Atomic States Research Articles

Surface-Enriched Room-Temperature Liquid Bismuth for Catalytic CO2 Reduction.

Bismuth-based electrocatalysts are effective for carbon dioxide (CO2) reduction to formate. However, at room temperature, these materials are only available in solid state, which inevitably suffers from surface deactivation, declining current densities, and Faradaic efficiencies. Here, the formation of a liquid bismuth catalyst on the liquid gallium surface at ambient conditions is shown as its exceptional performance in the electrochemical reduction of CO2 (i.e., CO2RR). By doping a trace amount of bismuth (740ppm atomic) in gallium liquid metal, a surface enrichment of bismuth by over 400 times (30 at%) in liquid state is obtained without atomic aggregation, achieving 98% Faradic efficiency for CO2 conversion to formate over 80 h. Ab initio molecular simulations and density functional theory calculations reveal that bismuth atoms in the liquid state are the most energetically favorable sites for the CO2RR intermediates, superior to solid Bi-sites, as well as joint GaBi-sites. This study opens an avenue for fabricating high-performing liquid-state metallic catalysts that cannot be reached by elementary metals under electrocatalytic conditions.

Properties of the ionization region in a magnetron plasma at gas-aggregation-source-relevant pressure regime explored using a global model

Abstract A global (volume averaged) model is developed for the ionization region of a gas aggregation source (GAS) plasma. The case of using argon gas and a copper target is considered. The model describes the densities of thermal and hot electrons, argon and copper ions, copper atoms and argon atoms in different excited states, the temperature of thermal electrons, the kinetic energies of the ions with which they bombard the target, the sheath width near the target cathode and the energy fluxes by different plasma species to a planar probe in the ionization region. Also, the fraction of input power is estimated which is dissipated to energize the thermal electrons in the ionization region. The gas discharge properties are analysed for different pressures and discharge currents under conditions corresponding to the experimental conditions (Gauter S et al 2018 J. Appl. Phys. 124 073301). The calculated pressure- and current-dependences for the GAS properties are used to explain the measured dependences for the deposition rate and the energy flux. It is found that the deposition rate increases with increasing discharge current because of the growth of currents of copper atoms and ions. With increasing pressure, the rate decreases due to drop of the densities of copper atoms and ions because of decreasing the kinetic energies of the ions with which they bombard the target. The model indicates that in the gas-aggregation-source relevant pressure regime, the energy flux by ions dominates over the energy fluxes of other plasma species.

Kinetics of Surface Wettability of Aromatic Polymers (PET, PS, PEEK, and PPS) upon Treatment with Neutral Oxygen Atoms from Non-Equilibrium Oxygen Plasma

The wettability of polymers is usually inadequate to ensure the appropriate spreading of polar liquids and thus enable the required adhesion of coatings. A standard ecologically benign method for increasing the polymer wettability is a brief treatment with a non-equilibrium plasma rich in reactive oxygen species and predominantly neutral oxygen atoms in the ground electronic state. The evolution of the surface wettability of selected aromatic polymers was investigated by water droplet contact angles deposited immediately after exposing polymer samples to fluxes of oxygen atoms between 3 × 1020 and 1 × 1023 m−2s−1. The treatment time varied between 0.01 and 1000 s. The wettability evolution versus the O-atom fluence for all aromatic polymers followed similar behavior regardless of the flux of O atoms or the type of polymer. In the range of fluences between approximately 5 × 1020 and 5 × 1023 m−2, the water contact angle decreased exponentially with increasing fluence and dropped to 1/e of the initial value after receiving the fluence close to 5 × 1022 m−2.

Quantum states and static field ionization of a cylindrical confined hydrogen atom: A diffusion Monte Carlo study

AbstractIn this article, the diffusion Monte Carlo (DMC) method is applied to the study of the quantum states of a hydrogen atom confined into a cylindrical potential well. We present an independent reproduction of previous studies based on different methods, in particular the energy eigenvalues for ground and selected excited states and the polarizability of the ground state, both for finite and infinite cylinders. The static field ionization of ground and excited states of the confined atom is discussed, including the determination of the potential energy surface and equilibrium position of the proton. This study provides a further demonstration of the versatility of the DMC method for this and analogous problems.

