Detailed Energy Level Research Articles

Crystal structure, theoretical calculations, mechanoluminescence feature and antimicrobial activity based on a double-armed Salamo-type ligand and its trinuclear Cu(Ⅱ) complex

A double-armed salamo-type ligand H4L and its Cu(Ⅱ) complex have been designed and synthesized. The stoichiometric ratios of the prepared H4L and its Cu(Ⅱ) complex were structurally characterized by a variety of analytical and spectroscopic techniques, including elemental analysis, FT-IR, UV–visible, fluorescence spectroscopy, and X-ray crystal diffraction. The results showed that H4L is a linear molecule, while the Cu(Ⅱ) complex is a trinuclear structure with three copper atoms exhibiting different coordination modes due to varying coordination cavities and bridging atoms. The quantum chemical parameters and molecular structures of the H4L and the Cu(Ⅱ) complex have been theoretically calculated and studied. Using molecular electrostatic potential (MEP) and density functional theory (DFT) calculations to understand the selectivity of the H4L and the Cu(Ⅱ) complex chemistry and related reactions. Detailed energy level transitions of the H4L and the Cu(Ⅱ) complex can be determined through time-dependent density functional theory (TD-DFT) calculations. In studying the fluorescence properties of liquid and solid states, it was observed that increasing water content leads to the formation of excimer in both the H4L and its Cu(Ⅱ) complex, the ligand H4L shown good mechanoluminescence, but the Cu(Ⅱ) complex did not. We studied the antimicrobial effectiveness of the H4L and the Cu(Ⅱ) complex against E. coli., the Cu(Ⅱ) complex showed higher inhibition of the pathogenic microorganisms.

Monte Carlo method for investigating population kinetics in non-local thermodynamic equilibrium plasmas

We propose a new method to solve the collisional-radiative (CR) model with the Monte Carlo method for investigating population kinetics of non-local thermodynamic equilibrium plasmas. The CR model is solved using massive sample particles accounting detailed energy levels. Whether an atom/ion undergoes an ionization/excitation/decay process is determined by probabilities calculated from ionization cross-sections, excitation and decay rates. By continuously iterating this process for massive atoms/ions, the ionization population distribution is obtained. The numerical convergence can be achieved for a mid-Z element using 103 particles in the Monte Carlo simulation. The results of the Monte Carlo simulations are compared with other methods and experimental results. The self emission spectra of silicon plasma is obtained and the ionization population distribution of silicon and iron plasmas are calculated. The proposed method can be used to interpret high energy density experiments and astrophysical phenomena where non-local thermodynamic equilibrium effects play vital roles.

Erbium energy levels in GaN grown by hydride vapor phase epitaxy

Erbium doped GaN (Er:GaN) is a promising candidate as a novel gain medium for solid-state high energy lasers (HELs) due to its superior physical properties over a synthetic garnet such as Nd:YAG. Er:GaN emits in the 1.5 µm region, which is retina-safe and has a high transmission in the air. We report photoluminescence (PL) studies performed on Er:GaN epilayers synthesized by the hydride vapor phase epitaxy (HVPE) technique. The room temperature PL spectra of HVPE grown Er:GaN epilayers resolved as many as 11 and seven emission lines in the 1.5 µm and 1.0 µm wavelength regions, respectively, corresponding to the intra-4f shell transitions between Stark levels from the first (4I13/2) and the second (4I11/2) excited states to the ground state (4I15/2) of Er3+ in GaN. The observed peak positions of these transitions enabled the construction of the detailed energy levels in Er:GaN. The results agree well with those of the calculation based on a crystal field analysis. Precise determination of the detailed energy levels of the Stark levels in the 4I11/2, 4I13/2, and 4I15/5 states is critically important for the realization of HELs based on Er:GaN.

