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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Multipolar Raman Scattering vs Interfacial Nanochemistry: Case of 4-Mercaptopyridine on Gold

Caution needs to be exercised in associating changes in plasmon-enhanced Raman spectra with chemical transformations. This is demonstrated through a detailed analysis of tip-enhanced Raman (TER) scattering from 4-mercaptopyridine (MPY) on gold. The substrate used consists of gold nanoplates atop a gold surface featuring heterogeneous grooves, all coated with a monolayer of MPY. The brightest spectra across the substrate exhibit features that can only be recovered by considering the generalized polarizability of oriented MPY molecules. Finally, the complex TER spectra we observe do not mark interfacial chemistry, but rather, multipolar TER scattering driven by local field gradients.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Multipolar Fermi Surface Deformations in Sr 2 ⁢RuO 4 Probed by Resistivity and Sound Attenuation: A Window into Electron Viscosity and the Collision Operator

Recent developments in electron hydrodynamics have demonstrated the importance of considering the full structure of the electron-electron scattering operator, which encodes a sequence of lifetimes, one for each component of the Fermi surface deformation in a multipolar expansion. In this context, the dipolar lifetime is measured by resistivity, whereas the quadrupolar component probes the viscosity and can be measured in the bulk via sound attenuation. We introduce a framework to extract the collision operator of an arbitrary metal by combining resistivity and sound attenuation measurements with a realistic calculation of the scattering operator that includes multiband and umklapp effects. The collision operator allows for the prediction of a plethora of properties, including the nonlocal conductivity, and can be used to predict hydrodynamic behavior for bulk metals. As a first application, we apply this framework to Sr 2 ⁢RuO 4 in a temperature range where electron-electron scattering is dominant. Furthermore, we find quantitative agreement between our model and the temperature dependence of both the resistivity and the sound attenuation, we find the quadrupolar (𝐵 1⁢𝑔 ) relaxation rate to be 30% higher than the dipolar one due to the presence of hot spots on the 𝛾 band, and we predict a strongly anisotropic viscosity arising from the 𝛼 and 𝛽 bands.

Boltzmann theory↗
DOE OSTI2016

Configuration analysis and optimization on multipolar Galatea trap

Multipolar Galatea magnetic trap simulation model was established with the finite element simulation software COMSOL Multiphysics. Analyses about the magnetic section configuration show that better magnetic configuration should make more plasma stay in the weak magnetic field rather than the annular magnetic shell field. Then an optimization model was established with axial electromagnetic force, weak magnetic field area and average magnetic mirror ratio as the optimization goals and with the currents of myxines as design variables. Select appropriate weight coefficients and get optimization results by applying genetic algorithm. Results show that the superiority of the target value of typical application parameters, including the average magnetic mirror can reduce more than 5%, the weak magnetic field area can increase at least 65%, at the same time, axial electromagnetic force acting on the outer myxines can be reduced to less than 50 N. Finally, the results were proved by COMSOL Multiphysics and the results proved the optimized magnetic trap configuration with more plasma in the weak magnetic field can reduce the plasma diffusion velocity and is more conducive for the constraint of plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

THE SHAPING OF THE MULTIPOLAR PRE-PLANETARY NEBULA CRL 618 BY MULTIDIRECTIONAL BULLETS

In order to understand the formation of the multipolar structures of the pre-planetary nebula CRL 618, we perform 3D simulations using a multidirectional bullet model. The optical lobes of CRL 618 and fast molecular outflows at the tips of the lobes have been found to have similar expansion ages of ∼100 yr. Additional fast molecular outflows were found near the source along the outflow axes with ages of ∼45 yr, suggesting a second episode of bullet ejections. Thus, in our simulations, two episodes of bullet ejections are assumed. The shaping process is simulated using the ZEUS-3D hydrodynamics code that includes molecular and atomic cooling. In addition, molecular chemistry is also included to calculate the CO intensity maps. Our results show the following: (1) Multiepoch bullets interacting with the toroidal dense core can produce the collimated multiple lobes as seen in CRL 618. The total mass of the bullets is ∼0.034 M{sub ⊙}, consistent with the observed high-velocity (HV) CO emission in fast molecular outflows. (2) The simulated CO J = 3–2 intensity maps show that the low-velocity cavity wall and the HV outflows along the lobes are reasonably consistent with the observations. The position–velocity diagram of the outflows along the outflow axes shows a linear increase of velocity with distance, similar to the observations. The ejections of these bullets could be due to magnetorotational explosions or nova-like explosions around a binary companion.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Search for multipolar instability in URu 2 Si 2 studied by ultrasonic measurements under pulsed magnetic field

