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Based on the local surface plasmon resonance effect of Ag nanolayer, the luminescence enhancement in the visible light range of multilayer thin film has been investigated combined with metal/spacer molecule/photoluminescence material structure. The luminescence enhancement effect of multilayer thin films can be improved by adjusting the spin-coating number of Ag nanolayer and SiO 2 spacer in the multilayer structure. At the same time, the mechanism of enhanced luminescence has been analyzed according to the change in fluorescence lifetime. The effect of the coupling between Ag nanolayer and luminescence layer on the radiative transition rate and fluorescence quantum yield have been discussed. The up-conversion luminescence intensity of the noble metal-modified multilayer thin film can be further improved by combining the multilayer structure with sensitized layer. • The emission intensity of thin films are improved via the LSPR effect of Ag nanolayer. • On the basis of Ag@Tm/Yb structure, SiO 2 spacer layer is introduced to further enhance the upconversion luminescence. • The mechanisms of luminescence enhancement in the multilayer thin films are analyzed. • More than 20 times emission enhancement is achieved in the Ag@SiO 2 @Tm/Yb@Yb multilayer thin films. [ABSTRACT FROM AUTHOR]

Herein, a new electrochemiluminescence (ECL) biosensor was constructed with highly efficient polymerized carbon dots (PCDs) as ECL emitter and the improved localized catalytic hairpin assembly (L-CHA) as signal amplifier for ultrasensitive detection of microRNA-222 (miRNA-222). Impressively, compared to the traditional carbon dots with inefficient blue region ECL emission, PCDs with N, O co-dope and large conjugated π-system showed high electrical conductivity, narrow band gap and strong radiative transition, which could exhibit high ECL efficiency to improve the sensitivity of detection and long wavelength ECL emission to achieve deep tissue penetration for reducing biological damage. Furthermore, the trace target miRNA-222 could be efficiently converted into large amounts of output DNA labelled with the quencher dopamine (S-DA) through the L-CHA reaction to significantly enhance the target amplification efficiency for further improving the sensitivity of detection. Thus, the ECL biosensor could achieve the ultrasensitive detection of miRNA-222 from 100 aM to 100 pM with the detection limit of 76 aM. Therefore, this work proposed a novel CDs with high ECL efficiency and long wavelength ECL emission, which not only was used to build an ultrasensitive biosensor for biomolecules detection in clinical diagnosis, but also served as a potential emitter for ECL bioimaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • QY was improved without changing the fluorescence wavelength by catalysis of MnSO 4. • The C = N and pyridine N could suppress k NR , leading to the QY increasement. • Warm white LED with excellent performance was constructed by using muticolor CDs. Multicolor carbon dots (CDs) possess tremendous potential applications, especially in optoelectronic devices. However, further applications in warm white LED have been constrained due to the extremely low quantum yield (QY) of multicolor CDs. In this work, fluorescence enhancement multicolor CDs (o-CDs(cat.) (emitted yellow, Em = 550 nm, QY = 85.4 %), m-CDs(cat.) (emitted blue, Em = 440 nm, QY = 35.7 %), p-CDs(cat.) (emitted red, Em = 610 nm, QY = 73.8 %)) with almost 15 % QY improvement, without changing the fluorescence emission wavelength, was successfully achieved by introducing MnSO 4 into the reaction system. The relevant mechanism may be the catalytic effect of MnSO 4 , which leads to the increased content of C = N and pyridine N, further suppressing non radiative transitions, leading to the increasement of QY. Finally, the obtained high QY multicolor CDs were applied to warm white LED with the color coordinates (CIE) of (0.33,0.36), color rendering index (CRI) of 90, correlated color temperature (CCT) of 3473 K. Laying the foundation for the research methods and mechanisms of metal ion caused high QY of CDs. [ABSTRACT FROM AUTHOR]

An explicit realistic model featuring a supercooled phase transition, which allows us to explain the background of gravitational waves recently detected by pulsar timing arrays, is constructed. In this model the phase transition corresponds to radiative symmetry breaking (and mass generation) in a dark sector featuring a dark photon associated with the broken symmetry. The completion of the transition is ensured by a non-minimal coupling between gravity and the order parameter and fast reheating occurs thanks to a preheating phase. Finally, it is also shown that the model leads to primordial black hole production. [ABSTRACT FROM AUTHOR]

Methylene is an important astrochemical compound. Though its laboratory spectrum was analyzed in 1982, its first unambiguous detection could be feasible after more than one decade in the hot core of Orion-KL nebula and the approximate molecular cloud of the continuum source W51M through its emission line 404-313. Since then waiting of its further detection has now broken as it has been detected in W51 E, W51 M, W51 N, W49 N, W43, W75 N, DR21, and S140 star forming regions, and in W3 IRS5 through the same transition 404-313. To find potential lines of methylene, we have performed Sobolev LVG analysis of each of the ortho and para species of methylene, considering 10 rotational levels having energy up to 324 cm-1. We have found only three lines, 404-313, 505-414 and 212-303 of methylene, which may help for its detection in a cosmic object. The line 212-303 lying at the lowest energy may be more helpful in a cosmic object having low kinetic temperature. [ABSTRACT FROM AUTHOR]

In our recent papers, a non-standard quasi-molecular mechanism was suggested and applied to treat the cosmological recombination. It was assumed that, in the pre-recombination stage of evolution of the Universe, an electron combined with two neighbouring protons and created a hydrogen molecular ion, |$\mathrm{ H}_2^+$| in a highly excited state, which then descended into the lower lying state or dissociated. In this work, we implement a quantitative analysis of this quasi-molecular mechanism of recombination; namely, we elaborate the scheme of calculation for a free–bound radiative transition. We show that the quasi-molecular mechanism played a significant role in the pre-recombination and recombination stages of evolution of the early Universe, and hence must be included into the consideration of the description of a thermal history of the Universe. Together with the earlier developed treatment of bound–bound radiative transitions in |$\mathrm{ H}_2^+$|⁠ , the elaborated scheme of calculation can be used for the design of a rapid and complete cosmological recombination code. [ABSTRACT FROM AUTHOR]

In a radiative Auger process, optical decay leaves other carriers in excited states, resulting in weak red-shifted satellite peaks in the emission spectrum. The appearance of radiative Auger in the emission directly leads to the question if the process can be inverted: simultaneous photon absorption and electronic demotion. However, excitation of the radiative Auger transition has not been shown, neither on atoms nor on solid-state quantum emitters. Here, we demonstrate the optical driving of the radiative Auger transition, linking few-body Coulomb interactions and quantum optics. We perform our experiments on a trion in a semiconductor quantum dot, where the radiative Auger and the fundamental transition form a Λ-system. On driving both transitions simultaneously, we observe a reduction of the fluorescence signal by up to 70%. Our results suggest the possibility of turning resonance fluorescence on and off using radiative Auger as well as THz spectroscopy with optics close to the visible regime. Radiative Auger is a process that leads to a red-shift of the optical emission of an atom or a charged solid-state quantum emitter. Here, the authors realize the inverse process by optically driving the radiative Auger transition of a short-lived electronic state in a semiconductor quantum dot. [ABSTRACT FROM AUTHOR]