Cross-calibration of quantum atomic sensors for pressure metrology

Quantum atomic sensors have shown great promise for vacuum metrology. Specifically, the density of gas particles in vacuum can be determined by measuring the collision rate between the particles and an ensemble of sensor atoms. This requires preparing the sensor atoms in a particular quantum state, observing the rate of changes of that state, and using the total collision rate coefficient for state-changing collisions to convert the rate into a corresponding density. The total collision rate coefficient can be known by various methods, including quantum scattering calculations using a computed interaction potential for the collision pair, measurements of the post-collision sensor-atom momentum recoil distribution, or empirical measurements of the collision rate at a known density. Observed discrepancies between the results of these methods call into question their accuracy. To investigate this, we study the ratio of collision rate measurements of co-located sensor atoms, 87Rb and 6Li, exposed to natural abundance versions of H2, He, N2, Ne, Ar, Kr, and Xe gases. This method does not require knowledge of the test gas density and is, therefore, free of the systematic errors inherent in efforts to introduce the test gas at a known density. Our results are systematically different at the level of 3% to 4% from recent theoretical and experiment measurements. This work demonstrates a model-free method for transferring the primacy of one atomic standard to another sensor atom and highlights the utility of sensor-atom cross-calibration experiments to check the validity of direct measurements and theoretical predictions.

MMC Array to Study X-Ray Transitions in Muonic Atoms

AbstractThe QUARTET collaboration aims to significantly improve the precision of the absolute nuclear charge radii of light nuclei from Li to Ne by using an array of metallic magnetic calorimeters to perform high-precision X-ray spectroscopy of low-lying states in muonic atoms. A proof-of-principle measurement with lithium, beryllium and boron is planned for fall 2023 at the Paul Scherrer Institute. We discuss the performance achieved with the maXs-30 detector module to be used. To place the detector close to the target chamber where the muon beam will impact the material under study, we have developed a new dilution refrigerator sidearm. We further discuss the expected efficiency given the transparency of the X-ray windows and the quantum efficiency of the detector. The expected muonic X-ray rate combined with the high resolving power and detection efficiency of the detector suggest that QUARTET will be able to study the de-excitation of light muonic atoms at an unprecedented level, increasing the relative energy resolution by up to a factor of 20 compared to conventional detector techniques.

Combating Atherosclerosis with Chirality/Phase Dual-Engineered Nanozyme Featuring Microenvironment-Programmed Senolytic and Senomorphic Actions.

Senescence plays a critical role in the development and progression of various diseases. This study introduces an amorphous, high-entropy alloy nanozyme-based therapeutic designed to combat senescence. We start by screening ligands to optimize the synthesis of the amorphous nanozyme. By adjusting the nanozyme's composition and surface properties, we analyze its catalytic performance under both normal and aging conditions, confirming that peroxide and superoxide dismutase activity are crucial for its anti-aging therapeutic function. Subsequently, we validate the chiral-dependent therapeutic effects and demonstrate the senolytic performance of D-handed PtPd2CuFe across several aging models. Through proteomic and transcriptome analyses, we explore the mechanism underlying the senolytic action exerted by nanozyme in depth. We confirm that exposure to senescent conditions led to the enrichment of copper and iron atoms in the nanozyme's lower oxidation states, disrupting the iron-thiol cluster in mitochondria and lipoic acid transferase, as well as oxidizing unsaturated fatty acids. These actions triggered a cascade of cuproptotic and ferroptotic cell death. Additionally, we found that the nanozyme's anti-aging effects depend on concentration. Even an ultra-low dose of the therapeutic can act as a senomorphic, reducing the effects of senescence. Given its broad-spectrum action and concentration-adjustable anti-aging potential, we confirmed the remarkable therapeutic capability of D-handed PtPd2CuFe in managing atherosclerosis, a disease involving various types of senescent cells. This article is protected by copyright. All rights reserved.

Deterministic generation of highly squeezed GKP states in ultracold atoms

We demonstrate a method for encoding Gottesman–Kitaev–Preskill (GKP) error-correcting qubits with single ultracold atoms trapped in individual sites of a deep optical lattice. Using quantum optimal control protocols, we demonstrate the generation of GKP qubit states with 10 dB squeezing, which is the current minimum allowable squeezing level for use in surface code error correction. States are encoded in the vibrational levels of the individual lattice sites and generated via phase modulation of the lattice potential. Finally, we provide a feasible experimental protocol for the realization of these states. Our protocol opens up possibilities for generating large arrays of atomic GKP states for continuous-variable quantum information.

