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White LED applications are still constrained by extremely efficient narrow band red emitting phosphors. Meanwhile, the concentration quenching induced by energy migration is the main reason that limits the emission intensity of a red emitting phosphor. Therefore, developing a novel red emitting material with energy migration limitations seems necessary. Here, we proposed and realized the non-concentration quenching doping of Eu3+ ions in a Sr9Y2−2xW4O24:xEu3+ (0 ≤ x ≤ 1.0) phosphor for the first time by means of host preferential selection. By clearly investigating the crystal structure and luminescence kinetics, the long-distance between the nearby Eu3+ ions and the low phonon energy are the main reasons that suppress the energy migration and the cross-relaxation among Eu3+ ions. These advantages result in a high internal (90.47%) and external quantum efficiency (42.1%) of Sr9Eu2W4O24. With the help of the Judd–Ofelt theory and the large value of oscillator strength Ω2, Eu3+ ions are verified to occupy the non-symmetric lattice site with high color purity (94.4%). In addition, only 5.2% emission intensity loss at 140 °C can guarantee its application in LED devices. Moreover, the SYWO:Eu3+ phosphor has high thermal tolerance, high color stability, excellent moisture resistance and superior physical/chemical stability, and thus has broad practical spectral application prospects. The prepared WLED shows superior performance, and the calculated NTSC values are as high as 101.8% and 104.7%, respectively. For comparison, the optical performances of the Sr9Y2W4O24:Eu3+ phosphor outperform those of the standard commercial red phosphors, Y2O3:Eu3+ and Y2O2S:Eu3+, and almost match that of K2MnF6. These results may pave the way for fresh approaches to the study of high-performance Eu3+-activated phosphors. [ABSTRACT FROM AUTHOR]

We perform micro-photoluminescence and Raman experiments to examine the impact of biaxial tensile strain on the optical properties of WS2 monolayers. A strong shift on the order of −130 meV per % of strain is observed in the neutral exciton emission at room temperature. Under near-resonant excitation, we measure a monotonic decrease in the circular polarization degree under the applied strain. We experimentally separate the effect of the strain-induced energy detuning and evaluate the pure effect coming from the biaxial strain. The analysis shows that the suppression of the circular polarization degree under the biaxial strain is related to an interplay of energy and polarization relaxation channels as well as to variations in the exciton oscillator strength affecting the long-range exchange interaction. [ABSTRACT FROM AUTHOR]

The formation of plasmon-exciton (plexciton) polariton is a direct consequence of strong light-matter interaction, and it happens in a semiconductor–metal hybrid system. Here the formation of plasmon-exciton polaritons was observed from an AgTe/CdTe Quantum Dot (QD) solid system in the strong coupling regime. The strong coupling was achieved by increasing the oscillator strength of the excitons by forming coupled QD solids. The anti-crossing-like behaviour indicates the strong coupling between plasmonic and excitons state in AgTe/CdTe QD solids, resulting in a maximum Rabi splitting value of 225 meV at room temperature. The formation of this hybrid state of matter and its dynamics were studied through absorption, photoluminescence, and femtosecond transient studies. [ABSTRACT FROM AUTHOR]

Bimetallic end‐on μ2‐η1:η1‐N2 bridging dinitrogen complexes have served as the platform for photochemical N2 activation, mainly for the N−N cleavage. However, the alternate N−N π‐photoactivation route has remained largely unexplored. This study strengthens the notion of weakening the N−N bond through the population of π* orbital upon electronic excitation from the ground to the first excited state using four prototypical complexes based on Fe (1), Mo (2), and Ru (3,4). The complexes 1–4 possess characteristic N−N π* based LUMO (π*‐π*‐π*) centered on their M−N−N−M core, which was earlier postulated to play a central role in the N2 photoactivation. Vertical electronic excitation of the highest oscillator strength involves transitions to the N−N π*‐based acceptor orbital (π*‐π*‐π*) in complexes 1–4. This induces geometry relaxation of the first excited metal‐to‐nitrogen (π*) charge transfer (1MNCT) state leading to a "zigzag" M−N−N−M core in the equilibrium structure. Obtaining the equilibrium geometry in the first excited state with the full‐sized complexes widens the scope of N−N π‐photoactivation with μ2‐η1:η1‐N2 bridging dinitrogen complexes. Promisingly, the elongated N−N bond and bent ∠MNN angle in the photoexcited S1 state of 1–4 resemble their radical‐ and di‐anion forms, which lead toward thermodynamically feasible N−N protonation in the S1 excited state. [ABSTRACT FROM AUTHOR]

Controlling coherent light–matter interactions in semiconductor microcavities is at the heart of the next-generation solid-state polaritonic devices. Organic–inorganic hybrid perovskites are potential materials for room-temperature polaritonics owing to their high exciton oscillator strengths and large exciton binding energies. Herein, we report on strong exciton-photon coupling in the micro-platelet and micro-ribbon shaped methylammonium lead bromide single crystals. Owing to high crystallinity and large refractive index, the as-grown perovskite microcrystals serve as self-hybridized optical microcavities along different orientations due to their distinct physical dimensionalities. In this regard, the perovskite micro-platelet forms a simple Fabry–Perot microcavity in out-of-plane orientation, while the micro-ribbon functions as a Fabry–Perot type waveguide microcavity within the plane of the perovskite sample. Consequently, excitons in these microcavities strongly interact with their corresponding uncoupled cavity modes, yielding multimode exciton-polaritons with Rabi splitting energies ∼205 and 235 meV for micro-platelet and micro-ribbon geometry, respectively. Furthermore, micro-ribbon geometry displays Young's double-slit-like interference patterns, which together with the numerical simulation readily reveals the parity and the mode order of the uncoupled cavity modes. Thus, our results not only shed light on strong exciton-photon coupling in various morphologies of methylammonium lead bromide microcrystals but also open an avenue for advanced polaritonic devices. [ABSTRACT FROM AUTHOR]

This review delves into the utilization of a sextic oscillator within the β degree of freedom of the Bohr Hamiltonian to elucidate critical-point solutions in nuclei, with a specific emphasis on the critical point associated with the β shape variable, governing transitions from spherical to deformed nuclei. To commence, an overview is presented for critical-point solutions E(5), X(5), X(3), Z(5), and Z(4). These symmetries, encapsulated in simple models, all model the β degree of freedom using an infinite square-well (ISW) potential. They are particularly useful for dissecting phase transitions from spherical to deformed nuclear shapes. The distinguishing factor among these models lies in their treatment of the γ degree of freedom. These models are rooted in a geometrical context, employing the Bohr Hamiltonian. The review then continues with the analysis of the same critical solutions but with the adoption of a sextic potential in place of the ISW potential within the β degree of freedom. The sextic oscillator, being quasi-exactly solvable (QES), allows for the derivation of exact solutions for the lower part of the energy spectrum. The outcomes of this analysis are examined in detail. Additionally, various versions of the sextic potential, while not exactly solvable, can still be tackled numerically, offering a means to establish benchmarks for criticality in the transitional path from spherical to deformed shapes. This review extends its scope to encompass related papers published in the field in the past 20 years, contributing to a comprehensive understanding of critical-point symmetries in nuclear physics. To facilitate this understanding, a map depicting the different regions of the nuclide chart where these models have been applied is provided, serving as a concise summary of their applications and implications in the realm of nuclear structure. [ABSTRACT FROM AUTHOR]