Interfacing long-lived qubits with propagating photons is a fundamental challenge in quantum technology. Cavity and circuit quantum electrodynamics (cQED) architectures rely on an off-resonant cavity, which blocks the qubit emission and enables a quantum non-demolition (QND) dispersive readout. However, no such buffer mode is necessary for controlling a large class of three-level systems that combine a metastable qubit transition with a bright cycling transition, using the electron shelving effect. Here we demonstrate shelving of a circuit atom, fluxonium, placed inside a microwave waveguide. With no cavity modes in the setup, the qubit coherence time exceeds 50 μs, and the cycling transition's radiative lifetime is under 100 ns. By detecting a homodyne fluorescence signal from the cycling transition, we implement a QND readout of the qubit and account for readout errors using a minimal optical pumping model. Our result establishes a resource-efficient (cavityless) alternative to cQED for controlling superconducting qubits. Existing schemes for coherent control and measurements in superconducting circuits rely on the coupling between superconducting qubits and cavity photons. Here the authors implement conditional fluorescence readout of a fluxonium qubit placed inside an open waveguide, with no coupling to cavity modes. [ABSTRACT FROM AUTHOR]

To experimentally identify the character of radiative transitions in trigonal Cu2BaSnS4, we conduct temperature and excitation intensity dependent photoluminescence (PL) measurements in the temperature range of 15–300 K. The low-temperature near band edge PL spectrum is interpreted as the free exciton at 2.11 eV and the bound exciton at 2.08 eV, coupled with associated phonon-assisted transitions. In the low energy region, we assign the dominant defect emission at 1.96 eV to donor–acceptor-pair recombination and the weak broad emission at 1.6 eV to the free-to-bound transition. The activation energies and temperature shift for the radiative transitions are determined and discussed. Above 90 K, the free exciton recombination becomes the dominant radiative transition, with its energy shift mainly governed by the contribution of optical phonons. [ABSTRACT FROM AUTHOR]

To examine the influence of radiative transitions on the performance of nonequilibrium seed-free argon plasma magnetohydrodynamic (MHD) generators, we developed MHD numerical simulation technique with a collisional-radiative (C-R) model, where neutral argon atoms with 45 discrete effective electronic excitation levels, singly ionized argon ions, and free electrons were considered under a two-temperature, low-magnetic Reynolds number MHD approximation. Furthermore, a so-called escape factor was implemented in the C-R model to consider the effects of radiation trapping by ground-state neutral atoms. Using the developed technique, we computed the performance characteristics of a nonequilibrium seed-free argon plasma MHD generator. The numerical results showed that the generator performance gets higher as the escape factor decreases, i.e., the optical thickness for radiative transitions to the ground state of neutral atoms increases. The numerical results also suggested that when the escape factor is $1.0\times 10^{-3}$ or less, the generator performance is almost the same as that for the escape factor of 0 corresponding to completely optical-thick plasma case for the radiative transitions to the ground state of neutral atoms. Furthermore, realistic escape factor values for resonance lines in the power generation channel were evaluated using a well-known estimation model. Consequently, the estimated values had the order of $10^{-4}$. We also showed that under such relatively optically thick plasma cases, a collisional (C) model and a widely used global ionization-recombination rate model with no explicit consideration of electronically excited-state neutral atoms can reproduce the generator performance predicted by the C-R model with relatively good accuracy. [ABSTRACT FROM AUTHOR]

Aminomethanol (NH2CH2OH) and N-Methylhydroxylamine (CH3NHOH) are isomers of each other, and have astrochemical importance. To our knowledge, they have not been analyzed so far in any terrestrial laboratory, and probably due to non-availability of accurate frequencies, they have not been searched in a cosmic object. It is well known that physical conditions in cosmic objects are very different as compared to those in our terrestrial laboratories. Therefore, these molecules may exist in the interstellar medium. For having information about the potential spectral lines of these molecules, we have obtained their rotational and centrifugal distortion constants, and electric dipole moment with the help of the GAUSSIAN software using B3LYP method, and aug-cc-pVDZ and aug-cc-pVTZ basis sets, separately. As the electric dipole moment has comparable components along all the three a, b and c axes, we have considered all the three types of radiative transitions together, and have calculated radiative transition probabilities for all the three kinds of radiative transitions. Considering a, b and c type transitions together, we have performed Sobolev LVG analysis of each molecule, where the collisional rate coefficients have been obtained using a scaling law. Considering energy levels up to 300 cm-1, we have found 181 weak MASER lines and 112 anomalous absorption transitions of NH2CH2OH, and 21 weak MASER lines and 28 anomalous absorption transitions of CH3NHOH, which may play important role for the identification of respective molecule in the ISM. [ABSTRACT FROM AUTHOR]

Results of studies by scanning electron microscopy and photoluminescence (PL) of structural features and radiative transitions of ZnO:Mg films grown by atmospheric pressure metal-organic chemical vapor deposition (APMOCVD) on silicon substrates are presented. Different ZnO:Mg microstructures from polycrystalline films with smooth morphology to columns and hexagonal rods are effectively formed in a wide temperature range 190-450 °C using two compositions of a mixture of zinc and magnesium (5 and 10 wt. %) acetylacetonates (ZnAA and MgAA, respectively) as precursors. The substrate temperatures have a drastic effect on the crystallinity and morphology of ZnO films. A column shaped ZnO microstructure is formed at a substrate temperature above 350 °C. The MgАА content in the mixture of precursors also affects the morphology of polycrystalline films. At lower substrate temperatures (200-320 °C), grown ZnO:Mg samples with MgAA content of 10 wt. % have a surface morphology characterized by enlarged grains compared to samples grown with MgAA 5 wt. %, whereas high substrate temperatures (350-450 °C) promote to form a surface morphology with rod-like structures in both cases: 5 and 10 wt. % of MgAA content. The growth rate of ZnO structures increases with increasing substrate temperatures. The PL emission spectra of samples with 10 wt. % MgAA demonstrate increased near band edge (NBE) emission and suppress defect level emission compared to samples with 5 wt. % MgAA. Therefore, we can conclude that magnesium acts as an isoelectronic impurity improving NBE PL emission due to gettering of defects. Mg also causes an increase in grain size, improving the crystalline perfection of ZnO:Mg polycrystalline films grown at low substrate temperatures, as well as helps to grow hexagonal rods at higher substrate temperatures. Thus, Mg-doped ZnO microstructures grown in the high temperature range could be an effective photocatalyst. [ABSTRACT FROM AUTHOR]