In this study, the elastic properties of URu 2 Si 2 in the high magnetic field region above 40 T, over a wide temperature range from 1.5 to 120 K, were systematically investigated by means of high-frequency ultrasonic measurements. The investigation was performed at high magnetic fields to better investigate the innate bare 5f-electron properties, since the unidentified electronic thermodynamic phase of unknown origin, the so-called “hidden order” (HO), and associated hybridization of conduction and f-electrons (c-f hybridization) are suppressed at high magnetic fields. From the three different transverse modes we find contrasting results; both the Γ 4 (B 2g ) and Γ 5 (E g ) symmetry modes C 66 and C 44 show elastic softening that is enhanced above 30 T, while the characteristic softening of the Γ 3 (B 1g ) symmetry mode (C 11 – C 12 )/2 is suppressed in high magnetic fields. These results underscore the presence of a hybridization-driven Γ 3 (B 1g ) lattice instability in URu 2 Si 2 . However, the results from this work cannot be explained by using existing crystalline electric field schemes applied to the quadrupolar susceptibility in a local 5f 2 configuration. Instead, we present an analysis based on a band Jahn-Teller effect.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Noncollinear Magnetic Structure and Multipolar Order in Eu 2 Ir 2 O 7

The magnetic properties of the pyrochlore iridate material Eu 2 Ir 2 O 7 (5d 5 ) have been studied based on first principles calculations, where the crystal field splitting Δ , spin-orbit coupling (SOC) λ, and Coulomb interaction U within Ir 5 d orbitals all play significant roles. The ground state phase diagram has been obtained with respect to the strength of SOC and Coulomb interaction U , where a stable antiferromagnetic ground state with all-in–all-out (AIAO) spin structure has been found. In addition, another antiferromagnetic state with energy close to AIAO has also been found to be stable. The calculated nonlinear magnetization of the two stable states both have the d -wave pattern but with a π/4 phase difference, which can perfectly explain the experimentally observed nonlinear magnetization pattern. Finally, compared with the results of the nondistorted structure, it turns out that the trigonal lattice distortion is crucial for stabilizing the AIAO state in Eu 2 Ir 2 O 7 . Furthermore, besides large dipolar moments, we also find considerable octupolar moments in the magnetic states.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Dielectric Spectroscopy on Thermally Aged, Intact Poly-vinyl Chloride/Ethylene Propylene Rubber (PVC/EPR) Multipolar Cables

As a contribution to condition monitoring diagnostics on low voltage cables used in nuclear power plants, this work shows that broadband dielectric spectroscopy can be an effective technique to assess aging state of these cables. Broadband dielectric spectroscopy has been performed on three-conductor (tri-core) cables, insulated by EPR with PVC jacket. The main challenge has been to perform the measurement on the intact cables, by means of a custom-built connector, conceiving a non-destructive and non-intrusive technique. Results show that capacitance and dissipation factor can provide information about the aging state of the cable, without the need to destroy the sample in the measurement process.

dielectric spectroscopy, nondestructive evaluation↗
DOE OSTI2021

The Multipolar Magnetic Field of the Millisecond Pulsar PSR J0030+0451

Modeling of the NICER X-ray waveform of the pulsar PSR J0030+0451, aimed at constraining the neutron star mass and radius, has inferred surface hot spots (the magnetic polar caps) that imply significantly nondipolar magnetic fields. To this end, we investigate magnetic field configurations that comprise offset dipole-plus-quadrupole components using a static vacuum field and force-free global magnetosphere models. Taking into account the compactness and observer angle values provided by Miller et al. and Riley et al., we compute geodesics from the observer plane to the polar caps to compute the resulting X-ray light curve. We explore, through Markov Chain Monte Carlo techniques, the detailed magnetic field configurations that can reproduce the observed X-ray light curve and have discovered degeneracies, i.e., diverse field configurations, which can provide sufficient descriptions of the NICER X-ray waveforms. Having obtained the force-free field structures, we then compute the corresponding synchronous γ-ray light curves following Kalapotharakos et al.; these we compare to those obtained by Fermi-LAT, to provide models consistent with both the X-ray and the γ-ray data, thereby restricting further the multipole field parameters. An essential aspect of this approach is the proper computation of the relative phase between the synchronous X- and γ-ray light curves. We conclude with a discussion of the broader implications of our study.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Nuclear Data Sheets for A=218

The evaluated data are presented for 11 known A=218 nulcides (Pb, Bi, Po, At, Rn, Fr, Ra, Ac, Th, Pa and U). For {sup 218}Pb, {sup 218}Bi, {sup 218}At and {sup 218}Pa, data are available only for the ground states. For {sup 218}U, only the g.s. and a high-spin isomer are known, with no data on γ-ray transitions available. For {sup 218}Po, ten excited states are known from {sup 218}Bi decay, with no knowledge on the multipolarities of gamma-ray transitions. For {sup 218}Th, five excited states in the g.s. band are known from an in-beam γ-ray study. Data on level half-lives, multipolarities and mixing ratios of gamma transitions is generally lacking for A=218 nuclei. The static magnetic dipole moment has been measured for only an isomer in {sup 218}Fr. With the exception of a new nuclide, {sup 218}Pb, and measurements of half-lives of ground states of a few nuclides of A=218 and A=222, no substantial structure information has become available since the previous evaluation in 2006. Q values are adopted from 2017Wa10 (AME-2016). The present evaluation supersedes the previous A=218 ENSDF evaluations, 2006Ja03, 1995El08, 1987El12 and 1977To13. This evaluation was carried out as part of a joint IAEA-ICTP workshop for Nuclear Structure and Decay Data, organized and hosted by the IAEA, Vienna, and ICTP, Trieste, October 15–26, 2018.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Theory of electric, magnetic, and toroidal polarizations in crystalline solids with applications to hexagonal lonsdaleite and cubic diamond