Characterisation of the b 3Σ+, v = 0 state and its interaction with the A 1Π state in aluminium monofluoride

Recently, we determined the detailed energy level structure of the , and states of AlF that are relevant to laser cooling and trapping experiments [Truppe et al., Phys. Rev. A. 100 (5), 052513 (2019)]. Here, we investigate the state of the AlF molecule. A rotationally resolved (1 + 2)-REMPI spectrum of the band is presented and the lifetime of the state is measured to be 190(2) ns. Hyperfine-resolved, laser-induced fluorescence spectra of the and the bands are recorded to determine fine- and hyperfine structure parameters. The interaction between the and the nearby state is studied and the magnitude of the spin–orbit coupling between the two electronic states is derived using three independent methods to give a consistent value of 10(1) cm. The triplet character of the A state causes an loss from the main A−X laser cooling cycle below the 10 level.

Spectroscopic characterization of aluminum monofluoride with relevance to laser cooling and trapping

Here we report on spectroscopic measurements of the aluminum monofluoride molecule (AlF) that are relevant to laser cooling and trapping experiments. We measure the detailed energy level structure of AlF in the X$^1\Sigma^+$ electronic ground state, in the A$^1\Pi$ state, and in the metastable a$^3\Pi$ state. We determine the rotational, vibrational and electronic branching ratios from the A$^1\Pi$ state. We also study how the rotational levels split and shift in external electric and magnetic fields. We find that AlF is an excellent candidate for laser cooling on any Q-line of the A$^1\Pi$ - X$^1\Sigma^+$ transition and for trapping at high densities.

Efficient Anti-solvent-free Spin-Coated and Printed Sn-Perovskite Solar Cells with Crystal-Based Precursor Solutions

Summary Tin-based perovskite solar cells (PSCs), with more consummate optical band gaps, lower exciton-binding energies, and higher charge-carrier mobility, have not attracted tremendous research efforts compared with the lead-based ones that have a record power conversion efficiency (PCE) of 24.2%. The major challenges for Sn-based research are significantly low open-circuit voltage, poor reproducibility, and environmental instability. It has been identified that the oxidation processes take place during the preparation of precursor solutions and fabrication of films, due to the low redox potential of the stannous absorption layer. Herein, we propose two strategies of crystal-resolving and recrystallization technology to reduce the oxidation process. As a result, PCEs of 8.9% (active area of 0.04 cm2) and 5.5% (active area = 1.01 cm2) are attained using the inverted p-i-n structure, which will lead to a revival of lead-free PSC research.

Perovskite solar cells: In pursuit of efficiency and stability

Perovskite solar cells (PSCs) are coming with positive hopes for researchers to commercialize high-power conversion efficiency (PCE) and low-cost solar cells. Recently, NREL-certified record PCE of PSC is 22.1%, which is competing to silicon solar cells has been reported. However, PSC devices are environmentally sensitive leading to a rapid PCE degradation. Therefore, it is important to understand the impact of the role of various parameters to achieve highly stable PSC without compromising on its performance. This review contains an overview of a recent progress in PSC with respect to PCE, materials engineering, and stability. Energy level diagram of various perovskite materials, electron conducting materials (ECMs) and hole conducting materials (HCMs) constitute pivotal role in selecting their combinations. Hence we have added detailed energy level diagrams from which researcher can select best possible combination to achieve highest efficiency. An in-depth discussion on the types of PSCs based on thin film, mesoporous, n-i-p and p-i-n architectures fabricated by using different deposition techniques has been provided. In order to transfer this exciting achievement to industry level, it is necessary to understand degradation process at different conditions. A detailed discussion on the mechanism of recombination, instability in PSCs and achieved success has been incorporated to apprehend the step-wise developments in this field and to find possible pathways that limit their stability.

Luminescence properties and energy transfer studies of color tunable Tb3+-doped RE1/3Zr2(PO4)3 (RE = Y, La, Gd and Lu)

The cooperation between host and activator ions in nature could enable novel controllability of emission colors in single host. This work presents the vacuum ultraviolet-visible (VUV-Vis) spectroscopic properties of Tb3+-doped NASICON-type RE1/3Zr2(PO4)3 (RE = Y, La, Gd and Lu) prepared by a Pechini method. The cooperation between self-active host and Tb3+ ions leads to tunable emission from the (greenish-)blue to yellowish-green region by appropriate adjusting the Tb3+ content. The visible cross relaxation between Tb3+ ions and energy transfer from host/Gd3+ to Tb3+ were observed and confirmed. A detailed energy level diagram that contains 4f levels of all divalent and trivalent lanthanide ions with respect to the valence and conduction bands of Gd1/3Zr2(PO4)3 has been constructed and explained. In addition, the energy transfer processes and cross relaxation processes were discussed.

