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A spectroscopic analysis is performed on Er[sup 3+] (4f[sup 11]) ions doped in NaBi(WO[sub 4])[sub 2] (NBWO) in order to assess this material for its potential as a near-infrared laser. The Judd–Ofelt model is applied to the room-temperature absorption intensities of Er[sup 3+] (4f[sup 11]) in NBWO to obtain the three phenomenological intensity parameters: Ω[sub 2]=5.50×10[sup -20] cm[sup 2], Ω[sub 4]=1.00×10[sup -20] cm[sup 2], and Ω[sub 6]=0.71×10[sup -20] cm[sup 2]. The intensity parameters are then used to determine the radiative decay rates (emission probabilities), radiative lifetimes, and branching ratios for the Er[sup 3+] transitions from the excited state multiplet manifolds to the lower lying manifold states. Using the radiative decay rates for the Er[sup 3+] (4f[sup 11]) transitions between the corresponding excited states and the lower lying states, the radiative lifetimes of eight excited states of Er[sup 3+] are determined in this host. Using the measured room temperature fluorescence lifetime of approximately 4.75 ms and the radiative lifetime of 5.63 ms as predicted by the Judd–Ofelt model for the [sup 4]I[sub 13/2]→[sup 4]I[sub 15/2] (1.52 μm) transition of Er[sup 3+] in NBWO the quantum efficiency is determined to be approximately 84% for this laser material. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Doublet and quartet states of the HS radical correlating with H([sup 2]S)+S([sup 3]P,[sup 1]D,[sup 1]S) were investigated by ab initio calculations, at the CASSCF-MRCI/aug-cc-pV5Z level of theory. Molecular parameters and spectroscopic constants obtained for both the ground (X [sup 2]Π) and the first excited (A [sup 2]Σ[sup +]) states represent the best overall theoretical description of this system to date. Transition moments, transition probabilities, and radiative and predissociative lifetimes were also determined for the X [sup 2]Π–A [sup 2]Σ[sup +] system. The values calculated for the radiative lifetimes of the A state show that previous results were too large. Theoretical predissociative lifetimes, although quite sensitive to the region of crossing of the potential energy curves, reproduce the experimental trends. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Highlights • High resolution VUV spectrum of tin excited in a vacuum spark was studied. • Transitions 4d75p- 4d75d in Sn VII are identified. • New 4d75d energy levels are derived from identified Sn VII wavelengths. • Parametric calculations are made for interpretation of Sn VII spectrum. • Transition probabilities are calculated for Sn VII lines in the region 153–1250 Å. Abstract The spectrum of tin excited in a vacuum spark was observed with a 6.6-m normal incidence spectrograph. The 4d75p – 4d75d transitions in Sn VII were studied. 137 spectral lines of these transitions in the region 556 - 763 Å were identified and 79 levels of the 4d75d configuration were found. Parametric calculations of the electric dipole transitions between the levels of the 4d8, 4p54d9, 4d75s, 4d76s, 4d75p and 4d75d configurations spanning the wavelength region from 153 Å through 1250 Å were performed. [ABSTRACT FROM AUTHOR]

Highlights • Lifetimes are 10−6 to 10−7 s for the e1Δ state and the 1st well of the f1Δ state. • The d1Σ+–a1Σ+, d1Σ+–b1Π, e1Π–a1Σ+, e1Π–b1Π, and g1Σ−–b1Π transitions are strong. • Emissions from the 1st well of f1Δ state to the b1Π and c1Δ states can be observed. • Lifetimes are approximately 10−6 s for the d1Σ+ and g1Σ− states. • Emissions originating from the 2nd well of the f1Δ state are very weak. • The emissions of the e1Π–d1Σ+ system are very weak. Abstract In this study, the potential energy curves are calculated for the a1Σ+, b1Π, c1Δ, d1Σ+, e1Π, f1Δ, and g1Σ− states of the AlN radical. The transition dipole moments between them are computed. The rotationless radiative lifetimes of the vibrational levels are found to be approximately several µs for the d1Σ+ and g1Σ− states, on the order of several hundred ns for the e1Π state, and one-tenth to several µs for the deep well of the f1Δ state. These results suggest that the spontaneous emissions originated from these states occur readily. The rotationless radiative lifetimes of the vibrational levels are on the order of 10–100 µs for the c1Δ state, 1000 µs for the vdW minimum of the f1Δ state, and 10–1000 µs for the b1Π state. In addition, the rotationless radiative lifetimes of these states decrease with the increasing vibrational level. This result suggests that the spontaneous emissions generated from these states at lower levels should be difficult to occur. The Einstein coefficients of spontaneous emissions from the d1Σ+–a1Σ+, d1Σ+–b1Π, e1Π–a1Σ+, e1Π–b1Π, and g1Σ−–b1Π systems, as well as from the f1Δ state to the b1Π and c1Δ states are large, indicating that the emissions of these systems can be measured readily via spectroscopy. The Einstein coefficients of the e1Π–d1Σ+ transition are very small and the emissions originating from the vdW minimum of the f1Δ state are very weak, predicting that these transitions are very difficult to be detected in spectroscopy experiments. Graphical abstract Image, graphical abstract The transition probabilities of emissions are calculated between the a1Σ+, b1Π, c1Δ, d1Σ+, e1Π, f1Δ, and g1Σ− states of the AlN radical. The rotationless radiative lifetimes of the vibrational levels are approximately 10−6 s for the d1Σ+ and g1Σ− states, and 10−6 to 10−7 s for the e1Π state and the first well of the f1Δ state, predicting that spontaneous emissions originating from them occur readily. The rotationless radiative lifetimes are about 10−4 to 10−5 s for the c1Δ state, 10−3 to 10−4 s for the second well of the f1Δ state, and 10−3 to 10−5 s for the b1Π state. Emissions from the d1Σ+–a1Σ+, d1Σ+–b1Π, e1Π–a1Σ+, e1Π–b1Π, and g1Σ−– b1Π systems, as well as those from the first well of the f1Δ state to the b1Π and c1Δ states are strong. Emissions of the e1Π–d1Σ+ system and emissions originating from the second well of the f1Δ state are so weak that they are hardly measured through spectroscopy. [ABSTRACT FROM AUTHOR]

