Excited Energy Levels Research Articles

Boosting characteristic emissions of lanthanide in Cs2Ag0.6Na0.4InCl6–xBrx double perovskites via mixing halide

Lanthanide ions (Ln3+) doping provides a potential strategy to control over the luminescent properties of lead-free halide double perovskite nanocrystals (DP NCs). However, due to the low energy transfer efficiency between self-trapped exciton (STE) and Ln3+ ions, the characteristic emissions of Ln3+ ions are not prominent. Furthermore, the energy transfer mechanism between STE and Ln3+ ions is also elusive and requires in-depth study. We chose trace Bi3+-doped Cs2Ag0.6Na0.4InCl6–xBrx as a representative DP matrix to demonstrate that by tuning the bromide concentration, the Ln3+ emission can be greatly enhanced. Such enhanced STE and Ln3+ ions energy transfer originates from the high covalency of Ln–Br bond, which contributes to improvement of the characteristic emission of Ln3+ ions. Furthermore, optical spectroscopy reveals that the energy transfer mechanism from DP to Eu3+ ions is different from all the other doped Ln3+ ions. The energy transfer from DP to Eu3+ ions is mostly through Eu–Br charge transfer while the other Ln3+ ions are excited by energy transfer from STE. The distinct energy transfer mechanism has resulted from the energy separation between the excited energy level of Ln3+ ions and the bottom of conduction band of DP. With increasing the energy separation, the energy transfer from STE to Ln3+ ions is less efficient because of the generation of a larger number of phonons and finally becomes impossible for Eu3+ ions. Our results provide new insight into tuning the energy transfer of Ln3+-doped DP NCs.

Efficient O-band emission from Pr3+ doped low phonon energy ZnF2-based glasses

Pr3+ doped ZnF2-based (ZnF2-BaF2-SrF2-YF3) glasses with a low phonon energy of ∼420 cm−1 are prepared by using a conventional melt-quenching method in dry N2 atmosphere. Under the excitation of a 980 nm laser diode, intense emission at ∼1310 nm is observed from the Pr3+ doped ZnF2-based glasses. The full spectral width at half maximum is 107 nm (1275–1382 nm), which is ∼7 nm wider than that of Pr3+ doped ZrF4-based glass (∼100 nm, 1279–1379 nm). The measured lifetime (∼183 μs) of the excited energy level 1G4 for Pr3+ ions in the ZnF2-based glass is also much longer than that of Pr3+ doped in ZrF4-based glass (∼110 μs). According to the theoretically calculated results, a positive gain of 31.7 dB at 1304 nm can be obtained from O-band optical amplifiers based on the Pr3+ doped ZnF2-based glass, which is 5 dB higher than that obtained from amplifiers based on Pr3+ doped ZrF4-based glass with a same pump condition. The corresponding bandwidth for a net gain of >20 dB is ∼51 nm (1277–1328 nm), and the noise figure is calculated to be < 5.8 dB in above spectral range. Our results indicate that Pr3+ doped ZnF2-based glasses have the potential for constructing efficient O-band optical amplifiers.

Pesticides luminescent sensing by a Tb3+-doped Zn metal-organic framework with selectivity towards parathion

Organophosphorus pesticides (OPPs) such as parathion have extensive uses in agriculture and household applications. Chronic exposure to these pesticides can cause severe health and environmental issues. Therefore, a current ecological concern is associated with accumulating these noxious OPPs in food and water sources. In this work, a new Tb3+-doped Zn-LMOF (Zn-LMOF= (3D) {[Zn3(1,4 benzenedicarboxylate)3(EtOH)2]·(EtOH)0.6}∞) was synthesized by a solvent-free reaction between the Zn-LMOF and the salt TbCl3·6H2O using a high-speed ball milling. The Tb@Zn-LMOF was thoroughly characterized by multiple spectroscopic tools, including Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy, and studied in-depth as a luminescent sensor for a series of pesticides (parathion, malathion, methalaxil, carbofuran, iprodione, captan and glyphosate) in aqueous methanol. The Tb@Zn-LMOF is a long-lived green-emitting compound with luminescence originated by an efficient antenna effect from the excited energy levels of Zn-LMOF toward the 5D state of Tb3+ ions, as it is displayed by its strong emission bands at 488, 545, 585, and 620 nm and a lifetime of 1.01 ms upon excitation at 290 nm. Additions of pesticides to a neutral methanolic dispersion of Tb@Zn-LMOF modified its green emission intensity with a pronounced selectivity toward parathion within the micromolar concentration range. The detection limit for parathion was calculated to be 3.04 ± 0.2 μM for Tb@Zn-LMOF. Based on 31P NMR and mass spectrometry studies, it is attributed to the release of lanthanide ions from Tb@Zn-LMOF with the simultaneous formation of a Tb3+-parathion complex.

