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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Features of the Emission Spectra of Ni-Like Ions. Application to Calculating the Wavelengths of Self-Photo-Pumped X-Ray Lasers

The energy levels and probabilities of radiative transitions to the ground state of Ni-like ions with Z = 36–51 are calculated. The energies of the upper working level 3d{sub 3/2}4f{sub 5/2} [J = 1] and the lower working level 3d{sub 3/2}4d{sub 3/2} [J = 1] of self-photo-pumped X-ray lasers along the sequence of Ni-like ions are studied. It is shown that, at the points of intersection of levels of the same parity, a strong interaction of these levels takes place, which leads to a redistribution of the oscillator strengths of the radiative transitions from these levels. Near the intersection points, the emission spectra change abruptly with variation in the nuclear charge Z.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Topological phase transition without single particle gap closing in strongly correlated systems

Here, in this study, we show two models where changing topology does not necessarily close the bulk insulating charge gap as demanded in the standard noninteracting picture. From extensive determinantal and dynamical cluster quantum Monte Carlo simulations of the half-filled and quarter-filled Kane-Mele-Hubbard model, we show that, for sufficiently strong interactions at either half- or quarter-filling, a transition between topological and trivial insulators occurs without the closing of a charge gap. To shed light on this behavior, we illustrate that an exactly solvable model reveals that while the single-particle gap remains, the many-body gap does, in fact, close. These two gaps are the same in the noninteracting system but depart from each other as the interaction turns on. We purport that for interacting systems, the proper probe of topological phase transitions is the closing of the many-body rather than the single-particle gap.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Surface spin-electron acoustic waves in magnetically ordered metals

Degenerate plasmas with motionless ions show existence of three surface waves: the Langmuir wave, the electromagnetic wave, and the zeroth sound. Applying the separated spin evolution quantum hydrodynamics to half-space plasma, we demonstrate the existence of the surface spin-electron acoustic wave (SSEAW). We study dispersion of the SSEAW. We show that there is hybridization between the surface Langmuir wave and the SSEAW at rather small spin polarization. In the hybridization area, the dispersion branches are located close to each other. In this area, there is a strong interaction between these waves leading to the energy exchange. Consequently, generating the Langmuir waves with the frequencies close to hybridization area we can generate the SSEAWs. Thus, we report a method of creation of the spin-electron acoustic waves.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

PVA Based Ternary Nanocomposites with Enhanced Properties Prepared by Using a Combination of Rice Starch Nanocrystals and Silver Nanoparticles

Ternary nanocomposite films exhibiting better properties were prepared by incorporating two different nanoparticles such as rice starch nanocrystals (RSN) and silver nanoparticles (AgNPs) together in polyvinyl alcohol (PVA) matrix at various concentrations. The morphological evaluation using atomic force microscopy revealed that the particle size of RSN nanoparticles varied from 50 to 125 nm. The nanocomposite films made using these nanoparticles were evaluated for its chemical, mechanical and thermal properties. FTIR spectra of the films revealed some specific vibrational bands of RSN along with the characteristic bands of PVA. The mechanical property analysis of nanocomposite films indicated better tensile strength and elongation properties, which can be attributed to the strong interaction of PVA with RSN and AgNPs. The thermal properties of these films were also evaluated. These ternary nanocomposites exhibited superior mechanical properties, which is very much beneficial as far as the end use applications are concerned.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Three-body Förster resonance of a new type in Rydberg atoms

The three-body Förster resonances 3 × nP{sub 3/2}(|M|) →nS{sub 1/2} + (n + 1)S{sub 1/2} + nP{sub 3/2}(|M*|), controlled by a constant electric field, were realised earlier by the authors in an ensemble of several cold Rydberg Rb atoms. One of the drawbacks of such resonances for potential application in three-qubit quantum gates is the proximity of the two-body Förster resonance 2 × nP{sub 3/2} → nS{sub 1/2} + (n + 1)S{sub 1/2}, as well as the possibility of their implementation only for states with values of the principal quantum numbers n ⩽38. A three-body resonance of a new type, 3 × nP{sub 3/2} → nS{sub 1/2} + (n + 1)S{sub 1/2} + nP{sub 1/2}, which can be realised for arbitrary n, is proposed and analysed. Its specific feature is also that the third atom transits into a state with a different total angular momentum J = 1/2, which has no Stark structure, so that the two-body resonance is completely absent. Numerical calculations showed that for not too strong interaction, it is possible to observe coherent three-body oscillations of the populations of collective states, which is of interest for developing new schemes of three-qubit quantum gates controlled by an electric field. (paper)

