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Stepwise two-photon absorption processes have received considerable attention, especially in photocatalysis, due to their relatively lower power threshold, characteristic spatial selectivity, amplification of chemical reactions, and so on. Meanwhile, studies on the relaxation dynamics of higher excited states in condensed systems have been limited for several molecular systems due to the short-lived nature of these states. In this study, we synthesized perylene-substituted perylene bisimide (PBI) and its derivate as model compounds and investigated their excited-state dynamics, including higher excited states, using pump–repump–probe spectroscopy. We revealed that these molecules form charge-transfer (CT) states instantaneously after the excitation, regardless of whether it is the perylene moiety or the PBI moiety that is excited. The lifetime of the CT state was shorter when the distance between the donor (perylene) and the acceptor (PBI) was shorter. Moreover, we also revealed that a higher-lying CT state generated by the stepwise excitation of the CT state using a 740-nm pulse induced Stark effect to the neighboring perylene moiety. The Stark effect not only gives more detailed information about the CT state, but also presents the possibility of new photofunctions, such as instantaneous modulation of the electronic state to achieve optimal electronic properties. These insights contribute to understanding advanced photochemical reactions and would be important for exploring photocatalytic reactions involving higher excited states. [ABSTRACT FROM AUTHOR]

A relativistic magnetic hyperfine interaction Hamiltonian based on the Douglas–Kroll–Hess (DKH) theory up to the second order is implemented within the ab initio multireference methods, including spin–orbit coupling in the Molcas/OpenMolcas package. This implementation is applied to calculate relativistic hyperfine coupling (HFC) parameters for atomic systems and diatomic radicals with valence s or d orbitals by systematically varying active space size in the restricted active space self-consistent field formalism with restricted active space state interaction for spin–orbit coupling. The DKH relativistic treatment of the hyperfine interaction reduces the Fermi contact contribution to the HFC due to the presence of kinetic factors that regularize the singularity of the Dirac delta function in the nonrelativistic Fermi contact operator. This effect is more prominent for heavier nuclei. As the active space size increases, the relativistic correction of the Fermi contact contribution converges well to the experimental data for light and moderately heavy nuclei. The relativistic correction, however, does not significantly affect the spin-dipole contribution to the hyperfine interaction. In addition to the atomic and molecular systems, the implementation is applied to calculate the relativistic HFC parameters for large trivalent and divalent Tb-based single-molecule magnets (SMMs), such as Tb(III)Pc2 and Tb(II) ( C p iPr 5 ) 2 without ligand truncation using well-converged basis sets. In particular, for the divalent SMM, which has an unpaired valence 6s/5d hybrid orbital, the relativistic treatment of HFC is crucial for a proper description of the Fermi contact contribution. Even with the relativistic hyperfine Hamiltonian, the divalent SMM is shown to exhibit strong tunability of HFC via an external electric field (i.e., strong hyperfine Stark effect). [ABSTRACT FROM AUTHOR]

Given the extensive use of fluorination in molecular design, it is imperative to understand the solvation properties of fluorinated compounds and the impact of the C–F bond on electrostatic interactions. Vibrational spectroscopy can provide direct insights into these interactions by using the C–F bond stretching [v(C–F)] as an electric field probe through the vibrational Stark effect (VSE). In this work, we explore the VSE of the three basic patterns of aliphatic fluorination, i.e., mono-, di-, and trifluorination in CF, CF2, and CF3 groups, respectively, and compare their response to the well-studied aromatic v(C–F). Magnitudes (i.e., Stark tuning rates) and orientations of the difference dipole vectors of the v(C–F)-containing normal modes were determined using density functional theory and a molecular dynamics (MD)-assisted solvatochromic analysis of model compounds in solvents of varying polarity. We obtain Stark tuning rates of 0.2–0.8 cm−1/(MV/cm), with smallest and largest electric field sensitivities for CFaliphatic and CF3,aliphatic, respectively. While average electric fields of solvation were oriented along the main symmetry axis of the CFn, and thus along its static dipole, the Stark tuning rate vectors were tilted by up to 87° potentially enabling to map electrostatics in multiple dimensions. We discuss the influence of conformational heterogeneity on spectral shifts and point out the importance of multipolar and/or polarizable MD force fields to describe the electrostatics of fluorinated molecules. The implications of this work are of direct relevance for studies of fluorinated molecules as found in pharmaceuticals, fluorinated peptides, and proteins. [ABSTRACT FROM AUTHOR]

A wire-on-well (WoW) structure was fabricated using InGaAs/GaAs/GaAsP superlattice device growth technology. This structure modifies the local concentration of carriers in the quantum well and lengthens the carrier lifetime to increase carrier transport efficiency. However, the reason for this remains unclear. Therefore, we investigated the detailed carrier transition properties using photoluminescence (PL) and photoreflectance measurements. Regarding the PL spectra at 4 K, two characteristic peaks at 1.39 and 1.34 eV were observed. Both transitions are attributed to the recombination between the first quantum level of the electron (e1) and that of the heavy hole (hh1). We also discussed the carrier distribution in the WoW structure and found that the maximum carrier existing probabilities for e1 and hh1 are located at different positions. The less overlapping of the wavefunctions causes low transition probability and results in the observed long carrier lifetime. An additional prominent result in the WoW structure is the blue shift attributed to the 1.34 eV PL peak induced by increasing laser excitation power. We found that the blue shift occurred by the screening of the electric field caused by the compressive strain, as in the case of the quantum-confined Stark effect. [ABSTRACT FROM AUTHOR]

Recent advances in Rydberg-atom electrometry detail promising applications in radio frequency communications. Presently, most applications use carrier frequencies greater than 1 GHz where resonant Autler–Townes splitting provides the highest sensitivity. This letter documents a series of experiments with Rydberg atomic sensors to collect and process waveforms from the automated identification system (AIS) used in maritime navigation in the very high frequency (VHF) band. Detection in this band is difficult with conventional resonant Autler–Townes based Rydberg sensing and requires a new approach. We show the results of a method called high angular momentum matching excited Raman (HAMMER), which enhances low frequency detection and exhibits superior sensitivity compared to the traditional AC Stark effect. From measurements of electromagnetically induced transparency in rubidium and cesium vapor cells, we show the relationship between incident electric field strength and observed signal-to-noise ratio and find that the sensitivity of the HAMMER scheme in rubidium achieved an equivalent single VHF tone sensitivity of 100 μ V / m / Hz . With these results, we estimate the usable range of the atomic vapor cell antenna for AIS waveforms given current technology and detection techniques. [ABSTRACT FROM AUTHOR]

