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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Iron Charge Distribution as an Identifier of Interplanetary Coronal Mass Ejections

We present solar wind Fe charge state data measured on the Advanced Composition Explorer (ACE) from early 1998 to the middle of 2000. Average Fe charge states in the solar wind are typically around 9 to 11. However, deviations from these average charge states occur, including intervals with a large fraction of Fe(sup greater or = 16+) which are consistently associated with interplanetary coronal mass ejections (ICMEs). By studying the Fe charge state distribution we are able to extract coronal electron temperatures often exceeding 2 x 10(exp 6) kelvins. We also discuss the temporal trends of these events, indicating the more frequent appearance of periods with high Fe charge states as solar activity increases.

Lepri, S. T.↗
DOE OSTI2020

Calculating and Characterizing the Charge Distributions in Solids

Accurate estimation of the partial atomic charges on metal centers is useful for understanding electronic and catalytic properties of materials. However, different methods of calculating these charges may give quite different results; this issue has been more widely studied for molecules than for solids. Here we study the charges on the metal centers of a test set of 18 solids containing transition metals by using density functional theory with several density functionals (PBE, PBE+U, TPSS, revTPSS, HLE17, revM06-L, B3LYP, B3LYP*, and other exchange-modified B3LYP functionals) and four charge models (Bader, Hirshfeld, CM5, and DDEC6). The test set contains 12 systems with nonmagnetic metal centers (eight metal oxides (MO 2 ), two metal sulfides (MS 2 ), and two metal selenides (MSe 2 )) and six ferromagnetic transition metal complexes. Our study shows that, among the four types of charges, Bader charges are the highest and Hirshfeld charges are the lowest for all the systems, regardless of the functional being used. The CM5 charges are bigger than DDEC6 charges for MX 2 with M = Ti or Mo and X = S or Se, but for the other 14 cases they are lower. We found that the most of the systems are sensitive to the Hubbard U parameters in PBE+U and to the percentage X of Hartree–Fock exchange in exchange-modified B3LYP; as we increase U or X, the charges on the metal atoms in MX 2 increase steadily. Testing different density functionals shows charges calculated with higher Hubbard U parameters in PBE+U are comparable to B3LYP (with 20% Hartree–Fock exchange). Among four meta-GGA functionals studied, the charges with HLE17 have the closest agreement with B3LYP. In conclusion, the variation of charges with choice of charge model is greater than the variation with choice of density functional.

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

Direct observation of elemental fluctuation and oxygen octahedral distortion-dependent charge distribution in high entropy oxides

The enhanced compositional flexibility to incorporate multiple-principal cations in high entropy oxides (HEOs) offers the opportunity to expand boundaries for accessible compositions and unconventional properties in oxides. Attractive functionalities have been reported in some bulk HEOs, which are attributed to the long-range compositional homogeneity, lattice distortion, and local chemical bonding characteristics in materials. However, the intricate details of local composition fluctuation, metal-oxygen bond distortion and covalency are difficult to visualize experimentally, especially on the atomic scale. Here, we study the atomic structure-chemical bonding-property correlations in a series of perovskite-HEOs utilizing the recently developed four-dimensional scanning transmission electron microscopy techniques which enables to determine the structure, chemical bonding, electric field, and charge density on the atomic scale. The existence of compositional fluctuations along with significant composition-dependent distortion of metal-oxygen bonds is observed. Consequently, distinct variations of metal-oxygen bonding covalency are shown by the real-space charge-density distribution maps with sub-ångström resolution. The observed atomic features not only provide a realistic picture of the local physico-chemistry of chemically complex HEOs but can also be directly correlated to their distinctive magneto-electronic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Unusual Layer-Dependent Charge Distribution, Collective Mode Coupling, and Superconductivity in Multilayer Cuprate Ba2Ca3Cu4O8F2