Numerical study on the non-equilibrium characteristics of high-speed atmospheric re-entry flow and radiation of aircraft based on fully coupled model

The strong coupling interactions of non-equilibrium flow, microscopic particle collisions and radiative transitions within the shock layer of hypersonic atmospheric re-entry vehicles makes accurate prediction of the aerothermodynamics challenging. Therefore, in this study a self-consistent non-equilibrium flow, collisional–radiative reactions and radiative transfer fully coupled model are established to study the non-equilibrium characteristics of the flow field and radiation of vehicle atmospheric re-entry. The comparison of the present calculation results with flight data of FIRE II and previous results in the literature shows a reasonable agreement. The thermal, chemical and excited energy level non-equilibrium phenomena are obtained and analysed for the different FIRE II trajectory points, which form the critical basis for studying the heat transfer and radiation. The non-equilibrium distribution of excited energy levels significantly exists in the post-shock and near-wall regions due to the rapid vibrational dissociation and electronic under-excitation, as well as the wall catalytic reactions. The analysis of stagnation-point heating of FIRE II illustrates that the translational–rotational convection and the dissociation component diffusion play key roles in the aerodynamic heating of the wall region. The spectrally resolved radiative intensity in the entire flow field indicates that the vacuum ultraviolet radiation caused by the high-energy nitrogen atomic spectral lines makes the main contribution to the radiative transfer. Finally, it is found that the non-equilibrium flow–radiation coupling effect can exacerbate the excited energy level non-equilibrium, and further affect the gas radiative properties and radiative transfer. This fully coupled study provides an effective method for reasonable prediction of atmospheric re-entry flow and radiation fields.

Synthesis and luminescent properties of Eu(III)/Tb(III) rare earth complex-coated the core-shell structured silica microspheres: Unleashing the potential for white light emission

A rare earth organic complex, SiO2@ATPA-Si-RE (RE = Eu, Tb), exhibiting a core-shell structure, was synthesized using the ligand (HOOC)2C6H3NHCONH(CH2)3Si(OCH2CH3)3(ATPA-Si) to connect the silica microspheres core and coordinate with rare earth ions. The pH value of the reaction was adjusted to produce organic complex shells with thicknesses of 2.0 nm and 5.0 nm, while the SiO2 core measured a diameter of 125 nm. Luminescence spectra indicated that the emission intensity of the SiO2@ATPA-Si-RE (RE = Eu, Tb) core-shell structure was stronger than that of the ATPA-Si-RE organic complex due to a perfect match between the triplet energy level of SiO2@ATPA-Si and the excited energy level of rare earth ions (Eu3+, Tb3+). Remarkably, the core-shell structure with a 2.0 nm shell thickness possessed a greater emission intensity compared to the 5.0 nm shell thickness. Moreover, these findings unveiled the tunability of luminescence color, ranging from green or red to white, by adjusting the doping ratio of Eu3+ and Tb3+ ions and the coating thickness of complexes. Particularly, a warm white light emission, characterized by CIE coordinates (0.389, 0.347), a color rendering index value of 86.7, and a low correlated color temperature value of 3550 K, was achieved using the organic complex with a 2.0 nm thickness coated on SiO2 microspheres with a doping ratio of Eu3+ at 0.7 mmol and Tb3+ at 0.3 mmol. Conversely, the complexes with a 5.0 nm coating thickness and Tb3+ doping ratio of 0.3 mmol yielded a cold white light emission. These findings demonstrate the potential applications in next-generation lighting industry and display systems.