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Electronic Excitation Energy Transfer in an Array of CdS Quantum Dots on a Quasi-Two-Dimensional Surface

The optical spectra of films composed of spherical silicon-dioxide particles coated with small-radius CdS quantum dots are recorded and analyzed. Large shifts of the absorption and photoluminescence bands are detected and studied in relation to the concentration of quantum dots and to the pumping density and wavelength. Analysis of the experimental data shows that the effects are due to electronic excitation energy transfer by particles through the mechanism of tunneling induced by a strong interaction between quantum dots. The results obtained at low pumping densities and different excitation wavelengths make it possible to describe the size distribution of CdS quantum dots. This distribution can be adequately approximated with a Gaussian function.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Transition Energies and Absorption Oscillator Strengths for c{sub 4}{sup ′1}Σ{sub u}{sup +}−X{sup 1}Σ{sub g}{sup +}, b{sup ′1}Σ{sub u}{sup +}−X{sup 1}Σ{sub g}{sup +}, and c{sub 5}{sup ′1}Σ{sub u}{sup +}−X{sup 1}Σ{sub g}{sup +} Band Systems in N{sub 2}

Theoretical transition energies and absorption oscillator strengths for the c{sub 4}{sup ′1}Σ{sub u}{sup +} (v′ = 0–2, 5, 7, 8) − X{sup 1}Σ{sub g}{sup +}(v{sup ′′}=0--14) and c{sub 5}{sup ′1}Σ{sub u}{sup +} (v′ = 0, 2) − X{sup 1}Σ{sub g}{sup +} (v″ = 0–14) Rydberg bands, and b{sup ′1}Σ{sub u}{sup +} (v′ = 0–9, 11, 12, 14–19, 21, 22) − X{sup 1}Σ{sub g}{sup +} (v″ = 0–14) valence bands of molecular nitrogen are reported. The strong interaction between {sup 1}Σ{sub u}{sup +} states has been dealt with through a vibronic interaction matrix. As a consequence of the Rydberg-valence interaction, irregularities in the vibrational structure of the above band systems are observed. Good agreement is found with the scarce high-resolution data that are available for oscillator strengths. The new band oscillator strengths reported here may be useful for a reliable interpretation of the spectra from atmospheres of the Earth, Titan, and Triton, where N{sub 2} is the mayor constituent.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Microwave-assisted synthesis of well-shaped UiO-66-NH2 with high CO2 adsorption capacity

Highlights: • Well-shaped UiO-66-NH{sub 2} was prepared through microwave heating in a short time. • Addition of HAc improves crystallinity and CO{sub 2} adsorption capacity of the UiO-66-NH{sub 2}. • UiO-66-NH{sub 2} prepared by microwave heating shows a higher CO{sub 2}/N{sub 2} adsorption selectivity. - Abstract: In a detailed study, the influence of microwave irradiation, synthesis time and temperature, addition of acetic acid (HAc) as a modulator on the morphology, crystallinity and stability of UiO-66-NH{sub 2} is investigated to develop a reliable and reproducible strategy for the preparation of well-shaped UiO-66-NH{sub 2}. The UiO-66-NH{sub 2} were characterized by powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and gas adsorption. It is found that well-shaped UiO-66-NH{sub 2} with a high CO{sub 2} adsorption capacity can be synthesized in a short time by microwave heating. The UiO-66-NH{sub 2} crystals synthesized by microwave heating are of high quality and show a superior CO{sub 2} adsorption capacity (5.8 mmol/g at 273k and 1 bar) due to the strong interactions between the −NH{sub 2} group and CO{sub 2}. The CO{sub 2}/N{sub 2} selectivity of the obtained UiO-66-NH{sub 2} at 298 K and 1 bar is 66, which is much higher than that of the pristine UiO-66 of 17.8.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Electrically tuned hyperfine spectrum in neutral Tb( II )(Cp iPr5 ) 2 single-molecule magnet

