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1

Fluid clathrate system for continuous removal of heavy noble gases from mixtures of lighter gases  

DOEpatents

An apparatus and method are disclosed for separation of heavy noble gas in a gas volume. An apparatus and method have been devised which includes a reservoir containing an oil exhibiting a clathrate effect for heavy noble gases with a reservoir input port and the reservoir is designed to enable the input gas volume to bubble through the oil with the heavy noble gas being absorbed by the oil exhibiting a clathrate effect. The gas having reduced amounts of heavy noble gas is output from the oil reservoir, and the oil having absorbed heavy noble gas can be treated by mechanical agitation and/or heating to desorb the heavy noble gas for analysis and/or containment and allow recycling of the oil to the reservoir. 6 figs.

Gross, K.C.; Markun, F.; Zawadzki, M.T.

1998-04-28

2

Heavy noble gases in solar wind delivered by Genesis mission  

NASA Astrophysics Data System (ADS)

One of the major goals of the Genesis Mission was to refine our knowledge of the isotopic composition of the heavy noble gases in solar wind and, by inference, the Sun, which represents the initial composition of the solar system. This has now been achieved with permil precision: 36Ar/38Ar = 5.5005 0.0040, 86Kr/84Kr = .3012 .0004, 83Kr/84Kr = .2034 .0002, 82Kr/84Kr = .2054 .0002, 80Kr/84Kr = .0412 .0002, 78Kr/84Kr = .00642 .00005, 136Xe/132Xe = .3001 .0006, 134Xe/132Xe = .3691 .0007, 131Xe/132Xe = .8256 .0012, 130Xe/132Xe = .1650 .0004, 129Xe/132Xe = 1.0405 .0010, 128Xe/132Xe = .0842 .0003, 126Xe/132Xe = .00416 .00009, and 124Xe/132Xe = .00491 .00007 (error-weighted averages of all published data). The Kr and Xe ratios measured in the Genesis solar wind collectors generally agree with the less precise values obtained from lunar soils and breccias, which have accumulated solar wind over hundreds of millions of years, suggesting little if any temporal variability of the isotopic composition of solar wind krypton and xenon. The higher precision for the initial composition of the heavy noble gases in the solar system allows (1) to confirm that, exept 136Xe and 134Xe, the mathematically derived U-Xe is equivalent to Solar Wind Xe and (2) to provide an opportunity for better understanding the relationship between the starting composition and Xe-Q (and Q-Kr), the dominant current planetary component, and its host, the mysterious phase-Q.

Meshik, Alex; Hohenberg, Charles; Pravdivtseva, Olga; Burnett, Donald

2014-02-01

3

Noble Gases  

NASA Astrophysics Data System (ADS)

The noble gases are the group of elements - helium, neon, argon, krypton, xenon - in the rightmost column of the periodic table of the elements, those which have "filled" outermost shells of electrons (two for helium, eight for the others). This configuration of electrons results in a neutral atom that has relatively low electron affinity and relatively high ionization energy. In consequence, in most natural circumstances these elements do not form chemical compounds, whence they are called "noble." Similarly, much more so than other elements in most circumstances, they partition strongly into a gas phase (as monatomic gas), so that they are called the "noble gases" (also, "inert gases"). (It should be noted, of course, that there is a sixth noble gas, radon, but all isotopes of radon are radioactive, with maximum half-life a few days, so that radon occurs in nature only because of recent production in the U-Th decay chains. The factors that govern the distribution of radon isotopes are thus quite different from those for the five gases cited. There are interesting stories about radon, but they are very different from those about the first five noble gases, and are thus outside the scope of this chapter.)In the nuclear fires in which the elements are forged, the creation and destruction of a given nuclear species depends on its nuclear properties, not on whether it will have a filled outermost shell when things cool off and nuclei begin to gather electrons. The numerology of nuclear physics is different from that of chemistry, so that in the cosmos at large there is nothing systematically special about the abundances of the noble gases as compared to other elements. We live in a very nonrepresentative part of the cosmos, however. As is discussed elsewhere in this volume, the outstanding generalization about the geo-/cosmochemistry of the terrestrial planets is that at some point thermodynamic conditions dictated phase separation of solids from gases, and that the Earth and the rest of the inner solar were made by collecting the solids, to the rather efficient exclusion of the gases. In this grand separation the noble gases, because they are noble, were partitioned strongly into the gas phase. The resultant generalization is that the noble gases are very scarce in the materials of the inner solar system, whence their common synonym "rare gases."This scarcity is probably the most important single feature to remember about noble-gas cosmochemistry. As illustration of the absolute quantities, for example, a meteorite that contains xenon at a concentration of order 10 -10 cm3STP g -1 (410-15 mol g-1) would be considered relatively rich in xenon. Yet this is only 0.6 ppt (part per trillion, fractional abundance 10-12) by mass. In most circumstances, an element would be considered efficiently excluded from some sample if its abundance, relative to cosmic proportions to some convenient reference element, were depleted by "several" orders of magnitude. But a noble gas would be considered to be present in quite high concentration if it were depleted by only four or five orders of magnitude (in the example above, 10-10 cm3STP g-1 of xenon corresponds to depletion by seven orders of magnitude), and one not uncommonly encounters noble-gas depletion of more than 10 orders of magnitude.The second most important feature to note about noble-gas cosmochemistry is that while a good deal of the attention given to noble gases really is about chemistry, traditionally a good deal of attention is also devoted to nuclear phenomena, much more so than for most other elements. This feature is a corollary of the first feature noted above, namely scarcity. A variety of nuclear transmutation processes - decay of natural radionuclides and energetic particle reactions - lead to the production of new nuclei that are often new elements. Most commonly, the quantity of new nuclei originating in nuclear transmutation is very small compared to the quantity already present in the sample in question,

Podosek, F. A.

2003-12-01

4

First complete isotopic analysis of Solar Wind heavy noble gases in Genesis Aluminum collectors  

NASA Astrophysics Data System (ADS)

Analyses of noble gases implanted into Genesis Solar Wind (SW) collectors and their comparison with the gases from solar-wind rich lunar and meteoritic materials may constrain an extent of temporal variations of isotopic composition of the solar wind. Here we report our isotope measurements of all heavy noble gas isotopes including low abundant 126Xe, 124Xe and 78Kr. Two aluminum Genesis collectors were used in this study: Aluminum on Sapphire (AloS) and Polished Aluminum Collector (PAC). Solar Wind (SW) noble gases were extracted using IR- and UV-lasers operated in Q-switched mode. Purified gases were analyzed in the modified 8-multiplier mass spectrometer Noblesse, custom built by Nu-Instruments (UK) for microanalyses of heavy noble gases. SW-Ar was analyzed using UV-depth profiling, which clearly demonstrated depth dependant isotope fractionation caused by SW-implantation at constant ion velocities. The cumulative SW-Ar composition is in good agreement with our earlier analyses made by a single multiplier mass spectrometer (36Ar/38Ar = 5.501 0.002, [1]). SW-Kr was found to have the following isotopic composition: 86Kr/84Kr = .3012 .0004, 83Kr/84Kr = .2034 .0002, 82Kr/84Kr = .2054 .0002, 80Kr/84Kr = .0412 .0002, and 78Kr/84Kr = .00642 .00005. These results are statistically indistinguishable from SW-Kr composition based on the lunar regolith data [2]. Our best current estimate of SW-Xe composition obtained from 25 independent analyses ran at different experimental conditions is: 136Xe/132Xe = .3003 .0006, 134Xe/132Xe = .3692 .0007, 131Xe/132Xe = .8263 .0013, 130Xe/132Xe = .1649 .0004, 129Xe/132Xe = 1.0401 .00010, 128Xe/132Xe = .0842 .0003, 126Xe/132Xe = .00417 .00009, and 124Xe/132Xe = .00492 .00007. Although small systematical difference between these numbers and lunar SW-Xe is observed, more accurate SW-Xe lunar regolith measurements are required to understand whether or not these differences are real. The total amounts of heavy noble gases accumulated over 853 days of collection are: (2.81 .19)E+10, (1.08 .05)E+07, and (1.15 .04)E+06 atoms/cm2 of 36Ar, 84Kr and 132Xe correspondently. This work is supported by NASA grant NNX07AM76G. [1] Meshik A. P. et al. Science 318, 2007, [2] Pepin R. O. et al. 1995. GCA 59.

Meshik, A.; Pravdivtseva, O.; Hohenberg, C. M.; Burnett, D. S.

2011-12-01

5

Nitrogen and heavy noble gases in ALH 84001: Signatures of ancient Martian atmosphere  

NASA Astrophysics Data System (ADS)

Nitrogen and noble gases have been studied in a bulk sample and three density separates of the Martian orthopyroxenite ALH 84001. The ? 15N values which lie between 85%. and -18%. (and after correcting for cosmogenic contribution, between 46%. and -23%.), define a two component mixing trend in a plot of ? 15N vs. 1/N, with Chassigny as one endmember and another component with 15N ? 46%.. This trend is different from the one defined by the data from EET 79001,C and glass from Zagami. Most of the krypton and xenon are of trapped origin; the ratios 129Xe/ 132Xe and 136Xe/ 132Xe being similar to the Martian atmospheric values as found in EET 79001,C. In addition, small contributions from in situ 238U fission and live 129I decay are evident in some high temperature steps, the later observation attesting to the antiquity of this Martian meteorite. Excesses at 80, 82Kr and 128Xe due to neutron capture effects on bromine and iodine, respectively, are observed in all the samples. These neutron effects are not consistent with in situ production in the meteoroid during cosmic ray exposure and hence should be produced in the Martian atmosphere or surface and enterd the meteorite as a trapped component. The lower ? 15N (?46%.) and 40Ar/ 36Ar ? 1400 in the trapped component of ALH 84001, as compared to the values from EET 79001,C, together with the fact that radiogenic 40Ar and trapped 36Ar, 84Kr, and 132Xe have similar release pattern, are strongly suggestive that the trapped component in ALH 84001 represents Martian atmosphere of 4Ga ago. The noble gas elemental ratios 36Ar/ 132Xe and 84Kr/ 132Xe show an elemental fractionation trend, enriching the heavy noble gases, similar to what has been observed in Nakhla (Drake et al., 1994). Comparing the nitrogen and xenon isotopic records and the radiogenic and stable isotope ratios ( 40Ar/ 129Xe and 39Ar/ 14N) from ALH 84001 representing Martian atmospheric component of 4 Ga ago, with those from EET 79001,C representing Martian atmospheric component of recent past, we infer the following on the evolution of the Martian atmosphere: (a) Xenon isotopic composition, as well as the amounts of xenon have been completely evolved at 4 Ga in Martian atmosphere and almost remained unchanged to the present; (b) The radiogenic 40Ar has not been completely degassed into the atmosphere at 4 Ga; (c) Nitrogen has been lost in a continuous process, leading to an increase in the ratio of 36Ar/ 14N as well as the ? 15N in the present Martian atmosphere as compared to 4 Ga ago. These inferences are consistent with the model predictions (Pepin, 1994).

Murty, S. V. S.; Mohapatra, R. K.

1997-12-01

6

MRI using hyperpolarized noble gases  

Microsoft Academic Search

. The aim of this study was to review the physical basis of MRI using hyperpolarized noble gases as well as the present status\\u000a of preclinical and clinical applications. Non-radioactive noble gases with a nuclear spin 1\\/2 (He-3, Xe-129) can be hyperpolarized\\u000a by optical pumping. Polarization is transferred from circularly polarized laser light to the noble-gas atoms via alkali-metal\\u000a vapors

H.-U. Kauczor; R. Surkau; T. Roberts

1998-01-01

7

Noble gases in the moon  

NASA Technical Reports Server (NTRS)

The abundance and isotopic composition of helium, neon, argon, krypton, and xenon which were released by stepwise heating of lunar fines (15601.64) and (15271.65) were measured spectrometrically. The results of a composition of noble gases released from the lunar fines with noble gases in meteorites and in the earth are presented along with the isotopic composition of noble gases in lunar fines, in meteorites, and in the atmosphere. A study of two isotopically distinct components of trapped xenon in carbonaceous chondrites is also included.

Manuel, O. K.; Srinivasan, B.; Hennecke, E. W.; Sinclair, D. E.

1972-01-01

8

IMPACT REGIMES AND POST-FORMATION SEQUESTRATION PROCESSES: IMPLICATIONS FOR THE ORIGIN OF HEAVY NOBLE GASES IN TERRESTRIAL PLANETS  

SciTech Connect

The difference between the measured atmospheric abundances of neon, argon, krypton, and xenon for Venus, Earth, and Mars is striking. Because these abundances drop by at least 2 orders of magnitude as one moves outward from Venus to Mars, the study of the origin of this discrepancy is a key issue that must be explained if we are to fully understand the different delivery mechanisms of the volatiles accreted by the terrestrial planets. In this work, we aim to investigate whether it is possible to quantitatively explain the variation of the heavy noble gas abundances measured on Venus, Earth, and Mars, assuming that cometary bombardment was the main delivery mechanism of these noble gases to the terrestrial planets. To do so, we use recent dynamical simulations that allow the study of the impact fluxes of comets upon the terrestrial planets during the course of their formation and evolution. Assuming that the mass of noble gases delivered by comets is proportional to the rate at which they collide with the terrestrial planets, we show that the krypton and xenon abundances in Venus and Earth can be explained in a manner consistent with the hypothesis of cometary bombardment. In order to explain the krypton and xenon abundance differences between Earth and Mars, we need to invoke the presence of large amounts of CO{sub 2}-dominated clathrates in the Martian soil that would have efficiently sequestered these noble gases. Two different scenarios based on our model can also be used to explain the differences between the neon and argon abundances of the terrestrial planets. In the first scenario, cometary bombardment of these planets would have occurred at epochs contemporary with the existence of their primary atmospheres. Comets would have been the carriers of argon, krypton, and xenon, while neon would have been gravitationally captured by the terrestrial planets. In the second scenario, we consider impacting comets that contained significantly smaller amounts of argon, an idea supported by predictions of noble gas abundances in these bodies, provided that they formed from clathrates in the solar nebula. In this scenario, neon and argon would have been supplied to the terrestrial planets via the gravitational capture of their primary atmospheres whereas the bulk of their krypton and xenon would have been delivered by comets.

Mousis, Olivier; Petit, Jean-Marc; Picaud, Sylvain; Thomas, Caroline [Universite de Franche-Comte, Institut UTINAM, CNRS/INSU, UMR 6213, 25030 Besancon Cedex (France); Lunine, Jonathan I. [Dipartimento di Fisica, Universita degli Studi di Roma 'Tor Vergata', Rome (Italy); Schmitt, Bernard [Universite Joseph Fourier, Laboratoire de Planetologie de Grenoble, CNRS/INSU, UMR 5109, Observatoire de Sciences de l'Univers de Grenoble (France); Marquer, Didier [Universite de Franche-Comte, Chrono-Environnement, CNRS/INSU, UMR 6249, 25030 Besancon Cedex (France); Horner, Jonathan, E-mail: olivier.mousis@obs-besancon.f [Department of Physics, Science Laboratories, University of Durham, South Road, Durham, DH1 3LE (United Kingdom)

2010-05-10

9

Theoretical study of the higher valence states of the noble gases and the heavy alkali metals  

SciTech Connect

The noble gases have been extensively investigated in recent years especially the compounds of xenon and krypton. That is, the filled electron shells of xenon and krypton which were formerly thought to be inert are actually able to participate in chemical bond formation. In addition, a series of authors have inquired into the ability of the inner electrons of the alkali metals rubidium and cesium, which are located directly after krypton and xenon respectively in the periodic table, to participate in chemical bond formation. An experimental study of and LCAO-MO calculations on the alkali metal monoxides showed that the formation of the metal-oxygen bond involved the mixing of the 4p orbitals of Rb and the 5p orbitals of Cs with the 2p orbitals of the oxygen. To elucidate the possibility of obtaining new, as yet unsynthesized compounds we undertook a qualitative analysis of the electron structure of the oxides of argon, krypton, and xenon and the isoelectronic compounds of rubidium and cesium where all of these elements are in high oxidation states.

Spitsyn, V.I.; Ionova, G.V.; Kiseleva, A.A.

1983-05-01

10

Noble Gases in Sea Water.  

PubMed

Concentrations of noble gases in samples of sea water obtained at depths to 3437 meters from a Pacific Ocean station were measured by mass spectrometry. An excess of helium, in relation to concentrations of the other noble gases, is attributed to influx of atoms of this gas from the sediments where it is produced by the natural radioactive decay of members of the uranium and thorium series. On the basis of a steady-state model, the escape of helium from the earth is calculated at 6.4 x 10(13) atoms per square centimeter per year. PMID:17832398

Bieri, R; Koide, M; Goldberg, E D

1964-11-20

11

Resonance Ionization of Heavy Noble Gases: The Potential of KR and Xe Measurements from Single Pre-Solar Grains  

Microsoft Academic Search

Since the first reliable indication of the existence of non-terrestrial composition of Xe isotopes in meteorites by Reynolds [1,2], anomalies have been found in the isotopic composition of many elements in meteorites, implying a plurality of nucleosynthetic processes, and indicating that the initial conditions leading to the formation of the solar system were quite diverse [3]. Noble gases provide a

N. Thonnard

1995-01-01

12

Light Collection in Liquid Noble Gases  

ScienceCinema

Liquid noble gases are increasingly used as active detector materials in particle and nuclear physics. Applications include calorimeters and neutrino oscillation experiments as well as searches for neutrinoless double beta decay, direct dark matter, muon electron conversion, and the neutron electric dipole moment. One of the great advantages of liquid noble gases is their copious production of ultraviolet scintillation light, which contains information about event energy and particle type. I will review the scintillation properties of the various liquid noble gases and the means used to collect their scintillation light, including recent advances in photomultiplier technology and wavelength shifters.

13

Noble gases in the dynamic mantle  

NASA Astrophysics Data System (ADS)

It is proposed that noble gases in the mantle reside mainly in a "hybrid pyroxenite" component that is formed as melt from old subducted oceanic crust reacts with surrounding refractory peridotite under mid-ocean ridges. The gases are presumed to have been acquired early in Earth history, and mixing under mid-ocean ridges of melts from pyroxenites and old crust would pass the noble gases to successive generations of pyroxenites. Much of the complement of noble gases would not be erupted at mid-ocean ridges and would recirculate in the mantle, so the hybrid pyroxenite would degas rather slowly over Earth history. The hybrid pyroxenite would also be denser than average mantle and would tend to settle into the D? zone at the base of the mantle, in the same way as subducted oceanic crust. Because residence times in D? are longer than in the rest of the mantle, the D? pyroxenite would be less degassed and its noble gases would be less radiogenic than that in the mid-ocean ridge basalt (MORB) source. Plumes could therefore tap a mixture of old, degassed oceanic crust and less degassed hybrid pyroxenite. This could resolve the long-standing question of the source of unradiogenic helium in many ocean island basalts (OIBs). Abundances of noble gases are not very well constrained and are plausibly larger than conventional estimates, which would remove the need for a large, deep, "undegassed" reservoir. The 40Ar mass balance may be satisfied if account is taken of uncertainties in the potassium content of the continental crust and the bulk silicate Earth and in the Earth's total budget of 40Ar. A relatively simple quantitative theory for the evolution of the noble gases is presented that accounts for the present concentrations and isotopic compositions of helium, neon, and argon in the MORB and OIB source regions. In particular, it confirms that longer residence times in D? can account for the less radiogenic noble gases in OIBs.

Davies, Geoffrey F.

2010-03-01

14

Resonance Ionization of Heavy Noble Gases: The Potential of KR and Xe Measurements from Single Pre-Solar Grains  

NASA Astrophysics Data System (ADS)

Since the first reliable indication of the existence of non-terrestrial composition of Xe isotopes in meteorites by Reynolds [1,2], anomalies have been found in the isotopic composition of many elements in meteorites, implying a plurality of nucleosynthetic processes, and indicating that the initial conditions leading to the formation of the solar system were quite diverse [3]. Noble gases provide a unique window into the composition of the progenitor material to the solar system [4]. Stellar evolution may contribute by the s-process, r-process, p-process, etc., each with its own isotopic distribution. Kr and Xe are especially useful as the large number of isotopes (7 in the 78Kr to 86Kr range, and 9 in the 124Xe to 136Xe range) provide many clues to help unravel the multiple sources to the measured abundances. Although Xe has been measured and analyzed considerably more frequently than Kr in meteorite studies, this has only partially been due to the wealth of information derivable from Xe studies, but also, due to experimental difficulties encountered in Kr measurements. Early in the development of stellar nucleosynthesis, 86Kr was proposed as a chronometer of the s-process [5], but until recently has provided unreliable results [6]. Other interesting properties derivable from Kr isotope measurements include 78Kr as an indication of spallation history, 80Kr as a stellar thermometer, and 81Kr and 83Kr to determine cosmic ray exposure ages. Studies of highly refractory microscopic grains (diamond, graphite and SiC) separated from the much more abundant carbonaceous matrix in primitive meteorites have shown a remarkable isotopic composition diversity in a small fraction of single grains from the same meteorite, implying multiple stellar sources [4]. Ion microprobe measurements have been possible of the major constituents of single interstellar grains [7,8] and of He and Ne using a state-of-the-art static noble gas mass spectrometer [9-11]. But, a recent attempt to measure noble gases from fourteen individual "X" SiC grains, previously identified by ion microprobe analysis, was unsuccessful with the 2,000 132Xe atom detection limit of the mass spectrometer [12,13]. From the Kr concentration measurements of SiC particles KJF by Lewis et al. [6], a 2 micrometer diameter particle will on average contain 134 Kr atoms. If only 4% of the SiC grains contain the majority of the noble gas atoms, then a single gas rich grain will contain 3,350 Kr atoms, or 12, 75, 385, 398, 1910, and 580 atoms for 78Kr through 86Kr, respectively. The Xe single-grain abundances would be similar. Resonance ionization, an emerging laser-based element analysis technique, is being harnessed to a wide variety of problems in which minute quantities of a particular element need to be measured efficiently in the presence of an overwhelmingly larger background of other materials [14]. By utilizing lasers tuned to specific atomic energy levels of the analyte element, ions are produced selectively in a mass spectrometer with much higher efficiency than possible using conventional methods, such as electron bombardment, thermal ionization, or ion sputtering. In a static resonance ionization system for noble gases, the combination of high ionization efficiency and sample concentrator results in an extremely fast (~3 min. detection half-life vs. ~60 min. for conventional systems) analyzer with a detection limit of ~100 85Kr atoms [15]. In addition to the almost complete absence of interferences, the short analysis time significantly reduces the background contribution of outgassing in the mass spectrometer. Although using a less efficient laser scheme resulting in slightly slower analyses, a similar system has recently been completed and dedicated to extraterrestrial Xe measurements [16]. At the newly formed Institute for Rare Isotope Measurements [17], the noble gas equipment that had previously been at Atom Sciences [14,15] is being re-installed and upgraded to provide routine noble gas measurements from terrestrial and extraterrestrial samples. The pres

Thonnard, N.

1995-09-01

15

Noble gases in the dynamic mantle  

Microsoft Academic Search

It is proposed that noble gases in the mantle reside mainly in a hybrid pyroxenite component that is formed as melt from old subducted oceanic crust reacts with surrounding refractory peridotite under mid-ocean ridges. The gases are presumed to have been acquired early in Earth history, and mixing under mid-ocean ridges of melts from pyroxenites and old crust would pass

Geoffrey F. Davies

2010-01-01

16

Diffusive separation of noble gases and noble gas abundance patterns in sedimentary rocks  

SciTech Connect

The mechanisms responsible for noble gas concentrations, abundance patterns, and strong retentivity in sedimentary lithologies remain poorly explained. Diffusion-controlled fractionation of noble gases is modeled and examined as an explanation for the absolute and relative abundances of noble gases observed in sediments. Since the physical properties of the noble gases are strong functions of atomic mass, the individual diffusion coefficients, adsorption coefficients and atomic radii combine to impede heavy noble gas (Xe) diffusion relative to light noble gas (Ne) diffusion. Filling of lithic grains/half-spaces by diffusive processes thus produces Ne enrichments in the early and middle stages of the filling process with F(Ne) values similar to that observed in volcanic glasses. Emptying lithic grains/half-spaces produces a Xe-enriched residual in the late (but not final) stages of the process producing F(Xe) values similar to that observed in shales. 'Exotic but unexceptional' shales that exhibit both F(Ne) and F(Xe) enrichments can be produced by incomplete emptying followed by incomplete filling. This mechanism is consistent with literature reported noble gas abundance patterns but may still require a separate mechanism for strong retention. A system of labyrinths-with-constrictions and/or C-, Si-nanotubes when combined with simple adsorption can result in stronger diffusive separation and non-steady-state enrichments that persist for longer times. Enhanced adsorption to multiple C atoms inside C-nanotubes as well as dangling functional groups closing the ends of nanotubes can provide potential mechanisms for 'strong retention'. We need new methods of examining noble gases in rocks to determine the role and function of angstrom-scale structures in both the diffusive enrichment process and the 'strong retention' process for noble gas abundances in terrestrial rocks.

Torgersen, T.; Kennedy, B.M.; van Soest, M.C.

2004-06-14

17

Hyperpolarized noble gases as contrast agents.  

PubMed

Hyperpolarized noble gases ((3)He and (129)Xe) can provide NMR signal enhancements of 10,000 to 100,000 times that of thermally polarized gases and have shown great potential for applications in lung magnetic resonance imaging (MRI) by greatly enhancing the sensitivity and contrast. These gases obtain a highly polarized state by employing a spin exchange optical pumping technique. In this chapter, the underlying physics of spin exchange optical pumping for production of hyperpolarized noble gases is explained and the basic components and procedures for building a polarizer are described. The storage and delivery strategies of hyperpolarized gases for in vivo imaging are discussed. Many of the problems that are likely to be encountered in practical experiments and the corresponding detailed approaches to overcome them are also discussed. PMID:21874479

Zhou, Xin

2011-01-01

18

Noble Gases in a Heterogeneous, Dynamic Mantle  

NASA Astrophysics Data System (ADS)

The source of unradiogenic noble gases in oceanic basalts has been perhaps the most enigmatic aspect of mantle geochemistry. One popular hypothetical source, a large enriched layer deep in the mantle, is incompatible with geophysical evidence. Not only does seismic tomography preclude a separate lower mantle, but any such layer ought to generate mantle plumes, and associated hotspot swells, much stronger than those observed. The only layering compatible with geophysical evidence is the D region, which is only around 200 km thick and comprises only about 2% of the mantles mass. It is argued that when the major-element heterogeneity of the mantle is more fully considered the noble gas observations can be reconciled with a mantle structure compatible with geophysics and dynamics. The mantle is observed, and expected, to comprise a refractory peridotite matrix containing eclogites and pyroxenites that are more fusible and more enriched in incompatible elements. These heterogeneities will melt deeper, and not all of their off-axis melt will be extracted at mid-ocean ridges, so it will recirculate internally within the mantle. Such recirculated heterogeneities will retain their incompatible elements, and the incompatibles will become concentrated within them, probably from early in Earth history. The heterogeneities, more mafic than ultramafic, will tend to be denser than average mantle through most of the mantles depth. They will therefore tend to accumulate within the D region, as dynamical models have demonstrated for subducted (mafic) oceanic crust. D would thus contain a mixture of subducted oceanic crust, which will have been degassed at the surface, and recirculated heterogeneities carrying noble gases. Dynamical models show that residence times in D are longer than for the mantle interior, so the noble gases in D would tend to be older, as well as higher in concentration. This can explain why mantle plumes, tapping D, contain noble gases that are less radiogenic than mid-ocean ridge basalts. Quantitative models bear this out. This picture requires that the bulk of the mantles noble gases reside in the MORB source, which comprises most of the mantle. Recent estimates of MORB source composition may have underestimated the content of incompatible elements because they are tied to peridotite compositions, which will probably not have equilibrated with all of the incompatibles residing in fusible heterogeneities. Most estimates of MORB source composition also focus on so-called normal MORB, which is actually more depleted than the mean. When more enriched components and plume-related components are considered, the budgets of the noble gases can be plausibly accounted for.