Low energy ultrahigh momentum resolution angle resolved photoemission spectroscopy study on four-layer self-doped high T{sub c} superconductor Ba{sub 2}Ca{sub 3}Cu{sub 4}O{sub 8}F{sub 2} (F0234) revealed fine structure in the band dispersion, identifying the unconventional association of hole and electron doping with the inner and outer CuO{sub 2} layers, respectively. For the states originating from two inequivalent CuO{sub 2} layers, different energy scales are observed in dispersion kinks associated with the collective mode coupling, with the larger energy scale found in the electron (n-) doped state which also has stronger coupling strength. Given the earlier finding that the superconducting gap is substantially larger along the n-type Fermi surface, our observations connect the mode coupling energy and strength with magnitude of the pairing gap.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1978

The nuclear and ionic charge distribution particle experiments on the ISEE-1 and ISEE-C spacecraft

The ISEE-1 and ISEE-C instruments are designed to measure the elemental abundances, charge state composition, energy spectra, and angular distributions of energetic ions in the energy range 2 keV/charge to 80 MeV/nucleon and electrons between 75 and 1300 keV. The instrument consists of three sensor systems: (1) ULECA which is an electrostatic deflection system with rectangular solid-state detectors for the 3-560 keV/charge range; (2) ULEWATT which is a double dE/dX vs E thin-window flowthrough proportional counter/solid-state detector telescope for the 0.2-80 MeV/nucleon (Fe) range; and (3) ULEZEQ which is a combination of an electrostatic deflection analyzer and a thin-window dE/dX vs E system with thin-window proportional counter and position-sensitive solid-state detector. The applications of the instruments to solar and interplanetary phenomena and to magnetospheric acceleration and trapped particles are discussed.

Hovestadt, D.↗
NASA NTRS1992

Determination and representation of electric charge distributions associated with adverse weather conditions

Algorithms are presented for determining the size and location of electric charges which model storm systems and lightning strikes. The analysis utilizes readings from a grid of ground level field mills and geometric constraints on parameters to arrive at a representative set of charges. This set is used to generate three dimensional graphical depictions of the set as well as contour maps of the ground level electrical environment over the grid. The composite, analytic and graphic package is demonstrated and evaluated using controlled input data and archived data from a storm system. The results demonstrate the packages utility as: an operational tool in appraising adverse weather conditions; a research tool in studies of topics such as storm structure, storm dynamics, and lightning; and a tool in designing and evaluating grid systems.

Rompala, John T.↗
NASA NTRS1983

Energy and charge distribution of energetic helium ions in the outer radiation belt of the earth

The first direct measurement of the charge states of helium at energies greater than 0.5 MeV/nucleon in the outer radiation belt, obtained aboard the ISEE-1 spacecraft in 1977, is reported. High abundances of singly ionized helium, with He(+)/He(2+) = 0.4 + or - 0.1 at L = 3.3 was found during one perigee pass, with a sudden decrease of that ratio by a factor of about 10 between L = 3.3 and 3.7. It is shown that nonstationary and/or nonadiabatic processes may play an important role for the distribution of helium ions in the outer radiation belt.

Klecker, B.↗
DOE OSTI2018

Effects of nonequilibrated topological charge distributions on pseudoscalar meson masses and decay constants

We study the effects of failure to equilibrate the squared topological charge Q 2 on lattice calculations of pseudoscalar masses and decay constants. The analysis is based on chiral perturbation theory calculations of the dependence of these quantities on the QCD vacuum angle θ. For the light-light partially quenched case, we rederive the known chiral perturbation theory results of Aoki and Fukaya, but using the nonperturbatively valid chiral theory worked out by Golterman, Sharpe and Singleton, and by Sharpe and Shoresh. We then extend these calculations to heavy-light mesons. Results when staggered taste violations are important are also presented. The derived Q 2 dependence is compared to that of simulations using the MILC Collaboration’s ensembles of lattices with four flavors of dynamical highly improved staggered quarks. We find agreement, albeit with large statistical errors. These results can be used to correct for the leading effects of unequilibrated Q 2 , or to make estimates of the systematic error coming from the failure to equilibrate Q 2 . In an appendix, we show that the partially quenched chiral theory may be extended beyond a lower bound on valence masses discovered by Sharpe and Shoresh. Subtleties occurring when a sea-quark mass vanishes are discussed in another appendix.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Space charge distributions in insulating polymers: A new non-contacting way of measurement

