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1.
In Y2SiO5:Pr3+ nanocrystals, an ordered phase is observed in the 1 D 2 luminescence decay curves of Pr3+ ions at their anomalously low concentration (0.5 at %). This effect is caused by the predominant accumulation of activator ions near the nanocrystal surface, which provides relaxation of the elastic strains arising as a result of the misfit between the ionic radii of Pr3+ and Y3+. The concentration quenching of Pr3+ luminescence is due to cooperative cross relaxation.  相似文献   

2.
The results of an experimental investigation of low-temperature optical spectra and phase relaxation of electronic excitations of Pr3+ impurity ions in a Y2SiO5 crystal are reported. It is established that at low temperatures spectral lines are broadened by a mechanism that is uncharacteristic for crystals and is due to the interaction of impurity ions with two-level systems. The constants characterizing the interaction of Pr3+ impurity ions with phonons and two-level systems are found. Zh. éksp. Teor. Fiz. 115, 704–715 (February 1999)  相似文献   

3.
A complex study of the energy spectra and relaxation channels for the excitation energy of activation centers in Y2SiO5:Pr3+, Lu2SiO5:Pr3+, and Gd2SiO5:Pr3+ was performed. An analysis of the low-temperature optical spectra showed that the energy parameters and the character of field splitting of the 1 D 2 and 3 H 4 activator ion terms were substantially different in crystals of different crystallographic types. The pseudosymmetry effect was observed in splitting of the 1 D 2 and 3 H 4 terms of Pr3+ ions situated in nonequivalent crystal lattice cation sites of Y2SiO5 and Lu2SiO5. Activator ions nonuniformly populated nonequivalent cation sites of the Y2SiO5 crystal lattice. At high activator ion concentrations (>1 at %), luminescence decay in Y2SiO5 could not be described by a simple exponential time dependence. The complex luminescence decay law was caused by activator ion excitation energy migration and capture by acceptors. The role of energy acceptors was played by activator ion dimers.  相似文献   

4.
For the fist time in Y2SiO5:Pr3+ nanocrystals, the ordered stage in the 1 D 2 luminescence decay curves for Pr3+ ions has been observed at anomalously low doped ion concentration (0.5 at %). This effect is caused by preferred location of the activator ions in the near-surface layer of the nanocrystal that provides the relaxation of elastic tension arising due to the difference of ionic radii of Pr3+ and Y3+ ions. Concentration quenching of Pr3+ luminescence is caused by the cooperative cross-relaxation.  相似文献   

5.
Photoluminescence spectra of CaWO4 doped with Pr3+ and Tb3+ obtained at high hydrostatic pressures up to 315 kbar applied in a diamond anvil cell (DAC) are presented. The intensities of the luminescence from the 3P0 state of Pr3+ and from the 5D3 state of Tb3+ decreased with increasing pressure. At pressures greater than 50 kbar, the 1D2 → 3HJ transitions in Pr3+ and the 5D4 → 7FJ transitions in Tb3+ dominated the spectra. At pressures greater than 100 kbar, only emissions from the lower excited states were observed. At pressures greater than 150 kbar, luminescence from the 1D2 and 5D4 states also decreased with increasing pressure, and at a pressure of 315 kbar for CaWO4:Pr3+ and 190 kbar for CaWO4:Tb3+, the emissions related to the Pr3+ and Tb3+ were quenched. These effects were related to the influence of impurity trapped excitons (ITEs) on the efficiency of the f–f emission in the Pr3+ and Tb3+ ions. Analysis of the emission spectra collected at different pressures allowed the energies of the ground states of the Pr3+ and Tb3+ ions with respect to the band edges of the CaWO4 host to be estimated.  相似文献   

6.
Strong temperature controlled segregation of doped ions in Y2SiO5:Pr3+ nanocrystals detected by spectroscopic techniques is reported. The elastic interactions stimulate Pr3+ segregation thus leading to non-uniform distribution of doped ions, pair formation and, as a consequence, to abnormal low threshold of luminescence concentration quenching for Y2SiO5:Pr3+ nanocrystals.  相似文献   

7.
《Journal of luminescence》1986,36(3):161-172
Use of site selection spectroscopic techniques combined with low temperature absorption spectral studies has enabled the identification and characterization of ten optically important charge-compensated crystallographic sites for Pr3+ in the β-ThCl4:Pr3+ system. Fluorescence decay time measurements, variation of site distribution with dopant concentration and fluorescence spectra were used to characterize the sites. Distant charge compensation is found to be one of the dominant modes of charge compensation of Pr3+ in ThCl4, and its predominance over other sites increases as Pr3+ concentration decreases. The sinusoidal distortion of the crystal field symmetry around Pr3+ in the incommensurate phase of β-ThCl4 is believed to be mainly responsible for the splitting and continuous shift in fluorescence spectral lines which occur when 3P03F2 fluorescence scans are made with excitation at different points on the 3P03H4 absorption line belonging to different sites.  相似文献   

