Enhanced photoluminescence features of Eu3+-modified di-ureasil-zirconium oxocluster organic-inorganic hybrids

In this work, a series of transparent di-ureasil hybrids containing different amounts of methacrylic acid modified zirconium tetrapropoxide (ZrMcOH) nanoclusters (5-85 mol%) and incorporating EuCl3 and [Eu(tta)(3)(H2O)(2)](tta = thenoyltrifluoroacetonate) complex were prepared. These hybrids are multi-wave-length emitters due to the convolution of the host intrinsic emission (electron-hole recombinations occurring in siliceous and urea cross-linkages) Eu3+ intra-4f(6) transitions. The ZrMcOH incorporation deviates the maximum excitation wavelength of the hybrid host intrinsic emission from the UV (365 nm) to the blue (420 nm) and enhances the absolute emission quantum yield from 6.0 +/- 0.6% to 9.0 +/- 0.9%, and contributes to an increase in the D-5(0) lifetime values, quantum efficiency due to a decrease in the non-radiative transition probability and OH groups coordinated to the Eu3+ ions. (C) 2010 Elsevier B.V. All rights reserved.

Transparent Er3+-activated lead fluorogermanate glass ceramics

Transparent glass ceramics containing β-PbF2:Er 3+ nanocrystals were obtained through appropriate thermal treatments of a glass of molar composition 60PbGeO3-10PbF2-30CdF 2 doped with 0.5 mol% Er3+. Their optical properties, as well as upconversion processes among erbium ions in the glass and glass ceramic matrix were studied. From absorption spectra, Judd-Ofelt parameters and radiative transition rates for several excited levels were calculated. Emission spectra in the visible and NIR regions were collected, and stimulated emission cross sections were obtained by McCumber theory for the 4F 13/2→4I15/2 transition at 1.5 μm. Red and green upconversion emissions were measured in glass and glass ceramics upon excitation at 980 nm; lifetimes were measured in order to assess the upconversion mechanisms.

Estudo das propriedades estruturais e ópticas do sistema vítreo 80TeO2-20WO3 dopado com Yb2O3

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Radiative Omega(-)->Xi(-)gamma decay and physics beyond the standard model

We investigate the impact of new physics beyond the Standard Model to the s --> d gamma process, which is responsible for the short-distance contribution to the radiative decay Omega-( )--> Xi(-) gamma. We study three representative extensions of the Standard Model, namely a one-family technicolor model, a two Higgs doublet model and a model containing scalar leptoquarks. When constraints arising from the observed b --> s gamma transition and the upper limit on D-0-(D) over bar(0) mixing are taken into account, we find no significant contributions of new physics to the s --> d gamma process.

Optical transition probabilities and compositional dependence of Judd-Ofelt parameters of Er3+ ions in fluoroindate glass

Fluoroindate glasses containing 1, 2, 3, and 4 mol% ErF3 were prepared in a dry box under an argon atmosphere. Absorption spectra of these glasses at room temperature were obtained. The Judd-Ofelt parameters Ωλ (λ = 2, 4, 6) for f-f transitions of Er3+ ions as well as transition probabilities, branching ratios, radiative lifetimes, and peak cross-sections for stimulated emission of each band were determined. The concentration effect on the intensities is analyzed. The optical properties of the fluoroindate glasses doped with Er3+ ions are compared with those of other glasses described in the literature. © 1995.

Radiative Omega(-)->Xi(-)gamma decay and physics beyond the standard model

We investigate the impact of new physics beyond the standard model to the s → dγ process, which is responsible for the short-distance contribution to the radiative decay Ω-Ξ-γ. We study three representative extensions of the standard model: namely, a one-family technicolor model, a two-Higgs-doublet model, and a model containing scalar leptoquarks. When constraints arising from the observed b→sγ transition and the upper limit on D0-D̄0 mixing are taken into account, we find no significant contributions of new physics to the s→dy process.

QCD sum rule approach to the s->d gamma contribution to the Omega(-)->Xi(-)gamma radiative decay

QCD sum rules are used to calculate the contribution of the short-distance single-quark transition s-->d gamma to the amplitudes of the hyperon radiative decay Omega(-)-->Xi(-) gamma. We reevaluate the Wilson coefficient of the effective operator responsible for this transition. We obtain a branching ratio which is comparable to the unitarity limit.