Gd2(WO4)3 and Gd2(WO4)3:0.5% Tm3+, 10% Yb3+ nanopowders have been prepared by the Pechini method and solid-state sintering. According to X-ray diffraction results, the materials prepared by the Pechini method are more uniform in phase composition. Optimal synthesis conditions were defined: t = 900°C and τ = 1 h for Gd2(WO4)3 and t = 950°C and τ = 3 h for Gd2(WO4)3:0.5% Tm3+, 10% Yb3+. The surface morphology of the materials has been studied by scanning electron microscopy. The samples prepared by solid-state sintering have been found to be highly agglomerated, and large agglomerates have been shown to persist even after ultrasonic processing. The average size of the doped and undoped nanoparticles prepared by the Pechini method has been determined to be 44.0 and 47.6 nm, respectively. Luminescence spectra of Gd2(WO4)3:0.5% Tm3+, 10% Yb3+ were measured and compared the intensities of the Tm3+1G4 → 3H6, 1G4 → 3F4, 3F1,2→3H6, and 3H4 → 3H6 radiative transitions in the materials prepared by both methods. The data obtained in this study demonstrate that the Pechini process is a preferable and promising method for the synthesis of Gd2(WO4)3 and Gd2(WO4)3:Tm3+,Yb3+ nanopowders. [ABSTRACT FROM AUTHOR]

The demonstration of the first ruby laser in 1960 led to a revolution in science and technology. The lasers have significantly influenced the development of new approaches to spectroscopy, giving previously undreamed insights into physics, chemistry, and other scientific areas. The search for new materials for light amplification is one of the fundamental subjects of modern photonics and nanotechnology. In this review, we summarize the most appealing progress in developing liquid crystalline (LC) micro and nano-lasers during the last decade, together with their applications and description of perspectives for the future. We will describe the physical background necessary to understand the operation principles of LC lasers, including a description of radiative transition phenomena and LC matter. The article will be divided into separate sections concerning different approaches of LC lasers realization, including; band edge, DFB, DBR, VECSEL, and random cavities utilization. We will also discuss how the LC phases can influence the design of laser devices. Finally, the potential applications, perspectives, and conclusions will be discussed at the end of the article. [ABSTRACT FROM AUTHOR]

Glass composition of (0.15-x)LiF–0.15NaF–0.01Al2O3–0.24SiO2–0.45B2O3–xTm2O3, in which x varies from 0.01 to 0.08, has been prepared by melt-annealing technique. The glass density values increased as thulium content increases from 2.359 to 2.735 g/cm3. The structure of glass showed the presence of trigonal BO3, O2B–F, tetrahedral BO4, O3B–F units, Si–O–Si, B–O–Si, and B–O–B linkages. The optical properties of the prepared glass were investigated. The optical absorption spectra revealed four characteristic bands in the ultraviolet and near-infrared regions for thulium ions. Judd–Ofelt parameters such as Ω2, Ω4, and Ω6 were calculated and took the order of Ω2 > Ω6 > Ω4. The radiative transition probability, branching ratio, and radiative lifetime were deduced from the Judd–Ofelt parameters. Moreover, the optical transition, refractive index, and phonon energy were calculated to show the effect of thulium content on borosilicate glass. [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]

Binary neutron star (NS) mergers have been expected to synthesize r-process elements and emit radioactively powered radiation, called kilonovae. Although r-process nucleosynthesis was confirmed by the observations of GW170817/AT2017gfo, no trace of individual elements has been identified except for strontium. In this paper, we perform systematic calculations of line strength for bound–bound transitions and radiative transfer simulations in NS merger ejecta toward element identification in kilonova spectra. We find that Sr ii triplet lines appear in the spectrum of a lanthanide-poor model, which is consistent with the absorption feature observed in GW170817/AT2017gfo. The synthetic spectrum also shows the strong Ca ii triplet lines. This is natural because Ca and Sr are coproduced in the material with relatively high electron fraction and their ions have similar atomic structures with only one s-electron in the outermost shell. The line strength, however, highly depends on the abundance distribution and temperature in the ejecta. For our lanthanide-rich model, the spectra show the features of doubly ionized heavy elements, such as Ce, Tb, and Th. Our results suggest that the line-forming region of GW170817/AT2017gfo was lanthanide-poor. We show that the Sr ii and Ca ii lines can be used as a probe of physical conditions in NS merger ejecta. Absence of the Ca ii line features in GW170817/AT2017gfo implies that the Ca/Sr ratio is <0.002 in mass fraction, which is consistent with nucleosynthesis for electron fraction ≥0.40 and entropy per nucleon (in units of Boltzmann constant) ≥25. [ABSTRACT FROM AUTHOR]

Thermal corrections to the one-photon spontaneous and induced transition probabilities for hydrogen and hydrogen-like ions are evaluated. The found thermal corrections are given by the vertex Feynman graph, where the vertex represents the thermal interaction between the bound electron and the nucleus. All derivations of thermal corrections to bound–bound transitions for an atom exposed to blackbody radiation are made in a fully relativistic approach within the framework of the adiabatic S-matrix formalism. It is found that the vertex-type radiative corrections to the transition rates can be at the level of a few percent to corresponding spontaneous rates for highly excited states in the hydrogen atom. A comprehensive analysis of the vertex-type thermal corrections for hydrogen-like atomic systems is presented. [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]

We present a new method aimed at improving the efficiency of component by component ionization modelling of intervening quasar absorption-line systems. We carry out cloud-by-cloud, multiphase modelling making use of cloudy and Bayesian methods to extract physical properties from an ensemble of absorption profiles. Here, as a demonstration of method, we focus on four weak, low-ionization absorbers at low redshift, because they are multiphase but relatively simple to constrain. We place errors on the inferred metallicities and ionization parameters for individual clouds, and show that the values differ from component to component across the absorption profile. Our method requires user input on the number of phases and relies on an optimized transition for each phase, one observed with high resolution and signal-to-noise ratio. The measured Doppler parameter of the optimized transition provides a constraint on the Doppler parameter of H  i , thus providing leverage in metallicity measurements even when hydrogen lines are saturated. We present several tests of our methodology, demonstrating that we can recover the input parameters from simulated profiles. We also consider how our model results are affected by which radiative transitions are covered by observations (for example, how many H  i transitions) and by uncertainties in the b parameters of optimized transitions. We discuss the successes and limitations of the method, and consider its potential for large statistical studies. This improved methodology will help to establish direct connections between the diverse properties derived from characterizing the absorbers and the multiple physical processes at play in the circumgalactic medium. [ABSTRACT FROM AUTHOR]

In the framework of a quasi-molecular approach, the formation of hydrogen atom in the pre-recombination period of evolution of the Universe is analysed quantitatively. Calculations in an adiabatic multilevel representation enable estimates of probabilities of radiative transitions. The quasi-molecular mechanism of recombination allows the formation of hydrogen molecular ion, |${\mathrm{ H}_2}^+$|⁠ , in its ground state. The probability of this process is comparable with the probability of the creation of atomic hydrogen. The participation of a second proton in the recombination increases the binding energy of an electron and decreases the rate of recombination of hydrogen. [ABSTRACT FROM AUTHOR]