Davies, G. F.

2010-12-01

19

Preserving noble gases in a convecting mantle.  

PubMed

High (3)He/(4)He ratios sampled at many ocean islands are usually attributed to an essentially undegassed lower-mantle reservoir with high (3)He concentrations. A large and mostly undegassed mantle reservoir is also required to balance the Earth's (40)Ar budget, because only half of the (40)Ar produced from the radioactive decay of (40)K is accounted for by the atmosphere and upper mantle. However, geophysical and geochemical observations suggest slab subduction into the lower mantle, implying that most or all of Earth's mantle should have been processed by partial melting beneath mid-ocean ridges and hotspot volcanoes. This should have left noble gases in both the upper and the lower mantle extensively outgassed, contrary to expectations from (3)He/(4)He ratios and the Earth's (40)Ar budget. Here we suggest a simple solution: recycling and mixing of noble-gas-depleted slabs dilutes the concentrations of noble gases in the mantle, thereby decreasing the rate of mantle degassing and leaving significant amounts of noble gases in the processed mantle. As a result, even when the mass flux across the 660-km seismic discontinuity is equivalent to approximately one lower-mantle mass over the Earth's history, high (3)He contents, high (3)He/(4)He ratios and (40)Ar concentrations high enough to satisfy the (40)Ar mass balance of the Earth can be preserved in the lower mantle. The differences in (3)He/(4)He ratios between mid-ocean-ridge basalts and ocean island basalts, as well as high concentrations of (3)He and (40)Ar in the mantle source of ocean island basalts, can be explained within the framework of different processing rates for the upper and the lower mantle. Hence, to preserve primitive noble gas signatures, we find no need for hidden reservoirs or convective isolation of the lower mantle for any length of time. PMID:19478782

Gonnermann, Helge M; Mukhopadhyay, Sujoy

2009-05-28

20

Planetary Formation and Evolution Revealed with a Saturn Entry Probe: The Importance of Noble Gases  

Microsoft Academic Search

The determination of Saturn's atmospheric noble gas abundances are critical to understanding the formation and evolution of Saturn, and giant planets in general. These measurements can only be performed with an entry probe. A Saturn probe will address whether enhancement in heavy noble gases, as was found in Jupiter, are a general feature of giant planets, and their ratios will

Jonathan J. Fortney; Kevin Zahnle; Isabelle Baraffe; Adam Burrows; Sarah E. Dodson-Robinson; Gilles Chabrier; Tristan Guillot; Ravit Helled; Franck Hersant; William B. Hubbard; Jack J. Lissauer; Mark S. Marley

2009-01-01

21

Laser Heating Extraction of Noble Gases from Allende and Murchison  

Microsoft Academic Search

We attempt to investigate noble gas components and their carrier phases by melting a small portion of meteorites employing a laser microprobe and by measuring all noble gas isotopes. As a preliminary study, noble gases were extracted from various materials of Allende and Murchison carbonaceous chondrites using a pulse Nd-YAG laser. The laser shot makes a pit 100-300 micrometers in

K. Nagao; Y. Miura

1992-01-01

22

Where do noble gases hide in space?  

NASA Astrophysics Data System (ADS)

Observations showing anomalous amounts of noble gas, especially in planetary atmospheres, are at the origin of a series of controversial interpretations from 1990 to nowadays (Hersant et al. (2004)). If, in a first step, we adopt a chemical point of view, we have to consider the possibility of associations of such elements (though usually considered as non reactive), with other molecules or atoms. Such complexes could trap the noble gases in some astrophysical objects at one time of their evolution, for example, in the early step of formation of protoplanetary disks. But two questions have to be answered to assert this type of hypothesis: which stable compounds could exist taking into account the environnement and which reactions could lead to such compounds? Hydrogen being by far the most abundant element in space, and neutral systems whose cohesion is driven by weak Van der Waals forces being unable to resist turbulence in space, the first and simplest association to consider is the one between the noble gas and the H3+ ion. Thus, DFT in the B3LYP, PW91 and BHandHLYP formalisms together with ab-initio methods of Coupled Cluster type have been employed to determine the equilibrium geometries, the spectroscopic constants and the bonding energies of the possible complexes between noble gases and hydrogen. We have first performed an extensive study of the associations ArnH3+ possible with Argon (the first noble gas which rose questions in the area of Jupiter's poles). We have found that several Argon atoms can be stabilized around the H3+ ion, the first complexation being in the plane of the ion. The spectroscopic data (rotational constants, dipole moments and IR signatures) were calculated (Pauzat & Ellinger (2005)) so that the laboratory experiments and spatial observations of these species could then be carried out. From our results and previous observations on this complex (Bogey et al. (1987)) we can say that the ArH3+ ion is certainly a good candidate for observation and, if observed, a good test of the hypothesis. In a second step, we have extended the study of the association of one atom of noble gas X with the H3+ ion, to all noble gas from Helium to Xenon. All XH3+ are found stable with respect to dissociation but the stability of the complexes increases with the size and polarizability of the X atom. Unfortunately, the more stable complexes are also those with the less abundant noble gas. Particular attention has been given to Helium. The association HeH+ between the two most abundant elements has been looked for in most areas of space and nowhere detected. The problem is worth being addressed. State of the art calculations can be performed for these small size molecules. We found that the HeH3+ ion is stable by only 0.1Kcal/mol with respect to its components (He and H3+). By contrast, HeH2+ is found stable by a much larger binding energy (6Kcal/mol). However, from all our investigations, there is no way to form it. As an efficient way to form the simplest association, HeH+, has also not been found, it seems that Helium is to be observed only as an isolated species and does not participate into any chemistry in spite of its large abundance in space.

Pauzat, F.; Ellinger, Y.

23

Ionization and Positronium Formation in Noble Gases  

NASA Astrophysics Data System (ADS)

This paper reviews key results of our recent study [Marler et al., Phys. Rev. A 71, 022701 (2005)] of direct ionization and positronium formation in the noble gases from the thresholds for these processes to 90 eV. Results for argon and xenon are emphasized. The original study also reports similar results for neon and krypton. The experiment uses a cold, trap-based positron beam and scattering in a strong magnetic field to make absolute cross section measurements. Comparison with a detailed set of previous measurements yields reasonably good absolute agreement. A third, independent analysis was used to resolve the remaining discrepancies to a < 5% level in argon, krypton and xenon. Key aspects of the work, comparison with available theory, and open questions for future research are discussed.

Marler, J. P.; Sullivan, J. P.; Surko, C. M.

2006-11-01

24

Trends In Positron Scattering From Noble Gases  

NASA Astrophysics Data System (ADS)

We have a program of low energy (< 100 eV), high resolution (~ 60 meV), positron scattering from atoms and molecules which is being facilitated by a high-flux, trapbased positron beamline facility at the Australian National University (Sullivan et al. 2008). The positron beam utilised is a pulsed beam which operates at about 100 Hz. A typical pulse will contain about 1000 positrons. For noble gases, our goals range from establishing "benchmarks" for positron scattering cross sections, to investigation of threshold effects in processes such as positronium formation and ionization. This paper will present examples of trends observed in a number of scattering processes in He, Ne, Ar, Kr and Xe. The project includes investigations of the - elastic cross sections - positronium formation cross sections - total cross sections Where possible the current experimental results will be compared with the best available theoretical calculations and other experimental data from literature.

Jones, A.; Caradonna, P.; Machacek, P.; Makochekanwa, C.; Slaughter, D.; McEachran, R.; Sullivan J.; Buckman, S.

2010-07-01

25

Noble gases in E-chondrites  

NASA Astrophysics Data System (ADS)

The combination of noble gas data for 12 E-chondrites with literature data shows K-Ar ages greater than 4 AE for 14 out of 18 meteorites, while U, Th-He ages are often shorter. Cosmic ray exposure ages are found to differ systematically between types E4 and E6, with the respective, below-16 Myr and above-30 Myr values implying that the E-chondrite parent body predominantly contains a single petrologic type on the 1 km scale of individual impacts in contrast to the mixed parent bodies of the ordinary chondrites. Amounts of planetary gas in E4-E6 chondrites fall in the range for ordinary chondrites of types 4-6, but fail to correlate with petrologic type or volatile trace element contents, in contrast to the ordinary chondrites. Analyses of mineral separates show that the planetary gases are concentrated in an HFand HCl-insoluble mineral, similar to phase Q. The subsolar gases are located in an HCl- and HNO3-resistant phase.

Crabb, J.; Anders, E.

1981-12-01

26

The Noble Gases in A-Level Chemistry.  

ERIC Educational Resources Information Center

Suggests two methods of developing the study of the noble gases: first, the discovery of the elements and recent discovery of xenon show the human face of chemistry (historical development); second, the properties of noble gas compounds (particularly xenon) can be used to test the framework of conventional chemistry. (Author/JM)

Marchant, G. W.

1983-01-01

27

Noble gases in Luna 24 core soils  

NASA Technical Reports Server (NTRS)

Isotopic abundances of the noble gases have been determined in grain size separates of six soils from different depths in the Luna 24 core. Concentrations of cosmogenic Ne-21 in these soils show a complex pattern as a function of soil depth, and are inconsistent with a single stage, in situ production in a static regolith or with a simple model of slow accumulation of previously unirradiated soils followed by a static period. All soils have apparently had a complex pre-irradiation history. Some soils show significant differences in the concentration of cosmogenic Ne-21 between different grain sizes, which is consistent with suggestions that they formed as a mixture of soils with different maturities. The exact subsurface depth relationships of the soils are not known, and several possibilities are discussed. Because of this factor and the complex nature of the soils, the cosmogenic Ne data do not define the depositional-irradiational history of the core. Luna 24 core soils may have been deposited any time during the past 300 million years.

Bogard, D. D.; Hirsch, W. C.

1978-01-01

28

Classical calculation of multiple ionization cross sections of noble gases near Bragg peak energies  

NASA Astrophysics Data System (ADS)

In this paper, we extend our previous work of COBI model to study the multiple ionization and mean charge state of noble gases collided by heavy ions at energies not far from Bragg peaks of several to hundreds keV/amu. Being in good agreement with various experimental data and taking extremely small computational time make the model helpful to study the charge state distribution and multiple ionization of gases transforming to plasmas.

Shao, J. X.; Zhou, M.; Zou, X. R.; Wang, S. Y.; Cheng, C.; Zhou, W.; Ma, X.; Chen, X. M.

2014-04-01

29

Noble gases and radiocarbon in natural gas hydrates  

Microsoft Academic Search

In samples of pure natural gas hydrates from Hydrate Ridge, Cascadia Margin, virtually no helium and neon components are present providing evidence that the light noble gases are not incorporated into the structure of natural methane hydrates. In contrast, the hydrates contain significant amounts of argon, krypton and xenon. These gases show a distinct fractionation pattern, with the heavier ones

Gisela Winckler; Werner Aeschbach-Hertig; Johannes Holocher; Rolf Kipfer; Ingeborg Levin; Christian Poss; Gregor Rehder; Erwin Suess; Peter Schlosser

2002-01-01

30

Photosensitive dopants for liquid noble gases  

DOEpatents

In an ionization type detector for high energy radiation wherein the energy of incident radiation is absorbed through the ionization of a liquid noble gas and resulting free charge is collected to form a signal indicative of the energy of the incident radiation, an improvement comprising doping the liquid noble gas with photosensitive molecules to convert scintillation light due to recombination of ions, to additional free charge.

Anderson, David F. (Wheaton, IL)

1988-01-01

31

Interaction of laser plasmas with noble gases  

Microsoft Academic Search

The interaction of a noble gas jet (Xe, Kr, He) with a laser plasma at a distance of ?1 cm from a solid target (Mg, (CH2)n, LiF, or CF4) was studied for the first time. The line spectra that were excited in the course of charge exchange of multicharged ions\\u000a with noble gas atoms in the interaction region were recorded.

V. E. Levashov; K. N. Mednikov; A. S. Pirozhkov; E. N. Ragozin

2004-01-01

32

Seawater subduction controls the heavy noble gas composition of the mantle.  

PubMed

The relationship between solar volatiles and those now in the Earth's atmosphere and mantle reservoirs provides insight into the processes controlling the acquisition of volatiles during planetary accretion and their subsequent evolution. Whereas the light noble gases (helium and neon) in the Earth's mantle preserve a solar-like isotopic composition, heavy noble gases (argon, krypton and xenon) have an isotopic composition very similar to that of the modern atmosphere, with radiogenic and (in the case of xenon) solar contributions. Mantle noble gases in a magmatic CO2 natural gas field have been previously corrected for shallow atmosphere/groundwater and crustal additions. Here we analyse new data from this field and show that the elemental composition of non-radiogenic heavy noble gases in the mantle is remarkably similar to that of sea water. We challenge the popular concept of a noble gas 'subduction barrier'--the convecting mantle noble gas isotopic and elemental composition is explained by subduction of sediment and seawater-dominated pore fluids. This accounts for approximately 100% of the non-radiogenic argon and krypton and 80% of the xenon. Approximately 50% of the convecting mantle water concentration can then be explained by this mechanism. Enhanced recycling of subducted material to the mantle plume source region then accounts for the lower ratio of radiogenic to non-radiogenic heavy noble gas isotopes and higher water content of plume-derived basalts. PMID:16688169

Holland, Greg; Ballentine, Chris J

2006-05-11

33

Fullerenes: A New Carrier Phase for Noble Gases in Meteorites  

NASA Technical Reports Server (NTRS)

The major focus of our research effort has been to measure the noble gases encapsulated within fullerenes, a new carbon carrier phase and compare it to the myriad of components found in the bulk meteorite acid residues. We have concentrated on the carbonaceous chondrites (Allende, Murchison and Tagish Lake) since they have abundant noble gases, typically with a planetary signature that dominates the stepped-release of the meteorite bulk acid residue. They also contain an extractable fullerene component that can be isolated and purified from the same bulk material.

Becker, Luann

2004-01-01

34

Noble Gases in the Martian Meteorite Tissint  

NASA Astrophysics Data System (ADS)

Noble gas studies in the martian meteorite fall Tissint gave an exposure age of 1.0 Ma and also show excess 82Kr due to (n, gamma) reactions on Br, indicating >22 cm preatmospheric size. Presence of Mars atmospheric component is indicated by 129Xe.

Murty, S. V. S.; Mahajan, R. R.; Ranjith Kumar, P. M.; Chennaoui Aoudjehane, H.

2012-09-01

35

Noble gases in Genesis Collector material: New Measurement Capabilities  

Microsoft Academic Search

The difficult task of measuring heavy noble gas isotopes in collector materials returned by the Genesis Mission has stimulated the development of new noble gas mass spectrometers. A new 8 multiplier instrument was developed and refined in collaboration with Nu-Instruments. This mass spectrometer has demonstrated an inherent sensitivity of 1.8 mA\\/torr, about 3.3 times greater than previous instruments, and it

C. M. Hohenberg; Y. Marrocchi; A. P. Meshik; J. C. Mabry; J. M. Saxton; P. Freedman

2005-01-01

36

Noble gases and halogens in altered MORB and implications for seawater recycling  

NASA Astrophysics Data System (ADS)

Recent studies suggested that the heavy noble gases and halogens are significantly recycled into the mantle through the subduction zone, since a seawater derived signature has been recorded in the mantle [1,2]. However, the processes of how these elements preserve the unique elemental composition of seawater from the ocean floor to the subduction process are unknown. Thus, we propose here a study of altered oceanic crust to identify the respective major host phases of both noble gases and halogens in pre-subducted material. Ten altered MORB coming from the ODP sites 504, 896 and 1256 in the Eastern Pacific Ocean (5.9 and 15 Ma) are being studied. Noble gas isotopes and abundances have been determined using an upgraded VG5400 mass spectrometer. Halogens (Cl, Br, I) are obtained by measuring noble gases on irradiated samples using a MS1 mass spectrometer. The analyses were all obtained from in vacuo crushing release of whole rock samples. Preliminary results show Ne to Xe isotopically identical to air. 3He/4He ratios vary from 4.50.5 (R/RA) to MORB-like values. Heavy noble gas elemental ratios for 9 samples fall within a narrow range, with 130Xe/36Ar and 84Kr/36Ar ratios varying respectively by 10% and 30%. They range from values close to seawater ( air) to values enriched in Xe and Kr going towards mantle values [1]. One altered MORB shows 130Xe/36Kr and 84Kr/36Ar ratios respectively 2 and 5 times greater than the average of the other samples, which suggests the contribution of a sediment component in this sample. Halogen data obtained on 4 samples are in accordance with noble gases results. The Br/Cl molar ratio is constant (1.970.15.10-3) while the I/Cl molar ratio varies significantly by up to one order of magnitude, ranging from 1.20.3.10-6 to 9.90.8.10-6. These results are in favour of a mixing between a seawater endmember and a sediment pore fluid endmember, which remains to be identified. The measurements will be extended to gabbros and sediments forming the oceanic crust. Also, the addition of data obtained by heating to those obtained by crushing will allow us to better constrain the partitioning of both the noble gases and the halogens in pre-subducted material, the identification of the host phases, as well as the controls of the seawater noble gases interaction with the oceanic crust. [1] Holland & Ballentine (2006), Nature 441, 186-191. [2] Sumino et al. (2010), EPSL 294, 163-172.

Chavrit, D.; Burgess, R.; Weston, B.; Abbott, L.; Ballentine, C. J.; Teagle, D. A.; Droop, G.; Pawley, A. R.

2011-12-01

37

Noble gases in Mars atmosphere: new precise analysis with Paloma  

Microsoft Academic Search

The Viking mission embarked a mass spectrometer designed by Alfred O. Nier that yielded the first determination of the elemental and isotopic composition of noble gases in Mars atmosphere. For example, the 40Ar\\/36Ar ratio in martian air is roughly 10 fold that in terrestrial air. This extraordinary accomplishment, however, has furnished only partial results with large analytical uncertainties. For example,

Ph. Sarda

2003-01-01

38

Impact degassing of water and noble gases from silicates  

NASA Technical Reports Server (NTRS)

Previous shock experiments by Ahrens and his colleagues show that degassing of H2O and CO2 occurs at 8-65GPa from hydrous minerals such as serpentine. In early solar system, the impact degassing would have played an important part in the formation of primary-atmospheres of the terrestrial planets. However, degassing conditions of noble gases are not well-known because there are few experiments for them. We conducted some shock recovery experiments to investigate the degassing condition and to understand the degassing mechanisms of water and noble gases. We used natural richterites (Ri), amphibolites (Am), serpentines (Sep) and orthoclases (or) as target samples. These, except Sep, contain radiogenic noble gases such as (40)Ar. The samples were put in stainless steel containers, and were show by a rail gun at ISAS or single-stage powder guns at Nagoya or Tohoku University, Japan. We used two kinds of containers: 'open' type containers having a ventilating path for released volatiles for most of samples and 'closed' type ones for some samples for comparison. On Ri and Sep, we made shock experiments for pre-heated (at 400-500 C) and unheated targets, and for powdered and uncrushed samples. Water and noble gases were analyzed both for the recovered shocked samples and the unshocked original samples, and the fractions of the degassed volatiles were calculated by comparing them. Water content in the sample was analyzed by thermo-gravimetry. Noble gases were extracted by heating the samples under high vacuum and analyzed with a sector-type mass spectrometer.

Azuma, S.; Hiyagon, H.; Iijima, Y.; Syono, Y.

1994-01-01

39

Impact degassing of water and noble gases from silicates  

NASA Astrophysics Data System (ADS)

Previous shock experiments by Ahrens and his colleagues show that degassing of H2O and CO2 occurs at 8-65GPa from hydrous minerals such as serpentine. In early solar system, the impact degassing would have played an important part in the formation of primary-atmospheres of the terrestrial planets. However, degassing conditions of noble gases are not well-known because there are few experiments for them. We conducted some shock recovery experiments to investigate the degassing condition and to understand the degassing mechanisms of water and noble gases. We used natural richterites (Ri), amphibolites (Am), serpentines (Sep) and orthoclases (or) as target samples. These, except Sep, contain radiogenic noble gases such as (40)Ar. The samples were put in stainless steel containers, and were show by a rail gun at ISAS or single-stage powder guns at Nagoya or Tohoku University, Japan. We used two kinds of containers: 'open' type containers having a ventilating path for released volatiles for most of samples and 'closed' type ones for some samples for comparison. On Ri and Sep, we made shock experiments for pre-heated (at 400-500 C) and unheated targets, and for powdered and uncrushed samples. Water and noble gases were analyzed both for the recovered shocked samples and the unshocked original samples, and the fractions of the degassed volatiles were calculated by comparing them. Water content in the sample was analyzed by thermo-gravimetry. Noble gases were extracted by heating the samples under high vacuum and analyzed with a sector-type mass spectrometer.

Azuma, S.; Hiyagon, H.; Iijima, Y.; Syono, Y.

40

Using noble gases to constrain gas exchange and biological productivity  

NASA Astrophysics Data System (ADS)

The five noble gases (He, Ne, Ar, Kr, and Xe) are biologically and chemically inert, making them useful oceanographic tracers. Moreover, the noble gases have a wide range of solubilities and diffusivities, and thus respond differently to physical forcing. We present here a one year time-series of the five noble gases and the isotope 3He, measured in the upper 400 m of the Sargasso Sea with monthly resolution at the Bermuda Atlantic Time-series Site (BATS). Two profiles of the noble gases in the entire water column down to 4200 m are presented as well. We combine the upper ocean noble gas time-series data, nutrient, oxygen, and hydrographic data from BATS, and a one-dimensional vertical mixed layer model (a modified Price-Weller-Pinkel model) in order to quantify air-sea gas exchange processes. We use inverse modeling to quantify the magnitude of both diffusive gas exchange and air injection processes. The estimates obtained constrain the seasonal time-scale gas exchange rate to a precision of 6% and the bubble injection fluxes to 15%, valid for wind speeds up to 15 m/sec. The overall results suggest that the Wanninkhof quadratic formulation needs to be adjusted downward by approximately 20%. Additionally, 3He is used as a tracer of upwelling nutrients in order to constrain new production. Nutrients in the upper thermocline are well correlated with 3He, and thus 3He and nitrate measurements, combined with estimates of gas exchange, are used to quantify the input of new nutrients into the mixed layer. 3He measurement are also used in conjunction with tritium and oxygen data in order to calculate apparent oxygen utilization rates (AOUR) and thus to estimate export production.

Stanley, R.; Jenkins, W. J.; Lott, D. E.; Doney, S. C.

2007-12-01

41

Noble Gases in Carbonatite Magmatism: Oldonyo Lengai  

Microsoft Academic Search

Oldonyo Lengai,Tanzania, is the only volcano on Earth that is actively erupting carbonatitic lavas. In order to further constrain the origin of the Oldonyo Lengai magmas, an expedition to Oldonyo Lengai in July 2005 sampled to volcanic gases. Two fumaroles were sampled, one with a discharging temperature of 124 C, the other more than 168 C. The chemical composition of

P. Burnard; B. Marty; T. Fischer; D. Hilton; F. Mangasini; C. Makene

2006-01-01

42

Noble Gases in Five Rumuruti Chondrites  

NASA Astrophysics Data System (ADS)

Concentration and isotopic composition have been measured in five new R-chondrites: Dar al Gani 417, Northwest Africa 053, Ouzina, Sahara 98248, and Sahara 99531. Two of these meteorites contain solar trapped gases, NWA 053 has an unusual short exposure age of 0.2 Ma.

Weber, H. W.; Schultz, L.

2001-03-01

43

Fullerenes: An extraterrestrial carbon carrier phase for noble gases  

PubMed Central

In this work, we report on the discovery of naturally occurring fullerenes (C60 to C400) in the Allende and Murchison meteorites and some sediment samples from the 65 million-year-old Cretaceous/Tertiary boundary layer (KTB). Unlike the other pure forms of carbon (diamond and graphite), fullerenes are extractable in an organic solvent (e.g., toluene or 1,2,4-trichlorobenzene). The recognition of this unique property led to the detection and isolation of the higher fullerenes in the Kratschmer/Huffmann arc evaporated graphite soot and in the carbon material in the meteorite and impact deposits. By further exploiting the unique ability of the fullerene cage structure to encapsulate and retain noble gases, we have determined that both the Allende and Murchison fullerenes and the KTB fullerenes contain trapped noble gases with ratios that can only be described as extraterrestrial in origin.

Becker, Luann; Poreda, Robert J.; Bunch, Ted E.

2000-01-01

44

Noble gases in CH 4-rich gas fields, Alberta, Canada  

NASA Astrophysics Data System (ADS)

The elemental and isotopic compositions of helium, neon, argon, and xenon in twenty-one CH 4-rich natural gas samples from Cretaceous and Devonian reservoirs in the Alberta, Canada, sedimentary basin were measured. In all but a few cases, radiogenic ( 4He, 40Ar, and 131-136Xe) and nucleogenic ( 21,22Ne) isotopes dominated. Based solely on the noble gas composition, two types of natural gas reservoirs are identified. One (Group B) is highly enriched in radiogenic-nucleogenic noble gases and varies little in composition: 3He /4He = 1.5 0.5 10 -8, 40Ar /36Ar = 5000-6500 , 40?Ar /4He = 0.10 , 136?Xe /4He ~ 0.7 10 -9, and 21?Ne /22?Ne = 0.452 0.041 (? denotes radiogenic or nucleogenic origin; all 4He is radiogenic). High nitrogen content with 4He /N 2 ~ 0.06 is also characteristic of Group B samples. The remaining samples (Group A) contain a radiogenic-nucleogenic component with a different composition and, relative to Group B samples, the extent of enrichment in this component is less and more variable: 3He /4He = 10-70 10 -8, 40Ar /36Ar < 1550 , and 40?Ar /4He ~ 0.25 . The composition of Group B radiogenic-nucleogenic noble gases is consistent with production in crust of average composition. Enrichment in Group B noble gases and nitrogen increases with proximity to the underlying Precambrian basement, consistent with a present-day mass flux into the overlying sedimentary basin. Inferred 40?Ar /136?Xe 4He ratios imply a basement source enriched in thorium relative to uranium and potassium (Th/U > 20). Combined, the overall lower total radiogenic-nucleogenic content of Group A reservoirs, the greater variability in composition, and the appearance of Group A noble gases in reservoirs higher in the sedimentary sequence relative to the underlying basement implies that the Group A radiogenic-nucleogenic noble gases are indigenous to the sediments. The most interesting aspect of the Group A noble gases are the very high 3He /4He ratios; ~ 10-70 times greater than expected if derived from average crust. The mantle, surface cosmogenic 3He production, cosmic dust, or production in a lithium-enriched environment as potential sources for the 3He excesses are evaluated. The present data set would seem to rule out cosmogenic 3He. The mantle, cosmic dust, or high Li, however, remain viable candidates. The relative abundances of the nonradiogenic, non-nucleogenic noble gases show no correlation with the Group A-B reservoir classification. Compositional variations indicate three-component mixing between air or an air-like component, 10C air-saturated water, and a third component enriched in xenon. Apparently, the latter cannot be derived from equilibrium solubility degassing of air-saturated water or oil-water mixtures, and may have been derived from devolatilization of C-rich petroleum source sediments.

