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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]

Abstract: In this work, L X-ray fluorescence cross sections, L sub-shell fluorescence yields and level widths and radiative vacancy transfer probabilities of L sub-shells to M i , N i and O i sub-shells were measured for the elements Ho, Lu, W, Hg and Bi. Energy dispersive X-ray fluorescence (EDXRF) technique was used to measure L X-ray photons. To obtain related parameters, we used 59.54keV gamma photons of 241Am radioactive point source. Emitted L X-ray photons from targets were collected by means of a Si(Li) detector with resolution of 180eV at 5.9keV. The present results are generally in a good agreement with theoretical calculations and the other results obtained in the literature, within their range considering experimental uncertainty. [Copyright &y& Elsevier]

Strong-luminescence YVO4:Eu nanoparticles were prepared by wet chemical reaction at 155°C. Energy transfer processes from V–O and Eu–O to Eu3+andf–ftransition of Eu3+are identified. Luminescence intensity is highest when excited through V–O charge transfer band. Also, luminescence intensity increases with heat treatment temperature up to 900°C due to increase of radiative rate. The luminescence emission intensity could be improved after covering the nanoparticles with an undoped shell. Bi-exponential decay is found. [ABSTRACT FROM PUBLISHER]

Luminescence spectra of CaPrF solid solutions are studied. It is found that, depending on the excitation energy, different kinds of emission centers appear in these spectra. An interconfigurational 4f 5d →4f luminescence is typical for single Pr ions in tetragonal sites. Data on the structure of the solid solutions show that the emission centers involved in S → 4f transitions can be attributed to Pr ions contained in clusters. [ABSTRACT FROM AUTHOR]

Abstract: Here we present the two-photon and two-gluon decay widths of the S-wave () and P-wave () charmonium and bottonium states and the radiative transition decay widths of , and systems based on Coulomb plus power form of the inter-quark potential () with exponent ν. The Schrödinger equation is solved numerically for different choices of the exponent ν. We employ the masses of different states and their radial wave functions obtained from the study to compute the two-photon and two-gluon decay widths and the E1 and M1 radiative transitions. It is found that the quarkonia mass spectra and the E1 transition can be described by the same interquark model potential of the with for and for systems, while the M1 transition (at which the spin of the system changes) and the decay rates in the annihilation channel of quarkonia are better estimated by a shallow potential with . [ABSTRACT FROM AUTHOR]

Abstract: Extensive non-relativistic variational calculations for estimating the energy values of states of two electron atoms (He, ) and and states of under weakly coupled plasma screening have been performed using explicitly correlated Hylleraas type basis. The modified energy eigenvalues of states arising from two p electrons of ion and states due to configuration of and ion in the Debye plasma environment are being reported for the first time. The effect of plasma has been incorporated through the Debye screening model. The system tends towards gradual instability and the number of bound states reduces with increasing plasma coupling strength. The wavelengths for and transitions in plasma embedded two electron atoms have also been reported. [Copyright &y& Elsevier]

Abstract: The present work investigates by electrochemical and steady-state and time-resolved spectroscopic methods a synthesized compound 5-nitro-benzo[b]thiophene-2-carboxylic acid (5NBTC), both in normal solvents and in the presence of TiO2 nanoparticles to reveal the nature of the photophysical processes involved. From the present experimental observations it is inferred that both in the ground state and the excited electronic state S1, there exists a strong binding between –COOH functionality of 5NBTC and TiO2 nanoparticles. However, the rupture of this binding in the presence of excess TiO2, as apparent from the steady-state and time-resolved spectroscopic measurements, is responsible for the increase in radiative transitions. Formations of aggregations of TiO2 nanoparticles at higher concentrations appear the cause of such rupturing. The redox potential measurements by cyclic voltammetry and theoretical computations by time-dependent density functional theory (TD-DFT) with B3LYP/6-311 G(d,p) basis function implemented in the Gaussian package confirm the electron accepting nature of 5NBTC and hence no electron transfer is possible between the organic compound and TiO2 nanoparticles. It is most likely that the interaction model between 5NBTC and TiO2 nanoparticles should be that the –COOH group of 5NBTC molecule coordinates either directly or through a hydrogen bond to the TiO2 surface. [Copyright &y& Elsevier]

Abstract: We construct the theory of carriers confined in spherical Si quantum dots with finite energy barriers for electrons and holes in the framework of Luttinger Hamiltonian for holes and taking into account the strong anisotropy of the conduction electron effective mass in Si. As a boundary condition for the electron and hole wave functions we use continuity of the wave functions and the current at the boundary of the nanocrystals. We apply this theory for the case of the SiO2 matrix surrounding Si quantum dots. We show that for experimentally relevant quantum dots energy spacings between neighbouring electron and hole levels are of the order of hundreds of meV. Therefore the relaxation of excited electrons and holes is damped. Theoretical calculations of probabilities of various radiative transitions are presented. [Copyright &y& Elsevier]

