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The broad emission bump in the electromagnetic spectra observed following the detection of gravitational waves created during the kilonova event of the merging of two neutron stars in August 2017, named GW170817, has been linked to the heavy elements of lanthanides (Z = 57–71) and a new understanding of the creation of heavy elements in the r-process. The initial spectral emission bump has a wavelength range of 3000–7000 Å, thus covering the region of ultraviolet (UV) to optical (O) wavelengths, and is similar to those seen for lanthanides. Most lanthanides have a large number of closely lying energy levels, which introduce extensive sets of radiative transitions that often form broad regions of lines of significant strength. The current study explores these broad features through the photoabsorption spectroscopy of 25 lanthanide ions, Ho I-III, Er I-IV, Tm I-V, Yb I-VI, and Lu I-VII. With excitation only to a few orbitals beyond the ground configurations, we find that most of these ions cover a large number of bound levels with open 4 f orbitals and produce tens to hundreds of thousands of lines that may form one or multiple broad features in the X-ray to UV, O, and infrared (IR) regions. The spectra of 25 ions are presented, indicating the presence, shapes, and wavelength regions of these features. The accuracy of the atomic data used to interpret the merger spectra is an ongoing problem. The present study aims at providing improved atomic data for the energies and transition parameters obtained using relativistic Breit–Pauli approximation implemented in the atomic structure code SUPERSTRUCTURE and predicting possible features. The present data have been benchmarked with available experimental data for the energies, transition parameters, and Ho II spectrum. The study finds that a number of ions under the present study are possible contributors to the emission bump of GW170817. All atomic data will be made available online in the NORAD-Atomic-Data database. [ABSTRACT FROM AUTHOR]

The effect of irradiation with different doses of 4-MeV electrons on radiative recombination of nonequilibrium charge carriers in Cu(In,Ga)(S,Se)2 thin films of solar cells was studied. Near-edge photoluminescence (PL) in the energy range ~0.9–1.2 eV in nonirradiated and irradiated direct-gap Cu(In,Ga)(S,Se)2 solid solutions was caused by optical interband transitions and radiative recombination through energy levels of acceptor- and donor-type structure defects in the presence of strong potential fluctuations. PL spectra measured in the temperature range 5–300 K exhibited energy shifts of the near-edge PL band maxima and redistributions of their intensities in thin films after irradiation with different doses of electrons. The activation energies of nonradiative recombination were determined from the quenching of PL band intensities. The possible nature of structural defects in nonirradiated and electron-irradiated Cu(In,Ga)(S,Se)2 solid solutions was discussed. [ABSTRACT FROM AUTHOR]

In this study, Ho3+-doped 0.825K0.5Na0.5NbO3-0.175Sr(Yb0.5Nb0.5)O3 luminescence transparent ceramics were prepared via the traditional solid-state sintering method. The structure and optical properties of the ceramics before and after polarization were studied at 40 kV cm−1 for 0.5 h. With the increase of Ho content, the phase structure of the ceramics changed from a pseudo-cubic phase to the tripartite and the orthorhombic phases, and the light transmittance decreased. The ceramics demonstrated an up-conversion luminescence characteristic under the excitation of a 980 nm laser, and the emission wavelengths were 550 and 670 nm. The best up-conversion luminescence performance was obtained when the Ho content was 0.1%. Moreover, the polarization markedly enhanced the luminescence performance of the 0.825K0.5Na0.5NbO3-0.175Sr(Yb0.5Nb0.5)O3-0.1%Ho ceramics due to the increased possibility of energy-level radiative transition of rare-earth Ho3+ ions and reduction of the Eg value of the ceramic. [ABSTRACT FROM AUTHOR]

Photoionization (PI) of the Ti9+ ion is investigated using the Dirac R-matrix method. Multi-configuration Dirac–Fock (MCDF) calculations are performed to construct accurate target functions. Good agreement of energy levels and radiative transition rates indicate the accuracy of target functions. PI cross sections show good consistency between length and velocity forms. The results are consistent with the previous theoretical values in high-energy regions. Partial waves' contribution to the total PI cross sections are discussed for the GS and MS. Moreover, the PI cross sections are dominated by many resonance structures and affected by the channel coupling effects in the low-energy region. In addition to providing data for the Opacity Project TOPbase, the present work promotes plasma simulation and diagnosis. [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]