In this article, Dy 3+ doped and K + co-doped BaWO 4 phosphors were synthesized by a solid state reaction method and the effect of Dy 3+ /K + doping/co-doping concentration on the structural and photoluminescence (PL) properties were investigated. Rietveld refinement analysis revealed the tetragonal structure of the phosphors and lattice parameter contraction/expansion due to doping/co-doping. The energy band gap reduced with the increasing doping and co-doping concentration in the host materials. Judd-Ofelt (J-O) parameters were calculated from the excitation spectra. J-O parameters described the covalency dependency on the environment around the Dy 3+ ion in the lattice. Intense white light was achieved by Dy 3+ doping. The PL concentration quenching mechanism was described and the suggested quenching mechanism was dipole-dipole interactions. K + co-doping with Dy 3+ doping suggested that charge compensation improved the colour point and increased the internal quantum efficiency from 56 to 67% owing to a reduction in the non-radiative transitions which was proven by using the J-O theory. A short life time (281.60 μs) and CCT value (5392 K) very close to day light of the Ba 1-x-y Dy x K y WO 4 (x = 0.10; y = 0.05) indicated the suitability of the tungstate based phosphors for white light emitting diode applications. [ABSTRACT FROM AUTHOR]

Accurate radiative transition probabilities of diatomic electronic systems are required to calculate the discrete radiation of plasmas. However, most of the published transition probabilities are obtained using older spectroscopic constants and electronic transition moment functions (ETMFs), some of which deviates greatly from experimental data. Fortunately, a lot of new spectroscopic constants that include more anharmonic correction terms than the earlier ones have been published over the past few years. In this work, the Einstein coefficients, Franck–Condon factors and absorption band oscillator strengths are calculated for important diatomic radiative transition processes of N 2 -O 2 , CO 2 -N 2 and H 2 plasmas produced in entering into the atmosphere of Earth, Mars and Jupiter. The most up-to-date spectroscopic constants are selected to reconstruct the potential energy curves by the Rydberg–Klein–Rees (RKR) method. Then the vibrational wave functions are calculated through the resolution of the radial Schrödinger equation for such potential energy curves. These results, together with the latest “ab-initio” ETMFs derived from the literature are used to compute the square of electronic-vibrational transition moments, Einstein coefficients and absorption band oscillator strengths. Moreover, the Franck–Condon factors are determined with the obtained vibrational wave functions. In the supplementary material we present tables of the radiative transition probabilities for 40 band systems of N 2 , N 2 + , NO, O 2 , CO, CO + , CN, C 2 and H 2 molecules. In addition, the calculated radiative lifetimes are systematically validated by available experimental results. [ABSTRACT FROM AUTHOR]

Tellurite glasses with different concentrations of Nd 3 + ions and WO 3 oxide were prepared using melt-quenching technique. The prepared glasses were characterized by the absorption spectrum, emission spectrum, Raman spectrum, fluorescence decay curve and DSC curve measurements, together with Judd-Ofelt intensity parameter, radiative transition probability and fluorescence branching ratio calculations to reveal the effects of Nd 3 + and WO 3 concentration on the structure, photo-luminescence and thermal stability. Under the excitation of 808 nm LD, three near-infrared band fluorescence emissions at around 0.9, 1.06 and 1.34 μm, corresponding to the transitions from the 4 F 3/2 → 4 I 9/2 , 4 I 11/2 and 4 I 13/2 levels respectively, are observed, and the fluorescence intensities increase with the increase of doped Nd 3 + concentration up to 0.6 mol%. Furthermore, the fluorescence intensities continue to increase greatly with the introduction of WO 3 oxide. Compared with 0.6 mol% Nd 3 + -doped glass without WO 3 oxide, the luminescent intensity of 1.06 μm band increases by about 95% in the glass with 9 mol% amount of WO 3 , which is mainly attributed to the rapid population of Nd 3 + ions in the excited level 4 F 3/2 due to the enhanced multi-phonon relaxation process with the increased phonon energy of glass host. Therefore, the enhanced luminescent intensity as well as the good thermal stability demonstrated by DSC curve indicate that the prepared 0.6 mol% Nd 3 + -doped tellurite glass with 9 mol% amount of WO 3 oxide is a potential gain medium applied for near-infrared band solid-state lasers and fiber amplifiers. [ABSTRACT FROM AUTHOR]