This study presents a simple model within the effective mass approximation to describe the magnetic field impact on the energy structure and interband optical quantum transitions in type-II ZnTe/CdSe and CdSe/ZnTe spherical quantum dots. The dependencies energy spectra and wave functions of an electron and hole on the magnetic field are calculated by the diagonalization method for spherical quantum dots of different sizes. It is shown that the magnetic field violates the spherical symmetry of the system and takes off the degeneration of the energy spectrum concerning the magnetic quantum number. For QD ZnTe/CdSe, the energy of the electron, and for QD CdSe/ZnTe, the energy of the hole in the states with m ≥ 0 increases when the magnetic field enhances; for the states with m < 0 , these dependences are non-monotonous (decreasing at first and then increasing). Moreover, the ground state of an electron for QD ZnTe/CdSe and the ground state of a hole for QD CdSe/ZnTe are formed alternately by the lowest states m = 0 , - 1 , - 2 , ... with increasing the induction of magnetic field (Aharonov–Bohm effect). The dependencies of the oscillator strength and the quantum energy transition on magnetic field induction are calculated. [ABSTRACT FROM AUTHOR]

In this work, a krypton gas impurity seeding experiment was conducted in a Large Helical Device. Emission lines from the Na-like Kr ion in the extreme ultraviolet wavelength region, such as 22.00 nm, 17.89 nm, 16.51 nm, 15.99 nm, and 14.08 nm, respective to 2 p 6 3 p (2 P 1 / 2 o) − 2 p 6 3 s (2 S 1 / 2) , 2 p 6 3 p (2 P 3 / 2 o) − 2 p 6 3 s (2 S 1 / 2) , 2 p 6 3 d (2 D 3 / 2) − 2 p 6 3 p (2 P 3 / 2 o) , 2 p 6 3 d (2 D 5 / 2) − 2 p 6 3 p (2 P 3 / 2 o) , and 2 p 6 3 d (2 D 3 / 2) − 2 p 6 3 p (2 P 1 / 2 o) transitions, are observed. In order to generate a theoretical synthetic spectrum, an extensive calculation concerning the excitation of the Kr 25 + ion through electron impact was performed for the development of a suitable plasma model. For this, the relativistic multiconfiguration Dirac–Hartree–Fock method was employed along with its extension to the relativistic configuration interaction method to compute the relativistic bound-state wave functions and excitation energies of the fine structure levels using the General Relativistic Atomic Structure Package-2018. In addition, another set of calculations was carried out utilizing the relativistic many-body perturbation theory and relativistic configuration interaction methods integrated within the Flexible Atomic Code. To investigate the reliability of our findings, the results of excitation energies, transition probabilities, and weighted oscillator strengths of different dipole-allowed transitions obtained from these different methods are presented and compared with the available data. Further, the detailed electron impact excitation cross-sections and their respective rate coefficients are obtained for various fine structure resolved transitions using the fully relativistic distorted wave method. Rate coefficients, calculated using the Flexible Atomic Code for population and de-population kinetic processes, are integrated into the collisional-radiative plasma model to generate a theoretical spectrum. Further, the emission lines observed from the Kr 25 + ion in the impurity seeding experiment were compared with the present plasma model spectrum, demonstrating a noteworthy overall agreement between the measurement and the theoretical synthetic spectrum. [ABSTRACT FROM AUTHOR]

Atomic-based field measurements have made significant progress in reproducibility, accuracy, and resolution enhancement. In this paper, the relative transition oscillator strength of excited 6P 3 / 2 to nD 5 / 2 /nD 3 / 2 can be measured more accurately by spectral results of Rydberg six-wave mixing, meanwhile accompanying measured efficiency of Rydberg electromagnetically induced transparent and fluorescence is compared. Relative transition oscillator strength is obtained and demonstrated, it is observed that relative transition oscillator strengths are independent of primary quantum n in thermal vapor. The measured results are approached with theoretical calculation which can not only extend relative transition oscillator strength of the measurement way in an atomic system, but can also demonstrate six-wave mixing as nonlinear process read information of laser excite atoms more accurately. [ABSTRACT FROM AUTHOR]

Ground‐ and excited‐state properties of complexes of SO3 with pyridine and bipyridine are studied with quantum‐mechanical approaches, an important endeavor as SO3 complexation is useful for mitigating its environmental impact and for designing photochromic polymers. Guided design of these polymers will benefit from detailed understanding of the performance of quantum‐mechanical methods to be used for such tasks. Therefore, here we study performance of density functional theory (DFT) and time‐dependent DFT (TD‐DFT) for predicting binding energies, relative energies and excitation spectra of pyridine‐SO3 and bipyridine‐SO3 complexes, in the gas phase and solution. Ground‐state properties are compared against DLPNO‐CCSD(T), DLPNO‐CCSD(T)‐F12 and CCSD(T)‐F12 calculations. Excited state properties are compared to second‐order Algebraic Diagrammatic Construction, ADC(2), and experimental data. For ground state properties, dispersion corrections make a massive improvement to computational data, with the revPBE‐D4 functional specifically recommended for its accuracy, ~1.5 kcal/mol error in the gas phase and ~2.8 kcal/mol in ethanol. For excited‐state properties, many density functionals perform quite well for predicting excitation energies, with most of them being range‐separated hybrids or double‐hybrids with spin‐scaled correlation. However, oscillator strengths from these functionals massively differ from ADC(2), with oscillator strengths from lower‐rung functionals like PBE, M06‐L and BP86 closer to ADC(2). [ABSTRACT FROM AUTHOR]

Y6 derivatives with asymmetric terminal groups have attracted considerable attention in recent years. However, the effects of the asymmetric modification of terminal groups on the photovoltaic performance of Y6 derivatives are not well understood yet. Therefore, we designed a series of Y6-based acceptors with asymmetric terminal groups by endowing them with various electron-withdrawing abilities and different conjugated rings to conduct systematic research. The electron-withdrawing ability of the Y6-D1 terminal group (substituted by IC-2F and IC-2NO2 terminals) is strongest, followed by Y6 (substituted by two same IC-2F terminals), Y6-D2 (substituted by IC-2F and 2-(4-oxo-4,5-dihydro-6H-cyclopenta[b]thiophen-6-ylidene)malononitrile terminals), Y6-D4 (substituted by IC-2F and indene ring), and Y6-D3 (substituted by IC-2F and thiazole ring). Computed results show that A–A stacking is the main molecular packing mode of Y6 and four other asymmetric Y6 derivatives. The ratios of A–A stacking face-on configuration of Y6-D1, Y6-D2, Y6-D3, Y6-D4, and Y6 are 51.6%, 55.0%, 43.5%, 59.3%, and 62.4%, respectively. Except for Y6-D1 substituted by the IC-2F and IC-2NO2 (the strongest electron-withdrawing capacity) terminal groups, the other three asymmetric molecules are mainly electron-transporting and can therefore act as acceptors. The open-circuit voltages of organic solar cells (OSCs) based on Y6-D2, Y6-D3, and Y6-D4, except for Y6-D1, may be higher than those of OSCs based on the Y6 acceptor because of their higher energy levels of lowest unoccupied molecular orbital (LUMO). PM6/Y6-D3 and PM6/Y6-D4 have better light absorption properties than PM6/Y6 due to their higher total oscillator strength. These results indicate that Y6-D3 and Y6-D4 can be employed as good acceptors. [ABSTRACT FROM AUTHOR]

