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1.
M.V. Nazarov D.Y. Jeon E.-J. Popovici M.V. Zamoryanskaya 《Solid State Communications》2004,131(5):307-311
Double incorporation of Eu3+ and Tb3+ ions into a CaWO4 crystalline lattice modifies the luminescence spectrum due to the formation of new emission centers. Depending on the activators concentration and nature, as well as on the interaction between the activators themselves, the luminescence color can be varied within the entire range of the visible spectrum. Variable luminescence was obtained when CaWO4:Eu,Tb phosphors with 0-5 mol% activator ions were exposed to relatively low excitation energies as UV (365 and 254 nm). Under high energy excitation such as VUV (147 nm) radiation or electron beam, white light has been observed.This material with controlled properties seems to be promising for the applications in fluorescent lamps, colored lightning for advertisement industries, and other optoelectronic devices. 相似文献
2.
Yu. V. Zorenko V. I. Gorbenko G. B. Stryganyuk V. N. Kolobanov D. A. Spasskii K. Blazek M. Nikl 《Optics and Spectroscopy》2005,99(6):923-931
The luminescence of excitons and antisite defects (ADs) was investigated, as well as the specific features of the excitation energy transfer from excitons and ADs to the activator (Ce3+ ion) in phosphors based on Lu3Al5O12:Ce (LuAG:Ce) single crystals and single-crystalline films, which are characterized by significantly different concentrations of ADs of the Lu Al 3+ type and vacancy-type defects. The luminescence band with λmax = 249 nm in LuAG:Ce single-crystal films is due to the luminescence of self-trapped excitons (STEs) at regular sites of the garnet lattice. The excited state of STEs is characterized by the presence of two radiative levels with significantly different transition probabilities, which is responsible for the presence of two excitation bands with λmax = 160 and 167 nm and two components (fast and slow) in the decay kinetics of the STE luminescence. In LuAG:Ce single crystals, in contrast to single-crystal films, the radiative relaxation of STEs in the band with λmax = 253.5 nm occurs predominantly near Lu Al 3+ ADs. The intrinsic luminescence of LuAG:Ce single crystals at 300 K in the band with λmax = 325 nm (τ = 540 ns), which is excited in the band with λmax = 175 nm, is due to the radiative recombination of electrons with holes localized near Lu Al 3+ ADs. In LuAG:Ce single crystals, the excitation of the luminescence of Ce3+ ions occurs to a large extent with the participation of ADs. As a result, slow components are present in the luminescence decay of Ce3+ ions in LuAG:Ce single crystals due to both the reabsorption of the UV AD luminescence in the 4f-5d absorption band of Ce3+ ions with λmax = 340 nm and the intermediate localization of charge carriers at ADs and vacancy-type defects. In contrast to single crystals, in phosphors based on LuAG:Ce single-crystal films, the contribution of slow components to the luminescence of Ce3+ ions is significantly smaller due to a low concentration of these types of defects. 相似文献
3.
Europium doped BaAl12O19 powder phosphors have been synthesized by combustion process within few minutes. The phosphors have been characterized by XRD, SEM, FT-IR, EPR and PL techniques. The EPR spectrum exhibits an intense resonance signal at g=1.96 characteristic of Eu2+ ions. In addition to this two weak resonance signals have been observed at g=2.28 and g=4.86. The population of the spin levels (N) for the resonance signal at g=1.96 is calculated as a function of temperature. By post-treating the phosphor at 1350 °C under a reducing atmosphere, it is observed that the population of spin levels has been increased five times. The excitation spectrum shows a peak at 326 nm with a shoulder at 290 nm. Upon excitation at 326 nm, the emission spectrum exhibits a well defined broad band with maximum at 444 nm emitting a blue light corresponding to 4f65d→4f7 transition. The luminescence intensity also has been enhanced to 60% by post-treating the phosphor at 1350 °C under a reducing atmosphere. 相似文献
4.
