzene

The study is devoted to ESR-investigation of the primary processes upon chemisorption of benzene molecules onto the molybdenum supported on dispersed SiO₂ and TiO₂ samples. It has been confirmed that benzene chemisorption onto the Mo⁶⁺ species results in one-electron transfer in the ground state and paramagnetic species formation, namely reduced molybdenum species (Mo⁵⁺ species) and radicals of benzene. Computer treatment of ESR experimental data revealed that there are several types of Mo⁵⁺ species and benzene radicals, the assignment of which is proposed

Photoluminescence Study of Eu-Species Incorporated In Lithium Tetraborate and Silica

Steady-state – excitation and emission – photoluminescence spectra of europium species incorporated in single crystal and glassy lithium tetraborate (LTB) and silica are reported. Kinetic features, decay curves of the emission and lifetime data were measured. Spectral characteristics were analyzed with the aim of distinguishing the oxidation state, site-symmetry and morphology of europium species in different solid-state host matrices.Досліджено спектри стаціонарної фотолюмінесценції (збудження та випромінювання) європію, інкорпорованого в монокристалічний і полікристалічний літій тетраборат та кремнезем. Приведено дані кінетичної фотолюмінесценції: криві загасання та час життя збудженого стану іонів європію в зразках. Проведено аналіз спектральних характеристик з метою визначення стану інкорпорованих іонів європію – окислювального та агрегатного, а також локальної симетрії в різних матрицях.Исследованы спектры стационарной фотолюминесценции (возбуждения и излучения) европия, инкорпорированного в монокристаллы и поликристаллы литий тетрабората и кремнезема. Приведены данные кинетической фотолюминесценции: кривые затухания и время жизни возбужденного состояния ионов европия в образцах. Проведен анализ полученных спектральных характеристик с целью определения состояния инкорпорированных ионов европия – окислительного и агрегатного, а также локальной симметрии в разных матрицах

Radioluminescent, thermoluminescent and dosimetric properties of X-ray phosphors

Time-resolved radioluminescence (RL) of X-ray phosphors: BaFCl:Eu, ZnS.CdS:Ag and Y₂О₃:Еu, which exhibited ultraviolet (lmax = 390 nm), yellow-green, (lmax = 530 nm) and red (lmax=620 nm) luminescence respectively, have been measured. For tested phosphors a good proportionality between the light output of the radioluminescence and the dose rate in the region of dose rates from 3 to 45 MGy/s has been obtained. It was also revealed that the emitting properties of all phosphors are preserved after high-dose (10⁴ Gy) and high temperature (500°C) annealing the samples. Thermoluminescent (TL) characterization of Sr₃(PO₄)₂:Eu and BaFCl:Eu under X-ray, beta and gamma irradiation have been performed. Linear TL dose dependence under irradiation dose in the mGy - Gy region was revealed, which makes these phosphors suitable also for luminescence dosimetry in the low doses region. Thus, the main characteristics of phosphors: i) the high conversion efficiency, ii) the good dose-rate proportionality, iii) the radiation stability allow to consider these materials as promising for high-energy and high dose rate dosimetry

