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The Stark structure of multiplets and the oscillator strengths of absorption transitions in Pr3+ ions in a Y3Al5O12 crystal have been described with allowance for the effect of the excited opposite-parity configuration and the charge-transfer configuration. To take into account this effect, a modified crystal-field Hamiltonian and an effective line-strength operator for intermultiplet electric-dipole transitions are proposed. Their use in description of experimental data makes it possible to decrease the standard deviation by 37 and 20%, respectively, in comparison with the standard theories. The even-and odd-crystal-field parameters and the covalence parameters have been obtained from the description of Stark levels. The intensity parameters calculated on the basis of the covalence parameters and odd-crystal-field parameters are in satisfactory agreement with the parameters obtained from the description of the experimental oscillator strengths. [ABSTRACT FROM AUTHOR]

The dependence of the structural reorganization of Eu3+ optical centers in Al2O3-Eu2O3-BiOF films on the annealing temperature has been investigated. It is shown by the methods of crystal field theory and computer simulation that the increase in the annealing temperature from 700 to 1100 °C leads to removal of bismuth from Eu-O-Bi complex centers with the C 3 V symmetry in the Al2O3 structure and the change in symmetry from D 3 to O h for a large fraction of EuAlO3 centers. [ABSTRACT FROM AUTHOR]

The Stark structure of multiplets and the oscillator strengths of absorption transitions in Pr3+ ions in a Y3Al5O12 crystal have been described with allowance for the effect of the excited opposite-parity configuration and the charge-transfer configuration. To take into account this effect, a modified crystal-field Hamiltonian and an effective line-strength operator for intermultiplet electric-dipole transitions are proposed. Their use in description of experimental data makes it possible to decrease the standard deviation by 37 and 20%, respectively, in comparison with the standard theories. The even-and odd-crystal-field parameters and the covalence parameters have been obtained from the description of Stark levels. The intensity parameters calculated on the basis of the covalence parameters and odd-crystal-field parameters are in satisfactory agreement with the parameters obtained from the description of the experimental oscillator strengths. [ABSTRACT FROM AUTHOR]

Abstract: Monoclinic 2at% Eu-doped KY(WO4)2 is grown by top-seeded solution growth method. Polarization-resolved absorption and stimulated-emission cross-section spectra are determined for this crystal. Spectroscopic properties of Eu:KY(WO4)2 are modeled within conventional Judd–Ofelt theory, as well as theory of f–f transition intensities for systems with anomalously strong configuration interaction, yielding absorption oscillator strengths, luminescence branching ratios and radiative lifetime of 5D0 state. The impact of excited-state absorption from this state on possibility of laser operation is discussed. Photoluminescent properties of Eu:KY(WO4)2 are determined. This crystal provides intense red emission with CIE coordinates x=0.670, y=0.329. [Copyright &y& Elsevier]

Abstract: Novel oxyfluoride glass doped with YbF3 and Eu2O3 is synthesized in the SiO2–PbO–PbF2–CdF2 system by melt-quenching technique. Its physical properties, as well as the optical absorption of Eu3+ and Yb3+ ions are studied. Spectroscopic properties of Eu3+ ions are modeled within modified Judd–Ofelt theory, yielding absorption oscillator strength, luminescence branching ratios and radiative lifetime of 5D0 state. Intrinsic emission of Eu3+ ions under direct excitation in the UV, as well as up-conversion luminescence under near-IR excitation via cooperative energy transfer, 2Yb3+ →Eu3+, are studied. In the latter case, the glass provides intense reddish-orange emission with CIE coordinates x =0.636, y =0.363. The asymmetry parameter R for Eu3+ emission in the studied glass is about 8. The efficiency of this transfer mechanism is estimated from shortening of 2F5/2(Yb3+) lifetime to be 10±1%. [Copyright &y& Elsevier]

Abstract: Pure and Nd-doped disordered calcium vanadate Ca10K(VO4)7, Ca10Li(VO4)7, Ca9La(VO4)7 and Ca9Y(VO4)7 single crystals with high optical quality were grown by Czochralsky technique in inert atmosphere. Their polarized absorption spectra were investigated in details. Spectroscopic parameters for Nd3+ ion were determined with Judd–Ofelt theory (J–O) and theory of f–f transition intensities for systems with intermediate or anomalously strong configuration interaction (ICI or ASCI approximation). Spectral and temporal characteristics of luminescence associated with 4F3/2→4I9/2, 4I11/2 and 4I13/2 transitions were analyzed, luminescence branching ratios and radiative lifetimes were calculated. Thermal expansion coefficients were determined for Ca9La(VO4)7 and Ca9Y(VO4)7 crystals in the directions of a and c crystallographic axes. Principal thermo-optic coefficients dn o/dT and dn e/dT were measured for Ca9La(VO4)7 crystal in the spectral range of 0.4–1.1μm. The potential of disordered vanadates for laser applications was analyzed from the point of thermal effects. [Copyright &y& Elsevier]