We report calculations of energy levels, radiative decay rates, and lifetimes for transitions among the 3s23p5, 3s3p6, and 3s23p43d configurations of Cl-like W LVIII. The general-purpose relativistic atomic structure package (GRASP) has been adopted for our calculations. Comparisons are made with the most recent results of Mohan et al. ( Can. J. Phys. 92, 177 (2014). and discrepancies in lifetimes are noted, up to four orders of magnitude in some instances. Our energy levels are estimated to be accurate to better than 0.5%, whereas results for radiative rates and lifetimes should be accurate to better than 20%. [ABSTRACT FROM AUTHOR]

We study the renormalization group effects on neutrino masses and mixing in Minimal Supersymmetric Standard Model (MSSM) by considering a μ-τ symmetric mass matrix at high energy scale giving rise to Tri-Bi-Maximal (TBM) type mixing. We outline a flavor symmetry model based on A4 symmetry giving rise to the desired neutrino mass matrix at high energy scale. We take the three neutrino mass eigenvalues at high energy scale as input parameters and compute the neutrino parameters at low energy by taking into account of renormalization group effects. We observe that the correct output values of neutrino parameters at low energy are obtained only when the input mass eigenvalues are large |m1,2,3|=0.08-0.12 eV with a very mild hierarchy of either inverted or normal type. A large inverted or normal hierarchical pattern of neutrino masses is disfavored within our framework. We also find a preference towards higher values of tan β, the ratio of vacuum expectation values (vev) of two Higgs doublets in MSSM in order to arrive at the correct low energy output. Such a model predicting large neutrino mass eigenvalues with very mild hierarchy and large tan β could have tantalizing signatures at oscillation, neutrino-less double beta decay as well as collider experiments. [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]

We investigate the reduction in the efficiency of band-edge radiative recombination in InN by two carrier recombination processes via mid-gap states: radiative recombination via deep states and nonradiative recombination (NR). Because of the small band-gap energy value and the existence of the surface electron accumulation layer, the carrier transition processes via deep states cannot be observed easily. We address this problem by using mid-infrared photoluminescence (PL) measurements, and observe an emission peak around 0.32 eV at room temperature, which we interpret as being caused by transition processes via deep-defect states. Since this emission is weaker than the band-edge emission, the dominant carrier recombination process is concluded to be NR by phonon emission. The NR rate is known to be determined by the NR defect density, carrier transport processes to NR defects, and thermal activation processes of carriers. Carrier transport and capture processes by NR defects are investigated using p-type samples for various carrier mobility values. It is concluded that the NR rate is highly affected by the carrier transport, and that the candidates for the NR defect species are point defects and complexes of acceptor nature. We have also observed the correlation between the thermal conductivity and the band-edge PL intensity. As a result, we have found that the NR rate is highly affected by the carrier transport and thermal activation processes in InN. [ABSTRACT FROM AUTHOR]

A comprehensive list of the best measured wavelengths in the In II spectrum has been compiled. Uncertainties of the wavelength measurements have been analyzed, and existing inconsistencies have been resolved. An optimized set of fine-structure energy levels that fits all observed wavelengths has been derived. Uncertainties of the energy level values have been reduced by an order of magnitude. An improved value of the ionization limit of In II has been determined by fitting quantum-defect and polarization formulas for several series of levels. Intensities of lines observed by different authors have been analyzed and converted to a uniform scale. A set of recommended values of radiative transition rates has been critically compiled, and uncertainties of these rates have been estimated. The hyperfine structure interval in the 5s 2S ground state of In III has been determined from the measurements of the 5sng and 5snh series in In II. [ABSTRACT FROM AUTHOR]