Evaluation Of kinetic parameters Of Li(2)b(4)o(7):Mn single crystal

WOS: 000330179200069The kinetic parameters of a newly developed Li2B4O7:Mn single crystal phosphor have been presented. Li2B4O7 single crystal doped with Mn were grown via the Czochralski method. Thermoluminescence (TL) glow curve of Li2B4O7:Mn single crystal exhibits two well separated TL peaks at about 363 and 478 K, later being more intense, with a heating rate of 1 K/s. The high-temperature glow curve at 478 K is important for dosimetric studies of Li2B4O7 (LBO) doped with Mn. The kinetic parameters (activation energy (E), frequency factor (s) and kinetic order (b)) of the main glow peak (478 K) have been calculated using initial rise (IR), isothermal decay (ID) and peak shape (PS) methods. Activation energies obtained by IR, ID and PS were found to be 1.24, 1.18 and 1.20 eV, respectively. Similarly, the frequency factors were determined using isothermal decay and peak shape methods and found as 7.85 x 10(11) and 3.27 x 10(11) s (1), respectively. All results obtained using these methods are compared and discussed. (C) 2013 Elsevier B. V. All rights reserved.Scientific and Technological Research Council of Turkey (TUBITAK) - Hungarian Academy of Sciences (HAS) European Scientific Exchange ProgramTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [2227]This research is supported by the grants from The Scientific and Technological Research Council of Turkey (TUBITAK) - Hungarian Academy of Sciences (HAS) European Scientific Exchange Program (2227)

Thermoluminescence characteristics of Li2B4O7 single crystal dosimeters doped with Mn

WOS: 000330157400033In this study, thermoluminescence (TL) characterization of newly developed Li2B4O7:Mn single crystal phosphor is reported. It is a very attractive material in personal dosimetry because of its near tissue equivalency (Z(eff) = 7.25). The crystal was grown by the Czochralski method from high purity compounds. Glow curve, dose response, and fading and reproducibility properties of this material were investigated. Its TL glow curve showed two well separated peaks at about 105 and 220 degrees C with a heating rate of 2 degrees C s(-1). The main peak at 220 degrees C has a linear dose response of up to 60 Gy. The thermal fading ratio of the material is about 8% for the main peak in 10 days. The results showed that there is no significant variation of TL responses for 15 sequential measurements. Apart from the dosimetric properties above, the TL kinetic parameters of the main peak at 220 degrees C of Li2B4O7:Mn single crystal phosphor were also calculated using the various heating rates method. Activation energy and frequency factor were found as 1.21 eV and 3.75 x 10(11) s(-1), respectively. (C) 2013 Elsevier Ltd. All rights reserved.TUBITAK - HAS European Scientific Exchange ProgramTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [2227]This research is supported by the grants from TUBITAK - HAS European Scientific Exchange Program (2227)

Spectroscopy of Cu- and Ag-doped single crystal and glassy lithium tetraborate: luminescence, optical absorption and ESR study

Photoluminescence (PL), optical absorption (ОА) and ESR spectra have been studied to characterize Cu- and Ag-doped single crystal and glassy Li₂B₄О₇ (LTB). The attribution of LTB:Cu glass PL as one arising from the sets of Cu⁺ ions with slightly different local environments is proposed. The ОА spectra of Cu-doped single crystal and glass are different in the UV and VIS ranges. The ОА and PL features of LTB:Ag single crystal and glassy are different from each other.Исследованы спектры фотолюминесценции (ФЛ), оптического поглощения (ОП) и ЭПР для характеристики монокристаллов и стекла тетрабората лития (ТБЛ), легированных Cu и Ag. Предложена интерпретация ФЛ стекла ТБЛ:Cu, как обусловленной набором Cu⁺ ионов в несколько отличных локальных окружениях. Спектры ОП монокристаллов и стекла отличаются как в УФ, так и в видимой части спектра. Показано, что спектры ОП и ФЛ монокристаллов и стекла ТБЛ:Ag также различны.Дослiджено спектри фотолюмiнесценцiї (ФЛ), оптичного поглинання (ОП) та ЕПР для характеристики монокристалiчного та склоподiбного тетраборату лiтiю (ТБЛ), легованого Cu та Ag. 3апропоновано iнтерпретацiю ФЛ скла ТБЛ:Cu як такої, що зумовлена набором Cu⁺ iонiв у дещо вiдмiнних локальних оточеннях. Спектри ОП монокристалiв та скла ТБЛ:Cu вiдрiзняються один вiд одного як в УФ, так i y видимiй дiлянках спектра. Спектри ОП монокристалiв та скла ТБЛ:Ag також вiдрiзняються один вiд одного