[en] Halides belong to large band gap matrices that have the perspective of wide applications when doped by optical active ions. This paper presents the results of spectroscopic studies of single crystals of halides (Cl, Br) of Ce, Pr and Nd. Their spectroscopic behaviour: electron-phonon coupling, ion pair interactions and the effect of covalency, is compared. Absorption, emission and emission excitation spectra of single crystals of LnCl₃·yH₂O (Ln = Nd, Pr, Ce; y=6, 7) were recorded at room temperatures and low temperatures down to 4.2 K. The intensities of the electronic lines and the Judd-Ofelt parameters were calculated (Nd, Pr) and compared to those of LnBr₃·yH₂O presented earlier by us. The relationship between the hypersensitivity and covalency was discussed. With increasing soft character of the halides (Br^- > Cl^-), the covalent character of Ln-ligand bond increases and the hypersensitive bands become more intense. The Judd-Ofelt intensity analysis resulted in a set of τ_λ parameters evaluated with quite low standard deviations. The temperature dependences of the intensities have been found and the vibronic coupling in the f-f transitions were analysed. At the low temperature (4.2 K), strong vibronic components occur in the electronic lines of the Nd(III) and Pr(III) ions, mainly with the Ln-X vibrations. The modes, which are in resonance with the splitting of the ground state multiplet, mediate in the cooperative transitions. Vibrational studies of the compounds under test were performed at the ambient temperature using IR and Raman spectroscopy. The assignment of the bands was done on the basis of the factor group analysis. The spectral features below 300 cm^-1 point at the differences between the spectra of the bromides and chlorides of Nd and Pr. Although the spectral features within the FIR region are complex, the bands of the praseodymium monocrystals originated by halogen bridges are clearly visible

[en] Among a wide variety of solid state materials, alkali lanthanide double phosphates are the subject of extensive spectroscopic investigations for their application as laser active materials. The edge of absorption in this compound is at rather high energies, which makes them suitable as efficient host for luminescent materials. Spectroscopic properties of Sm³⁺-doped K₃Y(PO₄)₂ are reported basing on the high resolution absorption and emission spectra for various temperatures mainly at 4, 10, and 293 K from UV to IR range. The effects of concentration and temperature on intensities and shape of the observed bands were studied. Radiative transition probabilities were calculated from absorption spectra and Judd–Ofelt parameters evaluated. The excited state dynamics will be discussed based on the decay time measurement. - Highlights: • Sm³⁺: K₃Y(PO₄)₂ crystals were synthesized via a solid-state reaction. • The spectroscopic properties of the samples were investigated at 293 and 11 K. • Concentration quenching mechanisms and possible relaxation channels were discussed. • The Judd–Ofelt intensity parameters are calculated. • Sm³⁺: K₃Y(PO₄)₂ is a promising material for 405 nm pumped phosphor.

[en] The high resolution absorption, luminescence and excitation spectra of the orthorhombic potassium lanthanum praseodymium ternary chloride, K₂La_1-xPr_xCl₅, (0.02 ≤ x ≤ 0.15) single crystals were recorded at 4, 77 and 293 K with different excitation sources. The experimental 4f² energy level scheme of the Pr³⁺ ion in K₂LaCl₅ 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 K₂LaCl₅

[en] The UV excited and persistent luminescence properties as well as thermoluminescence (TL) of Eu²⁺ doped strontium aluminates, SrAl₂O₄:Eu²⁺ were studied at different temperatures. Two luminescence bands peaking at 445 and 520 nm were observed at 20 K but only the latter at 295 K. Both Sr-sites in the lattice are thus occupied by Eu²⁺ but at room temperature efficient energy transfer occurs between the two sites. The UV excited and persistent luminescence spectra were similar at 295 K but the excitation spectra were different. Thus the luminescent centre is the same in both phenomena but excitation processes are different. Two TL peaks were observed between 50 and 250 deg. C in the glow curve. Multiple traps were, however, observed by preheating and initial rise methods. With longer delay times only the high temperature TL peak was observed. The persistent luminescence is mainly due to slow fading of the low temperature TL peak but the step-wise feeding process from high temperature traps is also probable