A theoretical framework is presented that exposes the radiative-dynamical relationships that govern the subcritical destabilization of African easterly waves (AEWs) by Saharan mineral dust (SMD) aerosols. The framework is built on coupled equations for quasigeostrophic potential vorticity (PV), temperature, and SMD mixing ratio. A perturbation analysis yields, for a subcritical, but otherwise arbitrary, zonal-mean background state, analytical expressions for the growth rate and frequency of theAEWs. The expressions are functions of the domain-averaged wave activity,which is generated by the direct radiative effects of theSMD. Thewave activity is primarily modulated by the Doppler-shifted phase speed and the background gradients in PV and SMD. Using an idealized version of the Weather Research and Forecasting (WRF) Model coupled to an interactive dust model, a linear analysis shows that, for a subcritical African easterly jet (AEJ) and a background SMD distribution that are consistent with observations, the SMD destabilizes the AEWs and slows their westward propagation, in agreement with the theoretical prediction. The SMD-induced growth rates are commensurate with, and can sometimes exceed, those obtained in previous dust-free studies in which the AEWs grow on AEJs that are supercritical with respect to the threshold for barotropic-baroclinic instability. The clarity of the theoretical framework can serve as a tool for understanding and predicting the effects of SMD aerosols on the linear instability of AEWs in subcritical, zonal-mean AEJs. [ABSTRACT FROM AUTHOR]

Hydrogen-like ions with high Z present unique opportunities to promote the understanding of atomic structure. On the other hand, determining the atomic structure of hydrogen-like atoms provides us the test of relativistic effects as well as accurate values of the spectral characteristics required for many applications. For this reason we have calculated level energies of hydrogen like thorium (Th89+, Z = 90) with both multiconfiguration Hartree-Fock (MCHF) and multiconfiguration Dirac-Fock (MCDF) methods. These calculations have contained the Breit-Pauli relativistic corrections in MCHF calculation and quantum electrodynamics effects in MCDF calculations besides electron correlations. The wavelengths, λ, weighted oscillator strengths, gf-value, and transition probabilities, Aki, have been also represented for allowed (E1) and forbidden (E2 and M1) transitions. We have compared our results with only theoretical work results because there is no available experimental data for Th89+. [ABSTRACT FROM AUTHOR]

The proton induced atomic inner-shell ionization processes comprising radiative and non-radiative transitions are characterized by physical parameters, namely, the proton ionization cross sections, X-ray emission rates, fluorescence yields and Coster-Kronig (CK) transition probabilities. These parameters are required to calculate the K/L/M shell X-ray production (XRP) cross sections and relative X-ray intensity ratios, which in turn are required for different analytical applications. The current status of different physical parameters is presented in this report for use in various applications. [ABSTRACT FROM AUTHOR]

The determination of radiative transition probabilities or oscillator strengths is of common interest in astrophysics. The analysis of the high-resolution stellar spectra is now available in order to estimate the stellar abundances. In this paper, 93 experimentally obtained transition probability values (Aki) for singly ionized krypton spectral lines belonging to the ultraviolet (UV) wavelength region (208-360) nm are presented. These data, expressed in absolute units, were derived from the measurements of relative spectral line intensities and the values of transition probability data taken from the literature. The results obtained extend considerably the transition probability data base. As a light source, a plasma from a low-pressure pulsed arc was used. Its electron density was in the range of (1.5-3.4) × 1022 m-3, while the temperature was between 28 000 and 35 000 K. A detailed analysis of the results is also given. Only a few relative and a few absolute transition probabilities from other authors, for the mentioned spectral region, are available in the literature. [ABSTRACT FROM AUTHOR]

