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Donor‐acceptor (D–A•) type luminescent organic radicals have received widespread attention as efficient doublet emitters. However, their generally low photoluminescence quantum efficiency (PLQE) and limited photostability restrict their various applications. Since unraveling the relationship between structure and properties of D–A• type luminescent radicals remains a challenge, here, a series of tri(2,4,6‐trichlorophenyl)methyl (TTM) radical derivatives, which differ by the location of their ring fusion sites and nature of their heteroatoms, is synthesized. The PLQE of isomers varies by ten times as a function of ring fusion sites. In particular, the PLQE of a radical undergoing ring fusion at the carbazole 3,4‐position is as high as 98.0%. Quantum‐chemical calculations show that in the case of overlapping holes and electrons, by increasing the effective distance between the D and A moieties, the radiative transition rates of the radicals increase. Also, decreasing the electronic coupling between the charge‐transfer and local‐excited states and avoiding large geometrical distortions between the ground state (D0)_and the first excited state (D1) can significantly reduce the nonradiative transition rates. This work offers a design strategy to obtain efficient and stable luminescent radicals by modifying the sites of ring fusion, which allows control of the radiative and nonradiative transition rates. [ABSTRACT FROM AUTHOR]

In purely organic room‐temperature phosphorescence (RTP) materials, fluorescence radiative transitions generally compete against inter‐system crossing (ISC) transitions to give fluorescence/phosphorescence dual emission. In order to achieve pure phosphorescence in RTP organic light‐emitting diodes (OLEDs), extended π‐conjugation is introduced into Se‐containing donors to suppress the fluorescence radiative transitions by the symmetry excited state orbitals in the introduced π–π* transitions that cancel the overlap of the orbitals, and two novel nonaromatic amine donor containing orange RTP emitters namely 2‐(benzo[c]phenoxaselenin‐10‐yl)‐4,6‐diphenyl‐1,3,5‐triazine (BPXSeDRZ) and 2‐(dibenzo[a,c]phenoxaselenin‐11‐yl)‐4,6‐diphenyl‐1,3,5‐triazine (DBPXSeDRZ) are developed, both of which exhibit efficient orange pure phosphorescence in doped films thanks to the sufficient ISC transitions. As a result, high external quantum efficiencies of 17.2% and 17.9% are respectively achieved for the orange RTP‐OLEDs based on BPXSeDRZ and DBPXSeDRZ for the first time, and they also exhibit stable pure electro‐phosphorescence spectra in a wide driving voltage. Moreover, by adopting DBPXSeDRZ as a sensitizer to harvest the triplet excitons and tetraphenyldibenzoperiflanthene as a conventional fluorescent emitter, the external quantum efficiency of the sensitized red fluorescent OLED can be elevated to 10.1%, which greatly expands the potential applications of the metal‐free phosphors in OLEDs. [ABSTRACT FROM AUTHOR]

In recent years, pure organic room‐temperature phosphorescence (RTP) with highly efficient and long‐persistent afterglow has drawn substantial awareness. Commonly, spin‐orbit coupling can be improved by introducing heavy atoms into pure‐organic molecules. However, this strategy will simultaneously increase the radiative and non‐radiative transition rate, further resulting in dramatic decreases in the excited state lifetime and afterglow duration. Here in this work, a highly symmetric bird‐like structure tetraphenylene (TeP), and its three symmetrical halogenated derivatives (TeP−F, TeP−Cl and TeP−Br) are synthesized, while their RTP properties and mechanisms are systematically investigated by both theoretical and experimental approaches. As the results, the rigid, highly twisted conformation of TeP restricts the non‐radiative processes of RTP and gives rise to the enhancement of electron‐exchange, which can contribute to the RTP radiation process. Despite the faint RTP of the bromine and chlorine‐substituted ones (TeP−Br, TeP−Cl), the fluoro‐substituted TeP−F exhibited a long phosphorescent lifetime up to 890 ms, corresponding to an extremely long RTP afterglow over 8 s, which could be incorporated into the best series of non‐heavy‐atom RTP materials reported in previous literature. [ABSTRACT FROM AUTHOR]

The electrochemiluminescence (ECL) is generally emitted via radiative transition of singlet or triplet excited state (S1 or T1). Herein, an ECL mechanism with the transitions of both S1 and T1 of black phosphorus quantum dots (BPQDs) is found, and an arginine (Arg) modification strategy is proposed to passivate the surface oxidation defects of BPQDs, which could modulate the excited states for enhancing the ECL efficiency of BPQDs. The Arg modification leads to greater spatial overlap of highest and lowest occupied molecular orbitals, and spectral shift of radiative transitions, and improves the stability of anion radical of BPQDs. To verify the application of the proposed mechanism, it is used to construct a sensitive method for conveniently evaluating the inhibiting efficiency of cyclo-arginine-glycine-aspartic acid-d-tyrosine-lysine to cell surface integrin by using Arg containing peptide modified BPQDs as signal tag. The dual excited states mediated ECL emitters provide a paradigm for adjustable ECL generation and extend the application of ECL analysis. Electrochemiluminescence is emitted via the radiative transition of a singlet or triplet excited state. Here, the authors propose an arginine modification of black phosphorus quantum dots that exhibits enhanced emission based on dual excited states. [ABSTRACT FROM AUTHOR]