A new technique for the determination of space charge profiles in insulating polymers is proposed. Based on the evolution of an existing thermal wave technique called Focused Laser Intensity Modulation Method ((F)LIMM), it allows non-contact measurements on thin films exhibiting an internal charge to be studied. An electrostatic model taking into account the new sample-cell geometry proposed was first developed. It has been shown, in particular, that it was theoretically possible to calculate the internal charge from experimental measurements while allowing an evaluation of the air layer appearing between the sample and the electrode when non-contact measurements are performed. These predictions were confirmed by an experimental implementation for two thin polymer samples (25 μm-polyvinylidenefluoride and 50 μm-polytetrafluoroethylene (PTFE)) used as tests. In these cases, minimum air-layer thickness was determined with an accuracy of 3% and 20%, respectively, depending on the signal-to-noise ratio during the experimental procedure. In order to illustrate the reachable possibilities of this technique, 2D and 3D cartographies of a negative space charge implanted by electron beam within the PTFE test sample were depicted: like in conventional (F)LIMM, a multidimensional representation of a selectively implanted charge remains possible at a few microns depth, but using a non-contacting way of measurement.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Probing Heterogeneous Charge Distributions at the α-Al 2 O 3 (0001)/H 2 O Interface

Unlike metal or semiconductor electrodes, the surface charge resulting from the protonation or deprotonation of insulating mineral oxides is highly localized and heterogeneous in nature. In this work the Stark active C≡N stretch of potassium thiocyanate is used as a molecular probe of the heterogeneity of the interfacial electrostatic potential at the α-Al 2 O 3 (0001)/H 2 O interface. Vibrational sum frequency generation (vSFG) measurements performed in the OH stretching region suggest that thiocyanate species organize interfacial water similarly to halide ions. Changes in the electrostatic potential are then tracked via Stark shifts of the vibrational frequency of the thiocyanate stretch. Our vSFG measurements show that we can simultaneously measure the vSFG response of SCN – ions experiencing charged and neutral surface sites. We assign local potentials of +308 and -154 mV to positively and negatively charged aluminol groups that are present at pH = 4 and pH = 10, respectively. Thiocyanate anions at positively charged surface sites and negatively charged surface sites and those participating in contact ion pairing adopt similar orientations and are oppositely oriented relative to thiocyanate ions near neutral surface sites. All four species followed Langmuir adsorption isotherms. Density functional theory–molecular dynamics (DFT-MD) simulations of SCN – near the neutral α-Al 2 O 3 (0001)/H 2 O interface show that the vSFG response in the C≡N stretch region originates from a SCN–H–O–Al complex, suggesting the surface site specificity of these experiments. To our knowledge this is the first spectroscopic measurement of local potentials associated with a heterogeneously charged surface. The ability to probe the evolution of local charges in situ could provide vital insight into many industrial, electrochemical, and geochemically relevant interfaces.

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

Measurements of higher-order cumulants of multiplicity and net-electric charge distributions in inelastic proton-proton interactions by NA61/SHINE

This paper presents the energy dependence of multiplicity and net-electric charge fluctuations in p+p interactions at beam momenta 20, 31, 40, 80, and 158 \(\text{ Ge }\hspace{-1.00006pt}\text{ V }\!/\!c\). Results are corrected for the experimental biases and quantified with the use of cumulants and factorial cumulants. Cumulant ratios are an essential tool in the search for the critical point of strongly interacting matter in heavy ion collisions. Measurements performed in p+p interactions provide a vital baseline estimation in these studies. The measured signals are compared with the string hadronic models Epos1.99 and FTFP-BERT.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

A Method to Extract the Charge Distribution Arriving at the TPC Wire Planes in MicroBooNE

