Line Shape Research Articles

Gate-voltage-dependent differential conductance via entangled-state tunneling in quantum point contacts.

The gate-voltage-dependent differential conductance in quantum point contacts, shaped by entangled-state tunneling, is demonstrated through the gate-voltage-induced displacement of a localized spin. This displacement leads to left-right asymmetric Kondo coupling at low gate voltages, transitioning to symmetric Kondo coupling at higher voltages. To analyze this behavior, we employ the Green's function technique in Liouville space, which allows for the systematic construction of basis vectors represented by operators. The entanglement between left and right dynamics gives rise to an additional coherent side peak, which plays a crucial role in reproducing the observed differential conductance line shape. By determining model parameters phenomenologically, we successfully replicate the experimentally observed gate-voltage-dependent conductance features.

All-weather precision alignment technology for ultra-wide steel box girders in cable-stayed bridges

High precision is required during the precise matching construction of steel box girder cable-stayed bridge segment suspension assembly. Due to temperature differences, sunlight, and other factors, the bridge shape changes dramatically during the day, so the precise matching of steel box girder cable-stayed bridges is generally carried out at night when the temperature is stable. However, nighttime construction restricts the progress of the project and poses certain safety hazards. This article proposes a precise matching construction method for steel beams during the dynamic changes in bridge line shape during the daytime through theoretical calculations and numerical analysis. After one measurement, two retests, and three calculations, and considering the influence of process and environmental factors, dynamic measurement, real-time calculation, and real-time control were applied to Yangmeizhou Bridge to achieve all-weather dynamic precise matching construction of steel box girders, verifying the feasibility of this method.

The hydrogen Lyman α line shape in the exospheres of terrestrial objects in the solar system

The exospheres of all objects are mostly made of atomic hydrogen. Because the Sun is bright in Lyman α, the properties of the H atoms in the exospheres of certain terrestrial solar system objects can be studied by analyzing the resonantly scattered solar Lyman α emission by these exospheric H atoms. This emission is optically thick in the exospheres of all planets in our solar system except Mercury. This makes it complicated to derive the true characteristics (number density distribution, energy distribution) of the H atoms present in these exospheres. While radiative transfer (RT) models have been used extensively to derive the characteristics of exospheric H atoms by modeling the line-integrated Lyman α intensity measured by spacecrafts via remote sensing, the models often fail to resolve discrepancies between the observed emission intensity and the simulated value. This is because of the various assumptions that are made in the RT models about the inherent characteristics of the H atoms and the corresponding Lyman α lineshape. Our knowledge about the characteristics of the H atoms can be significantly improved by understanding what the true lineshape of the H Lyman α line may be for various conditions. This can then be used to resolve the discrepancies between the modeled and the observed intensities for planetary exospheres. Here we present a detailed study on the shape of the exospheric Lyman α emission line for various conditions like change in altitude, temperature, non-isothermality, asymmetry, and presence of non-thermal atoms. These detailed line profiles are being used to determine H density distribution in Earth’s exosphere from analysis of absorption of the solar Lyman α line by geocoronal H as measured by remote sensing satellites. This theoretical analysis also highlights the advantages of obtaining highly resolved H Lyman α emission line measurements from the exospheres of certain terrestrial objects in our solar system.

Composite nature of the Tcc state

Abstract In 2021, LHCb collaboration reported a very narrow state in the D 0 D 0 π + mass spectrum just below the D *+ D 0 mass threshold. We consider the influence of the Castillejo–Dalitz–Dyson (CDD) pole in the scattering amplitude to derive a general treatment for the two-body final state interaction near its threshold. The line shape (or the energy dependent event distribution) are then obtained, where the parameters can be fixed by fitting to the experimental data on the D 0 D 0 π + mass spectrum. Within our method the data are quite well reproduced. The pole structure in the complex energy plane indicates that the T cc state has a large portion of elementary degree of freedom (e.g. the compact tetraquark component) inside its hadron wave function. The compositeness as a measure of molecule component in its wave function is predicted to be 0.2 3 − 0.09 + 0.40 . Clearly, the non-molecular component takes a non-negligible or even dominant portion.