Purely organic fluorescence emitters with ultrahigh exciton utilization, such as thermally‐activated delayed fluorescence (TADF) materials, are pursued as the cornerstone of the new‐generation organic light‐emitting diodes (OLEDs). However, most TADF emitters suffer from the dilemma of the aggregation‐caused fluorescence quenching effects, severely limiting their applications. Excitingly, the recently proposed aggregation‐induced delayed fluorescence (AIDF) strategy holds the potential to tackle this problem thoroughly. Here, the recently reported AIDF emitters CP‐BP‐PXZ and its halogenated counterparts, 3‐CCP‐BP‐PXZ and 3‐BCP‐BP‐PXZ, are investigated with a united theoretical and experimental insight. Based on first‐principles calculations combined with the polarizable continuum model (PCM) and the quantum mechanics/molecular mechanics (QM/MM) model, the photophysical mechanisms of these novel materials are proposed. It is found that both reverse intersystem crossing (RISC) and the subsequent radiative transition of CP‐BP‐PXZ are promoted via aggregation, owing to the increased effective RISC channels and boosted oscillator strength. Meanwhile, the unfavorable internal conversion rate is greatly slumped, ascribed to the suppressed Duschinsky rotation effect (DRE). The unique heavy‐atom effect is disclosed in 3‐CCP‐BP‐PXZ and 3‐BCP‐BP‐PXZ that the halogens act as steric blockers in crystal, rather than spin–orbit coupling enhancers. It is hoped that this work can shed new light on the designation of high‐efficient solid‐state fluorescence emitters. [ABSTRACT FROM AUTHOR]

The understanding of how radiative transition probabilities change with temperature is crucial for comprehending the relationship between fluorescence behavior and temperature. However, although various models have been proposed to explain the patterns of transition probabilities (A) with temperature changes, they lack consistency due to their derivation from distinct microscopic perspectives. In this study, the macroscopic law of the temperature-dependent A for the 4G 5/2 , 4F 9/2 , and 5D 0 energy states in YVO 4 :Re3+(Re3+=Sm3+, Dy3+ and Eu3+) was obtained. Three rare earth ions (Re3+) were identified for each with unique energy level properties conducive to validating the general rules of A. These ions share a common characteristic: in the visible spectrum, their main emissions originate from the radiative transitions from the same higher energy level (4G 5/2 in Sm3+, 4F 9/2 in Dy3+, and 5D 0 in Eu3+) to lower energy levels, respectively. The A of the main emission levels, varying with T , were obtained by fitting the fluorescence decay curves. The exponential law governing non-radiative transitions was revealed after separating the radiative transition rate (W R) from A. The macroscopic law of temperature-dependent transition probabilities of 4G 5/2 , 4F 9/2 , and 5D 0 energy states in YVO 4 :Ln3+ (Ln3+ = Sm3+, Dy3+ and Eu3+) has been found to follow the Boltzmann distribution. The results indicate that the non-radiative transitions of the main emission levels of the rare-earth ions are processes from the excited state to adjacent lower energy levels. This macroscopic pattern may serve as a foundational rule for understanding the impact of microscopic factors on A. • The macroscopic law of temperature-dependent transition probabilities of 4G 5/2 , 4F 9/2 , and 5D 0 energy states in YVO 4 :Ln3+ (Ln3+ = Sm3+, Dy3+ and Eu3+) has been found to follow the Boltzmann distribution. • The results indicate that the non-radiative transitions of the main emission levels of the rare-earth ions are processes from the excited state to adjacent lower energy levels. [ABSTRACT FROM AUTHOR]

We proposed a new molecular design strategy that the o‐carboranyl group is attached as "an innocent unit" to the remote side of luminogens to tune photophysical properties. To verify this strategy, two o‐carborane‐based compounds with asymmetric molecular geometry were designed and synthesized. Photophysical properties of o‐carborane‐based luminogens were investigated on the basis of UV‐Vis spectra, photoluminescence spectra, crystal structure analysis and theoretical calculations. The results indicate that the o‐carboranyl group has a slight effect on the energy gap between the ground state (S0) and the first excited state (S1) in the solution state but a significant effect on the energy gap between S0 and S1 in the solid state. Besides, the radiative and non‐radiative transition processes are modulated by the o‐carboranyl unit. This leads to emission quenching in the solution state but an enhanced luminous efficiency in the aggregate state with a typical aggregation‐induced emission (AIE) property. [ABSTRACT FROM AUTHOR]