Electron impact fine-structure cross-section calculations of Cu and their applications in the diagnostics of laser-produced Cu-plasma through the collisional radiative model

We present the calculations of electron impact excitation cross-sections for the transitions from the ground state of Cu 3d104sS1/22 to the excited fine structure energy levels of the configurations 3d94s2,3d94s4p,3d104l,(l=p,d,f),3d105l,(l=s,p,d),3d10nl,(n=6,7;l=s,p) using the fully relativistic distorted wave theory. In addition, cross-sections for the transitions from the metastable states 3d94s2D5/2,3/22 to the upper excited levels are also presented. For calculating these cross-sections, we have obtained the atomic wave functions of copper using the multi-configuration Dirac–Fock approximation theory. To ensure the accuracy of these wave functions, we compared our calculated oscillator strengths of some dipole-allowed transitions of Cu with the available earlier reported values. We have utilized all the calculated electron impact fine-structure level excitation cross-sections from the ground as well as the metastable states of Cu to develop a fine structure-resolved collisional-radiative (CR) model for the diagnostics of laser-produced Cu plasma at atmospheric pressure. The model has been applied for diagnostics by coupling it with the spatially resolved optical emission spectroscopy (OES) measurements of Singh and Sharma [Phys. Plasmas 23 122104 (2016)] in the presence and absence of a static magnetic field. For diagnostics, the intensities of three OES observed strong atomic emission lines of Cu viz, 510.5, 515.3, and 521.8 nm have been utilized in the absence and presence of a magnetic field at different axial lengths (z = 0.5–6.5 mm) from the Cu target. Also, these intensities are corrected using the internal reference self-absorption method to overcome the effect of radiation trapping. The normalized intensities of the considered lines obtained from the CR model have been compared with their corresponding OES-measured values to extract the plasma parameters, i.e., electron temperature and electron density. Further, the obtained electron temperatures from the CR model are compared with the corresponding values reported in the experimental paper of Singh and Sharma [Phys. Plasmas 23 122104 (2016)] obtained using the Boltzmann plot method.

Tuning photophysical properties of bicarbazole-based blue TADF emitters with AIE feature: Trade-off between small singlet-triplet energy splitting and high photoluminescence quantum yield

Three aggregation-induced emission (AIE) and thermally activated delayed fluorescence (TADF) blue light-emitting materials were successfully synthesized using bicarbazole and phenylsulfonyl/benzophenone moieties as electron donors and acceptors, respectively, via Buchwald-Hartwig reaction. Density functional theory calculations showed that the three emitters have a moderate dihedral angle between the two carbazole planes and between the donor and acceptor, resulting in a good conjugated structure and a trade-off between the small ΔEST and high photoluminescence quantum yield of the BCzDPM molecule. The cyclic voltammetry, thermogravimetric analysis and differential scanning calorimetry tests demonstrated that the three materials had high electrochemical and thermal stability. The three emitters exhibited obvious intramolecular charge transfer characteristics in solution and film. According to the fluorescence and low-temperature phosphorescence spectra, the lowest singlet and triplet excited state energy levels of BCzDPM were 2.96 eV and 2.78 eV, respectively, with a ΔEST of 0.18 eV. Using these emitters as non-doped emissive layers, efficient blue electroluminescent devices were fabricated. The maximum current efficiency and external quantum efficiency reached 15.4 cd/A and 7.05% for the BCzDPM device, respectively, and the efficiency roll-off of BCzDPM was smaller than that of PSOBCz and PBCzPM, under high current density.