Hiyagon, H.; Kennedy, B. M.

1992-04-01

45

Recent Experimental Advances to Determine (noble) Gases in Waters  

NASA Astrophysics Data System (ADS)

In aquatic systems noble gases, radon, and bio-geochemically conservative transient trace gases (SF6, CFCs) are frequently applied to determine water residence times and to reconstruct past environmental and climatic conditions. Recent experimental breakthroughs now enable ? to apply the well-established concepts of terrestrial noble gas geochemistry in waters to the minute water amounts stored in sediment pore space and in fluid inclusions (A), ? to determine gas exchange processes on the bio-geochemical relevant time scales of minutes - hours (B), and ? to separate diffusive and advective gas transport in soil air (C). A. Noble-gas analysis in water samples (< 1 g) facilitates determining the solute transport in the pore space and identifying the origin of bio- and geogenic fluids in (un) consolidated sediments [1]. Advanced techniques that combine crushing and sieving speleothem samples in ultra-high-vacuum to a specific grain size allow to separate air and water-bearing fluid inclusions and thus enables noble-gas-based reconstruction of environmental conditions from water masses as small as 1mg [2]. B. The coupling of noble gas analysis with approaches of gas chromatography permits combined analysis of noble gases and other gases species (e.g., SF6, CFCs, O2, N2) from a single water sample. The new method substantially improves ground water dating by SF6 and CFCs as excess air is quantified from the same sample and hence can adequately be corrected for [3]. Portable membrane-inlet mass spectrometers enable the quasi-continuous and real-time analysis of noble gases and other dissolved gases directly in the field, allowing, for instance, quantification of O2 turnover rates on small time scales [4]. C. New technical developments perfect 222Rn analysis in water by the synchronous the determination of the short-lived 220Rn. The combined 220,222Rn analysis sheds light on the emanation behaviour of radon by identifying soil water content to be the crucial control of 220Rn occurrence in the environment, e.g., making an argument why 220Rn is not detectable in water, but in soil air. As 220Rn occurrence is of 'very local origin' the combined analysis of 220,222Rn in soil air allows differentiating between advective and diffusive soil gas transport [5]. By discussing these recent achievements, we intend to stimulate a broader discussion to identify future applications of noble and other gases in (un) conventional aquatic systems, such as blood. [1] Tomonaga et al. (2011) Limnol. Oceanogr. Methods, 9, 42-49, doi:10:4319/lom.2011.9.42. [2] Vogel et al. (2013) Geochem. Geophys. Geosyst., 14, doi:10.1002/ggge.20164. [3] Brennwald et al. (2013) Environ. Sci. Technol., Article ASAP, DOI: 10.1021/es401698p. [4] Mchler et al. (2012) Environ. Sci. Technol., 47, 7060-7066. [5] Huxol et al. Environ. Sci. Technol., in revision.

Kipfer, R.; Brennwald, M. S.; Huxol, S.; Mchler, L.; Maden, C.; Vogel, N.; Tomonaga, Y.

2013-12-01

46

Sorption of noble gases by solids, with reference to meteorites. II - Chromite and carbon. III - Sulfides, spinels, and other substances; on the origin of planetary gases  

NASA Astrophysics Data System (ADS)

The trapping of noble gases by chromite and carbon, two putative carriers of primordial noble gases in meteorites, was studied by synthesizing 19 samples in a Ne-Ar-Kr-Xe atmosphere at 440-720 K. Noble gas contents are found to approximately obey Henry's Law, but only slight correlations are found with composition, surface area, or adsorption temperature. Geometric mean distribution coefficients for bulk samples and HCl residues in 10 cu cm STP/g atm are: Xe 100, Kr 15, Ar 3.5, and Ne 0.62. Elemental fractionation data support the suggestion of Lewis et al. (1977) that chromite and carbon in C2 and C3 chondrites were formed by the reaction: Fe, Cr + 4CO yields (Fe, Cr)3O4 + 4C + carbides. In contrast to meteoritic minerals, the synthetic specimens show no isotopic fractionation of noble gases. In a subsequent study, attention is given to the cases of sulfides and spinels, on the way to consideration of the origin of planetary gases. Sulfides showed three distinctive trends relative to chromite or magnetite. The elemental fractionation pattern of Ar, Kr and Xe in meteorites, terrestrial rocks and planets resembles the adsorption patterns on the carbons, spinels, sulfides, and other solids studied. The high release temperature of meteoritic noble gases may be explained by transformation of the physisorbed or chemisorbed gas. The ready loss of meteoritic heavy gases on surficial oxidation is consistent with adsorption, as is the high abundance.

Yang, J.; Anders, E.

1982-06-01

47

Contraction of the positive column of discharges in noble gases  

NASA Astrophysics Data System (ADS)

This review describes the experimental studies of contraction in neon, argon and helium, discussing the basic regularities of the phenomenon. These studies, extended over a long time, are still urgent. For pressures that are not too high a noticeable contraction of the plasma glow and a smooth non-monotonic dependence of the degree of contraction on the current are observed. Above a critical pressure the plasma immediately contracts into a bright thin cord, if the current reaches a critical value. A hysteresis phenomenon is observed during the transition from the diffuse state to the contracted state and vice versa. Experiments that show the secondary role of non-homogeneous gas heating for contraction in neon and argon, and the main role for contraction in helium, are described. Studies of the ionization waves (the strata), which propagate as pulses of the current cord area, are reviewed showing the close relationship between contraction and stratification. The roles of various mechanisms leading to the contraction and describing the general picture of the observed phenomena are analysed. For heavy noble gases the main role is played by ionization non-linearity as a function of electron concentration, which is related to the competition of electron-atom and electron-electron collisions. This non-linearity leads to plasma shrinkage and the development of ionization instability in the radial (contraction) and longitudinal (stratification) directions. For helium such non-linearity does not play a leading role, since the frequency of the elastic electron-atom collisions is considered to be constant over a large energy range, and this yields a Maxwellian distribution function. The contraction in helium is defined by thermal effects. In addition, recent studies on the numerical modelling of the contraction are discussed.

Golubovskii, Yu B.; Nekuchaev, V.; Gorchakov, S.; Uhrlandt, D.

2011-10-01

48

Howardite Noble Gases as Indicators of Asteroid Surface Processing  

NASA Technical Reports Server (NTRS)

The HED (Howardite, Eucrite and Diogenite) group meteorites likely or iginate from the Asteroid 4 Vesta - one of two asteroid targets of NA SA's Dawn mission. Whilst Howardites are polymict breccias of eucriti c and diogenitic material that often contain "regolithic" petrologica l features, neither their exact regolithic nature nor their formation processes are well defined. As the Solar Wind (SW) noble gas compon ent is implanted onto surfaces of solar system bodies, noble gas anal yses of Howardites provides a key indicator of regolithic origin. In addition to SW, previous work by suggested that restricted Ni (300-12 00 micro g/g) and Al2O3 (8-9 wt%) contents may indicate an ancient we ll-mixed regolith. Our research combines petrological, compositional and noble gas analyses to help improve understanding of asteroid reg olith formation processes, which will play an intergral part in the i nterpretation of Dawn mission data. Following compositional and petrological analyses, we developed a regolith grading scheme for our sampl e set of 30 Howardites and polymict Eucrites. In order to test the r egolith indicators suggested by, our 8 selected samples exhibited a r ange of Ni, Al2O3 contents and regolithic grades. Noble gas analyses were performed using furnace stepheating on our MAP 215-50 noble gas mass spectrometer. Of our 8 howardites, only 3 showed evidence of SW noble gases (e.g approaching Ne-20/Ne-22 approximately equals 13.75, Ne-21/Ne-22 approximately equals 0.033). As these samples display low regolithic grades and a range of Ni and Al2O3 contents, so far we are unable to find any correlation between these indicators and "regolit hic" origin. These results have a number of implications for both Ho wardite and Vesta formation, and may suggest complex surface stratigr aphies and surface-gardening processes.

Cartwright, J. A.; Mittlefehldt, D. W.; Herrin, J. S.; Ott, U.

2011-01-01

49

Origin of the atmospheric noble gases in OIB and MORB  

NASA Astrophysics Data System (ADS)

In order to constrain the origin of atmospheric noble gases measured in glassy margins of pillow lava from both OIB and MORB, fresh glassy samples from pillow lavas erupted at 30-40 meters deep in 2004 and 2007 and sampled by a diver without seeing atmosphere at the Piton de la Fournaise volcano (Runion island) were analyzed. These samples were chosen because of the low depth of eruption implying that the magmatic noble gases were strongly degassed. Step crushing, using the same analytical procedure that typical MORB and OIB samples, was performed. The sample doesn't show any magmatic helium implying that magmatic gases were indeed degased. However, important quantities of rare gases with air-like elementary abundances and isotopic ratios are observed during step crushing. These results suggest that this atmospheric component was injected in the sample during or after eruption. Our preferred explanation for the presence of air-like components in MORB and OIB is the presence of seawater, and sometimes air when exposed for a long time in the laboratory, in some vesicles or cracks, that can be degased under vacuum but not fast enough to avoid contamination of the magmatic component during gas extraction after 24-48h in vacuum.

Moreira, M. A.

2011-12-01

50

Subduction of Seawater-Derived Noble Gases and Halogens: Evidence from Wedge Mantle Peridotite  

NASA Astrophysics Data System (ADS)

Subduction volcanism is generally considered to form a 'subduction barrier' that efficiently recycles volatile components contained in subducted slabs back to the Earth's surface (Staudacher and Allegre, 1988). Nevertheless, subduction of sediment and seawater-dominated pore fluids to the deep mantle has recently been proposed to account for the convecting mantle heavy noble gas (Ar, Kr and Xe) non-radiogenic elemental abundance and isotopic pattern (Holland and Ballentine, 2006). To verify whether and how subduction fluids preserve a seawater signature, we have determined noble gas and halogen compositions of the Higashi-akaishi peridotite body in the Sanbagawa metamorphic belt, southwest Japan, in which former water-rich inclusions exhumed from depths greater than 100 km are contained as serpentine dominated micro-inclusions (Mizukami et al., 2004). The striking similarities of the observed noble gas and halogen compositions with marine pore fluids challenge a popular concept, in which the water flux into the wedge mantle is only by hydrous minerals in altered oceanic crust and sediment (e.g., Schmidt and Poli, 1998). Subduction and closed system retention of unbound marine pore fluid to at least 100 km depth is required. The subducted halogen and noble gas elemental ratios are clearly distinct from those of arc volcanic gases. This implies that the Higashi-akaishi peridotite body has frozen in and preserved an inferred but previously unseen part of the volatile recycling process. Return of these volatiles to the atmosphere via arc volcanism requires the addition of a mantle component and fractionation during degassing. A small proportion preserved in the downgoing slab can explain the heavy noble gases observed in the convecting mantle. References: Holland G. and Ballentine C. J., Nature, 441, 186-191 (2006). Mizukami T. et al., Nature, 427, 432-436 (2004). Schmidt M.W. and Poli S., Earth Planet. Sci. Lett., 163, 361-379 (1998). Staudacher, T. and Allegre C.J., Earth Planet. Sci. Lett., 89, 173-183 (1988).

Sumino, H.; Ballentine, C. J.; Burgess, R.; Holland, G.; Mizukami, T.; Wallis, S. R.

2008-12-01

51

Noble gases of the Yamato 000027 and Yamato 000097 lherzolitic shergottites from Mars  

NASA Astrophysics Data System (ADS)

We used total melting and stepwise heating methods to measure noble gases within bulk samples from Yamato 000027 and Yamato 000097 lherzolites as well as a melt-vein sample from Yamato 000027. He and Ne are dominated by cosmogenic noble gases. The obtained cosmic-ray exposure age of 4.6 1.5 Ma, an average age based on cosmogenic 3He, 21Ne, and 38Ar for these samples, is consistent with the ages of other lherzolitic shergottites, indicating a common impact event for the ejection of lherzolites from Mars. Heavy noble gases released from the bulk samples at low temperatures were elementally fractionated terrestrial atmosphere. Martian noble-gas isotopic signatures, 40Ar/ 36Ar = 1900 and 129Xe/ 132Xe = 1.3, were observed at high temperatures (>1000 C). The melt-vein sample released greater amounts of atmospheric Ar, Kr, and Xe at low temperatures than the bulk samples. Large amounts of Ar and Kr, as well as excess 40Ar and 129Xe, were evolved from the melt-vein sample at 1400 C, and the gas shows very high 36Ar/ 132Xe (=3100) and 84Kr/ 132Xe (=76) values. Maximum 40Ar/ 36Ar and 129Xe/ 132Xe values of the melt sample were 1100 and 1.6, respectively, at 1600 C. Cosmogenic Kr shows an absence of 80Kr and 82Kr produced by neutron capture on Br, which suggests a small pre-atmospheric body. Overall noble gas compositions for Y000027 and Y000097 support pairing for the Yamato 00 shergottites.

Nagao, Keisuke; Park, Jisun; Choi, Hoon Gong

52

Effect of Noble Gases on Sonoluminescence Temperatures during Multibubble Cavitation  

SciTech Connect

Sonoluminescence spectra were collected from Cr(CO){sub 6} solutions in octanol and dodecane saturated with various noble gases. The emission from excited-state metal atoms serves as an internal thermometer of cavitation. The intensity and temperature of sonoluminescence increases from He to Xe. The intensity of the underlying continuum, however, grows faster with increasing temperature than the line emission. Dissociation of solvent molecules within the bubble consumes a significant fraction of the energy generated by the collapsing bubble, which can limit the final temperature inside the bubble. (c) 2000 The American Physical Society.

Didenko, Yuri T.; McNamara, William B. III; Suslick, Kenneth S.

2000-01-24

53

Noble Gases in Several New Chondrite Falls and Finds  

NASA Astrophysics Data System (ADS)

Noble gases in chondrites are a mixture of different components that contain information on past "geological" events of the meteoritic material on their parent bodies and also on the irradiation and thermal history of the meteoroid. Furthermore, together with the mineralogical-petrographical record, the noble gases yield hints on the question of possible pairing of specimens. Seventeen different ordinary chondrites have been investigated. Results are given in Table 1. Twelve of these chondrites--marked with an asterisk--fell or have been recognized as meteorites during the last seven years. As shown by the presence of solar gases, two chondrites are regolithic breccias (Noblesville and Chiang Khan). Our analyses of Chiang Khan are different from that given by Eugster et al. (1990). It is possible that two different meteorites are known under this name. Glanerbrug, although a brecciated chondrite, does not contain solar gases. The Dunedin is a "museum-find." In 1987 it was proposed as a new meteorite (Sipiera et al., 1987). The noble gas record of Dunedin is different from that of all other yet measured LL3 and LL4 chondrites (Schultz and Kruse, 1989). Thus, these measurements do not contradict the suggestion of a distinct meteorite. A ^3He/^21Ne <1 is observed in Gilzem indicating a deficit of ^3He. This meteorite is not paired with the H5-shower of Simmern that fell in 1920 at a distance of about 40 km from Gilzem. Also the L-chondrites Pampa (a), (b), and (c) (R. Wieler, priv. communication) do not belong to the same fall. The ^3He/^21Ne-- and ^22Ne/^21Ne--ratios of individual fragments of the Kokubunji shower follow the trend-lines of the "Bern-plot." References: Eugster O., Michel Th., and Wang D. (1990) Lunar Planet. Sci. XXI, 339. Sipiera P.P., Brooks R.R. Johnston J.H., Holzbecher J., and Ryan D.E. (1987) Chem. Geol. 64, 351. Schultz L. and Kruse H. (1989) Meteoritics 24, 155. Table 1, which in the hard copy appears here, shows noble gas concetrations of the 17 ordinary chondrites under investigation.

Loeken, T.; Scherer, P.; Weber, H. W.; Schultz, L.

1992-07-01

54

Noble gases, K, U, Th, and Pb in native gold  

NASA Astrophysics Data System (ADS)

We present determinations of the noble gas and Pb isotopic abundances and of K, Th, and U concentrations of native gold. Our results demonstrate that gold is an excellent carrier for crustal volatiles, but direct dating of gold using the U, Th-4He, 40K-40Ar, and U fission Xe methods was not successful for various reasons. The main significance of this work is the great sensitivity of gold for trapped gases as well as for gases that were produced in situ which gives the prospects of using gold and its fluid and solid inclusions for the study of paleogas composition. Numerous nuclear effects characterize the noble gas inventory of placer gold from Switzerland and Italy, vein gold from Italy, South Africa, and Venezuela, and lode gold from South Africa. The degassing patterns obtained by mass spectrometry show a low-temperature release of volatiles around 500C from fluid inclusions mainly in vein gold and a high-temperature release from solid inclusions and the gold itself. The low-temperature volatiles represent species that were trapped when the gold crystallized. We investigated the following trapped species: the isotopes of He, Ne, Ar, Kr, Xe, and Pb, and the abundances of K, U, Th, H2O, and CO2. The crustal gases trapped by gold comprise 3He from 6Li(n,?)3H ? ?- ? 3He, 4He and 40Ar from the U, Th, and K decay, and Xe from 238U fission. We observe 4He/40Ar = 3.9 for the radiogenic trapped gases of tertiary gold and a ratio of 1.4 for Archean gold. These ratios are consistent with the production ratios from U and K at the respective times and demonstrate that gold can be used as a sampler of ancient atmospheric gases. The concentrations of U and Th range from a few parts per billion to a few parts per million, and those of K and Pb range up to some tens of parts per million. The antiquity of trapped Pb is indicated by the Pb-Pb model age of about 3000 Ma for the lead extracted from vein gold and quartz of the Lily gold mine (South Africa). Gold also contains noble gases produced in situ by U, Th, and K decay. We obtained 4He up to the extremely high concentration of 6.810-2 cm3 STP/g (STP: atmospheric pressure and 0C) for gold separated from a specimen of the Witwatersrand West Rand gold fields, indicating that this gold has a large U content.

Engster, O.; Niedermann, S.; Thalmann, C.; Frei, R.; Kramers, J.; KrHenbhl, U.; Liu, Y. Z.; Hofmann, B.; Boer, R. H.; Reimold, W. U.; Bruno, L.

1995-12-01

55

The origin of air-like noble gases in MORB and OIB  

Microsoft Academic Search

Interpretation of the noble gas (Ne, Ar, Kr and Xe) isotopic composition of Ocean Island and Mid Ocean Ridge basalt (OIB and MORB) glass is complicated by the near surface addition of atmosphere-derived noble gases. Although the noble gas elemental composition in these samples is often similar to modern air, equilibration between a seawater vapor phase and a basalt melt

Chris J. Ballentine; Dan N. Barfod

2000-01-01

56

Enhancement of Surface NMR by Laser-Polarized Noble Gases  

NASA Astrophysics Data System (ADS)

The transfer of polarization was recently demonstrated between laser polarized ^129Xe in solution and the spins of the solvent, liquid benzene (Science 271, 1848 (1996)). Here we will describe new experiments on transfer of spin polarization from laser-polarized ^3He and ^129Xe to ^1H and ^13C spins on the surfaces of solids (Aerosil) at T=4 K to 200 K. The transfer mechanism is dipole-dipole cross relaxation between the spins of the adsorbed mobile noble gas and the surface spins (Spin Polarization Induced Nuclear Overhauser Effect). The enhancement of surface ^1H magnetization by ^3He at 4 K and 10 K is between one and twofold. Using ^129Xe, enhancement factors of up to twenty were obtained when compared to the Boltzmann polarization (B_0=4.2 T, T=130 K). The SPINOE is an alternative transfer of spin polarization from laser-polarized gases to surface spins with no requirement for Hartmann-Hahn matching or zero field mixing. Solidification of the noble gases is not required and consequently the SPINOE can be carried out in a continuous flow mode and over a broader temperature range. Continous flow would allow signal accumulation and therefore the exploration of surfaces with fewer spins or long relaxation times, as well as SPINOE under MAS.

Room, T.; Appelt, S.; Seydoux, R.; Pines, A.; Hahn, E. L.

1997-03-01

57

Solar composition noble gases in the Washington County iron meteorite  

NASA Technical Reports Server (NTRS)

A sample of the Washington County iron meteorite is analyzed for its light noble gases by a combustion technique in two steps at 1160 C. The ratio of trapped to spallogenic noble gases in the sample was high enough to allow the resolution of trapped and spallogenic components in both combustion steps. The He:Ne:Ar elemental ratios in the trapped component are comparable to present-day solar-wind ratios. The (Ne-20)/(Ne-22) ratio, while subject to some uncertainty due to possible variation in either the spallation or the trapped component between the two steps, is in the range 13.3 + or 0.5, also comparable to present-day solar wind. Unless the Washington County iron formed by some unique process in a solar-wind-irradiated regolith, the fact that the trapped gas is of solar composition has implications with regard to the compositional history of the solar wind, to conditions in the early solar nebula during grain formation or accretion, and to primordial helium in the earth.

Becker, R. H.; Pepin, R. O.

1984-01-01

58

Solubilities of noble gases in magnetite - Implications for planetary gases in meteorites.  

NASA Technical Reports Server (NTRS)

Solubilities of noble gases in magnetite were determined by growing magnetite in a noble-gas atmosphere between 450 and 700 K. Henry's law is obeyed at pressures up to .01 atm for He, Ne, Ar and up to .00001 atm for Kr, Xe, with the following distribution coefficients at 500 K: He 0.042, Ne 0.016, Ar 3.6, Kr 1.3, Xe 0.88, some 100 to 100,000 times higher than previous determinations on silicate and fluoride melts. Apparent heats of solution are in sharp contrast with earlier determinations on melts which were small and positive, but are comparable to the values for clathrates. Presumably the gases are held in anion vacancies.

Lancet, M. S.; Anders, E.

1973-01-01

59

Insights into deep carbon derived from noble gases  

NASA Astrophysics Data System (ADS)

Science and society are faced with two challenges that are inextricably linked: fossil-fuel energy dependence and rising levels of atmospheric carbon dioxide. Management of remaining hydrocarbon resources, the search for cleaner fuels and increasing interest in subsurface carbon storage all require a better understanding of the deep terrestrial carbon cycle. The coupling of noble gas and carbon chemistry provides an innovative approach to understanding this deep carbon. Whereas carbon geochemistry and isotopic signatures record the history of inorganic and organic reactions that control carbon mobility, the inert noble gases provide unique tracers of fluid origin, transport and age. Together, they have been used to show that groundwater has a key role as both the sink for geologically sequestered carbon dioxide, and in the transport and emplacement of hydrocarbon gas deposits. Furthermore, these tracers have also been used to show that groundwater and subsurface microbiology jointly influence the formation and alteration of fossil-fuel deposits to an extent not previously recognized. The age and distribution of groundwater in fractures in the Earth's crust exert important controls on the Earth's deepest microbial communities.

Lollar, B. Sherwood; Ballentine, C. J.

2009-08-01

60

Noble gases and cosmogenic radionuclides in the Eltanin Pacific meteorite  

SciTech Connect

A 1.5 cm long, 1.2 g specimen of the Eltanin meteorite was found at 10.97 m depth in Polarstern piston core PS2704-1. The early studies indicated that the small fragments of the Eltanin meteorite was debris from a km-sized asteroid which impacted into the deep-ocean basin. In this study, the authors measured {sup 39}Ar-{sup 40}Ar age, noble gases, and cosmogenic radionuclides in splits of specimen as a part of consortium studies of Eltanin meteorite. They concluded that the specimen was about 3 m deep from the asteroid surface. The exposure age of the Eltanin asteroid was about 20 Myr.

Bogard, D D; Garrison, D H; Caffee, M W; Kyte, F; Nishiizumi, K

2000-01-14

61

Noble gases in a new meteorite, the Omolon pallasite  

NASA Astrophysics Data System (ADS)

The Omolon meteorite was observed to reach the earth's surface in May 1981 over a large area of the Magadan region, USSR; samples of the pallasite were collected in 1982 near the Omolon river, 64 deg 01 min N, 161 deg 48 min E. The objective of the study was to investigate the isotope composition and noble gas concentration of olivine from the Omolon pallasite in order to identify various genetic components of the gases, estimate the radiation age of the meteorite, and determine the time of olivine crystallization. Data on the isotope composition and contents of He, Ne, Ar, Kr, and Xe are presented, and some characteristic features of the isotope composition are discussed. The radiation age of the pallasite is estimated at 94 +/- 18 million years.

Shukoliukov, Iu. A.; Klimenko, Iu. V.; Koliasnikov, Iu. A.; Petaev, M. I.

62

Highly Concentrated Nebular Noble Gases in Porous Nanocarbon Separates from the Saratov (L4) Meteorite  

NASA Astrophysics Data System (ADS)

The majority of heavy noble gases (Ar, Kr, and Xe) in primitive meteorites are stored in a poorly understood phase called Q. Although Q is thought to be carbonaceous, the full identity of the phase has remained elusive for almost four decades. In order to better characterize phase Q and, in turn, the early solar nebula, we separated carbon-rich fractions from the Saratov (L4) meteorite. We chose this meteorite because Q is most resistant in thermal alteration among carbonaceous noble gas carriers in meteorites and we hoped that, in this highly metamorphosed meteorite, Q would be present but not diamond: these two phases are very difficult to separate from each other. One of the fractions, AJ, has the highest 132Xe concentration of 2.1 10-6 cm3 STP g-1, exceeding any Q-rich fractions that have yet been analyzed. Transmission electron microscopy studies of the fraction AJ and a less Q-rich fraction AI indicate that they both are primarily porous carbon that consists of domains with short-range graphene orders, with variable packing in three dimensions, but no long-range graphitic order. The relative abundance of Xe and C atoms (6:109) in the separates indicates that individual noble gas atoms are associated with only a minor component of the porous carbon, possibly one or more specific arrangements of the nanoparticulate graphene.

Amari, Sachiko; Matsuda, Jun-ichi; Stroud, Rhonda M.; Chisholm, Matthew F.

2013-11-01

63

Underground Nuclear Explosions and Release of Radioactive Noble Gases  

NASA Astrophysics Data System (ADS)

Over a period in 1961-1990 496 underground nuclear tests and explosions of different purpose and in different rocks were conducted in the Soviet Union at Semipalatinsk and anovaya Zemlya Test Sites. A total of 340 underground nuclear tests were conducted at the Semipalatinsk Test Site. One hundred seventy-nine explosions (52.6%) among them were classified as these of complete containment, 145 explosions (42.6%) as explosions with weak release of radioactive noble gases (RNG), 12 explosions (3.5%) as explosions with nonstandard radiation situation, and four excavation explosions with ground ejection (1.1%). Thirty-nine nuclear tests had been conducted at the Novaya Zemlya Test Site; six of them - in shafts. In 14 tests (36%) there were no RNG release. Twenty-three tests have been accompanied by RNG release into the atmosphere without sedimental contamination. Nonstandard radiation situation occurred in two tests. In incomplete containment explosions both early-time RNG release (up to ~1 h) and late-time release from 1 to 28 h after the explosion were observed. Sometimes gas release took place for several days, and it occurred either through tunnel portal or epicentral zone, depending on atmospheric air temperature.