Photoluminescence characteristics of Gd 2 O 3 :Bi are studied in the 4.2–800 K temperature range by the time-resolved spectroscopy methods. Purely cubic structure of Gd 2 O 3 :Bi is confirmed by XRD. The luminescence of Bi3+(S 6) and Bi3+(C 2) centers is found to arise from the electron transitions from the emitting level of the triplet excited state of Bi3+, corresponding to the 3P 1 → 1S 0 transitions of the free Bi3+ ion. Relaxation processes in the triplet excited state of Bi3+ ions do not result in the population of the lowest-energy metastable level. The absence of the radiative transitions, corresponding to the 3P 0 → 1S 0 transitions of the free Bi3+ ion, explains the short (0.3–2.0 μs) decay time of the triplet emission of Bi3+ even at 4.2 K. The conclusion is made that the fast luminescence decay cannot be caused by the mixing of the metastable and emitting levels of the triplet excited state of Bi3+ by the magnetic field created at the Bi3+ site by the magnetically ordered Gd3+ sublattice. The electron transfer and recombination processes, resulting in the appearance of the photo- and thermally stimulated electron recombination luminescence of Bi3+(S 6) and Bi3+(C 2) centers under excitation in the E exc > 4.3 eV energy region, are also discussed. The energy level positions of the Bi3+(S 6) and Bi3+(C 2) centers in the band gap of Gd 2 O 3 are estimated. [Display omitted] • Photo- and thermoluminescence and XRD are studied for Gd 2 O 3 :Bi3+ powder. • Luminescence arises only from the 3P 1.→ 1S 0 transitions of Bi3+(S 6) and Bi3+(C 2) • This explains a short (∼10−6 s) decay time of the triplet luminescence at 4.2 K. • Fast decay cannot be caused by the magnetic field created at Bi3+ site by Gd3+ sublattice. • Electron transfer processes take place under excitation of Bi3+ with E exc >4.3 eV. [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]

The Rayleigh–Ritz variational method with multiconfiguration interaction wave functions is used to calculate energies, radiative transitions and radial expectation values of the 1 s 2 2 s 2 2 p 2 3 P ground state and the 1 s 2 2 s 2 p 3 5 S , 1 D , 3 S highly excited states of C and O 2 + . Hyperfine structure parameters and magnetic coupling constants of these states are also calculated in this work. The present calculations agree well with theoretical and experimental values available in the literature. Other data not reported in the literature are expected to offer valuable benchmarks for future research. [ABSTRACT FROM AUTHOR]

Luminescence thermometry has been extensively exploited in the last decades both from the fundamental and applied point of views. The application of photoluminescent nanoparticles on the microscopic level based on rare-earth doped (RED) nanostructures is yet a challenge. Distinct underlying physical mechanisms in the RED nanomaterials have been exploited, such as intensity ratio between radiative transitions associated with thermally coupled energy levels, energy peak and lifetime of an excited state variations with the temperature. The drawbacks of such systems are the relatively low thermal sensitivity (S r), and the large temperature uncertainty. To overcome that, several research groups have been seeking new functionalized materials. The majority of the efforts have been directed towards increasing S r with record around 10%°C−1, which is, however, considered unsatisfactory. We propose the use of an automated machine learning tool to retrieve an ideal pipeline improving the response of photoluminescence thermometers. As a proof-of-concept, we used Nd3+-doped YAG nanoparticles, excited at 760 nm, and the photoluminescence spectra in the range from 860 nm to 960 nm as input parameters. In addition to the improvement in the accuracy (> 5.5 × over traditional methods), the implementation is very simple, without the requirement of any deconvolution procedure or knowledge of any underlying physical mechanism. Our findings demonstrate that this approach is resilient to natural variances across various spectral acquisitions, which may otherwise lead to an inaccurate estimation of temperature, opening the door for real-time applications. Our open-source code is designed to be accessible to individuals without programming experience. [Display omitted] • Automated machine learning selects the best model. • Best model improves the accuracy of photoluminescent thermometers (5.5x). • Photoluminescence of neodymium ions was used as a proof-of-concept. • The proposal can be extended to any photoluminescent material. • An open-source code is available to individuals without programming experience. [ABSTRACT FROM AUTHOR]

Undoped ZnS and Sm3+ doped with varying concentration of ZnS phosphor materials were synthesized via low temperature solid state reaction method. The samples were investigated for the influence of different concentrations of Sm3+ ions on their structural and spectroscopic properties. The presence of various absorption bands in UV–Vis–NIR spectra revealed the transition from ground state to different excited states of Sm3+ ions. The Judd-Ofelt (JO) analyses were evaluated to identify the structure and the bonding around the Sm3+ ions. The high value of Ω 2 intensity parameter reveals that the site symmetry is lower. The parameters such as radiative transition probabilities, radiative lifetime, branching ratio, stimulated emission cross-sections and the optical gain parameters are also evaluated. The PL spectra shows five high intensity emission bands centered at 567 nm, 590 nm, 619 nm, 641 nm and 667 nm corresponding to 4G 5/2 →6Hj (j = 5/2, 7/2,9/2, 11/2, 13/2) transitions and showed optimum for concentration at x = 0.03 in Zn (1- x) S. The quantum yield of the prepared optimal phosphor using integrating sphere method was found to be 10.08%. This indicates that the materials synthesized may be favorable for the applications of laser and other optical devices. • Hexagonal structured undoped and Sm3+ doped ZnS phosphor were prepared. • The positive value of bonding parameter reveals its covalent nature. • Judd-Ofelt analysis were performed and trend observed is Ω 2 >Ω 4 >Ω 6. • x = 0.03 in Zn (1-x) Sm x S show maximum emission with life time 1.661 ms. • The prepared phosphor could be an excellent candidate for photonic displays. [ABSTRACT FROM AUTHOR]