Er 3+ /Ce 3+ co-doped and B 2 O 3 modified tellurite glasses with initial composition of TeO 2 –GeO 2 –Li 2 O–Nb 2 O 5 were prepared using melt-quenching technique for potential applications in Er 3+ -doped fiber amplifiers (EDFAs) and lasers. The absorption spectra, fluorescence spectra, up-conversion spectra, Raman spectra and differential scanning calorimeter (DSC) curves of glass samples were measured to evaluate the effect of B 2 O 3 modification on the 1.53 μm band spectroscopic properties of Er 3+ , structural nature and thermal stability of glass hosts. It was shown that the introduction of an appropriate amount of B 2 O 3 oxide can further improve the 1.53 μm band fluorescence emission through an enhanced phonon-assisted energy transfer (ET) from Er 3+ to Ce 3+ ions under the excitation of 980 nm, and the quantitative studies were carried out to elucidate the ET mechanism via calculating the microscopic parameters and phonon contribution ratios. Meanwhile, the thermal stability of glass hosts increases slightly with the introduction of B 2 O 3 oxide. Furthermore, the 1.53 μm band optical signal amplification was simulated based on the rare-earth ion rate and light power propagation equations. An increment in signal gain by about 1.4 dB at 1532 nm was observed in the Er 3+ /Ce 3+ co-doped tellurite glass fiber containing 6 mol% amount of B 2 O 3 oxide, and the maximum signal gain reaches to 31 dB on a 50 cm fiber pumped at 980 nm with power 200 mW. The present results indicate that the prepared Er 3+ /Ce 3+ co-doped tellurite glass modified by an appropriate amount of B 2 O 3 oxide has good prospect as a gain medium applied for 1.53 μm band EDFAs and lasers. [ABSTRACT FROM AUTHOR]

Within the validity of perturbation theory an analytic expression for energy of an electromagnetic pulse with a Gaussian envelope absorbed on an excited inhomogeneously broadened transition is derived and subsequently analyzed. A dependence of the absorbed energy on the pulse duration and relative detuning of its carrier frequency from the central frequency of the transition is analyzed. The range is determined of the problem parameters for which nonlinearity of the considered problem is most pronounced. [ABSTRACT FROM AUTHOR]

The electric dipole transition probabilities and the oscillator strengths of neutral scandium have been calculated using the quantum defect orbital theory and the Cowan code for the 3d4s2-3d4s4p, 3d24s-3d24p, and 3d4s2-4s24p transitions. In addition, a parametric analysis of the fine structure for the 3d4s2 configuration of even parity is performed using Cowan code. The transition probabilities and the oscillator strengths obtained in this work are mostly in agreement with the data obtained from different theoretical works given in the literature. Moreover, transition probabilities for 24 levels of neutral scandium are given for the first time. [ABSTRACT FROM AUTHOR]

Energy levels and radiative rates are reported for transitions in Cl-like W LVIII. Configuration interaction (CI) has been included among 44 configurations (generating 4978 levels) over a wide energy range up to 363 Ryd, and the general-purpose relativistic atomic structure package ( grasp ) adopted for the calculations. Since no other results of comparable complexity are available, calculations have also been performed with the flexible atomic code ( fac ), which help in assessing the accuracy of our results. Energies are listed for the lowest 400 levels (with energies up to ∼98 Ryd), which mainly belong to the 3s 2 3p 5 , 3s3p 6 , 3s 2 3p 4 3d, 3s 2 3p 3 3d 2 , 3s3p 4 3d 2 , 3s 2 3p 2 3d 3 , and 3p 6 3d configurations, and radiative rates are provided for four types of transitions, i.e. E1, E2, M1, and M2. Our energy levels are assessed to be accurate to better than 0.5%, whereas radiative rates (and lifetimes) should be accurate to better than 20% for a majority of the strong transitions. [ABSTRACT FROM AUTHOR]

By applying AUTOSTRUCTURE code, the energies and transitions for allowed (E1) and forbidden (E2, M1, and M2) lines for low-lying configurations in magnesium-like tungsten (W62+) are studied. The electron correlation and relativistic effects are included in computations. Good agreement between our results and available other results are found. The data for E2, M1 and M2 besides some E1 transitions for low-lying levels are presented for the first time. [ABSTRACT FROM AUTHOR]

Transition probabilities and oscillator strengths for electric dipole radiation in triply ionized praseodymium are reported for the first time in this paper. They were computed using a semi-empirical relativistic Hartree-Fock approach including core-polarization effects. Due to the lack of experimental data in the Pr IV spectrum, the accuracy of our results is estimated and discussed on the basis of comparisons between calculations performed with a similar physical model and laboratory measurements previously published for the isoelectronic ion Ce2+. In view of their great interest in optical materials and nanophotonics, radiative rates for forbidden lines within the 4f² ground-state configuration of Pr3+ were also calculated in our work. [ABSTRACT FROM AUTHOR]

The emission band spectra of Tl2Ga2Se3S layered crystals have been studied in the temperature range of 10- 50 K and in the wavelength region of 540-700 nm. A broad photoluminescence band centered at 626 nm (1.98 eV) was observed at T = 10 K. Variation of emission band has been studied as a function of excitation laser intensity in the 0.4-51.5 mW cm-2 range. The analysis of the spectra reveals that the peak energy position changes with laser excitation intensity (blue shift). This behavior of the emission band is in agreement with the idea of separation inhomogeneity of donor-acceptor pairs. Radiative transitions from the moderately deep donor level Ed = 270 meV to the shallow acceptor level Ea = 10 meV were suggested to be responsible for the observed photoluminescence band. [ABSTRACT FROM AUTHOR]