We present our recent progress on theoretical studies that involve auto-ionizing states of highly charged tungsten ions. Such auto-ionizing states have two channels for decay, which requires that both radiative and auto-ionization atomic data be calculated and combined in a detailed study of the dielectronic recombination (DR). Three atomic codes are used to produce relativistic atomic data (energy levels, radiative transition probabilities, and auto-ionization rates). These are the relativistic many-body perturbation theory (RMBPT) code, the multiconfiguration relativistic Hebrew University Lawrence Livermore atomic code (HULLAC), and the Hartree-Fock relativistic (Cowan) code. Branching ratios relative to the first threshold and intensity factors are calculated for satellite lines, and DR rate coefficients are determined for the excited states. The total DR rate coefficient is derived as a function of electron temperature, and it is shown that the contribution of the highly excited states is very important for the calculation of the total DR rates. Synthetic dielectronic satellite spectra are constructed, and the atomic properties specific to the relevant tungsten ions are highlighted. First, we will consider the results for Na-like tungsten (W63+) and Mg-like tungsten (W62+) using all three codes. Then, we move to even higher ionization states and present the results in Li-like W (W71+). For this we use the RMBPT code as well as the quasi-relativistic many-body perturbation theory (MZ) code. The inclusion of the DR process is essential for correct identification of the lines in impurity spectra and for understanding the main contributions to the total radiation losses. [ABSTRACT FROM AUTHOR]

Twenty five years ago Arakawa suggested that by confining carriers in three dimensions (in quantum dots) a temperature insensitive threshold current (Ith) could be achieved in semiconductor lasers. In this paper we discuss investigations on state-of-the-art 1.3 μm InAs/GaAs undoped and p-doped quantum dot lasers for telecommunication applications and discuss the extent to which this original hypothesis has been verified. In this study, the threshold current and its radiative component (Irad) are measured as a function of temperature and pressure. The results show that although the radiative component of the threshold current can be temperature insensitive in undoped quantum dot lasers, a strong contribution from non-radiative Auger recombination makes the threshold current highly temperature sensitive. We find that p-doped devices can have a temperature insensitive Ith over a limited range around room temperature resulting from an interplay between an increasing non-radiative Auger current and decreasing radiative current. The decrease in Irad, also observed below 200 K in undoped devices, is attributed to an improvement in the carrier transport with increasing temperature. Gain measurements show that even if p-doping is successful in reducing the effect of gain saturation, the modal net gain of p-doped devices is less than in undoped lasers due to increased non-radiative recombination and non-thermal carrier distribution. [ABSTRACT FROM AUTHOR]

• Sensitized Mn2+ luminescence is studied in lithium tetraborate. • Existence of complex luminescence centres is proposed. • Slow or ultrafast Mn2+ luminescence decays occur depending on the excitation energy. • Mechanisms for excitation transfer and luminescence decay acceleration are proposed. Sub-nanosecond luminescence of Mn2+ in Mn-, Sn/Mn-, and Cu/Mn-doped Li 2 B 4 O 7 ceramics is observed under laser excitation. Picosecond pulsed laser radiation (350–370 nm) generates the frequency-doubled radiation directly in a single microcrystal selected in a ceramic sample, with this secondary radiation falling within the impurity-induced VUV excitation bands of doped Li 2 B 4 O 7. These excitation bands are attributed to the creation of an impurity-bound intra-anionic exciton in Me i O 4 –BO 3 –Mn Li complex centres (Me i = Mn, Sn, or Cu). The exciton, in turn, interacts with a nearby Mn2+ ion due to mixing of the Mn2+ excited states with the excitonic states. Exciton annihilation involves Mn2+ energy levels as transient states and causes a sub-nanosecond radiative transition which is accelerated, being accompanied by rearrangement of the surrounding atoms. Excitation within the lower-energy bands is related to the other part of the complex luminescence centre, this is metal-to-ligand intra-anionic charge transfer, which makes an electron accessible to Mn Li , while the hole is transferred only during relaxation of the excited structure. Mn2+ radiative transitions are not forced in the latter case, and slow Mn2+ luminescence decay is observed. [ABSTRACT FROM AUTHOR]

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]

We describe a complete software package for the computation of various atomic data such as energy levels; radiative transition; collisional excitation; ionization by electron impact, photoionization, autoionization; and their inverse processes radiative recombination and dielectronic capture. The atomic theoretical background and numerical techniques associated with each process are discussed in detail. Sample applications and results are presented. PACS Nos.: 31.15.–p, 32.70.Cs, 34.80.Kw, 32.80.Fb, 32.80.Dz [ABSTRACT FROM AUTHOR]