Notably Improved Red Photoresponse of Organic Diode Employing Gold Nanoparticles Plasmonic Absorption.

The wide variation of optical absorptions of AuNPs provides a strategy to fabricate simple photosensitive sensors. We demonstrate a notably improved red photoresponse of organic diode by incorporation of 3-nm gold nanoparticles (AuNPs) into NPB/C60 heterojunction interface. Near-field enhancement around AuNPs gives rise to the significant improvement of exciton generation and dissociation in the interface of organic photodiode (OPD), thereby obtaining a sharply increasing photocurrent. A detailed energy level diagram is proposed to interpret the improvement of photocurrent. Significantly, the OPD exhibits excellent diode characteristics in the dark. On the other hand, the device shows a large red photoresponse with responsivity greater than 200 mA/W. The calculated maximum D* and EQE are 1.52 x 10(11) jones and 39.21% at a very low voltage of -0.5 V, respectively. Note that the NPB and C60 almost have no absorption at 650 nm; the red photoresponse performance above is one of the highest values reported thus far for the single AuNPs layer dominant OPDs. It is expected that such a red-light detector will have potential application in future optoelectronic devices.

Improved performance for white phosphorescent organic light-emitting diodes utilizing an orange ultrathin non-doped emission layer

The chemical structures of materials, the device structures (a) and the detailed energy level diagram of the materials (b).

Photoluminescence properties and energy levels of RE (RE = Pr, Sm, Er, Tm) in layered-CaZnOS oxysulfide

RE3+ (RE = Pr, Sm, Er, Tm)-activated CaZnOS samples were prepared by a solid-state reaction method at high temperature, and their photoluminescence properties were investigated. Doping with RE3+ (RE = Pr, Sm, Er, Tm) into layered-CaZnOS resulted in typical RE3+ (RE = Pr, Sm, Er, Tm) f-f line absorptions and emissions, as well as the charge transfer band of Sm3+ at about 3.3 eV. The energy level scheme containing the position of the 4f and 5d levels of all divalent and trivalent lanthanide ions with respect to the valence and conduction bands of CaZnOS has been constructed based on the new data presented in this work, together with the data from literature on Ce3+ and Eu2+ doping in CaZnOS. The detailed energy level scheme provides a platform for interpreting the optical spectra and could be used to comment on the valence stability of the lanthanide ions in CaZnOS.

A Novel Full-Reference Color Image Quality Assessment Based on Energy Computation in the Wavelet Domain

AbstractThis article presents a novel full-reference (FR) image quality assessment (QA) algorithm by depicting the sub-band characteristics in the wavelet domain. The proposed image quality assessment method is based on energy estimation in the wavelet-transformed image. Image QA is achieved by applying a multilevel wavelet decomposition on both the original and the enhanced image. Next, the wavelet energy (WE) and vector are computed to obtain the percentage of the energy that corresponds to the approximation and the details, respectively. Further, the approximate and detailed energy levels of both the original and the enhanced images are compared to formulate an image quality assessment. Numerous experiments are conducted on a dozen of image enhancement algorithms. The results presented show that the image with poor contrast in the foreground than the background has continuous regular coefficient values. The probability density function for such an image has a relatively lower WE and skewness compared with the background. The proposed scheme not only evaluates the global information of an image but also estimates the fine, detailed changes in an enhanced image. Thus, the proposed metric serves as an objective and effective FR criterion for color image QA. The experimental results presented confirm that the proposed WE metric is an efficient and useful metric for evaluating the quality of the color image enhancement.