• Relativistic energies, oscillator strengths and the radiative transition rates of the 1 s 2 l 2 l ′3 l ′′ 5 L e,o (l = s, p; l ′ = p; l ″ = s, p, d; L = P, D) states for the Be-like ions are calculated. • The fine structure splitting values for the multiply excited quintet states are reported and discussed along with the increase of atomic number z. • The radiative transition wavelengths and lifetimes for the multiply excited quintet states are calculated and compared with experimental results. Radiative properties of 1 s 2 l 2 l ′3 l ′′ 5 L e,o (l = s, p; l ′ = p; l ″ = s, p, d; L = P, D) states are studied using multi-configuration Rayleigh–Ritz method from Z = 7 to 14. Absolute energies including mass polarization and relativistic corrections are reported for the first time. The contribution of quantum electrodynamics and nuclear field shifts to the total energy is estimated. The variation of the fine structure splitting values with the configuration structure and with the nuclear charge number Z is discussed. The oscillator strengths and the radiative transition rates are calculated using nonrelativistic wave functions. The calculated wavelengths and lifetimes are compared with the theoretical and experimental references. [ABSTRACT FROM AUTHOR]

Abstract A series of different Eu3+ ions incorporated La 2 Mo 2 O 9 phosphors exhibiting photoluminescence (PL) peaks in the red region (613 nm; 5D 0 →7F 2) were successfully synthesized by a citrate sol-gel method. Under the 351 nm excitation, the optimal doping concentration of Eu3+ ions was identified to be 25 mol% with higher PL emission intensity and further the concentration quenching mechanism was governed by electric diploe-diploe interaction. More importantly, the optimized phosphor was demonstrated high color purity while the Commission Internationale de I'Eclairage chromaticity coordinates were (0.661, 0.339). The intrinsic radiative transition lifetime for the optimized red phosphor was calculated to be 530.7 μs and the local structure environment of Eu3+ ions in the La 2 Mo 2 O 9 host matrix was also analyzed by the Judd-Ofelt theory. Moreover, a red-emitting light-emitting diode (LED) device was fabricated by combing a near-ultraviolet LED chip with the optimized red phosphor, which exhibits a dazzling red light. Based on the obtained results, the Eu3+ ions activated La 2 Mo 2 O 9 phosphors are expected to be as a promising red-emitting phosphor for solid-state lighting. Graphical abstract Image 1 Highlights • A series of La 2 Mo 2 O 9 :Eu3+ phosphors were synthesized by a facile sol-gel method. • All the samples emitted bright red emissions from the Eu3+ ions pumped by 351 nm light. • Optimized phosphors had high color purity of 96.3% while CIE values were (0.661, 0.339). • The refractive index was 2.48 while the Ω 2 and Ω 4 were obtained by Judd-Ofelt theory. [ABSTRACT FROM AUTHOR]

[Display omitted] • Regulating excited-state properties for high brightness DR/NIR fluorophores. • Both fluorophores show aggregation-induced emission performance. • The PLQY arrives to 56 % with maximal emission of 692 nm at aggregation. Deep red/Near-infrared (DR/NIR) emitters with high photoluminescent quantum yield (PLQY) in the aggregate state are still challenge for achieving highly efficient non-doped organic light emitting diodes (OLEDs). Herein, we utilize the methodology of regulating excited-state property to adjust the proportion of radiative and nonradiative transition at aggregation, three aggregation-induced emission (AIE) active emitters (TNZNp, TNZTPAN and TNZTPEDA) with diverse sum of benzene ring rotors are prepared. TNZTPEDA with more rotors suffers from fast nonradiative transition which leads to the low fluorescent efficiency in the unimolecular and aggregate levels. Oppositely, decreasing rotors to enhance obviously solid-state PLQY of TNZNp, but the radiative transition rate is still lower than the nonradiative rate. After introducing rotational electronic donor to improving locally excited-state proportion and suppress intermolecular interaction, simultaneously, TNZTPAN has the best PLQY of 56 % due to the faster radiative transition than nonradiative transition at aggregation. Three emitters are used to manufacture non-doped OLEDs, TNZTPAN shows the maximal electroluminescence peaking at 692 nm with Commission International de L'Eclairage coordinates of (0.68, 0.30), the external quantum efficiency of 3.54 % represents a higher level among the reported non-doped DR/NIR-type OLEDs. The results of this work demonstrate the feasibility of regulating excited-state property to prepare highly bright emitters, which plays important role in designing organic DR/NIR emitters with high fluorescent efficiency at aggregation in the future. [ABSTRACT FROM AUTHOR]

The transitions originating from triply excited, doubly autoionizing states of Li-like V formed in beam-foil experiments detected within a set of blended spectroscopic profiles have been assigned tentatively by the Hartree–Fock calculations including relativistic corrections and multi-configuration interactions as perturbations. The x-ray decay channels from the triply excited states such as 3p 3 4 S, 2p 2 n p 4 S ( n ∼ 12 ) through radiative transitions to the ground state via two or more steps have been observed. [ABSTRACT FROM AUTHOR]