Molecular spin qubits with long spin coherence time as well as non-invasive operation methods on such qubits are in high demand. It was shown that both molecular electronic and nuclear spin levels can be used as qubits. In solid state systems with dopants, an electric field was shown to effectively change the spacing between the nuclear spin qubit levels when the electron spin density is high at the nucleus of the dopant. Inspired by such solid-state systems, we propose that divalent lanthanide (Ln) complexes with an unusual electronic configuration of Ln 2+ have a strong interaction between the Ln nuclear spin and the electronic degrees of freedom, which renders electrical tuning of the interaction. Furthermore, as an example, we study electronic structure and hyperfine interaction of the 159 Tb nucleus in a neutral Tb(II)(Cp iPr5 ) 2 single-molecule magnet (SMM), which exhibits unusually long magnetization relaxation time, using the complete active space self-consistent field (CASSCF) method with spin–orbit interaction included within the restricted active space state interaction (RASSI). Our calculations show that the low-energy states arise from 4f 8 (6s,5d z 2 ) 1 , 4f 8 (5d x 2 -y 2 ) 1 , and 4f 8 (5d xy ) 1 configurations. We compute the hyperfine interaction parameters and the electronic–nuclear spectrum within our multiconfigurational approach. We find that the hyperfine interaction is about one order of magnitude greater than that for Tb(III)Pc 2 SMMs. This stems from the strong Fermi contact interaction between the Tb nuclear spin and the electron spin density at the nucleus that originates from the occupation of the (6s,5d) orbitals. We also uncover that the response of the Fermi contact term to electric field results in electrical tuning of the electronic–nuclear level separations. This hyperfine Stark effect may be useful for applications of molecular nuclear spins for quantum computing.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Tensor observables in electro- and photoreactions on the deuteron

The study of polarization effects in reactions with a simplest nucleus, deuteron, plays an important role for the investigation of deuteron structure as well as for the research of the properties of the strong interaction. However, data on the tensor observables in the electro- and photoreactions with deuteron appeared not so long ago. We present here a brief overview of the experiments on three such reactions with a deuteron: elastic scattering, photodisintegration and coherent photoproduction of the neutral pion.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Feedback by AGN Jets and Wide-angle Winds on a Galactic Scale

To investigate the differences in mechanical feedback from radio-loud and radio-quiet active galactic nuclei on the host galaxy, we perform 3D AMR hydrodynamic simulations of wide-angle, radio-quiet winds with different inclinations on a single, massive, gas-rich disk galaxy at a redshift of 2–3. We compare our results to hydrodynamic simulations of the same galaxy but with a jet. The jet has an inclination of 0° (perpendicular to the galactic plane), and the winds have inclinations of 0°, 45°, and 90°. We analyze the impact on the host’s gas, star formation, and circumgalactic medium. We find that jet feedback is energy-driven and wind feedback is momentum-driven. In all the simulations, the jet or wind creates a cavity mostly devoid of dense gas in the nuclear region where star formation is then quenched, but we find strong positive feedback in all the simulations at radii greater than 3 kpc. All four simulations have similar SFRs and stellar velocities with large radial and vertical components. However, the wind at an inclination of 90° creates the highest density regions through ram pressure and generates the highest rates of star formation due to its ongoing strong interaction with the dense gas of the galactic plane. With increased wind inclination, we find greater asymmetry in gas distribution and resulting star formation. Our model generates an expanding ring of triggered star formation with typical velocities of the order of 1/3 of the circular velocity, superimposed on the older stellar population. This should result in a potentially detectable blue asymmetry in stellar absorption features at kiloparsec scales.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

A novel metal-organic framework for high storage and separation of acetylene at room temperature

