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1.
Praseodymium dicarboxylate, [Pr(H 2O)] 2[O 2C(CH 2) 3CO 2] 3.4H 2O]–glutarate, Pr[glut], is synthesized by hydrothermal techniques. The title compound crystallizes in the monoclinic space group C2/c (No. 15). The rare earth cation is coordinated by nine oxygen atoms, eight oxygen atoms from the carboxylate groups and one from the water molecule. The local symmetry of Pr site is low, C s. The absorption spectra of Pr[glut] are recorded from the visible to the far IR domain at 300, 77 and 9 K. Under various Ar + laser excitations no emission is detected from 3P 0 and 1D 2 excited levels of Pr 3+ ion. In the low temperature absorption spectra only one electronic line is recorded for 3H 4→ 3P 0 transition. It confirms a unique local environment for the rare earth ion in Pr[glut]. The utility of the ‘barycenter curves’ in the attribution of electronic lines is demonstrated. Energy level scheme of 36 Stark components is deduced from the absorption spectra. The parametric calculation was performed on the whole 4f 2 (Pr 3+) configuration with the starting set of crystal field parameters obtained previously for the Eu 3+ ion in the isostructural compound. Eight free ion and nine phenomenological crystal field parameters in C 2v symmetry reproduce quite well several electronic levels of Pr 3+ ion experimentally observed in Pr[glut]. A good r.m.s. standard deviation of 14.8 cm −1 is obtained. 相似文献
2.
The absorption and emission spectroscopies of RE 3+ ions embedded in a new phase, LaGa 3O 6, owing to the La 2O 3–Ga 2O 3 binary system (RE=Pr, Nd, Eu) are discussed. The 2S+1L J level degeneracies are completely lifted in accordance with the low point symmetry of the site occupied by the rare earth ion in LaGa 3O 6. The energy level schemes deduced from the data are reproduced by considering a crystal field (CF) effective Hamiltonian involving the nine real and five imaginary parameters required for the C 2 or C s symmetry of the rare earth site. The rms deviation is satisfactory for the three simulations. However, the strong variation of the CF parameters between Pr 3+ and Eu 3+ in LaGa 3O 6 suggests the possible limit of existence of the phase, intimately correlated to small variations of the rare earth ionic radius. 相似文献
3.
The high resolution absorption, luminescence and excitation spectra of the orthorhombic potassium lanthanum praseodymium ternary chloride, K 2La 1−xPr xCl 5, (0.02 ≤ x ≤ 0.15) single crystals were recorded at 4, 77 and 293 K with different excitation sources. The experimental 4f 2 energy level scheme of the Pr 3+ ion in K 2LaCl 5 derived from the absorption and emission spectra consisted of 86 (out of 91) Stark components. This energy level scheme was simulated by using a phenomenological crystal field (cf) model which included eight free ion and nine cf parameters according to the C 2v symmetry. Despite the approximate C 2v point symmetry instead of the real C s one, the simulation yielded a very satisfactory rms deviation of 17 cm −1 between the experimental and calculated energy level schemes. The results, especially the weak cf strength, are discussed taking into account the bonding characteristics in K 2LaCl 5. 相似文献
4.
The results of the high-resolution absorption, selective excitation, time-resolved emission and emission kinetics of Eu 3+ in GdCOB and EuCOB single crystals are presented. The Eu 3+ spectra show at least three non-equivalent centers whose static spectral characteristics were used to assign structural models. The crystal field parameters were estimated for prevailing Eu 3+ center in EuCOB. The inhomogeneous broadening and shifts of the 5D 0→ 7F 0 and 5D 0→ 7F 1 Eu 3+ lines in GdCOB under selective excitation in main lines were explained by J mixing of 7F 2 states into 7F 1 and 7F 0 by second order crystal field terms and connected to disordered structure in cationic spheres. 相似文献
5.