Low-ionization iron-rich broad absorption-line quasar SDSS J 1652+2650: physical conditions in the ejected gas from excited Fe ii and metastable He i

ABSTRACT We present high-resolution VLT/UVES spectroscopy and a detailed analysis of the unique broad absorption-line system towards the quasar SDSS J 165252.67+265001.96. This system exhibits low-ionization metal absorption lines from the ground states and excited energy levels of Fe ii and Mn ii, and the meta-stable $2\, ^3S$ excited state of He i. The extended kinematics of the absorber encompasses three main clumps with velocity offsets of −5680, −4550, and −1770 km s−1 from the quasar emission redshift, z = 0.3509 ± 0.0003, derived from [O ii] emission. Each clump shows moderate partial covering of the background continuum source, Cf ≈ [0.53; 0.24; 0.81]. We discuss the excitation mechanisms at play in the gas, which we use to constrain the distance of the clouds from the active galactic nucleus (AGN) as well as the density, temperature, and typical sizes of the clouds. The number density is found to be nH ∼ 104 cm−3 and the temperature Te ∼ 104 K, with longitudinal cloudlet sizes of ≳0.01 pc. cloudy photoionization modelling of He i⋆, which is also produced at the interface between the neutral and ionized phases, assuming the number densities derived from Fe ii, constrains the ionization parameter to be log U ∼ −3. This corresponds to distances of a few 100 pc from the AGN. We discuss these results in the more general context of associated absorption-line systems and propose a connection between FeLoBALs and the recently identified molecular-rich intrinsic absorbers. Studies of significant samples of FeLoBALs, even though rare per se, will soon be possible due to large dedicated surveys paired with high-resolution spectroscopic follow-ups.

Analyzing exciton distribution in organic light-emitting devices using near-infrared probes

Although organic light-emitting devices (OLEDs) can achieve an internal quantum efficiency (QE) of 100%, their external QE remains limited to less than 40% due to low outcoupling efficiency (OCE). The distribution of excitons is a critical factor in determining OLED OCE, as it affects the coupling to surface plasmon polaritons. Therefore, investigating exciton distribution through experiments is crucial to optimize device structure and enhance OCE. In this study, we propose a probe method to analyze exciton distribution by inserting an ultrathin (∼0.1 nm) near-infrared (NIR) material at a specific position within the emitting layer (EML). With a low excited state energy level, the NIR probe can utilize excitons generated around the specific EML position. By preparing different devices with the NIR probe at various EML positions, we can quantitatively present exciton distribution using the NIR to visible emission ratio. Our results demonstrate that this probe method is effective for investigating exciton distribution in blue, green, and red OLEDs with hole-dominant, electron-dominant, and bipolar transport EMLs, respectively.

Chloroplast photoprotection: face the light or run and hide?

Chloroplast photoprotection: face the light or run and hide?

Analysis of the 2p-manifold population distribution in a diode-pumped metastable Ar laser.

The complex excited energy levels in the diode-pumped metastable Ar laser may induce harmful effects in laser cycling. Significantly, the influence of the population distribution in 2p energy levels on the laser performance is unclear yet. In this work, the absolute populations in all the 2p states were measured online by the simultaneous applications of tunable diode laser absorption spectroscopy and optical emission spectroscopy. The results showed that most atoms were populated to the 2p8, 2p9, and 2p10 levels while lasing, and the majority of the 2p9 population was efficiently transferred to the 2p10 level with the aid of helium, which was beneficial for the laser performance.

SPECTROSCOPIC INVESTIGATION OF ARGON DC GLOW DISCHARGE IN PLASMA MEDIUM

In this study, UV-VIS-NIR (Ultraviolet Visible Near-Infrared) spectra emitted from Argon Glow discharge plasma in a low vacuum were recorded with a high-resolution Czerny-Turner type spectrometer. Argon plasma was produced at a pressure of 5mTorr and with a voltage of 584 V. Argon plasma was produced between two parallel stainless steel plates anode and cathode with a diameter of 15 cm, a thickness of 0.8 cm, and a distance of 13 cm between them. The radiative and collisional processes of the Argon plasma medium were modeled by the PrismSPECT atomic physics software (Software). The distributions of ion densities were calculated using the Saha-Boltzmann equation. The intensity of the excited energy levels of Ar(I) and Ar (II) ions were calculated in the electron temperature range of (0.4-3.5eV) and the mass density of (10-4-10-1gr/cm3). The UV-Visible-NIR spectra were simulated and compared with experimental spectra. The ratios of the intensities of the ArII/ArI (1s22s22p63s23p44f1/1s22s22p63s23p54p1) spectral lines were obtained for different plasma temperatures and densities. The temperature of the argon plasma was obtained from the spectral line intensity ratios.