In this study, we report a unique solution-combustion synthesis of Mn4+ doped CaYAlO 4 microcrystals and demonstrate a narrow-band deep-red emission. Through the simulation of low-temperature photoluminescence (PL) spectroscopy and theoretical fitting on temperature-dependent PL intensity at T < 400 K, we obtained a dominant phonon mode with energy of 40 meV during the vibronic coupling process, with a small Huang-Rhys factor of S = 0.68. From the analysis of the measured PL lifetime evolution of Mn4 + doped CaYAlO 4 , it is found that luminescence thermal quenching effect was mainly attributed to four-dominant phonon interaction with Mn4+ electronic states. More interestingly, the deviation of luminescence decay curve from the single-exponential mode at T > 400 K suggests that the occurrence of two radiative transitions is a consequence of ionically thermal excitation to the second excited state of 4T 2. These findings provide not only a general approach to identify the predominant phonon vibration, but also deep insights into the effect of weak electron-phonon coupling on PL properties of solid-state luminescent. • A unique approach of solution-combustion process has been employed for the synthesis of Mn4+ doped CaYAlO 4 microcrystals. • A narrow-band with FWHM of 34 nm has been achieved with deep red emission at the maximum of 710 nm. • The dominant phonon energy has been determined to be 40 meV from both experimental and theoretical calculation works. • Both radiative transition processes were revealed from luminescence dynamics at high temperature. [ABSTRACT FROM AUTHOR]

The transition dipole moments of the first eight Σ states of the LiH molecule have been calculated using ab initio approach based on the pseudopotential technique. Such transition dipole moments have been used to determine the radiative lifetimes for all vibrational levels of the first and the second excited states, A and C Σ, using accurate adiabatic potential energy curves. In addition to the bound-bound transitions, we have included the bound-free emissions probabilities. The latter was calculated exactly and using the Franck-Condon approximation and then included in the total radiative lifetime. A significant change in these lifetimes has been observed, particularly for the higher excited vibrational levels for which the approximate evaluation breaks down. The radiative lifetimes of the vibrational levels of the AΣ exited sate are in very good agreement with the few available theoretical and experimental results. However, the radiative lifetimes associated to the CΣ state are presented here for the first time. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The asymptotic normalization coefficient (ANC) is an important quantity in the calculation of radiative width amplitudes, providing limits on the radiative width. Here we present some examples showing the connection between the ANC and radiative width. In particular, the radiative width of the E1 transition l7F(l/2-, Ex = 3.104 MeV) to l7F (l/2+,Ex, = 0.495 MeV) reported by Rolfs [Nucl. Phys. A 217, 29 (1973)] is (1.2 ±0.2) x 10-2 eV. Meanwhile the ANC for the first excited state in 17F puts a lower limit on the radiative width, which is (3.4 ± 0.50) x 10-2 eV. Such a strong disagreement between the measured radiative width and the lower limit imposed by the ANC calls for a new measurement of this radiative width. Other examples are also considered. [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]

The efficient deep-blue organic emitters with satisfying National Television System Committee (NTSC) standard Commission Internationale de L'Eclairage (CIE) coordinate of (0.14, 0.08) are indispensable component for full-color organic light-emitting diodes (OLEDs) display. In this work, we designed and synthesized a novel deep-blue material TPIN with donor‒π‒acceptor (D‒π‒A) structure by utilizing triphenylamine (TPA) as donor, 1,4,5-triphenyl-1 H -imidazole (PIM) as acceptor and pyridyl as π-bridge. The pyridyl is expected to endow TPIN with multiple intra-/intermolecular hydrogen bands (H-bands) interactions which could inhibit molecular vibration and affect the radiative transition, aiming to obtain efficient deep-blue OLED with high color purity and negligible efficiency roll-off. In addition, the photophysical experiments and theoretical calculations were implemented to verify the unique hybridized excited state of TPIN. And X-ray crystallographic analysis of TPIN single-crystal indicates that there exist many C–H⋯N and C–H···π interactions in the stacking structure. The non-doped device based on TPIN exhibited good deep-blue electroluminescence (EL) performance with emission peak at 443 nm, corresponding to a CIE coordinate of (0.151, 0.080), and a maximum external quantum efficiency (EQE max) of 3.71% with negligible efficiency roll-off (EQE = 3.70% @ 1000 cd m−2). [Display omitted] • A novel D‒π‒A-type deep-blue emitter, TPIN, was designed and synthesized. • The pyridyl π-bridge endow TPIN with multiple H-bands interactions. • Non-doped OLED of TPIN exhibited deep-blue emission. • The deep-blue device have high efficiency with negligible roll-off. [ABSTRACT FROM AUTHOR]

The energy levels of the 3 d4 l ( l = 1-3) and 3 p3 d4 l ( l = 0, 1) configurations in the Kr IX ion and the probabilities of radiative transitions to the ground state from these excited states have been calculated within the relativistic perturbation theory using a zero-approximation model potential. The results are shown to be stable within this approximation. The well-known problem of anomalously low accuracy of the calculations of some higher lying singlet levels is considered. [ABSTRACT FROM AUTHOR]

The design of the active region is one of the most crucial problems to address in light emitting devices (LEDs) based on III-nitride, due to the spatial separation of carriers by the built-in polarization. Here, we studied radiative transitions in InGaN-based LEDs with various quantum well (QW) thicknesses—2.6, 6.5, 7.8, 12, and 15 nm. In the case of the thinnest QW, we observed a typical effect of screening of the built-in field manifested with a blue shift of the electroluminescence spectrum at high current densities, whereas the LEDs with 6.5 and 7.8 nm QWs exhibited extremely high blue shift at low current densities accompanied by complex spectrum with multiple optical transitions. On the other hand, LEDs with the thickest QWs showed a stable, single-peak emission throughout the whole current density range. In order to obtain insight into the physical mechanisms behind this complex behavior, we performed self-consistent Schrodinger–Poisson simulations. We show that variation in the emission spectra between the samples is related to changes in the carrier density and differences in the magnitude of screening of the built-in field inside QWs. Moreover, we show that the excited states play a major role in carrier recombination for all QWs, apart from the thinnest one. [ABSTRACT FROM AUTHOR]