The polarization-induced quantum confined Stark effect has been recognized as a significant factor contributing to the Internal Quantum Efficiency (IQE) droop in light-emitting diodes (LEDs). This study focuses on the design of LEDs by investigating the InAlN/AlGaN interface. By incorporating InAlN quantum wells, a polarization-matched (PM) multi-quantum well (MQW) LED architecture was developed. While the flat conduction and valence bands on PM MQWs indicate an improved recombination rate, it is crucial to examine the impact on IQE, considering carrier confinement and injection efficiency influenced by the band offsets. This paper presents a numerical analysis comparing two LEDs emitting at 245 and 275 nm, respectively. The results demonstrate that the PM LED operating at 275 nm exhibits enhanced performance, benefiting from high probability density overlap. Conversely, the PM LED emitting at 245 nm demonstrates poor confinement, resulting in an overall low performance, regardless of polarization matching. [ABSTRACT FROM AUTHOR]

This Letter focuses on the discharge mechanisms of an atmospheric pressure micro-plasma jet optimized for endoscopic applications in biology and medicine. This capacitively coupled plasma (CCP) features a concentric double flow allowing for shielding the Helium or Neon plasma gas with carbon dioxide from the humid ambient air. High-resolution optical emission spectroscopy allows for the analyses of the Stark effect of the He I 492.19 nm and the Hydrogen Hβ lines to determine the electric field (EF) and the electron density spatially resolved along the discharge expansion outside the source. EF in Neon at atmospheric pressure was reliably determined with the Stark shift measurement of the weak Ne I line at 515.196 nm. In both gases, the EF diagnostic revealed a steep transition from CCP afterglow to streamer discharge with a magnitude up to 30 kV/cm. This research is a significant step forward in the field of plasma medicine with a plasma source capable of delivering a reactive chemistry with or without an intense EF to the target. [ABSTRACT FROM AUTHOR]

Quasi‐2D perovskites are widely used in solar cells, photodetectors, and light‐emitting diodes (LEDs) due to their excellent optoelectronic properties and stability. However, much fewer all‐optical devices are realized based on quasi‐2D perovskites. Although perovskites have large nonlinear optical coefficients, the relaxation progress of excitons and carriers will slow down the response time and reduce the signal contrast of the all‐optical devices. In this paper, the exciton dynamics are investigated under off‐resonance excitation in quasi‐2D perovskite PEA2(FAPbBr3)2PbBr4. The spin‐selective optical Stark effect (OSE) is observed through circularly polarized transient absorption measurements, and a Stark shift of 3.3 meV is achieved under 1.11 eV excitation. The hot‐biexciton cooling process induced by two‐photon absorption is also observed. A spin‐based XNOR gate is demonstrated with a response time of ≈180 fs, and the logical signal contrast is enhanced through the competition of the OSE and the hot‐biexciton effect. [ABSTRACT FROM AUTHOR]

We demonstrate the continuous broadband microwave receivers based on AC Stark shifts and Floquet states of Rydberg levels in a cesium atomic vapor cell. The resonant transition frequency of two adjacent Rydberg states 78 S 1 / 2 and 78 P 1 / 2 is tuned based on AC Stark effect of 70 MHz radio frequency (RF) field that is applied outside the vapor cell. The use of the j = 1 / 2 Rydberg states ensures that only a single m j sublevel is involved. The generated Rydberg Floquet states act to enhance the sensitivity of the AC-Stark-tuned states when the frequency is matched and further extend the bandwidths. We achieve microwave field measurements with over 1.172 GHz continuous frequency tuning and a sensitivity ranging from 280.2 nVcm−1Hz−1/2 to 14.6 μ Vcm−1Hz−1/2. The achieving of continuous frequency and high sensitivity microwave detection will promote the application of Rydberg receivers in the radar technique and wireless communication. [ABSTRACT FROM AUTHOR]

GaInN/GaN multiple quantum shell (MQS) nanowires (NWs) are of great interest as high‐efficiency micro‐light emitting diodes (micro‐LEDs), mainly due to their quantum confined Stark effect suppression and dry etching insensitivity features. Herein, morphological and device properties corresponding to NW‐LEDs with different numbers of GaInN/GaN superlattices (SLs) are evaluated. The scanning electron microscopy measurements revealed that the polar‐plane MQS are shrunken, while the semipolar‐plane underwent expansion upon the introduction of the SLs. The current density–voltage–light output analysis at low current density indicates that samples with a greater number of SL pairs exhibit higher light output. Electroluminescence spectra show that NWs lacking SLs exhibit an emission wavelength of 700 nm, which is derived from indium‐rich clusters in polar‐plane MQS, whereas those with SLs emit at a significantly shorter wavelength of 560 nm. The reduction in the polar‐plane MQS coupled with the enhancement in MQS quality resulting from the SLs is identified as the primary contributing factor. Additionally, the external quantum efficiency factor for NW‐LEDs, which remained consistent even as the emission area decreased, is assessed. These findings suggest that NW‐LEDs with SLs possess the potential to mitigate the emission degradation associated with sidewall etching and realize high‐efficiency micro‐LEDs. [ABSTRACT FROM AUTHOR]

This article presents the effect of aluminium nitride (AlN) epilayer (EPL) growth rate on the growth of semipolar (11–22) InGaN/GaN light emitting diode (LED). Three samples are grown with different AlN EPL growth rates, which are low (L1, 1.0 nm s−1), intermediate (L2, 1.3 nm s−1), and high (L3, 1.6 nm s−1) growth rate. The root‐mean‐square (RMS) and peak‐to‐valley roughness show an increasing trend with the increasing AlN EPL growth rate which is attributed to an increment in indium composition as justified by the photoluminescence results. The sample with AlN EPL growth rate of 1.3 nm s−1 (L2) exhibits an outstanding crystal quality in terms of defect densities reduction, with a minimum basal stacking fault density of 1.60 × 104 cm−1 as calculated. Besides that, the obvious fringes of InGaN/GaN peaks observed in 2θ−ω scan proves that a high abruptness multi‐quantum well is attained. Sample L2 also shows a single peak profile in both photoluminescence and electroluminescence spectra with green wavelength emission of 506 and 537 nm, respectively, indicating a homogeneous indium composition. As the injection current is swept from 5 to 40 mA for sample L2, a weak blueshift of ≈6 nm is observed which indicates a reduction in quantum‐confined Stark effect (QCSE). [ABSTRACT FROM AUTHOR]

