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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 NTRS1989

The determination of accurate dipole polarizabilities alpha and gamma for the noble gases

The static dipole polarizabilities alpha and gamma for the noble gases helium through xenon were determined using large flexible one-particle basis sets in conjunction with high-level treatments of electron correlation. The electron correlation methods include single and double excitation coupled-cluster theory (CCSD), an extension of CCSD that includes a perturbational estimate of connected triple excitations, CCSD(T), and second order perturbation theory (MP2). The computed alpha and gamma values are estimated to be accurate to within a few percent. Agreement with experimental data for the static hyperpolarizability gamma is good for neon and xenon, but for argon and krypton the differences are larger than the combined theoretical and experimental uncertainties. Based on our calculations, we suggest that the experimental value of gamma for argon is too low; adjusting this value would bring the experimental value of gamma for krypton into better agreement with our computed result. The MP2 values for the polarizabilities of neon, argon, krypton and zenon are in reasonabe agreement with the CCSD and CCSD(T) values, suggesting that this less expensive method may be useful in studies of polarizabilities for larger systems.

Rice, Julia E.↗
NASA NTRS1993

Solar noble gases revealed by closed system stepped etching of a metal separate from Fayetteville

Solar He, Ne, and Ar in a Fe-Ni separate from the chondrite Fayetteville are analyzed by closed system stepped oxidation. We report here data of the first 15 steps comprising 55 percent of the total solar gases. He-4/Ar-36 and Ne-20/Ar-36 are quite constant at values about 20 percent below those of present day solar wind (SWC). In this, Fe-Ni differs from lunar ilmenites where He-4/Ar-36 and Ne-20/Ar-36 in the first steps are several times below SWC. Thus, metal retains SW-noble gases even better than ilmenite, almost without element fractionation. Nevertheless, the isotopic composition of SW-He, -Ne, and -Ar in the first steps of the metal sample are identical to those found in a recently irradiated lunar ilmenite, indicating that ilmenites and chondritic metal both contain isotopically unfractionated SW noble gases. A preliminary analysis of a smaller Fayetteville metal separate shows Ne from solar energetic particles (SEP-Ne) with Ne-20/Ne-22 less than or equal to 11.5.

Murer, CH.↗
NASA NTRS1978

The origin and relative abundances of C, N and the noble gases on the terrestrial planets and in meteorites

Relative concentrations of noble gases and C and N are evaluated for the terrestrial planets. Comparisons between amounts of volatile materials in carbonaceous chondrites and on Earth and Mars are presented as support for the accretion model of planetary formation. However, attention is given to the large differences in the C/noble gas ratios on various bodies in the solar system, e.g. the Sun, Venus, Earth, Mars, stressing that the data are too incomplete to provide a reliable model for the sources of volatile and noble elements on the terrestrial planets.

Bogard, D. D.↗
NASA NTRSDate not supplied

THE DAVINCI+ MISSION TO REVEAL THE MYSTERIES OF VENUS: DEEP ATMOSPHERE VENUS INVESTIGATION OF NOBLE GASES, CHEMISTRY, AND IMAGING PLUS

The Deep Atmosphere Venus Investigation of Noble Gases, Chemistry, and Imaging Plus (DAVINCI+) mission is one of four finalists now in Phase A study as part of the ongoing Discovery Program competition [1-5]. If selected for flight, DAVINCI+ will be the first mission to Venus to incorporate flybys, a descent probe, and an orbital phase into one unified architecture – at the cost of a Discovery mission. The result will be a transformative new understanding of the atmosphere, surface, and evolutionary path of Venus as a once-habitable planet [6] (and model exoplanet) that is now host to a certainly unhabitable surface environment.

S Getty↗
NASA NTRS1982

Sorption of noble gases by solids, with reference to meteorites. I - Magnetite and carbon

The trapping of meteoritic noble gases by solids is simulated through the synthesis of 18 Fe3O4 samples at 350-720 K in a noble gas atmosphere, by means of the reactions: (1) 3Fe + 4H2O yields Fe3O4 + 4H2, using Ne, Ar, Kr and Xe; and (2) 3Fe + 4CO yields Fe3O4 + 4C + carbides, using Xe. Etching experiments suggest an analogy with 'Phase Q' in meteorites. Adsorbed atmospheric gases are present in all samples, and dominate whenever the noble gas partial pressure in the atmosphere is greater than that in the synthesis. While many of the results of Lancet and Anders (1973) appear to have been dominated by such an atmospheric component, others are suspect. When the doubtful samples of Lancet and Anders are corrected or eliminated, the fractionation pattern no longer peaks at Ar, but rather, as in the present sample, rises monotonically from Ne to Xe. No evidence is found for the earlier study's claim of a strong temperature dependence.