Dubasov, Yuri V.

2010-05-01

64

Mantle-derived noble gases in natural gases from Songliao Basin, China  

SciTech Connect

Abundances and isotopic compositions of noble gases have been measured in six natural gas samples (CO{sub 2} and CH{sub 4}-rich) from the Songliao Basin, Jilin Province, in northeastern China. The samples contain noble gases of mantle origin. The {sup 3}He/{sup 4}He ratio reaches 5.0 times the atmospheric ratio. In a three-isotope plot of neon, the {sup 20}Ne/{sup 22}Ne (up to 10.9) and {sup 21}Ne/{sup 22}Ne (up to 0.051) ratios make a positive correlation array together with natural gases from other continental areas. Compared with a correlation band for MORB, the natural gases from other continental areas. Compared with a correlation band for MORB, the natural gases have a lower slope with more nucleogenic {sup 21}Ne. The natural gas samples contain radiogenic argon with {sup 40}Ar/{sup 36}Ar ratios up to 7700. A positive correlation between {sup 40}Ar/{sup 36}Ar and nuclear reaction like {sup 35}Cl ({alpha}, p) {sup 38}Ar. Apparent excesses of {sup 129}Xe, {sup 132-136}Xe are recognized in four samples. The excess of {sup 129}Xe (up to 3%) can be attributed to a decay of extinct {sup 129}I. Excess {sup 132-136}Xe is not large enough to determine if the origin of the excess is {sup 238}U or {sup 244}Pu. Anomaly in {sup 129}Xe/{sup 130}Xe ratio is correlated with that of {sup 136}Xe/{sup 130}Xe. The isotopic features of the natural gases with radiogenic {sup 4}He and nucleogenic {sup 21}Ne can be produced within the crust. However, a natural gas from another basin in eastern China with a different reservoir age contains mantle derived neon which falls on the neon correlation line formed by the samples from the Songliao Basin. This consistency suggests that the isotopic features of the natural gases aren`t necessarily ascribable to surface contamination of radiogenic and nucleogenic isotopes. 58 refs., 6 figs., 1 tab.

Xu, Sheng; Nakai, Shun`ichi; Wakita, Hiroshi [Univ. of Tokyo, Bunkyo-ku (Japan)] [and others] [Univ. of Tokyo, Bunkyo-ku (Japan); and others

1995-12-31

65

No Evidence for Trapped Noble Gases in CAIs  

NASA Astrophysics Data System (ADS)

Refractory inclusions (CAIs) in meteorites probably are the first solids in the solar system. Although formed at high temperatures, CAIs are reported to contain trapped noble gases [1,2,3] which would provide information on CAI formation and solar system evolution. We reassessed this question by measuring Ne and Ar in CAIs of primitive chondrites (Allende, Axtell, Efremovka) by IR-laser extraction suitable for measuring low gas concentrations [4]. We chose meteorites with different preatmospheric radii, exposure ages, and degrees of alteration to take into account those effects on CAI noble gas compositions. 20Ne/22Ne is below 0.9 indicating the absence of common trapped Ne. We suggest that elevated 20Ne/22Ne of [1,2,5] resulted from contamination of their CAI samples with matrix rich in trapped Ne. 21Ne/22Ne is 0.72 to 0.86; more altered CAIs show the lower ratios. The Ne might be a mixture of chondritic cosmogenic Ne and nearly pure 22Ne, e.g., from presolar SiC [3]. However, calculated cosmogenic Ne for CAI minerals perfectly mimics the observed trend; in particular Na-rich alteration phases shift the 21Ne/22Ne to lower values. 36Ar/38Ar is 0.7 to 4.8, thereby more altered CAIs have higher ratios. The Ar might be a mixture of chondritic cosmogenic Ar (mainly produced from Ca) and trapped Ar [3] or solar wind Ar [2], the latter supporting CAI formation in an X-wind scenario [6]. However, due to high Cl concentrations in CAIs also nearly monoisotopic 36Ar produced cosmogenically by neutron capture and beta- decay on Cl must be taken into account. Modelling Ar ratios and concentrations using only cosmogenic Ar from Ca and Cl nicely match the measured data. Thereby more Cl-rich altered CAIs show higher 36Ar/38Ar. Although the data do not principally contradict the presence of trapped Ne or Ar in CAIs they can be straightforwardly explained by cosmogenic productions mainly from Na, Ca, and Cl. {[1]} Smith et al. (1977) GCA, 41, 627-647; [2] Shukolyukov et al. (2001) Geochem. Int., 39(1), 110-125; [3] Russel et al. (1998) MAPS, 33, A132; [4] Vogel (2003) PhD-Thesis, ETH Zuerich, Switzerland; [5] Goebel et al. (1982) GCA, 46, 1777-1792; [6] Shu et al. (1997) Science, 277, 1475-1479.

Vogel, N.; Baur, H.; Leya, I.; Wieler, R.

2003-12-01

66

Mantle-derived noble gases in natural gases from Songliao Basin, China  

NASA Astrophysics Data System (ADS)

Abundances and isotopic compositions of noble gases have been measured in six natural gas samples (CO 2 and CH 4-rich) from the Songliao Basin, Jilin Province, in northeastern China. The samples contain noble gases of mantle origin. The 3He/4He ratio reaches 5.0 times the atmospheric ratio. In a three-isotope plot of neon, the 20Ne/22Ne (up to 10.9) and 21Ne/22Ne (up to 0.051) ratios make a positive correlation array together with natural gases from other continental areas. Compared with a correlation band for MORB, the natural gases have a lower slope with more nucleogenic 21Ne. The natural gas samples contain radiogenic argon with 40Ar/36Ar ratios up to 7700. A positive correlation between 40Ar/36Ar and 20Ne/22Ne ratios indicates occurrence of mantle-derived Ar. Slight excess of 38Ar can be attributed to a nuclear reaction like 35C1 (?, p) 38 Ar. Apparent excesses of 1292'Xe, 132-136Xe are recognized in four samples. The excess of 129Xe (up to 3%) can be attributed to a decay of extinct 129I. Excess 132-136Xe is not large enough to determine if the origin of the excess is 238U or 244Pu. Anomaly in 129Xe/130Xe ratio is correlated with that of 136Xe/130Xe. The isotopic features of the natural gases with radiogenic 4He and nucleogenic 21Ne can be produced within the crust. Alternatively, they may reflect the geochemical features of the subcontinental mantle which has been enriched in U, Th. We can not distinguish the two possibilities. However, a natural gas from another basin in eastern China with a different reservoir age contains mantle derived neon which falls on the neon correlation line formed by the samples from the Songliao Basin. This consistency suggests that the isotopic features of the natural gases aren't necessarily ascribable to surface contamination of radiogenic and nucleogenic isotopes.

Xu, Sheng; Nakai, Shun'ichi; Wakita, Hiroshi; Wang, Xianbin

1995-11-01

67

Biomedical Magnetic Resonance Imaging and Spectroscopy with Laser Polarized Noble Gases  

NASA Astrophysics Data System (ADS)

In the past year, a great deal of attention has been drawn to the use of laser polarized noble gases to produce magnetic resonance images of rodent and human lungs. Initial demonstrations proved the principle that air space images can be produced with noble gases polarized to several percent. (The noble gas density is thousands of times smaller, but the noble gas polarization is thousands of times greater than the proton polarization of order 10-5 at 2 Tesla.) The manifold motivations include improvement of pulmonary and circulatory diagnostic radiology techniques as well as study of physiological function including neurological response. We have undertaken a program of development and application of MR imaging and spectroscopy using laser polarized gases with several goals including development of techniques and technologies to facilitate research and eventual medical applications. This talk will describe this multi-disciplinary program combining laser and optical physics, magnetic resonance tomography, neurophysiology and medical science.

Welsh, R. C.; Rosen, M. S.; Coulter, K. P.; Chupp, T. E.; Swanson, S. D.; Agranoff, B. W.; Prince, M. R.

1996-05-01

68

Elementary and isotopic compositions of noble gases in geothermal fluids of Tuscany, Italy  

Microsoft Academic Search

Analyses were made of the major gases, as well as helium and radon, in fluids from more than 90 geothermal wells in Tuscany. The elementary and isotopic abundances of the noble gases were determined by multiple samplings in seven wells. The results show good correlations between constituents of atmospheric origin and those of deep origin, suggesting the existence of a

S NUTI

1984-01-01

69

Modification of the Light Noble Gases From Genesis Aluminum Collectors  

NASA Astrophysics Data System (ADS)

The Genesis mission returned samples of solar wind (SW) collected over 2 years at the L1 point for earth- based laboratory measurements. The main goal of the mission is to obtain accurate, high precision isotopic measurements of trace elements in the SW. Since there are several processes and effects that can alter the laboratory measured value from the true SW value, it is worth trying to quantify these effects. We have been doing that by looking at the light noble gases: helium, neon, and argon, but these results will have implications for other elements as well. First, isotopic fractionation can occur if the processes which accelerate the SW away from the sun are mass- dependent. It has been uncertain how large this effect might be. In an effort to quantify this effect, Genesis collected samples of SW from different flow regimes (slow, fast, CME). Our measurements of these different regimes have tightly constrained the possible isotopic fractionation of neon and argon. Second, there are implantation effects. It is known that implantation at constant velocity results in mass fractionation with depth. Heavier isotopes have higher energy, and thus a larger range. The effect of this is that if all of the gas is not recovered during the measurement, the measured isotopic ratios will be altered from their source values. Surface erosion (such as surface damage of Genesis collectors and sputtering of lunar regolithic material) will make the measured ratios heavier than the source, while incomplete degassing of the sample will make the measured ratios lighter. And third, thermally activated diffusion can alter the initial depth profiles and cause losses of shallowly implanted species, both of which cause preferential loss of the light isotopes. We are currently working on a diffusion experiment to determine the diffusion parameters of the Genesis collector materials and to quantify the changes in the measured ratios from diffusive losses. We maintained individual pieces of two different Genesis collectors, polished aluminum and aluminum on sapphire (AloS), at six different temperatures between 160 C and 360 C for 322 days. And now we are performing step-wise heating on the samples. Helium and neon are measured together in one mass spectrometer, and Ar is cryogenically separated from them and measured in a second mass spectrometer. Preliminary results show higher variation in 3He/4He than 20Ne/22Ne and little variation in 36Ar/38Ar, as expected.

Mabry, J. C.; Meshik, A. M.; Hohenberg, C. M.; Burnett, D. S.

2008-12-01

70

Methane activation using noble gases in a dielectric barrier discharge reactor  

NASA Astrophysics Data System (ADS)

The conversion of methane is measured in a planar-type dielectric barrier discharge reactor using three different noble gases--He, Ne, and Ar--as additives. The empirical results obtained clearly indicate that methane activation is considerably affected by thy type of noble gas used. Through 0-D calculations, the discharge parameters inside the reactor, i.e., electron temperature and electron density, are estimated using experiment results. A comparison of the discharge characteristics and experimental results shows that the electron temperature is an important factor in achieving high methane activation and the mixture with Ar gas shows the highest methane conversion. These results are constructed using the mechanisms of energy and charge transfer from excited and ionized noble gas atoms to methane molecules, considering the number density of active atoms of noble gases. Finally, electron temperatures obtained for gas mixtures having different reactant compositions and concentrations are analyzed to estimate methane activation.

Jo, Sungkwon; Hoon Lee, Dae; Seok Kang, Woo; Song, Young-Hoon

2013-08-01

71

Methane activation using noble gases in a dielectric barrier discharge reactor  

SciTech Connect

The conversion of methane is measured in a planar-type dielectric barrier discharge reactor using three different noble gasesHe, Ne, and Aras additives. The empirical results obtained clearly indicate that methane activation is considerably affected by thy type of noble gas used. Through 0-D calculations, the discharge parameters inside the reactor, i.e., electron temperature and electron density, are estimated using experiment results. A comparison of the discharge characteristics and experimental results shows that the electron temperature is an important factor in achieving high methane activation and the mixture with Ar gas shows the highest methane conversion. These results are constructed using the mechanisms of energy and charge transfer from excited and ionized noble gas atoms to methane molecules, considering the number density of active atoms of noble gases. Finally, electron temperatures obtained for gas mixtures having different reactant compositions and concentrations are analyzed to estimate methane activation.

Jo, Sungkwon; Hoon Lee, Dae; Seok Kang, Woo; Song, Young-Hoon [Korea Institute of Machinery and Materials, 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of)] [Korea Institute of Machinery and Materials, 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of)

2013-08-15

72

Method and apparatus for measuring purity of noble gases  

DOEpatents

A device for detecting impurities in a noble gas includes a detection chamber and a source of pulsed ultraviolet light. The pulse of the ultraviolet light is transferred into the detection chamber and onto a photocathode, thereby emitting a cloud of free electrons into the noble gas within the detection chamber. The cloud of electrons is attracted to the opposite end of the detection chamber by a high positive voltage potential at that end and focused onto a sensing anode. If there are impurities in the noble gas, some or all of the electrons within the cloud will bond with the impurity molecules and not reach the sensing anode. Therefore, measuring a lower signal at the sensing anode indicates a higher level of impurities while sensing a higher signal indicates fewer impurities. Impurities in the range of one part per billion can be measured by this device.

Austin, Robert (Largo, FL)

2008-04-01

73

Noble gases in CH 4 -rich gas fields, Alberta, Canada  

Microsoft Academic Search

The elemental and isotopic compositions of helium, neon, argon, and xenon in twenty-one CH 4 -rich natural gas samples from Cretaceous and Devonian reservoirs in the Alberta, Canada, sedimentary basin were measured. In all but a few cases, radiogenic ( 4 He, 40 Ar, and 131-136 Xe) and nucleogenic ( 21,22 Ne) isotopes dominated. Based solely on the noble gas

H. Hiyagon; B. M. Kennedy

1992-01-01

74

Carbynes: carriers of primordial noble gases in meteorites  

Microsoft Academic Search

Five carbynes (triply bonded allotropes of carbon) have been found by electron diffraction in the Allende and Murchison carbonaceous chondrites: carbon VI, VIII, X, XI, and (tentatively) XII. From the isotopic composition of the associated noble-gas components, it appears that the carbynes in Allende (C3V chondrite) are local condensates from the solar nebula, whereas at least two carbynes in Murchison

A. G. Whittaker; E. J. Watts; R. S. Lewis; E. Anders

1980-01-01

75

Primordial noble gases in separated meteoritic minerals--I  

Microsoft Academic Search

Magnetite and a layer-lattice silicate from the Orgueil carbonaceous chondrite show strikingly different noble gas patterns. Magnetite contains He, Ne and Ar in essentially solar proportions, with some excess Kr and Xe. Isotopic ratios are typically solar: Ne 20 \\/ Ne 22 = 12.5, He 3 \\/ He 4 = (3.8 0.4) 10 -4 ; but Xe 129

Peter M. Jeffery; Edward Anders

1970-01-01

76

Insights into deep carbon derived from noble gases  

Microsoft Academic Search

Science and society are faced with two challenges that are inextricably linked: fossil-fuel energy dependence and rising levels of atmospheric carbon dioxide. Management of remaining hydrocarbon resources, the search for cleaner fuels and increasing interest in subsurface carbon storage all require a better understanding of the deep terrestrial carbon cycle. The coupling of noble gas and carbon chemistry provides an

B. Sherwood Lollar; C. J. Ballentine

2009-01-01

77

Noble gases in CH sub 4 -rich gas fields, Alberta, Canada  

SciTech Connect

The elemental and isotopic compositions of helium, neon, argon, and xenon in twenty-one CH{sub 4}-rich natural gas samples from Cretaceous and Devonian reservoirs in the Alberta, Canada, sedimentary basin were measured. In all but a few cases, radiogenic ({sup 4}He, {sup 40}Ar, and {sup 131-136}Xe) and nucleogenic ({sup 21,22}Ne) isotopes dominated. Based solely on the noble gas composition, two types of natural gas reservoirs are identified. One (Group B) is highly enriched in radiogenic-nucleogenic noble gases and varies little in composition. High nitrogen content with {sup 4}He/N{sub 2} {approximately} 0.06 is also characteristic of Group B samples. The remaining samples (Group A) contain a radiogenic-nucleogenic component with a different composition and, relative to Group B samples, the extent of enrichment in this component is less and more variable. The composition of Group B radiogenic-nucleogenic noble gases is consistent with production in crust of average composition. Combined, the overall lower total radiogenic-nucleogenic content of Group A reservoirs, the greater variability in composition, and the appearance of Group A noble gases in reservoirs higher in the sedimentary sequence relative to the underlying basement implies that the Group A radiogenic-nucleogenic noble gases are indigenous to the sediments. The relative abundances of the nonradiogenic, non-nucleogenic noble gases show no correlation with the Group A-B reservoir classification. Compositional variations indicate three-component mixing between air or an air-like component, 10C air-saturated water, and a third component enriched in xenon. Apparently, the latter cannot be derived from equilibrium solubility degassing of air-saturated water or oil-water mixtures, and may have been derived from devolatilization of C-rich petroleum source sediments.

Hiyagon, H.; Kennedy, B.M. (Univ. of California, Berkeley (United States))

1992-04-01

78

Noble gases and shock effects in the Odessa octahedrite  

NASA Technical Reports Server (NTRS)

Noble gas contents and shock effects have been studied in 21 Odessa irons from known geographic locations. Cosmogenic He-3, Ne-21, Ar-38 contents and He-3/Ne-21 ratios vary by factors of 62, 91, 68, and 1.55, respectively, while Ne-22/Ne-21 ratios are virtually constant at 1.07. The samples fall into two groups differing by a factor of 4.1 in exposure age, 1000 in source mass, or some combination of these. Three samples show significant shock effects, two of them to above 130 kbar, probably arising during terrestrial impact from the crater-forming explosion. As in Canyon Diablo plains specimens, noble gas contents do not correlate with siting or shock.

Herzog, G. F.; Lipschutz, M. E.; Jain, A. V.; Rodman, T. E.

1976-01-01

79

Trapped Solar Wind Noble Gases in APOLLO 12 Lunar Fines 12001 and APOLLO 11 Breccia 10046.  

National Technical Information Service (NTIS)

The concentrations and isotopic composition of the five noble gases were measured in an unseparated bulk sample of the Apollo 12 fines 12001, in seven bulk and five ilmenite grain size fractions from 12001, and in four ilmenite grain size fractions separa...

P. Eberhardt J. Geiss H. Graf N. Groegler M. D. Mendia

1972-01-01

80

Noble gas state of the ancient mantle as deduced from noble gases in coated diamonds  

NASA Astrophysics Data System (ADS)

Precise isotopic data on noble gas from diamonds are presented as well as a comparison of noble gas states of the present and the ancient mantle. Ne-20/Ne-22 ratios are found to fall in a narrow range, the average being 11.8 + or - 0.4. Ne-21/Ne-22 ratios show considerable variation, which is argued as being due to nucleogenic Ne-21 produced from O(alpha, n)-18 or from Mg(n, alpha)-24 essentially in the mantle. Ar-38/Ar-36 and Kr isotopic ratios are identical with the atmospheric ratios within 1 percent. Heavier Xe isotopes corrected for fission Xe derived either from Pu-244 or U-238 and Xe-128 are indistinguishable from atmospheric ratios. Xe-129 has a distinct excess (up to about 10 percent) relative to atmospheric Xe, which can be attributed to the extinct nuclide I-129.

Ozima, M.; Zashu, S.

1991-07-01

81

Carbynes - Carriers of primordial noble gases in meteorites  

NASA Technical Reports Server (NTRS)

Five carbynes (triply bonded allotropes of carbon) have been found by electron diffraction in the Allende and Murchison carbonaceous chondrites: carbon VI, VIII, X, XI, and (tentatively) XII. From the isotopic composition of the associated noble-gas components, it appears that the carbynes in Allende (C3V chondrite) are local condensates from the solar nebula, whereas at least two carbynes in Murchison (C2 chondrite) are of exotic, presolar origin. They may be dust grains that condensed in stellar envelopes and trapped isotropically anomalous matter from stellar nucleosynthesis.

Whittaker, A. G.; Watts, E. J.; Lewis, R. S.; Anders, E.

1980-01-01

82

Carbynes: carriers of primordial noble gases in meteorites  

SciTech Connect

Five carbynes (triply bonded allotropes of carbon) have been found by electron diffraction in the Allende and Murchison carbonaceous chondrites: carbon VI, VIII, X, XI, and (tentatively) XII. From the isotopic composition of the associated noble-gas components, it appears that the carbynes in Allende (C3V chondrite) are local condensates from the solar nebula, whereas at least two carbynes in Murchison (C2 chondrite) are of exotic, presolar origin. They may be dust gains that condensed in stellar envelopes and trapped isotopically anomalous matter from stellar nucleosynthesis.

Whittaker, A.G. (Aerospace Corp., El Segundo, CA); Watts, E.J.; Lewis, R.S.; Anders, E.

1980-09-26

83

The nature of pristine noble gases in mantle plumes  

PubMed

High-precision noble gas data show that the Hawaiian and Icelandic mantle plume sources contain uniquely primitive neon that is composed of moderately nucleogenic neon-21 and a primordial component indistinguishable from the meteoritic occurrence of solar neon. This suggests that Earth's solar-type rare gas inventory was acquired during accretion from small planetesimals previously irradiated by solar wind from the early sun. However, nonradiogenic argon, krypton, and xenon isotopes derived from the mantle display nonsolar compositions and indicate an atmosphere-like fingerprint that is not due to recent subduction. PMID:10807571

Trieloff; Kunz; Clague; Harrison; Allegre

2000-05-12

84

The record of cosmogenic, radiogenic, fissiogenic, and trapped noble gases in recently recovered Chinese and other chondrites  

NASA Astrophysics Data System (ADS)

Noble-gas isotopic abundances were determined in 36 recently recovered chondrites including 27 chondrites recovered in China. The comparison of the release patterns of trapped noble gases from ordinary and from carbonaceous chondrites showed that the planetary trapped noble gases in ordinary chondrites were released mainly above 1200 C, whereas more than 85 percent of noble gases trapped in carbonaceous chondrites were released at or below 1200 C, indicating that the carrier phases of the trapped noble gases in ordinary and in carbonaceous chondrites may not be the same. It is suggested that the ordinary chondrites started to retain fission Xe about 48 +/- 30 Ma earlier than Angra dos Reis. No systematic differences were observed between H, L, and LL or type 5 and 6 chondrites with respect to the time of fission Xe retention. Eight chondrites displayed neutron capture effects due to secondary cosmic-ray-produced neutrons.

Eugster, O.; Michel, Th.; Niedermann, S.; Wang, D.; Yi, W.

1993-03-01

85

Laser Induced Breakdown in High Pressure Noble Gases.  

National Technical Information Service (NTIS)

Laser induced breakdown is studied both experimentally and analytically in high pressure helium, neon, and argon gases. It is shown that an analysis based on balancing electron production against electron loss yields good agreement with experimental data ...

A. A. Dougal G. W. Haynes

1971-01-01

86

A generic biokinetic model for noble gases with application to radon.  

PubMed

To facilitate the estimation of radiation doses from intake of radionuclides, the International Commission on Radiological Protection (ICRP) publishes dose coefficients (dose per unit intake) based on reference biokinetic and dosimetric models. The ICRP generally has not provided biokinetic models or dose coefficients for intake of noble gases, but plans to provide such information for (222)Rn and other important radioisotopes of noble gases in a forthcoming series of reports on occupational intake of radionuclides (OIR). This paper proposes a generic biokinetic model framework for noble gases and develops parameter values for radon. The framework is tailored to applications in radiation protection and is consistent with a physiologically based biokinetic modelling scheme adopted for the OIR series. Parameter values for a noble gas are based largely on a blood flow model and physical laws governing transfer of a non-reactive and soluble gas between materials. Model predictions for radon are shown to be consistent with results of controlled studies of its biokinetics in human subjects. PMID:23612507

Leggett, Rich; Marsh, James; Gregoratto, Demetrio; Blanchardon, Eric

2013-06-01

87

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

NASA Technical Reports Server (NTRS)

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.; Scherer, P.; Schultz, L.

1993-01-01

88

A mass spectrometric system for the analysis of noble gases and tritium from water samples  

Microsoft Academic Search

The design, setup, and performance of a mass spectrometric system for the analysis of noble gas isotopes (³He, ⁴He, ²°Ne, ²¹Ne, ²²Ne, ³⁶Ar, ⁴°Ar, ⁸⁴Kr, ¹³⁶Xe) and tritium (³H) from water samples are described. The ³H concentration is measured indirectly by the ³He ingrowth from radioactive decay. After extraction, purification, and separation, the noble gases are measured in two noncommercial

Urs Beyerle; Werner Aeschbach-Hertig; Dieter M. Imboden; Heinrich Baur; Thomas Graf; Rolf Kipfer

2000-01-01

89

Measuring high-order Kerr effects of noble gases based on spectral analysis  

NASA Astrophysics Data System (ADS)

A method for measuring high-order Kerr effects of noble gases is proposed. It is based on analyzing spectral characteristics of the optical pulse after propagation through a hollow-core fiber which is filled with noble gas whose Kerr effects are to be measured. This method is further investigated through numerical experiments, and the retrieved Kerr refractive indexes agree well with the coefficients used in the model simulating the propagation dynamics. This method uses single beam geometry which is easy to implement and avoids the spurious interfering effects in multi-beam methods originally used for measuring these effects.

Wang, Ding; Leng, Yuxin

2014-10-01

90

Enhancement of surface NMR by laser-polarized noble gases  

NASA Astrophysics Data System (ADS)

The transfer of spin polarization from laser-polarized helium and xenon to spins such as 1H and 13C on the surface of high-surface-area solids (Aerosil) is demonstrated over a temperature range from 4 to 200 K. The transfer mechanism is dipole-dipole cross relaxation between the spins of the adsorbed mobile noble gas and the surface spins (spin-polarization-induced nuclear Overhauser effect). The enhancement of surface proton magnetization by laser-polarized helium at 4 K and 10 K is between one and twofold. Using laser-polarized xenon, enhancement factors of up to 20 were obtained when compared to the Boltzmann polarization in a field of 4.2 T and at a temperature of 130 K.

Rm, T.; Appelt, S.; Seydoux, R.; Hahn, E. L.; Pines, A.