Abstract: The fluorescence behaviour of some new dyes based on the pyrazolo[3,4-b]quinoline (PQ) ring has been investigated. It was found that introduction of electron withdrawing and electron donating groups into pyrazolo[3,4-b]quinoline molecule causes an increase of the ground and excited state dipole moments but more important is introduction of the N,N-dimethylamine group directly into the pyrazolo[3,4-b]quinoline skeleton. Further introduction of the cyano groups in the peripheral phenyl rings brings about only minor changes in the transition dipole moments (absorption and fluorescence). Such compounds exhibit a CT fluorescence. The fluorescence of these compounds was investigated in terms of the radiative charge transfer transition to obtain the charge transfer parameters such as the energy gap between the charge transfer and the ground states, solvent reorganization energies and internal reorganization energy. The magnitude of these parameters was discussed in terms of a modern electron transfer theory and the parameters were used to calculate the rate constants for non-radiative CT transition. [Copyright &y& Elsevier]

K shell radiative transition probabilities and K, L2 and L3 shell/subshell fluorescence yields were measured using the Kβ/Kα intensity ratio for seven elements in the atomic number range 30≤Z≤40 (Zn, As, Se, Rb, Sr, Y and Zr). The targets were irradiated with γ photons of energy 59.5 keV from Am-241. The obtained values were compared with the theoretical values. It was observed that the present values agree with previous theoretical results. The L2 and L3 subshell fluorescence yields were the first measured for the present elements. [Copyright &y& Elsevier]

The vacancy transfer probabilities of K to L1, L2 and L3 shells were measured using a new approach. Those measuring L X-ray yields from targets excited by 59.5-keV incident photons above the K edge of elements were detected with a high-resolution Si(Li)-detector. For comparison with experimental results, using available data on radiative and radiationless transitions theoretical calculations were made. The radiative transitions of these elements were observed from the relativistic Hartree–Slater model. The radiationless transitions were observed from the Dirac–Hartree–Slater model. The measured results were found to be in good agreement with theoretical values. [Copyright &y& Elsevier]

Term energies, line strengths, transition probabilities, and transition wavelengths among the (1s2)2s22p2, 2s22p3p, 2s2p3, 2s22p3s and 2s22p3d 1,3,5 L (L = S, P, D, F) configuration states in Mg VII and Si IX are calculated by using the multiconfiguration Rayleigh-Ritz variation method and restricted variation method. The transition line strengths and transition probabilities of the electric dipole transitions are both given in length and velocity gauges. Differences between these two gauge values are discussed. The calculated atomic parameters show good agreement with the observed experimental results and other theoretical data. Furthermore, the uncertainty of each electric dipole transition line strength is estimated. For several transition parameters, uncertainties are decreased compared to the values from the National Institute of Standards and Technology Atomic Spectra Database. • Transition parameters in Mg VII and Si IX are calculated by Rayleigh-Ritz method. • Calculated transition parameters agree well with the values compiled by NISTASD. • Uncertainty for each electric dipole transition is estimated. • Several transition parameters uncertainties are decreased. [ABSTRACT FROM AUTHOR]

In the present review some basic radiative and non-radiative processes occurring with strongly confined electron-hole pairs (excitons) in silicon nanocrystals are discussed, and rates of these processes are calculated. We explore both intra-crystallite processes, such as the photon absorption or emission, Auger recombination, phonon-assisted exciton relaxation, multi-exciton generation, and inter-crystallite processes realized through the exciton migration in ensembles of nanocrystals. Dependence of the rates on a nanocrystal size is analyzed, and physical and chemical factors, such as doping with shallow donors and surface passivation, is examined from the point of view of their influence on the nanocrystal electronic structure and all the processes investigated. We consider nanocrystals in a wide range of their sizes. For small crystallites (less than ~ 2 nm in diameter), the presented results are based on the stationary and non-stationary density functional theory (DFT and TD DFT, respectively). For greater crystallites, for which some semiempirical methods, such as the envelope function approximation, tight binding model, or empirical pseudopotential, are usually employed, we discuss the results obtained within the framework of these methods. • Rates of exciton tunneling in Si crystallites are comparable with those of Auger process. • Doping with P increases the rates of radiative transitions and slows down Auger process. • Halogenation of the crystallite surface increases an efficiency of exciton generation. [ABSTRACT FROM AUTHOR]

A novel hybrid optical amplifier covering entire S- and C-bands has been proposed. A silica fiber configured with an erbium (Er)-doped cladding and a germanium-doped core was used. Amplification was achieved by stimulated Raman scattering along with the Er ions' radiative transition in a fiber. A numerical simulation has been performed to analyze the amplification characteristics. Fiber parameters such as optical loss, Er concentration, fiber length, and pump power were taken into consideration to calculate the optimum pump power and fiber length for a flat gain characteristic over the entire S- and C-bands. [ABSTRACT FROM PUBLISHER]

Developing ultralong organic phosphorescence (UOP) materials has become a growing concern. To date, it remains a formidable challenge to prolong the lifetime of ultralong phosphorescence under ambient conditions. A series of fluoro‐substituted phenylboronic acid derivatives with UOP feature under ambient conditions is reported here. The UOP lifetime of 2,4‐difluorophenylboronic acid (24FBP) crystal is up to 2.50 s, which is the longest emission lifetime among the reported single‐component pure organic phosphors. Combining the experimental and theoretical study, upon stabilization of triplet excitons by H‐aggregation, it is reasoned that rotation confinement in molecular rotors plays a critical role in prolonging the UOP lifetime. Given the feature of ultralong luminescence, 24FBP phosphor is successfully applied to anticounterfeiting. This result will pave the way toward tuning the UOP lifetime and expanding the scope of metal‐free organic phosphorescent materials with ultralong luminescence and their applications. [ABSTRACT FROM AUTHOR]