Atomic States Research Articles

A Review on The Nitrogen Laser

Abstract: A nitrogen laser is a type of gas laser that uses molecular nitrogen as its gain medium to operate in the ultraviolet (UV) spectrum. First created in 1963, nitrogen lasers were first put to use in commerce in 1972. A nitrogen laser is a type of gas laser that uses molecular nitrogen as its gain medium to operate in the ultraviolet (UV) spectrum. First created in 1963, nitrogen lasers were first put to use in commerce in 1972.Applications for nitrogen lasers can be found in physics, chemistry, and medical research. The principle of operation for nitrogen lasers is a quick electrical discharge through nitrogen gas. Liquid nitrogen or a gas cylinder might be used to supply the nitrogen gas. The UV-wavelength laser light has a short pulse width and a high intensity. The principle of operation for nitrogen lasers is a rapid electrical discharge via nitrogen gas. Liquid nitrogen or a gas cylinder might be used to supply the nitrogen gas. The laser light has a short pulse width, high intensity, and is released into the ultraviolet spectrum. Electricity is used by the nitrogen laser to excite the nitrogen. The electrons in the laser strike the nitrogen atoms in the air when an electric spark passes through a spark gap, stimulating them into a metastable condition. A photon with a wavelength of 337 nm causes stimulated emission and the creation of a laser state in the excited nitrogen atoms. Electricity is used by the nitrogen laser to excite the nitrogen. The nitrogen atoms in the air are excited into a metastable condition when an electric spark passes through a spark gap in the laser. A photon with a wavelength of 337 nm causes stimulated emission and the creation of a laser state in the excited nitrogen atoms. [22]

Interfacial Coupling Induced Discrete Orientation of Epitaxial Graphene on High‐Index Cu Substrates

AbstractControlled and precise synthesis of materials has been a central pursuit in academia and industry. With the rise of twistronics research, there is growing demand for synthesizing orientation‐controlled 2D materials with atomic precision. Previous theories for 2D materials can predict graphene (Gr) growth on low‐index metal substrates but fail to explain the discrete orientations on most high‐index substrates, inconsistent with experimental data. Using density functional theory (DFT) and ab‐initio molecular dynamics (AIMD), this study explores graphene growth on high‐index substrates, showing that atomic steps do not dominate in trapping C atoms or driving preferential graphene nucleation at high temperatures. Thus, the possibility of intrinsic atomic steps in inducing graphene orientation on high‐index substrates is ruled out. Interfacial coupling strength between graphene and substrates is quantified using a close contact index (CCI), linking atomic structure and electronic states. The coupling between graphene and high‐index Cu surfaces is generally weak, reducing substrate anchoring and increasing graphene orientation dispersion. The extension of this theory to bilayer graphene (BLG) reveals competition between Gr/Cu interfacial coupling and Gr/Gr interlayer coupling, offering insights for controlling twist angles. This theory explains the discrete orientations on high‐index substrates, providing a theoretical basis for synthesizing orientation‐controlled graphene.

Kinetic Study of the Reactions of Ground State Atomic Carbon and Oxygen with Nitrogen Dioxide over the 50-296 K Temperature Range.