The formation of cation solid solution in the (La 1−xGd x)OCl:Eu 3+ (0≤ xGd≤1; ΔxGd=0.1) series was studied by photoluminescence spectroscopy. The luminescence from the 5D 0–2 to the 7F 0–4 levels of the Eu 3+ ion in the (La 1−xGd x)OCl series was recorded at 77 K by using argon ion laser excitation (457.9 nm). The interpretation of the spectra according to the C 4v site symmetry of the Eu 3+ ion in the tetragonal PbFCl-type structure yielded nearly complete sets (18 to 19 levels) for the 7F 0–4 levels. Simulations of the Stark level schemes were carried out with the aid of a phenomenological c.f. theory utilizing the five non-zero c.f. Bqk parameters ( B02, B04, B44, B06 and B46) allowed for the C 4v site symmetry. By using the calculated c.f. parameter sets a quantitative measure was obtained to monitor the formation of cation solid solutions. The strength of the c.f. effect was estimated with the c.f. strength parameters S and Sk ( k=2, 4 and 6). The c.f. parameter sets reproduced the experimental 7F J ( J=0–4) energy level schemes with the rms deviations between 4 and 11 cm −1. The individual parameters as well as the c.f. strength parameters were found to evolve in a smooth manner indicating complete solid solubility in the (La 1−xGd x)OCl series. Some local distortions from the C 4v symmetry — probably of long range—leading to the splitting of the 7F 1 doubly degenerate E level were observed, however. 相似文献
6.
Optical and magnetic measurements are performed on Nd 3+ doped into LiYO 2. 105 energy levels of Nd 3+ are assigned from the optical absorption and excitation spectra for the powdered sample at 20 K. The crystal field analysis is performed in the C1 site symmetry of Nd 3+. Theoretical values of the crystal field parameters, oscillator strengths, magnetic susceptibility and ground state splitting factors are calculated and compared with experimentally measured quantities. 相似文献
7.
A valence change from Eu 3+ to Eu 2+ was observed in the europium ion-doped ZnO–B 2O 3–P 2O 5 glasses prepared at high temperature in air. The fluorescence emission spectrum of the sample consists of a broad emission band ascribed to the 5d–4f transition of Eu 2+ ion and sharp emission peaks assigned to the transitions of 5D o– 7F J ( J = 0, 1, 2, 3, and 4) of Eu 3+ ion, indicating that part of Eu 3+ can be reduced into Eu 2+ in the glass. A charge compensation model is proposed. The rigid tetrahedral network structure of glasses plays an important role in stability of Eu 2+. The fabrication conditions are also studied. 相似文献
8.
The paper reports on the course of decomposition of hydrated lutetium nitrate and lutetium chloride to Lu 2O 3 in the eutectic mixture of NaNO 2 and KNO 2. It was shown that a crystallographically pure phase of the cubic Lu 2O 3 is formed at temperature as low as 250 °C. IR spectra revealed that the recovered powder contains some OH-contamination, however. The powders are characterized by crystallites sizes in the range of 18–30 nm in average. Emission and excitation spectra of Eu-doped powders show characteristic features for Eu 3+ ion in an oxide host, which indicates that the procedure is appropriate for making activated nanoparticulate oxide phosphors. Most profound emission appears around 611 nm and the luminescence from the powder made starting with Lu(NO 3) 3 was noticeably higher compared to the product obtained from LuCl 3. The excitation spectrum of Eu 3+ emission at 611 nm contains a band related to the fundamental absorption of the lutetia host lattice, which indicates an existence of the host-to-activator energy transfer. 相似文献
9.
Nano-sized SrAl2O4:Eu^2+,Dy^3+ phosphors with good monodispersity and narrow size distribution were synthesized by the coupling of water-in-oil (W/O) microemulsion with coprecipitation method. The phase composition, morphology, crystallinity, excitation spectra, emission spectra, and afterglow decay of SrAl2O4:Eu^2+,Dy^3+ nanophosphors were measured. It was found that the amount of surfactant that was used had an important effect on the shape and average size of the phosphor particles. SrAl204 phase of the phosphors showed an increase with the increase in calcination temperature. When the calcination temperature reached 1150℃, the fine crystal of SrAl2O4 was formed and the long afterglow luminescence could be obviously observed. In comparison with the samples prepared by the high-temperature solid-state method, the calcination temperature showed an obvious decrease and a dear blue shift occurred in the excitation and emission spectra of the sample. The afterglow time could be more than 8 h. 相似文献
10.
Nanosized Gd 1.92−x−yZn xLi yEu 0.08O 3−δ phosphor was fabricated by combustion synthesis. The effect of Zn 2+ and Li + ions on the crystallization behavior, morphology, and luminescence property of Gd 2O 3:Eu 3+ was investigated. The results indicated that incorporation of Zn 2+ and Li + ions into Gd 2O 3:Eu 3+ nanoparticles (NPs) could lead to a remarkable increase of photoluminescence or X-ray excited luminescence, and the intensity at 612 nm was increased by a factor of 7.1 or 21.5 in comparison with that of undoped sample. The enhanced luminescence was regarded as the results of the creation of oxygen vacancies due to the Gd 3+ sites occupied by Li + ions, the alteration of the crystal field surrounding the activator Eu 3+ ions owing to the incorporation Zn 2+ ions into interstitial sites, and the flux effect of Zn 2+ and Li + ions. The Zn- and Li-codoped Gd 2O 3:Eu 3+ phosphor with highly enhanced luminescence is very encouraging for applications in high-resolution display devices. 相似文献
11.
