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Perylene diimides (PDIs) have received considerable attention as a versatile class of functional dyes owing to their flexible reaction sites and remarkable stability. Recent advances have enhanced our understanding of the fluorescence and photothermal conversion properties of PDI molecules. The interplay between radiative and nonradiative transitions controls the emission and heat generation processes in these molecules. This comprehensive overview summarizes the recent strategies for manipulating the structures of PDI molecules for fluorescence and photothermal conversion applications. Additionally, challenges and potential solutions associated with the usage of fluorescent and photothermal PDI molecules are discussed. [ABSTRACT FROM AUTHOR]

Copper nanoclusters (CuNCs) are emerging electrochemiluminescence (ECL) emitters with unique molecule‐like electronic structures, high abundance, and low cost. However, the synthesis of CuNCs with high ECL efficiency and stability in a scalable manner remains challenging. Here, we report a facile gram‐scale approach for preparing self‐assembled CuNCs (CuNCsAssy) induced by ligands with exceptionally boosted anodic ECL and stability. Compared to the disordered aggregates that are inactive in ECL, the CuNCsAssy shows a record anodic ECL efficiency for CuNCs (10 %, wavelength‐corrected, relative to Ru(bpy)3Cl2/tripropylamine). Mechanism studies revealed the unusual dual functions of ligands in simultaneously facilitating electrochemical excitation and radiative transition. Moreover, the assembly addressed the limitation of poor stability of conventional CuNCs. As a proof of concept, an ECL biosensor for alkaline phosphatase detection was successfully constructed with an ultralow limit of detection of 8.1×10−6 U/L. [ABSTRACT FROM AUTHOR]

The Si2C and SiC2 both are considered to play key role in the formation of the SiC dust grains in the atmosphere of the carbon-rich stars. The molecule of our interest Si2C has been detected in the envelope of the red supergiant star IRC+10216 first time. It is an asymmetric top molecule having electric dipole moment of 1 Debye along the b-axis of inertia. Because of zero nuclear spin of both the Carbon and Silicon atoms, it has only paratransitions. Using the given spectroscopic data (rotational and centrifugal distortion constants and electric dipole moment), for the para-Si2C, we have calculated energies of 200 lower rotational levels (having energy up to 217.8 cm-1) and the Einstein A and B coefficients for 867 radiative transitions between the levels. We have solved a set of 200 statistical equilibrium equations coupled with 867 equations of radiative transfer (Sobolev analysis), where the collisional rate coefficients are taken from a scaling law. Out of 867 radiative transitions, 13 transitions have been found showing weak MASER action, and 19 transitions showing anomalous absorption. One transition 808-717 is found to show both the MASER action as well as the anomalous absorption. These transitions in addition to the observed transitions may play important role in the identification of Si2C in the cosmic objects. [ABSTRACT FROM AUTHOR]

The amplitude T for 'free-free' processes such as bremsstrahlung or photoabsorption by an electron in the continuum in the presence of an external field, is usually written as the matrix element of the radiation operator taken between two continuum states. However, unlike the case when at least one of the states is bound, as in radiative transitions, electron capture or the photo-effect, this expression contains unphysical term, proportional to a delta function, and is not really the physical amplitude T p h y s . We first give an a priori definition of T p h y s in terms of the scattering parts of the continuum functions, which does not have this delta function term and has an obvious interpretation in terms of time-ordered diagrams. We then show that when the formal amplitude T is modified by a long-distance cutoff, the modified form T α approaches T p h y s as the cutoff is removed. The modified form may be used as the basis for calculation and approximations without the need to introduce further cutoffs at a later stage. [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]

The amplitude T for ‘free-free’ processes such as bremsstrahlung or photoabsorption by an electron in the continuum in the presence of an external field, is usually written as the matrix element of the radiation operator taken between two continuum states. However, unlike the case when at least one of the states is bound, as in radiative transitions, electron capture or the photo-effect, this expression contains unphysical term, proportional to a delta function, and is not really the physical amplitude Tphys. We first give an a priori definition of Tphys in terms of the scattering parts of the continuum functions, which does not have this delta function term and has an obvious interpretation in terms of time-ordered diagrams. We then show that when the formal amplitude T is modified by a long-distance cutoff, the modified form Tα approaches Tphys as the cutoff is removed. The modified form may be used as the basis for calculation and approximations without the need to introduce further cutoffs at a later stage.