The Fisher information-theoretic measurement and the oscillator strength are studied with a mixed hyperbolic Pöschl–Teller potential (MHPTP). Using the total energy eigenvalue equation obtained via the super-symmetric WKB approach as well as the total wave function. We obtained the oscillator strength for the atomic transitions 1 s - 2 p and 1 s - 3 p , where the strength length decreased with increasing potential screening parameters. Also, the Fisher information entropies for both position and momentum spaces are obtained numerically. We studied the correlation between potential parameters and the energy spectra graphically. Our results for the information-theoretic measures obey the Fisher's uncertainty product and the Cramer–Rao inequality in position space. The analytical result for the N -dimensional energy eigenvalue obtained by the super-symmetric WKB approach is the same as the result obtained by a different analytic approach in the existing literature. The oscillator strength conforms to the ones reported in existing literature using different potential energy functions. [ABSTRACT FROM AUTHOR]

Three distorted square antiprismatic eight coordinated neodymium acylpyrazolone complexes were synthesized having the compositions [Nd(L1)3(H2O)(EtOH)] (NdL1), [Nd(L2)3(H2O)(EtOH)] (NdL2), and [Nd(L3)3(H2O)(EtOH)] (NdL3). The structure of all three complexes was examined using ESI‐mass, FT‐IR, and thermogravimetric methods. According to the single crystal analysis of NdL1, the complex was found eight‐coordinated (NdO8) with a distorted square antiprismatic geometry. A powder XRD pattern confirmed a similar structural arrangement of the other two complexes. In electronic absorption spectra, the transition 4G5/2←4I9/2, which is close to the centre of the visible spectrum (~17,500 cm−1), exhibits hypersensitivity, which stands out in stark contrast to the behaviour of many other typically weak and reliably unchanging, typical 4f–4f transitions. Through a comparative analysis of calculated oscillator strength, Judd‐Ofelt parameters, root mean square deviation, radiative lifetime and covalency parameters in various solvents, hypersensitivity, symmetry characteristics, and covalency have been thoroughly investigated. The promotion of 4f–4f electric‐dipole intensity has been found to be particularly successful with ethanol, pyridine, DMF, and DMSO. Utilizing Judd‐Ofelt Ω4 values and Hirshfeld analysis, long‐range secondary π⋅⋅⋅π stacking or H‐bonding interactions were investigated. The intensity of emission spectra, quantum yield, stokes shift, and antenna effect energy diagram was examined using solid‐state emission spectra. [ABSTRACT FROM AUTHOR]

The main focus of this study is the spectroscopic properties of highly charged hafnium ions. Highly charged ions of high-Z elements (Z ~ 70–83) are of great importance in atomic physics, astronomical physics and especially plasma diagnostics. Therefore, we perform level energies, transition probabilities, wavelengths, and line strengths for electric dipole, electric quadrupole, and magnetic dipole transitions in Hf LXII (Hf 61+, Z = 72). All values are calculated using the AUTOSTRUCTURE atomic structure code whose relativistic corrections are introduced according to the Breit–Pauli distorted wave approach. Valence–valence, core–valence, and core–core electron correlation effects are included. The results are compared with other studies from the National Institute of Standards and Technology database. The present results are in good agreement with other studies in the literature. We hope to fill a lack of atomic data for highly charged hafnium ions, which may be useful in plasma diagnostics. [ABSTRACT FROM AUTHOR]

The FT–IR, FT–Raman and UV–Vis spectra of 2E-1-(3-bromothiophene-2-yl)-3-(1, 3-benzodioxol-5-yl)prop-2-en-1-one (BTBD) have been performed experimentally and simulated theoretically. The present investigation focuses mainly on quantum chemical calculations and the spectral characteristics of the molecule. The observed and theoretical wavenumbers have been assigned to respective vibrational modes through potential energy distribution (PED). The non-linear optical (NLO) properties have been explored through the calculation of the first hyperpolarizability of the BTBD compound. In the MEP map, it is evident that the negative site located the carbonyl group and the positive site over the CH2 group of 1, 3-benzodioxol, and all hydrogen atoms. From the HOMO–LUMO orbital investigation, the HOMO is caped on the C = O and C–C excluding the thiophene ring. The UV-Visible spectrum, the electronic properties which include wavelength, excitation energies, and oscillator strength were simulated via the DFT method. The antifungal ability of the molecule is predicted through in vitro evaluation toward four fungal strains. The NBO analysis confirms the hyper conjugative interaction and stabilization energy E (2). The in vitro anti-inflammatory activity was done via the protein denaturation assay method at various concentrations. Molecular docking studies were carried out to predict the active binding residues of the target. [ABSTRACT FROM AUTHOR]

In this work, we present the core–valence separation (CVS) approximation applied to unitary coupled-cluster (UCC) theory for the calculation of core-excited states and the simulation of x-ray absorption spectroscopy (XAS). Excitation energies and oscillator strengths of small- to medium-sized organic molecules have been computed using the second-order and extended second-order UCC schemes (CVS-UCC2 and CVS-UCC2-x) as well as the third-order scheme (CVS-UCC3). All results are compared to the corresponding algebraic-diagrammatic construction methods and experimental data. The agreement between CVS-UCC and experimental data demonstrates its potential as a new approach for the calculation of XAS. [ABSTRACT FROM AUTHOR]

We have fabricated organic semiconductor microcavities having an extended optical path-length (up to 2 µm) that contain J-aggregates of a cyanine dye. These structures are studied using optical-reflectivity and are found to be characterized by a series of polaritonic modes. By changing the effective oscillator strength of the dye within the cavity, we evidence a transition from "normal" strong coupling in which the photon modes are coupled to one another via the excitonic transition of the molecular dye to a state in which photon-modes become decoupled. We use an eight-level modified Hamiltonian to describe the optical properties of the system and compare the distribution of the confined optical field in coupled and decoupled structures. [ABSTRACT FROM AUTHOR]

Strain in two-dimensional transition metal dichalcogenide has led to localized states with exciting optical properties, in particular, in view of designing one photon sources. The naturally formed nanobubbles when the MoS2 monolayer is deposited on an hBN substrate lead to a local reduction in the band gap due to strain developing in the nanobubble. The photogenerated particles are thus confined in the strain-induced potential. Using numerical diagonalization, we simulate the spectra of the confined exciton states, their oscillator strengths, and their radiative lifetimes. We show that a single state of the confined exciton is optically active, which suggests that the MoS2/hBN nanobubbles are a good candidate for the realization of single-photon sources. Furthermore, our calculations show that the localized exciton gains in activation energy and radiative lifetime inside the nanobubble, the latter decreasing toward the one of free excitons when the nanobubble size increases. [ABSTRACT FROM AUTHOR]

The mechanism of resonance enhancement of a single harmonic during high-order harmonic generation in indium-, zinc-, and chromium-contained atomic and molecular plasmas is reexamined using single-color and two-color pumps of ablated species. We demonstrate that oxides, selenides, and phosphides of these metals notably reduce the enhancement of a single harmonic compared with purely atomic plasma due to either a shift of the ionic transitions possessing strong oscillator strength out of the wavelength of those harmonics or a reduction of the oscillator strength of these transitions. The role of oscillator strength in harmonic enhancement is discussed and compared with improvements in phase-matching conditions for some harmonics in the region of anomalous dispersion of ionic transitions. The application of different wavelengths of driving pulses drastically changes the enhancement of a single harmonic in indium-contained plasmas. [ABSTRACT FROM AUTHOR]