Abstract: The electric dipole transition probabilities and the lifetimes of excited levels have been calculated using the weakest bound electron potential model theory (WBEPMT) and the quantum defect orbital theory (QDOT) in atomic fluorine. In the calculations, many of transition arrays included both multiplet and fine-structure transitions are considered. We employed Numerical Coulomb Approximation (NCA) wave functions and numerical non-relativistic Hartree–Fock (NRHF) wave functions for expectation values of radii in determination of parameters. The necessary energy values have been taken from experimental energy data in the literature. The calculated transition probabilities and lifetimes have been compared with available theoretical and experimental results. A good agreement with results in literature has been obtained. Moreover, some transition probability and the lifetime values not existing in the literature for some highly excited levels have been obtained using these methods. [Copyright &y& Elsevier]

Abstract: Energy levels, transition probabilities, oscillator strengths, line strengths, and lifetimes have been calculated for Oxygen-like Gallium, Ga XXIV. The configurations 2s22p4, 2s2p5, 2p6, 2s2p4 , 2s22p3 , and 2p5 were used in calculations and 226 fine-structure levels were obtained. The fully relativistic GRASP code has been adopted, and results are reported for all electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2) transitions among the lowest 226 levels of Ga XXIV, belonging to the configurations. Comparisons have been made with earlier available theoretical and experimental results. [Copyright &y& Elsevier]

Abstract: Large-scale multiconfiguration Hartree–Fock and Dirac–Fock calculations have been performed for the ground configuration, [Kr]4d104f4, energy levels of the W24+ ion. The relativistic corrections were taken into account in the quasirelativistic Breit–Pauli and fully relativistic Breit (taking into account QED effects) approximations. The role of correlation, relativistic, and QED corrections is discussed. Line strengths, oscillator strengths, and transition probabilities in the Coulomb and Babushkin gauges are presented for the electric quadrupole (E2) transitions among these levels. The magnetic dipole transitions are also investigated. Dependence of the E2 transition probabilities on the gauge condition of the electromagnetic field potential is studied as well. [Copyright &y& Elsevier]

The Xb(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider at √s = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb-1, these states are reconstructed through their radiative decays to Y( 1 S, 2S) with Y → μ+μ-. In addition to the mass peaks corresponding to the decay modes (1P, 2P) → Y(1S)γ, a new structure centered at a mass of 10.530 ± 0.005(stat) ± 0.009(syst) GeV is also observed, in both the Y(1S,)γ and Y(2S)γ decay modes. This structure is interpreted as the Xb(3P) system. [ABSTRACT FROM AUTHOR]

The CHIANTI spectral code consists of an atomic database and a suite of computer programs to calculate the optically thin spectrum of astrophysical objects and carry out spectroscopic plasma diagnostics. The database includes atomic energy levels, wavelengths, radiative transition probabilities, collision excitation rate coefficients, and ionization and recombination rate coefficients, as well as data to calculate free--free, free--bound, and two-photon continuum emission. Version 7 has been released, which includes several new ions, significant updates to existing ions, as well as Chianti-Py, the implementation of CHIANTI software in the Python programming language. All data and programs are freely available at http://www.chiantidatabase.org, while the Python interface to CHIANTI can be found at http://chiantipy.sourceforge.net. [ABSTRACT FROM AUTHOR]

Qualitative analysis of additional energy of neutrino and antineutrino in plasma is performed. A general expression for the neutrino self-energy operator is obtained in the case of ultra-high energies when the local limit of the weak interaction is not valid. The neutrino and antineutrino additional energy in plasma is calculated using the dependence of the W- and Z-boson propagators on the momentum transferred. The kinematical region for the neutrino radiative transition (the so-called "neutrino spin light") is established for some important astrophysical cases. For high energy neutrino and antineutrino, dominating transition channels in plasma, νe + e+ → W+, $\bar\nu_e + e^- \to W^-$ and $\bar\nu_{\ell} + \nu_{\ell} \to Z$, are indicated. [ABSTRACT FROM AUTHOR]

We present a numerical study of the properties of optical forces on moving atoms derived from purely stimulated processes produced by multiple adiabatic rapid-passage sequences. The optical Bloch equations are solved for a carefully timed sequence of frequency-swept pulses that can produce a force much larger than the ordinary radiative force. We describe the effects of the sweep range, peak intensity, sweep direction, number of pulses, atomic velocity, and spontaneous emission. Since the momentum of thermal atoms is much larger than that transferred by a single absorption-stimulated emission cycle, multiple repetitions are needed to make a significant velocity change. [ABSTRACT FROM AUTHOR]