Radiative lifetimes of 11 levels of Eu II in the energy range 34 923.43–46 029.14 cm−1 and those of six levels in the 4f65d configuration of Eu III in the range from 39 636.88 to 42 530.91 cm−1 were measured by time-resolved laser-induced fluorescence spectroscopy in laser-induced plasma. The obtained lifetimes range from 33 to 760 ns. To our knowledge, six levels for Eu II and three levels for Eu III are reported for the first time. Transition probabilities and oscillator strengths for 24 lines of Eu II and five lines of Eu III relative to the studied levels were derived by combining the obtained lifetimes with branching fractions measured in the emission spectrum of a hollow cathode lamp. [ABSTRACT FROM AUTHOR]

Highlights • Hyperfine structure and radiative transition of C-like Fe, Co and Ni are studied. • Electron correlation effect are investigated in detail. • Influences of Breit and QED effect on energies are studied. • The radiative spectra may provide theoretical support for experimental study. Abstract Energy levels, hyperfine structure and 2s-2p radiative transition processes of C-like Fe, Co and Ni are studied by performing multiconfiguration Dirac–Hartree–Fock method using the fully relativistic codes GRASP2K. Electron correlation effect on the energies, hyperfine structure constants and radiative transition rates are investigated in detail. Influences of Breit and quantum electrodynamics (QED) effect on energies are studied. Good agreements are found between the results in this work and experimental data. The radiative spectra of the excited states 1s22s2p3 and 1s22p4 of C-like Fe, Co and Ni may provide theoretical support for further experimental study. Since Fe, Co and Ni are important constituent part of experimental apparatus (such as EBIT), the data in this work have important application value for experimental application. [ABSTRACT FROM AUTHOR]

Calculations of energy levels, radiative data and lifetimes are reported for tungsten Ca-like ion (W LV) by using multi-configuration Dirac–Fock (MCDF) method. The GRASP2K package is adopted to carry out a large-scale systematic computation with a restricted active space treatment; the Breit interaction and QED effects are included in subsequent relativistic configuration interaction calculations. The energies and lifetimes of the lowest 119 levels are listed; the main leading configuration of the levels is of the ground state configuration [Ne]3s 2 3p 6 3d 2 and the first excited configuration [Ne]3s 2 3p 5 3d 3 . The wavelengths, radiative rates and oscillator strengths for relatively strong E1, E2, M1, and M2 transitions are listed. Comparisons with earlier experimental and theoretical values are made. The average relative deviations of energy levels from the NIST results and E1 transition wavelengths from the EBIT experimental results have turned to be only 0.20% and 0.13%, respectively. The other present results are in reasonable agreement with available data. These agreements confirm the reliability and accuracy of the current results. The present datasets may help us with the investigation of the electron–electron correlation effects in complex multi-electron highly charged heavy ions and of the diagnosis of tungsten impurity plasmas in fusion science. [ABSTRACT FROM AUTHOR]

Praseodymium (Pr 3+ ) doped mixed lanthanum yttrium oxyorthosilicate (LaYSiO 5 ) powder phosphors were synthesized using urea-assisted combustion method. The molar ratio of La:Y were varied in the following manner: La 2-x Y x SiO 5 ( x = 0, 0.5, 1, 1.5, 2), were x = 0 is pure La 2 SiO 5 , x = 2 is pure Y 2 SiO 5 and x = 0.5, 1, and 1.5 are the admixtures of the two compounds. The X-ray diffractometer results showed that the La 2 SiO 5 and Y 2 SiO 5 crystalized in their pure monoclinic phases, while their admixtures are both present in the same phase. The Burstein–Moss (BM) shift was used to explain the increase observed in the band gap after doping. The influence of the host crystal field on the branching ratios of the photoluminescence emission intensities of the 3 P 0 and 1 D 2 energy levels of Pr 3+ were studied. The electronic transition from the 3 P 0 transition dominated the emission spectra when x = 0, while the 1 D 2 electronic transition dominated when x = 2. The variation in the branching ratios of the 3 P 0 and 1 D 2 emission with the change in the molar ratio of La:Y could be due to 3 P 0 → 1 D 2 non-radiative transitions, which increased with the crystal field of the host as the value of x increased (i.e., as the molar ratio of Y increases). Furthermore, it was shown that the 3 P 0 emission lines emerged from Pr 3+ ions occupying La1 and Y1 sites of La 2 SiO 5 and Y 2 SiO 5 respectively, while the 1 D 2 emission lines emerged from Pr 3+ ions occupying La2 and Y2 sites. The decay curve showed three lifetime components from both 3 P 0 and 1 D 2 emission lines, with the 1 D 2 lines having higher lifetimes in all cases. [ABSTRACT FROM AUTHOR]