Absorption and fluorescence measurements have been performed on pure Eu 2Te 4O 11 tellurium oxide and on Eu 3+-doped Gd 2Te 4O 11 samples. The spectra were recorded at liquid helium, liquid nitrogen and room temperatures. In this monoclinic host matrix, the rare earth occupies a single crystallographic point site, with the very low symmetry C1. The energy level scheme is derived, from the experimental data, for the 7F j (J= 0,1,2,3,4) ground multiplet of the 4f 6 configuration of Eu 3+. Despite the low symmetry for the rare earth, parametrization of the crystal field effects was carried out with very good r.m.s. standard deviations and residues. 相似文献
12.
Luminescence properties of KNbW 2O 9 crystal doped with Eu 3+, investigated at room and liquid nitrogen temperatures, showed that the active ions occupy two crystallographically different sites. The structural and IR spectra investigations were also carried for better understanding of Eu 3+ ion behavior. The luminescence decay profiles were slightly non-exponential. The luminescence lifetimes of Eu 3+ were approximated by biexponential decays. Both were ascribed to two different Eu(III) sites. The longer component was determined to be ca. 1 ms, whereas the shorter one was about 0.5 ms. It was found that the Eu sites characterized by longer decay times were not affected by temperature, whereas the sites characterized by shorter decay times revealed strong decrease of decay times with temperature. Infrared investigation demonstrated the presence of water molecules occupying hexagonal tunnels in the KNbW 2O 9 crystal. The UV irradiated crystal showed the presence of blue coloration. The observed color was attributed to small W 5+ polarons or intervalence charge transfer between W 5+ and W 6+ states. The electrons, necessary for the formation of the W 5+ states, originate most likely from UV photodissociation of water molecules. 相似文献
13.
The absorption spectrum of (η 8-COT)Nd[HB(3,5-Me 2pz) 3] (COT=cyclooctatetraenyl, pz=pyrazol-1-yl) has been measured at room temperature, at approximately 90 K and in parts at ca. 30 K. The bands were assigned by applying the selection rules for C 8v symmetry and by performing crystal field (CF) calculations assuming the CF parameters of the Nd complex were the same as for the previously analyzed (COT)Pr[HB(3,5-Me 2pz) 3]. The parameters of an empirical Hamiltonian were fitted to the energies of 27 levels to give an r.m.s. deviation of 25.5 cm −1. Neglecting the influence of [HB(3,5-Me 2pz) 3] ligand, the CF strength of the [COT] −− ligand could be estimated from the CF parameters obtained. 相似文献
14.
The polarized absorption and emission spectra have been measured for the Tm 3+ doped NaY(MoO 4) 2 crystal and spectral parameters have been estimated from the absorption data based on the Judd–Ofelt theory. The effective intensity parameters ( t = 2, 4, 6) are 11.67 ×10 −20, 2.21 × 10 −20, 1.74 × 10 −20 cm 2, respectively. From the intensity parameters, the radiative transition probabilities, radiative lifetimes, branching ratios and the emission cross-section have been calculated. In comparison with other Tm 3+ doped laser crystals, Tm 3+:NaY(MoO 4) 2 crystal has potential as a promising laser crystal. 相似文献
15.
Optical absorption and magnetic circular dichroism (MCD) spectra of 1% Pr 3+ doped ZBLAN fluorozirconate glass have been recorded at several temperatures between 4.2 K and room-temperature. The dipole strengths of the 4f–4f transitions are parametrized in terms of three phenomenological Judd–Ofelt intensity parameters Ωλ ( λ=2, 4 and 6). The method of moments was used to extract the Faraday parameters from the MCD spectra. While the room-temperature MCD spectra are dominated by A-terms (which have the shape of the first derivative of an absorption curve), C-terms become more important at lower temperature. The temperature dependence of the 3P 0← 3H 4 transition is a typical example. The temperature dependent change of the MCD spectrum can be explained by the differential thermal population of the Zeeman levels from which absorption of left and right circularly polarized light takes place. 相似文献
16.