A novel 3D microporous metal-organic framework with NbO topology, [Cu{sub 2}(L)(H{sub 2}O){sub 2}]∙(DMF){sub 6}·(H{sub 2}O){sub 2} (ZJU-10, ZJU = Zhejiang University; H{sub 4}L =2′-hydroxy-[1,1′:4′,1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid; DMF =N,N-dimethylformamide), has been synthesized and structurally characterized. With suitable pore sizes and open Cu{sup 2+} sites, ZJU-10a exhibits high BET surface area of 2392 m{sup 2}/g, as well as moderately high C{sub 2}H{sub 2} volumetric uptake capacity of 132 cm{sup 3}/cm{sup 3}. Meanwhile, ZJU-10a is a promising porous material for separation of acetylene from methane and carbon dioxide gas mixtures at room temperature. - Graphical abstract: A new NbO-type microporous metal-organic framework ZJU-10 with suitable pore size and open Cu{sup 2+} sites was synthesized to realize the strong interaction with acetylene molecules, which can separate the acetylene from methane and carbon dioxane gas mixtures at room temperature. Display Omitted - Highlights: • A novel 3D NbO-type microporous metal-organic framework ZJU-10 was solvothermally synthesized and structurally characterized. • ZJU-10a exhibits high BET surface area of 2392 m{sup 2}/g. • ZJU-10a shows a moderately high C{sub 2}H{sub 2} gravimetric (volumetric) uptake capacity of 174 (132) cm{sup 3}/g at 298 K and 1 bar. • ZJU-10a can separate acetylene from methane and carbon dioxide gas mixtures at room temperature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Electrochemical recovery of Nd using liquid metals (Bi and Sn) in LiCl-KCl-NdCl 3

Highly efficient recovery of Nd into liquid metals of Bi and Sn was achieved in molten LiCl-KCl-NdCl 3 electrolyte at 773–973 K by leveraging the strong interactions of Nd with liquid metals. Based on the emf measurements of Nd-Sn and Nd-Bi alloys, the activity values of Nd were determined as low as 1.1–5.8×10 –13 in both liquid metals at 973 K while the solubility of Nd was found to be 1.46 mol% in Sn and 5.65 mol% in Bi. Both liquid metals demonstrated high round-trip coulombic efficiencies (>99.3%) during deposition-removal cycles of 10–50 mA cm –2 and high recovery capacity up to approximately 20 mol% Nd beyond the solubility limit. In addition, a high Nd recovery yield (84–90%) with respect to the applied charge was confirmed based on chemical analysis of electrolysis products in Bi after constant current electrolysis (–50 mA cm –2 ) at 873–973 K. Overpotentials during the Nd deposition process were attributed to charge-transfer and mass-transport resistances based on the current-potential curve and electrochemical impedance spectroscopy. The charge-transfer kinetics of Nd deposition into liquid metals was facile with high exchange current densities at ~220 mA cm –2 . Finally, the exceptionally high recovery efficiency for Nd in the molten chloride is thought to result from strong chemical interactions (i.e., low activity) of Nd in liquid metals that encourage one-step reduction, i.e., Nd 3+ + 3e → Nd(in Bi or Sn) by effectively suppressing side reaction pathways from multivalent states (Nd 2+ and Nd 3+ ).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Experimental Determination of the QCD Effective Charge α g1 ( Q )

The QCD effective charge α g1 (Q) is an observable that characterizes the magnitude of the strong interaction. At high momentum Q, it coincides with the QCD running coupling α s (Q). At low Q, it offers a nonperturbative definition of the running coupling. We have extracted α g1 (Q) from measurements carried out at Jefferson Lab that span the very low to moderately high Q domain, 0.14 ≤ Q ≤ 2.18 GeV. The precision of the new results is much improved over the previous extractions and the reach in Q at the lower end is significantly expanded. The data show that α g1 (Q) becomes Q-independent at very low Q. They compare well with two recent predictions of the QCD effective charge based on Dyson–Schwinger equations and on the AdS/CFT duality.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Updates on the Studies of $${\varvec{N}}^\mathbf{*}$$ N * Structure with CLAS and the Prospects with CLAS12

