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Abstract NaPO 3 -ZnF 2 binary fluorophosphate glasses doped with trivalent erbium and monovalent copper were synthesized by the conventional melting and casting method using ErF 3 and CuCl as starting materials. The samples were systematically investigated using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. X-ray powder diffraction patterns confirmed that the as-prepared compounds were all amorphous. The glass transition temperature (T g) was observed around 230 °C by DSC analysis, while the thermal stability range (ΔT) was estimated to be between 90 and 140 °C. The measured value of the refractive index (n) was measured as 1.502 at a wavelength of 632.8 nm. Thermal annealing of the samples was performed at different temperatures above T g for various heat-treatment times. During these steps, monovalent copper and sodium ions were expected to be reduced, forming metallic nanoparticles. This transformation lead to coloration changes, depending on the annealing time and temperature, with respect to the transparency of the glasses. These spectroscopic changes are related to the plasmonic effects induced by the presence of both Cu and Na metallic nanoparticles, which promote red shift due to absorption. The VIS-NIR absorption spectra of the prepared glasses were investigated in the frame work of standard Judd-Ofelt (J-O) theory, which was used to determine the J-O intensity parameters, radiative transition probabilities and branching ratios for Er3+ ions embedded in the glasses. The calculated intensity parameters ( Ω 2,4,6 ) were compared to those obtained for Er3+ in several other glasses. Graphical abstract Image 1 Highlights • Fluorophosphate glasses have been synthesized in the NaP3-ZnF2 system and have been doped with Er3+ and Cu+. • Copper and sodium nanoparticles have been formed into this vitreous matrix using heat treatement. • Spectroscopic properties have been investigated and discussed on the basis of the Judd-Ofelt theory. [ABSTRACT FROM AUTHOR]

A new scheme of water cloud optical properties is proposed for correlated k-distribution (CKD) models, in which the correlation in spectral distributions between the gaseous absorption coefficient and cloud optical properties is maintained. This is an extension of the CKD method from gas to cloud by dealing with the gas absorption coefficient and cloud optical properties in the same way. Compared to the results of line-by-line benchmark calculations, the band-mean cloud optical property scheme can overestimate cloud solar heating rate, with a relative error over 30%% in general. Also, the error in the flux at the top of the atmosphere can be up to 20 W m−2 at a solar zenith angle of 0°. However, the error is considerably reduced by applying the new proposed CKD cloud scheme. The physical explanation of the large error for the band-mean cloud scheme is the absence of a spectral correlation between the gaseous absorption coefficient and the cloud optical properties. The overestimation of the solar heating rate at the cloud-top layer could affect the moisture circulation and limit the growth of cloud. It is found that the error in the longwave cooling rate caused by the band-mean cloud scheme is very small. In the infrared, the local thermal emission strongly affects the spectral distribution of the radiative flux, which makes the correlation between the gaseous absorption coefficient and cloud optical properties very weak. Therefore, there is no obvious advantage in emphasizing the spectral correlation between gas and cloud. [ABSTRACT FROM AUTHOR]

Abstract: Glasses having composition 20ZnO·xBi2O3·(79.5− x)B2O3·0.5Pr6O11 were prepared by melt quench technique. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction. The spectroscopic properties of these glasses were investigated by recording optical absorption and fluorescence spectra. The structural investigations of the glasses were carried out by recording the IR spectra. The optical properties of Pr3+ ions doped zinc borate glasses with varying concentration of bismuth oxide have been studied. The Judd–Ofelt intensity parameters Ω λ (λ =2, 4, 6) and other radiative properties like radiative transition probability, radiative life time, branching ratio and stimulated emission cross-section of the prepared glasses have been calculated. The variation of Ω 2 with Bi2O3 content has been attributed to changes in the asymmetry of the ligand field at the rare earth ion site and to the changes in their rare earth oxygen (RE-O) covalency. The branching ratio for 3P0 → 3F2 transition is 42% and the predicted spontaneous radiative transition probability rates are fairly high (14,347–14,607s−1). This is beneficial for lasing emission. The stimulated emission cross-section for all the emission bands has been calculated. [Copyright &y& Elsevier]

Abstract: This article presents the optical absorption and emission properties of Pr3+ and Nd3+ doped two different mixed alkali chloroborate glass matrices of the type 70B2O3·xLiCl·(30− x)NaCl and 70B2O3·xLiCl·(30− x)KCl (x =5, 10, 15, 20 and 25). The variation of Judd–Ofelt parameters (Ω 2, Ω 4 and Ω 6), total radiative transition probabilities (A T), radiative lifetimes (τ R) and emission cross-sections (σ p) with the variation of alkali contents in the glass matrix have been discussed in detail. The changes in the peak wavelengths of the hypersensitive transition and intensity parameters with x are correlated to the structural changes in the host matrix. The estimated radiative lifetimes of certain excited states of Pr3+ and Nd3+ in these two glass matrices are reported. Peak stimulated emission cross-sections (σ P) are reported for the observed emission transitions of Pr3+ and Nd3+ ions. Branching ratios (β) of the observed emission transitions obtained from the Judd–Ofelt theory are compared with the values obtained from the emission spectra. [Copyright &y& Elsevier]