• Er3+/Tm3+/Ag NPs doped tellurite glass was prepared using melt-quenching method. • NIR band fluorescence in range of 1350–1650 nm with FWHM of 161 nm was obtained. • The fluorescence intensity was increased by 91% after the introduction of Ag NPs. • NIR band signal amplification of Er3+/Tm3+ doped tellurite glass fiber was simulated. The radiative property of Er3+/Tm3+ co-doping tellurite glass containing metallic silver nanoparticles (Ag NPs) in near-infrared (NIR) band region was studied under the 808 nm pumping. The tellurite glass was prepared by applying melt-quenching and heat-treated technique, and characterized by measuring differential scanning calorimeter (DSC) curve, transmission electron microscopy (TEM) image, absorption spectrum and fluorescence spectrum. Under the optimized combination of Er3+ and Tm3+ ions, a flat and wide NIR band fluorescence in spectral range of 1350 to 1650 nm with full width at half maximum (FWHM) of 161 nm, originating from Er3+:4I 13/2 →4I 15/2 radiative transition (1.53 µm) and Tm3+:3H 4 →3F 4 radiative transition (1.47 µm), was observed in the studied tellurite glass. The fluorescence intensity was increased by about 91% when the Ag NPs with size of ∼17.4 nm was embedded into the doping glass. A similar wide optical amplification spectrum was also observed through the theoretical simulation of stimulated radiative transition of tellurite glass fiber co-doped with Er3+/Tm3+ ions, indicating the potential of Er3+/Tm3+ co-doping tellurite glass applied for broadband fiber amplifiers and tunable lasers. Additionally, the DSC curve revealed the excellent thermal stability of glass host with transition temperature of 381°C and the difference between crystallization onset temperature and transition temperature of 141°C. Some important spectral parameters like radiative transition probability and fluorescence branching ratio among different levels were determined according to Judd-Ofelt theory to better understand the observed broadband and flat NIR luminescence phenomenon. [Display omitted] [ABSTRACT FROM AUTHOR]

At fusion plasma electron temperature and number density regimes of 1 × 103–1 × 107 K and 1 × 1028–1 × 1031/m3, respectively, the excited states and radiative transition of hydrogen-like ions in fusion plasmas are studied. The results show that quantum plasma model is more suitable to describe the fusion plasma than the Debye screening model. Relativistic correction to bound-state energies of the low-Z hydrogen-like ions is so small that it can be ignored.The transition probability decreases with plasma density, but the transition probabilities have the same order of magnitude in the same number density regime. [ABSTRACT FROM PUBLISHER]

Inner-shell excitation energy levels, and radiative and Auger transitions of the 1s2s22p2, 1s2s22p3p, 1s2s2p3, 1s2p4, and 1s2p33p 2,4 L ( L = S, P, D) resonances for B-like nitrogen are calculated using the saddle-point variation and saddle-point complex-rotation methods. The first-order perturbation theory is used to calculate relativistic and mass polarization corrections. Present autoionization energy levels, radiative transition rates and wavelengths, Auger rates, and Auger electron energies for these resonances agree well with theoretical and experimental data available in the literature, and will provide valuable background data for astrophysics and plasma physics in future. [ABSTRACT FROM AUTHOR]

Results of investigation of photoluminescence spectrums of the epitaxial structures containing InSb low-dimensional structures formed in GaSb matrix by a method of pulse cooling of saturated solution-melt are presented. It is shown, that observable photoluminescence bands are concerned with radiation transitions through energy levels of InSb low-dimensional structures formed on InSb wetting layer with thickness of 2 nm.