Luminescence investigations of nanocrystalline (nc) BaTiO 3 powders doped with Eu 3+-ions prepared by the sol–gel method is described. A stability of Eu 3+-ions replacing Ba 2+-sites up to 1100 °C is reported. The effect of BaTiO 3 grain sizes on luminescence properties of Eu 3+ was noticed. To explain these differences a detailed analysis of luminescence spectra by the Judd–Ofelt theory has been performed. 相似文献
17.
Laser excited luminescence and site selective excitation spectra of trivalent terbium (Tb 3+) in two rare earth oxyfluoride (ROF) matrices, LaOF and GdOF, were detected at temperatures down to liquid helium. From the analyses of spectra, the crystal field (c.f.) fine structure of the 7F J ( J=0–6) ground multiplet was obtained for the 4f 8 electron configuration. The energy level schemes comprising 26 c.f. sublevels out of 33 allowed for the C 3v point symmetry of the R 3+ site were simulated according to a phenomenological model taking into account only the c.f. effect. The simulation including six c.f. parameters (B02, B04, B34, B06, B36, and B66) reproduced the experimental energy level schemes in a satisfactory manner with rms deviations of 5 and 6 cm−1 for the LaOF and GdOF hosts, respectively. The c.f. parameter sets are characterized by B02 values close to zero while the fourth and sixth rank parameters assumed rather high values. The Oh to C3v descending symmetry method revealed a slight trigonal distortion from the cubic fluorite CaF2-type structure. The c.f. parameters vary only slightly as a function of the host matrix. The 7F6 level was not simulated correctly probably because of the electron–phonon interaction. 相似文献
18.
Chemiluminescence (CL) of the systems containing Eu 2+ or HCO 3− ions and hydrogen peroxide was studied. The kinetic curves and CL emission spectra of the systems were discussed. The emission spectrum of the system containing carbonates revealed two emission maxima: the first directly after initiation of the reaction by hydrogen peroxide and the second in several seconds after the first. On the basis of the characteristic bands in the CL spectrum the emitters in the system Eu 2+/HCO 3−/H 2O 2 were identified as: excited Eu 3+ ions and excited products of carbonate decomposition. The emission bands for λ=600 and 420 nm appeared in a time distance of a few ten seconds. 相似文献
19.
A single-crystal X-ray structural investigation of [Tb(C 5H 5) 2Br] 2 revealed the [Sc(C 5H 5) 2Cl] 2-type structure, space group P2 1/ c, with a = 1407.6(2) pm, b = 1644.7(2) pm, c = 1370.6(9) pm, β = 93.46(3)°, V = 3167(2) × 10 6 pm 3, Dc = 2.322 g cm −3 and Z = 6 dimers ( R = 0.036 for 4627 reflections with I > 3σ( I)). The metal centres have the pseudosymmetry C2v. Magnetic susceptibility data show Curie-Weiss behaviour between 213 and 6 K with θ p = −4.5(3) K and a magnetic moment μ = 9.8(1) μ B close to the Tb 3+ free-ion value (9.72 μ B). Below 6 K, deviations from Curie-Weiss behaviour are observed, and at 5.3 K a maximum in the susceptibility is detected which may be caused by intradimer antiferromagnetic spin coupling. The magnetic properties are compared with the prediction of various models, starting from cubic crystal fields and isotropic intramolecular exchange interactions, followed by extension to lower crystal field symmetry (orthorhombic) and anisotropic contributions to the spin coupling. However, a reasonable agreement between the measured and calculated data was not obtained. As in [Gd(C 5H 5) 2Br] 2, the low-temperature behaviour is governed by effects which cannot be described by spin coupling models in the generally accepted form. 相似文献
20.
Energy transfer phenomena have been observed by activating the oxyapatite host-lattice Ca 2Gd 8(SiO 4) 6O 2 with Eu 3+, Tb 3+, Dy 3+, Sm 3+. This is based on the energy migration in the Gd 3+ sublattice and trapping by the activators. The trapping efficiency for Gd 3+ excitation energy increases in the sequence of Sm 3+ < Dy 3+ < Tb 3+ < Eu 3+. It is supposed that the activator ions are incorporated on both Gd 3+ sites in Ca 2Gd 8(SiO 4) 6O 2. The Gd 3+ sublattice in Ca 2Gd 8(SiO 4) 6O 2 can be sensitized by Pb 2+ but not by Ce 3+, Pr 3+ and Bi 3+. 相似文献
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