Strong coupling between surface plasmons and molecular excitons may lead to the formation of new hybrid states—polaritons—that are part light and part matter in character. A key signature of this strong coupling is an anti-crossing of the exciton and surface plasmon modes on a dispersion diagram. In a recent report on strong coupling between the plasmon modes of a small silver nano-rod and a molecular dye, it was shown that when the oscillator strength of the exciton is large enough, an additional anti-crossing feature may arise in the spectral region where the real part of the permittivity of the excitonic material is zero. However, the physics behind this double anti-crossing feature is still unclear. Here, we make use of extensive transfer matrix simulations to explore this phenomenon. We show that for low oscillator strengths of the excitonic resonance, there is a single anti-crossing arising from strong coupling between the surface plasmon and the excitonic resonance, which is associated with the formation of upper and lower plasmon–exciton polaritons. As the oscillator strength is increased, we find that a new mode emerges between these upper and lower polariton states and show that this new mode is an excitonic surface mode. Our study also features an exploration of the role played by the orientation of the excitonic dipole moment and the relationship between the modes we observe and the transverse and longitudinal resonances associated with the excitonic response. We also investigate why this type of double splitting is rarely observed in experiments. [ABSTRACT FROM AUTHOR]

Time-resolved spontaneous and laser-induced unimolecular fragmentation of perylene cations (C20H12+) has been measured on timescales up to 2 s in a cryogenic electrostatic ion beam storage ring. We elaborate a quantitative model, which includes fragmentation in competition with radiative cooling via both vibrational and electronic (recurrent fluorescence) de-excitation. Excellent agreement with experimental results is found when sequential fragmentation of daughter ions co-stored with the parent perylene ions is included in the model. Based on the comparison of the model to experiment, we constrain the oscillator strength of the D1 → D0 emissive electronic transition in perylene (fRF = 0.055 ± 0.011), as well as the absolute absorption cross section of the D5 ← D0 excitation transition (σabs > 670 Mb). The former transition is responsible for the laser-induced and recurrent fluorescence of perylene, and the latter is the most prominent in the absorption spectrum. The vibrational cooling rate is found to be consistent with the simple harmonic cascade approximation. Quantitative experimental benchmarks of unimolecular processes in polycyclic aromatic hydrocarbon ions like perylene are important for refining astrochemical models. [ABSTRACT FROM AUTHOR]

Using a synchrotron-based Fourier-transform spectrometer, the high-resolution absorption spectra of the C1-symmetric 2,3-dihydrofuran (23DHF) and C2v-symmetric 2,5-dihydrofuran (25DHF) have been measured from 5.5 eV to 9.4 eV with an absolute absorption cross section scale. Oscillator strengths and vertical excitation energies of the lowest 18 states have been computed using the average of the second- and third-order algebraic diagrammatic construction polarization propagator method and the equation-of-motion coupled-cluster method at the level of singles and doubles model. These show that the bright valence transitions of ππ*-character are embedded into Rydberg transitions, whose oscillator strengths are at least one order of magnitude lower. To account for intensity borrowing, the first broad valence transition between 5.5 eV and 6.8 eV was simulated using a nuclear ensemble, and the agreement between experiment and theory is excellent. Whereas 23DHF only exhibits one broad valence transition followed by d/f Rydberg series converging to the ionization energy, the absorption spectrum of 25DHF has four bands, attributed to a valence nπσ → π*-transition, nπσ → 3px,z/3dxz transitions, a second valence nπ → π*-transition followed by d/f Rydberg series converging to the ionization energy, respectively. All Rydberg series converging to the ionization energy have been characterized in terms of their quantum defects. [ABSTRACT FROM AUTHOR]

Experimental, theoretical, and additive-model photoabsorption cross sections combined with constraints provided by the Kuhn–Reiche–Thomas sum rule and the high-energy behavior of the dipole oscillator strength density are used to construct dipole oscillator strength distributions for benzene, pyridazine (1,2-diazine), pyrimidine (1,3-diazine), pyrazine (1,4-diazine), s-triazine (1,3,5-triazine), toluene (methylbenzene), hexafluorobenzene, and nitrobenzene. The distributions are used to predict dipole sum rules S(k) for −6 ≤ k ≤ 2, mean excitation energies I(k) for −2 ≤ k ≤ 2, and isotropic van der Waals C6 coefficients. A popular combination rule for estimating C6 coefficients for unlike interactions from the C6 coefficients of the like interactions is found to be accurate to better than 1% for 606 of 628 cases (96.4%) in the test set. [ABSTRACT FROM AUTHOR]

This study experimentally analyzes the cessation of self-sustained periodic oscillations of gas columns in delay-coupled Rijke tube oscillators. The Rijke tube oscillator comprised an open-ended resonance tube with a Bunsen burner inserted into it. Delay coupling was introduced using acoustic waves propagating through a gas-filled tube with both ends connected to the resonance tubes. Two coupling methods, single- and double-tube coupling, were tested for comparison. A significant reduction in the acoustic amplitude was observed with relatively narrow tubes in double-tube coupling when the tube lengths were equal to half the wavelength and one wavelength of the acoustic waves of the uncoupled oscillator. The experimental results were analyzed using the theoretical model of the delay-coupled Rijke tube oscillators, whose coupling strength varied with the delay time. The present results would be useful in establishing a simple method for suppressing unwanted acoustic oscillations observed in various combustors. [ABSTRACT FROM AUTHOR]

Alloys between group III nitrides and the corresponding heterovalent II-IV-N2 compounds have recently been proposed as a further way of tuning the properties of nitride semiconductors. At 50% composition, a new ordered compound with composition ZnGeGa2N4 and space group Pmn21 was found, which has the lowest energy among wurtzite based structures. This structure obeys the local octet rule that every N is surrounded by two Ga, one Zn, and one Ge, ensuring local charge neutrality. Here, we investigate the vibrational properties of this new compound and provide predictions for its related infrared and Raman spectra, which may become useful for the characterization of this material. A group theoretical analysis, phonon frequencies and related Born effective charges, dielectric constants, infrared oscillator strengths, and Raman tensors are presented. Polarized infrared and Raman spectra for different scattering geometries are presented, as well as the phonon band structure and density of states. [ABSTRACT FROM AUTHOR]

Alloys between group III nitrides and the corresponding heterovalent II-IV-N2 compounds have recently been proposed as a further way of tuning the properties of nitride semiconductors. At 50% composition, a new ordered compound with composition ZnGeGa2N4 and space group Pmn21 was found, which has the lowest energy among wurtzite based structures. This structure obeys the local octet rule that every N is surrounded by two Ga, one Zn, and one Ge, ensuring local charge neutrality. Here, we investigate the vibrational properties of this new compound and provide predictions for its related infrared and Raman spectra, which may become useful for the characterization of this material. A group theoretical analysis, phonon frequencies and related Born effective charges, dielectric constants, infrared oscillator strengths, and Raman tensors are presented. Polarized infrared and Raman spectra for different scattering geometries are presented, as well as the phonon band structure and density of states. [ABSTRACT FROM AUTHOR]