Light harvesting plays a significant role in the enhancement on photovoltaic performance. It is closely associated with the photocurrent of solar cells. It is possible to improve light harvesting by material substitution as well as expansion of absorptive edge. Therefore, upconversion characteristics is one of promising solutions for better light harvesting. Upconverting materials emit visible light which is available for photoconversion after they absorb invisible near-infrared (NIR) light. In this study, Er3+ doped Y 2 O 3 (Y 2 O 3 :Er3+) nanoparticles were used as upconverting material. Its strong emissions of green and red light corresponding to 2H 11/2 and 4S 3/2 → 4I 15/2 and 4F 9/2 → 4I 15/2 transitions were clearly demonstrated under NIR irradiation of 975 nm wavelength. These emissions were apparently absorbed by dye-sensitized electrode. Based on these results, Y 2 O 3 :Er3+ nanoparticles were introduced into dye-sensitized solar cells (DSCs). After incorporating Y 2 O 3 :Er3+ nanoparticles, photovoltage was increased due to its high band-gap energy of about 5 eV. On the other hand, the photocurrent was decreased because of the decrease in adsorbed dye amount and electron paths. However, the photoconversion edge was obviously expanded. As a result, DSC performance was enhanced with optimum upconverting particles. It exhibited an efficiency of 8.03%, which was higher than that of a conventional DSC. [ABSTRACT FROM AUTHOR]

Based on theory of rate equations, the fluorescent dynamic process of transitions between different levels in Nd 3+ :NaYF 4 transparent glass ceramic is analyzed and discussed theoretically. The radiative transition probability and non-radiative transition probability are calculated, respectively. The stationary states of rate equations are analyzed, and the populations of Nd 3+ in each energy level are proposed. The results show that the crystallization increases the population probabilities of 4 I 15/2 , 4 I 13/2 and 4 I 11/2 energy levels. Theoretical explanation is a significant complement of the experimental and practical application. [ABSTRACT FROM AUTHOR]

A comprehensive theoretical study of atomic characteristics of energy levels and transitions for the core-excited 6 S e,o (n) and 6 P e,o (n) ( n =1–5) states of the boron isoelectronic sequence ( Z =6–14) are investigated by the Rayleigh–Ritz variation method and multi-configuration interaction wavefunctions. The relativistic corrections and mass polarization effects are included by first-order perturbation theory. The configuration structures of the high-lying sextet series 6 S e,o ( n ) and 6 P e,o ( n ) ( n =1–5) of the B-like ions are assigned. The transition rates and wavelengths for the electric dipole transitions 6 S e,o (n)— 6 P o,e (n) ( n =1–5) of the B-like ions are calculated and compared with currently available theoretical and experimental data. Furthermore, the radiative transition rates and wavelengths for the important dipole transitions are discussed with the increase of nuclear charge number Z . The calculations will provide useful data for identification of spectral lines arising from the solar atmosphere and the experimental study in future work. [ABSTRACT FROM AUTHOR]

Er 3+ -doped, Er 3+ /Yb 3+ co-doped tellurite glass with and without Ag NPs were synthesized by melt-quenching method. The high resolution transmission electron microscopy (HR-TEM) and selected area electron diffractions (SAED) manifest growth of Ag NPs. The UV–vis–NIR absorption spectroscopy and fluorescence spectroscopy were measured. The optical band gap and multiphonon relaxation rate constants were calculated. The electronic band structure and local density of state (DOS) of Ag NPs are calculated. The fluorescence emission and enhancement mechanism including localized surface plasmon resonance (LSPR) and energy transfer (ET) microcosmic mechanism were discussed. The electric field distributions of Ag NPs are emulated by FDTD solutions software. Local field enhancement (LFE) induced by LSPR and lightning rod effect was found to be responsible for the fluorescence enhancement while energy transfer from Ag NPs to rare-earth was considered ignorable in the samples without photoluminescent emission. [ABSTRACT FROM AUTHOR]

Abstract: Energies, radiative and Auger transitions of the 1s vacancy resonances 1s2s 22p 2, 1s2s 22p3p, 1s2s2p 3, 1s2p 4, and 1s2p 33p, 4 L (L=S, P, D) for the neutral boron atom are calculated using the saddle-point variation and saddle-point complex-rotation methods. Large-scale wave functions are used to obtain reliable results. Relativistic and mass polarization corrections are included by the first-order perturbation theory. The calculated term energies, x-ray wavelengths, and Auger electron energies for these core-excited states are compared with available theoretical and experimental results. Auger electron energies and branching ratios are used to identify high-resolution B Auger spectrum produced in 300keV B+ on CH4 collision experiment. It is found that the Auger decay of core-excited states of the boron atom gives significant contributions to Auger spectrum in the range of 165–210eV, and many previously unknown line identifications are presented. [Copyright &y& Elsevier]