Using known values of rotational and centrifugal distortion constants in conjunction with electric dipole moment of NH2CHO, we have calculated energies of rotational levels in the ground vibrational state, and the probabilities for radiative transitions between the levels. The radiative transition probabilities in conjunction with the scaled values of collisional rate coefficients are used in the Sobolev LVG analysis of NH2CHO. There are some strong lines. For ortho-NH2CHO, we have found one transition 110-111 showing anomalous absorption and five transitions 615-514, 717-616, 716-615, 818-717, 817-716 showing emission feature. For para-NH2CHO, six emission transitions 505-404, 606-505, 707-606, 808-707, 909-808, 100.10-909 are found. Out of these 12 transitions, three transitions, 110-111, 505-404, and 808-707, are already found in the ISM. Other relatively weaker lines are also found in the ISM. In addition to the observed lines, 9 transitions may play important role in the identification of NH2CHO in a cosmic object. [ABSTRACT FROM AUTHOR]

Cyanamide (NH2CN) has pyramidal equilibrium structure with two substates, denoted by 0+ and 0–. For each state of NH2CN, knowing rotational and centrifugal distortion constants in conjunction with electric dipole moment, energies for rotational levels and the probabilities for radiative transitions between the levels are calculated. The radiative transition probabilities in conjunction with scaled values for rate coefficients for collisional transitions between the levels are used in the Large Velocity Gradient analysis for each substate. For each substate, we have found anomalous absorption in three doublets at high temperature and weak MASER action at low temperature. We have also found emission feature in nine transitions in each substate. These transitions, along with the observed ones, may play important role for identification of NH2CN in a cosmic object. [ABSTRACT FROM AUTHOR]

In this review, we discuss several fundamental processes taking place in semiconductor nanocrystals (quantum dots (QDs)) when their electron subsystem interacts with electromagnetic (EM) radiation. The physical phenomena of light emission and EM energy transfer from a QD exciton to other electronic systems such as neighbouring nanocrystals and polarisable 3D (semi-infinite dielectric or metal) and 2D (graphene) materials are considered. In particular, emission decay and FRET rates near a plane interface between two dielectrics or a dielectric and a metal are discussed and their dependence upon relevant parameters is demonstrated. The cases of direct (II–VI) and indirect (silicon) band gap semiconductors are compared. We cover the relevant non-radiative mechanisms such as the Auger process, electron capture on dangling bonds and interaction with phonons. Some further effects, such as multiple exciton generation, are also discussed. The emphasis is on explaining the underlying physics and illustrating it with calculated and experimental results in a comprehensive, tutorial manner. [ABSTRACT FROM AUTHOR]

Context. The star-formation rates and stellar densities found in young massive clusters suggest that these stellar systems originate from gas at densities of n(H2) > 106 cm−3. Until today, however, the physical characterization of this ultra high density material remains largely unconstrained in observations. Aims. We investigate the density properties of the star-forming gas in the OMC-1 region located in the vicinity of the Orion Nebula Cluster (ONC). Methods. We mapped the molecular emission at 652 GHz in OMC-1 as part of the APEX-SEPIA660 Early Science. Results. We detect bright and extended N2H+ (J = 7–6) line emission along the entire OMC-1 region. Comparisons with previous ALMA data of the (J = 1–0) transition and radiative transfer models indicate that the line intensities observed in this N2H+ (7–6) line are produced by large mass reservoirs of gas at densities n(H2) > 107 cm−3. Conclusions. The first detection of this N2H+ (7–6) line at parsec-scales demonstrates the extreme density conditions of the star-forming gas in young massive clusters such as the ONC. Our results highlight the unique combination of sensitivity and mapping capabilities of the new SEPIA660 receiver for the study of the ISM properties at high frequencies. [ABSTRACT FROM AUTHOR]

The change in the state of sky from cloudy to cloudless (or vice versa) comprises an additional phase called "transition zone," in which the characteristics of the particle suspension lay between those corresponding to pure clouds and atmospheric aerosols. This phase, however, is usually considered, in atmospheric monitoring and modeling, as an area containing either aerosol or thin clouds. A sensitivity analysis has been performed to assess the longwave radiative effects resulting from different approximations to the transition zone for three radiation parameterizations included in the Weather Research and Forecasting Model. The parameterizations produce important differences (up to 60 W m−2) between radiative effects of optically thin layers of aerosols and clouds (as surrogates for transition zone suspensions) in the longwave region, both at the top and bottom of the atmosphere. Also, differences are greater if the suspension of particles is located at higher altitudes, but smaller in high humidity conditions. Plain Language Summary: The change in the state of sky from cloudy to cloudless (or vice versa) comprises an additional phase called "transition zone," in which the characteristics of the particle suspension lay between those corresponding to a pure cloud and those of atmospheric aerosols. This phase, however, is usually considered, in atmospheric monitoring and modeling, as an area containing either aerosol or thin clouds. This study quantifies the uncertainties that this binary assumption may introduce to the estimation of longwave radiative effects at the top and bottom of the atmosphere by using the Fu‐Liou‐Gu (FLG), NewGoddard, and Rapid Radiative Transfer Model for General Circulation Model (RRTMG) radiative parameterizations included in the Weather Research and Forecasting Model. The results show that there are important differences between optically thin clouds and aerosols in longwave region, which may cause substantial uncertainties in the radiative effects at the top and bottom of the atmosphere (up to 60 W m−2) if they are used to approximate transition zone conditions. Results are important due to the role that longwave radiation plays in the radiative balance that drives the Earth's climate. Key Points: The LW radiation parameterizations RRTMG, FLG, and NGO included in WRF‐ARW were used for idealized one‐dimensional vertical simulationsDifferent approximations to transition zone cause substantial uncertainty in the LW radiative effects at top and bottom of the atmosphereNeglecting transition zone conditions at high altitudes contributes to larger uncertainties in the total column energy budget [ABSTRACT FROM AUTHOR]

This work reports on the analysis of structural and spectroscopic properties of the fluoroindate glasses co-doped with Er3+/Ho3+. Structural analysis showed that erbium and holmium ions were modifier ions and depolymerizedof the fluoroindate glass network. The energy transfer processes between rare - earth ions in fluoroindate glasses pumped by and 980 nm laser diode have been also examined. Due to partial Er3+ → Ho3+ energy transfer and superposition of Er3+: 4I 11/2 → 4I 13/2 (2.77 μm)+ Ho3+: 5I 6 → 5I 7 (2.85 μm) radiative transitions in fluoroindate glass co-doped with 0.8ErF 3 /1.6HoF 3 , a broadening 3 μm luminescence (Δλ= 201 nm) was obtained. The overall energy transfer efficiency η ET1 + η ET2 was calculated to be 95% indicating efficient sensitization of the holmium ions by erbium. [ABSTRACT FROM AUTHOR]

