| 1. |
- Omelkov, S. I., et al.
(author)
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Recent advances in time-resolved luminescence spectroscopy at MAX IV and PETRA III storage rings
- 2022. - 1
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In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2380
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Conference paper (peer-reviewed)abstract
- Short-wavelength synchrotron radiation excitation has been an indispensable tool in the studies of the properties of wide gap materials using time-resolved low-temperature luminescence spectroscopy. In recent years, several setups for such investigations have been launched at MAX IV Laboratory and Photon Science at DESY. Two permanently stationed time-resolved luminescence setups at FinEstBeAMS and P66 beamlines are in operation at MAX IV 1.5 GeV and Petra III storage rings, respectively. Mobile luminescence setups have been developed for studies at FemtoMAX and P23 beamlines. FinEstBeAMS, P66 and P23 provide time resolution from ?1/4160 to 100 ps. The FemtoMAX photon source based on an in-vacuum undulator getting an electron beam from the 3 GeV linear accelerator provides an exceptional time resolution of ?1/430 ps, limited by time response of the photodetector. The performance of the setups, achieved milestones and research challenges are discussed for four new luminescence stations available for the research community with the main focus on time-resolved techniques.
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| 2. |
- Feldbach, E., et al.
(author)
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Low-temperature irradiation effects in lithium orthosilicates
- 2006
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In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 250, s. 159-163
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Conference paper (peer-reviewed)abstract
- The emission spectra of lithium orthosilicates (Li4SiO4) ceramics have been measured in the range of 1.8-5.8 eV under irradiation by 6-30 eV photons or 1-30 keV electrons at 6-300 K. The tunnel recombination phosphorescence, as well as luminescence, stimulated by 1.5-2.5 eV photons has been detected in the sample preliminarily irradiated at 6 or 80 K. The main peaks of thermally stimulated luminescence (TSL) in the irradiated ceramics have been observed at 72, 118 and 265 K. The creation spectra of the 118 K TSL peak, as well as the excitation spectrum of photostimulated luminescence (PSL) span the region of the intrinsic absorption of a lithium orthosilicate (9-30 eV). The intensity of PSL and the TSL peaks in Li4SiO4 ceramics prepared in hydrogen/argon atmosphere is several times lower than that in the mainly investigated Li4SiO4 ceramics prepared in the atmosphere of dry argon. The optical characteristics of Li4SiO4 are compared with the ones known for Li2O and SiO2. Low-temperature luminescent methods are promising for the investigation of electron-hole processes and radiation defects serving as the traps for tritium released in D-T fusion reactor blanket systems. (c) 2006 Elsevier B.V. All rights reserved.
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| 3. |
- Kotlov, A, et al.
(author)
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Luminescence study of self-trapped holes in pure and Fe- or Mo-doped ZnWO4 crystals
- 2004
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In: LUMDETR2003. - : Elsevier BV. ; 38, s. 715-715
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Conference paper (peer-reviewed)abstract
- Thermostimulated and photostimulated luminescence of ZnWO4, ZnWO4:Fe and ZnWO4:MO Crystals irradiated at low temperatures by X-rays or UV photons was studied in the temperature range 4.2-300 K in order to clarify the creation and recombination processes of the elementary colour centres. The connection of the luminescence phenomena with the self-trapped holes has been revealed. (C) 2003 Published by Elsevier Ltd.
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| 4. |
- Nagirnyi, V, et al.
(author)
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Luminescence study of pure and Fe- or Mo-doped ZnWO4 crystals
- 2004
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In: Radiation Measurements. - : Elsevier BV. - 1879-0925 .- 1350-4487. ; 38:4-6, s. 519-522
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Journal article (peer-reviewed)abstract
- ZnWO4, ZnWO4 : Fe and ZnWO4 : Mo crystals were investigated by the methods of time-resolved spectroscopy in the temperature range of 4.2-300 K. It is shown that the Mo and Fe impurities significantly reduce the light yield of ZnWO4. The main 2.5 eV emission of ZnWO4 and the 1.77 eV emission band of ZnWO4 : Mo are shown to originate from the triplet excited state of the WO6 and MoO6 complex, respectively. In ZnWO4 : Fe,Mo the MoO6 emission band is shifted to lower energies due to the perturbing influence of the iron impurity. No perturbing effect of Fe or Mo ions was observed for the main emission of ZnWO4 : Fe and ZnWO4 : Mo. The creation spectrum of self-trapped holes was measured for ZnWO4, ZnWO4 : Fe and ZnWO4 : Mo crystals in the energy region of 4-30 eV. (C) 2004 Elsevier Ltd. All rights reserved.