1997-05-01

91

Medical imaging with laser-polarized noble gases  

Microsoft Academic Search

The field of medical imaging with polarized rare gases, just five years old, has brought optical scientists together with medical researchers to perfect techniques and pursue new opportunities for biomedical research. This review, written for the likely reader of these volumes, aims to present the field from several perspectives. The historical perspective shows how applications of nuclear polarization for experiments

Timothy Chupp; Scott Swanson

2001-01-01

92

Abundance and isotopic composition of noble gases in metal and graphite of the Bohumilitz IAB iron meteorite  

NASA Astrophysics Data System (ADS)

Abundances and isotopic compositions of noble gases in metal and graphite of the Bohumilitz IAB iron meteorite were measured. The abundance ratios of spallogenic components in metal reveal a 3He deficiency which is due to the diffusive loss of parent isotopes, i.e., tritium (Tilles, 1963; Schultz, 1967). The diffusive loss likely has been induced by thermal heating by the Sun during cosmic ray exposure (( 160 My; Lavielle et al., 1999). Thermal process such as impact-induced partial loss may have affected the isotopic composition of spallogenic Ne. The 129Xe/131Xe ratio of cosmogenic components in the metal indicates an enhanced production of epi-thermal neutrons. The abundance ratios of spallogenic components in the graphite reveal that it contained small amounts of metal and silicates. The isotopic composition of heavy noble gases in graphite itself was obtained from graphite treated with HF/HCl. The isotopic composition of the etched graphite shows that it contains two types of primordial Xe, i.e., Q-Xe and El Taco Xe. The isotopic heterogeneity preserved in the Bohumilitz graphite indicates that the Bohumilitz graphite did not experience any high(temperature event and, consequently, must have been emplaced into the metal at subsolidus temperatures. This situation is incompatible with an igneous model as well as the impact melting models for the IAB-IIICD iron meteorites as proposed by Choi et al. (1995) and Wasson et al. (1980).

Maruoka, Teruyuki; Matsuda, Jun-Ichi; Kurat, Gero

2001-05-01

93

The Standard Model for Noble Gases in Mantle Geochemistry: Some Observations and Alternatives  

NASA Astrophysics Data System (ADS)

We evaluate the Standard Model of noble gases against a number of observational constraints of relevance to the distribution of noble gases in the Earth's mantle. These constraints include: 1) the lack of evidence for high 3He/4He ratios correlating with high (initial) He concentrations, 2) that MORB and OIB 3He/4He data do not represent two different distributions [1], 3) that systematic global correlations between 3He/4He ratios and lithophile isotopic systems are lacking, 4) that the correlations we do observe are broadly linear, 5) that large, local geographical 3He/4He variations are observed, which are inconsistent with a strongly localized (i.e. plum-stem) flux of high-3He/4He material, and 6) that dramatic temporal 3He/4He variations are observed on very short time scales (10-100 years). Non-layered noble gas mantle models, in which the carrier of unradiogenic He is a relatively noble gas-poor phase scattered in the mantle, are more consistent with this set of constraints. We propose that the carrier of unradiogenic noble gases is primarily olivine [2]. Olivine-rich lithologies, produced in previous partial melting events, are a natural part of the Statistical Upper Mantle Assemblage (SUMA); a highly heterogeneous assemblage of small-to-moderate scale (1-100 km) enriched and depleted lithologies with a wide range in chemical composition, fertility, age and isotopic signatures. The isotopic signatures of oceanic basalts, including noble gases, are obtained by partial melting of the SUMA under slightly different P-T conditions; i.e. different degrees of partial melting and different degrees of homogenization prior to eruption [3-5]. Noble gas isotopic systematics do not trace deep mantle components in the source materials of oceanic basalts. They may, however, indirectly indicate potential temperature, as the order in which different mantle lithologies melt depends on pressure. References: [1] Anderson, EPSL 193, 77-82 (2001). [2] Brooker et al., Lithos, 73, S15 (2004). [3] Morgan and Morgan, EPSL 170, 215-239 (1999). [4] Meibom and Anderson, EPSL 217, 123-139 (2003). [5] Ito and Mahoney, EPSL submitted (2004).

Meibom, A.; Sleep, N. H.; Zahnle, K.; Anderson, D. L.

2004-12-01

94

More on noble gases in Yellowstone National Park hot waters  

Microsoft Academic Search

Water and gas samples from research wells in hydrothermal areas of Yellowstone National Park, U.S.A., have been mass spectrometrically analyzed for their rare gas contents and isotopic composition. In agreement with previous findings, the rare gases have been found to originate from infiltrating run-off water, saturated with air at 10 to 20C. The atmospheric rare gas retention values found for

E. Mazor; R. O. Fournier

1973-01-01

95

Helium solubility in mica and mechanisms for deep transport of noble gases in subduction zones  

NASA Astrophysics Data System (ADS)

We have experimentally determined helium solubility in mica to explore possible transport mechanisms of noble gases in subduction zones. Helium solubility in single crystals of muscovite and F-phlogopite investigated is relatively high, ~1 [He]/PHe (ppm/kbar). This solubility is approximately two orders of magnitude greater than values recently measured for olivine [1], and similar to values recently measured for amphibole with a low density of unoccupied ring sites [2]. Helium was dissolved into the micas by subjecting them to a high pressure noble gas atmosphere (1.26-1.48 He-Ne-Ar kbar) at moderate temperatures (450-700 C), allowing the micas to diffusively equilibrate with the imposed helium fugacity. Diffusion of Ne and Ar is too slow in both micas at the explored conditions to quantify their solubility. Experiments were conducted using a TZM gas pressure medium apparatus (Brown University). Analysis was completed by noble gas LA-MS (Open University, UK). Muscovite (dioctehedral) and F-phlogopite (trioctehedral) represent the two basic structural groups of micas, suggesting micas stabilized at higher pressures and temperatures, such as phengite, can provide a relatively deep transport mechanism for noble gases delivered to subduction zones. Thus, phengite may play a role in explaining atmospheric signatures in mantle derived noble gases [e.g.3,4]. 1. Heber, V. S., Brooker, R. A., Kelley, S. P. & Wood, B. J., GCA, 71, 1041-1061 2. Jackson C.R.M, Kelley S.P., Parman S.W., Cooper R.F., Goldschmidt 2012 Abstract 3. Holland, G. & Ballentine, C. J., Nature 441, 186-191 4. Mukhopadhyay, S.. Nature 486, 101-104

Jackson, C.; Parman, S. W.; Kelley, S. P.; Cooper, R. F.

2012-12-01

96

Noble gas systematics of the Runion mantle plume source and the origin of primordial noble gases in Earths mantle  

Microsoft Academic Search

New noble gas data of ultramafic xenoliths from Runion Island, Indian Ocean, further constrain the characteristics of primordial and radiogenic noble gases in Earths mantle plume reservoirs. The mantle source excess of nucleogenic 21Ne is significantly higher than for the Hawaiian and Icelandic plume reservoirs, similar to excess of radiogenic 4He. 40Ar\\/36Ar of the Runion mantle source can be constrained

Mario Trieloff; Joachim Kunz; Claude J. Allgre

2002-01-01

97

Incorporation of Solar Noble Gases from a Nebula-Derived Atmosphere During Magma Ocean Cooling  

NASA Technical Reports Server (NTRS)

The presence of solar noble gases in the deep interior of the Earth is inferred from the Ne isotopic compositions of MORB (Mid-ocean Ridge Basalts) and OIB (Oceanic Island Basalt); Ar data may also consistent with a solar component in the deep mantle. Models of the transport and distribution of noble gases in the earth's mantle allow for the presence of solar Ar/Ne and Xe/Ne ratios and permit the calculation of lower mantle noble gas concentrations. These mantle data and models also indicate that the Earth suffered early (0.7 to 2 x 10(exp 8) yr) and large (greater than 99 percent) losses of noble gases from the interior, a result previously concluded for atmospheric Xe. We have pursued the suggestion that solar noble gases were incorporated in the forming Earth from a massive, nebula-derived atmosphere which promoted large-scale melting, so that gases from this atmosphere dissolved in the magma ocean and were mixed downward. Models of a primitive atmosphere captured from the solar nebula and supported by accretion luminosity indicate that pressures at the Earth's surface were adequate (and largely more than the required 100 Atm) to dissolve sufficient gases. We have calculated the coupled evolution of the magma ocean and the overlying atmosphere under conditions corresponding to the cessation (or severe attenuation) of the sustaining accretion luminosity, prior to the complete removal of the solar nebula. Such a condition was likely to obtain, for instance, when most of the unaccumulated mass resided in large bodies which were only sporadically accreted. The luminosity supporting the atmosphere is then that provided by the cooling Earth, consideration of which sets a lower limit to the time required to solidify the mantle and terminate the incorporation of atmospheric gases within it. In our initial calculations, we have fixed the nebula temperature at To = 300K, a value likely to be appropriate for nebular temperatures at lAU in the early planet-building epoch. We treated the background (nebula) pressure as an adjustable, time-dependent parameter. Additional information is contained within the original extended abstract.

Woolum, D. S.; Cassen, P.; Wasserburg, G. J.; Porcelli, D.; DeVincenzi, Donald (Technical Monitor)

1998-01-01

98

Retention of Radioactive Noble Gases in Nuclear Power Stations by Means of Activated Charcoal Delay Systems. A Status Report.  

National Technical Information Service (NTIS)

Since the beginning of the 1970s off-gas systems using activated charcoal have been used in BWRs and PWRs to minimize the release of radioactive noble gases and the resultant exposure of the environment. In practice, the power-related noble gas emission r...

H. J. Schroeder

1983-01-01

99

Adsorption behavior of ternary mixtures of noble gases inside single-walled carbon nanotube bundles  

NASA Astrophysics Data System (ADS)

In order to study the gas-storage and gas-filtering capability of carbon nanotube (CNT) bundles simultaneously, we considered the adsorption behavior of a ternary mixture of noble gases, including Argon (Ar), Krypton (Kr), and Xenon (Xe), i.e., Ar-Kr-Xe mixture, on (10, 10) single-walled carbon nanotube (SWCNT) bundles. Molecular dynamics (MD) simulations at different temperatures of (75, 100, 150, 200, 250, and 300) K were performed, and adsorption energies, self-diffusion coefficients, activation energies, and radial distribution functions (RDFs) were computed to analyze the thermodynamics, transport and structural properties of the adsorption systems. It is observed that the SWCNT bundles have larger contents of heavier noble gases compared to the lighter ones. This interesting behavior of SWCNT bundles makes them proper candidates for gas-storage and gas molecular-sieving processes.

Foroutan, Masumeh; Nasrabadi, Amir Taghavi

2010-09-01

100

Nuclear magnetic resonance of laser-polarized noble gases in molecules, materials, and organisms  

NASA Astrophysics Data System (ADS)

Conventional nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) are fundamentally challenged by the insensitivity that stems from the ordinarily low spin polarization achievable in even the strongest NMR magnets. However, by transferring angular momentum from laser light to electronic and nuclear spins, optical pumping methods can increase the nuclear spin polarization of noble gases by several orders of magnitude, thereby greatly enhancing their NMR sensitivity. This dissertation is primarily concerned with the principles and practice of optically pumped nuclear magnetic resonance (OPNMR). The enormous sensitivity enhancement afforded by optical pumping noble gases can be exploited to permit a variety of novel NMR experiments across many disciplines. Many such experiments are reviewed, including the void-space imaging of organisms and materials, NMR and MRI of living tissues, probing structure and dynamics of molecules in solution and on surfaces, and zero-field NMR and MRI.

Goodson, Boyd Mclean

101

Cosmogenic 10Be and Noble Gases in Diogenites  

NASA Astrophysics Data System (ADS)

Introduction: A recent reevaluation of the 3He, 21Ne, and 38Ar cosmic-ray exposure ages of eight non-Antarctic and three Antarctic diogenite falls led to a consistent set of exposure ages with a major cluster at 22 Ma and a possible second cluster around 40 Ma [1]. These clusters coincide with two major peaks in the exposure-age distributions of the genetically related eucrites and howardites [2], but the scarcity of young diogenites is remarkable [3]. An update of the exposure-age distribution for diogenites, including nine separate Antarctic falls, will be presented and possible differences in exposure history between Antarctic and non-Antarctic diogenites will be discussed. The exposure-age distributions of eucrites and howardites are still controversial [2,3], as conventional shielding corrections--on the basis of the 22Ne/21Ne ratio--cannot be applied. Therefore, the use of other shielding parameters, such as 10Be or 26Al, is considered. We examined the relation between 10Be contents and 22Ne/21Ne ratios in diogenites to obtain more insight into the shielding sensitivity of the 10Be production rate. Experimental: In addition to the existing database of more than 30 noble gas analyses [4] we carried out noble gas measurements on 5 non-Antarctic diogenites and on 12 Antarctic samples from 9 separate falls. On the same samples 10Be was measured by AMS. The experimental uncertainties in the 10Be values are 2-3%, those in the 22Ne/21Ne ratios are 0.5-1.0%. Results and Conclusions: The major exposure-age cluster at 22 Ma contains about 45% of the diogenite falls, indicating a major impact on its parent body. However, the presence of several younger diogenites suggests that this collisional event was not necessarily as destructive as previously suggested [3]. Four diogenites show exposure ages around 40 Ma, indicating a second major impact on the HED parent body. Although some Antarctic diogenites have unique mineralogical features [5,6], we didn't find any evidence for different populations on the basis of their exposure histories. Figure 1 shows the experimental relation between 10Be contents and 22Ne/21Ne ratios measured in diogenites. The 10Be contents decrease by 30-35%, while corresponding 22Ne/21Ne ratios increase from 1.07 to 1.29. Graf's semi- experimental model predicts--for L chondrites with preatmospheric radii less than 50 cm--a decrease of about 50% in 10Be over this interval of 22Ne/21Ne ratios [7]. This discrepancy cannot be explained by the minor differences in composition with respect to 10Be production. Therefore, our results indicate that this model is slightly overestimating the shielding sensitivity of 10Be. Five points do not fall within 2 sigma on the best (exponential) fit. Measurements of additional radionuclides may contribute to a better understanding of their outlying character. Acknowledgments: We thank the MWG in the USA, the NIPR in Tokyo and the National Museums for Natural History in Washington, London, and Paris for diogenite samples. This work was financially supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO). References: [1] Welten K. C. et al. (1991) Meteoritics, 26, 408. [2] Schultz L. (1987) LPSC XVIII, 884-885. [3] Alymer D. et al. (1988) GCA, 52, 1691-1698. [4] Schultz L. and Kruse H. (1989) Meteoritics, 24, 155-172. [5] Takeda H. (1991) GCA, 55, 35-57. [6] Berkley J. L. and Boynton N. J. (1992) Meteoritics, 27, 387-394. [7] Graf Th. et al. (1990) GCA, 54, 2521-2534. Figure 1, which appears in the hard copy, shows shielding effects on P10 in diogenites.

Welten, K. C.; Lindner, L.; van der Borg, K.; Loeken, Th.; Scherer, P.; Schultz, L.

1993-07-01

102

Noble gases in the Finero phlogopite-peridotites, western Italian Alps  

Microsoft Academic Search

Here we report results from an investigation of noble gases in a specimen with layers of very fine-grained apatite and orthopyroxene from the Finero ultramafic complex, western Italian alps. We have also examined fresh olivine grains separated from phlogopite-harzburgites without an apatite layer. Fluid inclusions of these olivine separates appeared rich in radiogenic components such as 4He, 21Ne and 40Ar,

Takuya Matsumoto; Tomoaki Morishita; Jun-Ichi Matsuda; Toshiyuki Fujioka; Masamichi Takebe; Koshi Yamamoto; Shoji Arai

2005-01-01

103

Primordial noble gases in chondrites: the abundance pattern was established in the solar nebula.  

PubMed

Ordinary chondrites, like carbonaceous chondrites, contain primordial noble gases mainly in a minor phase comprising

Alaerts, L; Lewis, R S; Anders, E

1977-12-01

104

Pulse-Nmr Studies of Spin Relaxation Relevant to Laser-Polarized Noble Gases  

Microsoft Academic Search

The past few years have witnessed a tremendous increase in applications of noble gases polarized by spin -exchange with a laser-optically pumped alkali-metal vapor. The applications have benefited from the prior and ongoing study of more fundamental questions, both directly and indirectly related to spin exchange. This thesis addresses several such questions and also presents a new application of laser-polarized

Brian Timothy Saam

1995-01-01

105

Initial results of noble gases in micrometeorites from the Transantarctic Mountains, Antarctica  

NASA Astrophysics Data System (ADS)

The bulk of extraterrestrial matter collected by Earth is in the form of micrometeorites, which have a main flux onto Earth at about 220 ?m in diameter [1]. According to the petrographic and geochemical data, most of the small micrometeorites have been related to CM chondrites [2]. Recent studies suggest that larger micrometeorites (> 300?m) mostly derive from ordinary chondrite sources e.g. [3-5]. Following some models [6], they may have made important contributions to the volatile inventory of the Earth. We have initiated a coupled comprehensive survey of noble gas contents and petrography in micrometeorites. While helium and neon are generally dominated by the solar wind contribution, the inventory of heavy primordial noble gases has been hardly characterized so far. In particular, useful data are lacking on the diagnostic isotopic composition of xenon. We hope to fill this gap, since huge amounts of material are available. This might make a contribution towards understanding some aspects of the formation of the solar system and in particular the terrestrial atmosphere. We will present results obtained on "large" micrometeorites from Victoria Land, Transantarctic Mountains. These were collected during a PNRA (Programma Nazionale delle Ricerche in Antartide, Italy) expedition on top of the Miller Butte micrometeorite traps #45 b and c [7]. We reported first results in [8]. Our research includes however, also material from other collections, e.g. CONCORDIA [9, 10]. [1] Love, S.G., Brownlee, D.E. (1993) Science 262, 550-553. [2] Kurat, G. et al. (1994) Geochimica et Cosmochimica Acta 58, 3879-3904. [3] Genge, M.J. et al. (2008) Meteoritics & Planetary Science 43, 497-515. [4] Dobrica, E. et al. (2011) Meteoritics & Planetary Science 46, 1363-1375. [5] Van Ginneken M. et al. (2012) Meteoritics & Planetary Science 47, 228-247. [6] Maurette, M. et al. (2000) Planetary and Space Science 48, 1117-1137. [7] Rochette P. et al. (2008) Proceedings of the National Academy of Sciences , 105, 18206-18211. [8] Baecker B. et al. (2012) 43rd Lunar & Planetary Science Conference (abs. #1824). [9] Duprat J. et al. (2007) Advances in Space Research 39, 605-611. [10] Baecker B. et al. (2012) 75th Annual Meeting of the Meteoritical Society (abs. #5056).

Baecker, B.; Cordier, C.; Folco, L.; Trieloff, M.; Ott, U.

2012-12-01

106

Geothermochronology based on noble gases: I. Stability of the U-Xe isotopic system in nonmetamict zircons  

Microsoft Academic Search

The paper presents data on persistent tendencies and relations in the migration of noble gases in U-bearing minerals of various\\u000a composition: uraninite, pitchblende, metamict zircon, khlopinite, samarskite, betafite, and ampangabeite from various regions\\u000a worldwide. The escape curves of all noble gases (starting with radiogenic He, Kr, and Xe and ending with nucleogenic 38Ar) during annealing in the laboratory are demonstrated

Yu. A. Shukolyukov; M. M. Fugzan; I. P. Paderin; S. A. Sergeev; D. P. Krylov

2009-01-01

107

The role of van der Waals interactions in the adsorption of noble gases on metal surfaces.  

PubMed

Adsorption of noble gases on metal surfaces is determined by weak interactions. We applied two versions of the nonlocal van der Waals density functional (vdW-DF) to compute adsorption energies of Ar, Kr, and Xe on Pt(111), Pd(111), Cu(111), and Cu(110) metal surfaces. We compared our results with data obtained using other density functional approaches, including the semiempirical vdW-corrected DFT-D2. The vdW-DF results show considerable improvements in the description of adsorption energies and equilibrium distances over other DFT based methods, giving good agreement with experiments. We also calculated perpendicular vibrational energies for noble gases on the metal surfaces using vdW-DF data and found excellent agreement with available experimental results. Our vdW-DF calculations show that adsorption of noble gases on low-coordination sites is energetically favored over high-coordination sites, but only by a few meV. Analysis of the two-dimensional potential energy surface shows that the high-coordination sites are local maxima on the two-dimensional potential energy surface and therefore unlikely to be observed in experiments; this provides an explanation of the experimental observations. The DFT-D2 approach with the standard parameterization was found to overestimate the dispersion interactions, and to give the wrong adsorption site preference for four of the nine systems we studied. PMID:23032730

Chen, De-Li; Al-Saidi, W A; Johnson, J Karl

2012-10-24

108

The role of van der Waals interactions in the adsorption of noble gases on metal surfaces  

NASA Astrophysics Data System (ADS)

Adsorption of noble gases on metal surfaces is determined by weak interactions. We applied two versions of the nonlocal van der Waals density functional (vdW-DF) to compute adsorption energies of Ar, Kr, and Xe on Pt(111), Pd(111), Cu(111), and Cu(110) metal surfaces. We compared our results with data obtained using other density functional approaches, including the semiempirical vdW-corrected DFT-D2. The vdW-DF results show considerable improvements in the description of adsorption energies and equilibrium distances over other DFT based methods, giving good agreement with experiments. We also calculated perpendicular vibrational energies for noble gases on the metal surfaces using vdW-DF data and found excellent agreement with available experimental results. Our vdW-DF calculations show that adsorption of noble gases on low-coordination sites is energetically favored over high-coordination sites, but only by a few meV. Analysis of the two-dimensional potential energy surface shows that the high-coordination sites are local maxima on the two-dimensional potential energy surface and therefore unlikely to be observed in experiments; this provides an explanation of the experimental observations. The DFT-D2 approach with the standard parameterization was found to overestimate the dispersion interactions, and to give the wrong adsorption site preference for four of the nine systems we studied.

Chen, De-Li; Al-Saidi, W. A.; Johnson, J. Karl

2012-10-01

109

Simultaneous measurements of radioactive noble gases and aerosols in the vicinity of a nuclear power station  

NASA Astrophysics Data System (ADS)

Simultaneous measurements of the activity concentration of radioactive noble gases and aerosols have been made in the vicinity of the Swedish nuclear power station at Ringhals. The primary photon fluence rate due to radioactive noble gases in the air was measured with a Ge detector, placed on the ground 4.4 km away from the power station. Surface air was also filtered through Microsorban or glass fibre filters using a high-volume air pump. The filters were changed weekly, and the activity concentration of aerosol-bound radionuclides was measured with a Ge detector. Measurements of the radioactive noble gases show that the Gaussian plume model with standard dispersion parameters can be used to calculate the air concentration within a factor of 2. For aerosols emanating from the nuclear power station the ratios between measured air concentrations and air concentrations calculated from reported releases were about 30 for 60Co and 10 for 140Ba. This discrepancy between measured and calculated air concentrations is probably due to underestimated reported releases, caused by particle size fractionation in the stack of the power plant.

Bjurman, Bjrn; Erlandsson, Bengt; Mattsson, Sren

1989-01-01

110

Use of Stable Noble Gases as a Predictor of Reactor Fuel Type and Exposure  

SciTech Connect

Ensuring spent reactor fuel is not produced to provide weapons-grade plutonium is becoming a major concern as many countries resort to nuclear power as a solution to their energy problems. Proposed solutions range from the development of proliferation resistant fuel to continuous monitoring of the fuel. This paper discusses the use of the stable isotopes of the fissiogenic noble gases, xenon and krypton, for determining the burnup characteristics, fuel type, and the reactor type of the fuel from which the sample was obtained. The gases would be collected on-stack as the fuel is reprocessed, and thus confirm that the fuel is as declared.

Fearey, B.L.; Charlton, W.S.; Perry, R.T.; Poths, J.; Wilson, W.B.; Hemberger, P.H.; Nakhleh, C.W.; Stanbro, W.D.

1999-08-30

111

Slab-Derived Noble Gases Preserved in Wedge Mantle Peridotite From the Sanbagawa Belt, Shikoku, Japan  

NASA Astrophysics Data System (ADS)

Subduction volcanism is generally considered to form a 'subduction barrier' that efficiently recycles volatile components contained in subducted slabs back to the Earth's surface. Water-rich fluids released from subducting slabs play an important role in this volatile circulation. However, noble gases in the fluids are not well investigated. The Higashi-akaishi peridotite body in the Sanbagawa metamorphic belt, southwest Japan, is a possibly unique example of a km-scale sliver of a former mantle wedge exhumed from depths of at least 100 km. The body mainly consists of dunite with minor amounts of garnet-bearing rocks. Penetrative porphyroclastic microstructure in the dunite is associated with the development of olivine LPO patterns implying hydrous and high-stress conditions. Serpentine dominated micro-inclusions in the porphyroclastic olivine grains are regarded as relics of former water-rich inclusions developed in the wedge mantle above a subducting slab. Thus, it is expected that these micro-inclusions should preserve noble gas characteristics of slab-derived fluids and measurements of their compositions could provide important constraints on geochemical models of subduction zones. To extract noble gases from the micro-inclusions we first step heated the samples up to 800C, above the breakdown temperature of serpentine minerals, before crushing them in vacuo. This treatment ensures both platy antigorite matrix grains and cross-cutting lizardite veins that formed after the micro-inclusions broke down during the heating and their contained noble gases were almost entirely released at this stage. In contrast, micro-inclusions are enclosed in thermally stable "capsules" of olivine and their noble gases should be dominantly released during the subsequent crushing. The determined isotopic characteristics of noble gases in the micro-inclusions are as follows. (1) {}3He/{}4He ratios of about 2 Ra representing a mixture of mantle and radiogenic He. (2) {}40Ar/{}36Ar ratios up to 440 that are close to atmospheric ratios with a small contribution of mantle and/or radiogenic Ar. The mantle He and atmospheric Ar should be an intrinsic feature of the micro-inclusions. This implies that Ar in the wedge mantle was heavily contaminated by an atmospheric component derived from the subducting slab. Ar analyses of neutron-irradiated samples revealed insignificant contribution of in situ radiogenic {}40Ar accumulated after the formation of micro-inclusions that predates cooling ages of the Sanbagawa metamorphism (c. 76-94 Ma). However, it remains uncertain whether slab-derived He (possibly crust-like, enriched in radiogenic He) is contained in the micro-inclusions, due to relatively poor constraints on the amount of in situ radiogenic He production. The noble gas isotopic features of the micro-inclusions are similar to those of arc volcanic gases and rocks. This implies that the Higashi-akaishi peridotite body has frozen in and preserved an inferred but previously unseen part of the recycling process whereby noble gases (and probably other volatiles) are injected into the wedge mantle just above the subducting slab before being recycled back to the atmosphere via arc volcanism.

Sumino, H.; Mizukami, T.; Wallis, S. R.

2005-12-01

112

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

NASA Astrophysics Data System (ADS)

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.; Lewis, R. S.; Anders, E.

1982-06-01

113

Mass fractionation of noble gases in synthetic methane hydrate: Implications for naturally occurring gas hydrate dissociation  

USGS Publications Warehouse

As a consequence of contemporary or longer term (since 15 ka) climate warming, gas hydrates in some settings may presently be dissociating and releasing methane and other gases to the ocean-atmosphere system. A key challenge in assessing the impact of dissociating gas hydrates on global atmospheric methane is the lack of a technique able to distinguish between methane recently released from gas hydrates and methane emitted from leaky thermogenic reservoirs, shallow sediments (some newly thawed), coal beds, and other sources. Carbon and deuterium stable isotopic fractionation during methane formation provides a first-order constraint on the processes (microbial or thermogenic) of methane generation. However, because gas hydrate formation and dissociation do not cause significant isotopic fractionation, a stable isotope-based hydrate-source determination is not possible. Here, we investigate patterns of mass-dependent noble gas fractionation within the gas hydrate lattice to fingerprint methane released from gas hydrates. Starting with synthetic gas hydrate formed under laboratory conditions, we document complex noble gas fractionation patterns in the gases liberated during dissociation and explore the effects of aging and storage (e.g., in liquid nitrogen), as well as sampling and preservation procedures. The laboratory results confirm a unique noble gas fractionation pattern for gas hydrates, one that shows promise in evaluating modern natural gas seeps for a signature associated with gas hydrate dissociation.