We investigated the electronic states and nonradiative transitions among the relaxed excited states of Au− centers in RbCl crystals. To this end, we measured the temperature dependences of the luminescence intensities and decay time constants of the A′, B′, and C′ luminescence bands, which are attributed to the radiative transitions from the relaxed excited states of Au− centers. The intensities and decay time constants of these luminescence bands change with temperature, through the thermally activated nonradiative transitions among the relaxed excited states. The temperature dependences of the luminescence intensities and decay time constants were analyzed utilizing rate equations, except the decay time constant of the C′ luminescence. From the best fitting results, the activation energies of the relaxed excited states are estimated. The C′ luminescence has a longer decay time constant than that expected from the dipole-allowed transition. The temperature dependence of the decay time of the C' luminescence is discussed by considering a trapped level. • Luminescence properties of the A′, B′, and C′ bands in RbCl:Au− were investigated. • The decay profiles of these luminescence bands exhibit a single-exponential profile. • Temperature dependences of the luminescence intensities and decay time constants were analyzed by rate equations. • The 3E u and 3T 2u states are largely split in energy by a cubic crystal field. [ABSTRACT FROM AUTHOR]

A dual tunable visible (reddish, orangish, blueish and white emission) and near infrared energy conversion in Pr3+-doped yttrium tantalate prepared by sol-gel method were observed depending on the ratio of radiative transitions from the 3P 0 and 1D 2 excited states. The Pr3+ concentration influences the crystallization process of cubic Y 3 TaO 7 and monoclinic M'-YTaO 4 crystalline phases as attested by X-ray diffraction and Raman spectroscopy. Increasing the lanthanide concentration, the Y 3 TaO 7 crystalline phase is stabilized, delaying the formation of the M'-YTaO 4 one. Spectroscopic studies revealed a pronounced near-infrared (NIR) emission of Pr3+ ions, ascribed to 1D 2 →3F 3,4 transition, under ultraviolet (UV) and visible excitation. Changes in the emission profile were also noticed and could be correlated with the crystalline structure. A reduced multiphonon relaxation from the 3P 0 to the 1D 2 was observed due to the low phonon energy of the host. An intense blue emission (3P 0 →3H 4) was detected, which is increased in comparison to the red emission, for higher dopant concentration. Samples containing the highest Pr3+ concentration (5.0 mol %) exhibited a luminescence quenching on the visible and NIR transitions from the 1D 2 level indicating the influence of a cross-relaxation process on depopulating the 1D 2 level and tuning the color emission. All the above-mentioned structural and luminescent properties make these yttrium tantalates potential candidates for Photonic applications, especially as red-orange-white-blue light emitters and as energy converters for the enhancement of commercial Si solar cell efficiency. [Display omitted] • Pr3+-doped yttrium tantalate polymorphs exhibiting low phonon energy. • Wide emission color tunelability from orange/red to blue/white. • The Pr3+ concentration influences the radiative transitions from 3P 0 and 1D 2 excited states. • A UV-Vis to near infrared energy conversion leads to an intense 1.0 µm NIR emission. [ABSTRACT FROM AUTHOR]

• Brief description of the electron- Mo XXXIV collision models and photoionization of Mo XXXIII. • Bound target states description, level energies, and the radiative transition probabilities between them. • Comprehensive set of level specific photoionization cross sections of Mo XXXIII computed using the B reit- P auli R -matrix method and some important characteristic features of these cross sections. • Channel coupling effects are illustrated throughout the energy ranges considered, in particular via new structure of resonances associated with 1s22s2p6 target states. • Calculation covers a large photon energy range for each symmetry with 19500 energies up to 212.33 Ryd above the first ionization threshold, 1s22s22p5 2Po 3/2. Within the framework of Breit Pauli R -matrix approach, a close-coupling calculation has been carried out for the process of photoionization of ground and excited states of Ne-like Mo XXXIII ion. The calculation includes 60 fine-structure levels and 15 parities for the target states. Level specific photoionization cross sections are computed for all levels at a fine energy mesh of 10−5 scaled Ryd, with 19500 energies for each J π = 0± - 6± symmetry, up to 2s22p43s (2S 1/2) threshold at 212.33 Ryd above the first ionization threshold, 1s22s22p5 2 P o 3/2. In this article are presented cross sections for the photoionization of ground 1s22s22p6 1 S 0 and 1s22s22p5(2Po)3p 3 P 0 , 1s22s22p5(2Po)3p 1 S 0 , 1s22s2p63s 1 S 0 , 1s22s22p53s(3 P o 2,1,0), 1s22s22p53s (1 P o 1) excited states. To explore the role of particle-hole, channels coupling and electron-electron correlation effects on the photoionization cross sections we have compared two calculation models, namely 8-target basic configurations and 5-target basic configurations, with and without 2s2p5 3l target states included into the model. Effects are highlighted in the photoionization cross section behavior of the excited of 2s2p63s of Mo XXXIII. We believe that this is the first such calculation for this ion to obtain the photoionization cross section and results are important for the modeling and diagnostics of laboratory and astrophysical plasmas. [ABSTRACT FROM AUTHOR]