A. N. Starukhin D. K. Nelson D. L. Fedorov D. K. Syunyaev 《Physics of the Solid State》2017,59(2):236-241
The luminescence excitation spectra of localized excitons in GaSe0.85Te0.15 solid solutions have been investigated at the temperature T = 2 K. It has been shown that the excitation spectra of excitons with the localization energy ε > 10 mV exhibit an additional maximum M E located on the low-energy side of the maximum corresponding to the free exciton absorption band with n = 1. It has been found that the shift in the position of the maximum M E in the excitation spectrum with respect to the energy of detected photons increases as the energy of detected photons decreases, i.e., with an increase in the localization energy of excitons. Under the resonant excitation of localized excitons by a monochromatic light from the region of the exciton emission band, in the exciton luminescence spectrum on the low-energy side from the excitation line, there is also a maximum of the luminescence (M L ). The energy distance between the position of the excitation line and the position of the maximum in the luminescence spectrum increases with a decrease in the frequency of the excitation light. The possible mechanisms of the formation of the described structure of the luminescence excitation and exciton luminescence spectra of GaSe0.85Te0.15 have been considered. It has been concluded that the maximum M E in the excitation spectrum and the maximum M L in the luminescence spectrum are attributed to electronic–vibrational transitions with the creation and annihilation of localized excitons, respectively. 相似文献
5.
The specific features of the absorption, photoluminescence, x-ray luminescence, thermally stimulated luminescence, and photostimulated luminescence spectra of CsBr: Eu2+ single crystals grown using the Bridgman method are investigated in the temperature range 80–500 K at the highest possible dopant content (0.1–0.4 mol % EuOBr in the batch) required for preparing perfect crystals. It is shown that an increase in the dopant content leads to a broadening of the absorption and photoluminescence excitation bands with maxima at wavelengths of 250 and 350 nm due to the interconfigurational transitions 4f7(8S7/2) → 4f65d(e g , t2g) in Eu2+ ions. The photoluminescence and photostimulated luminescence spectra of CsBr: EuOBr single crystals (0.1–0.4 mol % EuOBr) contain a band at a wavelength of λmax=450 nm and bands at wavelengths of λmax=508–523 and 436 nm. The last two bands are assigned to Eu2+-VCs isolated dipole centers and Eu2+-containing aggregate centers, respectively. It is revealed that the intensity of the luminescence associated with the aggregate centers (λmax=508–523 nm) is maximum at an EuOBr content of less than or equal to 0.1 mol % and decreases with an increase in the dopant content. The possibility of forming CsEuBr3-type nanocrystals that are responsible for the green luminescence observed at a wavelength λmax=508–523 nm in CsBr: Eu crystals is discussed. The intensity of photostimulated luminescence in the CsBr: EuOBr crystals irradiated with x-ray photons is found to increase as the dopant content increases. It is demonstrated that CsBr: EuOBr crystals at a dopant content in the range 0.3–0.4 mol % can be used as x-ray storage phosphors for visualizing x-ray images with high spatial resolution. 相似文献
6.
Yu. V. Zorenko A. S. Voloshinovskii G. B. Striganyuk V. I. Gorbenko 《Optics and Spectroscopy》2005,98(4):555-558
The paper reports on a study of exciton luminescence in single crystals (SCs) and single-crystal films (SCFs) of YAlO3, which have substantially different concentrations of vacancy-type and substitutional defects, under excitation by synchrotron radiation near the fundamental absorption edge. The radiative annihilation of excitons in SCFs was shown to occur primarily at regular perovskite lattice sites and to be accompanied by luminescence in a band peaking at λmax = 295 nm with τ = 5.2 ns. In contrast to SCFs, the radiative exciton decay in YAlO3 SCs takes place predominantly near vacancy-type defects (F+ and F centers) and is accompanied by luminescence in the bands at λmax = 350 nm (τ = 2.5 ns) and 440 nm (τ1 = 1.9 ns, τ2 = 30 ms). Photoexcitation in the 175-nm band of YAlO3 SCs revealed photoconversion of the centers F → F+. 相似文献
7.