Speciation of Magnesium Surfaces by X‐Ray Photoelectron Spectroscopy (XPS)

ABSTRACTMagnesium metal, alloys, and salts have ubiquitous uses as structural materials, components in energy‐conversion devices, and catalysts. The surface states and reactions that underpin these applications are commonly studied by X‐ray photoelectron spectroscopy (XPS). Yet, reported binding energies for the Mg 2p transition vary widely, making accurate speciation of magnesium surfaces by XPS notoriously challenging. We found that these literature discrepancies result from differences between charge referencing procedures, particularly due to the unusually high binding energy of adventitious carbon on MgO and Mg(OH)2. Relevant pure and mixed samples were analyzed to assess the chemical speciation for magnesium. The range of Mg 2p binding energies was only 1.2 eV for pure samples, insufficient for speciation in many cases. The Mg KLL spectral lines were studied and found to provide additional chemical information due to final‐state effects. The range of the modified Auger parameter (α’), which is also independent of charging, was found to be 2.9 eV. The position and shape of the Mg KLL spectral lines are reported, and their use for the speciation of mixed systems is demonstrated. Moreover, a curve‐fitting procedure for O 1s signals was developed, which can separate MgO and Mg(OH)2 despite their overlapping Mg 2p signals.

Assessment of Seaweed Biodiversity under the Influence of Chemical Industry Effluents : A Case Study at Veraval, Gujarat Coast

The coastal zone is an interface between land and sea. the interaction between land and sea involves physical and chemical processes, which produce characteristic shapes of coast line. Thus, in a coastal zone the terrestrial ecosystem has its influence on the sea and vice versa. The physical features of the land bordering the sea, wind, speed, water currents, salinity, pollutants, light, temperature and number of other related factors influence coastal productivity and its species diversity. The present investigation was carried out at Veraval at Lat 210 35’N; Long 690 36E’. It is one of the important port cities located along the western coast of Gujarat in India. Its water is polluted by viscous filament of yarns. Sulphuric acid, carbon disulphide & sodium sulphate discharge through chemical industry effluent. In order to achieve the aim following parameters were studied to assess species diversity of seaweeds along increasing distance from the discharge point. Number of seaweed species showed a trend similar to that of species diversity was more related to species richness. Ratio of species number for Green, Brown and Red algae indicated that red algae were in greater proportion than green and brown algae. Seaweed species diversity was minimum near Chemical industry effluent discharge point during post monsoon, Pre monsoon and Monsoon. Whereas it increases as the discharge point from the outfall increases.

Directly revealing double-resonance dynamics of second-harmonic generation in a quadratic microcavity

High-quality (Q) microcavities, which significantly enhance wave mixings through optical resonances, play an important role in the investigation of light–matter interaction. For second-harmonic generation (SHG) in quadratic microcavities, satisfying a double-resonance condition is crucial for enhancing the nonlinear conversion. However, directly revealing a precise double-resonance condition can be demanding and has seldom been implemented. In this work, we introduce a method to synchronize the fundament wave and its second harmonic during the transmission measurement, and directly distinguish the double-resonance detuning. We also investigate the impact of each detuning on the cavity-enhanced SHG spectral line shape and intensity. The approach provides a method to help deeper understand of the nonlinear coupling processes and benefit research on cavity-enhanced nonlinear optics.

Differential chirped-pulse dual-comb spectroscopy for complex line shape fitting the R(6) manifold of the 2ν3 band of methane

Differential chirped-pulse dual-comb spectroscopy for complex line shape fitting the R(6) manifold of the 2ν3 band of methane

Maximizing spectral sensitivity without compromising resolution in phase-incremented, steady-state solution NMR

NMR acquisitions based on Ernst-angle excitations are widely used for maximizing spectral sensitivity without compromising bandwidth or resolution. However, if relaxation times T1, T2 are long and similar, as is often the case in liquids, steady-state free-precession (SSFP) experiments could provide higher sensitivity per acquisition_time (SNRt). Although strong offset dependencies and poor spectral resolutions have impeded SSFP’s analytical applications, this study reexplores if, when and how can phase-incremented (PI) SSFP schemes overcome these drawbacks. It is found that PI-SSFP can indeed provide a superior SNRt than Ernst-angle FT-NMR acquisitions, but that achieving this requires using relatively large flip angles. This, however, can restrict PI-SSFP’s spectral resolution and lead to distorted line shapes; to deal with this we introduce here a new SSFP outlook that overcomes this dichotomy. This outlook also leads to a new processing pipeline for PI-SSFP acquisitions, providing high spectral resolution even when utilizing relatively the large flip angles. The enhanced SNRt that the ensuing method can provide over FT-based NMR counterparts, is demonstrated with a series of 13C and 15N investigations on organic compounds.