Strong Coulomb interaction in atomically thin transition metal dichalcogenides makes these systems particularly promising for studies of excitonic physics. Of special interest are the manifestations of the charged excitons, also known as trions, in the optical properties of two-dimensional semiconductors. In order to describe the optical response of such a system, the exciton interaction with resident electrons should be explicitly taken into account. In this paper, we demonstrate that this can be done in both the trion (essentially, few-particle) and Fermi-polaron (many-body) approaches, which produce equivalent results, provided that the electron density is sufficiently low and the trion binding energy is much smaller than the exciton one. Here, we consider the oscillator strengths of the optical transitions related to the charged excitons, fine structure of trions, and Zeeman effect, as well as photoluminescence of trions illustrating the applicability of both few-particle and many-body models. [ABSTRACT FROM AUTHOR]

Monolayers of transition metal dichalcogenides present an intriguing platform to investigate the interplay of excitonic complexes in two-dimensional semiconductors. Here, we use optical spectroscopy to study the light–matter coupling and non-equilibrium relaxation dynamics of three-particle exciton states, commonly known as trions. We identify the consequences of the exchange interaction for the trion fine structure in tungsten-based monolayer materials from variational calculations and experimentally determine the resulting characteristic differences in their oscillator strength. It allows us to quantitatively extract trion populations from time-resolved photoluminescence measurements and monitor their dynamics after off-resonant optical injection. At liquid helium temperature, we observe a pronounced non-equilibrium distribution of the trions during their lifetime with comparatively slow equilibration that occurs on time-scales up to several hundreds of ps. In addition, we find an intriguing regime of population inversion at lowest excitation densities, which builds up and is maintained for tens of picoseconds. At a higher lattice temperature, the equilibrium is established more rapidly and the inversion disappears, highlighting the role of thermal activation for efficient scattering between exchange-split trions. [ABSTRACT FROM AUTHOR]

We present three schemes to go beyond the electric-dipole approximation in x-ray absorption spectroscopy calculations within a four-component relativistic framework. The first is based on the full semi-classical light–matter interaction operator and the two others on a truncated interaction within the Coulomb gauge (velocity representation) and multipolar gauge (length representation). We generalize the derivation of the multipolar gauge to an arbitrary expansion point and show that the potentials corresponding to different expansion points are related by a gauge transformation, provided that the expansion is not truncated. This suggests that the observed gauge-origin dependence in the multipolar gauge is more than just a finite-basis set effect. The simplicity of the relativistic formalism enables arbitrary-order implementations of the truncated interactions, with and without rotational averaging, allowing us to test their convergence behavior numerically by comparison to the full formulation. We confirm the observation that the oscillator strength of the electric-dipole allowed ligand K-edge transition of TiCl4, when calculated to the second order in the wave vector, becomes negative but also show that inclusion of higher-order contributions allows convergence to the result obtained using the full light–matter interaction. However, at higher energies, the slow convergence of such expansions becomes dramatic and renders such approaches at best impractical. When going beyond the electric-dipole approximation, we therefore recommend the use of the full light–matter interaction. [ABSTRACT FROM AUTHOR]

The eT program is an open source electronic structure package with emphasis on coupled cluster and multilevel methods. It includes efficient spin adapted implementations of ground and excited singlet states, as well as equation of motion oscillator strengths, for CCS, CC2, CCSD, and CC3. Furthermore, eT provides unique capabilities such as multilevel Hartree–Fock and multilevel CC2, real-time propagation for CCS and CCSD, and efficient CC3 oscillator strengths. With a coupled cluster code based on an efficient Cholesky decomposition algorithm for the electronic repulsion integrals, eT has similar advantages as codes using density fitting, but with strict error control. Here, we present the main features of the program and demonstrate its performance through example calculations. Because of its availability, performance, and unique capabilities, we expect eT to become a valuable resource to the electronic structure community. [ABSTRACT FROM AUTHOR]

Dielectric and conducting properties of unintentionally doped bulk and Sn-doped thin film β - Ga 2 O 3 samples were studied using time-domain terahertz spectroscopy. Complex permittivity and optical conductivity spectra from 0.25 to 2.5 THz were obtained experimentally over a broad temperature range. The low-temperature spectra of the unintentionally doped sample were fit using a model involving two oscillators. The parameters of one of them show an unusual temperature dependence, in particular, a pronounced increase in the oscillator strength upon heating above 50 K. This is interpreted as an absorption due to thermally activated charge carriers moving in localized potential minima linked to the unintentional doping. Upon heating, the influence of this optical conductivity mechanism strongly increases, and the sample becomes opaque in the THz range near 100 K. The nanocrystalline Sn-doped Ga 2 O 3 thin film sample exhibits a much higher optical conductivity than the unintentionally doped bulk sample, and its spectra are remarkably stable over a broad temperature range (4–750 K). This first study of β - Ga 2 O 3 based on phase-sensitive THz spectroscopy reveals how the impurities influence the high-frequency conductive properties of the material. [ABSTRACT FROM AUTHOR]

We report the one-dimensional cuts of the six-dimensional potential energy surfaces (PESs) of the ground and lowest doublet and quartet electronic states of trans-HO3 at the MRCI-F12/aug-cc-pVTZ level of theory. Theoretical calculations predict that the first excited state (A2A) presents a real minimum on its PES and possesses a nonplanar structure. The adiabatic excitation energy at the MRCI+Q and MRCI-F12 levels shows that the A2A state lies in the near-infrared region. Both the transition dipole moment and the oscillator strength were predicted to be weak, which suggests that photodissociation of HO3 to produce OH and O2 after UV-Vis absorption is not a plausible mechanism. The harmonic vibrational frequencies and rotational constants of the weakly bound complex OH–O2 in the two electronic states were predicted to help in its detection. Our PES shows that the reactions of H + O3 or HO2 + O in their ground states do not lead to trans-HO3 in its ground electronic state if one of the component fragments, i.e., HO2(A2A′) + O(3P) or H(2S) + O3(3B2), is excited. [ABSTRACT FROM AUTHOR]

We report Tn ← T1 spectra and extinction coefficients, ε, and other properties as functions of chain length for a series of fluorene oligomers, oFn, and polymers, pFn, with n = 2–84 repeat units. We find that ε increases with length, peaking at 159 400 M−1 cm−1 for oF3 and then decreases for longer chains. ε does not scale with 1/n or e−n to reach a constant value at long length, as predicted by the commonly applied oligomer extrapolation approximation, although spectral shifts, oscillator strengths, and transition dipole moments do reach limiting values for chains near 10 units long. While computations describe the triplet in oF2 and oF3 as having similar geometries with a single flattened dihedral angle between units, computations and simulations suggest that in longer oligomers motion along the chains of the short 2–3 unit, the long T1 state is probably the source of the unusual changes in ε. These occur because hopping along the chain is sufficiently fast that the dihedrals between fluorene units cannot fully relax. At a length near 10 units, hopping and dihedral angle changes produce a steady state distribution of geometries with only small changes from the ground state, which persist for longer chains. Additional decreases in ε from pF28 to pF84 are plausibly due to a small number of chain defects which result in loss of triplets. [ABSTRACT FROM AUTHOR]