I. N. Ogorodnikov I. N. Sedunova V. Yu. Ivanov L. I. Isaenko 《Physics of the Solid State》2012,54(10):2039-2050
The subnanosecond time-resolved ultraviolet luminescence of Li6Gd(BO3)3: Ce crystals under selective excitation by ultrasoft X-rays in the region of the 4d??4f core transitions at temperatures of 7 and 293 K has been investigated for the first time. The performed investigation has revealed the following features: an intense fast component of the luminescence decay kinetics in the subnanosecond range due to the high local density of electronic excitations and the processes of Auger relaxation of the core hole; the modulation of the luminescence excitation spectrum by the ??giant resonance?? absorption band of the 4d-4f photoionization in the energy range 135?C160 eV; and a new broad luminescence band at an energy of 4.44 eV due to the direct radiative recombination between the genetically related electron in the states of the conduction band bottom and hole in the 4f ground state of the Ce3+ ion. 相似文献
8.
Excitation spectra (T = 75–300 K; λexc = 450–630 nm) which were measured for the R-lines of Cr3+-doped oxides (α-Al2O3, β-Ga2O3) and for different luminescence lines (R-lines, N-lines) of Cr3+-doped spinels (MgAl2O4, ZnAl2O4, ZnGa2O4) are reported. The excitation maxima observed for different luminescence lines of a given compound exhibit considerable differences: 530 nm ? λmaxexc ? 565 nm for MgAl2O4; 530 nm ? λmaxexc ? 580 nm for ZnAl2O4; 545 nm ? λmaxexc 555 nm for ZnGa2O4. According to the interpretation of N-lines to arise from different classes of Cr3+ ion swith different short range orderd, the excitation maximum of one distinct line should entirely correspond to the transition Δ : 4T2 ← 4A2 of that Cr3+ class from which the line arises. By this method spectroscopic data about the different kinds of Cr3+ ions present in a given sample can, therefore, be obtained which are not available from absorption measurements. The experimetal data were found to be in agreement with the results of model calculations. Restrictions which limit the accuracy and relevance of the data are discussed. 相似文献
9.
The structural luminescence spectra of protoporphyrin IX solid solutions in ethanol and hydrochloric acid were obtained under selective laser excitation in the region of the inhomogeneouly broadened pure electronic and vibronic bands at T = 3.8 K. The dependence of the excitation selectivity on the excitation frequency was investigated. The vibrational frequencies of protoporphyrin IX were obtained in the ground and excited electronic states when the excitation frequency has been scanned in the region of pure electronic and vibronic bands, respectively. A universal apparatus is described for the investigation of the absorption and luminescence spectra of polyatomic molecules in the temperature range from 3.5 to 300 K under the dye laser excitation tunable in the spectral region 265–365 nm, 435–730 nm, detection of spectra in the region 300–900 nm with a polychromator and silicon intensified image detector and processing of the spectral information with an optical spectrum analyser controlled with a microcomputer. 相似文献
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11.
Vacuum ultraviolet luminescence of Er3+ ions in LiYF4 and BaY2F8 crystals has been investigated. It is revealed that under excitation by 193 nm radiation from an ArF excimer laser the interconfigurational 5d–4f radiative transitions in Er3+ ions are observed. It is shown that from the LiYF4:Er crystal only the spin-forbidden luminescence (λ = 165 nm) is detected, whereas both the spin-forbidden (λ = 169 nm) and spin-allowed (λ = 160.5 nm) components are observed from the BaY2F8:Er crystal. 相似文献
12.