[en] Spectroscopic properties of Ln(III) complexes with 4-amino-6-methylpicolinic acid N-oxide (ampicN-O) were characterized using absorption, fluorescence and phosphorescence spectra of the ligand as well as Eu(III) luminescence (intensity, lifetime measurements and selective excitation spectra in the range of ⁵D₀ <- ⁷F₀ transition) at 77 and 293 K. Based on emission behavior of ampicN-O and its Eu(III) and Gd(III) complexes the energy level of the ligand triplet state, mechanism of the ligand to metal energy transfer has been proposed and a role of the C-T state in this process analyzed. Detailed studies of the Eu(III) selective excitation spectra in the range of ⁵D₀ <- ⁷F₀ transition recorded for Eu/ampicN-O aqueous solution indicated equilibrium of three complex forms: ML, ML₂, ML₃

[en] Yttrium aluminum garnet, Y₃Al₅O₁₂ (YAG), doped with Eu (0-4%) was synthesized reacting appropriate metal nitrates in NaNO₂-KNO₂ eutectic mixture. Pure cubic garnet phase was formed upon heating for a few hours at temperature as low as 470 ^oC. The particle sizes of the powders were mostly in the range of 200-300 nm, but a small fraction of material crystallized in particles of about 20-40 nm. Selected area electron diffraction patterns proved that the larger particles are monocrystalline. Excitation and emission spectra of the Eu-doped powders are characteristic for Eu³⁺ in an oxide host. The most intense luminescence lines are located around 590 nm

[en] A series of potassium lanthanum praseodymium ternary bromides, K₂La_1-xPr_xBr₅ (0.02 ≤ x ≤ 1) single crystals was grown by the Bridgman technique. The high resolution absorption, luminescence and excitation spectra were measured at 4, 77 and 293 K under different excitation sources, including VUV synchrotron radiation. The Stark components determined from the absorption and emission spectra were simulated by using a phenomenological crystal-field model for 4f² configuration of the Pr³⁺ ion in K₂PrBr₅. The comparison is made with earlier reported data for Pr³⁺ in K₂PrCl₅ crystal. The decay times of the emission from the ¹D₂ and ³P₀ levels were measured and excited states dynamic is analysed

[en] Two types of new Ln³⁺ chelates, phosphoro- and sulfono-derivatives of beta-diketones and Lewis base ligands were obtained and characterized by the high resolution photoluminescence spectroscopy at 293 and 77 as well as by luminescence decay times. The new type of phosphors shows very strong emission after excitation in the UV range within the ligand bands. The dynamics of the excited state will be discussed. The paths of the energy transfer (ET) are analyzed and mechanism of this process is proposed. The silica gels containing investigated complexes with silver particles were obtained and the role of silver plasmons on spectroscopic properties is displayed. - Highlights: • Spectral characteristic of new type of lanthanide chelates: Na[Ln(SP)₄] and [Ln(SP)₃L]. • Preparation of the energy-transfer (E-T) diagram. • Analysis of the possible pathways of energy transfer and their mechanism. • Application of chelates incorporated in sol–gel codoped by Ag particles.

[en] Highly resolved luminescence and luminescence excitation spectra of recently synthesized LnL₃bpy complexes, where Ln=Eu³⁺, Tb³⁺, bpy=2,2'- bipyridyne and L=phosphoroazo derivative of β-diketone: CCl₃C(O)NP(O)(OCH₃)₂, in solid state and dissolved in nematic liquid crystal 6CHBT [4-(isothiocyanatophenyl)-1-(trans-4-hexyl)cyclohexane] were measured. The photoluminescence intensity of the complexes dissolved in 6CHBT was found to exhibit a strong dependence on the electric field. The mechanism of the effect and reason of its asymmetry with respect to the sign of electric field are discussed in the paper. Luminescence decay time in various environments and experimental quantum yields of the luminescence of these compounds in CDCl₃ and CHCl₃ solutions were measured

[en] New combustion technology of synthesis of nanosize phosphors have been described. Four series of nanocrystalline Lu₂O₃:Eu³⁺ have been prepared for different composition of fuel (glutamic acid:glycine)using the combustion method. The concentration of Eu(III) varied from 0.05 to 15wt% and the size of the nanoparticles covered the range 6-10nm. The size effect on optical properties of the phosphors have been investigated and correlated with the decay profiles of the Eu(III) emission. It has been proved that composition of the fuel influences the size of nanocrystallines, and in consequence their optical properties