Aims. Accurate atomic data for Ti II are essential for abundance analyses in astronomical objects. The aim of this work is to provide accurate and extensive results of oscillator strengths and lifetimes for Ti II. Methods. The multiconfiguration Dirac–Hartree–Fock and relativistic configuration interaction (RCI) methods, which are implemented in the general-purpose relativistic atomic structure package GRASP2018, were used in the present work. In the final RCI calculations, the transverse-photon (Breit) interaction, the vacuum polarisation, and the self-energy corrections were included. Results. Energy levels and transition data were calculated for the 99 lowest states in Ti II. Calculated excitation energies are found to be in good agreement with experimental data from the Atomic Spectra Database of the National Institute of Standards and Technology based on the study by Huldt et al. Lifetimes and transition data, for example, line strengths, weighted oscillator strengths, and transition probabilities for radiative electric dipole (E1), magnetic dipole (M1), and electric quadrupole (E2) transitions, are given and extensively compared with the results from previous calculations and measurements, when available. The present theoretical results of the oscillator strengths are, overall, in better agreement with values from the experiments than the other theoretical predictions. The computed lifetimes of the odd states are in excellent agreement with the measured lifetimes. Finally, we suggest a relabelling of the 3d2(12D)4py2D3/2o 3 d 2 (2 1 D) 4 p y 2 D 3 / 2 o $ 3d^2(^{1}_{2}D)4p\,y^2D_{3/2}^{o} $ and z2P3/2o z 2 P 3 / 2 o $ z^2P_{3/2}^{o} $ levels. [ABSTRACT FROM AUTHOR]

With the recent advent of circular polarization capabilities at the Atacama Large Millimeter/submillimeter Array (ALMA), Zeeman effect measurements of spectral lines are now possible as a means to directly probe line-of-sight magnetic fields in protoplanetary disks (PPDs). We present a modeling study that aims to guide physical interpretation of these anticipated observations. Using a fiducial density structure based on a typical ringed disk, we simulate line emission for the hyperfine components of the CN J = 1−0 transition with the POLARIS radiative transfer code. Since the expected magnetic field and typical CN distribution in PPDs remain largely unconstrained, we produce models with several different configurations. Corresponding integrated Stokes I and V profiles and 0.4 km s−1 resolution, 1″ beam convolved channel maps are presented. We demonstrate that the emission signatures from toroidally dominated magnetic fields are distinguishable from vertically dominated magnetic field based on channel map morphology. Due to line-of-sight and beam cancellation effects, disks with toroidal -field configurations result in significantly diminished Stokes V emission. Complex magnetic fields therefore render the traditionally used method for inferring line-of-sight magnetic field strengths (i.e., fitting the derivative of the Stokes I to the Stokes V profile) ambiguous, since a given intrinsic field strength can yield a variety of Stokes V amplitudes depending on the magnetic field geometry. In addition, gas gaps can create structure in the integrated Stokes V profile that might mimic magnetic substructure. This method should therefore be applied with caution in PPD environments and can only confidently be used as a measure of magnetic field strength if the disk's magnetic field configuration is well understood. [ABSTRACT FROM AUTHOR]

We model the (v′ = 1, v″ = 0) band of the Birge–Hopfield I band system of molecular nitrogen, N2, i.e. , emitted by nonthermal gas discharges in low pressure air. In particular, we calculate the rate of electron impact excitation of N2, which is thermally equilibrated at room temperature, to rotational levels J′ < 31 of N2(b1Πu, v′ = 1, J′). Subsequently, we calculate the intensity of emission lines resulting from radiative transitions from the aforementioned rotational levels to. Predissociation is the only nonradiative channel considered for the decay of N2(b1Πu, v′ = 1, J′) levels. [ABSTRACT FROM AUTHOR]

Si quantum dots (QDs) have a significant improvement in luminous efficiency compared with bulk Si, achieved by alleviating the forbiddance of no-phonon Γ–Γ radiative transition determined by the law of momentum conservation. Two divergent mechanisms have been proposed to account for the breakdown of momentum conservation in Si QDs, one is due to the space-confinement-induced spread of k -space wave functions associated with Heisenberg uncertainty principle Δr · Δk > 1/2, and the other is due to the interface-effect-induced intervalley mixing between indirect and direct bandgap states. Both mechanisms could cause a small overlap of the electron and hole wave functions in k -space and make vertical transitions allowed, which leads to the zero-phonon light emission. In this work, we unravel the hierarchical relationship between these two primary mechanisms in the process of zero-phonon light emission from indirect bandgap QDs, by performing semiempirical pseudopotential calculation including many-body interaction on the room-temperature luminescent properties of a series of Si, Ge, and Ge/Si core/shell QDs. We show that the space confinement mechanism is dominant in both Si and Ge indirect bandgap QDs, and the interface-induced intervalley coupling mechanism plays a minor role. While in Ge/Si core/shell QDs, the interface-induced intervalley coupling mechanism has a more pronounced contribution to enhanced light emission, implying one can further enhance light emission via engineering interface based on the intervalley coupling mechanism. Given this, we further engineer the Ge QD interface by bringing four motifs of Si/Ge multiple layers from previously inverse designed Si/Ge superlattices and core/shell nanowires for light emitters. We show that two out of four motifs always give rise to two orders of magnitude enhancement in light emission relative to the Ge and Si QDs. We demonstrate that the interface engineering can enhance light emission in indirect bandgap QDs substantially and regulate the intervalley coupling mechanism as the primary factor over the space confinement mechanism in breaking the momentum conservation law. [ABSTRACT FROM AUTHOR]

In this work, we report a list of 91 strong Th  ii spectral lines in the visible wavelength region that could be used as cosmochronometers in future investigations to determine stellar ages from thorium radioactive decay. This list was established on the basis of a pseudo-relativistic Hartree–Fock model including core-polarization corrections (HFR+CPOL) allowing us to compute the corresponding radiative decay parameters, the latter being found to be in good overall agreement with the most accurate experimental data when available. Besides this semi-empirical approach, the fully relativistic ab initio multiconfiguration Dirac–Hartree–Fock (MCDHF) method was attempted, showing large discrepancies with both the present HFR+CPOL and the most recent experimental oscillator strengths, although the calculated wavelengths from theoretical energy levels agreed with observed spectral line wavelengths within 2.4  per cent. [ABSTRACT FROM AUTHOR]

We model emissions from the Carroll-Yoshino (v′ = 0, v″ = 0) band of molecular nitrogen N2, i.e. due to nonthermal gas discharges in low pressure air and N2. In particular, we calculate the rate of excitation of thermally equilibriated N2 at room temperature (i.e. 300 K) to various rotational levels J′ of. Subsequently, we calculate the intensity of 47 emission lines resulting from radiative transitions from the aforementioned rotational levels. It is assumed that predissociation is the only nonradiative channel for the decay of excited levels. [ABSTRACT FROM AUTHOR]