An approach to simulate the signal at the top of the atmosphere (TOA) in the visible and near-infrared regions is based on the exploitation of CIMEL sky radiances in three spectral bands (i.e. 440 nm, 675 nm and 870 nm). An iterative method, developed at the Laboratoire Interdisciplinaire des Sciences de l'Environnement (LISE, Wimereux, France), allows the aerosol phase function to be extracted from these ground-based measurements. Sky radiances are corrected for the multiple scattering based on the use of a radiative transfer tool and the aerosol phase function is derived from the primary scattering approximation. In order to cover the largest range of scattering angles, only the sky radiances acquired at low solar elevations are employed in this retrieval. These extreme geometrical conditions impose to adapt the radiative transfer code and to check its performances. Limits, performances and accuracy of this inverse method are discussed and illustrated both from the radiative transfer computations and from the CIMEL measurements. Moreover, thanks to the fact that the Aerosol Robotic Network (AERONET) also proposes CIMEL derived aerosol phase functions, the latter have been compared with our results. The substantial discrepancies that appear between the two sets are explained by the different objectives used in the two retrieval algorithms. [ABSTRACT FROM AUTHOR]

Abstract: Glasses having composition 20ZnO·xBi2O3·(79− x)B2O3 (15⩽ x ⩽35mol%) and doped with 1mol% Sm3+ ions have been prepared by melt quench technique. Optical absorption and fluorescence spectra have been recorded. Judd–Ofelt approach has been applied for the f ↔ f transition of Sm3+ ions to evaluate various intensity parameters (Ω 2, Ω 4, Ω 6). The variations in intensity parameters, radiative transition probabilities and hypersensitive band positions with composition have been discussed. The variation of Ω 2 with Bi2O3 content have been attributed to change 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, whereas the variation of Ω 6 is found to be strongly dependent on nephlauxetic effect. The shift of the hypersensitive band shows that the covalency of the RE–O bond increases with increase of Bi2O3 content due to increased interaction between the Sm3+ ion and non-bridging oxygens. The radiative transition probabilities for the Sm3+ ions are large in zinc bismuth borate glasses, suggesting their suitability as laser material. [Copyright &y& Elsevier]

The wave functions of one-electron states above the 4 d10 core have been calculated within the relativistic perturbation theory with a zero-order model potential. The wavelengths and probabilities of electric dipole transitions in an Ag-like ion have been calculated for the 5 s-5 p, 5 p-5 d, 5 d-5 f, and 4 f-5 d transitions. The data obtained are compared with the results of calculations by the relativistic Hartree-Fock method and within the relativistic many-body perturbation theory. The theoretical results are compared with experimental data on the lifetimes of energy levels in Ag-like ions. [ABSTRACT FROM AUTHOR]

A method is presented to calculate the radiative transition probabilities and the radiative recombination rate coefficients between electronic molecular states. Total transition probabilities are determined from vibrational transition probabilities without considering the detailed rotational structure of the molecular electronic states. Radiative recombination rate coefficients are obtained from the computation of vibrational photo-ionisation cross sections. Concerning spontaneous emission, Lyman (B → X) and Werner (C → X) band systems of H2 and Meinel (A → X), (B → A) and (B → X) band systems of OH are investigated. For radiative recombination, transitions between H (X) and H2(X), and between OH+(X, a, A, b, and c) and OH(X) are considered. Transition probabilities and recombination rate coefficients are calculated as a function of temperature in the range 1500–15 000 K. [ABSTRACT FROM AUTHOR]

Explicit formulasfor strongly forbidden magnetic-dipole transitiions between states njl and n′jl in the hydrogen atom and light hydrogen-like ions are derived. The expressions for transition probabilities are presented in the form W = Dα m e(α Z)10 (in relativistic units), where m e is the electron mass, α is the fine-structure constant, and Z is the nuclear charge; the constants D are presented in an analytical form. Before now, only the D coefficient corresponding to the 1 s1/2–2 s1/2 transition was known in explicit form. The results obtained can be used in designing an experiment on parity violation in the hydrogen atom. [ABSTRACT FROM AUTHOR]

New measurements of radiative lifetimes for 9 levels in singly ionized tungsten (WII) have been performed with the time-resolved laser-induced-fluorescence technique. Transition probabilities have been obtained from a combination of experimental lifetimes and theoretical branching fractions. The reliability of the present results is assessed through the good agreement observed between the calculated lifetimes and the experimental values from this work and from previous publications. These new results fill in a gap in the available data for this atomic species particularly important for fusion reactors. [ABSTRACT FROM AUTHOR]

Systematic calculations of the probabilities and energies of radiative transitions in doubly excited 3 l3 l′, 3 l4 l′, and 4 l4 l′ states of oxygen, carbon, and nitrogen ions have been carried out within the Hartree-Fock approximation. The emission spectra are obtained, and analysis of the changes in the spectral characteristics with a change in the charge and the number of additional electrons in the ground state of the initial ion is performed. The data obtained are used to interpret the X-ray spectra of the atmospheres of planets and comets. [ABSTRACT FROM AUTHOR]