8.
Photoluminescence and time resolved photoluminescence spectra of Ca(NbO3)2 doped with Pr3+, excited under 37,000 cm?1 (270 nm), obtained at high hydrostatic pressure up to 20 kbar applied in a sapphire anvil cells, are presented. At ambient conditions, the emission spectrum obtained in the time interval 0–1 μs is dominated by spin allowed transitions from the 3P0 state. The luminescence related to transitions from 1D2, characterized by a decay time equal to 33 μs, is observed when one excites directly the Pr3+ ion with 30,770 cm?1 (325 nm) wavelength. The introduction of Pr3+ impurities in Ca(NbO3)2 does not quench the self-trapped exciton (STE) luminescence. This luminescence, peaking at 20,000 cm?1 (500 nm), having a decay time of 61 ± 1 μs, still occurs when the crystal is excited with a wavelength of 37,000 cm?1 (270 nm) or shorter. Under such excitation a fraction of the STE luminescence is reabsorbed by Pr3+ ions; in this case the emission lifetime of the 1D23H4 transition of Pr3+ is 64 ± 3 μs. This effect is stable also at high pressure.  相似文献   

9.
The variation of photon echo intensity in LaF3 : Pr3+ measured as a function of pulse separation for short times is shown to be a consequence of echo modulation as caused by isolated non-interacting Pr3+ ions.  相似文献   

10.
The polarized absorption and emission spectra of Pr3+ ions in NaY(MoO4)2 single crystal were investigated. The standard and modified Judd–Ofelt theory have been applied to the measured optical absorption intensities to determine the spectroscopic parameters, including the Judd–Oflet intensity parameters Ωt (t=2,4,6), the radiative transition rates, branching ratios, and emission cross-sections for various excited levels of Pr3+ ions. In samples with Pr3+ ions concentration of 2.00×1020 cm-3, the excitation of the 1 D 2 manifold decays non-radiatively by the electric dipole–dipole transfer between Pr3+ neighbors. The good spectroscopic properties show the possible application of the Pr3+ doped NaY(MoO4)2 crystal as a solid-state laser. PACS 42.70.Hj; 78.20.-e  相似文献   

11.
The direct comparison of the luminescence decay data obtained for nano- and bulk Y2SiO5:Pr3+ crystals has revealed that the concentration threshold of luminescence quenching is strikingly low for nanocrystals. Nanocrystal inhomogeneous stress field induced by a surface stimulates the segregation of the doped Pr3+ ions within the surface layer that provides the relaxation of elastic tension arising due to the difference of the ionic radii of Pr3+ and Y3+. The Pr3+ irregular distribution in the nanocrystal volume results in the Pr3+ local concentration increasing that facilitates the luminescence quenching.  相似文献   

12.
The optical absorption, emission, and excitation spectra of Pr3+ and Er3+ ions in LiYF4 have been measured and energy level schemes established which agree with previous work. The temperature dependence of the emission lifetimes were investigated and analyzed using the Huang-Rhys and Struck-Fonger treatments of multiphonon decay. The non-radiative processes in LiYF4: Er3+ were shown to follow the same “gap law” behavior as Er3+ in LaF3 and MnF2. Theoretical fits to the Huang-Rhys model allowed the construction of a configuration coordinate diagram for the Er3+ system. The non-exponential temperature dependence of the 1D2 lifetime in Pr3+ can be understood as a non-radiative transition from higher levels.  相似文献   

13.
Single crystals of SrLaAlO4: Pr3+ and SrLaAlO4: Nd3+ have been grown by the Czochralski method and their optical properties have been studied for different activator concentrations. The absorption and emission spectra of the activators are inhomogeneously broadened because the Sr2+ and La3+ ions are distributed randomly on the sites ofC 4 symmetry, however, the symmetry selection rules are still obeyed. Strong self-quenching of the praseodymium luminescence occurs by cross relaxation which is supposed to be assisted by phonon emission in the case of the3 P 0 level. Self-quenching of Nd3+ luminescence disappears at low temperature indicating that the condition of resonance in the cross-relaxation process is fulfilled only for higher components of the ground state.Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw, Poland  相似文献   