A Multi-Interface Structure of Graphdiyne/Cobalt Oxides for Chlorine Production.

A challenge facing the chlor-alkali process is the lack of electrocatalyst with high activity and selectivity for the efficient industrial production of chlorine. Herein the authors report a new electrocatalyst that can generate multi-interface structure by in situ growth of graphdiyne on the surface of cobalt oxides (GDY/Co3O4), which shows great potential in highly selective and efficient chlorine production. This result is due to the strong electron transfer and high density charge transport between GDY and Co3O4 and the interconversion of the mixed valence states of the Co atoms itself. These intrinsic characteristics efficiently enhance the conductivity of the catalyst, facilitate the reaction kinetics, and improve the overall catalytic selectivity and activity. Besides, the protective effect of the formed GDY layer is remarkable endowing the catalyst with excellent stability. The catalyst can selectively produce chlorine in low-concentration of NaCl aqueous solution at room temperature and pressure with the highest Faraday efficiency of 80.67% and an active chlorine yield rate of 184.40mg h-1 cm-2, as well as superior long-term stability.

Microwave photo-association of fine-structure-induced Rydberg (n+2)D5/2nFJ macro-dimer molecules of cesium

Long-range (n+2)D5/2nFJ Rydberg macro-dimers are observed in an ultracold cesium Rydberg gas for 39≤n≤48. Strong dipolar flip (〈D5/2F5/2|V̂dd|F5/2D5/2〉, 〈D5/2F7/2|V̂dd|F7/2D5/2〉) and cross (〈D5/2F7/2|V̂dd|F5/2D5/2〉) couplings lead to bound, fine-structure-mixed (n+2)D5/2nFJ macro-dimers at energies between the FJ fine-structure levels. The (n+2)D5/2nFJ macro-dimers are measured by microwave photo-association from optically prepared [(n+2)D5/2]2 Rydberg-pair precursor states. Calculated adiabatic potential curves are used to elucidate the underlying physics and to model the macro-dimer spectra, with good overall agreement. Microwave photo-association allows Franck-Condon tuning, which we have studied by varying the detuning of a Rydberg-atom excitation laser. Further, in Stark spectroscopy, we have measured molecular DC electric polarizabilities that are considerably larger than those of the atomic states. The large molecular polarizabilities are unexpected and may be caused by high-ℓ mixing. The observed linewidths of the Stark-shifted molecular lines provide initial evidence for intramolecular induced-dipole-dipole interaction. Published by the American Physical Society 2024

The atomic configuration and metallic state of extrinsic defects in Nb-doped BiFeO3 thin films

Defects in ferroelectric materials can cause microscopic strain and electron doping, which opens up new possibilities for unique physical properties in nanoelectronics. However, comprehending the relationship between these deep-buried defect configurations and the resulting physical properties is a long-term challenge. Here, utilizing the integrated differential phase imaging technique equipped in scanning transmission electron microscopy combined with energy dispersive X-ray spectroscopy, we show the full element-resolved atomic configuration of characteristic extrinsic defects in Nb-doped epitaxial BiFeO3 thin films. Atomic-resolution characterization reveals that the Nb doping substitutes Fe at the center of an oxygen octahedron and creates Fe vacancies near the defect core, leading to the formation of one perovskite cell-wide BiNbO3 chain that is expanded by 19 % in perovskite cell volume and rotated by 45° relative to the matrix lattice. Further quantitative analysis of the defect demonstrates that the ferroelectric polarization distribution around the dopant-induced defects displays a “head-to-head” configuration, indicating the accumulation of negative charges. Supported by electron energy loss spectroscopy and density functional theory calculations, the linear defect leads to one-dimensional metallic channels embedded within the ferroelectric BiFeO3 matrix. These atomic-scale findings establish the structure-functionality relationship of extrinsic defect in Nb-doped BiFeO3 thin films, providing new insight into their fundamental understanding and potential use in low-dimensional nanoelectronics devices.