Photoluminescence properties and energy level locations of RE3+ (RE = Pr, Sm, Tb, Tb/Ce) in CaAlSiN3 phosphors

RE3+ (RE = Pr, Sm, Tb, Tb/Ce)-activated CaAlSiN3 samples were prepared by a solid-state reaction method at high temperature, and their photoluminescence properties were investigated. An interesting observation is that the 5d bands of Pr3+ and Tb3+ are at rather low energy in CaAlSiN3 compared to oxides. Pr3+-doped CaAlSiN3 shows strong 4f15d1 → 4f2 emission bands (334–480 nm) as well as typical 4f2 → 4f2 emission lines (480–800 nm) of Pr3+ under 4f2 → 4f15d1 excitation. Sm3+-doped CaAlSiN3 exhibits bright red emission originating from 4G5/2 → 6HJ (J = 5/2, 7/2 and 9/2) transitions, and the charge transfer band of Sm3+ was observed at an unusually low energy of 3.91 eV. In Tb3+-doped samples, the direct Tb3+ 4f8 → 4f75d1 excitation leads to 5D3 → 7FJ (J = 6, 5, 4, 3, 2, 1) (blue) and 5D4 → 7FJ (J = 6, 5, 4, 3) (green) line emissions. The bands at about 252 nm in the excitation spectra are attributed to the host lattice absorption. It is observed that there is energy transfer from the host lattice to the luminescent activators (Pr3+, Sm3+, Tb3+). In Tb3+/Ce3+-codoped CaAlSiN3, an effective energy transfer process exists from Tb3+ to Ce3+. A detailed energy level diagram that contains the position of the 4f and 5d levels of all divalent and trivalent lanthanide ions with respect to the valence and conduction bands of CaAlSiN3 has been constructed and explained.

Spectrum of electron-hole states of the Si/Ge structure with Ge quantum dots

The lateral photoconductivity spectra of Si/Ge multilayer structures with Ge quantum dots of various sizes are investigated. We observed optical transition lines between the hole levels of quantum dots and electronic states of Si. This enabled us to construct a detailed energy level diagram of the electron-hole spectrum of the Si/Ge structures. It is shown that the hole levels of Ge quantum dots are successfully described by the “quantum box” model using the actual sizes of Ge islands. It I found that the position of the longwavelength photosensitivity boundary of Si/Ge structures with Ge quantum dots can be controlled by changing the growth parameters.

Spectra simulation of the argon plasma

In this work, a simulation calculation scheme based on a collisional radiation model and employing detailed energy levels was developed under the framework of corona approximation for low-density plasmas. Atomic data such as energy levels, radiative transition rates, Auger rates, collision excitation and ionization cross sections needed for the simulation were calculated by using the Flexible Atomic Code. In this work, the emission spectra of the first and second excited configurations of He-like Ar ions and their dielectronic and inner shell excited satellites from Li-like argon ions were studied for a low-density plasma, taking into account the influence of all satellite electrons of principal quantum number n<10. A comparison with the result of tokamak experiments under similar plasma conditions was made. Good agreement was seen for these spectra; however, the charge state balance between the He-like and Li-like Ar ions was not well modeled. A discussion of this deviation is presented.

Static and ultrafast dynamics of defects of SrTiO3 in LaAlO3/SrTiO3 heterostructures

A detailed defect energy level map was investigated for heterostructures of 26 unit cells of LaAlO3 on SrTiO3 prepared at a low oxygen partial pressure of 10−6 mbar. The origin is attributed to the presence of dominating oxygen defects in SrTiO3 substrate. Using femtosecond laser spectroscopy, the transient absorption and relaxation times for various transitions were determined. An ultrafast relaxation process of 2–3 ps from the conduction band to the closest defect level and a slower process of 70–92 ps from conduction band to intraband defect level were observed. The results are discussed on the basis of the proposed defect-band diagram.

Yb3+ doped LaSi3N5 and YSi3N5 with low energy charge transfer for near-infrared light-emitting diode and solar cell application

Yb3+ doped LaSi3N5 phosphors have been prepared by solid-state synthesis in a high temperature furnace directly coupled to a glove box. The charge transfer (CT) band of Yb3+ in LaSi3N5 was observed at an unusually low energy of 3.1 eV. Excitation of this CT band results in f–f emission of Yb3+ at 1.2 eV, which could make Yb3+ doped LaSi3N5 suitable for application as a spectral conversion material for infrared light-emitting diodes or solar cells. Substitution of La3+ by the smaller Y3+ ion shifts the CT to higher energy (3.9 eV). A clear relation between the CT energy and the Yb3+ f–f emission intensity was found. With the help of a detailed energy level diagram that contains the position of the 4f and 5d levels of all divalent and trivalent ions with respect to the valence and conduction band, all hitherto observed luminescence properties of divalent and trivalent lanthanide dopants in LaSi3N5 are reviewed and explained.