State selective charge transfer cross sections are calculated in Mg12+ collisions with H and He atoms at incident energies of 1.0, 3.0, and 5.0 keV amu−1 using a time-dependent lattice method. Total capture cross sections using the time-dependent lattice method are found to be larger than those previously calculated using the Landau–Zener method. Lyman line ratios are calculated using the time-dependent lattice capture cross sections and standard radiative transitions for both the H and He atoms. Lyman line probabilities are presented for both H and He. The strongest probability for both H and He is the Lyman α emission, but relatively strong probabilities for He at an incident energy of 1.0 keV amu−1 are found for Lyman β, γ, δ, and ϵ emission. [ABSTRACT FROM AUTHOR]

We calculate the masses of χ c (3 P) states with threshold corrections in a coupled-channel model. The model was recently applied to the description of the properties of χ c (2 P) and χ b (3 P) multiplets (Ferretti and Santopinto in Phys Lett B 789:550, 2019]. We also compute the open-charm strong decay widths of the χ c (3 P) states and their radiative transitions. According to our predictions, the χ c (3 P) states should be dominated by the charmonium core, but they may also show small meson-meson components. The X(4274) is interpreted as a c c ¯ χ c 1 (3 P) state. More information on the other members of the χ c (3 P) multiplet, as well as a more rigorous analysis of the X(4274)'s decay modes, are needed to provide further indications on the quark structure of the previous resonance. [ABSTRACT FROM AUTHOR]

Superdense plasmas widely exist in planetary interiors and astrophysical objects such as brown-dwarf cores and white dwarfs. How atoms behave under such extreme-density conditions is not yet well understood, even in single-species plasmas. Here, we apply thermal density functional theory to investigate the radiation spectra of superdense iron–zinc plasma mixtures at mass densities of ρ = 250 to 2000 g cm−3 and temperatures of kT = 50 to 100 eV, accessible by double-shell–target implosions. Our ab initio calculations reveal two extreme atomic-physics phenomena—firstly, an interspecies radiative transition; and, secondly, the breaking down of the dipole-selection rule for radiative transitions in isolated atoms. Our first-principles calculations predict that for superdense plasma mixtures, both interatomic radiative transitions and dipole-forbidden transitions can become comparable to the normal intra-atomic Kα-emission signal. These physics phenomena were not previously considered in detail for extreme high-density plasma mixtures at super-high energy densities. Matter at extremely high density and pressure behaves differently than at ambient conditions. Here the authors use first-principles calculations to show the existence of interspecies radiative and dipole-forbidden transitions in warm and superdense plasma mixture of iron and zinc. [ABSTRACT FROM AUTHOR]

The inner parsec of our Galaxy contains tens of Wolf–Rayet stars whose powerful outflows are constantly interacting while filling the region with hot, diffuse plasma. Theoretical models have shown that, in some cases, the collision of stellar winds can generate cold, dense material in the form of clumps. However, their formation process and properties are not well understood yet. In this work, we present, for the first time, a statistical study of the clump formation process in unstable wind collisions. We study systems with dense outflows (⁠|${\sim }10^{-5}\rm \ M_{\odot }\ yr^{-1}$|⁠), wind speeds of 500– |$1500\rm \ km\ s^{-1}$|⁠ , and stellar separations of ∼20– |$200\rm \ au$|⁠. We develop three-dimensional high-resolution hydrodynamical simulations of stellar wind collisions with the adaptive-mesh refinement grid-based code ramses. We aim at characterizing the initial properties of clumps that form through hydrodynamic instabilities, mostly via the non-linear thin-shell instability (NTSI). Our results confirm that more massive clumps are formed in systems whose winds are close to the transition between the radiative and adiabatic regimes. Increasing either the wind speed or the degree of asymmetry increases the dispersion of the clump mass and ejection speed distributions. Nevertheless, the most massive clumps are very light (∼10−3– |$10^{-2}\rm \ M_{\oplus }$|⁠), about three orders of magnitude less massive than theoretical upper limits. Applying these results to the Galactic Centre, we find that clumps formed through the NTSI should not be heavy enough either to affect the thermodynamic state of the region or to survive for long enough to fall on to the central supermassive black hole. [ABSTRACT FROM AUTHOR]

Y2O3:Er3+ translucent ceramics was fabricated with addition of La(OH)3 nanopowder as a sintering aid. The influence of La(OH)3 addition on the microstructure, transmittance and upconversion luminescence of Y2O3:Er3+ ceramics was investigated in detail. The results show that the ceramics sample with 5 mol % La(OH)3 additives exhibits finer microstructure with fewer pores and higher optical transmittance than others. It was proved that La(OH)3 additives could greatly reduce the porosity and improve the transparency of Y2O3:Er3+ ceramics. By using a 980 nm diode laser as a pumping source, the Y2O3:Er3+ ceramics gave bright visible upconversion luminescence, which was ascribed to the radiative transitions of 2H11/2,4S3/2 →4I15/2 and 4F9/2 →4I15/2 of Er3+ ions, respectively. The possible upconversion mechanism has been proposed accordingly. [ABSTRACT FROM AUTHOR]

The relationships governing variation of the photoluminescence of graphitic carbon nitride synthesized by heat treatment of melamine in a closed air medium containing oxygen in the temperature range of 10–300 K were investigated. It was shown that the concentration of oxygen in the obtained material 4–5 at.% increases with increase of temperature and decreases with increase in the duration of the synthesis process. By measurements at reduced temperatures right down to 10 K it was possible to resolve bands due to radiative recombination processes in the photoluminescence spectra of the graphitic carbon nitride. It was found that increase of the synthesis temperature from 500 to 600°C and also increase of the duration at the given temperature from 30 to 240 min shift the maximum in the photoluminescence spectrum from 2.74 eV into the region of lower energies to 2.71–2.67 eV. This is due to the bigger role of the molecular system formed by the π bonds of carbon and nitrogen atoms with sp2 hybridization and characterized by a smaller forbidden band width in the emission of light. Transitions due to recombination through oxygen-induced levels in the forbidden band of the semiconductor lead to the appearance of a "tail" in the photoluminescence spectra in the region of low energies (2.40–2.33 eV). Increase of the carbon nitride synthesis temperature to 600°C leads to a change in the structure of the energy bands and to increase of the energy of the radiative transitions as a result of increase in the degree of doping with oxygen atoms and thermal stratifi cation. [ABSTRACT FROM AUTHOR]