Here, the recent results on $\gamma_vpN^*$ electrocouplings from analyses of the data on exclusive meson electroproduction off protons measured with the CLAS detector at Jefferson Lab are presented. The impact of these results on the exploration of the excited nucleon state structure and non-perturbative strong interaction dynamics behind its formation is outlined. The future extension of these studies in the experiments with the CLAS12 detector in the upgraded Hall-B at JLab will provide for the first time $\gamma_vpN^*$ electrocouplings of all prominent resonances at the still unexplored distance scales that correspond to extremely low (0.05~GeV$^2 < Q^2 <$ 0.5~GeV$^2$) and the highest photon virtualities (5.0~GeV$^2 < Q^2 <$ 12.0~GeV$^2$) ever achieved in the exclusive electroproduction measurements. The expected results will address the most important open problems of the Standard Model: on the nature of more than 98\% of hadron mass, quark-gluon confinement and emergence of the excited nucleon state structure from the QCD Lagrangian, as well as allowing a search for the new states of hadron matter predicted from the first principles of QCD, the so-called hybrid baryons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

SO(3) “Nuclear Physics” with ultracold Gases☆

An ab initio calculation of nuclear physics from Quantum Chromodynamics (QCD), the fundamental SU(3) gauge theory of the strong interaction, remains an outstanding challenge. Here, we discuss the emergence of key elements of nuclear physics using an SO(3) lattice gauge theory as a toy model for QCD. We show that this model is accessible to state-of-the-art quantum simulation experiments with ultracold atoms in an optical lattice. First, we demonstrate that our model shares characteristic many-body features with QCD, such as the spontaneous breakdown of chiral symmetry, its restoration at finite baryon density, as well as the existence of few-body bound states. Then we show that in the one-dimensional case, the dynamics in the gauge invariant sector can be encoded as a spin S=(3/2) Heisenberg model, i.e., as quantum magnetism, which has a natural realization with bosonic mixtures in optical lattices, and thus sheds light on the connection between non-Abelian gauge theories and quantum magnetism.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Large-momentum effective theory

Since the parton model was introduced by Feynman more than 50 years ago, much has been learned about the partonic structure of the proton through a large body of high-energy experimental data and dedicated global fits. However, limited progress has been made in calculating partonic observables such as the parton distribution function (PDFs) from the fundamental theory of strong interactions, quantum chromodynamics (QCD). Recently some advocated for a formalism, large-momentum effective theory (LaMET), through which one can extract parton physics from the properties of the proton traveling at a moderate boost factor such as γ ~ 2 – 5 . The key observation behind this approach is that Lorentz symmetry allows the standard formalism of partons in terms of light-front operators to be replaced by an equivalent one with large-momentum states and time-independent operators of a universality class. With LaMET, the PDFs, generalized PDFs or generalized parton distributions, transverse-momentum-dependent PDFs, and light-front wave functions can all be extracted in principle from lattice simulations of QCD (or other nonperturbative methods) through standard effective field theory matching and running. Future lattice QCD calculations with exascale computational facilities could help one to understand the experimental data related to the hadronic structure, including those from the upcoming electron-ion colliders dedicated to exploring the partonic landscape of the proton. In this work, the progress made in the past few years in the development of the LaMET formalism and its applications is reviewed, with an emphasis on a demonstration of its effectiveness from initial lattice QCD simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Insights into the emergence of mass from studies of pion and kaon structure

There are two mass generating mechanisms in the standard model of particle physics (SM). One is related to the Higgs boson and fairly well understood. The other is embedded in quantum chromodynamics (QCD), the SM’s strong interaction piece; and although responsible for emergence of the roughly 1 GeV mass scale that characterises the proton and hence all observable matter, the source and impacts of this emergent hadronic mass (EHM) remain puzzling. As bound states seeded by a valence-quark and -antiquark, pseudoscalar mesons present a simpler problem in quantum field theory than that associated with the nucleon. Consequently, there is a large array of robust predictions for pion and kaon properties whose empirical validation will provide a clear window onto many effects of both mass generating mechanisms and the constructive interference between them. This has now become significant because new-era experimental facilities, in operation, construction, or planning, are capable of conducting such tests and thereby contributing greatly to resolving the puzzles of EHM. These aspects of experiment, phenomenology, and theory, along with contemporary successes and challenges, are reviewed herein. In addition to providing an overview of the experimental status, we focus on recent progress made using continuum Schwinger function methods and lattice-regularised QCD. Further, advances made using other theoretical tools are also sketched. Our primary goal is to highlight the potential gains that can accrue from a coherent effort aimed at finally reaching an understanding of the character and structure of Nature’s Nambu–Goldstone modes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