Two types of radiative transitions were observed in the low-temperature photoluminescence spectra of Pb1− x Eu x Te (0 ≤ x ≤ 0.09) solid solutions: an intense line corresponding to the transitions from the conduction to the valence band and a series (up to 15) of narrow lines corresponding to the transitions from the hybridized conduction band to the split Eu3+ levels. The intensity of the discrete lines increases with x, and their energies (and intensities) weakly depend on the temperature. The absorption and emission of the discrete lines are caused by the 4 f 7(8 S 7/2) ↔ 4 f 6(7 F J )[ L + 5 dt 2 g ] transitions. [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]

Mechanistic photodissociation of a polyatomic molecule has long been regarded as an intellectually challenging area of chemical physics, the results of which are relevant to atmospheric chemistry, biological systems, and many application fields. Carbonyl compounds play a unique role in the development of our understanding of the spectroscopy, photochemistry, and photophysics of polyatomic molecules and their photodissociation has been the subject of numerous studies over many decades. Upon irradiation, a molecule can undergo internal conversion (IC) and intersystem crossing (ISC) processes, besides photochemical and other photophysical processes. Transient intermediates formed in the IC and ISC radiationless processes, which are termed “dark”, are not amenable to detection by conventional light absorption or emission. However, these dark intermediates play critical roles in IC and ISC processes and thus are essential to understanding mechanistic photochemistry of a polyatomic molecule. We have applied the multiconfiguration complete active space self-consistent field (CASSCF) method to determine the dark transient structures involved in radiationless processes for acetophenone and the related aromatic carbonyl compounds. The electronic and geometric structures predicted for the dark states are in a good agreement with those determined by ultrafast electron diffraction experiments. Intersection structure of different electronic states provides a very efficient “funnel” for the IC or ISC process. However, experimental determination of the intersection structure involved in radiationless transitions of a polyatomic molecule is impossible at present. We have discovered a minimum energy crossing point among the three potential energy surfaces (S 1, T 1, and T 2) that appears to be common to a wide variety of aromatic carbonyl compounds with a constant structure. This new type of crossing point holds the key to understanding much about radiationless processes after photoexcitation of aromatic carbonyl compounds. The importance of ab initio determination of transient structures in the photodissociation dynamics has been demonstrated for the case of the aromatic carbonyl compounds. In addition, the detailed knowledge of mechanistic photochemistry for aromatic carbonyl compounds forms the basis for further investigating photodissociation dynamics of a polyatomic molecule. [ABSTRACT FROM AUTHOR]

The stimulated radiation pressure acting on an atom nonadiabatically interacting with the field of counterpropagating frequency-modulated waves is shown to reach high values typical for the rapid adiabatic passage of the instantaneous frequency of the field of the counterpropagating waves through resonance with an atomic transition. Under the appropriate choice of interaction parameters, the radiation pressure changes insignificantly in a wide range of atomic velocities. [ABSTRACT FROM AUTHOR]

We have carried out an isotope study on the band gap and radiative transition spectra of boron nitride nanotubes (BNNTs) using both experimental and theoretical approaches. The direct band gap of BNNTs was determined at 5.38 eV, independent of the nanotube size and isotope substitution, by cathodoluminescences (CL) spectra. At lower energies, several radiative transitions were observed, and an isotope effect was revealed. In particular, we confirmed that the rich CL spectra between 3.0 and 4.2 eV reflect a phonon−electron coupling mechanism, which is characterized by a radiative transition at 4.09 eV. The frequency red shift and peak broadening due to isotopic effect have been observed. Our Fourier transform infrared spectra and density functional theory calculations suggest that those radiative transitions in BNNTs could be generated by a replacement of some nitrogen atoms with oxygen. [ABSTRACT FROM AUTHOR]

An a priori study of the turbulence radiation interaction (TRI) is performed on numerical data from Direct Numerical Simulation (DNS) of a turbulent flame. The influence of the various correlations that appear in the radiative emission is investigated and their impact is evaluated in the context of Large Eddy Simulation (LES). In LES, only filtered quantities are computed, where the filter is the grid. The radiative emission is reconstructed first from the exact, then filtered solution variables and the sensitivity to the filter size is evaluated. Three approaches are used to take into account the subgrid scale correlations: the no-TRI, partial TRI and full TRI approaches. Results show that the full TRI is exact compared to the reference emission and that the partial TRI performs worse than the no-TRI for the studied configuration. This indicates that in the studied case, the TRI must be considered in LES in a full formulation. [ABSTRACT FROM AUTHOR]