CFI-Former: Efficient lane detection by multi-granularity perceptual query attention transformer.

CFI-Former: Efficient lane detection by multi-granularity perceptual query attention transformer.

Observation of a Fano Resonance at 92 meV (13.5 µm) in Al0.2Ga0.8N/GaN-Based Quantum Cascade Emitters

We report on asymmetrically shaped Fano resonances in Al0.2Ga0.8N/GaN-based quantum cascade structures. In order to observe this type of resonance in electro-luminescence, a spectrally narrow feature must interact with a broad, quasi-continuous emission. While the narrow waveform is provided by the GaN-based LO-phonon at 92 meV (13.5 µm, 741 cm−1), the broad peak consists of overlapping inter-subband transitions between several higher-order excited states ranging from 80 to 300 meV and the ground state. Through the interference of these spectrally dissimilar peaks, a typical, asymmetric Fano line shape is generated.

Phase evolution of strong-field ionization

We investigate the time-dependent evolution of the dipole phase shift induced by strong-field ionization (SFI) using attosecond transient absorption spectroscopy (ATAS) for time delays where the pump-probe pulses overlap. We study measured and calculated time-dependent attosecond transient absorption spectra of the ionic 4d→5p in xenon, and present the time-dependent line shape parameters in the complex plane. We attribute the complex dynamics to the contribution of three distinct processes: accumulation of ionization, transient population, and retrapping of excited states arising from polarization of the ground state. Published by the American Physical Society 2025

Multiscale Dynamical Processes Shaping a Mixing Line

Abstract The paper discusses multiscale dynamical processes shaping a mixing line in the upper troposphere/lower stratosphere (UTLS). It focuses on aircraft observations above southern Scandinavia during a mountain wave event and how they can be analyzed based on dynamic variables and the trace gases O and CO. This study aims to identify the irreversible component of the stratosphere‐troposphere exchange. It was shown that the overall shape of the mixing line is determined by the large‐scale and mesoscale atmospheric conditions in the UTLS. Especially, the wide range of values along the flight tracks causes a compact, almost linear tracer‐tracer relation between O and CO. Only motion components with scales less than 4 km lead to the observed scatter around the mixing line. The anisotropic and patchy nature of the observed turbulence is responsible for this scatter in O and CO. The turbulence analysis reveals different scaling laws for the power spectra upstream, over the ridge and downstream of the mountains that lead to energy dissipation and irreversible mixing. The study suggests that turbulence dynamics may follow a cycle starting with 3D homogeneous isotropic turbulence upstream, transitioning to anisotropic turbulence over the ridge and further downstream. This transition is attributed to an interplay between turbulent eddies and internal gravity waves.

The Dark State, Vibronic Coupling, and Viscosity Sensing of Methoxylated Benzoyl Coumarins.

The 8/6-methoxylated 3-benzoyl coumarins (BC8 and BC6) are synthesized and demonstrated potential as a viscosity-sensitive fluorescent probe. To date, the mechanism of viscosity sensing has predominantly been attributed to a twisted intramolecular charge transfer effect. However, the observed fluorescence quenching is better ascribed to the presence of a dark charge transfer (1CT) state. Fluorescence enhancement in high-viscosity media is driven by an emissive hybridized local and charge-transfer (1HLCT) state and the suppression of the 1HLCT → 1CT transition and configuration conversion. Furthermore, vibronic fluorescence emission spectra at 77 K are computed using an intense adiabatic Hessian model and Voigt line shape functions to probe the contributions of Franck-Condon/Herzberg-Teller effects. The fluorescence emission and internal conversion rate at both 298 and 77 K are also theoretically determined, enabling the calculation of a fluorescence quantum yield that agrees well with experimental findings and further reconfirming the presence of 1CT configuration. Thus, this study not only advances understanding of the dark 1CT state of methoxylated benzoyl coumarins but also provides computational protocols for modeling 1HLCT → 1CT transition and vibronic emission spectra. Additionally, it offers a new molecular design and mechanism for the development of viscosity-sensitive fluorophores.