Wavelengths, transition rates, and line strengths are calculated for the 85 possible multipole transitions between the excited 4p6 4d9 4f, 4p6 4d9 5l, 4p5 4d10 4f, and 4p5 4d10 5l states and the ground 4p6 4d10 state in Pd-like ions with the nuclear charges ranging from Z = 47 to 100. Relativistic many-body perturbation theory (RMBPT), including the Breit interaction, is used to evaluate energies and transition rates for multipole transitions in hole–particle systems. This method is based on the relativistic many-body perturbation theory, agrees with MCDF calculations in lowest order, includes all second-order correlation corrections, and includes corrections from negative energy states. The calculations start from a [Zn]4p64d10 Dirac–Fock potential. First-order perturbation theory is used to obtain intermediate-coupling coefficients, and second-order RMBPT is used to determine the matrix elements. The contributions from negative-energy states are included in the second-order multipole matrix elements. The resulting transition energies and transition rates are compared with experimental values and with results from other recent calculations. Trends of the transitions rates for the selected multipole transitions as function of Z are illustrated graphically. The Z dependence of the energy splitting for all triplet terms of the 4p64d9 4f and 4p64d9 5l configurations are shown for Z = 47–100. PACS Nos.: 31.15.Ar, 31.15.Md, 32.70.Cs, 32.30.Rj, 31.25.Jf [ABSTRACT FROM AUTHOR]

We summarize our study of a diatomic homonuclear molecule incident upon a potential barrier in one dimension [G.L. Goodvin and M.R.A. Shegelski. Phys. Rev. A, 71, 032719 (2005).]. We study various initial states for the molecule and allow transitions between vibrational states of the molecule during the process of tunneling. By applying an elegant method to solve this problem, we show that transmission resonances occur in several cases and that adding more binding energy levels for the molecule can tend to decrease the probability of tunneling. We also discuss the extension of our results to more realistic three-dimensional and experimental systems.PACS Nos.: 34.20.Cf, 03.65.Xp, 34.20.Gj, 34.50.Pi [ABSTRACT FROM AUTHOR]

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]

The computation of the radiation flux related to the Hawking temperature of a Schwarzschild black hole or another geometric background is still well-known to be fraught with a number of delicate problems. In spherical reduction, as shown by one of the present authors (Kummer) with Vassilevich, the correct black body radiation follows when two “basic components” (conformal anomaly and a “dilaton” anomaly) are used as input in the integrated energy-momentum conservation equation. The main new element in the present work is the use of a quite different method, the covariant perturbation theory of Barvinsky and Vilkovisky, to establish directly the full effective action which determines these basic components. In the derivation of Kummer and Vassilevich the computation of the dilaton anomaly implied one potentially doubtful intermediate step which can be avoided here. Moreover, the present approach also is sensitive to IR (renormalization) effects. We realize that the effective action naturally leads to expectation values in the Boulware vacuum which, making use of the conservation equation, suffice for the computation of the Hawking flux in other quantum states, in particular for the relevant Unruh state. Thus, a rather comprehensive discussion of the effects of (UVandIR) renormalization upon radiation flux and energy density is possible. [ABSTRACT FROM AUTHOR]

The potential of 1.3-μm AlGaInAs quantum-well (MQW) laser diodes for uncooled operation in high-speed optical communication systems is experimentally evaluated by characterizing the temperature dependence of key parameters such as the threshold current, transparency current density, optical gain and carrier lifetime. Detailed measurements performed in the 20°C-100°C temperature range indicate a localized T0 value of 68 K at 98°C for a device with a 208 μm ridge width and 700μm cavity length. The transparency current density is measured for temperatures from 20°C to 60°C and found to increase at a rate of 7.7 A.cm-2 · °C-1. Optical gain characterizations show that the peak model gain at threshold is independent of temperature, whereas the differential gain decreases linearly with temperature, whereas the differential gain decreases linearly with temperature at a rate of 3 × 10-4 A-1 · °C-1. The differential carrier lifetime is determined from electrical impedance measurements and found to decrease with temperature. From the measured carrier lifetime we derive the monomolecular (A), radiative (B), and nonradiative Auger (C) recombination coefficients and determine their temperature dependence in the 20°C-80°C range. Our study shows that A is temperature independent, B decreases with temperature. The experimental observations are discussed and compared with theoretical predictions and measurements performed on other material systems. [ABSTRACT FROM AUTHOR]