The fabrication of high‐performance microbial fuel cells requires the evaluation of the activity of electrochemically active bacteria. However, this is challenging because of the time‐consuming nature of biofilm formation and the invasive nature of labeling. To address this issue, we developed a fast, label‐free, single‐cell Raman spectroscopic method. This method involves investigating the “pure” linear Stark effect of endogenous CO in the silent region of biological samples, which allows for probing the intrinsic electric field in the outer‐membrane cytochromes of live bacterial cells. We found that reduced outer‐membrane cytochromes can generate an additional intrinsic electric field equivalent to an applied potential of +0.29 V. We also found that the higher the electrical activity of the cell, the larger the generated electric field. This was also reflected in the output current of the constructed microbial fuel cells. Raman spectroscopy was employed to facilitate the assessment of electrochemical activity at the single‐cell level in highly‐diluted bacterial samples. After analysis, inactive bacteria were ablated by laser heating, and 20 active cells were cultured for further testing. The rapid and high‐throughput probing of the intrinsic electric field offers a promising platform for high‐efficiency screening of electrochemically active bacterial cells for bioenergetic and photosynthetic research. [ABSTRACT FROM AUTHOR]

In this paper, we explore the dynamics of the global quantum discord (GQD) and quantum Fisher information (QFI) of a multipartite two-level stationary and moving atomic system under the Stark shift effect. The system interacts with a thermal field with a different number of average thermal photons. For a fixed Stark parameter value, the GQD magnitudes increase as the system size (N) increases for both static and moving atomic systems. However, in the instance of a stationary atomic system and lower Stark parameter values, the QFI preserves a constant magnitude for different N values. When atomic motion is taken, the quantifier dynamics exhibit periodic oscillations. Additionally, increasing the Stark parameter led to a suppression in the magnitude of both GQD and QFI. With in the sight of intrinsic decoherence (ID), the quantifiers show a damping in their oscillations. Interestingly, the atomic motion assists to mitigate the damping effects caused by ID. Moreover, if the average thermal photons are increased, the magnitude of the GQD and QFI are decreased. [ABSTRACT FROM AUTHOR]

Entangled in the push for modernity and securing frontiers, the young and rising mountains of the Himalayas bear stark witness to the effects of climate change and anthropogenic activities. Much of these effects are evident in the register of disasters, which displays horrific events. While popular media have increased its focus on climate change in this region, especially Uttarakhand, the emphasis has heavily relied on a techno-managerial aspect. Valuable these approaches may seem, they render the emotive and affective dimensions of disaster an appendix to the explanation. Drawing on scholarship on grief, I argue that grief is a structuring affect in the Himalayas that can politicise the Anthropocene as a generative framework to reveal historical inequalities. I show how it is politically urgent to emphasise grief when framing the story of disaster, not merely as a footnote but as the core element for portraying the plot of human suffering in public remembrance. I propose that a turn to the political in grief should emerge in the form of public witnessing and grievability. In demonstrating these claims, the paper approaches an unsettling account of disaster in the Raini village of Uttarakhand (India). Through this, the article centres on a normative dimension of climate change that often characterises a disaster as an 'eventful' register – invisibilising the affective contours of loss. [ABSTRACT FROM AUTHOR]

A set of two newly designed, single-channel Czerny–Turner spectrometers has been deployed at the DIII-D tokamak for measurements of the motional Stark effect (MSE) split beam emission and the C6+ (CVI) carbon charge exchange recombination (CER) emission at high spectral (δλ = 0.13 nm) and temporal (1–5 kHz) resolution. High throughput optics (f/# = 2.8) allow for good signal-to-noise at high time resolution using fast EMCCD detectors. The MSE emission allows for spectral fitting of the magnitude and direction of the local B-field, while the carbon emission yields local ion temperature and toroidal rotation information. To reduce so-called Doppler broadening of the MSE emission, a new channel-specific variable lens-masking approach has been developed. Experimental data collected from the 2023 DIII-D experimental campaign demonstrate the signal quality and instrument fidelity for both diagnostic measurements. Moreover, initial CER data analysis shows a clear evolution of the toroidal rotation during edge localized modes. Initial progress on the advanced MSE model, including a new validated ray-trace model of the DIII-D collection optics, is shown via sensitivity analysis. [ABSTRACT FROM AUTHOR]

The barrier effect of calcium silicate hydrate (C – S – H), which is secondarily formed around a repository owing to the utilization of cementitious materials, was explored. Eu was employed as a chemical analog of Am (a key radionuclide in high-level radioactive wastes), and its interaction with C – S – H was analyzed via synthesis experiments. For the experiments, calcium oxide, fumed silica, and a Eu solution were mixed to interact Eu with C – S – H that had not undergone drying. Fluorescence Raman spectroscopies were performed to analyze the coexistence of Eu with C – S – H. The results indicated that Eu was mostly undissolved in the liquid phase and that it was incorporated into the C – S – H structure rather than precipitated as its hydroxide species even at the pH conditions for Eu hydrolysis. Additionally, the C – S – H formation at 50°C, as well as its incorporation of Eu, were accelerated compared to 25°C. The findings indicated the possibility of immobilizing Eu and Am by C – S – H formed in the underground environment even under groundwater conditions in which Eu and Am form mobile colloids via the hydrolysis. [ABSTRACT FROM AUTHOR]