14.
A Bi2(MoO4)3 single crystal doped with Pr3+ ions has been grown by the Czochralski technique. The polarized absorption and fluorescence spectra as well as the fluorescence decay curve of Pr3+ ions in the crystal were measured at room temperature. The spectroscopic parameters, including the Judd–Ofelt intensity parameters Ωt (t=2, 4, and 6), spontaneous emission probabilities, fluorescence branching ratios, radiative lifetimes, stimulated emission cross sections, and fluorescence quantum efficiencies, were calculated. The spectral properties related to laser performance of this crystal were analyzed. The 1 D 2 multiplet of the crystal may be a good upper level for a solid-state laser.  相似文献   

15.
We show the possibility of obtaining UV luminescence from 5d-4f transitions of rare-earth ions in the BaY2F8: (Yb3+, Pr3+, Ce3+) crystal under upconversion excitation by standard laser diodes with lasing wavelengths of 960, 808, and 840 nm. Various upconversion mechanisms of pumping for populating the higher-lying energy levels of the active ions, as well as methods of adaptation of the active medium BaY2F8: (Yb3+, Pr3+, Ce3+) to these mechanisms, are considered.  相似文献   

16.
In this paper we present and discuss results of detailed spectroscopy studies of Pr3+ luminescence from the (Ba,La)F2:0.2 m%Pr crystals under UV and VUV synchrotron excitation.We have measured time resolved emissions from the minor site Pr3+ in (Ba,La)F2:Pr at 10 and 300 K. The spectra clearly show the 1S0 emission from the Pr3+ ions in some low symmetry Pr-sites (we designate them La-sites) previously identified in higher concentration (0.3 m%Pr and more) crystals. However most of emission from the Pr activated (Ba,La)F2 crystals originates in Pr3+ ions in other sites which produce an efficient d-f emission. As demonstrated by excitation spectra, the emission from some of these sites (denoted as Ba-sites) closely resembles the d-f emission from BaF2.The La-site, time resolved and long delay emission spectra are dominated by hypersensitive transitions from the 1S0 and 3P0 levels to lower energy levels of the 4f2 configurations. Only these transitions contribute to the photon cascade emission desired for some mercury free phosphor applications.  相似文献   

17.
Abstract

The luminescence spectrum of Cs2NaScCl6:Pr3+ (0.1 at.%) has been recorded at temperatures down to 10 K and assigned between 20,800 and 9900 cm?1. Twenty‐three energy levels of the 4f2 configuration Pr3+ ion were located and then fitted by the conventional 4f2 crystal field calculation, as well as by a configuration interaction assisted crystal field (CIACF) calculation. The latter gave a much better fit. A comparison of the fit for Cs2NaScCl6:Pr3+ with fits upon the same set of energy levels in Cs2NaYCl6:Pr3+ and Cs2NaPrCl6, where the fifth nearest neighbor of Pr3+ is changed and the lattice parameter increases along this series, shows a decrease in the magnitudes of the crystal field parameters, which were also semiquantitatively simulated. Several facets of the emission spectra are interesting, including the observation of weak progressions in the totally symmetric Pr–Cl stretching vibration and the occurrences of the resonance of electronic and vibronic states. The spectra of Cs2NaScCl6:Pr3+ (1 at.%) differ considerably from those of the more dilute system and show that other species are formed rather than a complete substitution of the Sc3+ sites by Pr3+.  相似文献   

18.
The paper reports on a study of luminescence and excitation spectra of SrAlF5:Pr3+ (0.5 mol %) polycrystals performed at 10 and 300 K with synchrotron radiation in the range from 5 to 25 eV. The Pr3+ ions in SrAlF5 were shown to emit successively two photons in transitions from the 1 S 0 and 3 P 0 levels. The main energy characteristics of the compound, namely, the position of the 4f → 5d excitation band (5.95–8.0 eV), the energy separation between the 1 S 0, 4f and the lowest 5d levels (~0.15 eV), and the SrAlF5 band gap width (~12 eV), were determined. SrAlF5:Pr3+ was found to possess a number of features not found in other Pr3+-activated fluorides.  相似文献   

19.
The possibilities of occupying high-lying 4f states of Pr3+ ions in the active BaY2F8:Yb3+,Pr3+ medium according to the photon avalanche and step-by-step sensitization mechanisms are compared. It is shown that the photon avalanche is unlikely to occur in the BaY2F8:Yb3+,Pr3+ crystal. The multiband luminescence spectra in the visible spectral range (white emission) under single- and multiwave pumping of BaY2F8:Yb3+,Pr3+ crystal by IR laser diodes are reported.  相似文献   

20.
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