Hunt, Andrew G.; Stern, Laura; Pohlman, John W.; Ruppel, Carolyn; Moscati, Richard J.; Landis, Gary P.

2013-01-01

114

The five stable noble gases are sensitive unambiguous tracers of glacial meltwater  

NASA Astrophysics Data System (ADS)

five inert noble gasesHe, Ne, Ar, Kr, and Xeexhibit a unique dissolved gas saturation pattern resulting from the formation and addition of glacial meltwater to seawater. He and Ne become oversaturated, and Ar, Kr, and Xe become undersaturated to varying percentages. For example, addition of 10 glacial meltwater to seawater results in a saturation anomaly of ?He = 12.8%, ?Ne = 8.9%, ?Ar = -0.5%, ?Kr = -2.2%, and ?Xe = -3.3%. This pattern in noble gas saturation reflects a unique meltwater signature that is distinct from the other major physical processes that modify the gas concentration and saturation, namely, seasonal changes in temperature at the ocean surface and bubble mediated gas exchange. We use Optimum Multiparameter analysis to illustrate how all five noble gases can help distinguish glacial meltwater from wind-driven bubble injection, making them a potentially valuable suite of tracers for glacial melt and its concentration in the deep waters of the world ocean.

Loose, B.; Jenkins, W. J.

2014-04-01

115

Occlusion of noble gases (He, Ne, Ar, Kr, Xe) into synthetic magnetite at 5001300C  

Microsoft Academic Search

The trapping mechanism of noble gases during growth of magnetite is investigated by oxidizing Fe with water vapor at temperatures ranging from 500 to 1300C. An apparent negative correlation between the concentration of argon and synthetic temperatures suggests that gases are trapped by adsorption. The fixation of adsorbed gas atoms is probably due to crystal growth. The elemental fractionation pattern

Takuya Matsumoto; Kazuyuki Maruo; Akira Tsuchiyama; Jun-Ichi Matsuda

1996-01-01

116

Nuclear tracks and light noble gases in ALH84001: Preatmospheric size, fall characteristics, cosmic ray exposure duration and formation age  

Microsoft Academic Search

Cosmic ray produced nuclear tracks and noble gases have been studied in the martian orthopyroxenite ALH84001, to delineate its cosmic ray exposure history, preatmospheric size and fall characteristics. A K-Ar age of 3.9Ga, cosmic ray exposure duration of 16.7Ma and a preatmospheric radius of 10cm have been deduced from the noble gas and track data. The track data suggest ALH84001

J. N. Goswami; N. Sinha; S. V. S. Murty; R. K. Mohapatra; C. J. Clement

1997-01-01

117

Implantation of high concentration noble gases in cubic zirconia and silicon carbide: A contrasted radiation tolerance  

NASA Astrophysics Data System (ADS)

The modifications of the microstructure of yttria-stabilized cubic zirconia and silicon carbide single crystals implanted with high concentrations of noble gas ions and subsequently annealed at high temperature were characterized using RBS/C, XRD and TEM. It is found that the annealing behavior is strongly dependent on both the material and the implanted noble gases. Ar-implanted yttria-stabilized zirconia shows no significant microstructural modification upon annealing at 800 C, e.g. dislocations are still present and the size of the Ar bubbles does not evolve. This is in strong contrast with previous observations on helium-implanted zirconia, where the formation of bubbles and elongated fractures were observed. In the case of SiC, thermal annealing at 1000 C shows an enhanced damage recovery when He is implanted as compared to Ar implantation and the recrystallization of the matrix is accompanied with the release of noble gas atoms. This difference can be ascribed to different atomic radii, and thus mobility of implanted species.

Veli?a, Gihan; Debelle, Aurlien; Thom, Lionel; Mylonas, Stamatis; Vincent, Laetitia; Boulle, Alexandre; Jagielski, Jacek; Pantelica, Dan

2014-08-01

118

Experimental study of disruption mitigation using massive injection of noble gases on Tore Supra  

NASA Astrophysics Data System (ADS)

Disruptions are a major threat for future tokamaks, including ITER. Disruption-generated heat loads, electromagnetic forces and runaway electrons will not be tolerable for next-generation devices. Massive noble gas injection is foreseen as a standard mitigation system for these tokamaks. Disruption mitigation experiments have been carried out on Tore Supra to study various injection scenarios and to investigate gas jet penetration and mixing. Comparisons of different gases (He, Ne, Ar, He/Ar mixture) and amounts (from 5 to 500 Pa m3) were made, showing that light gases are more efficient regarding runaway electron suppression than heavier gases. Eddy currents in the limiter are moderately reduced by all the gases, and may be more dependent on the time constants of the structures than on the gas species. The density rise induced by the massive injection before the thermal quench is higher and faster with light gases. Gas jet penetration in the cooling phase is observed to be shallow and independent of the gas nature and amount. The gas cold front is stopped along the q = 2 surface where it triggers MHD instabilities, expelling thermal energy from the plasma core.

Reux, C.; Bucalossi, J.; Saint-Laurent, F.; Gil, C.; Moreau, P.; Maget, P.

2010-09-01

119

Elementary and isotopic compositions of noble gases in geothermal fluids of Tuscany, Italy  

SciTech Connect

Analyses were made of the major gases, as well as helium and radon, in fluids from more than 90 geothermal wells in Tuscany. The elementary and isotopic abundances of the noble gases were determined by multiple samplings in seven wells. The results show good correlations between constituents of atmospheric origin and those of deep origin, suggesting the existence of a mixing between cold waters and hot fluids, a process which takes place at considerable depth. The helium isotopic ratios indicate the presence of a radiogenic crustal component. Enrichment of radiogenic argon and excess nucleogenic neon-21 were measured in some samples. Calculations were also made of the /sup 4/He//sup 222/Rn ages of the gas sources.

Nuti, S.

1984-01-01

120

On the distribution of noble gases in Allende - A differential oxidation study  

NASA Technical Reports Server (NTRS)

The investigation makes use of an oxidizing technique which is based on methods widely employed in light stable isotope analysis. The utilization of closed-system differential combustion in molecular oxygen in an ultra-high vacuum system on-line with a spectrometer makes it possible to conduct precise abundance and isotopic measurements of all gases released in progressive oxidation and/or thermal outgassing of the host phases. Attention is given to the noble gases mobilized in progressive oxidation of a carbon-rich acid residue and a fine-grained matrix separate. The progressive oxidation of the Allende matrix is discussed. Release occurred over three distinct intervals, characterized by oxidation below 600 C, gas mobilization between 630 and 750 C, and high-temperature diffusive release.

Frick, U.; Pepin, R. O.

1981-01-01

121

Bubble formation, vesicularity and fractionation of noble gases during MORB degassing  

NASA Astrophysics Data System (ADS)

The fractionation of noble gases in oceanic basalts gives information on the source region and on the transport of volatiles up to the seafloor. For instance, the large distribution (~1-1,000) of the 4He/40Ar* ratio in mid-ocean ridge basalts (MORB), is interpreted as the signature of different degassing scenarios taking place at depth. Thus, a low value of this ratio is explained by a closed system degassing whereas a high value is assigned either to an open system degassing (where vesicles are lost in a magma chamber or at depth during magma ascent) or to a kinetic disequilibrium induced by a rapid magma ascent just prior eruption. Unfortunately, CO2 has a very low solubility in basaltic melts at pressure corresponding to the seafloor and an overwhelming majority of erupted lavas have lost their pristine volatile contents. However notable exceptions are the popping rocks characterized by a large vesicularity, a high CO2 content and a 4He/40Ar* ratio compatible with the expected U/K ratio of the upper mantle. Those samples likely have experienced a CO2 exsolution at about 35 km depth in the oceanic mantle. So, the very existence of these exceptional MORB samples suggests that CO2-rich melts could be present at a greater depth. Thus, explosive eruptions near ocean spreading centers are well documented (Hekinian et al., 2000) and are associated with volcaniclastic deposits containing highly vesicular basalts, a feature which suggests that this volcanism is driven by CO2-rich magmas (Helo et al., 2011). But how much CO2-rich are these magmas, that is the question. The objective of this study is to use molecular dynamics simulation (MD) to evaluate the vesicularity and the fractionation of noble gases in a degassing MORB melt. A previous simulation study (Guillot and Sator, 2011) has shown that the solubility of CO2 in basaltic melts increases steadily with the pressure and deviates significantly from the Henry's law at high pressures. From the CO2 solubility curve and the equations of state of the two coexisting phases, deduced from the MD simulation, we have evaluated the evolution of the vesicularity of a MORB melt at depth as function of its initial CO2 contents. An excellent agreement is obtained between our results and data on MORB samples collected at oceanic ridges. A conclusion is that CO2-rich magmas may exist at 100 km depth or more in the oceanic mantle. Moreover, we have evaluated the partitioning and the fractionation of noble gases between the CO2-saturated melt and supercritical CO2 vesicles as function of the pressure. We show that the large distribution of the 4He/40Ar* ratio reported in the literature can be explained if the magma experiences a suite of vesiculation and vesicle loss during ascent. Finally, by applying a pressure drop to a volatile bearing melt (CO2+noble gas), the MD simulation reveals the main steps of bubble formation and noble gas transfer at the nanometric scale. A key result is that the transfer of noble gases is found to be concomitant with CO2 bubble nucleation, a finding which suggests that the difference in diffusivity between He and Ar in the degassing melt has practically no effect on the 4He/40Ar* ratio measured in the vesicles. Guillot B., Sator N. (2011), GCA 75, 1829-1857 Hekinian et al. (2000), J. Volcanol. Geotherm. Res. 98, 49-77 Helo et al. (2011), Nature Geoscience 4, 260-263

Sator, N.; Guillot, B. B.; Aubry, G.

2012-12-01

122

A theoretical study of the cohesion of noble gases on graphite  

NASA Astrophysics Data System (ADS)

The interactions of the noble gases with a graphene sheet are investigated theoretically. The short range repulsive interaction between the noble gas and each carbon atom is described using Hartree-Fock atomic densities and a local density functional theory with the exchange functional corrected for the finite range of the interaction by introducing a Rae-type correction depending on the effective number of electrons. The long range interactions are introduced as the sum of the Axilrod-Teller triple-dipole interaction plus the dipole-dipole and dipole-quadrupole dispersive attractions damped according to the theory of Jacobi and Csanak. The energy arising from the interactions between the permanent quadrupoles on the carbon atoms with the dipole they induce on the noble gas is negligible, being nonzero only on account of the atomistic structure of graphene. The mobile and delocalized nature of the graphene ? electrons causes the effective number of electrons to be around 500 rather than that of 12 appropriate for a system of entirely localized interactions with individual carbon atoms. Inclusion of the Axilrod-Teller term is required to obtain reliable predictions for the binding energies and equilibrium geometries. Absorption of a noble gas atom is predicted to occur at the site above the center of a six membered ring although this is preferred over two other sites by only about 5 meV. The methods presented for generating all the potentials can be applied to derive the interactions between any ion and carbon atom in the wall of a single-walled nanotube. Knowledge of these interactions is required to study the alkali halide nanocrystals encapsulated in single-walled carbon nanotubes of current interest.

Bichoutskaia, Elena; Pyper, Nicholas C.

2008-01-01

123

A new automated method for measuring noble gases and their isotopic ratios in water samples  

NASA Astrophysics Data System (ADS)

A method is presented for precisely measuring all five noble gases and their isotopic ratios in water samples using multiple programmed multistage cryogenic traps in conjunction with quadrupole mass spectrometry and magnetic sector mass spectrometry. Multiple automated cryogenic traps, including a two-stage cryotrap used for removal of water vapor, an activated charcoal cryotrap used for helium separation, and a stainless steel cryotrap used for neon, argon, krypton, and xenon separation, allow reproducible gas purification and separation. The precision of this method for gas standards is 0.10% for He, 0.14% for Ne, 0.10% for Ar, 0.14% for Kr, and 0.17% for Xe. The precision of the isotopic ratios of the noble gases in gas standards are 1.9 for 20Ne/22Ne, 2.0 for 84Kr/86Kr, 2.5 for 84Kr/82Kr, 0.9 for 132Xe/129Xe, and 1.3 for 132Xe/136Xe. The precision of this method for water samples, determined by measurement of duplicate pairs, is 1% for He, 0.9% for Ne, 0.3% for Ar, 0.3% for Kr, and 0.2% for Xe. An attached magnetic sector mass spectrometer measures 3He/4He with precisions of 0.1% for air standards and 0.14% for water samples.

Stanley, Rachel H. R.; Baschek, Burkard; Lott, Dempsey E.; Jenkins, William J.

2009-05-01

124

Noble gases in South Indian carbonatites: Trapped and in situ components  

NASA Astrophysics Data System (ADS)

We have studied noble gases in carbonates and apatites from three carbonatites of South India, namely Hogenakal (2400 Ma), Sevattur (770 Ma) and Khambamettuu (523 Ma) by vacuum crushing. Apatite has also been analysed by pyrolysis. Vacuum crushing mostly releases the trapped gas components. The ratios 21Ne/ 20Ne, 22Ne/ 20Ne and 40Ar/ 36Ar increase with progressive crushing due to preservation of different composition gases in smaller inclusions released in later steps. This heterogeneity of isotopic composition of fluid inclusions is a consequence of the involvement of magmas carrying different noble gas signatures. The inclusions with lower ratios suggest the presence of a subducted atmospheric component, while the higher 21Ne/ 20Ne, 22Ne/ 20Ne and 40Ar/ 36Ar can be attributed to the presence of an enriched lithospheric mantle component. In addition, very minor trapped gases from less degassed, deeper mantle may also be present but overprinted by lithospheric and/or nucleogenic components. We propose that these carbonatites were generated only in an advanced stage of magmatism when this lithospheric component overwhelmed any contribution from the deeper mantle source. The lithospheric mantle underwent enrichment during an ancient subduction process through mantle metasomatism manifested in nucleogenic/radiogenic isotopic ratios of 21Ne/ 20Ne, 22Ne/ 20Ne and 40Ar/ 36Ar. The apatites analysed by pyrolysis clearly show nucleogenic 21Ne from 18O(?,n) reaction. We have demonstrated the potential of using U,Th- 21Ne systematics as a thermo-chronometer in conjunction with the established U,Th- 4He and U- 136Xe clocks. While for Hogenakal, the U,Th- 21Ne age of 845 127 Ma is in agreement with the age of emplacement of other adjacent younger carbonatites, syenites and alkali granites, for the Sevattur apatite (738 111 Ma) it indicates the crystallisation age.

Murty, S. V. S.; Basu, S.; Kumar, Anil

2007-04-01

125

Effects of traces of molecular gases (hydrogen, nitrogen) in glow discharges in noble gases  

NASA Astrophysics Data System (ADS)

The "Grimm" type of low pressure glow discharge source, introduced some forty years ago, has proved to be a versatile analytical source. A flat sample is used as the cathode and placed about 0.2mm away from the end of a hollow tubular anode leading to an obstructed discharge. When the source was first developed, it was used for the direct analysis of solid metallic samples by optical emission spectroscopy (OES), normally with argon as the plasma gas; it was soon found that, using suitable electrical parameters, the cathode material was sputtered uniformly from a circular crater of diameter equal to that of the tubular anode, so that the technique could be used for compositional depth profile analysis (CDPA). Over the years the capability and applications of the technique have steadily increased. The use of rf powered discharges now permits the analysis of non-conducting layers and samples; improved instrumental design now allows CDPA of ever thinner layers (e.g. resolution of layers 5 nm thick in multilayer stacks is possible). For the original bulk material application, pre-sputtering could be used to remove any surface contamination but for CDPA, analysis must start immediately the discharge is ignited, so that any surface contamination can introduce molecular gases into the plasma gas and have significant analytical consequences, especially for very thin layers; in addition, many types of samples now analysed contain molecular gases as components (either as occluded gas, or e.g. as a nitride or oxide), and this gas enters the discharge when the sample is sputtered. It is therefore important to investigate the effect of such foreign gases on the discharge, in particular on the spectral intensities and hence the analytical results. The presentation will concentrate mainly on the effect of hydrogen in argon discharges, in the concentration range 0-2 % v/v but other gas mixtures (e.g. Ar/N_2, Ne/H_2) will be considered for comparison. In general, the introduction of molecular gases can change the discharge impedance, alter the sputtering rate and crater profile and cause changes in the absolute and relative intensities of lines in both the atomic and ionic spectra of the sample element and the plasma gas. The authors wish to acknowledge financial support from EC funded Analytical Glow Discharge Research Training Network GLADNET, contract no. MRTN-CT-2006-035459. P. Smid thanks the Deutsche Forschungsgemeinschaft (Ref 436 TSE 17/7/06) for support while carrying out experiments at IFW Dresden.

Steers, E. B. M.; Smid, P.; Hoffmann, V.

2008-07-01

126

Momentum transfer cross sections for the heavy noble gases  

NASA Astrophysics Data System (ADS)

We present momentum transfer cross sections for elastic electron scattering from argon, krypton and xenon atoms over the energy range from zero to 1 keV. These have been calculated using the Dirac equations with a relativistic complex optical potential which includes polarization of the target atom by the incident electron and allows for the absorption of some of the incident electron flux into channels representing excitation and ionization of the atom. In order to aid in plasma modelling calculations, we provide simple analytic fits to these cross sections as well as to the elastic scattering cross sections. Comparisons are made with previous experimental and theoretical results.

McEachran, R. P.; Stauffer, A. D.

2014-06-01

127

Noble gases in pyroxenites and metasomatised peridotites from the Newer Volcanics, southeastern Australia: implications for mantle metasomatism  

Microsoft Academic Search

The elemental and isotopic compositions of five noble gases (He, Ne, Ar, Kr and Xe) have been determined in selected, well-documented, ultramafic xenoliths from southeastern Australia. These xenoliths include both spinel-bearing peridotites with an apparent metasomatic overprint and garnet-bearing pyroxenites. In general, helium, neon, argon and xenon isotopic ratios from gases trapped in fluid inclusions of the samples are mid-ocean

Takuya Matsumoto; Masahiko Honda; Ian McDougall; Suzanne Y. O'Reilly; Marc Norman; Greg Yaxley

2000-01-01

128

The quest for regolithic howardites. Part 1: Two trends uncovered using noble gases  

NASA Astrophysics Data System (ADS)

We report noble gas data (helium (He), neon (Ne), argon (Ar), krypton (Kr) and xenon (Xe)), nominal gas retention ages (K-Ar, U-Th-He) and cosmic ray exposure (CRE) ages for the ten howardites EET 83376, EET 99408, LEW 85313, MET 00423, MET 96500, PCA 02066, PRA 04401, QUE 94200, QUE 97002, and SCO 06040, in research to better understand the regolith of the HED parent body - Vesta - through a combined petrological, compositional and noble gas study. Our main aim is to determine which howardites are truly regolithic - as defined by the presence of solar noble gas components (e.g. solar wind (SW), fractionated solar wind (FSW)) and/or by the presence of planetary components (e.g. Q, HL) associated with foreign clasts of carbonaceous chondrite material within the breccias. Of our ten howardites, four (LEW 85313, MET 00423, PRA 04401 and SCO 06040) show evidence for a regolithic origin, with noble gas ratios indicating the presence of trapped components. Howardites PRA 04401 and SCO 06040 contain significant amounts of CM type carbonaceous chondrite material, and these samples are dominated by a planetary component similar to that observed in CM meteorites Murchison and Maribo. Overall, we find evidence for two regolithic groups with different release trends: (1) SW/FSW component dominated howardites (LEW 85313 and MET 00423), where SW/FSW is dominant at low temperature releases, and less pronounced at higher temperatures; (2) Planetary component dominated howardites (PRA 04401 and SCO 06040) that also contain SW/FSW - the planetary component is associated with incorporated carbonaceous chondrite material, and is dominant at the mid-temperature release. The remaining six howardites EET 83376, EET 99408, MET 96500, PCA 02066, QUE 94200, and QUE 97002, are dominated by cosmogenic noble gases, and are not considered regolithic. Previous work by Warren et al. (2009) suggested that high siderophile element contents (specifically nickel (Ni) > 300 ?g/g) were a regolith indicator for howardites, in addition to restricted Al2O3 contents (8-9 wt.%) representing a eucrite/diogenite mixing ratio of 2:1 as indicative of an ancient well-mixed regolith. These parameters were based on five 'gas-rich' howardites. However, we find no obvious correlation between these parameters and SW/FSW or planetary noble gas content in our howardite samples. We conclude that howardite regolith parameters are not as simple as those defined by Warren et al. (2009), where three of the five howardites used contained foreign CM material, which may have caused a bias in their defined parameters. We conclude that sideophile abundances alone cannot be used to determine the regolithic nature of a sample: noble gas analysis remains a key parameter, where it is important to distinguish between planetary-dominated and SW-dominated regolithic howardites.

Cartwright, J. A.; Ott, U.; Mittlefehldt, D. W.; Herrin, J. S.; Herrmann, S.; Mertzman, S. A.; Mertzman, K. R.; Peng, Z. X.; Quinn, J. E.

2013-03-01

129

Noble Gases and Siderophile Elements in the Mantle: Unconventional Experimental Results and Their Implications for Chemical Geodynamics  

Microsoft Academic Search

Recent and ongoing experimental studies reveal unexpected behavior of noble gases and siderophile elements that may affect future geodynamic interpretations. Ar-uptake experiments on mantle minerals provide insight into Ar compatibility (solubility) and diffusivity in these phases. Contrary to expectation, solubility results suggest that Ar behaves as a compatible element during mantle melting, favoring residence in point defects in minerals over

E. B. Watson; L. A. Hayden; J. B. Thomas; D. J. Cherniak

2007-01-01

130

A Complex Exposure History of the Gold Basin L4-Chondrite Shower from Cosmogenic Radionuclides and Noble Gases  

NASA Technical Reports Server (NTRS)

Cosmogenic radionuclides and noble gases in samples of the Gold Basin L-chondrite shower indicate a complex exposure history, with a first stage exposure on the parent body, followed by a second stage of approx. 19 Myr in a meteoroid 3-4 m in radius. Additional information is contained in the original extended abstract.

Welten, K. C.; Nishiizumi, K.; Caffee, M. W.; Masarik, J.; Wieler, R.

2001-01-01

131

Shock-implanted noble gases. II - Additional experimental studies and recognition in naturally shocked terrestrial materials  

NASA Astrophysics Data System (ADS)

The process by which ambient gases can be implanted into silicates by shocks was investigated by analyzing the noble-gas content of several experimentally and naturally shocked silicate samples. The retentivity of shock-implanted gas during stepwise heating in the laboratory was defined in terms of two parameters, namely, the activation energy for diffusion and the extraction temperature at which 50 percent of the gas is released, both of which correlate with the shock pressure. The experiments indicate that, with increasing shock pressure, gas implantation occurs through an increasing production of microcracks/defects in the silicate lattice. The degree of annealing of these defects control the degree of diffusive loss of implanted gas.

Bogard, D.; Horz, F.; Johnson, P.

1989-06-01

132

On segregation of noble gases in water-based Single Bubble Sonoluminescence  

NASA Astrophysics Data System (ADS)

A long-standing issue in the field of long time stable water based single bubble sonoluminescence has been the close similarity of the spectra to that of blackbody radiation. Looking for the effects of possible segregation of noble gases has been suggested as a means to investigate whether the similarity is just a weird coincidence with the bubbles being on the whole transparent to their own radiation. We have investigated spectra from bubbles seeded with various mixtures of helium and neon with xenon and argon using a novel transformation that allows for a single parameter characterization of the spectra, with the surprising result that although no trace of segregation is found, the radiation seems to be highly thermalized in all cases.

Levinsen, Mogens

2011-03-01

133

A theoretical study of 30 to 50 angstrom noble gas heavy ion lithography  

SciTech Connect

The feasibility of using heavy noble gas ions to etch 30 to 50 {Angstrom} wide lines in polymethylmethacrylate (PMMA) on a silicon substrate was investigated. The TRIM91 computer code was used to model point sources of neon, argon, xenon, krypton, or uranium ions penetrating a two-dimensional geometry consisting of a 50 {Angstrom} layer of PMMA over a 50 {Angstrom} layer of silicon. For ions with a kinetic energy less than 500 e, the energy deposition is so confined that the proximity effect is virtually nonexistent. These and other considerations indicate that heavy noble gas ions may be ideal for etching angstrom-level features in this geometry.

Nelson, C.B.; Makowitz, H.

1994-02-01

134

Atmospheric noble gases as tracers of biogenic gas dynamics in a shallow unconfined aquifer  

NASA Astrophysics Data System (ADS)

Atmospheric noble gases (NGs) were used to investigate biogenic gas dynamics in a shallow unconfined aquifer impacted by a crude oil spill, near Bemidji, MN. Concentrations of 3,4He, 20,22Ne, 36,40Ar, Kr, and Xe were determined for gas- and aqueous-phase samples collected from the vadose and saturated zones, respectively. Systematic elemental fractionation of Ne, Ar, Kr, and Xe with respect to air was observed in both of these hydrogeologic zones. Within the vadose zone, relative ratios of Ne and Ar to Kr and Xe revealed distinct process-related trends when compared to corresponding ratios for air. The degree of NG deviation from atmospheric concentrations generally increased with greater atomic mass (i.e., ?Xe > ?Kr > ?Ar > ?Ne), indicating that Kr and Xe are the most sensitive NG tracers in the vadose zone. Reactive transport modeling of the gas data confirms that elemental fractionation can be explained by mass-dependent variations in diffusive fluxes of NGs opposite to a total pressure gradient established between different biogeochemical process zones. Depletion of atmospheric NGs was also observed within a methanogenic zone of petroleum hydrocarbon degradation located below the water table. Solubility normalized NG abundances followed the order Xe > Kr > Ar > Ne, which is indicative of dissolved NG partitioning into the gas phase in response to bubble formation and possibly ebullition. Observed elemental NG ratios of Ne/Kr, Ne/Xe, Ar/Xe, and Kr/Xe and a modeling analysis provide strong evidence that CH4 generation below the water table caused gas exsolution and possibly ebullition and carbon transfer from groundwater to the vadose zone. These results suggest that noble gases provide sensitive tracers in biologically active unconfined aquifers and can assist in identifying carbon cycling and transfer within the vadose zone, the capillary fringe, and below the water table.