Excitation of donor-acceptor pair luminescence has been studied in CdTe doped with lithium or chlorine. The excitation spectrum of the lithium acceptor is determined and fitted with the effective mass theory of Baldereschi and Lipari. Revised values of the valence band parameters are deduced: μ = 0.8, δ = 0.054, Ry = 24 meV. The analysis of the 1.45 eV luminescence band in compensated Cl-doped crystals shows the existence of donor-acceptor pair transitions. Three acceptor centers are identified: EA = 89, 111 and 119 meV, and the contribution of a deep donor (ED > 40 meV) is demonstrated. Besides intracentre type excitation transitions of the 1.45 eV band have been observed in non-compensated chlorine-doped crystals. Thus several recombination channels and distinct acceptor states contribute to the composite 1.45 eV luminescence band. 相似文献
13.
A. Cornet J. Collet T. Amand M. Pugnet B.S. Razbirin G. Michailov 《Journal of Physics and Chemistry of Solids》1983,44(1):53-59
We report a study at low temperature of the time resolved luminescence of CdS, excited by two photon absorption. Concerning the so called EHP-LO and P bands, we confirm our results previously obtained on CdSe[1, 2]. (a) At high excitation a broad band (peak position at λ > 495 nm) occurs due to radiative recombination in an electron hole plasma, assisted by the emission of one LO phonon. (b) The simultaneous kinetics of the P line (λ ? 490.5 nm) and A-LO line (λ ? 492.5 nm) are conflicting with the interpretation of the P line as resulting of radiative exciton-exciton collisions. We interpret the P line as due to biexciton recombination.We have studied the luminescence in the (I2-I1) region (486nm < λ < 490nm) at low excitation. We observe clearly the following, (a) A broad band (488 nm < λ < 490.5 nm) which corresponds to the gain observed in previous experiments of pulse and probe spectroscopy and interpreted as direct recombination in an electron hole liquid (EHL). (b) After the disappearance of the EHL band, one single line (MD), which shifts continuously towards the I2 position during the time resolved kinetics. We suggest it to be connected with the high excitation effect on donor impurities (bound polyexcitons). 相似文献
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15.
A. S. Rokhmin N. V. Nikonorov A. K. Przhevuskii A. V. Chukharev A. M. Ul’yashenko 《Optics and Spectroscopy》2004,96(2):168-174
A partial polarization of luminescence in laser phosphate and silicate erbium-doped glasses was found to take place for the fundamental laser transition 4 I 13/2→4 I 15/2 (λ=1.55 μm) under excitation by linearly polarized laser radiation (532 and 790–990 nm). The shape of the luminescence spectrum depends on the wavelength of the exciting light and on the composition of the glass matrix. The degree of polarization of the luminescence depends on the spectral range of both the excitation and the detection, attaining a maximum of ~1%. The concentration dependence of the degree of polarization is studied. 相似文献
16.
《Journal of Molecular Spectroscopy》1987,124(2):443-449
A spectrum, found in the 360- to 420-nm region following hollow-cathode excitation of InCl3/In/He mixtures has been attributed to the InCl+ ion. Sixteen bands have been classified for the system which has been identified through rotational analysis to be B2Σ-X2Σ, consistent with photoelectron observations by Berkowitz and Dehmer. A second, very much weaker set of bands has been observed between 320 and 335 nm under the same experimental conditions. These latter bands constitute either a new system of InCl or a second InCl+ system. 相似文献
17.
M. S. Smirnov O. V. Ovchinnikov I. G. Grevtseva A. I. Zvyagin A. S. Perepelitsa R. A. Ganeev 《Optics and Spectroscopy》2018,124(5):681-686
The results of studying degradation of the optical properties of colloidal Ag2S and CdS quantum dots (QDs) 2.6–3.2 nm in size passivated by thioglycolic acid (TGA) are presented. The photoluminescence intensity of colloidal Ag2S QDs has been found to decrease under laser irradiation at a wavelength of 445 nm, beginning with the effective power of 10 mW. The observed effect is interpreted as a photochemical reaction of formation of new nonradiative-recombination channels in Ag2S QDs upon excitation. It is established for colloidal CdS QDs passivated by TGA that a decrease in the optical density in the entire absorption spectrum and the luminescence intensity is accompanied by precipitation of the colloidal particles in a cell and related to photodegradation of the passivating shell. 相似文献
18.