Rotationally Resolved Infrared Spectroscopy of Supersonic Jet-Cooled Isoprene.

The high-resolution infrared spectrum of isoprene has been observed under supersonic jet-cooled conditions in the region of the ν26 vibrational band near 992 cm-1. The spectrum was assigned and fit using a standard asymmetric top Hamiltonian, and an acceptable fit was obtained for transitions to excited state energy levels with J ≤ 6, with an error in the fit of 0.002 cm-1. For excited state energy levels with J > 6, a perturbation was present that prevented fitting using the standard asymmetric top Hamiltonian. Based on previous anharmonic frequency calculations and observed vibrational bands of isoprene, the perturbation is most likely caused by Coriolis coupling between the ν26 and ν17 vibrations or a combination band that lies near the ν26 band. The excited state rotational constants from the fit show reasonable agreement with previous anharmonic calculations performed at the MP2/cc-pVTZ level of theory. The jet-cooled spectrum is compared with previous high-resolution measurements of this band at room temperature and shows that understanding the perturbation will be necessary to accurately model this vibrational band.

Transfer reaction measurements using SNACK at KoBRA

KoBRA can produce RI beams with energies of 5–10 MeV/u from stable ion beams (10–40 MeV/u) delivered from the superconducting linear accelerator SLC3 of RAON. In its early phase of operation, transfer reaction measurements with these RI beams can be performed for nuclear astrophysics studies. SNACK has been developed at RISP in order to measure the light ejectiles from the transfer reactions. With the beam trajectories obtained from upstream PPACs, excitation energy levels in the heavy recoils can be reconstructed by measuring light ejectile’s energies and scattering angles. The expected results of transfer reaction measurements with SNACK and KoBRA beamline detectors were calculated by using a Monte Carlo simulation.

Response Speed‐Tunable Photodetectors Based on Hybrid Ternary FePSe3 Nanoflakes

AbstractThe layered metal phosphorus trichalcogenides (MPTs) are a newly emerging van der Waals material family with bandgaps ranging from 1.3 to 3.5 eV, which are promising candidates for optoelectronic devices. By using the excited multiple energy levels of FePSe3, a high‐performance FePSe3 photodetector, which shows tunable response speed in the range of ultraviolet (UV) to near‐infrared (NIR), is designed. The FePSe3 photodetector exhibits a high photoresponsivity of 236.18 A·W−1 under 532 nm laser illumination (laser power density P = 1 mW cm−2). The properties of FePSe3 can be modulated by oxygen plasma treatment, which transfer to oxygen‐doped FePSe3 (FePSe3‐O). Moreover, the speed of the FePSe3‐O photodetector can be improved more than 240 times compared to the intrinsic FePSe3 photodetector under NIR illumination (λ = 808 nm). In addition, the FePSe3‐graphene heterojunction can significantly improve the photoresponsivity and simultaneously prolong the response time of the device due to the FePSe3/graphene interfacial barrier. These results suggest that intrinsic, doped FePSe3 and its heterojunction can be used as multifunctional photodetectors with tunable response speeds.

Loosely bound few-body states in a spin-1 gas with near-degenerate continua

A distinguishing feature of ultracold collisions of bosonic lithium atoms is the presence of two near-degenerate two-body continua. The influence of such a near degeneracy on the few-body physics in the vicinity of a narrow Feshbach resonance is investigated within the framework of a minimal model with two atomic continua and one closed molecular channel. The model allows analysis of the spin composition of loosely bound dimers and trimers. In the two-body sector the well-established coupled-channel calculation phenomenology of lithium is qualitatively reproduced, and its particularities are emphasized and clarified. In the three-body sector we find that the Efimov trimer energy levels follow a different functional form as compared to a single continuum scenario while the thresholds remain untouched. This three-channel model with two atomic continua complements our earlier developed three-channel model with two molecular channels [Yudkin and Khaykovich, Phys. Rev. A 103, 063303 (2021)] and suggests that the experimentally observed exotic behavior of the first excited Efimov energy level (Yudkin, Elbaz, and Khaykovich, arXiv:2004.02723) is most probably caused by the short-range details of the interaction potential.