Controlling matter at the level of electrons using ultrafast laser sources represents an important challenge for science and technology. Recently, we introduced a general laser control scheme (the Stark control of electrons at interfaces or SCELI) based on the Stark effect that uses the subcycle structure of light to manipulate electron dynamics at semiconductor interfaces [A. Garzón-Ramírez and I. Franco, Phys. Rev. B 98, 121305 (2018)]. Here, we demonstrate that SCELI is also of general applicability in molecule–semiconductor interfaces. We do so by following the quantum dynamics induced by non-resonant few-cycle laser pulses of intermediate intensity (non-perturbative but non-ionizing) across model molecule–semiconductor interfaces of varying level alignments. We show that SCELI induces interfacial charge transfer regardless of the energy level alignment of the interface and even in situations where charge exchange is forbidden via resonant photoexcitation. We further show that the SCELI rate of charge transfer is faster than those offered by resonant photoexcitation routes as it is controlled by the subcycle structure of light. The results underscore the general applicability of SCELI to manipulate electron dynamics at interfaces on ultrafast timescales. [ABSTRACT FROM AUTHOR]

The decline in quantum efficiency observed in yellow-LEDs emitting wavelength around ∼575 nm, commonly known as the 'green-yellow gap', is predominantly influenced by the fact that high In-content In x Ga1− x N/GaN (x = 30%) yellow-multiple quantum wells (yellow-MQWs) are typically grown on GaN template. This configuration leads to substantial compressive stress, contributing to the structural defects and the significant quantum confined stark effect. To address this challenge, our strategy involves achieving superior lattice constant alignment within the yellow-MQWs by growing a pre-stress alleviation layer (PSAL) prior to the growth of yellow-MQWs. Our comprehensive theoretical study, coupled with numerical simulations, aimed to explore the impact of two distinct practical and commercially viable PSAL approaches: pre-quantum well, comprising short periods of InYGa1− Y N/GaN and pre-thin layer, incorporating a thin layer of In Z Ga1− Z N. Following a thorough analysis of these approaches, we propose an innovative improved optimized structure that demonstrates the highest internal quantum efficiency of 74.2%, minimal efficiency droop of 14.7% at 20 A cm−2, and a 20 nm favourable red-shift in electroluminescence characteristic with narrower full-width-half-maximum of 28 nm without any adverse effect on the pure yellow-color emission at 20 A cm−2. This advancement holds promise for providing better crystal quality and addressing the green-yellow gap issue in yellow-LED technology. [ABSTRACT FROM AUTHOR]

Single-photon emitters (SPEs) hold the key to many quantum technologies including quantum computing. In particular, developing a scalable array of identical SPEs can play an important role in preparing single photons – crucial resources for computation – at a high rate, allowing to improve the computational capacity. Recently, different types of SPEs have been found in various 2D materials. Towards realizing scalable SPE arrays in 2D materials for quantum computation, it is required to develop tunable SPEs that can produce identical photons by precisely controlling emission properties. Here, we present a brief review of the recent progress on various tuning methods in different 2D materials. Firstly, we discuss the operation principle of different 2D SPEs along with their unique characteristics. Secondly, we introduce various dynamic strain engineering methods for tuning the emission wavelengths in 2D SPEs. We also present several electric field-induced wavelength tuning methods for 2D SPEs. Lastly, we discuss the outlook of dynamically tunable 2D SPEs towards scalable 2D SPE arrays for realizing practical quantum photonics applications.

The size-dependent emission wavelength shift of micro-scale light emitting diodes (micro-LEDs) has been frequently reported in recent publications, but its underlying physical mechanism has not yet been thoroughly elucidated. Here, we fabricate and characterize the red, green, and blue InGaN micro-LED mesas with different diameters down to 1 μm. As the size decreases, all the samples of different colors show an inverted V-shaped photoluminescence wavelength variation trend, first a red shift and then a blue shift, and the shifting range is larger for samples with longer wavelengths. Micro-Raman spectrum confirms that the stress was significantly released after scaling down the size from epitaxial wafer to 1 μm. The theoretical simulations show that the red and blue shifts are, respectively, attributed to the bandgap narrowing and the weakening of the quantum-confined Stark effect caused by strain relaxation, which dominate successively. [ABSTRACT FROM AUTHOR]

AlGaN-based light-emitting diodes (LEDs) operating in the deep-ultraviolet (DUV) spectral range (210–280 nm) have demonstrated potential applications in physical sterilization. However, the poor external quantum efficiency (EQE) hinders further advances in the emission performance of AlGaN-based DUV LEDs. Here, we demonstrate the performance of 270-nm AlGaN-based DUV LEDs beyond the state-of-the-art by exploiting the innovative combination of bandgap engineering and device craft. By adopting tailored multiple quantum wells (MQWs), a reflective Al reflector, a low-optical-loss tunneling junction (TJ) and a dielectric SiO2 insertion structure (IS-SiO2), outstanding light output powers (LOPs) of 140.1 mW are achieved in our DUV LEDs at 850 mA. The EQEs of our DUV LEDs are 4.5 times greater than those of their conventional counterparts. This comprehensive approach overcomes the major difficulties commonly faced in the pursuit of high-performance AlGaN-based DUV LEDs, such as strong quantum-confined Stark effect (QCSE), severe optical absorption in the p-electrode/ohmic contact layer and poor transverse magnetic (TM)-polarized light extraction. Furthermore, the on-wafer electroluminescence characterization validated the scalability of our DUV LEDs to larger production scales. Our work is promising for the development of highly efficient AlGaN-based DUV LEDs. [ABSTRACT FROM AUTHOR]

Enhancing and preserving the atomic correlation and entanglement is of significant utility in quantum information. To this aim, we study the temporal evolution of uncertainty-induced nonlocality () and logarithmic negativity (ℒ ) as measures of quantum correlations (QCs) and quantum entanglement (QE) between two effective atoms coupled to a bosonic reservoir in the absence of thermal fluctuations and in the presence of Kerr medium (KM) and Stark shift (SS) under which n-photon transitions are permitted. We explore how Markovian and non-Markovian regimes affect the temporal dynamics of atomic correlation and entanglement and its limitations. Our findings indicate that by adjusting the KM and SS parameters, the quantum correlations between the two atoms can be enhanced and maintained while displaying similar qualitative behavior. Notably, it was observed that the QCs and QE quantities are at their highest magnitudes in the non-Markovian regime when the strengths of both SS and KM are increased, implying that QCs and QE are well protected. In contrast to the typical view that protecting the QCs from decoherence that may be observed owing to environmental noise, we proposed a gainful way to reduce the atomic decoherence by adjusting the number of n-photon transitions. Our investigation reveals that in the non-Markovian regime, the considered system exhibits better resistance against decoherence in comparison to the Markovian regime, as evidenced by the significant amount of quantum correlations detected among the two effective atoms at a specific point in time. [ABSTRACT FROM AUTHOR]