V. V. Osipov V. I. Solomonov A. V. Spirina M. G. Ivanov A. N. Orlov 《Optics and Spectroscopy》2009,106(1):78-83
Pulsed cathodoluminescence of Nd3+: Y2O3 nanopowders of the cubic and monoclinic phases and the ceramics synthesized from these nanopowders has been investigated in the spectral range 350–850 nm. It is found that the IR emission band of neodymium ions in the Nd3+: Y2O3 cubic phase is located at λ1 ≈ 825 nm. When there is a monoclinic phase admixture, two additional luminescence bands of Nd3+ arise in the spectrum at λ2 ≈ 750 nm and λ3 ≈ 720 nm. The emission spectrum of all Nd3+: Y2O3 materials also contains a wide intrinsic band of yttrium oxide at λ ≈ 485 nm; however, the presence of neodymium decreases the intensity of this band and increases the its structurization. It is suggested that the structure of this band in Nd3+: Y2O3 materials is mainly determined by local absorption (self-absorption) of neodymium ions. 相似文献
19.
Eduard Aleksanyan Vachagan Harutunyan Rein Kink Yuri Maksimov Tatiana V. Ouvarova 《Optics Communications》2010,283(1):49-53
We report on observation of upconverted VUV luminescence due to 5d-4f radiative transitions in Er3+ and Nd3+ ions doped into some fluoride crystals, under excitation by ArF and KrF excimer lasers, respectively. Only spin-forbidden 5d-4f luminescence of Er3+ (at 165 nm) was detected from the LiYF4:Er3+ crystal whereas both spin-forbidden (at 169 nm) and spin-allowed (at 160.5 nm) components are observed from the BaY2F8:Er3+ crystal, the latter being much weaker than in the case of one-photon excitation. Nd3+ 5d-4f luminescence at 180 and 173 nm has been detected from the LiYF4:Nd3+ and LaF3:Nd3+ crystals, respectively. The shift of short-wavelength edge of 5d-4f emission spectra towards longer wavelengths is observed under temperature increase from 15 to 293 K. The observed effects in the spectra of Er3+ and Nd3+ doped crystals were interpreted as a result of reabsorption of 5d-4f luminescence escaping from the bulk of the crystals. 相似文献
20.
Yu. V. Zorenko 《Optics and Spectroscopy》2006,100(4):572-580
The time-resolved luminescence and luminescence excitation spectra, and luminescence decay kinetics at 8 and 300 K of Lu3A15O12 (LuAG) single-crystal films doped with Sc3+ and La3+ isoelectronic impurities and excited by synchrotron radiation are investigated. It is established that the La3+ isoelectronic impurity in the ?ub;c?ub; positions of the garnet lattice forms La Lu 3+ luminescence centers emitting in the band with λmax = 280 nm and the decay time of the main component τ = 300 ns at 300 K. The Sc3+ isoelectronic impurity located in the ?ub;c?ub; and (a) positions of the LuAG lattice forms two luminescence centers, Sc Lu 3+ and Sc Al 3+ , emitting in the bands with λmax = 290 nm and τ = 240 ns and λmax = 335 nm and τ = 375 ns, respectively, at 300 K. It is shown that the luminescence excitation of the La3+ and Sc3+ isoelectronic impurities in LuAG single-crystal films occurs through radiative decay of excitons localized near La Lu 3+ , Sc Lu 3+ , and Sc Al 3+ centers. The energies of formation of these excitons are determined to be 6.8, 6.88, and 7.3 eV, respectively. It was found that the excited state of the excitons genetically related to the La Lu 3+ , Sc Lu 3+ , and Sc Al 3+ enters has two radiative levels with different transition probabilities. This configuration leads to the presence of fast (2.3–8.4 ns) and slow (150–375 ns) main components in the luminescence of the centers formed by isoelectronic impurities in garnets. 相似文献