The kinetics of the reactions of nitrogen dioxide, NO2, with atomic oxygen and atomic carbon in their ground triplet states (3P) have been studied at room temperature and below using a supersonic flow (Laval nozzle) reactor. O(3P) and C(3P) atoms (hereafter O and C respectively) were created in situ by the pulsed laser photolysis of the precursor molecules NO2 at 355 nm and CBr4 at 266 nm, respectively. While the progress of the O + NO2 reaction was followed by detecting O atoms by a chemiluminescent tracer method, progress of the C + NO2 reaction was followed by detecting C atoms directly by vacuum ultraviolet laser-induced fluorescence at 116 nm. The measured rate constants for the O + NO2 reaction are found to be in excellent agreement with earlier work at higher temperatures and extend the available kinetic data for this process down to 50 K. The present work represents the first kinetics study of the C + NO2 reaction. Although both reactions display rate constants that increase as the temperature falls, a more substantial rate increase is observed for the O + NO2 reaction. The effects of these reactions on the simulated abundances of interstellar NO2 and related compounds were tested using a gas-grain model of the dense interstellar medium, employing expressions for the rate constants of the form, k(T) = α(T/300)β, with α = 1 × 10-11 cm3 s-1 and β = -0.65 for the O + NO2 reaction and α = 2 × 10-10 cm3 s-1 and β = -0.11 for the C + NO2 reaction. Although these simulations predict that gas-phase NO2 abundances are low in dense interstellar clouds, NO2 abundances on interstellar dust grains are predicted to reach reasonably high levels, indicating the potential for detection of this species in warmer regions.

Strong error bounds for Trotter and strang-splittings and their implications for quantum chemistry

Efficient error estimates for the Trotter product formula are central in quantum computing, mathematical physics, and numerical simulations. However, the Trotter error's dependency on the input state and its application to unbounded operators remains unclear. Here, we present a general theory for error estimation, including higher-order product formulas, with explicit input state dependency. Our approach overcomes two limitations of the existing operator-norm estimates in the literature. First, previous bounds are too pessimistic as they quantify the worst-case scenario. Second, previous bounds become trivial for unbounded operators and cannot be applied to a wide class of Trotter scenarios, including atomic and molecular Hamiltonians. Our method enables analytical treatment of Trotter errors in chemistry simulations, illustrated through a case study on the hydrogen atom. Our findings reveal the following: (i) for states with fat-tailed energy distribution, such as low-angular-momentum states of the hydrogen atom, the Trotter error scales worse than expected (sublinearly) in the number of Trotter steps; (ii) certain states do not admit an advantage in the scaling from higher-order Trotterization and, thus, the higher-order Trotter hierarchy breaks down for these states, including the hydrogen atom's ground state; (iii) the scaling of higher-order Trotter bounds might depend on the order of the Hamiltonians in the Trotter product for states with fat-tailed energy distribution. Physically, the enlarged Trotter error is caused by the atom's ionization due to the Trotter dynamics. Mathematically, we find that certain domain conditions are not satisfied by some states so higher moments of the potential and kinetic energies diverge. Our analytical error analysis agrees with numerical simulations, indicating that we can estimate the state-dependent Trotter error scaling genuinely. Published by the American Physical Society 2024

Theoretical analysis and predictions for the two-neutrino double electron capture of 124Xe

Abstract We provide a complete theoretical description of the two-neutrino electron capture in 124Xe, improving both the nuclear and the atomic structure calculations. We improve the general formalism through the use of the Taylor expansion method, leading to higher-order terms in the decay rate of the process. The nuclear part is treated with pn-QRPA and interacting shell model (ISM) methods. The nuclear matrix elements (NMEs) are calculated with the pn-QRPA method with isospin restoration by fixing the input parameters so that the experimental decay rate is reproduced, resulting in values significantly lower than in previous calculations. The validity of the pn-QRPA NMEs is tested by showing their values to be comparable with the ones for double-beta decay with the emission of two antineutrinos of 128,130Te, which have similar pairing features. Within the ISM, we reproduce the total experimental half-life within a factor of two and predict the capture fraction to the KK channel of about 74%. We also predict the capture fractions to other decay channels and show that for the cumulative decay to the KL1–KO1 channels, a capture fraction of about 24% could be observed experimentally. On the atomic side, calculations are improved by accounting for the Pauli blocking of the decay of innermost nucleon states and by considering all s-wave electrons available for capture, expanding beyond the K and L1 orbitals considered in previous studies. We also provide improved atomic relaxation energies of the final atomic states of 124Te, which may be used as input for background modeling in liquid Xenon experiments.