Observation of an all-fiber Fano resonance comb.

This study demonstrates the generation of a tunable all-fiber Fano resonance comb by incorporating a 10° tilted fiber Bragg grating (TFBG) into an all-fiber Mach-Zehnder interferometer (MZI). The TFBG generates the discrete state that couples with the continuum state of the MZI to produce all-fiber Fano resonance comb spanning an 80 nm spectral range. This system exhibits precise tunability, enabling continuous transitions among asymmetric Fano line shape, symmetric electromagnetically induced transparency, and electromagnetically induced absorption line shapes. The results also demonstrate that key spectral parameters, including the Fano parameter q, slope rate, and extinction ratio, exhibit periodic variation. The proposed approach offers a robust, low-loss, and scalable solution for multi-Fano resonance generation and holds promise for applications of high-sensitivity sensing and optical switching.

Long timescale solvation dynamics and confinement: The case of non-ionic deep eutectic solvents of lauric acid and N-methylacetamide.

Microscopic segregation and molecular heterogeneities in complex liquids are the result of the interplay between different intermolecular forces, all of which contribute to the energy landscape of the system. A consequence of the intricate energy landscape is the nontrivial effect on the solvation dynamics. Here, the impact of molecular heterogeneities on the solvation dynamics is studied using infrared spectroscopies and molecular dynamics simulations. In particular, this study focuses on the dynamical effect of nanoscopic heterogeneities present in deep eutectic solvents (DESs) composed of lauric acid (LA) and N-methylacetamide (NMA). To this end, a molecular probe containing a carbon triple bond is used as an infrared reporter. The results show that the vibrational probe is likely to be located in the NMA polar domains. Furthermore, the probe solvation dynamics derived from the 2DIR spectra presents a slowdown of its timescale with increasing LA concentration in the DES. Kubo modeling of the probe solvation dynamics shows a correlation between the amplitude of its long time component and the presence of molecular heterogeneities in the sample. Semiclassical modeling of the vibrational line shape of the triple bond stretch demonstrates that the heterogeneities affect the whole solvation dynamics of the system through the amplitudes of the frequency fluctuations. Molecular dynamics simulations confirm the experimental results and their interpretation by showing a slowdown of the solvation dynamics when the LA heterogeneities are present. Overall, the study presents a molecular framework to explain the effect of confinement created by nanoscopic LA heterogeneities on the solvation dynamics of the system.

Investigating the Narrowing Effect in Muon Spin Relaxation within Fluctuating Magnetic Fields: A Strong Collision Model Approach

We present our recent findings on the narrowing effect observed in muon spin relaxation within fluctuating magnetic fields, with a particular focus on muon diffusion in a background of random fields. Utilizing a strong collision model framework, we explore muon diffusion in a random Voigtian magnetic field and introduce a novel parameter to characterize the narrowing effect on the muon spin resonance (μSR) line shape. For the first time, we computationally demonstrate that the narrowing effect depends on the ratio of the Lorentzian half-width at half-maximum (HWHM) to the Gaussian HWHM. Our results indicate that increasing the Lorentzian HWHM reduces the rate of the narrowing effect, leading to a saturation regime characterized by an exponential relaxation function. When the Lorentzian contribution is sufficiently high, the motional narrowing effect disappears. This transition is marked by a sign change in our defined parameter from positive to negative values. Furthermore, we extend our study to La1.976Sr0.024CuO4 at 200 K, where our analysis reveals that muon diffusion occurs in the presence of a static Gaussian nuclear dipole field, while the static Lorentzian field remains absent. These findings underscore the importance of considering both muon diffusion and fluctuating fields in the interpretation of μSR spectra. Our study provides significant insights into muon behavior in complex magnetic environments, particularly in materials exhibiting spin glass states or mixed magnetic interactions, contributing to a broader understanding of magnetic field interactions at the microscopic level.