Bose-Einstein condensation of non-ground-state caesium atoms

Bose-Einstein condensates of ultracold atoms serve as low-entropy sources for a multitude of quantum-science applications, ranging from quantum simulation and quantum many-body physics to proof-of-principle experiments in quantum metrology and quantum computing. For stability reasons, in the majority of cases the energetically lowest-lying atomic spin state is used. Here, we report the Bose-Einstein condensation of caesium atoms in the Zeeman-excited mf = 2 state, realizing a non-ground-state Bose-Einstein condensate with tunable interactions and tunable loss. We identify two regions of magnetic field in which the two-body relaxation rate is low enough that condensation is possible. We characterize the phase transition and quantify the loss processes, finding unusually high three-body losses in one of the two regions. Our results open up new possibilities for the mixing of quantum-degenerate gases, for polaron and impurity physics, and in particular for the study of impurity transport in strongly correlated one-dimensional quantum wires.

THE ROLE OF ATOMIC SCATTERING FACTORS IN DETERMINING THE MINERAL COMPOSITION OF THE BAZHENOV SUITE'S ROCKS

For the first time, it was demonstrated, that the use of standard atomic-structural parameters of minerals in X-ray diffraction (XRD) analysis to determine the phase composition in the Bazhenov suite's core is incorrect and most often leads to inaccurate information when calculating their quantitative ratio. In particular, by decomposing the XRD — based quantitative data on the mineral composition of the core of the Bazhenov suite into the main rock-forming oxides and further comparing them with reliable X-ray fluorescence spectrometry (XRF) data, an unsatisfactory convergence between them was established. At the same time, significant differences in the results of XRD and XRF have been shown in terms of oxides of silicon, sodium, magnesium, potassium, and iron, both at large and small mass fractions. It has been found that even with perfect XRD, achieved by optimizing the standard mineral structure parameters (lattice period, crystallite size, crystal lattice microdistortion, absorption coefficient, crystallographic texture, background) and achieving a very high degree of convergence (more than 95%) of experimental and theoretical diffractograms, the differences between oxide forms are still significant. It is shown, that the results of XRD of Bazhenov suite are questioned due to detected inconsistencies in oxide forms. Using the analysis of multiple factors and data from diffractograms of many samples, it has been established that the identified differences are primarily caused by the use of incorrect initial atomic-structure parameters of minerals in modeling. It is shown that rock minerals in the Bazhenov suite are primarily characterized by significant changes in the values of atomic scattering factors and significant displacements of atomic positions in the nodes of the crystal lattice, caused by the action of the high pressures and temperatures in the formation. For the first time, the XRD algorithm that has been developed, is presented and implemented in Bazhenov suite rocks, with consideration of the state of atoms in the analyzed mineral. Furthermore, it was found that the authors XRD approach enables the identification and quantification of the Bazhenov suite minerals with a relatively low content, which are challenging to identify during traditional XRD.

Production of High-Coercive nanostructured ND-fE-B alloy by chemical method

For the first time, a nanostructured alloy powder with high coercive force was obtained by a chemical method without the addition of Dy, which can compete with physical methods of production. The work carried out a study of the influence of stoichiometric composition on the magnetic properties of nanostructured Nd-Fe-B alloys. Alloys with different contents of Nd, Fe, and B were synthesized: Nd12Fe84B6, Nd14Fe80B6, Nd16Fe76B8, and Nd16Fe72B8. With a decrease in the iron content in the first two compositions, a decrease in the iron content in the soft magnetic phase α-Fe was observed, which led to an increase in the coercive force Hc and a decrease in the values of Ms and Mr. Experiments have shown that an increase in the content of Nd and B promotes the formation of the hard magnetic phase Nd2Fe14B and an increase in the coercive force. For example, the nanostructured Nd16Fe76B8 alloy demonstrated a maximum coercive force of Hc = 8439 Oe, while compensating for the values of Ms (109 emu*g−1) and Mr (78 emu*g−1). A comprehensive study of the nanostructured Nd16Fe76B8 alloy was carried out, including structural analysis. XRD using FullProff and Vesta software revealed the tetragonal crystal structure of the Nd2Fe14B phase, providing details of the atomic arrangement. The unit cell contains four layers with Nd and Fe atoms, and boron atoms are embedded in the center of the octahedron of Nd and Fe atoms, playing an important role in the magnetic exchange interaction. The results of Mössbauer spectroscopy confirmed the presence of the Nd2Fe14B phase and revealed details of the state of Fe atoms in the structure of six sextets.