Application of the Jost Function for Calculation of the Ground State of the Lithium Atom

Application of the Jost Function for Calculation of the Ground State of the Lithium Atom

Replenish the Electron-Deficient State of Carbonyl Carbon Atoms to Achieve Stable Li-S Battery.

Carbonate-based electrolytes are widely used in Li-ion batteries (LIBs) due to their safe, stable properties and wide operating temperature range. However, the nucleophilic attack at carbonyl carbon atoms by polysulfide anions and the low solubility of lithium nitrate (LiNO3<0.1m) in carbonate-based electrolytes seriously hinder the application of lithium-sulfur (Li-S) batteries in carbonate-based electrolytes. Herein, the electrophilicity of carbonyl carbon atoms is gradually reduced through solvent molecules redesign, eliminated the attack of polysulfide anions on carbonyl carbon atoms, and also changed the intermolecular interactions in the electrolyte, improving the solubility of LiNO3 (>1.0m) and forming stable LiNxOy-containing SEI on the surface of the lithium metal. The assembled Li-S battery with these designed solvent molecules delivers an initial discharge capacity of 1251.7mAhg-1 at 0.1C. In addition, the lithium-sulfur battery assembled with the designed solvent molecule has a discharge capacity of 631mAhg-1 after 420 cycles at 0.2 C, with a capacity retention of ≈60%. Moreover, the Li||Li symmetrical cell shows stable cycle performance over 1200h at 0.5mAcm-2 and 0.5mAhcm-2.

Variational Hirshfeld Partitioning: General Framework and the Additive Variational Hirshfeld Partitioning Method.

We introduce the general mathematical framework of variational Hirshfeld partitioning, wherein the best possible approximation to a molecule's electron density is obtained by minimizing the f-divergence between the molecular density and a non-negative linear combination of (normalized) basis functions. This framework subsumes several existing methods that variationally optimize their pro-atoms, like (Gaussian) iterative stockholder analysis (ISA and GISA) and minimal basis iterative stockholder partitioning (MBIS), and provides a solid foundation for developing mathematically rigorous partitioning schemes. In this paper, we delve into the mathematical underpinnings of Hirshfeld-inspired partitioning schemes and show that among all the valid f-divergence measures only the extended Kullback-Leibler is a suitable choice. This led us to develop a novel partitioning scheme, called additive variational Hirshfeld (AVH), which constructs the pro-molecular density as a convex linear combination of the densities from selected states of isolated atoms and atomic ions. The AVH method is size-consistent with a unique solution and provides a straightforward approach for adding constraints for fragment properties. It also results in an intuitively appealing valence-bond-like decomposition of the molecular density as a weighted average of the densities of the atomic states in the molecule; that is, the AVH atomic density is a minimal deformation of the corresponding isolated atomic reference state's density. Compared to other variational Hirshfeld variants, our numerical results show that AVH yields chemically interpretable and sensible atomic charges that are not excessively large and demonstrate computational robustness.

Al-N3 Bridge Site Enabling Interlayer Charge Transfer Boosts the Direct Photosynthesis of Hydrogen Peroxide from Water and Air.

Manipulating the electronic environment of the reactive center to lower the energy barrier of the rate-determining water oxidation step for boosting the direct generation of H2O2 from water, air, and sunlight is fascinating yet remains a grand challenge. Driven by a first-principles screening across a series of metal single atoms in carbon nitride, we report a class of an Al-N3 bridge site enabling interlayer charge transfer in carbon nitride nanotubes (CNNT-Al) for the highly efficient photosynthesis of H2O2 directly from water, oxygen, and sunlight. We demonstrate that the interlayered Al-N3 bridge site in CNNT-Al is able to activate the neighboring surface N atom for promoting the rate-determining step of the two-electron water oxidation to H2O2. It is also able to act as a bridge for enhancing the vertical interlaminar charge transfer due to the hybridization between the 3s and 3p states of the interstitial Al atom and the conduction band of two adjacent carbon nitride layers. Collectively, these factors lead to a highest photocatalytic mass activity of 1410.2 μmol g-1 h-1 (with a photocatalyst concentration of 1 g L-1) for direct photosynthesis of H2O2 out of all CN-based photocatalysts and a 7-fold higher solar-to-chemical conversion efficiency (0.73%) compared to that of the natural photosynthesis of typical plants (∼0.1%). Most importantly, the CNNT-Al-based flow reactor can steadily produce H2O2 for 200 h and be directly used for the on-site degradation of organic dye in water. The CNNT-Al-based flow reactor can also kill a 10 times higher concentration of bacteria in deionized water than that in natural water with 100% efficiency, which makes our design economically appealing for practical water treatment.