The luminescence of Cu+ and Cu2+ ions in CsBr:Cu and CsBr:CuBr2 crystals, respectively, is investigated under excitation by synchrotron radiation in the CsBr fundamental absorption range at 10 K and 300 K. The existence of the luminescence bands of different origin: (i) the intrinsic radiative transition of Cu+ ions in the bands peaked at 2.61 eV and 2.23 eV, (ii) the recombination luminescence of Cu2+ ions in the bands peaked at 2.55 eV and 2.13 eV, (iii) the luminescence of excitons localized around Cu+ and Cu2+ ions in the band peaked at 3.08 eV and 3.38 eV, respectively, was found in CsBr:Cu and CsBr:CuBr2 crystals. The energies of creation of exciton localized around Cu+ and Cu2+ ions (6.06 eV and 6.09 eV, respectively, at 10 K) and excitons bound with these ions (5.83 eV and 5.99 eV at 300 K) were determined as well. [ABSTRACT FROM AUTHOR]

Abstract: Intersublevel transitions in semiconductor quantum dots are transitions of a charge carrier between quantum dot confined states. In InAs/GaAs self-assembled quantum dots, optically active intersublevel transitions occur in the mid-infrared spectral range. These transitions can provide a new insight on the physics of semiconductor quantum dots and offer new opportunities to develop mid-infrared devices. A key feature characterizing intersublevel transitions is the coupling of the confined carriers to phonons. We show that the effect of the strong coupling regime for the electron–optical phonon interaction and the formation of mixed electron–phonon quasi-particles called polarons drastically affect and control the dynamical properties of quantum dots. The engineering of quantum dot relaxation rates through phonon coupling opens the route to the realization of new devices like mid-infrared polaron lasers. We finally show that the measurement of intersublevel absorption is not limited to quantum dot ensembles and that the intersublevel ultrasmall absorption of a single quantum dot can be measured with a nanometer scale resolution by using phonon emission as a signature of the absorption. To cite this article: P. Boucaud et al., C. R. Physique 9 (2008). [Copyright &y& Elsevier]

Structures of H2CN and CH2CN molecules are similar to that of H2CO molecule. The H2CO has shown anomalous absorption for its transition 111 - 110 at 4.8 GHz in a number of cool molecular clouds. Though the molecules H2CN and CH2CN have been identified in TMC-1 and Sgr B2 through some transitions in ortho as well as in para species, here we have investigated the condition under which transitions 111 - 110 and 212 - 211 of these molecules may show anomalous absorption. For the present investigation, we have calculated energy levels and radiative transition probabilities. However, we have used scaled values for collisional rate coefficients. We found that relative values of collisional rate coefficients can produce the required anomalous absorption in 111 - 110 and 212 - 211 transitions in the molecules. [ABSTRACT FROM AUTHOR]

Abstract: Radiative transition parameters are tabulated for the band system of the silver dimer 107,109Ag2 for bands involving vibrational levels up to and , which amply covers the band transitions empirically studied in the seminal work of Kleman and Lindkvist [B. Kleman, S. Lindkvist, Arkiv för Fysik 9 (1955) 385–390]. The tabulated parameters include band-origin wavelengths and wavenumbers, Franck–Condon factors, r-centroids, electronic transition moments, Einstein coefficients (spontaneous emission rates) and absorption band oscillator strengths. Rydberg–Klein–Rees potential energy curves for both electronic states, based on the latest available spectroscopic constants, were calculated, and then used to solve the radial Schrödinger equation for the vibrational wave functions, and . The constant electronic transition moment function was fitted to previously reported relative absorption band strength measurements and the radiative lifetime of the state. A numerical integration of was performed in computing the Einstein coefficients and absorption band oscillator strengths, and these were found to differ negligibly from similar results obtained with the r-centroid approximation, as expected for a constant function. [Copyright &y& Elsevier]

Absorption and emission as well as emission decay times of Ho3+ ions embedded in LaAlO3 single crystal were measured. The experimental results were analysed in the frame of the Judd–Ofelt theory. Energy levels, oscillator strengths and probabilities of radiative transitions were determined. The results indicate on nonradiative transitions due to cross-relaxation down and up-conversions processes. [Copyright &y& Elsevier]