Yang, J.↗
NASA NTRS1983

Trapped noble gases indicate lunar origin for Antarctic meteorite

The isotopic abundances of the noble gases (He, Ne, Ar, Kr, Xe) are reported for Antarctic ALHA 81005. It contains solar wind-implanted gases whose absolute and relative concentrations are quite similar to lunar regolith samples but not to other meteorites. ALHA 81005 also contains a large excess Ar-40 component which is identical to the component in lunar fines implanted from the lunar atmosphere. Large concentrations of cosmogenic Ne-21, Kr-82, and Xe-126 in ALHA 81005 indicate a total cosmic ray exposure age of at least 200 million years. The noble gas data alone are strong evidence for a lunar origin of this meteorite.

Bogard, D. D.↗
NASA NTRS1976

Carbonaceous chondritic xenoliths and planetary-type noble gases in gas-rich meteorites

The source of the planetary-type noble gases in gas-rich meteorites is identified as finely divided (submillimeter to millimeter-sized), widely dispersed carbonaceous chondritic fragments. Trace-element abundances, noble-gas elemental abundances and isotopic abundances of xenon are compatible with the hypothesis that the carbonaceous chondritic carrier is present in amounts of a few percent in the gas-bearing portions of gas-rich chondrites and achondrites.

Wilkening, L. L.↗
NASA NTRS1973

Noble gases in eleven H-chondrites.

Review of the results of measurements of noble gases in powdered aliquots of 11 H-chondrites whose trace element contents have been previously determined by Laul et al. (1973). The measurements were made on a 4.5-inch radius, Reynolds-type mass spectrometer, using conventional techniques.

Ganapathy, R.↗
NASA NTRS1979

Thermal metamorphism of primitive meteorites. VIII - Noble gases, carbon and sulfur in Allende /C3/ meteorite heated at 400-1000 C

Noble gases, C and S, are lost from Allende samples heated for 1 week at temperatures of 400-1000 C in a low pressure environment. In the extreme, losses of He-3 and He-4 are about 100 x while for C, S and Ne, Ar and Kr isotopes and Xe-132 these are less than or equal to 10 x. Except for He, these losses are less severe than those of Bi or Tl from samples heated in the same runs. Significant He, Ne and Ar isotopic fractionation during heating indicates preferential outgassing of specific reservoirs. Next to He, Ar-40 is the most labile of those species considered here but still less so than Bi or Tl. L-group (but not H- or LL-group) chondrites may have lost mobile elements like Tl while being outgassed after late impact-associated heating. A less likely alternative involving a collateral relation between condensation conditions and depth in a parent object may also explain the L-group trend.

Herzog, G. F.↗
NASA NTRS1986

Studies of light noble gases in mineral grains from lunar soils: A status report

Among the lunar soil constituents, monomineralic grains deserve special attention. Noble gases of carefully prepared mineral separates from lunar bulk soils were studied. The major results and conclusions of these investigations are summarized, in the context of both the regolith evolution and the history of the solar corpuscular radiation. With regard to the most abundant noble gas component in the regolith samples (the solar gases) the mineral grains have mainly two properties giving these particles among all soil constituents the best characteristics as sensors for solar gases, despite the fact, that the noble gas concentrations in a mineral separate are 10 to 60 times lower that those in a bulk sample of the same grain size. The first of these properties is the mineral dependent retentivity of the light gases He and Ne, the second property concerns the relatively short time during which a mineral grain acquires it solar gases. These two points are briefly discussed.

Wieler, R.↗
NASA NTRS1986

Noble gases in the diamond-free ureilite, ALHA 78019 - The roles of shock and nebular processes

The noble gases for unshocked ureilite ALHA 78019 and moderately shocked ureilite Kenna are measured. The preparation of the samples and the analysis procedures are described. The analyses reveal that for ALHA 78019 the residue yield equals 2.5 percent of the original mass of the meteorite and 25 percent of the gas is contained in the fine-grained amorphous carbon, and for Kenna the residue yield equals 2.9 percent and 60 percent of the noble gas is contained in the carbon. It is noted that the gases and carbon are present in the ureilites prior ot the shock that produced the diamond, and the shock has no effect on the origin of the carbon in these meteorites. The source of the gas-rich carbon in the ureilite ALHA 78019 is investigated; the Xe-130/C ratio, which equals 4.2 x 10 to the -10th, implies that the gases were acquired while the ureilite was exposed to the solar nebula.

Wacker, J. F.↗
NASA NTRS1988

Noble gases as tracers of the origin and evolution of the Martian atmosphere and the degassing history of the planet

Noble gas analysis of Martian samples can provide answers to a number of crucial questions. Some of the most obvious benefits will be in Martian chronology, using techniques that have been applied to lunar samples. However, these are by no means the only relevant noble gas studies possible. Since Mars has a substantial atmosphere, noble gases can be used to study the origin and evolution of that atmosphere, including the degassing history of the planet. This type of study can provide constraints on: (1) the total noble gas inventory of the planet, (2) the number of noble gas reservoirs existing, and (3) the exchange of gases between these reservoirs. How to achieve these goals are examined.