We present an analysis of quantum confinement of carriers and excitons, and exciton fine structure, in metal halide perovskite (MHP) nanocrystals (NCs). Starting with coupled-band k · P theory, we derive a nonparabolic effective mass model for the exciton energies in MHP NCs valid for the full size range from the strong to the weak confinement limits. We illustrate the application of the model to CsPbBr3 NCs and compare the theory against published absorption data, finding excellent agreement. We then apply the theory of electron-hole exchange, including both short- and long-range exchange interactions, to develop a model for the exciton fine structure. We develop an analytical quasicubic model for the effect of tetragonal and orthorhombic lattice distortions on the exchange-related exciton fine structure in CsPbBr3, as well as some hybrid organic MHPs of recent interest, including formamidinium lead bromide (FAPbBr3) and methylammonium lead iodide (MAPbI3). Testing the predictions of the quasicubic model using hybrid density functional theory (DFT) calculations, we find qualitative agreement in tetragonal MHPs but significant disagreement in the orthorhombic modifications. Moreover, the quasicubic model fails to correctly describe the exciton oscillator strength and with it the long-range exchange corrections in these systems. Introducing the effect of NC shape anisotropy and possible Rashba terms into the model, we illustrate the calculation of the exciton fine structure in CsPbBr3 NCs based on the results of the DFT calculations and examine the effect of Rashba terms and shape anisotropy on the calculated fine structure. [ABSTRACT FROM AUTHOR]

Context. Polycyclic aromatic hydrocarbons (PAHs) are believed to be the carriers of the aromatic infrared bands and have been proposed as candidates to explain other astronomical phenomena such as diffuse interstellar bands (DIBs). The first aromatic structures possessing more than one ring, 1- and 2-cyanonaphthalene (CNN), were recently detected by rotational spectroscopy in the dense molecular cloud TMC-1. Laboratory investigations have indicated that due to fast and efficient relaxation through recurrent fluorescence (RF), CNN+ may be photostable in the harsh conditions of the lower density, more diffuse regions of the interstellar medium (ISM) exposed to ultraviolet (UV) radiation. As a result, it has been suggested that the widely held belief that small PAHs present in these regions are dissociated may need to be revisited. If 1-CNN+ is able to survive in the diffuse ISM it may contribute to the population of 1-CNN observed in TMC-1. To investigate the abundance of 1-CNN+ in diffuse clouds, laboratory spectroscopy is required. The present work concerns the electronic spectroscopy of 1-CNN+ in absorption and the search for its spectroscopic fingerprints in diffuse clouds. Aims. The aim is to obtain laboratory data on the electronic transitions of gas-phase 1-CNN+ under conditions appropriate for comparison with DIBs and assess abundance in diffuse clouds. Methods. Spectroscopic experiments are carried out using a cryogenic ion trapping apparatus in which gas-phase 1-CNN+ is cooled to temperatures below 10 K through buffer gas cooling. Calculations are carried out using time-dependent density-functional theory. Results. Experimental and theoretical data on the D2 ← D0 and D3 ← D0 electronic transitions of 1-CNN+ are reported. The former transition has a calculated oscillator strength of f = 0.075 and possesses a pattern dominated by its origin band. The origin band is located at 7343 Å and has a full width at half maximum of 28 Å. In observational data, this falls in a region polluted by telluric water lines, hindering assessment of its abundance. Conclusions. Space-based observations are required to search for the spectroscopic signatures of 1-CNN+ and evaluate the hypothesis that this small aromatic system, stabilised by RF, may be able to survive in regions of the ISM exposed to UV photons. [ABSTRACT FROM AUTHOR]

Electron energy loss spectroscopy (EELS) is a well established technique in electron microscopy that yields information on the elemental content of a sample in a very direct manner. One of the persisting limitations of EELS is the requirement for manual identification of core-loss edges and their corresponding elements. This can be especially bothersome in spectrum imaging, where a large amount of spectra are recorded when spatially scanning over a sample area. This paper introduces a synthetic dataset with 736,000 labeled EELS spectra, computed from available generalized oscillator strength tables, that represents 107 K, L, M or N core-loss edges and 80 chemical elements. Generic lifetime broadened peaks are used to mimic the fine structure due to band structure effects present in experimental core-loss edges. The proposed dataset is used to train and evaluate a series of neural network architectures, being a multilayer perceptron, a convolutional neural network, a U-Net, a residual neural network, a vision transformer and a compact convolutional transformer. An ensemble of neural networks is used to further increase performance. The ensemble network is used to demonstrate fully automated elemental mapping in a spectrum image, both by directly mapping the predicted elemental content and by using the predicted content as input for a physical model-based mapping. [ABSTRACT FROM AUTHOR]

Studying the motor-control mechanisms of the brain is critical in academia and also has practical implications because techniques such as brain-computer interfaces (BCIs) can be developed based on brain mechanisms. Magnetoencephalography (MEG) signals have the highest spatial resolution (~3 mm) and temporal resolution (~1 ms) among the non-invasive methods. Therefore, the MEG is an excellent modality for investigating brain mechanisms. However, publicly available MEG data remains scarce due to expensive MEG equipment, requiring a magnetically shielded room, and high maintenance costs for the helium gas supply. In this study, we share the 306-channel MEG and 3-axis accelerometer signals acquired during three-dimensional reaching movements. Additionally, we provide analysis results and MATLAB codes for time-frequency analysis, F-value time-frequency analysis, and topography analysis. These shared MEG datasets offer valuable resources for investigating brain activities or evaluating the accuracy of prediction algorithms. To the best of our knowledge, this data is the only publicly available MEG data measured during reaching movements. [ABSTRACT FROM AUTHOR]

The present study reports the annealing induced structural as well as optical properties of Ag 2 S/As 2 Se 3 heterostructure film at different annealing temperatures. The trigonal AgAsSe 2 phase formation was confirmed from the X-ray diffraction (XRD) and selective area electron diffraction (SAED) study. The bandgap of as-prepared Ag 2 S/As 2 Se 3 film decreased on annealing. The reduction in bandgap increased the static refractive index with annealing. The Urbach energy increased from 422±3 meV to 464±2 meV whereas the optical density and extinction coefficient increased by annealing due to the formation of AgS–AsSe solid solution. The dispersion energy increased and consequently increased the oscillator wavelength and oscillator strength upon annealing. The carrier concentration and optical conductivity increased whereas the optical electronegativity decreased with annealing. The 3rd order nonlinear susceptibility (χ(3)) increased from 2.804x10−11 esu (as-prepared Ag 2 S/As 2 Se 3) to 5.132 x10−11 esu upon annealing at 200 °C. The n 2 value increased upon annealing which increased the nonlinear absorption coefficient but decreased the figure-of-merit. The contact angle value decreased (93°–47.6°) that shows the transformation of hydrophobicity to hydrophilic nature which is good for sensor applications like biological sensor. The surface roughness decreased upon annealing. The change in optical parameters upon annealing makes them the appropriate candidate for optoelectronics, dielectric and nonlinear optical applications such as memory devices, optical switch, etc. [Display omitted] [ABSTRACT FROM AUTHOR]

Context: Heavy metal ion removal from wastewater has become a global concern due to its extensive negative effects on human health and the environment. The density functional theory is employed to investigate the possibility of removing Pb2+, Hg2+, and Cd2+ ions from wastewater using nano-graphene. Researchers have shown that NG can efficiently remove heavy metals from media. Additionally, it was shown that the adsorption of Pb2+, Hg2+, and Cd2+ ions might reduce the large pristine NG (HOMO–LUMO) gap. Methods: HSE06 may accurately represent NG electrical characteristics. The DFT-D3 method was also used to account for Van der Waals interactions in the present study. The results demonstrated that charge transfer and binding energy remained greater in cation-NG systems with greater electron transfer rates. Pb2+, Hg2+, and Cd2+ adsorption results indicated that Egap was significantly reduced by 68%, 15%, and 21%, respectively. The Pb2+@NG complex exhibited the strongest oscillator strength. This may be explained by the enormous occupation number difference between the 2px orbital of the C atoms and the 6 s orbital of the Pb2+ cations. The greater Ebin value of Pb2+@NG is consistent with the increased predicted redshifts (199 nm). DFT (hybrid functional HSE06) studies that rely on time showed that the relevant complexes have "ligand-to-metal charge transfer" excitations. In general, it was found that Pb2+@NG had the greatest k value, binding energy, redshifts, and charge transfer rate among the complexes. The theoretical insights of this study may influence experimental efforts to identify NG-based compounds that are effective and efficient at removing pollutants from wastewater. [ABSTRACT FROM AUTHOR]