The absorption, emission spectra and lifetime of the 4F9/2 fluorescent level of Dy3+ in YAl3(BO3)4 crystal were investigated. Energy level structure was constructed from absorption and emission spectra recorded at 5 K. The measured oscillator strengths of the transitions between the J manifolds at 300 K were compared with those derived from the Judd–Ofelt theory. The radiative transition rates and radiative lifetimes were calculated. Although there are several transitions originating in the 4F9/2 level a major part of emission intensity is contained in the 4F9/2→6H13/2 transition. Measurement of selfquenching of the 4F9/2 luminescence provided a parameter characterizing an activator–activator interaction, which may be used to predict an optimal Dy3+ concentration. The narrow and polarization dependent emission lines, relatively long lifetime of the 4F9/2 metastable level (τ=520 μs) and its high quantum efficiency are advantageous for low threshold laser action in both CW and pulsed operation. The emission cross-section of a potential laser line at 570 nm connected with 4F9/2→6H13/2 transition was estimated. [Copyright &y& Elsevier]

The strength of radiative transitions in atoms is governed by selection rules that depend on the occupation of atomic orbitals with electrons[1]. Experiments have shown[SUP2-5] similar electron occupation of the quantized energy levels in semiconductor quantum dots -- often described as artificial atoms. But unlike real atoms, the confinement potential of quantum dots is anisotropic, and the electrons can easily couple with phonons of the material[6]. Here we report electrical pump-and-probe experiments that probe the allowed and 'forbidden' transitions between energy levels under phonon emission in quantum dots with one or two electrons (artificial hydrogen and helium atoms). The forbidden transitions are in fact allowed by higher-order processes where electrons flip their spin. We find that the relaxation time is about 200 μs for forbidden transitions, 4 to 5 orders of magnitude longer than for allowed transitions. This indicates that the spin degree of freedom is well separated from the orbital degree of freedom, and that the total spin in the quantum dots is an excellent quantum number. This is an encouraging result for potential applications of quantum dots as basic entities for spin-based quantum information storage. [ABSTRACT FROM AUTHOR]

Impurity Oxygen (O) atom is usually found in boron nitride materials. Herein, geometries, electronic, magnetic properties, and related stability of porous boron nitride (p-BN) with O defects were discussed employing first principles calculation. The phonon dispersion and cohesive energy demonstrate that the predicted p-BN with the band gap width of 3.99 ​eV is stable, and the formation energy of three O-doped systems (h-BO) is lower than other doped structures, which verified h-BO is easier to synthesize in the experiment. Furthermore, one or three O-doped p-BN exhibits magnetic moments of 1.0 μ B per cell, which will lead to highly efficient magnetic properties. Due to the multiple inductive energy levels in the electronic structure, h-BO system results in a series of radiative transition levels range from ~3.50 ​eV (~354 ​nm) to ~3.87 ​eV (~318 ​nm), which reveals that p-BN by replacing nitrogen atoms with oxygen is expected to be utilized in fabricating optical nanomaterial. h-BO is the most energetically favorable p-BN among the O doped p-BN systems we fabricated, which exhibits new electronic and optical properties, meanwhile, the optical levels in h-BO show the lowest intensity and less harm in UV band. [Display omitted] • h-BO is the most energetically favorable structure for its lowest formation energy. • O doped p-BN exhibits new magnetic and catalytic properties. • Optical levels in h-BO show the lowest intensity and less harm in UV band. • Origin of optical properties for p-BN in experiments is first interpreted. [ABSTRACT FROM AUTHOR]

The newly developed generalized density-dependent cluster model is employed to study the favored a transitions of exotic nuclei in both ground and isomeric states. We perform a systematic calculation for the ground and isomeric states of neutron-deficient isotopes ranging from Z = 67 to Z = 89. No adjustable parameter is introduced in our calculation. The theoretical a-decay half-lives are found to be in good agreement with the experimental data. This indicates that a unified description of a-decay half-lives for both ground and isomeric states is achieved by our model. [ABSTRACT FROM AUTHOR]