Understanding the nontrivial isoscalar pseudoscalar structures in the KSKSπ0 spectra in the J/ψ radiative decay

Initiated by the recent observation of a flattened line shape of IJPC=00−+ around 1.4–1.5 GeV in the KSKSπ0 invariant mass spectrum by BESIII, we make a systematic partial wave analysis of J/ψ→γηX→γKK¯π based on an isobaric approach. We demonstrate that in the scenario of the first radial excitations of the isoscalar pseudoscalar from the KK¯π threshold to about 1.6 GeV the non-trivial KSKSπ0 invariant mass spectrum can be explained by the coupled-channel effects with the presence of the triangle singularity mechanism. It shows that a combined fit of the Dalitz plots, three-body and two-body spectra can be achieved, which suggests that the one-state solution around 1.4–1.5 GeV proposed before still holds well. In particular, we show that the coupled-channel effects between the three important quasi-two-body decay channels, K*K¯+c.c., κK¯+c.c. and a0(980)π, can be well described by taking into account the one-loop corrections in the isobaric approach. This is because the isoscalar pseudoscalar states are coupled to the K*K¯+c.c. and a0(980)π (κK¯+c.c.) channels via the P and S waves, respectively. As a consequence, the coupled-channel effects can be largely absorbed into the redefinition of the tree-level effective couplings with the transition amplitudes computed to the order of one-loop corrections. Then, the coupled-channel effects can be estimated by the contributions from the one-loop rescattering amplitudes in comparison with the tree-level ones, where we find that the rescattering contributions from the P wave into the S wave, or vice versa, are apparently suppressed in the kinematic region near threshold. Published by the American Physical Society 2025

No planet around the K giant star 42 Draconis

Published radial-velocity (RV) measurements of the K giant star 42 Dra taken over a three-year time span reveal variations consistent with a 3.9 Jupiter-mass companion in a 479-d orbit. This exoplanet can be confirmed if these variations are long-lived and coherent. Continued monitoring may also reveal additional companions. We acquired additional RV measurements of 42 Dra; the data now span 15 years. Standard periodogram analyses were used to investigate the stability of the planet's RV signal. We also investigated variations in the spectral line shapes using the bisector velocity span as well as infrared photometry from the COBE mission. The recent RV measurements do not follow the published planet orbit. An orbital solution using the 2004 - 2011 data yields a period and eccentricity consistent with the published values, but the RV amplitude decreased by a factor of four since the earlier measurements. Including some additional RV measurements taken between 2014 and 2018 reveals a second period at 530 d. The interference (beating) of this period with the one at 479 d may account for the observed amplitude variations. The planet hypothesis is conclusively ruled out by COBE/DIRBE 1.25 μ photometry, which shows variations with the planet orbital period as well as a 170 d period. The RV of 42 Dra shows significant amplitude variations, which along with the COBE/DIRBE photometry firmly established that there is no giant planet around this star. The presence of multi-periodic variations suggests that we are seeing stellar oscillations in this star, most likely oscillatory convection modes. These oscillations may account for some of the long-period RV variations attributed to planets around K giant stars that may skew the statistics of planet occurrence around intermediate-mass stars. Long-term monitoring with excellent sampling is required to exclude amplitude variations in the long periods found in the RV of K giant stars.

Surface Properties of p‐GaN and Formation of Nickel Metal Contacts

Abstract Nickel (Ni) is the key component in ohmic contacts for Mg‐doped p‐GaN, but the detailed formation mechanisms of the ohmic contact have not yet been understood. In this work, the effect of potassium hydroxide (KOH)‐based chemical treatment on the surface of p‐GaN is investigated using X‐ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and low‐energy electron diffraction (LEED). Ni metal contacts on the chemically treated p‐GaN surface are studied using transfer length method (TLM) and synchrotron radiation photoelectron spectroscopy (SR‐XPS). The chemical treatment of p‐GaN improves the brightness of the (1x1) hexagonal diffraction pattern in LEED and keeps the 2D terrace structure in STM visible. Concomitantly, XPS shows that the amount of O, C, and Mg–O bonds at the surface were reduced. Ni/p‐GaN provided an ohmic contact after annealing in ultra‐high vacuum (UHV) at 500 °C. Simultaneously, SR‐XPS shows the diffusion of Ga to Ni and the formation of a previously unreported Ga 3d component, which has a surprisingly narrow line shape, indicating that it originates from a crystalline interface phase. Diffusion of Ga is discussed to cause Ga vacancies and acceptor levels in the bandgap increasing carrier tunneling, thus enabling ohmic contact.