In this paper, we revisit the Stark effect of the hydrogen atom induced by a uniform static electric field. In particular, a general formula for the integral of associated Laguerre polynomials was derived by applying the method for Hermite polynomials of degree n proposed in the work (Anh-Tai T.D. et al., 2021 AIP Advances 11 085310). The quadratic Stark effect is obtained by applying this formula and the time-independent non-degenerate perturbation theory to hydrogen. Using the Siegert state method, numerical calculations are performed and serve as data for benchmarking. The comparisons are then illustrated for the ground and some highly excited states to provide an insightful look at the applicable limit and precision of the quadratic Stark effect formula for other atoms with comparable properties. [ABSTRACT FROM AUTHOR]

The polarized photoluminescence emitted on the edge of a series of aluminum‐rich (Al,Ga)N‐AlN quantum wells (QWs) grown by molecular beam epitaxy on AlN templates deposited by metal organic chemical vapor deposition on c‐plane sapphire is measured. The contrast and the principal axis of the emission diagrams for 2 nm‐thick (Al,Ga)N QWs grown for aluminum compositions between 40% and 90% are studied. The light is emitted on the edge of the QWs at wavelengths going from 280 nm down to 209 nm. The emission diagram, a change from oblate to prolate with respect to the in‐plane orientation, for an aluminum composition is found to occur around 72%, that is, at an emission wavelength of about 235 nm. The orientations and shapes of the edge‐emission diagrams indicate that the fluctuations of the composition of the (Al,Ga)N confining layer are deep enough for producing intravalence band mixings. This property, that acts in concert with the built‐in strain and quantum‐confined Stark effect, contributes to the anisotropy of the light emission when the aluminum composition reaches 60–70%, that is, for an emission wavelength of 260–235 nm. [ABSTRACT FROM AUTHOR]

Magnetically confined plasma experiments generate a wealth of spectroscopic data. The first step toward extracting physical parameters is to fit a spectral model to the often complex spectra. The CXSFIT (Charge eXchange Spectroscopy FITting) spectral fitting code was originally developed for fitting charge exchange spectra on JET from the late 1980s onward and has been further developed over decades to keep up with the needs of the users. The primary use is to efficiently fit a large number of spectra with many constrained Gaussian spectral lines of which the physical parameters can be coupled in a user-friendly manner. More recent additions to the code include time-dependent couplings between parameters, flexible background subtraction, and a non-linear coupling scheme between fit parameters. The latter was a pre-requisite for implementing Zeeman and motional Stark effect multiplets in the library of spectral features. The ability to save and replay "fit recipes," even when multiple iterations are required, has ensured the traceability of the results and is one of the keys to the longevity and success of the code. The code is also in use on other tokamaks (AUG, ST-40) and to fit data from other spectroscopic diagnostics on JET. In this paper, we document the current capabilities and philosophy behind the structure of the code, including some of the algorithms used to calculate spectral features numerically efficiently. We also provide an outline of how CXSFIT could be transferred into a framework that would be able to meet the spectral fitting requirements of future devices, such as ITER. [ABSTRACT FROM AUTHOR]

Measurement of the internal magnetic field is crucial for determining the equilibrium, stability, and current density of a plasma in a tokamak. A motional Stark Effect (MSE) diagnostic was developed to provide a measurement of the internal magnetic field in tokamaks by analyzing the emission from the interaction of the plasma particle with an injected neutral beam. The Stark effect causes the shifting and splitting of deuterium spectral lines due to the Lorentz electric field. However, it is difficult to accurately measure the internal magnetic field components since the radial electric field inherently formed inside the plasma is mixed with the Lorentz field. Under the circumstances in the Korea Superconducting Tokamak Advanced Research (KSTAR) device, one possible approach is to derive a radial electric field by measuring and comparing the polarization angles from the full and half-energy components of the neutral beam. To utilize the polychromatic MSE diagnostics in KSTAR, the half-energy component wavelength bands according to various magnetic field and beam energy combinations have been calculated, and the filter combinations required for those measurements have been selected. The Stokes-filter model used to evaluate the effect of multiple-ion-source neutral beam injection on the MSE measurements has been extended to infer the sensitivity of this approach to take the non-ideal bandpass filter effects into account. [ABSTRACT FROM AUTHOR]

Motional Stark effect polarimetry is a key diagnostic for plasma fusion research since its usage on PBX-M. The MSE diagnostic measures the radial magnetic pitch angle profile in a plasma from a neutral beam by observation of Stark split D-alpha emission from atoms excited by collision with ions and electrons in the plasma. The pitch angle measurement is used with equilibrium reconstruction codes to determine the q-profile for studies of plasma stability, confinement, and transport. Historically, the algorithm was used in a post-processing fashion. The goal of our work was to apply this method in real time and pass the results to the plasma control system computer for real-time equilibrium reconstruction and control. [ABSTRACT FROM AUTHOR]

Despite the considerable research interest in InGaN‐based microdisk lasers, owing to their unique circular geometry distinct from vertical cavity surface‐emitting lasers (VCSEL) or edge‐emitting lasers, commercial products remain scant due to deficient performance under electrical injection. This study proposes an innovative method integrating a thin‐film configuration with a metallic undercut, significantly augmenting optical confinement, overlap factor, and thus lasing performance. This approach results in a diminished lasing threshold from 1500 to 670 Wcm−2 and a record high quality (Q) factor of 10100 under electrical injection. Strain relaxation in the metallic undercut, identified via scanning near‐field optical microscopy (SNOM), beneficially mitigates the Quantum Confined Stark Effect (QCSE), boosting the internal quantum efficiency of the laser. Furthermore, a beneficial blue‐shift in the emission spectrum aligns with the lasing peak, strengthening the Q factor. A tactfully implemented recessed top contact enables electrical injection lasing without optical performance compromise. The study provides invaluable insights for future microdisk laser technology advancements, potentially leading to specialized functionalities, including quantum optics, thereby opening new avenues for research and applications in this field. [ABSTRACT FROM AUTHOR]