Multipolar order in bulk crystalline solids is characterized by multipole densities-denoted as polarizations in this work-that cannot be cleanly defined using the concepts of classical electromagnetism. Here we use group theory to overcome this difficulty and present a systematic study of electric, magnetic, and toroidal multipolar order in crystalline solids. Based on our symmetry analysis, we identify five categories of polarized matter, each of which is characterized by distinct features in the electronic band structure. For example, Rashba spin splitting in electropolar bulk materials like wurtzite represents the electric dipolarization in these materials. We also develop a general formalism of indicators for individual multipole densities that provide a physical interpretation and quantification of multipolar order. Our work clarifies the relation between patterns of localized multipoles and macroscopic multipole densities they give rise to. To illustrate the general theory, we discuss its application to polarized variants of hexagonal lonsdaleite and cubic diamond structures. In conclusion, our work provides a general framework for classifying and expanding current understanding of multipolar order in complex materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Beyond the electric-dipole approximation in simulations of x-ray absorption spectroscopy: Lessons from relativistic theory

Herein we present three schemes to go beyond the electric-dipole approximation in x-ray absorption spectroscopy calculations within a four-component relativistic framework. The first is based on the full semi-classical light–matter interaction operator and the two others on a truncated interaction within the Coulomb gauge (velocity representation) and multipolar gauge (length representation). We generalize the derivation of the multipolar gauge to an arbitrary expansion point and show that the potentials corresponding to different expansion points are related by a gauge transformation, provided that the expansion is not truncated. This suggests that the observed gauge-origin dependence in the multipolar gauge is more than just a finite-basis set effect. The simplicity of the relativistic formalism enables arbitrary-order implementations of the truncated interactions, with and without rotational averaging, allowing us to test their convergence behavior numerically by comparison to the full formulation. We confirm the observation that the oscillator strength of the electric-dipole allowed ligand K -edge transition of TiCl 4 , when calculated to the second order in the wave vector, becomes negative but also show that inclusion of higher-order contributions allows convergence to the result obtained using the full light–matter interaction. However, at higher energies, the slow convergence of such expansions becomes dramatic and renders such approaches at best impractical. When going beyond the electric-dipole approximation, we therefore recommend the use of the full light–matter interaction.

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

Spontaneous breaking of multipole symmetries

Multipole symmetries are of interest both as a window on fracton physics and as a crucial ingredient in realizing new universality classes for quantum dynamics. Here we address the question of whether and when multipole symmetries can be spontaneously broken, both in thermal equilibrium and at zero temperature. In this work, we derive generalized Mermin-Wagner arguments for the total or partial breaking of multipolar symmetry groups and generalized Imry-Ma arguments for the robustness of such multipolar symmetry breaking to disorder. We present both general results and explicit examples. Our results should be directly applicable to quantum dynamics with multipolar symmetries and also provide a useful stepping stone to understanding the robustness of fracton phases to thermal fluctuations, quantum fluctuations, and disorder.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Microscopic origin of reflection-asymmetric nuclear shapes

The presence of nuclear ground states with stable reflection-asymmetric shapes is supported by rich experimental evidence. Theoretical surveys of odd-multipolarity deformations predict the existence of pear-shaped isotopes in several fairly localized regions of the nuclear landscape in the vicinity of near-lying single-particle shells with Δℓ = Δj = 3. We analyze the role of isoscalar, isovector, neutron-proton, neutron-neutron, and proton-proton multipole interaction energies in inducing the onset of reflection-asymmetric ground-state deformations. The calculations are performed in the framework of axial reflection-asymmetric Hartree-Fock-Bogoliubov theory using two Skyrme energy-density functionals and density-dependent pairing force. We show that reflection-asymmetric ground-state shapes of atomic nuclei are driven by the odd-multipolarity neutron-proton (or isoscalar) part of the nuclear interaction energy. This result is consistent with the particle-vibration picture, in which the main driver of octupole instability is the isoscalar octupole-octupole interaction giving rise to large E3 polarizability. The necessary condition for the appearance of localized regions of pear-shaped nuclei in the nuclear landscape is the presence of parity doublets involving Δℓ = Δj = 3 proton or neutron single-particle shells. This condition alone is, however, not sufficient to determine whether pear shapes actually appear, and, if so, what the corresponding reflection-asymmetric deformation energies are. The predicted small reflection-asymmetric deformation energies result from dramatic cancellations between even- and odd-multipolarity components of the nuclear binding energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