A novel state-resolved actinometry method to determine the nitrogen atom number density in the ground state and intra-shell excited states in low-pressure electron cyclotron resonance plasmas

The active-particle number density is a key parameter for plasma material processing, space propulsion, and plasma-assisted combustion. The traditional actinometry method focuses on measuring the density of the atoms in the ground state, but there is a lack of an effective optical emission spectroscopy method to measure intra-shell excited-state densities. The latter atoms have chemical selectivity and higher energy, and they can easily change the material morphology as well as the ionization and combustion paths. In this work, we present a novel state-resolved actinometry (SRA) method, supported by a krypton line-ratio method for the electron temperature and density, to measure the number densities of nitrogen atoms in the ground and intra-shell excited states. The SRA method is based on a collisional-radiative model, considering the kinetics of atomic nitrogen and krypton including their excited states. The densities measured by our method are compared with those obtained from a dissociative model in a miniature electron cyclotron resonance (ECR) plasma source. Furthermore, the saturation effect, in which the electron density remains constant due to the microwave propagation in an ECR plasma once the power reaches a certain value, is used to verify the electron density measured by the line-ratio method. An ionization balance model is also presented to examine the measured electron temperature. All the values obtained with the different methods are in good agreement with each other, and hence a set of verified rate coefficient data used in our method can be provided. A novel concept, the ‘excited-state system’, is presented to quickly build an optical diagnostic method based on the analysis of quantum number propensity and selection rules.

Energy and Z dependence of low velocity Nq+ ion induced M X-ray relative intensities for some heavy elements

The intensity ratios, IMk/IMn (exp)(k = ξ, γ, m1; n = total, αβ), for some heavy elements, 70Yb, 79Au, 81Tl, 82Pb and 83Bi induced by 1000 keV−1750 keV Nq+ (q = 4, 5) ions have been measured in order to investigate their dependence on the projectile energy and atomic number of the respective target elements. The measured intensity ratios have been compared with two sets of values calculated using the Mj (j = 1–5) sub-shell ionization cross sections based on the ECPSSR-UA model, the X-ray emission rates based on the Dirac-Hartree Slater (DHS) model, two sets of the fluorescence and Coster-Kronig yields based on the DHS model and those evaluated by McGuire employing non-relativistic Hartree-Slater model. Significant differences have been observed between the present measured IMk/IMαβ (exp) (k = ξ, γ, m1) intensity ratios and those calculated using independent particle approximation (IPA) models based single atomic vacancy state physical parameters.

Static and dynamic atom displacements in nanocrystalline powders from diffraction analysis at finite temperature

Static and dynamic atom displacements in nanocrystalline powders from diffraction analysis at finite temperature

Phosphine Substituted N‐coordinated Stannylene: Efficient Catalyst in Ketone Hydroboration.

P‐substituted stannylene (Ph2PCH2)(L)Sn containing N,C,N‐chelated ligand (L = [2,6‐(Me2NCH2)2C6H3]) was prepared. Complex was further oxidized to prepare P‐substituted organotin(IV) compounds (Ph2PCH2)(L)SnX2. Finally, P(S)‐substituted N‐coordinated stannylene [(Ph2P(S)CH2](L)Sn containing P atom in the oxidation state +V was also prepared. All these P‐substituted organotins were tested as the catalysts for the hydroboration of ketones to see the effect of oxidation numbers of Sn/P atoms. Stannylene (Ph2PCH2)(L)Sn showed remarkable conversions with TOF about 1800 h‐1 and it is suitable to the reduction of several ketones. The mechanistic studies are also discussed.

Parallel Gate Fidelity of Flip‐Flop Qubits in Small 1D‐ and 2D‐Arrays in a Noisy Environment

AbstractThe long coherence time of donor atom nuclear spin states and of its bounded electron in can be exploited to define a qubit. This work is focused on a type of donor‐ and quantum dot‐based qubit, the flip‐flop (FF) qubit, that leverages antiparallel electron‐nuclear spin states of a donor atom controlled by an electric field. It can provide long‐range inter‐qubit interactions in the order of some hundreds of nanometers, thus relaxing the common constraints and tolerances on inter‐qubit distances in donor‐based qubits. Simulation results of linear array (LA) and square array (SA) of four FF qubits are presented to study the effect of noise, idle qubits, and simultaneous gating (parallel gating) on gate fidelity. The impact of noise and qubit mutual coupling for both considered types of array are presented and the obtained fidelity results are compared.

High-order magnetic resonance in the presence of strong longitudinal radio-frequency magnetic field based on atomic alignment states

High-order magnetic resonance in the presence of strong longitudinal radio-frequency magnetic field based on atomic alignment states