The anticrossing spectra of the helium line λ 1 s 4 l   D 3 , F − 1 s 2 p   P 3 = 447.2 nm emitted after electron capture by H e + ions in H e + − H e collisions were measured for projectile energies of 10–29 keV. Furthermore, considering the excited states' time evolution, the theoretical intensity functions were calculated. The electric field and density distributions of the target He atoms in the collision volume were taken into account, and by fitting the theoretical intensities to the measured ones, the post-collisional states of the charge-transferred He atoms were determined. The results indicate that for the intermediate projectile energy range, the electronic charge distributions were asymmetric, but the electric dipole moments did not change, as in the case of the target atoms excited directly in the collisions. This result shows that the Paul trap mechanism may play an important role in the charge transfer excitation in this energy range. [ABSTRACT FROM AUTHOR]

The construction of a large-scale quantum internet requires quantum repeaters containing multiple entangled photon sources with identical wavelengths. Semiconductor quantum dots can generate entangled photon pairs deterministically with high fidelity. However, realizing wavelength-matched quantum-dot entangled photon sources faces two difficulties: the non-uniformity of emission wavelength and exciton fine-structure splitting induced fidelity reduction. Typically, these two factors are not independently tunable, making it challenging to achieve simultaneous improvement. In this work, we demonstrate wavelength-tunable entangled photon sources based on droplet-etched GaAs quantum dots through the combined use of AC and quantum-confined Stark effects. The emission wavelength can be tuned by ~1 meV while preserving an entanglement fidelity f exceeding 0.955(1) in the entire tuning range. Based on this hybrid tuning scheme, we finally demonstrate multiple wavelength-matched entangled photon sources with f > 0.919(3), paving the way towards robust and scalable on-demand entangled photon sources for quantum internet and integrated quantum optical circuits. Realising scalable entangled photon sources with quantum dots requires compensating for both wavelength mismatches and exciton fine-structure splitting (FSS). So far, multiple QDs with the same emission wavelength and near-zero FSS have not been demonstrated. Here, the authors fill this gap, reaching high entanglement fidelity for multiple QDs tuned into resonance with each other or with Rb atoms. [ABSTRACT FROM AUTHOR]

It is commonly known that the high ionization energy of acceptor magnesium is the cause of the low hole injection efficiency in the active region of AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs). This study presents an effective method of exploiting the polarization effect in quantum wells to increase the hole injection efficiency of 279 nm AlGaN-based DUV LEDs. The polarization electric field can be exploited to increase the mean free path of holes and improve hole concentration in the active region by suitably increasing the thickness of the quantum well. This method effectively increases the hole concentration and improves the electron-hole wave function overlap. As a result, the internal quantum efficiency and optical power of DUV LEDs are significantly enhanced. It is noteworthy that the strong quantum confined stark effect can cause electron and hole wave functions to separate, leading to a decrease in LED performance when quantum wells exceed a certain thickness. [ABSTRACT FROM AUTHOR]

Slow (meV) photoelectron imaging spectroscopy is employed in the experimental study of near-threshold photoionization of strontium atoms in the presence of an external static electric field. Specifically, the study is devoted to the glory effect, that is, the appearance of an intense peak at the center of the recorded photoelectron images, when dealing with m = 0 final ionized Stark states (m denoting the magnetic quantum number). This critical effect is formally identical to that encountered in classical scattering theory, where, for a nonzero value of the impact parameter, the zero-crossing of the deflection function leads to a divergent classical differential cross section. By recording the magnitude variation of this glory peak as a function of electron excitation energy, we observe that, besides the traces of classical origin, it also exhibits intense quantum interference and beating phenomena, above and below the zero-static-field ionization threshold. We study both, single- and two-photon ionization of Sr, thus enabling a comparison not only between the different excitation schemes, but also with an earlier work devoted to two-photon ionization of Mg atom by Kalaitzis et al (2020 Phys. Rev. A 102 033101). Our recordings are analyzed within the framework of the Harmin–Fano frame transformation Stark effect theory that is applied to both the hydrogen atom and a non-hydrogenic one simulating Sr. We discuss the various aspects of the recorded and calculated glory interference and beating structures and their 'short time Fourier transforms' and classify them as either atom-specific or atom independent. In particular, we verify the 'universal' connection between the glory oscillations above the zero-field threshold and the differences between the origin-to-detector times of flight corresponding to pairs of classical electron trajectories that end up to the image center. [ABSTRACT FROM AUTHOR]

Porphyrins are excellent light‐harvesting complexes. Presently they are unsuitable for photovoltaic applications, as their excellent light absorbance is compensated to a large extent by their poor transport properties, where most excitons are lost by recombination. Arranging porphyrins in regular, strongly bound, lattices of surface‐anchored metal‐organic frameworks (PP‐SURMOFs) may facilitate charge carrier dissociation, but does not significantly enhance the conductive properties. In most cases, photogenerated excitons traverse undirected, Brownian motion through a hopping process, resulting in a substantial diffusion length to reach electrodes, leading to significant exciton loss through recombination. Here, we propose to guide exciton diffusion indirectly by an external electric field. We show that electric fields, even as strong as 1 V nm−1, do not affect the HOMO‐LUMO gap of the porphyrins. However, fields of 0.1 V nm−1 and even less demonstrate a notable Stark effect, with slight band gap reductions, for some PP‐SURMOFs. When applied as an electric field gradient, for instance, via the substrate, it creates a unidirectional hopping pathway for the excitons. Consequently, we expect a significant reduction of exciton diffusion length leading to increased utilization of photogenerated excitons as they reach the electrodes. This strategy holds promise for integrating photoactive molecules in photovoltaic and photocatalytic applications. [ABSTRACT FROM AUTHOR]

Data on Stark broadening parameters, spectral line widths, and shifts for 15 multiplets of N VI, whose spectral lines are broadened by collisions with electrons, protons, alpha particles (He III) and B III, B IV, B V and B VI ions, are presented. They have been calculated using the semiclassical perturbation theory, for temperatures from 50,000 K to 2,000,000 K, and perturber densities from 1016 cm−3 up to 1024 cm−3. The data for e, p and He III are of particular interest for the analysis and modelling of atmospheres of hot and dense stars, as, e.g., white dwarfs, and for investigation of their spectra, and data for boron ions are used for analysis and modelling of laser-driven plasma in proton–boron fusion research. Dataset: The dataset is submitted as a Supplementary File. Dataset License: CC-BY 4.0 [ABSTRACT FROM AUTHOR]