NASA Polynomial representation of molecular specific heats

So called NASA polynomials are widely used in plasma and combustion models to represent the specific heat of molecules as a function of temperature. In this work, we compute seven-term NASA polynomials for 464 molecules of which 44 are cations and 9 are anions; polynomials are not currently available for almost 200 of these species. Calculation of the NASA polynomials utilises data provided by the ExoMol database, the HITRAN database, the diatomic partition functions computed by Barklem and Collet, and the JANAF thermodynamic tables. Our results are compared against existing polynomial compilations where available, and for cases where there are multiple datasets the recommended polynomials are identified. As proposed in the original compilation, the seven-term polynomials are fitted separately for the temperature ranges 200 – 1000 K and 1000 – 6000 K. In general, different data sources give good agreement in the lower temperature range but there are significant discrepancies at higher temperatures, which can be attributed to the underlying assumptions made about highly excited rotation-vibration energy levels.

Molecular engineering of Pyran‐fused acceptor–donor–acceptor‐type non‐fullerene acceptors for highly efficient organic solar cells—A density functional theory approach

AbstractThe end‐capped modification proves that it is an excellent attempt to improve the solar cells performances. Therefore, nowadays, many researchers are working to design new molecules for potential use in organic photovoltaics. Herein, we have modified new molecules (SA1–SA5) from the reference (R) for fullerene‐free solar cells. These novel molecules have lower excitation energy levels that make the easier excitation in the excited state. Additionally, SA1 to SA5 molecules exhibit excellent charge mobility due to the modification of an efficient core units. Geometric and physiochemical investigations indicate that the modeled molecules are beneficial for efficient organic solar cells. The estimation of frontier molecular orbitals analysis, reorganizational energy, photovoltaic characteristics, and charge transmission calculations was done using density functional theory calculations with B3LYP/6‐31G (d, p) basis set. Among all designed molecules, SA3 has emerged as the preferred choice because of its outstanding photovoltaic characteristics, which include a minimal bandgap of 2.03 eV and reorganization energy of electron and holes of 0.0095 and 0.0077 eV, correspondingly. The designed materials (SA1–SA5) displayed a high λ max values, that is, 693.54 nm (in gas) and 679.63 nm (in chloroform). This theoretical framework suggests that the required photovoltaic properties may be efficiently obtained by remodeling the new molecules.

Mixed symmetry states in 96Mo and 98Ru isotones in the framework of interacting boson model

The software package IBM code for interacting boson model-1 and Neutron Proton Boson NPBOS code for interacting boson model-2 have been used to calculate energy levels for, for by estimating a set of parameters which are used to predict the behavior of even-even isotones within the current scope of work there is clear competition between the two parameters (ε and a2) in isotones, as an inverse relationship. This means that vibrational qualities are continuous mixed with the rotational properties. In interacting boson model-2 parameters(ε, κ, χπ and χν) have been shown similarity with interacting boson model-1 expected. The Majorana parameter effect (ζ2) on the calculated excitation energy level for isotones has been accomplished by vary the ζ2 around the optimum-matches to practical data. The effect of increasing ζ2 on mixing symmetry states is the same in all isotones but different from state to another, we find the state J+ = 23+ was the lowest mixing symmetry states still approximately constant in the all. In that time,isotones have 1+, 3+1, 5+1 mixed symmetry states, rapidly increasing with increasing ζ2. The results of the calculated energy levels were in acceptable agreement with the experimental data. There is no pure vibrational property of these isotones

Temperature dependence of Cr:CYA effective emission cross-section

A high-quality Cr:CYA (Cr:CaYAlO4) single crystal fiber was grown by μ-PD (Micro-Pulling-Down) method. The E//a and E//c polarized excitation spectra of Cr:CYA at room temperature was measured. The crystal field parameters were calculated and the energy level structure of Cr:CYA was analyzed. We also measured the polarization emission spectra and lifetimes at different temperatures and calculated the effective emission cross-section. Based on the above data and Boltzmann law, the thermal distribution between the excited energy levels 2E and 4A2 at different temperatures was analyzed. The present work may be useful for guiding laser research on Cr:CYA and other Cr3+-doped laser crystals above room temperature.