Abstract: Nd3+-doped NaLa(WO4)2 single crystal with a dimension of ∅20mm×40mm and a good optical quality was grown by Czochralski method. The polarized absorption spectra and emission spectra were measured at room temperature. The absorption cross-section and emission cross-section were presented. The Judd–Ofelt theory, extended to anisotropic system, has been applied to evaluate the intensity parameters Ω t (t =2,4,6), radiative transition rates A, radiative lifetimes τ R and fluorescent branching ratios β. The calculated radiative lifetime was compared with the experiment data for the 4F3/2 emitting level. All spectral features are strongly affected by an inhomogeneous broadening connected with the ‘disordered crystal’ character of the title compound. [Copyright &y& Elsevier]

Abstract: Electron impact collision strengths among 560 levels of Si IX, 320 levels of Si X, and 350 levels of Si XI have been calculated using the Flexible Atomic Code of Gu [M.F. Gu, Astrophys. J. 582 (2003) 1241]. Collision strengths Ω at 10 scattered electron energies, namely 10, 50, 100, 200, 400, 600, 800, 1000, 1500, and 2000eV, are reported. Assuming a Maxwellian energy distribution, effective collision strengths ϒ are obtained on a finer electron temperature grid of 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0MK, which covers the typical temperature range of astrophysical hot plasmas. Additionally, radiative rates A and weighted oscillator strengths gf are given for the more probable transitions among these levels. Comparisons of our results with available predictions reported in earlier literature are made and the accuracy of the data is assessed. Most transitions exhibit a good agreement, but large differences in gf appear for a few cases, which are due to the different configuration interactions included in different theoretical calculations. For excitations among levels of the ground and lower excited configurations, large discrepancies of ϒ may have resulted from the consideration of resonance effects in earlier works. [Copyright &y& Elsevier]

We continue the investigation of mesons in terms of the spectral integral equation initiated before for the $$b\bar b$$ and $$c\bar c$$ systems; we consider the light-quark ( u, d, s) mesons with masses M ≤ 3 GeV. The calculations have been performed for the mesons lying on linear trajectories in the ( n, M 2) planes, where n is the radial quantum number. Our consideration relates to the $$q\bar q$$ states with one component in the flavor space, with the quark and antiquark masses equal to each other, such as π(0−+), ρ(1−−), ω(1−−), ϕ(1−−), a 0(0++), a 1(1++), a 2(2++), b 1(1+−), f 2(2++), π 2(2−+), ρ 3(3−−), ω 3(3−−), ϕ 3(3−−), π 4(4−+) at n ≤ 6. We obtained the wave functions and mass values of mesons lying on these trajectories. The corresponding trajectories are linear, in agreement with data. We have calculated the two-photon decays π, a 0(980), a 2(1320), f 2(1285), f 2(1525) and radiative transitions ρ, ω → γπ, which agree qualitatively with the experiment. On this basis, we extract the singular part of the interaction amplitude, which corresponds to the so-called “confinement interaction.” The description of the data requires the presence of the strong t-channel singularities for both scalar and vector exchanges. [ABSTRACT FROM AUTHOR]

Abstract: The atomic inner-shell vacancy decay processes comprised of radiative and nonradiative transitions are characterized by the fluorescence, Auger and Coster-Kronig yields. We present a review of our recent measurements of the L i (i=1,2,3) sub-shell fluorescence yields (ωi ) and the L1–L3 Coster-Kronig transition probabilities (f 13) for elements with 70⩽Z⩽92 following photoionization. The comparison of the measured ωi and f 13 values with the theoretical ones, based on the relativistic Dirac–Hartree–Slater (RDHS) model calculations, indicated the need for more refined calculations of transition probabilities for different Coster-Kronig transitions. [Copyright &y& Elsevier]

Abstract: Weisskopf–Wigner theory applied to the macroscopically quantized field shows that the spontaneous emission rate of an excited atom is unaffected by a dielectric, rather than enhanced by a factor of the refractive index, as local-field effects are eliminated in the continuum approximation. Dielectric effects on an atom must be calculated microscopically. [Copyright &y& Elsevier]

Radiative parameters for transitions depopulating the levels belonging to the 4d85s2, 4d96s and 4d95d configurations of Ag ii have been obtained from a combination of theoretical lifetimes and experimental branching fractions. On the experimental side, a laser-produced plasma was used as a source of Ag+ ions. The light emitted by the plasma was analysed by a grating monochromator coupled with a time-resolved optical multichannel analyser system. Spectral response calibration of the experimental system was performed using a deuterium lamp in the wavelength range from 200 to 400 nm, and a standard tungsten lamp in the range from 350 to 600 nm. The transition probabilities were obtained from measured branching ratios and theoretical radiative lifetimes of the corresponding states calculated with a relativistic Hartree–Fock approach including core-polarization effects and configuration interaction in an extensive way. Theoretical and experimental data have been compared and the new data have also been compared with the few previous results available in the literature. [ABSTRACT FROM AUTHOR]

It has been shown that the low-frequency periodic processes in spectroscopy and chemical transformations that proceed without a change in the total energy of a complex molecular system can be explained as a result of synchronized radiationless transitions between the resonant ground states of quantum systems of a different structure. [ABSTRACT FROM AUTHOR]