Solution‐processed 2D materials hold promise for their scalable applications. However, the random, fragmented nature of the solution‐processed nanoflakes and the poor percolative conduction through their discrete networks limit the performance of the enabled devices. To overcome the problem, conduction modulation of the solution‐processed 2D materials is reported via Stark effect. Using liquid‐phase exfoliated molybdenum disulfide (MoS2) as an example, nonlinear conduction switching with a ratio of >105 is demonstrated by the local fields from the interfacial ferroelectric P(VDF‐TrFE). Through density‐functional theory calculations and in situ Raman scattering and photoluminescence spectroscopic analysis, the modulation is understood to arise from a charge redistribution in the solution‐processed MoS2. Beyond MoS2, the modulation may be shown effective for the other solution‐processed 2D materials and low‐dimensional materials. The modulation can open their electronic device applications, for instance, thin‐film nonlinear electronics and non‐volatile memories. [ABSTRACT FROM AUTHOR]

The review examines telecom electro-optic modulators made of group III–V compound semiconductor material composed of indium phosphide. The operation principles of modulators and issues of heterostructure and modulator design optimization are considered; the results of recent developments and the achieved parameters of modulators are presented. [ABSTRACT FROM AUTHOR]

Rydberg atoms-based electric field sensing has developed rapidly over the past decade. A variety of theoretical proposals and experiment configurations are suggested and realized to improve the measurement metrics, such as intensity sensitivity, bandwidth, phase, and accuracy. The Stark effect and electromagnetically induced transparency (EIT) or electromagnetically induced absorption (EIA) are fundamental physics principles behind the stage. Furthermore, various techniques such as amplitude- or frequency-modulation, optical homodyne read-out, microwave superheterodyne and frequency conversion based on multi-wave mixing in atoms are utilized to push the metrics into higher levels. In this review, different technologies and the corresponding metrics they had achieved were presented, hoping to inspire more possibilities in the improvement of metrics of Rydberg atom-based electric field sensing and broadness of application scenarios. [ABSTRACT FROM AUTHOR]

Stark effect, the electric-field analogue of magnetic Zeeman effect, is one of the celebrated phenomena in modern physics and appealing for emergent applications in electronics, optoelectronics, as well as quantum technologies. While in condensed matter it has prospered only for excitons, whether other collective excitations can display Stark effect remains elusive. Here, we report the observation of phonon Stark effect in a two-dimensional quantum system of bilayer 2H-MoS2. The longitudinal acoustic phonon red-shifts linearly with applied electric fields and can be tuned over ~1 THz, evidencing giant Stark effect of phonons. Together with many-body ab initio calculations, we uncover that the observed phonon Stark effect originates fundamentally from the strong coupling between phonons and interlayer excitons (IXs). In addition, IX-mediated electro-phonon intensity modulation up to ~1200% is discovered for infrared-active phonon A2u. Our results unveil the exotic phonon Stark effect and effective phonon engineering by IX-mediated mechanism, promising for a plethora of exciting many-body physics and potential technological innovations. The authors report experimental evidence of phonon Stark effect in 2H-MoS2 bilayers. A Stark phonon appears as the interlayer excitons are tuned to resonate with the LA phonon emission line, and shows a linear energy shift upon application of an out-of-plane electric field. [ABSTRACT FROM AUTHOR]

Potassium europium molybdate, KEu(MoO4)2, is an intriguing material known for its efficient luminescence properties attributed to Eu3+ ions and its polymorphic nature. Despite its significance, research on the metastable γ-phase has been limited, with no prior reports on its structure, particle morphology, and luminescence characteristics. In this study, both the stable α-phase and the metastable γ-phase of KEu(MoO4)2 were synthesized using solid-state and hydrothermal reaction methods, and their crystal structures, particle morphologies, and luminescence properties were comprehensively investigated. X-Ray diffraction analysis confirmed the formation of the triclinic α-phase and the orthorhombic γ-phase, with factor analysis results consistent with theoretically optimized structures, facilitating accurate structural determination. Both phases exhibited typical photoluminescence (PL) spectra of Eu3+ ions. However, in the γ-phase, the 5D0 → 7F2 transition appeared as a non-split peak with minimal Stark effect, attributed to differences in structural symmetry between the phases. A red-shift in the PL excitation edge was observed in the α-phase, which was attributed to a narrowed band gap resulting from the broadening of the O-p orbital in the valence band, as indicated by density functional theory (DFT) calculations. Additionally, KEu(MoO4)2 was doped with Y3+ ions to form K(Eu,Y)(MoO4)2, revealing a solid solubility limit of 40% in the α-phase, while the γ-phase displayed no solid solution limit. The estimated critical distance of Eu3+ ions suggested that Eu–Eu interactions contributing to concentration quenching are minimal in the stacking direction but significant in the in-plane direction, operating in the second shell. [ABSTRACT FROM AUTHOR]

Reflection spectra of a heterostructure with a GaAs/AlGaAs quantum well (QW) of 30 nm wide have been studied under additional optical excitation in an external electric field. The influence of the electric field on all parameters of light-hole and heavy-hole exciton resonances, was studied upon selective excitation of various optical transitions. The effect of compensating for the Stark shift upon excitation to the ground exciton state of the QW is found. A sharp increase in the Stark shift of excitons in QW was found upon optical creation of charge carriers in the GaAs buffer layer. A microscopic calculation of exciton states in various electric fields has been performed. A comparison of the calculated and measured Stark shift of the heavy-hole exciton is used to obtain the dependence of the electric field strength in the QW on the applied voltage. [ABSTRACT FROM AUTHOR]