Context: The dye-sensitized solar cell is a technology unique in its light conversion properties as it operates with record efficiencies in diffused light conditions. The choice of the appropriate sensitizer is one of the important strategies to improve photovoltaic performance of DSSC devices. This theoretical study mainly aims to determine the impact of the π-spacer on the geometric and optoelectronic parameters of sensitizer dyes. For that, we have chosen six organic dyes of Donor-π-Acceptor structure based on triphenylamine unit as electron donor, cyanoacrylic acid as electron acceptor with various π-bridges. The results indicated that the doping process modify dihedral angles and electronic properties by enhancing the planarity and decreasing the gap energy. We have examined the optoelectronic and photovoltaic properties of studied triphenylamine based-dyes. Introducing thiophene and furan as π-spacer groups in D6 dye can effectively decrease the gap energy (Egap = 2.21 eV), broaden the absorption range (λmax = 671.19 nm), and promote the light-harvesting properties. The D2 dye based on two pyrrole units presents an improved electron injection driving force (ΔGinject = − 2.269 eV) and regeneration driving force corresponding to better charge separation. The π-bridge groups can efficiently tune the optoelectronic and photovoltaic properties of sensitizers, which contribute to the efficiency of solar cells. Methods: The geometrical and electronic properties of all systems were studied by the DFT method using the correlation exchange functional B3LYP combined with 6-31G(d, p) basis set. On the other hand, the maximum absorption wavelengths λmax and the corresponding oscillator strengths were calculated using the hybrid functional BHandHLYP and 6-31+G(d) basis set. The solvent tetrahydrofuran (THF) are used to study the effect of the solvent, using the "Conductor-Polarizable Continuum" (C-PCM) model. All calculations were performed using Gaussian 09 program. [ABSTRACT FROM AUTHOR]

In an astrochemical and environmental context, this work constitutes a step forward in understanding the photo-reactivity of polycyclic aromatic hydrocarbons (PAHs) with water molecules and in water ice under irradiation with low energy photons. The role of charge transfer states PAH + -H 2 O - has been proposed, motivating the study of the electronic excited states up to about 6 eV of planar and bowl-shaped PAHs, namely pyrene C 16 H 10 and corannulene C 20 H 10 , interacting with water clusters of different sizes and orientations, using a time-dependent density functional theory approach. In the case of pyrene, the systematic occurrence of low energy excitations from π orbitals to diffuse orbitals located on some water molecules, mixed with the Rydberg orbitals (R/wat), was found. Such excitations are more numerous and possess larger oscillator strengths when (i) the number of water molecules increases up to representing a first layer of hexagonal water ice and (ii) for the arrangements leading to the lower vertical ionization potential values. In this case, the /wat orbitals are located on the most external H atoms and they may also mix with π ⋆ orbitals. This accounts for the efficient reactivity of pyrene with water in water ice. In the case of corannulene, the main result is that, for the C 20 H 10 (H 2 O) 3 isomer formed in a noble gas matrix, where (H 2 O) 3 interacts with the concave face of corannulene, no π → R/wat transition is observed. It is in line with the lack of reactivity of corannulene with water in a noble gas matrix. [ABSTRACT FROM AUTHOR]

Nd3+-activated CdO–V 2 O 5 –ZnO–B 2 O 3 (CVZB) inverted glasses with chemical composition of 80–5.0-2.5–12.5 mol%, respectively, were prepared by melt-quenching to analyze their optical spectroscopy features by applying the Judd-Ofelt (JO) theory. The Nd3+ content was changed from 0.4 up to 4.0 mol%. The structural characterization carried out by X-ray diffraction patterns and Raman spectroscopy, confirmed the amorphous nature for doping contents up to 4.0 mol% of Nd3+. The direct (E g d i r ) and indirect (E g i n d ) band gap obtained from the absorption spectra, showed values of 2.76 ± 0.12 and 2.50 ± 0.10 eV, respectively, without significative changes by the Nd3+ doping variations. Such band gap energy values are suitable to allow the Nd3+ emissions centered at 878, 1060 and 1332 nm, corresponding to the 4F 3/2 → 4I 9/2 , 11/2 , 13/2 transitions, respectively. The Nd3+ emission intensity reached the optimum at 2.8 mol% of Nd3+. At larger Nd3+ concentrations, the emission is gradually quenched due to cross-relaxation processes. These processes were dominated by electric dipole-dipole interactions within Nd3+-Nd3+ clusters, as suggested by the Inokuti-Hirayama model and critical interaction distance. The experimental branching ratios (β exp) were stables up to 1130 mW of 808 nm laser excitation, with values of (4F 3/2 → 4I 9/2) β exp = 0.28, (4F 3/2 → 4I 11/2) β exp = 0.56, and (4F 3/2 → 4I 13/2) β exp = 0.16. The JO parameters for the optimal emitting glass (2.8 mol% of Nd3+) obtained from least-square fitting between theoretical (f cal) and experimental (f exp) oscillator strengths, were Ω 2 = 5.31 × 10−20, Ω 4 = 2.81 × 10−20 and Ω 6 = 3.34 × 10−20 cm2. The stimulated cross-section peak (σ p), obtained from the JO parameters, resulted to be σ p = 1.21 × 10−20 and 3.50 × 10−20 cm2 for the 4F 3/2 → 4I 9/2 and 4F 3/2 → 4I 11/2 transitions, respectively. The radiative (τ R) and experimental (τ exp) lifetimes led to quantum yield value of 0.49. Finally, laser parameters for the 4F 3/2 → 4I 11/2 emission, such as bandwidth (σ P EMI × Δλ em) and optical gain (σ P EMI × τ R) were calculated from the emission cross-section peak (σ P EMI , 1061 nm), resulting values of 165 × 10−27 cm3 and 37 × 10−25 cm2s, respectively. [ABSTRACT FROM AUTHOR]

Recently, interlayer and intralayer excitons in transition metal dichalcogenide heterobilayers have been studied both experimentally and theoretically. In spite of a growing interest, these layer-resolved excitons in the presence of external stimuli, such as strain, remain not fully understood. Here, using density-functional theory calculations with many-body effects, we explore the excitonic properties of vertically stacked MoSe2/WSe2 heterobilayer in the presence of in-plane biaxial strain of up to 5%. We calculate the strain dependence of exciton absorption spectrum, oscillator strength, wave function, and binding energy by solving the Bethe–Salpeter equation on top of the standard GW approach. We identify the interlayer and intralayer excitons by analyzing their electron-hole weights and spatial wave functions. We show that with the increase in strain magnitude, the absorption spectrum of the interlayer and intralayer excitons is red-shifted and re-ordered, and the binding energies of these layer-resolved excitons decrease monotonically and almost linearly. We derive the sensitivity of exciton binding energy to the applied strain and find that the intralayer excitons are more sensitive to strain than the interlayer excitons. For instance, a sensitivity of −7.9 meV/% is derived for the intra-MoSe2-layer excitons, which is followed by −7.4 meV/% for the intra-WSe2-layer excitons, and by −4.2 meV/% for the interlayer excitons. Our results indicate that interlayer and intralayer excitons in vertically stacked MoSe2/WSe2 heterobilayer are efficiently tunable by in-plane biaxial strain. [ABSTRACT FROM AUTHOR]