Jones, Katherine L.; Lindsay, Matthew B. J.; Kipfer, Rolf; Mayer, K. Ulrich

2014-03-01

135

Noble gases in the Oceanic Crust: Preliminary results from ODP Hole 1256D  

NASA Astrophysics Data System (ADS)

Noble gas isotopes and abundance ratios have been extensively used as tracers of oceanic mantle sources and fluxes. Most of the existing data are from seafloor basalt glasses and hydrothermal fluids, and there are very few studies of noble gases in the oceanic crust, which is an important component in global subduction flux estimates. In an effort to determine the relative contributions of mantle, radiogenic, and atmospheric/hydrothermal noble gas components in the ocean crust, we have performed helium, neon and argon measurements on a suite of gabbros and granoblastic dikes collected during IODP Expeditions 312 and 335 to Hole 1256D, a deep crustal borehole drilled into 15 Ma ocean crust formed at the East Pacific Rise during an episode of superfast spreading (>200 mm/yr). All measurements were carried out by coupled vacuum crushing and melting of whole rock samples, in order to determine the distribution of noble gases within the ocean crust. Total helium abundances in the gabbros range from 0.46 to 1.22 micro cc STP/gram, which is 2 to 5 times higher than literature data, all of which are from the slow spreading Southwest Indian Ridge (Kumagai et al., 2003; Moreira et al., 2003). These strikingly higher helium concentrations place constraints on the thermal crustal history (due to rapid helium diffusivity) and are assumed to reflect fundamentally different emplacement/degassing processes within crust formed at a super fast spreading rate. Crushing releases 12-25 % of the total helium in the gabbros demonstrating that most of the helium resides in the solid mineral phases. Contact metamorphosed granoblastic dikes have total helium contents lower than the gabbros (typically ~ 0.15 micro cc STP/gram), but significantly higher than the assumed degassed basaltic protolith, thus suggesting that metamorphism actually adds helium to the crust, an important hypothesis that requires further testing. The helium isotopes obtained by crushing of both the gabbros and granoblastic dikes are dominated by mantle helium, with average 3He/4He = 6.5 .2 times atmosphere (Ra). This value is at the low end of the range for normal Pacific MORB helium data and is interpreted to represent the mantle source. 3He/4He values obtained by melting are slightly lower and are consistent with a small radiogenic component, and suggest that helium will be useful for geochronology of the ocean crust. In contrast with the helium isotopic data, neon and argon are dominated by atmospheric isotopic compositions, which is consistent with mineralogical and petrological evidence for extensive alteration of the crust. Crushing in vacuum releases a larger fraction of total neon and argon (28 to 64 %), suggesting that atmospheric/hydrothermal/alteration neon and argon are loosely bound, most likely in secondary alteration minerals. Small mantle argon isotopic components are only found in a few samples, and only during the heating experiments. These data suggest that the atmospheric noble gas components are most likely to be expelled during subduction of the ocean crust.

Kurz, M. D.; Curtice, J. M.; IODP Expedition 335 Science Party

2011-12-01

136

A noble gas profile across a Hawaiian mantle xenolith: Coexisting accidental and cognate noble gases derived from the lithospheric and asthenospheric mantle beneath Oahu  

NASA Astrophysics Data System (ADS)

A noble gas profile across a garnet pyroxenite xenolith from Salt Lake Crater, Oahu, Hawaii, provides information about the scale and origin of noble gas heterogeneities within such rocks. Variations in both absolute and relative noble gas concentrations are large and comparable to those observed between individual Salt Lake Crater pyroxenite xenoliths. 3He/4He varies from 7.7 to 9.4 times the atmospheric value (Ra) and correlates inversely with 40Ar/36Ar, which ranges between 4100 and 9700. Neon krypton and xenon isotopes are uniform and indistinguishable from air, with the exception of excess 129Xe. Overall, the observed noble gas compositions reflect a derivation from depleted MORB-type mantle sources. The spatial distribution of noble gas signatures within the xenolith and the observed correlation between helium and argon isotopes suggest the presence of two different noble gas components which are trapped in different phases and are unevenly distributed within the xenolith. 40Ar/36Ar and 1/36Ar correlate inversely, indicating that atmospheric contamination is insignificant. Hence, the observed isotopic variations reflect mixing of two mantle-derived noble gas components. Correlations between He?Ar isotopes and CO2/H2O in different pyroxenites from Salt Lake Crater, including our sample, reveal that the first component is characterized by highly radiogenic helium and argon isotopes and related to abundant secondary CO 2-rich fluid inclusions. Given the high diffusivity of He at mantle temperatures (Hart, 1984), the observed helium isotope heterogeneities on a sub-mm scale require that the fluids were introduced concurrently with eruption. This interpretation is supported by the low entrapment depths of fluid inclusions in Salt Lake Crater pyroxenites (<30 km; Murck et al., 1978). This implies that the fluids are genetically related to the host magma itself and reflect its composition. The second noble gas component is interpreted as being magmatic, i.e., cognate to the basaltic magma from which the pyroxenite precipitated within the mantle. It is proposed that this component resides inside the mineral lattices and was trapped during magmatic crystallization. Our results indicate that the depleted lithospheric mantle source of the post-erosional host magma (Honolulu Volcanic Series) is characterized by 40Ar/36Ar ? 10000, R/Ra ? 7.5, and excesses in 129Xe. Noble gas signatures of the asthenospheric mantle source parental to the pyroxenite-producing magma are less radiogenic with respect to these isotopes. Combining noble gas and strontium, neodymium, and lead isotope evidence, we propose that the asthenosphere beneath Oahu was originally similar to depleted MORB-type mantle, but became slightly modified by noble gases and other incompatible trace elements derived from the Hawaiian mantle plume prior to partial melting. This study provides evidence that noble gas isotopes and solid radiogenic isotopes are coupled in the mantle sources of basalts (e.g., Allgre et al., 1983), but decoupled in xenoliths (e.g., Vance et al., 1989).

Rocholl, A.; Heusser, E.; Kirsten, T.; Oehm, J.; Richter, H.

1996-12-01

137

ULTRAHIGH SENSITIVITY HEAVY NOBLE GAS DETECTORS FOR LONG-TERM MONITORING AND MONITORING AIR  

EPA Science Inventory

A Georgia Institute of Technology/Argonne National Laboratory team will develop and demonstrate novel ultrahigh sensitivity heavy noble gas (krypton, xenon, and radon) detectors for long-term monitoring of spent fuel and TRU waste, as well as for distinguishing background radon a...

138

The delivery og noble gases and nitrogen to erth by extraterrestrial matter  

NASA Astrophysics Data System (ADS)

Micrometeorites represent the largest mass flux of extraterrestrial matter on Earth, and could have contributed significantly to the budget of volatile and biogenic elements at the Earth's surface in the past [1]. These volatiles which are delivered directly the external reservoirs of the Earth and could significantly contribute to it need to have their flux and the processes of delivery to be documented. We present coupled noble gas (He, Ne, Ar) and nitrogen isotope analyses of Antarctic micrometeorites (AMMs) that are representative of the range of textures observed among AMMs (crystalline, fine-grained scoriaceous, cosmic spherules). Fragments weighting a few ?g were were analyserd by CO_2-laser exrtraction-static mass spectrometry [12].Antarctic micrometeorites (AMMs) have variable, and sometimes very high noble gas contents up to one order of magnitude higher than Orgueil (ref). In contrast nitrogen is in low abundance in AMMs (about one tenth of chondritic) and does not correlate well with indexes of atmospheric entry. The AMM nitrogen content correlates well with radiogenic ^4He and 40Ar (Table 1, Fig. 1) whereas primordial 3He, 20Ne and 36Ar correlate among each others but no correlation between the two groups. is observed between N, ^4He, 40Ar on the one hand, and primordial 3He, 20Ne and 36Ar on the other hand (Table 1). This lack of correlation demonstrates that each set of element/isotopes is hosted by a different phase, which could be silicates in the case of N as the parents of 4He and 40Ar are indeed hosted by silicates. The major host phase of nitrogen in carbonaceous chondrites and IDPs is organic, so that the different behavior of nitrogen relative to noble gases (which are also likely to be hosted by an organic phase) in AMMs suggests different host phases, the nitrogen one being disrupted more easily during atmospheric entry. In order to quantify the release of volatile elements from micrometeorites during atmospheric entry, we have attempted heating experiments in which < 1 mm fragments of Orgueil were pulse-heated in 1 atm. air furnace at 1350^oC during 2, 5, 10 and 120 s and subsequently analyzed following the same procedure. preliminary results indicate quantitative degassing in the order He>N_2>Ne>Ar, thus confirming the the more labile phase hosting nitrogen.

Marty, B.; Engrand, C.; Toppani, A.; Libourel, G.

2003-04-01

139

Ancient carbon and noble gas fractionation. [in carbonaceous meteorites and terrestrial kerogen  

NASA Technical Reports Server (NTRS)

Noble gases in ancient terrestrial kerogen and meteoritic carbonaceous residues are compared in terms of their elemental fractionation with respect to atmospheric and the cosmic reservoirs, respectively. Fractionation factors for the heavy noble gases are almost identical in both types of samples. Therefore, some features of the interaction between carbon phases and noble gases in very different environments of origin appear to be similar. These findings underscore the plausibility of the meteoritic carbonaceous residues as a noble gas carrier and as a novel vehicle for achieving the elemental fractionation required to derive the planetary noble gas pattern from cosmic abundances.

Frick, U.; Chang, S.

1977-01-01

140

Using noble gases in the pore water of ocean sediments to characterize CH4 seepage off the coast of New Zealand  

NASA Astrophysics Data System (ADS)

Newly developed analytical techniques to determine the abundances of noble gases in sediment pore water [1, 5] allow noble-gas concentrations and isotope ratios to be measured easily and routinely in unconsolidated lacustrine sediments [6, 7]. We applied these techniques for the first time to ocean sediments to investigate an active cold methane seepage system located in the South Pacific off the coast of New Zealand using 3He-4He ratios determined in the sediment pore water. Our results [8] show that more 3He-rich fluids are released in the vicinity of the Pacific-Australian subduction zone than at the forearc stations located closer to the New Zealand coast. However, the 3He-4He isotope signature in the sediment column indicates that only a minor part of the He emanating from deeper strata originates from a (depleted) mantle source. Hence, most He in the pore water is produced locally by the radioactive decay of U and Th in the sediment minerals or in the underlying crustal rocks. Such an occurrence of isotopically heavy crustal He also suggests that the source of the largest fraction of methane is a near-surface geochemical reservoir. This finding is in line with a previous ?13C study in the water column which concluded that the emanating methane is most likely of biological origin and is formed in the upper few meters of the sediment column [2]. The prevalence of isotopically heavy He agrees well with the outcome of other previous studies on island arc systems [3, 4] which indicate that the forearc regions are characterized by crustal He emission, whereas the volcanic arc region is characterized by the presence of mantle He associated with rising magma. References [1] Brennwald, M. S., Hofer, M., Peeters, F., Aeschbach-Hertig, W., Strassmann, K., Kipfer, R., and Imboden, D. M. (2003). Analysis of dissolved noble gases in the pore water of lacustrine sediments. Limnol. Oceanogr.: Methods 1, 51-62. [2] Faure, K., Greinert, J., Schneider von Deimling, J., McGinnis, D., Kipfer, R., Linke, P. (2010). Methane seepage along the Hikurangi Margin of New Zealand: Geochemical and physical data from the water column, sea surface and atmosphere. Mar. Geol. 272, 170-188. [3] Sano, Y., Nakajima, J. (2008). Geographical distribution of 3He-4He ratios and seismic tomography in Japan. Geochem. J. 42, 51-60. [4] Sano, Y., Wakita, H., Giggenbach, W., 1987. Island arc tectonics of New Zealand manifested in helium isotope ratios. Geochim. Cosmochim. Acta 51 (7), 1855-1860. [5] Tomonaga, Y., Brennwald, M. S., Kipfer, R. (2011). An improved method for the analysis of dissolved noble gases in the pore water of unconsolidated sediments. Limnol. Oceanogr.: Methods 9, 42-49. [6] Tomonaga, Y., Brennwald, M. S., Kipfer, R. (2011). Spatial distribution and flux of terrigenic He dissolved in the sediment pore water of Lake Van (Turkey). Geochim. Cosmochim. Acta 75 (10), 2848-2864. [7] Tomonaga, Y., Blttler, R., Brennwald, M. S., Kipfer, R. (2012). Interpreting noble-gas concentrations as proxies for salinity and temperature in the world's largest soda lake (Lake Van, Turkey). J. Asian Earth Sci., 59, 99-107. [8] Tomonaga, Y., Brennwald, M. S., Kipfer, R. Using noble gases in ocean sediments to characterize active methane seepage off the coast of New Zealand. Mar. Geol., submitted.

Tomonaga, Yama; Brennwald, Matthias S.; Kipfer, Rolf

2013-04-01

141

Analysis of high frequency breakdown of noble gases in A MEMS-based Rb87 lamp for miniaturized passive rubidium atomic clock  

Microsoft Academic Search

MEMS-based atomic clock is being studied by some investigators and we are proposing and developing a miniaturized pass rubidium atomic clock, in which Rb-87 lamp is the first microdevice of the system. To make the lamp give off light, noble gas is needed to fill the lamp. In this paper, we study the high frequency breakdown of noble gases in

Jie Chen; Tao Guo; Hang Guo

2009-01-01

142

Dating and tracing groundwater resources in central Qubec with noble gases, 14C and water chemistry  

NASA Astrophysics Data System (ADS)

Canada water supply is derived mainly from lakes and rivers while groundwater accounts for less than 30% of the demand. Climatic and anthropogenic stress is endangering this natural resource. This study is part of a Quebec-funded program to characterize groundwater resources from major basins to ensure adequate water quality and management. The Bcancour River catchment area, 200 km NE of Montral, is studied for this purpose. The region extends from the Appalachian Mts. down to the St. Lawrence River. Water chemistry shows the occurrence of Ca,Na-HCO3, Ca-HCO3, Na-HCO3 and NaCl waters, mainly recharged in the Appalachians and flowing to the St. Lawrence River. Aquifers are also recharged locally through Quaternary sandy deposits throughout the plain. Main aquifers are found both in unconfined and confined Quaternary sands intercalated with clays, and also locally in fractured Ordovician carbonates. To identify groundwater flow paths and to estimate water residence times, a multi-isotopic study involving noble gases, 14C and U, Th isotopes was initiated. Noble gas preliminary results were obtained on two transects, one along the downward flow path and the second perpendicular to the first, along a deeper sinclinorium with NaCl waters (TDS =170-705 mg/L). The 3He/4He ratios versus 4He/20Ne clearly points to mixing between three water bodies. The first has been recharged very recently displaying a near-atmospheric ratio of 0.79 Ra (Ra=atmospheric 3He/4He ratio of 1.386 x 10-6) and a 4He/20Ne of 0.2 close to the Air Saturated Water value, i.e. the ratio of atmospheric He and Ne dissolved in groundwater. The second water body is slightly older and shows the occurrence of tritiogenic 3He (3Hetri) excesses up to 1.07x10-13 ccSTP/g. These waters are found along the transect parallel to the main flow path. Using a local tritium decay curve and measured 3Hetri, an age of 19-20 years is suggested. The third water body contains large amounts of radiogenic 4He produced by U and Th decay in aquifer rocks up to 4.48x10-5 ccSTP/g. These waters are found close to the Appalachian recharge and in the transversal sinclinorium. They are from relatively deep wells (50 m depth), likely tapping the Ordovician carbonate basement. A simple in situ U-Th-4He age model gives ages of 2.0 to 6.6 Ma, which might suggest either: (1) the occurrence of isolated pockets of old water in the fractured basement or (2) mixing with deeper fossil brines containing large amounts of radiogenic 4He occurring in the Bcancour area. 14C measurements, in progress, should be helpful in calibrating the He age model and to test whether a 4He source external to aquifers might exist. Preliminary calculated paleotemperatures using atmospheric noble gases suggest values varying between 0 to 7 C. The higher temperature represents actual recharge conditions during spring. The lower temperatures might correspond to Holocene waters recharged during the last deglaciation or contribution from recent glacial meltwater.

Vautour, G.; Pinti, D. L.; Castro, M. C.; Barbecot, F.; Larocque, M.; Hall, C. M.

2011-12-01

143

Isotopic Composition of Trapped and Cosmogenic Noble Gases in Several Martian Meteorites  

NASA Technical Reports Server (NTRS)

Isotopic abundances of the noble gases were measured in the following Martian meteorites: two shock glass inclusions from EET79001, shock vein glass from Shergotty and Y793605, and whole rock samples of ALH84001 and QUE94201. These glass samples, when combined with literature data on a separate single glass inclusion from EET79001 and a glass vein from Zagami, permit examination of the isotopic composition of Ne, Ar, Kr, and Xe trapped from the Martian atmosphere in greater detail. The isotopic composition of Martian Ne, if actually present in these glasses, remains poorly defined. The Ar-40/Ar-36 ratio of Martian atmospheric Ar may be much less than the ratio measured by Viking and possibly as low as approx. 1900. The atmospheric Ar-36/Ar-38 ratio is less than or equal to 4.0. Martian atmospheric Kr appears to be enriched in lighter isotopes by approx. 0.4%/amu compared to both solar wind Kr and to the Martian composition previously reported. The Martian atmospheric Ar-36/Xe-132 and Kr-84/Xe-132 Xe elemental ratios are higher than those reported by Viking by factors of approx. 3.3 and approx. 2.5, respectively. Cosmogenic gases indicate space exposure ages of 13.9 +/- 1 Myr for ALH84001 and 2.7 +/- 0.6 Myr for QUE94201. Small amounts of Ne-21 produced by energetic solar protons may be present in QUE94201, but are not present in ALH84001 or Y793605. The space exposure age for Y793605 is 4.9 +/- 0.6 Myr and appears to be distinctly older than the ages for basaltic shergottites.

Garrison, Daniel H.; Bogard, Donald D.

1997-01-01

144

Analytical equation of state with three-body forces: Application to noble gases  

SciTech Connect

We developed an explicit equation of state (EOS) for small non polar molecules by means of an effective two-body potential. The average effect of three-body forces was incorporated as a perturbation, which results in rescaled values for the parameters of the two-body potential. These values replace the original ones in the EOS corresponding to the two-body interaction. We applied this procedure to the heavier noble gases and used a modified Kihara function with an effective Axilrod-Teller-Muto (ATM) term to represent the two- and three-body forces. We also performed molecular dynamics simulations with two- and three-body forces. There was good agreement between predicted, simulated, and experimental thermodynamic properties of neon, argon, krypton, and xenon, up to twice the critical density and up to five times the critical temperature. In order to achieve 1% accuracy of the pressure at liquid densities, the EOS must incorporate the effect of ATM forces. The ATM factor in the rescaled two-body energy is most important at temperatures around and lower than the critical one. Nonetheless, the rescaling of two-body diameter cannot be neglected at liquid-like densities even at high temperature. This methodology can be extended straightforwardly to deal with other two- and three-body potentials. It could also be used for other nonpolar substances where a spherical two-body potential is still a reasonable coarse-grain approximation.

Ro, Fernando del, E-mail: fdr@xanum.uam.mx; Daz-Herrera, Enrique; Guzmn, Orlando; Moreno-Razo, Jos Antonio [Departamento de Fsica, Universidad Autnoma Metropolitana, Iztapalapa, Apdo 55 534, Mxico DF, 09340 (Mexico)] [Departamento de Fsica, Universidad Autnoma Metropolitana, Iztapalapa, Apdo 55 534, Mxico DF, 09340 (Mexico); Ramos, J. Eloy [Colegio de Ciencia y Tecnologa, Universidad Autnoma de la Ciudad de Mxico, Mexico DF (Mexico)] [Colegio de Ciencia y Tecnologa, Universidad Autnoma de la Ciudad de Mxico, Mexico DF (Mexico)

2013-11-14

145

Analytical equation of state with three-body forces: Application to noble gases  

NASA Astrophysics Data System (ADS)

We developed an explicit equation of state (EOS) for small non polar molecules by means of an effective two-body potential. The average effect of three-body forces was incorporated as a perturbation, which results in rescaled values for the parameters of the two-body potential. These values replace the original ones in the EOS corresponding to the two-body interaction. We applied this procedure to the heavier noble gases and used a modified Kihara function with an effective Axilrod-Teller-Muto (ATM) term to represent the two- and three-body forces. We also performed molecular dynamics simulations with two- and three-body forces. There was good agreement between predicted, simulated, and experimental thermodynamic properties of neon, argon, krypton, and xenon, up to twice the critical density and up to five times the critical temperature. In order to achieve 1% accuracy of the pressure at liquid densities, the EOS must incorporate the effect of ATM forces. The ATM factor in the rescaled two-body energy is most important at temperatures around and lower than the critical one. Nonetheless, the rescaling of two-body diameter cannot be neglected at liquid-like densities even at high temperature. This methodology can be extended straightforwardly to deal with other two- and three-body potentials. It could also be used for other nonpolar substances where a spherical two-body potential is still a reasonable coarse-grain approximation.

del Ro, Fernando; Daz-Herrera, Enrique; Guzmn, Orlando; Moreno-Razo, Jos Antonio; Ramos, J. Eloy

2013-11-01

146

Noble Gases on Metal Surfaces: New Insights on Adsorption Site Preference  

NASA Astrophysics Data System (ADS)

Experiments have previously found that noble gases (Kr, Xe) adsorb on low-coordination atop sites on several different metal surfaces, rather than on high-coordination hollow sites. This unexpected preference for low-coordination sites has been previously ascribed to reduced Pauli repulsion mostly due to exchange energy at the atop site, based on density functional theory calculations within the local density approximation (LDA). In contrast, our calculations using non-local van der Waals (vdW-DF) density functional show that site preference is due to a delicate balance between the electrostatics which favor the hollow site and kinetic energy which favors the atop site; exchange-correlation energies has a very little role. Moreover, we find, using LDA, GGA, and vdW-DF functionals, that the hollow site is a saddle point of index 1 or 2 on the 2-dimensional potential energy surface, while the atop site is the only true minimum. Therefore, the reason that hollow site occupation is not observed is that it is a transition state and so has a very short life-time. Our results show that the inclusion of non-local vdW interactions is crucial for obtaining results in quantitative agreement with experiments for adsorption energies, equilibrium distances, and vibrational energies.

Chen, De-Li; Al-Saidi, Wissam; Johnson, Karl

2012-02-01

147

Noble gases in individual chondrules of the Allende CV3 chondrite  

NASA Astrophysics Data System (ADS)

We analyzed noble gases in nine individual chondrules, an assemblage of small chondrules, and four whole-rock samples of the Allende CV3 chondrite. Major elements were also determined for five chondrules. The cosmic ray exposure ages are calculated from cosmogenic 3He to be 5.17 0.38 and 5.15 0.25 Myr for the averages of the chondrules and whole rocks, respectively, showing no significant pre-exposure evidence for the studied chondrules. Large amounts of 36Ar, 80,82Kr, and 128Xe produced by neutron capture are observed in most samples; the abundances of these nuclides are correlated among the samples. The epithermal neutron flux and neutron slowing down density are calculated based on [80Kr]n, from which a sample depth of about 30 cm can be calculated. The measured chondrules contain variable amounts of radiogenic 129Xe. The abundance ratios of radiogenic 129Xe to neutron capture-produced 128Xe are rather constant among the studied chondrules; four chondrules give more precise ratios at the high-temperature fractions, ranging from 1920 80 to 2280 140, which corresponds to a time difference of 3.9 2.4 Myr. It is noticeable that most chondrules also contain 244Pu-derived fission Xe. The average 244Pu/238U ratio for nine chondrules is 0.0069 0.0018, which agrees well with the preferred ratio reported for chondrites.

Miura, Yayoi N.; Nagao, Keisuke; Kimura, Makoto

2014-06-01

148

Measuring radioactive noble gases by absorption in polycarbonates and other organics: From radon indoors to nuclear safety  

NASA Astrophysics Data System (ADS)

The report summarizes recent research and practice of using materials with high absorption ability to noble gases to measure their radioactive isotopes. Most of the studies employ bisphenol-A based polycarbonates, because of their remarkably high absorption ability to noble gases. This is the material of which commercial CDs/DVDs are made and they may serve as serendipitous, already available in dwellings, radon and thoron detectors. We present the essence of the gathered experimental evidence that the CD/DVD method can successfully address some long-lasted problems in radon dosimetry: The first is making sufficiently precise retrospective 222Rn dosimetry for the purposes of epidemiological studies and risk estimation. The second is rapid identification of buildings with radon problem. We demonstrate how this can be used to develop an integrated approach to the radon problem. Within this approach detection, diagnostic and mitigation are considered as an unified whole, and the interval between the decision to provide disks for analysis and the complete mitigation of the building, if radon problem is identified, is short. Besides radon and thoron, bisphenol-A based polycarbonates were successfully used to measure 85Kr and 133Xe for the purposes of the effluents control and nuclear safety of nuclear installations. The perspectives to employ other organic materials in which noble gases are highly soluble for measurement of their radioactive isotopes are also discussed.

Pressyanov, Dobromir S.

2013-07-01

149

Photoabsorption to Stark Rydberg States of Heavy Noble Gas Atoms: Testing Limits of Closed Orbit Theory  

Microsoft Academic Search

The selective dramatic effects of a dc electric field on the photoabsorption spectrum of Rydberg states and the associated recurrence strengths and closed orbits are studied in heavy noble gas atoms. Using collinear atom-laser beam spectroscopy, complex scaled-energy photoabsorption spectra are mapped experimentally in high resolution for pi and sigma transitions from the ns[3\\/2] and ns[1\\/2] metastable states, formed by

Heric Flores-Rueda; Matthew L. Keeler; David Wright; Thomas J. Morgan

2003-01-01

150

Analysis of noble gases in water using a quadrupole mass spectrometer in static mode  

Microsoft Academic Search

A quadrupole-based mass spectrometer used in static mode has been employed to determine noble gas concentrations of water samples by isotope dilution. Water samples are degassed and spiked with minor isotopes of each noble gas. After separation of the various gas components, the isotopic ratios are measured in the mass spectrometer. Because a spike is added to each sample, the

Jason C. Poole; Gavin W. McNeill; Stephen R. Langman; Frank Dennis

1997-01-01

151

Lower mantle contribution to the genesis of carbonatites: the noble gases and carbon isotopic evidence  

NASA Astrophysics Data System (ADS)

It has been demonstrated that only 20 to 40% of the subducted CO2 is extracted by decarbonatation of descending slab. This, and the fact that some carbonatites exhibit HIMU-like Pb, Nd and Sr isotopic signatures, led to models invoking a carbonatite origin by partial melting of ancient subducted carbonated oceanic crust. A recycled carbon origin for diamonds has also been suggested. However the mantle is the largest carbon reservoir of the Earth and a non-recycled (i.e. primordial) origin for the carbon in carbonatites cannot be discarded. Some of the Cape Verde oceanic carbonatites present low 4He/3He ratios (down to 46,700; R/Ra up to 15.5) demonstrating that they sample a reservoir characterized by low time-integrated (U+Th)/3He. Such a reservoir, being clearly distinct from the crust or from the upper mantle sampled by the 60 000 km long oceanic ridge system, is thought to be localized in the lower mantle. For continental carbonatites several authors has also interpreted noble gases isotopic compositions as reflecting the contribution of a reservoir with time-integrated (U+Th)/(3He, 22Ne) and 40K/36Ar lower than the upper mantle, thus endorsing the contribution of the lower mantle [1;2;3]. Some carbonatites are also characterized by 129Xe anomalies relatively to the air (129Xe/130Xe up to 6.94 in Cape Verde). Considering that the recycling of carbonates, eventually characterized by high Te and Ba contents, would with time increase simultaneously the 129Xe and 130Xe, the observed 129Xe anomalies cannot be explained by models calling upon crustal carbonate recycling. We interpret them in terms of an ancient mantle origin by decay of the now extinct 129I. Moreover, experimental work has demonstrated that crustal carbonates are unlikely to be transported to lower mantle depth levels as a consequence of its removal by melting reactions. Thus, all the above described lower mantle signals are indicative of a non-recycled, lower mantle, origin for carbon, unless we admit that, during ascent, deep-seated mantle plumes entrain recycled carbon from the upper mantle. Nevertheless many carbonatites are also characterized by ^13C values (-8.0 to -4.25 per mil in Cape Verde) lighter than those characterizing crustal inorganic carbonates, endorsing the role of primordial carbon to the genesis of carbonatites. Taking into account that a recycled origin for some carbonatites is inescapable from carbon and noble gases signatures [e.g. 4; 5] we conclude that multiple origins (recycled vs. primordial) are possible for the carbon involved in the generation of carbonatitic magmas. Sasada et al. (1997) - Geochim. Cosmochim. Acta, 61: 4219-4228 Marty et al. (1998)- Earth Planet. Sci. Lett., 164: 179-192 Tolstikhin et al. (2002) - Geochim. Cosmochim. Acta, 66: 881-901 Ray et al. (1999) - Earth Planet Sci. Lett., 170; 205-214 Basu & Murty (2006) - Chem. Geol., 234: 236-250 This is a contribution from the FCT/FEDER project PLINT (POCTI/CTA/45802/2002)

Mata, J.; Moreira, M.; Mouro, C.; Ader, M.; Doucelance, R.