Accurate values of electric dipole (E1) amplitudes along with their uncertainties for a number of transitions among low-lying states of Mg + , Ca + , Sr + , and Ba + are listed by carrying out calculations using a relativistic all-order many-body method. By combining experimental wavelengths with these amplitudes, we quote transition probabilities, oscillator strengths and lifetimes of many short-lived excited states of the above ions. The uncertainties in these radiative properties are also quoted. We also give electric quadrupole (E2) and magnetic dipole (M1) amplitudes of the metastable states of the Ca + , Sr + , and Ba + ions by performing similar calculations. Using these calculated E1, E2 and M1 matrix elements, we have estimated the transition probabilities, oscillator strengths and lifetimes of a number of allowed and metastable states. These quantities are further compared with the values available from the other theoretical studies and experimental data in the literature. The present data will be useful for the astrophysical observations, laboratory analysis and simulations of spectral properties in the above considered alkaline-earth metal ions. [ABSTRACT FROM AUTHOR]

• The potential energies of 14 Λ-S states of HgBr are calculated by MRCI method. • The spin-orbit coupling and 5d10 correlation effects are included in the calculation. • Spectroscopic constants of bound states of HgBr are determined. • The predissociation mechanism of C2Π 1/2 of HgBr are analyzed. • Radiative lifetimes of C2Π 1/2 , D2Π 3/2 and B2Σ+ 1/2 states of HgBr are evaluated. Due to attractive candidate for the laser application and searching for the permanent electric dipole moment of the electron (eEDM), mercury bromide (HgBr) is of much interest to researchers. However, detailed information of the electronic structure of HgBr is still lacking, especially for spin-orbit interactions in excited states. In this work, high-level configuration interaction calculations of low-lying states correlating to the lowest two dissociation limits Hg(1S) + Br(2P) and Hg(3P) + Br(2P) of HgBr are carried out. In order to ensure good accuracy, the Davidson correction and spin-orbit coupling (SOC) effect are all taken into consideration in our computations. The potential energy curves (PECs) of 14 Λ-S states and 30 Ω states are determined. Based on the PECs, the spectroscopic constants of the bound states are obtained, most of which have not been reported in previous studies. The calculated SOC integrals of 22Σ+-22Π indicate a strong spin-orbit interaction, which can explain the apparent perturbations between B2Σ+ 1/2 and C2Π 1/2 found in the HgBr fluorescence excitation spectrum. Finally, to reveal more detail on transition properties of excited states, transition dipole moments of C2Π 1/2 -X2Σ+ 1/2 , D2Π 3/2 -X2Σ+ 1/2 , and B2Σ+ 1/2 -X2Σ+ 1/2 transitions and radiative lifetimes of C2Π 1/2 , D2Π 3/2 , and B2Σ+ 1/2 are determined. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Transitions from the singlet electronic excited states higher than S 1 level (S 2) to the fundamental state (S 0) are unlikely, although such transitions are observed for perylene derivative compounds. This rareness led us to investigate the role of the molecular structure of two perylene derivatives (bis(butylimido) – BuPTCD and bis(phenetylimido) – PhPTCD), as well as their supramolecular arrangements, such as molecular organization, crystallinity, and molecular aggregates (before and after thermal treatment) on the radiative transition S 2 →S 0. The emission spectra of BuPTCD and PhPTCD solutions (monomers) indicated that differences in their molecular structures (lateral groups) do not influence such transitions. Besides, it was verified that the relative intensity (RI) S 1 →S 0 over S 2 →S 0 (RI = I S 1 →S 0 /I S 2 →S 0) obtained for BuPTCD and PhPTCD PVD films increases around 15 and 1.5, respectively (in comparison to their respective solutions). However, it was surprising to observe a decrease of RI = I S 1 →S 0 /I S 2 →S 0 by a factor of 88 for both BuPTCD and PhPTCD PVD films after their thermal treatment at 200 °C for 2 h. The latter led to an increase of the emission intensity from S 2 →S 0 transition in relation to S 1 →S 0. The decrease of H aggregates, presence of J aggregates and formation of other types of molecular aggregates, induced by thermal treatment, seem to be the cause of the S 2 →S 0 emission increase, which is supported by theoretical calculations. • BuPTCD and PhPTCD present a S 2 →S 0 emission band, named anti-Kasha's fluorescence. • The relative intensity (RI) I S1 → S0 /I S2 → S0 is the same for BuPTCD and PhPTCD solutions. • In PVD film, BuPTCD and PhPTCD present distinct RI values between S 1 →S 0 and S 2 →S 0. • RI was equally decreased for BuPTCD and PhPTCD PVD films after thermal treatment. • Thermal treatment privileges J- and mixed-aggregates of BuPTCD and PhPTCD PVD films. [ABSTRACT FROM AUTHOR]