Engineering of hyperentangled complex quantum networks

Abstract We propose a novel scheme to engineer the atomic hyperentangled cluster and ring graph states invoking cavity-QED technique for applicative relevance to quantum biology and quantum communications utilizing the complex quantum networks. These states are engineered using both external quantized momenta states and energy levels of neutral atoms under off-resonant and resonant Atomic Bragg Diffraction (ABD) technique. The study of dynamical capacity and potential efficiency have certainly enhanced the range of usefulness of these states. In order to assess the operational behavior of such states when subjected to a realistic noise environment has also been simulated, demonstrating long enough sustainability of the proposed states. Moreover, experimental feasibility of the proposed scheme has also been elucidated under the prevailing cavity-QED research scenario.

Shape-dependent CO chemisorption on Pt13 nanocluster deposited on reduced TiO2(110)

This article delves into the impact of nanoparticle shape on CO chemisorption and the reactivity of Pt13 nanocatalysts supported on reduced TiO2(110). Distinct reactivity in carbon monoxide adsorption is observed among nanoparticles, all composed of 13 platinum atoms but varying in shape. The calculated formation and CO adsorption energies are correlated to the electronic properties of the system and the oxidation states of the Pt atoms involved. Through an analysis of band shifting during the deposition of Pt clusters onto the oxide, and a comparison of the valence band maximum with the measured oxidation potential for the CO to CO2 reaction, we make predictions about the system's oxidation capability in this reaction. Our findings suggest that Pt13 clusters with cuboid, double triangle DT2 and octahedral Oh shapes, supported on the surface, are particularly advantageous for catalyzing the conversion of CO to CO2. Within these geometries, several configurations for CO adsorption are evaluated, focusing on the ratio between anionic and cationic Pt sites. This ratio appears to govern the activity for CO oxidation, aligning with recent experimental reports.

A collisional-radiative model for atmospheric-pressure low-temperature air discharges

Plasma-assisted combustion technology has been a hot spot in aero-engines and scramjet-engines. The electron density is a key discharge parameter related to the active-particle density. The latter has been considered playing an important role in the above applications by the kinetic effect. In this work, an atmospheric pressure air plasma collisional-radiative model considering the excited states of atomic nitrogen and oxygen is built based on previous widely kinetic investigations of molecules and radicals, as well as their excited states. The excited states, especially the atomic nitrogen and oxygen states were less investigated in previous works. The emission intensity distributions from the model have a good agreement with those measured in the glide arc plasma with two discharge modes, as well as the microwave plasma. Based on the kinetics of molecular and atomic emitting states, the line-ratio method is presented to determine the electron density. The N2(337 nm)/O(844 nm) and N2(337 nm)/NO(γ) line ratios are used for the glide arc plasma and microwave plasma torch, respectively. Besides, the kinetics of the excited states involved with two line-ratios are also investigated in the two types of discharges. Combined with the atmospheric pressure actinometry method, the kinetic effect of the plasma-assisted combustion can be revealed quantitatively in the future.