Comparison of energy structure and spectral properties of Ce:LaAlO3 and Ce:Lu2(SiO4)O

Undoped LaAlO3 and 1 at.% Ce:LaAlO3 single crystals were grown by the Czochralski process. Absorption and fluorescence spectra were measured at room temperature. Detailed energy levels structure of Ce:LaAlO3 was determined. In this paper, two viewpoints were provided. The first one is: the energy levels structure of Ce:LaAlO3 is very similar to that of Ce:Lu2(SiO4)O which is a well-known scintillator. In the energy levels structure of Ce:LaAlO3 and Ce:Lu2(SiO4)O, the lowest 5d energy level of Ce3+ is located below the bottom of the conduction band of host crystal and the other higher 5d energy levels of Ce3+ are located above the bottom of the conduction band of host crystal. The second one is: Ce:LaAlO3 single crystal may not be suitable for scintillation application; by comparing the energy levels structures of Ce:LaAlO3 and Ce:Lu2(SiO4)O, the large energy difference (1.13 eV) between the two lowest 5d energy levels of Ce3+ in LaAlO3 is a crucial factor that causes the luminescence quenching.

Emission spectra of lanthanide ions in hexafluoroelpasolite lattices excited by synchrotron radiation

Emission spectra at 10 K employing synchrotron radiation have been recorded for the tripositive lanthanide ions, Ln = Sm, Gd, Tb, Ho, and Er situated at octahedral (or nearly octahedral) site symmetry in hexafluoroelpasolite Cs 2NaMF 6 (M = Y, Sc, or Ga) lattices. Interconfigurational 5d → 4f transitions are only observed for Er 3+, and the intensity ratio of 4f 105d → 4f 11 emission, compared with 4f 11 → 4f 11 emission, with excitation into 5d levels, is greater for M = Ga than M = Sc. The highest energy intraconfigurational emission is from 4G 5/2 (Sm 3+), 6P 7/2 (Gd 3+), 5D 3 (Tb 3+), 5G 4 (Ho 3+), and 2F(2) 7/2 (Er 3+). Detailed energy level assignments have been given for Ln = Sm, Gd, and the remaining spectra are assigned as multiplet–multiplet transitions.

Intensity analysis and energy-level modeling of Nd3+ in Nd3+:Y2O3 nanocrystals in polymeric hosts

Optical absorption and emission intensities are investigated for Nd3+ in nanocrystalline Nd3+:Y2O3. Room temperature absorption intensities of Nd3+(4f3) transitions in synthesized Nd3+:Y2O3 nanocrystals have been analyzed using the Judd–Ofelt (J-O) approach to obtain the phenomenological intensity parameters. The J-O intensity parameters are used to calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios of the Nd3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds L2S+1J of Nd3+(4f3). The emission cross sections and room temperature fluorescence lifetimes of the important intermanifold F43/2→I4J (J=9/2,11/2,13/2,15/2) transitions have been determined. We also compare the spectra of the Nd3+:Y2O3 nanocrystals to those of the nanocrystals embedded in polymeric matrices of epoxy and chitosan, and we find similarities in terms of the detailed Stark energy levels of the Nd3+ ion in the Y2O3 nanocrystalline host. The 300 K spectra are analyzed for the energy (Stark) level transitions between the L2S+1J multiplet manifolds of Nd3+(4f3). The results of this study are also compared with a crystal-field splitting analysis reported earlier for single-crystal Nd3+:Y2O3 grown by a modified flame fusion method. We find that the spectroscopic properties of our nanocrystals embedded in polymeric hosts compare favorably with other ceramic and single-crystal forms of Nd3+:Y2O3 currently available.