Swindle, T. D.↗
DOE OSTI2026

Detection of scintillation light in noble gases with wavelength-shifting optical fibers

Wavelength-shifting (WLS) techniques enable particle detectors based on noble gases, whose scintillation light is predominantly emitted in the vacuum-ultraviolet. We investigate WLS fibers coated with tetraphenyl butadiene (TPB) for scintillation light detection in gaseous xenon and argon at pressures up to 8.5 bar, motivated by future high-pressure xenon time-projection chambers of the NEXT program. Two detector configurations are studied: an elongated high-pressure vessel with four PTFE panels equipped with WLS fibers read by temperature-stabilized SiPMs, and a compact box-shaped detector operated at 1 bar Xe with WLS fibers read out by PMTs. Both operate with continuous gas purification. The detector response is characterized using cosmic muons and alpha particles from a $^{241}$Am source. With the SiPM setup, we measure a light collection efficiency (LCE) of ${1.18 \pm 0.01~\mathrm{(sta.)}~^{+0.07}_{-0.09}~\mathrm{(sys.)}~\%}$ for xenon and ${1.07 \pm 0.01~\mathrm{(sta.)}~^{+0.06}_{-0.08}~\mathrm{(sys.)}~\%}$ for argon. With PMT readout, we measure a LCE of ${0.45 \pm 0.01~\mathrm{(sta.)} \pm 0.05~\mathrm{(sys.)}~\%}$ in xenon, in agreement with the SiPM result once photon detection efficiency is accounted for. Average scintillation waveforms in xenon and argon are studied to assess the time structure of the emitted light. Cosmic-muon measurements yield a mean energy required to produce a scintillation photon $45\pm7~\mathrm{(sta.)}~^{+4}_{-5}~\mathrm{(sys.)}~\mathrm{eV}$ at 1.5 bar, in agreement with the literature. The results demonstrate that TPB-coated WLS fiber systems can reliably detect scintillation light in high-pressure gaseous noble detectors, with a LCE representing an upper limit for realistic large-scale TPCs, where additional photon losses from materials and fiber attenuation are expected.

Soleti, S. R. [Donostia Intl. Phys. Ctr., San Seba↗
NASA NTRS1987

Implications of isotopic signatures of noble gases for the origin and evolution of terrestrial atmospheres

It is contented that the initial quantities of noble gases present in planetesimals were controlled by the sizes and masses of the planets, and fit with a model of successive accretion. The successive accretion model proposed for the origin of terrestrial planets is based upon: (1) the sequence of zones of condensation of solar nebula, (2) the condensation sequence of minerals, iron and nickel in different P-T regimes of the solar nebula, and (3) the sequence in the nucleation of iron cores of the terrestrial planets.

Rao, A. S. P.↗
NASA NTRS2003

Elastic Properties of Films of Water and Noble Gases Condensed at Low Temperatures

We have shown that there are extensive similarities between the quench-condensed noble gas films and those of amorphous water ice. In particular, both can be quite soft upon deposition and can stiffen considerably when annealed. Furthermore, this stiffening follows a logarithmic time dependence for all substances. The temperature dependence of these behaviors scales with the triple point. The results shown here show a strong thickness dependence, which has implications for any study of mechanical properties of films on substrates. The temperature dependence of the stiffening and the stiffening rate have now been characterized for the noble gases, and these observations provide a roadmap for new experiments on amorphous water ice.

Pohl, Robert O.↗
NASA NTRS1990

Angular correlation studies in noble gases

There has been a recent revival of interest in the measurement of angular correlation of annihilation photons from the decay of positrons and positronium in gases. This revival has been stimulated by the possibility offered by the technique to shed new light on the apparently low positronium formation fraction in the heavier noble gases and to provide information on positronium quenching processes in gases such as oxygen. There is also the potential for learning about positronium slowing down in gases. This review focuses on experimental noble gas work and considers what new information has been, and may be, gained from these studies.

Coleman, P. G.↗
NASA NTRS1993

Noble gases in twenty Yamato H-chondrites: Comparison with Allan Hills chondrites and modern falls

Concentration and isotopic composition of noble gases have been measured in 20 H-chrondrites found on the Yamato Mountains ice fields in Antarctica. The distribution of exposure ages as well as of radiogenic He-4 contents is similar to that of H-chrondrites collected at the Allan Hills site. Furthermore, a comparison of the noble gas record of Antarctic H-chrondrites and finds or falls from non-Antarctic areas gives no support to the suggestion that Antarctic H-chrondrites and modern falls derive from differing interplanetary meteorite populations.

Loeken, TH.↗
NASA NTRS1977

Noble gases in separated meteoritic minerals - Murchison /C2/, Ornans /C3/, Karoonda /C5/, and Abee /E4/

The distribution of all five noble gases was measured in four meteorites of different classes by mass spectrometry and stepwise heating of HCl-HF-insoluble residues and of samples treated with HNO3 and atomic oxygen. The distribution of the gases among the three main phases, chromite, polymer, and the ill-defined Q-phase, was determined, and also the isotopic distribution of the gases in the phases was obtained.

Srinivasan, S.↗