The most commonly applied luminescent thermometry (LTs) approach, which are based on the luminescence intensity ratio (LIR), requires integration of the analyzed emission bands. This analysis is often cumbersome and technically challenging due to spectral overlap and vicinity of the two emission bands. These limitations can be overcome by a new, single emission band ratiometric (SBR) approach which involves excitation through thermally induced excited state absorption (ESA) and ground state absorption (GSA). What is more, the frequent problem of low intensity of one of the radiative transitions, which are analyzed in conventional luminescent thermometry, is overcome owing to the involving of the SBR approach. Due to the opposable behavior of the emission intensity with temperature changes upon these two excitation schemes, improved thermal sensitivity can be achieved. In this work, the suitability of Nd3+-doped oxyfluorotellurite (65-x)TeO2–20ZnF2–12PbO–3Nb2O5–xNd2O3 (x = 0.1, 1, 2, 5 and 10) glasses (TZPN) was analyzed for SBR-based luminescent thermometry. To excite Nd3+ ions, the 808 nm and 1060 nm wavelengths, which are related to GSA and ESA, respectively, were involved. In the biological temperature range the relative sensitivity reached SR = 2.95%/°C. The highest value of SR = 6.15%/°C was obtained at low temperature range for the 10%Nd3+:TZPN glass LT and decreased below 1%/°C only at temperatures above 200 °C. • The excited state absorption was observed in Nd TZPN glass. • The single band ratiometric luminescent thermometer was developed based on Nd emission. • Presented luminescent thermometer is characterized by high relative sensitivity >5%/oC. [ABSTRACT FROM AUTHOR]

Spectra and decay curves of luminescence induced in a single crystal of LiTaO 3 :Pr3+ by femtosecond light pulses at different wavelengths from the UV-Blue and NIR regions were recorded and analyzed. It was found that excited levels involved in the broad UV absorption band of LiTaO 3 : Pr3+ are not able to relax via radiative transitions but they feed nonradiatively excited states of the ground Pr3+ configuration. Femtosecond pulse excitation in the NIR region results in an up-converted visible luminescence weakly affected by the pulse wavelength within the 1200 nm–1800 nm region. Spectra acquired imply that the supercontinuum (SC) generated does not promote single - or double-photon processes that may feed the 3P 0 or 1D 2 levels via transitions within the ground 4f2 configuration. It was concluded that the excitation mechanism is consistent with the multiphoton excitation (MPE) that feeds the 5d levels of Pr3+. • Conversion of femtosecond pulses into optically uniaxial system. • Down and up-conversion phenomena in LiTaO 3 :Pr3+ crystal. • Effect of supercontinuum generation on Pr3+ excited states excitation. • Ultrashort pulses induced change of electrical conductivity. [ABSTRACT FROM AUTHOR]

Presented are the results of comparative study of the decay kinetics for luminescence in the visible (350 ÷ 700 nm) and infrared (1000 ÷ 1900 nm) spectral regions, which is excited in CsI:Tl crystals by a pulsed electron beam (Е m = 250 keV, t 1/2 = 15 ns, j= 8 mJ/cm2). The infrared luminescence is assumed to be caused by radiative transition from the excited 62P 3/2 state into the ground 62P 1/2 state of Tl0 center. The decay kinetics of this luminescence at temperatures within 77 ÷ 450 К range is found to have two pronounced stages. One of them is exponential with a time constant characteristic for the given temperature and independent of Tl concentration within 0.018 ÷ 0.43 mass% range. The other stage has the same decay kinetics as that of the visible luminescence measured under the same conditions. In terms Tl0-V k recombination giving rise to Tl-perturbed excitons, the visible luminescence arise due to disintegration of [(Tl0)*,V k complexes, where Tl0 center has the populated ψ sub-level of the 62P 3/2 excited state. The exponential nature and rather long duration of the visible luminescence decay (τ = 700 ns) at room temperature are determined by the lifetime of Tl0 center in the excited metastable state. • CsI:Tl cathodoluminescence spectrum contains the fast-decaying infrared band. • Infrared luminescence is due to Tl0 center transition from the 62P 3/2 excited state. • Kinetics of Tl0-luminescence has exponential and hyperbolic decay stages. • Mono-exponential decay of Tl+-luminescence arises from excited state of Tl0 centers. [ABSTRACT FROM AUTHOR]

• The temperature dependence of Trp fluorescence lifetime in solutions was studied. • A model was suggested of Trp molecules transition from the excited state to the CTS. • Reversal transition from the CTS to the excited state of Trp is considered. • Formation of the quasi-conductive band in the system of hydrogen bonds is considered. The temperature dependence of tryptophan fluorescence lifetime in an aqueous solution, aqueous solutions of glycerol (50 and 75 %, v/v) and dimethyl sulfoxide (DMSO) (50 and 75 %), and 1 M aqueous trehalose solution was studied in the range of –170 to +20 °C. In this temperature range, the fluorescence kinetics in all samples is best approximated by three exponential terms with characteristic times τ 1 ∼ 3 ns, τ 2 ∼ 4 ns, and τ 3 ∼ 15 ns at room temperature. Temperature dependences of fluorescence lifetimes for the fastest and medium components exhibited antisymbatic (antiphase) behavior in the temperature range of –60 to 10 °C. To explain this behavior, a model was suggested that takes into account the tryptophan (Trp) molecule transition from the excited state to the state with separated charges – charge transfer state (CTS), the transitions back to the excited state, and the radiative transitions of the CTS to the ground state. Mathematically, this model is equivalent to the model that we have suggested earlier in [Gorokhov et al. (2018) Biochemistry (Moscow) , 82 , 1615–1623] to describe the transitions between different rotamer forms of tryptophan. The obtained results can be used for interpreting the experimental temperature curves of tryptophan fluorescence lifetime in proteins. [ABSTRACT FROM AUTHOR]