Calculations and measurements of polarization-dependent soft X-ray scattering intensity are presented during a magnetic hysteresis cycle. It is confirmed that the dependence of the intensity on the magnetic moment can be linear, quadratic or a combination of both, depending on the polarization of the incident X-ray beam and the direction of the magnetic moment. With a linearly polarized beam, the scattered intensity will have a purely quadratic dependence on the magnetic moment when the magnetic moment is parallel to the scattering plane. However, with the magnetic moment perpendicular to the scattering plane, there is also a linear component. This means that, when measuring the hysteresis with linear polarization during a hysteresis cycle, the intensity will be an even function of the applied field when the change in the magnetic moment (and field) is confined within the scattering plane but becomes more complicated when the magnetic moment is out of the scattering plane. Furthermore, with circular polarization, the dependence of the scattered intensity on the moment is a combination of linear and quadratic. With the moment parallel to the scattering plane, the linear component changes with the helicity of the incident beam. Surprisingly, in stark contrast to absorption studies, even when the magnetic moment is perpendicular to the scattering plane there is still a dependence on the moment with a linear component. This linear component is completely independent of the helicity of the beam, meaning that the hysteresis loops will not be inverted with helicity. [ABSTRACT FROM AUTHOR]

This study explores the effects of growth temperature of InGaN/GaN quantum well (QW) layers on indium migration, structural quality, and luminescence properties. It is found that within a specific range, the growth temperature can control the efficiency of In incorporation into QWs and strain energy accumulated in the QW structure, modulating the luminescence efficiency. Temperature-dependent photoluminescence (TDPL) measurements revealed a more pronounced localized state effect in QW samples grown at higher temperatures. Moreover, a too high annealing temperature will enhance indium migration, leading to an increased density of non-radiative recombination centers and a more pronounced quantum-confined Stark effect (QCSE), thereby reducing luminescence intensity. These findings highlight the critical role of thermal management in optimizing the performance of InGaN/GaN MQWs in LEDs and other photoelectronic devices. [ABSTRACT FROM AUTHOR]

Using a stereo camera system, a new diagnostic for the safety factor of the core plasma based on the pellet ablation trail is applied on the Experimental Advanced Superconducting Tokamak (EAST). In EAST discharge No. 128 874, a shattered pellet injection system is applied to inject a shattered neon pellet into the EAST. Since the strong magnetic field in tokamaks binds the ablated pellet material, the orientation of the pellet ablation trail is the same as the local magnetic field direction. Thus, from the three-dimensional reconstruction result of the pellet ablation trail, the local safety factor q can be obtained. The motional Stark effect (MSE) diagnostic is applied to determine the safety factor q profile in this shot. The determined safety factor q results for this new diagnostic are in quantitative agreement with those from the MSE diagnostic with the mean relative difference of only 6.8%, confirming the effectiveness of this new diagnostic of the safety factor. [ABSTRACT FROM AUTHOR]

A model potential previously developed for the ammonia molecule is treated in a single-center partial-wave approximation in analogy with a self-consistent field method developed by Moccia. The latter was used in a number of collision studies. The model potential is used to calculate DC Stark resonance parameters, i.e., resonance positions and shifts using the exterior complex scaling method for the radial coordinate. Three molecular valence orbitals are investigated for fields along the three Cartesian coordinates, i.e., along the molecular axis and in two perpendicular directions. The work extends previous work on the planar-geometry water molecule for which non-monotonic shifts were observed. We find such non-monotonic shifts for fields along the molecular axis. For perpendicular fields, we report the splitting of the 1 e orbitals into a fast- and a slow-ionizing orbital. [ABSTRACT FROM AUTHOR]

The possibility of carrying out measurements of plasma parameters in a tokamak with reactor technologies (TRT) by means of the technique based on the Stark effect by resolving the spectrum of the split lines of Balmer series emitted by fast hydrogen atoms injected into plasma is analyzed. The code containing the models of emission applicable for the high-temperature tokamak plasma, along with the library of functions for the ray-tracing simulation of geometric optics, was used. Simulation of spectra of active neutral beam emission and plasma emission, both as a result of charge exchange on beam atoms and passive one, taking into account reflections from the plasma facing vessel elements, allowed determining parameters of the diagnostic injector and relative position of the light-collection systems and heating injectors for which the useful and background spectra could be separated. The signal gathered by the detector is simulated. The shape of the visual angle along the line of sight, optical properties of the lens materials, the instrumental function of the spectral device, the sensor characteristics, and statistical noise of the signal are taken into consideration. Based on the obtained results, a preliminary concept of the motional Stark effect (MSE) diagnostic for the tokamak with reactor technologies is proposed. [ABSTRACT FROM AUTHOR]

Spectral line shapes code in plasmas (SLSPs) code comparison workshops have been organized in the last decade with the aim of comparing the spectra obtained with independently developed analytical and numerical models. Here, we consider the simultaneous effect of a plasma microfield and a periodic electric field on the hydrogen lines Lyman-α, Lyman-β, Balmer-α, and Balmer-β for plasma conditions where the Stark effect usually dominates line broadening. [ABSTRACT FROM AUTHOR]

AC Stark shifts have an impact on the dynamics of atoms interacting with a near-resonant quantized single-mode cavity field, which is relevant to a single atom micromaser. In this study, we demonstrate that, when the field is in a squeezed coherent state, atomic lineshapes are highly sensitive to the squeezing parameter. Furthermore, we show that, when considering a superposition of squeezed coherent states with equal amplitude, the displacement of the transition lines depends significantly, not only on the squeezing parameter, but also on its sign. [ABSTRACT FROM AUTHOR]

We provide in this work Stark broadening data (widths and shifts) for 120 ultraviolet spectral lines of Ni  v ion. Our calculations are performed using the semiclassical perturbation method. For energy levels and oscillator strength calculations, we use the multiconfiguration Hatree–Fock approach. Stark shifts and widths are calculated for collisions with electrons and with the positive ions: H+, He+, and He++, allowing us to take into account the important perturbers in stellar atmospheres. We compare our Stark widths with estimations obtained using the Cowley formula. Our electron impact Stark widths are also fitted with temperature using a logarithmic formula. Finally, our obtained Stark widths are used to investigate the influence of Stark broadening in the atmospheric conditions of hot DA white dwarfs. Despite the importance of ultraviolet lines of Ni  v ion for modelling white dwarf atmospheres and also for investigations of variation of fundamental constants with gravitational potential, we did not find Stark broadening data previously calculated or measured for Ni  v ion. The objective of this work is to give the missed data. [ABSTRACT FROM AUTHOR]