The interaction of plasmonic whispering gallery modes on the surface of silver nanospheres with an exciton of the surrounding organic medium has been theoretically studied. DPAVBi (4,4'-bis[4-(di-ptolylamino) styryl]biphenyl) was selected as an organic material due to its high oscillator strength. The results show that for spheres of sufficiently large radii, several plasmon modes can be localized on their surface at once, which makes them possible for strong coupling with an exciton. The calculated spectra confirm that plasmon modes can effectively interact with excitons in the surrounding organic material, which leads to a significant change in both the absorption and emission characteristics of the system. These observations highlight the potential of such hybrid systems for a number of applications in optoelectronics and photonics, making them a promising platform for further research in this area. [ABSTRACT FROM AUTHOR]

Absolute differential and integral cross sections (DCSs and ICSs) for the lowest-lying singlet excitations in ammonia (NH3) molecules have been measured from near threshold to 400 eV using angle-revolved electron energy loss spectroscopy. Normalizing the angular distributions of inelastically scattered electrons to the absolute DCS of He as the reference, the reliable absolute cross sections for the A ~ 1 A ″ 2 excitation were obtained in a wider impact energy range. The BEf-scaled ICS was also derived as a function of incident electron energy from the generalized oscillator strengths analysis using the corresponding DCS measured at higher impact energies. The experimental ICS of the singlet excitation in the present study has reasonably reproduced the BEf-scaled ICS in the energy of not only higher impact energies but also near the threshold energy within the experimental uncertainties. The present absolute measurement has suggested that the BEf-scaling law was confirmed to be quite useful to NH3 molecules even towards the threshold energy. [ABSTRACT FROM AUTHOR]

An interesting chiral molecule with a double half-twisted π-electron system has been investigated with theoretical calculations. To investigate the geometry and electronic structure, the size of macrocyclic cavity, electrostatic potential (ESP) and density-of-states (DOS) were calculated. The multi-center bond order (MCBO) and AV1245 index were calculated to compare the aromaticity of phenylene groups. To investigate the spectroscopic properties, Raman, Raman Optical Activity (ROA), UV–Vis spectrum, fluorescence, CPL (circularly polarized luminescence) and ECD (electronic circular dichroism) spectra have been calculated and analyzed. The oscillator strengths, rotatory strengths and dissymmetry factor (glum) have been discussed. [ABSTRACT FROM AUTHOR]

A rapid filtration test method that predicts malt filtration efficiency has been developed in this research. This rapid filtration test method has an advantage over existing beer filtration tests, as it can be easily operated and there is no need to brew. Six kinds of malts with distinct filtration performance were selected, and the filtration performance was determined by measuring the turbidity of their clarified wort through simple simulation of mashing. The results indicate the filtering performance ranking as given: Copeland > Pearl malt 1 > Pearl malt 2 > Synergy > Planet > Wheat malt. When a sample is purchased for six times of parallelization, RSD is less than 10%, and the experimental results are significantly correlated with viscosity and β-glucan content. Therefore, this method can effectively predict the filtration performance of malt. The response surface design 3 × 3 factor experiment was used to optimize the fast detection method, which increased the sample differentiation (F-value) and made it easier to judge the experimental results. Response surface experiment results show the optimal reaction conditions for enhancing differentiation, i.e., an enzyme ratio of 0.5 (α-amylase, β-glucanase, neutral protease = 1:2:1), a holding period of 38 min, and a reaction temperature of 44 °C. The F-value is 147.00. [ABSTRACT FROM AUTHOR]

The exponentially correlated Hylleraas–configuration interaction method (E-Hy-CI) is a generalization of the Hylleraas–configuration interaction method (Hy-CI) in which the single r i j of an Hy-CI wave function is generalized to a form of the generic type r i j ν i j e − ω i j r i j . This work continues the exploration, begun in the first two papers in this series (on the helium atom and on ground and excited S states of Li II), of whether wave functions containing both linear and exponential r i j factors converge more rapidly than either one alone. In the present study, we examined not only 1 s 2   1 S states but 1s2p  1 P states for the He I, Li II, Be III, C V and O VII members of the He isoelectronic sequence as well. All 1 P energies except He I are better than previous results. The wave functions obtained were used to calculate oscillator strengths, including upper and lower bounds, for the He-sequence lowest (resonance) 1 S → 1 P transition. Interpolation techniques were used to make a graphical study of the oscillator strength behavior along the isoelectronic sequence. Comparisons were made with previous experimental and theoretical results. The results of this study are oscillator strengths for the 1 s 2   1 S → 1s2 p 1 P He isoelectronic sequence with rigorous non-relativistic quantum mechanical upper and lower bounds of (0.001–0.003)% and probable precision ≤ 0.0000003, and were obtained by extending the previously developed E-Hy-CI formalism to include the calculation of transition moments (oscillator strengths). [ABSTRACT FROM AUTHOR]

Nonlinear interactions between excitons strongly coupled to light are key for accessing quantum many-body phenomena in polariton systems. Atomically-thin two-dimensional semiconductors provide an attractive platform for strong light-matter coupling owing to many controllable excitonic degrees of freedom. Among these, the recently emerged exciton hybridization opens access to unexplored excitonic species, with a promise of enhanced interactions. Here, we employ hybridized interlayer excitons (hIX) in bilayer MoS2 to achieve highly nonlinear excitonic and polaritonic effects. Such interlayer excitons possess an out-of-plane electric dipole as well as an unusually large oscillator strength allowing observation of dipolar polaritons (dipolaritons) in bilayers in optical microcavities. Compared to excitons and polaritons in MoS2 monolayers, both hIX and dipolaritons exhibit ≈ 8 times higher nonlinearity, which is further strongly enhanced when hIX and intralayer excitons, sharing the same valence band, are excited simultaneously. This provides access to an unusual nonlinear regime which we describe theoretically as a mixed effect of Pauli exclusion and exciton-exciton interactions enabled through charge tunnelling. The presented insight into many-body interactions provides new tools for accessing few-polariton quantum correlations. In semiconductors, accessing nonlinear interactions between excitons strongly coupled to light will be key for quantum technologies. Here, in atomic bilayers of MoS2, new types of excitons are discovered showing strong inter-excitonic interactions. [ABSTRACT FROM AUTHOR]

The development of light‐absorbing organic molecules with calculated oscillator strength (f) is widely investigated to improve the performances of organic photoelectric devices such as organic photodiodes (OPDs). The oscillator strength estimates the probability of radiative electronic transition of a single molecule. However, most photoelectric devices are composed of organic thin films rather than a single organic molecule. Herein, the molecular volume is considered the critical parameter for the design of organic molecules. Three novel organic molecules, Et‐H, Me‐Me, and Me‐H, with similar oscillator strengths and different molecular volumes, are designed and synthesized as proof‐of‐concept. Their experimental absorption properties and organic photodiode performances are investigated. Me‐H, which has the smallest molecular volume and highest molecular packing density, shows the highest absorption coefficient in organic thin films and the best OPD performance with the highest external quantum efficiency. [ABSTRACT FROM AUTHOR]