Authors aim to study multicomponent barium bismuth borate glasses doped with Dy3+ (1 mol%) for white light-emitting diodes (WLEDs) application. All samples, synthesized through melt-quench approach, were characterized by XRD, optical absorption, excitation, emission, and decay lifetimes. Oscillator strengths and Judd–Ofelt intensity parameters (Ω2, Ω4, Ω6) for all glasses were computed from absorption spectra and further, radiative emission transition probability (AR), branching ratio (βR), and radiative lifetime (τR) were estimated for Dy3+ ion various excited states using J–O parameters. Upon 350 nm excitation, 4I15/2 → 6H15/2 [454 nm (blue)], 4F9/2 → 6H15/2 [483 nm (blue)], 4F9/2 → 6H13/2 [575 nm (yellow)], and 4F9/2 → 6H11/2- [663 nm (red)] emission transitions were observed among which 4F9/2 → 6H13/2 transition exhibits the highest intensity. Dy3+: Li glass showed relatively higher PL intensity and quantum efficiency than Dy3+: Na and Dy3+: K samples. Calculated CIE chromaticity (x = ~ 0.35, y = ~ 0.39) coordinates (λex.: 350 nm) and CCTs (4749‒4890 K) proclaimed overall neutral white light emission from all samples, implying their suitability for WLED applications. Decay lifetimes (τexp) were determined for Dy3+: 4F9/2 → 6H13/2 transition. Additionally, stimulated emission cross-section ( σ p E ) and gain bandwidth ( σ p E × Δλeff) were calculated for respective blue and yellow emission transitions. [ABSTRACT FROM AUTHOR]

A series of glasses by melting quenching method fabricated for spectroscopic investigations of Dysprosium (Dy3+) particle ions deposited on Antimony (Sb) - Magnesium (Mg) - Strontium (Sr) Oxyfluoroborate (BSbMgfSr) glasses. The structural and optical characterizations such as XRD, UV-VIS-NIR absorption spectroscopy, photoluminescence (PL) (excitation and emission) were accomplished to study the properties of prepared glasses. The transitions from lowest energy state to an excited state in RE3+ ions were identified using optical UV-NIR absorption spectra. By the use of Judd-Ofelt theory the J-O intensity parameters Ωλ (λ = 2, 4, 6) have been evaluated utilizing the absorption spectra with the determination of experimental (fexp) and calculated (fcal) oscillator strengths. The emission of light from glass system was concluded through PL spectra (Excitation and emission) for Dy3+ion. The radiative properties resembling radiative transition probability (AR), radiative-lifetime (τR), and branching-ratio (β) of the glasses have also estimated. Stimulated emission cross-section (σse) of the glasses also calculated for the feasibility of lasing applications. Experimental lifetime (τexp) of the decay curves of the BSbMgfSrD glasses were also calculated upon excitation by suitable wavelengths of all various concentrations of the RE3+ ions. [ABSTRACT FROM AUTHOR]

Absorption, fluorescence, and phosphorescence spectra of metal complexes of 4-tert-butylphenyl-substituted tetra(1,4-diazepino)porphyrazine MPADz4Ph8′ (M = Mg, Zn; PA = porphyrazine; Dz = diazepine; Ph = phenyl; Ph′ = 4-tert-butylphenyl) were recorded in DMF at 293 and 77 K. The Q(0–0) absorption bands of MgPADz4Ph8′ and ZnPADz4Ph8′ did not show signs of splitting, i.e., corresponded to the monomeric form. Singlet–triplet gaps of 4700 cm–1 for the Mg complex and 4800 cm–1 for the Zn complex were determined from fluorescence and phosphorescence spectra. Fluorescence quantum yields and lifetimes were measured. Rate constants of S1,2 → S0 radiative transitions and total rate constants of nonradiative deactivation of the S1,2 states were determined. Internal conversion rate constants were estimated. Conformer geometries of MgPADz4Ph8 (in the 6H tautomeric form) were calculated by density functional theory in the PBE/TZVP version. The conformer of symmetry S4v (D2d) had the lowest energy. Nonplanar diazepine rings induced small but perceptible out-of-plane distortions in the central porphyrazine ring of MgPADz4Ph8. This feature correlated with the observed Stokes shifts of 400 and 350 cm–1 (at 293 K) for MgPADz4Ph8′ and ZnPADz4Ph8′ whereas the metal phthalocyanines had shifts of ~50 cm–1. Excited electronic states of MgPADz4Ph8 were calculated using INDO/Sm. The Q-state energy of 15,200 cm–1 agreed well with the observed value of 14,800 cm–1. Strong featureless absorption in the range 330–450 nm (Soret band analog) with maxima at ~25,000 and ~29,000 cm–1 was due mainly to two strong electronic transitions with calculated energies of 24,100 and 31,500 cm–1; a shoulder on the long-wavelength side of the Soret band at ~23,000 cm–1, to a transition of calculated energy 23,800 cm–1. [ABSTRACT FROM AUTHOR]

The glasses of samarium (0.1, 0.2, 0.5, 1.0, 1.5 and 2.0 mol %) doped lithium strontium borate samples were synthesized. The physical and optical properties are studied at ambient conditions and discussed in this study. XRD spectra reveals the no atomic order in structure (amorphous) present in these glasses. Infrared spectroscopic study reveals the structural units of borate viz., BO3 and BO4 group present in the matrix. Interestingly, it is found that as the rare earth concentration increases and beyond 1.5 mol % the luminescence intensity decreases due to non-bridging Sm3+ ions in the glass network. The peaks in absorption spectra are due to dipole transition from 6H5/2 to levels corresponds to (2S + 1)LJ excited states under the excitation wavelength of 402 nm. Judd–Ofelt theory applied to estimate dipole strength in terms of J–O parameters (Ω2, Ω4 and Ω6), oscillator strength (fexp and fcal), radiative transition possibility (AR), branching ratio (βR) and stimulated emission cross section (σ) of the glass samples. From Judd–Ofelt analysis the parameters obtained are shown for 1.50 mol % of Sm3+ doped lithium strontium borate (LSB) glasses studied, which were compared with other glasses. The obtained results suggest their potential candidature for using as solid state material lighting applications due their efficient orange emissions. [ABSTRACT FROM AUTHOR]

Glass samples with formula as Li2O–BaO–GdF3–SiO2:Sm2O3 were fabricated by melt quenching method. Their optical, physical and luminescence properties were studied, for their potential applications in photonic device working in visible region. The Sm3+ ions and nearby ligands bonding nature were determined from bonding parameters (δ) that in turn were calculated from LGF absorption spectra. Oscillator strength of different absorption bands and Judd–Ofelt (JO) parameters (Ωλ (λ = 2, 4, 6)) were measured. JO-parameters and refractive index have been used to valuate various radiative properties of Sm3+ ions emission transitions in prepared glasses to explore their potential application as visible lasers. Furthermore, the emission was studied by exciting the LGF glass samples with different wavelengths (λex = 275, 402 nm). The orange to red ratios at different wavelengths (λex = 275 nm and X-ray) were evaluated to measure the Sm3+-ions local disorder in the glass network. The decreasing trend in experimental decay time (τexp) with Sm3+-ion concentration increasing was observed due to energy transfer. Best fit for the prepared glass, when studied in the light of Inokuti–Hirayama model was obtained for S = 6 indicating dipole–dipole type of energy transfer. The intense visible (orange) emission, high stimulated emission cross-section (σe), branching ratios (βR), radiative transition probability (AR), and reasonable quantum efficiency were determined for transition from 4G5/2 to 6H7/2 in glass. This suggests Sm3+ doped glass shows potential use for development of devices (laser and photonic) working in visible (orange) region. [ABSTRACT FROM AUTHOR]