Theoretical Study on BiCoO3: Pressure‐Tuned Transformation of Structure, Magnetism, Charge, and Spin State

AbstractThe atomic structures, electronic structures, magnetic properties, and spin states of BiCoO3 multiferroic material under hydrostatic pressure are comprehensively investigated by using first‐principles calculation based on density functional theory. Firstly, we found the pressure‐tuned structural symmetry transition from tetragonal P4 mm (No. 99) to cubic Pmm (No. 221) space group. The structural transformation prompts the Co─O polyhedral coordination transfer from a CoO5 pyramidal to a CoO6 distorted octahedron. Secondly, the pressure‐induced magnetic change from C‐type antiferromagnetic state to ferromagnetic state and then to paramagnetic configuration occurred after continuous compression of the volume. Essentially, the fundamental reason for the transition of the magnetic structure lies in the change of the internal atomic structure, such as the pressure induced abrupt changes of Co─O bond length and &lt;Co─O─Co&gt; bond angle. Meanwhile, an obvious volume collapse was observed when the pressure was applied to 51–56 GPa. Finally, as the pressure increases, the magnetism changes from C‐type antiferromagnetic state to paramagnetic configuration, accompanying the transformation from high spin state with b2g2eg2a1g1b1g1 configuration in pyramid structure to low spin state with t2g6eg0 in octahedral field. Therefore, our results demonstrate that applied hydrostatic pressure in BiCoO3 can trigger the transformation of structure, magnetism, charge, and spin state.

Downwind of the Atomic State: Atmospheric Testing and the Rise of the Risk Society

Downwind of the Atomic State: Atmospheric Testing and the Rise of the Risk Society

Modulating Spin of Atomic Manganese Center for High-Performance Oxygen Reduction Reaction.

Single atom catalysts (SACs) are promising non-precious catalysts for oxygen reduction reaction (ORR). Unfortunately, the ORR SACs usually suffer from unsatisfactory activity and in particular poor stability. Herein, we report atomically dispersed manganese (Mn) embedded on nitrogen and sulfur co-doped graphene as an efficient and robust electrocatalyst for ORR in alkaline electrolyte, realizing a half-wave potential (E1/2) of 0.883 V vs. reversible hydrogen electrode (RHE) with negligible activity degradation after 40,000 cyclic voltammetry (CV) cycles in 0.1 M KOH. Introducing sulfur (S) to form Mn-S coordination changes the spin state of single Mn atom from high-spin to low-spin, verified by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements as well as density functional theory (DFT) calculations, which effectively optimizes the oxygen intermediates adsorption over the single Mn atomic sites and thus greatly improves the ORR activity.

Modulating Spin of Atomic Manganese Center for High‐Performance Oxygen Reduction Reaction

AbstractSingle atom catalysts (SACs) are promising non‐precious catalysts for oxygen reduction reaction (ORR). Unfortunately, the ORR SACs usually suffer from unsatisfactory activity and in particular poor stability. Herein, we report atomically dispersed manganese (Mn) embedded on nitrogen and sulfur co‐doped graphene as an efficient and robust electrocatalyst for ORR in alkaline electrolyte, realizing a half‐wave potential (E1/2) of 0.883 V vs. reversible hydrogen electrode (RHE) with negligible activity degradation after 40,000 cyclic voltammetry (CV) cycles in 0.1 M KOH. Introducing sulfur (S) to form Mn−S coordination changes the spin state of single Mn atom from high‐spin to low‐spin, verified by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements as well as density functional theory (DFT) calculations, which effectively optimizes the oxygen intermediates adsorption over the single Mn atomic sites and thus greatly improves the ORR activity.

Gordon Decomposition of the Magnetizability of a Dirac One-Electron Atom in an Arbitrary Discrete Energy State

We present a Gordon decomposition of the magnetizability of a Dirac one-electron atom in an arbitrary discrete energy eigenstate, with a pointlike, spinless, and motionless nucleus of charge Ze. The external magnetic field, by which the atomic state is perturbed, is assumed to be weak, static, and uniform. Using the Sturmian expansion of the generalized Dirac–Coulomb Green function proposed by Szmytkowski in 1997, we derive a closed-form expressions for the diamagnetic (χd) and paramagnetic (χp) contributions to χ. Our calculations are purely analytical; the received formula for χp contains the generalized hypergeometric functions 3F2 of the unit argument, while χd is of an elementary form. For the atomic ground state, both results reduce to the formulas obtained earlier by other author. This work is a prequel to our recent article, where the numerical values of χd and χp for some excited states of selected hydrogenlike ions with 1⩽Z⩽137 were obtained with the use of the general formulas derived here.

