Bound states of the barium atom by the hyperspherical approach

We present a nonadiabatic hyperspherical calculation of the highly excited and low lying doubly excited states of the barium atom using effective potentials for the two optically active electrons' interactions. Within the hyperspherical adiabatic approach the investigation of the spectra is performed with potential curves and nonadiabatic couplings of a unique radial variable, which allows clear identification of the states. The convergence of energy is obtained within well established bound limits, and the precision is comparable to accurate configuration interaction calculations. A very good agreement with experimental results is obtained with only few nonadiabatic couplings. (C) 2004 American Institute of Physics

High precision calculation of multipolar dynamic polarizabilities and two- and three-body dispersion coefficients of atomic hydrogen

In this paper we investigate a variationally stable procedure for multipolar dynamic polarizabilities calculation as well as the two- and three-body van der Waals coefficients of the hydrogen atom. This approach provides precise, fast convergent values for real and imaginary frequency-dependent 2 (L) -pole dynamic polarizabilities. Highly accurate two- and three-body van der Waals dispersion coefficients are calculated from dynamic polarizabilities at imaginary photon frequencies. The present approach is also precise for higher interaction orders. The results are compared with previous calculations found in the literature.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Effect of heat treatment on the generation of structural defects in LaTaO4 ceramics and their correlation with photoluminescent properties

The synthesis, structure characterization, as well as luminescence properties of LaTaO4 ceramics were investigated in this study. The materials were prepared through the Pechini method. The characterization techniques, including the X-ray diffraction (XRD) as well as the scanning electron microscopy (SEM) were used to analyze the structure and microstructure, respectively. Details of emissions as a result of the type V-O* (or V-O**) defects were determined using photoluminescence (PL) measurements. (C) 2011 Elsevier B. V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Y2O3:Eu3+ (5 mol%) with Ag nanoparticles prepared by citrate precursor

Y2O3:Eu3+ (5 mol% Eu3+) and Y2O3:Eu3+ (5 mol% Eu3+) containing 1 mol% of Ag nanoparticles were prepared by heat treatment of a viscous resin obtained via citrate precursor. TEM and EDS analyses showed that Y2O3:Eu3+ (5 mol% Eu3+) is formed by nanoparticles with an average size of 12 nm, which increases to 30 nm when Ag is present because the effect of metal induced crystallization occurs. Ag nanoparticles with a size of 9 nm dispersed in Y2O3:Eu3+ (5 mol% Eu3+) were obtained and the surface plasmon effect on Ag nanoparticles was observed. The emission around 612 nm assigned to the Eu3+ (D-5(0) -> F-7(2)) transition enhanced when the Ag nanoparticles were present in the Y2O3:Eu3+ luminescent material. (C) 2010 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Structural and optical properties of Eu3+ and Mg2+ doped LiTaO3 obtained via the polymeric precursor method

This work reports on the pure lithium tantalate (LiTaO3), europium (III)-doped LiTaO3 and magnesium (II)-europium (III)-doped LiTaO3 preparared by the polymeric precursor method, using four different powered samples of Eu3+ ion concentrations 0.1 to 1at %. Structural and optical properties of powders have been studied. The different possible sites occupied by the rare earth were examined. The phase contents and lattice parameters were studied by the Rietveld method and the structural disorder in the LiTaO3 host caused by Eu3+ ions was analyzed. Results indicated LiTaO3 free of secondary phases at 650°C and the photoluminescence (PL) emission spectra showed the characteristic sharp emission bands given by Eu3+ ions when they are excited at a wavelength of 399 nm. An increase of dopants contents caused a non-homogeneous broadening and showed a slightly larger one when Mg was added. A displacement of the transition 5D0-7F0 to shorter wavelengths as function of Eu3+ concentration was also noticed