Glasses and glass-ceramics with nominal composition 73 TeO 2 – 4BaO– 3Bi 2 O 3 –18SrF 2 -2RE 2 O 3 (where RE = Eu, Dy) have been synthesized by conventional melt-quenching technique and subsequent heat treatment at 370 °C for 24 h in air atmosphere. Various Eu3+ to Dy3+ molar ratio have been applied to investigate luminescence properties in both glass and glass-ceramic matrices. Especially, white light emission through simultaneous excitation of Eu3+ and Dy3+ has been studied in detail. Influence of crystalline SrF 2 phase on luminescence kinetics has been determined by luminescence decay time measurements. Presence of crystalline SrF 2 phase has been confirmed by X-ray diffraction technique XRD and transmission electron microscopy TEM. X-ray photoelectron spectroscopy XPS and Fourier-transform infrared spectroscopy FTIR have been applied to get further insight into structural properties of glass and glass-ceramic materials. Color tunable white light emission has been obtained using UV excitation. Influence of the SrF 2 crystallization on luminescence properties of prepared materials have been described in detail. Moreover, luminescence properties and especially emission color dependence on the Eu3+ to Dy3+ molar ratio have been exhaustively studied. Color-tunable white light emission has been observed as a result of simultaneous radiative transition of both, Eu3+ and Dy3+ ions when applying UV excitation. Judd – Ofelt and other optical parameters have been calculated based on luminescence emission spectra. Achieved results confirm that tellurite glass-ceramics containing SrF 2 nanocrystals are good hosts for RE3+ ions and they can be considered as new phosphors for white light emitting diodes WLEDs. • Transparent oxyfluoride glass-ceramics with SrF 2 nanocrystals have been prepared. • Color-tunable white light emission has been obtained by adjusting Eu3+/Dy3+ molar ratio. • SrF 2 crystallization influence onto luminescence of Eu3+ and Dy3+ has been studied. • Judd-Ofelt parameters have been calculated using JOES application software. [ABSTRACT FROM AUTHOR]

Dazzling green emission exhibiting Tb3+ ions doped lanthanum tungstate (LWO) nanophosphors were synthesized by a facile hydrothermally assisted solid-state reaction method. The nanophosphors were determined to have an orthorhombic structure using XRD analysis. In the optimized Tb3+: LWO nanophosphor, FE-SEM revealed aggregated non-uniform nanorods. TEM, FTIR, and XPS studies were performed to examine the material properties. A predominant excitation band was recorded at 488 nm (7F 6 →5D 4) for the Tb3+ doped LWO nanophosphors, along with a moderately intense excitation band at 378 nm (7F 6 →5G 6). Ravishing green emission at 544 nm (5D 4 →7F 5) was obtained from Tb3+ ions containing LWO nanophosphors under excitation at 378 nm and 488 nm. We improved the green emission intensity by increasing the Tb3+ ion concentration up to 14 mol%, which was reduced after 14 mol% due to concentration quenching. The energy-level diagram shows the green radiative transition pathway. The CIE coordinates and color purity were computed for Tb3+: LWO nanophosphors from their emission profiles, and the evaluated coordinates were centralized in the strong green region. A high color purity of 90.1% was obtained appreciably from the optimized Tb3+: LWO nanophosphor. The lifetime of the green emission transition was systematically evaluated based on decay dynamics. The visualization of fingerprints was examined using the optimized green phosphor with an in-depth analysis of the Group-III level details. The non-cytotoxicity of Tb3+ (14 mol%): LWO nanophosphor was confirmed in normal WI-38 lung fibroblast cells. Moreover, these phosphors exhibited strong cytotoxicity against human breast cancer cells of MCF-7. From these results, the synthesized Tb3+ (14 mol%): LWO non-cytotoxic nanophosphor material is considered the best green luminescent material for latent fingerprints in forensic investigation, photonic and anticancer applications. [Display omitted] • An orthorhombic Tb3+: La 10 W 22 O 81 nanophosphor rods were synthesized. • Luminescence of Tb3+ ions was improved by increasing the concentration of Tb3+ions. • Lifetime, CIE coordinates, color purity and cytotoxicity were extensively studied. • Anticancer studies were performed systematically. • Latent finger print application was performed with optimized sample. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two coumarin-based compounds with blue and green emission were prepared. • These compounds have the potential to be used as novel dual-state emitting luminogens. • Positive solvatochromism is found in these molecules. • These molecules exhibit Aggregation-Caused Red Shifted Emission. • Rewritable data storage has been demonstrated using the DSEgen molecule. The development of dual-state organic luminogens with high emission efficiency both in solution and solid phase is still a difficult task. Dual-state emissive fluorescent materials have proven to have a much broader application in several fields. Molecular design plays a significant role in fabricating switchable as well as tunable emissions. Nonetheless, the mechanism of dual-state emission needs to be studied further. Herein, two compounds, Blue-Yellow emissive material (BYEM) and Green-Red emissive material (GREM), have been designed and synthesized for a novel class of luminogens with dual-state emission (DSEgens) properties. These compounds emit luminously in solution state as well as solid state, with Aggregation Caused Red-Shifted Emission (ACRE) emission. Close-packed molecular structure and the steric hindrance effect can reduce the intramolecular rotation solution state, which accelerates the radiative transition of the compound in the solution state. On the contrary, in the solid state, the twisted structure and intermolecular C–H⋯π interactions can indorse the J -aggregation, which leads to the high fluorescence at the solid state. Significant red shift emission at solid state has been supported by theoretical calculations. On the other hand, by combining a partly shared donor–acceptor unit based on the twisted molecule, these compounds have shown good solvatochromic behavior. Gradual redshift emission has been observed as the solvent polarity is increased. These dual state highly emissive compounds can be applied in several industrial applications as well as the biomedical field. [ABSTRACT FROM AUTHOR]

We revisited the mass spectra of the Ξcc++ baryon with positive and negative parity states using Hypercentral Constituent Quark Model Scheme with Coloumb plus screened potential. The ground state of the baryon has been determined by the LHCb experiment, and the anticipated excited state masses of the baryon have been compared with several theoretical methodologies. The transition magnetic moments of all heavy baryons Ξcc++, Ξcc+, Ωcc+, Ξbb0, Ξbb−, Ωbb−, Ξbc+, Ξbc0, Ωbc0 are also calculated and their values are −1.013 μN, 1.048 μN, 0.961 μN, −1.69 μN, 0.73 μN, 0.48 μN, −1.39 μN, 0.94 μN and 0.710 μN, respectively.