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| 5. |
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| 6. |
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| 7. |
- Nagirnyi, V, et al.
(author)
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Emission decay kinetics in a CaWO4 : Bi crystal
- 2005
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In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 537:1-2, s. 61-65
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Journal article (peer-reviewed)abstract
- The decay kinetics of the 2.88 eV emission of pure and Bi-doped CaWO4 crystals has been studied in the temperature region of 4.2-300 K. The decay components connected with the radiative transitions from the triplet excited states of regular WO42- oxyanionic complexes and WO42- complexes perturbed by Bi3+ ions (WO42-(Bi3+) centres) have been identified. It is shown that WO4(Bi3+) centres can be excited directly above the edge of the fundamental absorption of CaWO4, or due to the energy transfer from the metastable state of a Bi3+ ion at the excitation in the Bi3+ absorption band at 4.4e.V. At temperatures T> 170 K, the excited state of the WO42-(Bi3+) centre is thermally ionised, giving rise to phosphorescence in the blue spectral region. These processes are compared with those known for excitons in PbWO4 crystals.
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| 8. |
- Nagirnyi, V, et al.
(author)
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Energy transfer in ZnWO4 and CdWO4 scintillators
- 2002
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In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 486:1-2, s. 395-398
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Journal article (peer-reviewed)abstract
- A systematic spectroscopic study of oriented single ZnWO4 crystals was performed using UV and synchrotron excitation. Emission and phosphorescence spectra in the energy region 1-4 eV as well as reflection spectra and excitation spectra of various emissions and phosphorescence in the energy region 3.5-32eV were studied at 4.2-300K using synchrotron radiation. The results are compared to those available for CdWO4. The peculiarities of the band structure and those of excitonic and electron-hole processes in the systems investigated are discussed.
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| 9. |
- Nagirnyi, V, et al.
(author)
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Iron-related luminescence centers in ZnWO4 : Fe
- 2002
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In: Radiation Effects and Defects in Solids. - : Informa UK Limited. - 1042-0150 .- 1029-4953. ; 157, s. 1123-1123
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Journal article (peer-reviewed)abstract
- A systematic spectroscopic study of single ZnWO4 :Fe crystals with different iron concentrations has been performed under excitation by ultraviolet light, by synchrotron radiation or under photostimulation by near-infrared light. The luminescence of Fe3+-related centres has been studied. It is shown that iron centres of different types efficiently promote the formation of crystal defects at low temperatures. Electrons and holes can be trapped near Fe2+ or Fe3+ ions, which is further revealed in phosphorescence, thermostimulated or photostimulated luminescence. At room temperature the main effect of iron impurity is to reduce the light yield of a ZnWO4 scintillator.
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| 10. |
- Nagirnyi, V, et al.
(author)
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Separation of excitonic and electron-hole processes in metal tungstates
- 2003
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In: Journal of Luminescence. - 0022-2313. ; 102, s. 597-603
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Journal article (peer-reviewed)abstract
- Absorption, reflection and emission polarization spectra of CdWO4 crystals have been studied in the region 3.5-30 eV in order to distinguish the excitonic and electron-hole processes in the vicinity of the band gap. The following parameters have been defined from the Urbach tail study at 6-300 K: E-0 = 5 eV, sigma(0) = 0.31, homega = 70 meV (565 cm(-1)). Excitonic processes have been shown to dominate at excitation of tungstate crystals in the lower part of the conduction band. Excitons are formed due to the transitions into the tungstate W5d states hybridized with O6p and possess a very strong tendency for self-trapping. Free electrons and holes can be created at the energies 1-2 eV (depending on the crystal) higher than the bottom of the conduction band due to the transitions into cationic states. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 11. |
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| 12. |
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| 13. |
- Kotlov, A., et al.
(author)
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Excited states of molybdenum oxyanion in scheelite and wolframite structures
- 2007
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In: Radiation Measurements. - : Elsevier BV. - 1350-4487 .- 1879-0925. ; 42:4-5, s. 767-770
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Journal article (peer-reviewed)abstract
- Scheelite CdMoO4 and wolframite eCdWO(4):MO (0.04-0.4wt%) single crystals were studied using the time-resolved spectroscopy under UV excitation over a temperature range of 1.85-300K. The threshold energies for the creation of free charge carriers were measured using the method of photostimulated luminescence. The decay kinetics of the main emission in CdMoO4 and the molybdenum-related emission in CdWO4:MO was studied and the parameters of the triplet excited states of molybdenum-related oxyanions were calculated. (C) 2007 Elsevier Ltd. All rights reserved.
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