Enhancing Oxygen Reduction Reaction of Single-Atom Catalysts by Structure Tuning.

Deciphering the fine structure has always been a crucial approach to unlocking the distinct advantages of high activity, selectivity, and stability in single-atom catalysts (SACs). However, the complex system and unclear catalytic mechanism have obscured the significance of exploring the fine structure. Therefore, we endeavored to develop a three-component strategy to enhance oxygen reduction reaction (ORR), delving deep into the profound implications of the fine structure, focusing on central atoms, coordinating atoms, and environmental atoms. Firstly, the mechanism by which the chemical state and element type of central atoms influence catalytic performance is discussed. Secondly, the significance of coordinating atoms in SACs is analyzed, considering both the number and type. Lastly, the impact of environmental atoms in SACs is reviewed, encompassing existence state and atomic structure. Thorough analysis and summarization of how the fine structure of SACs influences the ORR have the potential to offer valuable insights for the accurate design and construction of SACs.

Recent Progress in Molecular Oxygen Activation by Iron-Based Materials: Prospects for Nano-Enabled In Situ Remediation of Organic-Contaminated Sites.

In situ chemical oxidation (ISCO) is commonly used for the remediation of contaminated sites, and molecular oxygen (O2) after activation by aquifer constituents and artificial remediation agents has displayed potential for efficient and selective removal of soil and groundwater contaminants via ISCO. In particular, Fe-based materials are actively investigated for O2 activation due to their prominent catalytic performance, wide availability, and environmental compatibility. This review provides a timely overview on O2 activation by Fe-based materials (including zero-valent iron-based materials, iron sulfides, iron (oxyhydr)oxides, and Fe-containing clay minerals) for degradation of organic pollutants. The mechanisms of O2 activation are systematically summarized, including the electron transfer pathways, reactive oxygen species formation, and the transformation of the materials during O2 activation, highlighting the effects of the coordination state of Fe atoms on the capability of the materials to activate O2. In addition, the key factors influencing the O2 activation process are analyzed, particularly the effects of organic ligands. This review deepens our understanding of the mechanisms of O2 activation by Fe-based materials and provides further insights into the application of this process for in situ remediation of organic-contaminated sites.

Acceleration of Diffusion in Ab Initio Nanoreactor Molecular Dynamics and Application to Hydrogen Sulfide Oxidation.

The computational description of chemical reactivity can become extremely complex when multiple different reaction products and intermediates come into play, forming a chemical reaction network. Therefore, computational methods for the automated construction of chemical reaction networks have been developed in the last decades. One of these methods, ab initio nanoreactor molecular dynamics (NMD), is based on external forces enhancing reactivity by e.g., periodically compressing the system and allowing it to relax. However, during the relaxation process, a significant simulation time is required to allow energy to dissipate and molecules to diffuse, making this part of the NMD simulation computationally intensive. This work aims to improve NMD by accelerating the diffusion process in the relaxation phase. We systematically investigate the speedup of reaction discovery gained by diffusion acceleration, leading to a factor of up to 28 in discovery frequency. Diffusion-accelerated nanoreactor molecular dynamics (DA-NMD) is then used to construct a reaction network of hydrogen sulfide oxidation under atmospheric conditions, where reactions are automatically detected by a change in the bond order and bond distance. A reaction network of 108 molecular species and 399 elementary reactions was constructed starting from hydrogen sulfide, hydroxy radicals, and molecular oxygen covering a broad variety of sulfur-oxygen chemistry and oxidation states of the sulfur atom ranging from -II to +VI.