In this technote, we describe the concept and general strategy of LArTPC drifted-charge extraction, which converts the raw digitized TPC waveform to the number of ionized electrons passing through the wire plane at a given time. The proper recovery of the number of ionized electrons from all wire planes is important to the success of the subsequent reconstruction algorithms. A number of building blocks for the processing algorithm are described and characterized. An example of implementation of the algorithm was realized inside the Wire-Cell reconstruction package. The performance was qualitatively illustrated on MicroBooNE data with event display pictures, which shows significant improvements. Some metrics to evaluate the performance of the TPC signal extraction procedure are described. Next steps towards the quantification of the effect of the proposed concept and optimization of the procedure are outlined.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Simultaneous Control of Pore‐Space Partition and Charge Distribution in Multi‐Modular Metal–Organic Frameworks

Abstract We report here a strategy for making anionic pacs type porous materials by combining pore space partition with charge reallocation. The method uses the first negatively charged pore partition ligand (2,5,8‐tri‐(4‐pyridyl)‐1,3,4,6,7,9‐hexaazaphenalene, H‐tph) that simultaneously enables pore partition and charge reallocation. Over two dozen anionic pacs materials have been made to demonstrate their excellent chemical stability and a high degree of tunability. Notably, Ni 3 ‐bdt‐tph (bdt=1,4‐benzeneditetrazolate) exhibits month‐long water stability, while CoV‐bdt‐tph sets a new benchmark for C 2 H 2 storage capacity under ambient conditions for ionic MOFs. In addition to tunable in‐framework modules, we show feasibility to tune the type and concentration of extra‐framework counter cations and their influence on both stability and capability to separate industrial C 3 H 8 /C 3 H 6 and C 6 H 6 /C 6 H 12 mixtures.

Hong, Anh N.↗
DOE OSTI2022

Simultaneous Control of Pore-Space Partition and Charge Distribution in Multi-Modular Metal–Organic Frameworks

Here we report here a strategy for making anionic pacs type porous materials by combining pore space partition with charge reallocation. The method uses the first negatively charged pore partition ligand (2,5,8-tri-(4-pyridyl)-1,3,4,6,7,9-hexaazaphenalene, H-tph) that simultaneously enables pore partition and charge reallocation. Over two dozen anionic pacs materials have been made to demonstrate their excellent chemical stability and a high degree of tunability. Notably, Ni 3 -bdt-tph (bdt=1,4-benzeneditetrazolate) exhibits month-long water stability, while CoV-bdt-tph sets a new benchmark for C 2 H 2 storage capacity under ambient conditions for ionic MOFs. In addition to tunable in-framework modules, we show feasibility to tune the type and concentration of extra-framework counter cations and their influence on both stability and capability to separate industrial C 3 H 8 /C 3 H 6 and C 6 H 6 /C 6 H 12 mixtures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

The charge distribution of heavy cosmic ray nuclei

In the analysis of data from a balloon flight of a detector of cosmic ray nuclei designed to study the isotopic composition, the charge composition has been measured with high resolution. Some 24,000 nuclei with Z not less than 10 have been measured with a charge resolution of 0.2 charge units. The limitations on the significance of these results are those due to the corrections for the effects of matter in the detectors and the residual atmospheric matter. These corrections are discussed and corrected results are compared with other high resolution charge spectra reported recently.

Freier, P. S.↗
NASA NTRS1982

A thundercloud electric field sounding - Charge distribution and lightning

An instrumented free balloon measured electric fields and field changes as it rose through a thundercloud above Langmuir Laboratory, New Mexico. The variation of the electric field with altitude implied that the cloud contained negative space charge of density -0.6 to -4 nC/cu m between 5.5 and 8.0 km MSL. The environmental temperature at these levels ranged from -5 to -20 C. The measurements imply that the areal extent of this negative charge center was significantly greater than that of the cloud's intense precipitation shafts. At altitudes greater than 8 km, the instrument ascended past net positive charge. In addition, positive space charge adjacent to the earth's surface (concentration 0.6 nC/cu m and in the lowest portion of the cloud (1.0 nC/cu m) is inferred from the measurements. Electric field changes from intracloud lightning were interpreted by using a simple model for the developing streamer of the initial phase. Thunder source reconstructions provided estimates for the orientation of lightning channels. Seven 'streamers' so analyzed propagated on the average, at 50,000 m/s and carried a current of 390 A. The mean charge dissipated during a flash was 30 C.

Weber, M. E.↗