2009-04-01

152

Implanted radiogenic and other noble gases in crustal diamonds from Northern Kazakhstan  

NASA Astrophysics Data System (ADS)

Noble gases were extracted in steps from grain size fractions of microdiamonds (less than 100 microns) from the Kokchetav Massif, Northern Kazakhstan, by pyrolysis and combustion. The concentration of He-4 in the diamonds proper (liberated by combustion) shows a 1/r dependence on grain size. For grain diameters greater than 15 microns the concentration also decreases with the combustion step. Both results are clear evidence that He-4 has been implanted into the diamonds from alpha-decaying elements in the surrounding matrix. The saturation concentration of He-4. (5.6 x 10(exp -4) cu cm STP/g) is among the very highest observed in any terrestrial diamonds. Fission xenon from the spontaneous fission of U-238 accompanies the radiogenic He-4; the (136)Xe(sub f)/He-4 ratio of (2.5 +/- 0.3) x 10(exp -9) agrees well with the production ratio of 2.3 x 10(exp -9) expected in a reservoir where Th/U about 3.3. Radiogenic Ar-40 is predominantly (greater than 90%) set free upon combustion; it also resides in the diamonds and appears to have been incorporated into the diamonds upon their formation. He-3, on the other hand is mainly released during pyrolysis and hence is apparently carried by 'contaminants'. The concentration in the diamonds proper is of the order of 4 x 10(exp -12) cu cm STP/g, with a He-3/He-4 ratio of 1 x 10(exp -8). Excess Ne-21, similarly, appears to be present in contaminants as well as in diamonds proper. These two nuclides in the contaminants must have a nucleogenic origin, but it is difficult to explain their high concentrations.

Verchovsky, A. B.; Ott, U.; Begemann, F.

1993-12-01

153

Evaluation of a high-pressure proportional counter for the detection of radioactive noble gases. Master's thesis  

SciTech Connect

This report presents a study of the characteristics of a high-pressure proportional detector for the qualitative and quantitative analysis of radioactive noble gases. Several external sources (Americium 241, Cadmium 109 and Cobalt 57) were used to establish the detector's response at high pressures using argon fill gas. A radioactive xenon gas sample with Xenon 131m and Xenon 133 was used to demonstrate the detector's utility for the analysis of radioactive noble gases. Procedurally, counting gas from a 12.34-liter reservoir was cryo-genically condensed in the 0.197-liter detector volume. Energy calibration was performed using the external sources. The analysis of the internal radioactive xenon gas source was not successful. The Xenon 131M to Xenon 133 concentration was 50% of the planned minimum value, and the Xenon 133 source activity was one hundred times the acceptable level. The associated detector recovery time and space-charge density reduced the efficiency drastically (approx 1%). Occasional unpredictable responses from contaminants adsorbed in the epoxy seals produced excessive numbers of erratic data with the internal noble-gas source.

Lackey, R.E.

1987-01-01

154

H3+ as a trap for noble gases-3: Multiple trapping of neon, argon, and krypton in XnH3+ (n=1-3)  

NASA Astrophysics Data System (ADS)

Recent studies on the formation of XH3+ noble gas complexes have shown strategic implications for the composition of the atmospheres of the giant planets as well as for the composition of comets. One crucial factor in the astrophysical process is the relative abundances of the noble gases versus H3+. It is the context in which the possibility for clustering with more than one noble gas (XnH3+ up to n=3) has been investigated for noble gases X ranging from neon to krypton. In order to assert our results, a variety of methods have been used including ab initio coupled cluster CCSD and CCSD(T), MP2, and density functional BH&HLYP levels of theory. All complexes with one, two, and three noble gases are found to be stable in the Ne, Ar, and Kr families. These stable structures are planar with the noble gases attached to the apices of the H3+ triangle. The binding energy of the nth atom, defined as the XnH3+-->Xn-1H3++X reaction energy, increases slightly with n varying from 1 to 3 in the neon series, while it decreases in the argon series and shows a minimum for n=2 in the krypton series. The origin of this phenomenon is to be found in the variations in the respective vibrational energies. A topological analysis of the electron localization function shows the importance of the charge transfer from the noble gases toward H3+ as a driving force in the bonding along the series. It is also consistent with the increase in the atomic polarizabilities from neon to krypton. Rotational constants and harmonic frequencies are reported in order to provide a body of data to be used for the detection in laboratory prior to space observations. This study strongly suggests that the noble gases could be sequestered even in an environment where the H3+ abundance is small.

Pauzat, F.; Ellinger, Y.; Pilm, J.; Mousis, O.

2009-05-01

155

New model concering the hollow cathode electric discharge (HCED) as a spectral source in mixed noble gases and metal vapors  

NASA Astrophysics Data System (ADS)

This work concerns with the excitation and ionization processes in the cathode region of the hollow cathode abnormal glow discharge, like in a genetically abnormal glow discharge in mixture of noble gases and metal vapors. The proposed model takes into account the ionic and atomic population of metal vapors, the metastables population of predominant buffer gas and of the ion population of the gas mixture, while the other models, reported in the literature don't take into account the last two populations. This model is qualitatively experimentally attested.

Iova, Iancu; Bazavan, M.; Biloiu, Costel; Ilie, Gheorghe; Biloiu, Ioana

2001-06-01

156

Neutron Capture Isotopes in the Martian Regolith and Implications for Martian Atmospheric Noble Gases  

NASA Astrophysics Data System (ADS)

Impact-produced glasses in some martian meteorites have trapped significant amounts of the recent martian atmosphere. From literature data, we estimate that 9% of the trapped 80Kr in these meteorites was produced from neutron capture on 79Br. Estimates of neutron fluences made from 80Kr and 149Sm for bulk samples of meteorite EET79001 indicate that 80Kr excesses in the impact glass were not produced in situ. Theoretical calculations independently predict production of a large neutron-capture component of 80Kr and 36Ar in the martian regolith, and part of this component presumably escaped into the martian atmosphere. These calculations were made by using the Los Alamos High-Energy Transport Code to calculate the fluxes of galactic cosmic ray (GCR)-produced thermal neutrons as a function of depth in the uppermost 500 g cm -2 of the martian surface, and by adopting average Cl, Br, and I concentrations of the upper martian surface of 0.3%, 20 ppm, and 0.5 ppm, respectively. Combining these data with the appropriate neutron-capture cross sections, we calculate Mars global production rates of 80Kr n=2.410 16atoms sec -1, 36Ar n=5.510 18 atoms sec -1, and 128Xe n=310 13 atoms sec -1. Calculated global production rates of spallogenic 80Kr sp, and 36Ar sp, are smaller by factors of 770 and 29, respectively. It would require 330 Myr to produce an amount of 80Kr n equivalent to the amount inferred to be present today in the martian atmosphere (2.510 32 atoms). Production of these neutron-capture components probably has occurred over the past 4 Gyr, as only an atmospheric pressure substantially higher than today's would appreciably decrease the neutron flux in the regolith. Thus, most of the neutron-capture noble gases produced over time probably remain in the martian regolith and would make sensitive indicators of the time period a sample has resided near the martian surface. Assuming mixing of the martian surface to an average depth of 100 m, the predicted average regolith concentrations of 80Kr n, 36Ar n, and 128Xe n are 410 -9 cm -3 g -1, 110 -6 cm 3 g -1, and 510 -12 cm 3 g -1, respectively. If similar fractions of these neutron-capture isotopes have escaped into the atmosphere, they would comprise 3% and 0.2% of the present atmospheric inventories of 36Ar and 128Xe, respectively. The fractional excess of 80Kr n in ancient martian meteorite ALH84001 appears similar to that in shock-glass phases of young shergottite meteorites. If ALH84001 acquired its atmospheric gases 4 Gyr ago, this implies that, prior to that time, halogens were greatly concentrated at the martian surface by crustal formational and weathering processes, impacts efficiently degassed the regolith, and Mars did not have a significant atmosphere to shield the surface.

Rao, M. N.; Bogard, D. D.; Nyquist, L. E.; McKay, D. S.; Masarik, J.

2002-04-01

157

Noble gases in submarine pillow basalt glasses from the Lau Basin: Detection of a solar component in backarc basin basalts  

NASA Astrophysics Data System (ADS)

Noble gas elemental and isotopic abundances have been analysed in eight samples of youthful basaltic glass dredged from three different locations within the Lau Backarc Basin: (1) the King's Triple Junction, (2) the Central Lau Spreading Center at 18 deg S and (3) the Eastern Lau Spreading Center at 19 deg S. Samples from the Lau central and eastern spreading centres have Mid-Ocean Ridge Basalt (MORB)-like helium isotopes ratios of approximately 1.2 x 10(exp -5) (8.5 R/R(sub A)). In contrast, the samples from the King's Triple Junction yield helium isotopic ratios averaging 9.4 (+/- 0.8) x 10(exp -6) (6.7 +/- 0.6 R/R(sub A)), systematically lower than the MORB-like value, which may be reflecting the addition of radiogenic He-4 released from the descending slab. Neon isotopic ratios are enriched in Ne-20 and Ne-21 with respect to atmospheric ratios by as much as 23% and 62% respectively. These observations further confirm that non-atmospheric neon is common characteristic of samples derived from the mantle. The helium and neon isotopic signatures in the samples can be explained by mixing of a primordial solar component, radiogenic and nucleogenic components produced by radioactive processes inside the Earth, and an atmospheric component. This reconnaissance survey of noble gases in a backarc basin indicates that current volcanism is dominated by magmas from the mantle wedge, a source similar to that from which MORBs are derived. The heavier noble gases (argon, krypton and xenon), however, show more atmosphere-like compositions, either indicating strong interaction of the magmas with the atmosphere or the presence of a recycled component derived from the underlying subducting slab.

Honda, Masahiko; Patterson, Desmond B.; McDougall, Ian; Falloon, Trevor J.

1993-12-01

158

High power external cavity laser diode arrays for the generation of hyperpolarized noble gases  

Microsoft Academic Search

Hyperpolarized noble gas magnetic resonance imaging promises to be a useful medical diagnostic tool due to its ability to image airways and brain function. A current limitation to widespread use is the time needed to generate gas quantities large enough for clinical patient imaging. Here I investigate line-narrowing of laser diode arrays in order to optimize the generation of hyperpolarized

Gregory Paul Blasche

2004-01-01

159

Noble Gases and CRE Ages of Eucrites NWA 5073, NWA 2550 and HaH 286  

NASA Astrophysics Data System (ADS)

We report the first noble gas and CRE age data for basaltic eucrites NWA 5073, NWA 2550 and HaH 286 in research to better understand the impact history on Vesta. Our preliminary results correlate with an ejection event at ~22 Ma and one at 65-70 Ma.

Cartwright, J. A.; Ott, U.; Roszjar, J.; Barrat, J. A.; Bischoff, A.

2012-09-01

160

Evidence for multiple magma ocean outgassing and atmospheric loss episodes from mantle noble gases  

NASA Astrophysics Data System (ADS)

Giant impacts are theorized to generate global magma oceans during Earth's accretion. However, geochemical evidence requiring a terrestrial magma ocean is scarce. We will present evidence that the 3He/22Ne ratio in the depleted mantle requires at least two separate episodes of giant impact-induced atmospheric blow-off and magma ocean outgassing on Earth. 3He/22Ne ratios in the mantle source of equatorial Atlantic mid-ocean ridge basalts correlate with Ne, Pb and Nd isotope ratios, establishing that mantle 3He/22Ne variability is caused by recent mixing of sources with different endmember compositions. Our data define the 3He/22Ne ratio of the depleted mantle to be ?10, whereas primitive material sampled by plumes has a value of ~2.3-3. These terrestrial ratios are higher than all possible sources of volatile elements, in particular the solar nebula with a value of 1.5. Therefore a planetary process must have raised the mantle's 3He/22Ne ratio. We demonstrate that long-term plate tectonic cycling is incapable of fractionating He and Ne significantly in 4.5 Ga and if anything would lower their ratio. However, solubility-controlled ingassing or outgassing of a magma ocean is predicted to raise the 3He/22Ne ratio in the mantle during Earth's accretion. The 3He/22Ne ratio as well as the 20Ne/22Ne ratio of primitive material sampled by plumes is consistent with ingassing a gravitationally accreted nebular atmosphere into a magma ocean. Ingassing would raise the mantle 3He/22Ne over the nebular value by at most a factor of ~2, the He/Ne solubility ratio in a pyrolitic magma ocean. The 6.5 enhancement in the 3He/22Ne of the depleted mantle over the nebular value requires at least two additional episodes of giant impact-induced atmospheric blow-off and magma ocean outgassing, the last of which being the Moon-forming impact. Each of these outgassing episodes raises the mantle 3He/22Ne ratio by at most a factor of ~2. We note that atmospheric blow-off is necessary for driving He/Ne fractionation in the mantle. The large differences in the 3He/22Ne of the primitive reservoir and the depleted mantle require that the giant impacts, including the Moon-forming impact, could not have melted and homogenized the whole mantle. Hence, if primordial noble gases in plumes are derived from large low shear velocity provinces (LLSVPs) at the core-mantle boundary, these features did not form from crystallization of the magma ocean associated with the Moon-forming impact. LLSVPs may have formed from crystallization products of previous magma oceans and survived the Moon-forming impact, or else their formation is unrelated to magma oceans. Along with 20Ne/22Ne and 129Xe/130Xe, the disparate 3He/22Ne ratios between mantle domains require that 4.5 billion years of mantle convection has not erased chemical differences set up during accretion.

Tucker, J.; Mukhopadhyay, S.

2013-12-01

161

Low-pressure adsorption of Ar, Kr, and Xe on carbonaceous materials (kerogen and carbon blacks), ferrihydrite, and montmorillonite: Implications for the trapping of noble gases onto meteoritic matter  

Microsoft Academic Search

Noble gases trapped in meteorites are tightly bound in a carbonaceous carrier labeled phase Q. Mechanisms having led to their retention in this phase or in its precursors are poorly understood. To test physical adsorption as a way of retaining noble gases into precursors of meteoritic materials, we have performed adsorption experiments for Ar, Kr, and Xe at low pressures

Yves Marrocchi; Angelina Razafitianamaharavo; Laurent J. Michot; Bernard Marty

2005-01-01

162

Noble Gases in a Metal Separate of the Solar-Gas Rich Meteorite Fayetteville, Released by Closed System Oxidation with CuCl2xnH2O  

Microsoft Academic Search

Closed system stepped oxidation of noble gas-rich samples at room-temperature leads to less diffusive elemental fractionation during gas-release than techniques involving high temperatures like stepped combustion or pyrolysis. Metal is generally considered to retain noble gases even better than ilmenite. Thus regolithic metal samples are likely to contain the least fractionated solar noble gases. A metal separate of the dark

Ch. Murer; H. Baur; P. Signer; R. Wieler

1992-01-01

163

Noble gases in CH sub 4 -rich gas fields, Alberta, Canada  

Microsoft Academic Search

The elemental and isotopic compositions of helium, neon, argon, and xenon in twenty-one CH-rich natural gas samples from Cretaceous and Devonian reservoirs in the Alberta, Canada, sedimentary basin were measured. In all but a few cases, radiogenic (⁴He, ⁴°Ar, and ¹³¹⁻¹³⁶Xe) and nucleogenic ({sup 21,22}Ne) isotopes dominated. Based solely on the noble gas composition, two types of natural gas reservoirs

H. Hiyagon; B. M. Kennedy

1992-01-01

164

Experimental detection of the influence of radiation damages upon the diffusion behaviour of solar wind noble gases in single grains of moon dust  

Microsoft Academic Search

The linear heating technique was applied to study the diffusion of solar ; wind implanted noble gases (⁴He and ²°Ne) in single grains of moon ; dust. The samples were heated in a diffusion oven with a heating rate of 6 K\\/min ; from room temperature to 1,200 K. The thus expelled gases were detected in highly ; sensitive mass

H. Ducati

1973-01-01

165

Pressure broadening and shift of the cesium D transition by the noble gases and N, H, HD, D, CH, CH, CF, and He  

Microsoft Academic Search

The pressure broadening and shift rates for the cesium D (6 P<-6 S) transition with the noble gases and N, H, HD, D, CH, CH, CF, and He were obtained for pressures less than 300 torr at temperatures under 65 deg. C by means of laser absorption spectroscopy. The collisional broadening rate, gamma{sub L}, for He, Ne, Ar, Kr, Xe,

Greg A. Pitz; Douglas E. Wertepny; Glen P. Perram

2009-01-01

166

Intensive sampling of noble gases in fluids at Yellowstone: I. Early overview of the data; regional patterns  

NASA Astrophysics Data System (ADS)

The Roving Automated Rare Gas Analysis (RARGA) lab of Berkeley's Physics Department was deployed in Yellowstone National Park for a 19 week period commencing in June, 1983. During this time 66 gas and water samples representing 19 different regions of hydrothermal activity within and around the Yellowstone caldera were analyzed on site. Routinely, the abundances of five stable noble gases and the isotopic compositions of He, Ne, and Ar were determined for each sample. In a few cases the isotopes of Kr and Xe were also determined and found to be of normal atmospheric constitution. Correlated variations in the isotopic compositions of He and Ar can be explained within the precision of the measurements by mixing of only three distinct components. The first component is of magmatic origin and is enriched in the primordial isotope 3He with 3He /4He ? 16 times the air value. This component also contains radiogenic 40Ar and possible 36Ar with 40Ar /36Ar ? 500 , resulting in a 3He /36Ar ratio ? 41,000 times the air value. The second component is assumed to be purely radiogenic 4He and 40Ar ( 4?He /40?Ar = 4.08 .33 ). This component is the probable carrier of observed excesses of 21?Ne, attributed to the ?,n reaction on 18O. Its radiogenic character implies a crustal origin in U. Th, and Krich aquifer rocks. The third component, except for possible mass fractionation, is isotopically indistinguishable from the noble gases in the atmosphere. This component originates largely from infiltrating run-off water saturated with atmospheric gases. In addition to exhibiting nucleogenic 21?Ne, Ne data show anomalies in the ratio 20Ne /20Ne , which correlate roughly with the 21Ne /22Ne anomalies for the most part, but not as would occur from simple mass fractionation. Some exaggerated instances of the 20Ne /22Ne anomaly occur which could be explained by combined mass fractionation of Ne and Ar isotopes to a severe degree coupled with remixing with normally isotopic gases. Otherwise exotic processes have to be invoked to explain the 20Ne data. Relative abundances of the non-radiogenic and non-nucleogenic noble gases ( 22Ne, 36Ar, 84Kr, and 132Xe) are highly variable but strongly correlated. High Xe/Ar ratios are always accompanied by low Ne/ Ar ratios and vice versa. Except for water from the few cold ( T < 20 C) springs analyzed, none of the samples have relative abundances consistent with air saturated water and the observed variations are not readily explained by the distillation of air saturated water. In characterizing each area of hydrothermal activity by the highest 3He /4He ratio found for that area, we find that within the caldera this parameter is somewhat uniform at ~7 1 times the air value. There are exceptions, most notably at Mud Volcano, an area located along a crest of recent and rapid uplift. Here the maximum 3He /4He ratio is ~ 16 times the air value. Also noteworthy is Gibbon Basin which is in the vicinity of the most recent rhyolitic volcanism and exhibits a 3He /4He ratio ~ 13 times the air value. Immediately outside the caldera the maximum sol 3He /4He ratio decreases rapidly to values < ~3 times the air value.

Kennedy, B. M.; Lynch, M. A.; Reynolds, J. H.; Smith, S. P.

1985-05-01

167

Cosmogenic noble gases in lunar meteorites: unravelling the history of the lunar regolith  

NASA Astrophysics Data System (ADS)

We are conducting a survey of the cosmogenic noble gas isotope record of lunar meteorite samples, to determine their exposure and closure ages and constrain their depth of burial on the Moon. Lunar regolith meteorites are ejected from the Moon by asteroidal and cometary impacts and delivered to Earth [1]. We are initially investigating twelve lunar meteorites from the ANSMET meteorite collection. Lunar meteorites represent material that is sourced from random localities on the Moon that are previously unsampled, including our only samples from the lunar farside. Thus, these meteorites are from mixed provenances, which include feldspathic rocks, basaltic rocks and mixed feldspathic and basaltic types: this is to investigate the regolith in different types of crustal terrains.

Curran, N. M.; Burgess, R.; Joy, K. H.; Fellowes, J. W.

2013-09-01

168

Incorporation of Solar Noble Gases from a Nebula-derived Atmosphere during Magma Ocean Cooling  

Microsoft Academic Search

To test the idea that solar gases were acquired by the Earth by dissolution in a magma ocean from a nebuladerived atmosphere, we calculate the cooling history of such a system. Preliminary results constrain the conditions under which this could have occurred.

D. S. Woolum; P. Cassen; D. Porcelli; G. J. Wasserburg

1999-01-01

169

Production Rates of Noble Gases in the Near-Surface Layers of Europa by Energetic Charged Particles and the Potential for Determining Exposure Ages  

NASA Technical Reports Server (NTRS)

The surface of Europa is expected to be extremely active, undergoing tectonic and/or tidal geological activity and sputtering/ deposition, as well as impact cratering. Determination of the actual age of the surface at one or more places would greatly simplify trying to sort out what processes are occurring, and at what rate. If there is K present, as the spectral and compositional modeling discussed predict, it should be possible, in principle, to determine K-Ar crystallization ages. Whether or not there is K present, a consideration of the environment suggests we can determine an energetic particle exposure age if we can make in situ measurements of the abundances of major elements and of noble gas isotopes. This requires instrumentation that is within reach of current technology. In this paper, we calculate production rates for noble-gas isotopes in a simplified Europan surface, to quantify the amount of light noble gases produced by exposure to energetic particles.

Swindle, T. D.; Reedy, R. C.; Masarik, J.

2003-01-01

170

Relationships between Noble Gases and Indicators of Geochemical Enrichment in Carbonatite Metasomatized Xenoliths from Samoa  

NASA Astrophysics Data System (ADS)

Rejuvenated lavas from oceanic hotspots can host peridotite mantle xenoliths that provide windows into the composition and history of the upper mantle. Peridotite xenoliths hosted in Samoan rejuvenated lavas from the Island of Savaii exhibit evidence for variable enrichment by carbonatitic melts. Some xenoliths are trace element depleted, while others host incompatible element budgets on par with enriched alkali basalts (Hauri and Hart, 1994). The most incompatible element enriched xenoliths have 87Sr/86Sr ratios (up to 0.7128) that are the highest observed in the oceanic mantle. Poreda and Farley (1992) examined the noble gas isotopic compositions of a different suite of xenoliths from the same locality. They identified a narrow range of 3He/4He ratios (8.6 to 12.04 Ra), while the neon isotopic compositions spanned an enormous range, from the Loihi-Kileaua line (unradiogenic) to the MORB line. The xenoliths with the highest 3He/4He have neon isotopes that are most unradiogenic, while samples with lower 3He/4He have MORB-like neon isotopic compositions. It is not known which xenoliths in this suite have experienced carbonatite metasomatism, as lithophile element concentrations were not reported by Poreda and Farley (1992), and the noble gas signature associated with carbonatite metasomatism beneath Samoa is unknown. We report new helium measurements on olivine and orthopyroxene separates from 14 Savaii peridotite xenoliths that were previously characterized by Hauri and Hart (1994) and Hauri et al (1993). All samples are extremely fresh. Their 3He/4He ratios span 11.6 to 12.41 Ra, at the high end of the range reported by Poreda and Farley (1992). We also report whole-rock trace element abundances on these xenoliths (trace elements on individual clinopyroxenes from each sample were reported by Hauri and Hart and Hauri et al (1993)). The xenoliths that exhibit trace element evidence for enrichment from carbonatite fluids (low Nb/U, and high La/Nd and Nb/Ta) have the lowest 3He/4He. By contrast, the most trace element depleted xenoliths have higher 3He/4He. These trace element correlations suggest that the carbonatitic fluid responsible for the enrichment has lower 3He/4He. Based on the known correlations between helium and neon, this would suggest that the lower 3He/4He is also associated with more radiogenic neon isotopes , and that the trace element depleted xenoliths should have unradiogenic neon. The samples with the highest 4He concentrations (approximately 1.46E-7 to 7.5E-7 g/cc) will be further analyzed for Ne and Ar isotopic compositions.

Kukolich, S.; Jackson, M. G.; Kurz, M. D.

2012-12-01

171

Light noble gases in 12 meteorites from the Omani desert, Australia, Mauritania, Canada, and Sweden  

NASA Astrophysics Data System (ADS)

We measured the concentrations and isotopic compositions of He, Ne, and Ar in 14 fragments from 12 different meteorites: three carbonaceous chondrites, six L chondrites (three most likely paired), one H chondrite, one R chondrite, and one ungrouped chondrite. The data obtained for the CV3 chondrites Ramlat as Sahmah (RaS) 221 and RaS 251 support the hypothesis of exposure age peaks for CV chondrites at approximately 9 Ma and 27 Ma. The exposure age for Shi?r 033 (CR chondrite) of 7.3 Ma is also indicative of a possible CR chondrite exposure age peak. The three L chondrites Jiddat al Harasis (JaH) 091, JaH 230, and JaH 296, which are most likely paired, fall together with Hallingeberg into the L chondrite exposure age peak of approximately 15 Ma. The two L chondrites Shelburne and Lake Torrens fall into the peaks at approximately 40 Ma and 5 Ma, respectively. The ages for Bassikounou (H chondrite) and RaS 201 (R chondrite) are approximately 3.5 Ma and 5.8 Ma, respectively. Six of the studied meteorites show clear evidence for 3He diffusive losses, the deficits range from approximately 17% for one Lake Torrens aliquot to approximately 45% for RaS 211. The three carbonaceous chondrites RaS 221, RaS 251, and Shi?r 033 all have excess 4He, either of planetary or solar origin. However, very high 4He/20Ne ratios occur at relatively low 20Ne/22Ne ratios, which is unexpected and needs further study. The measured 40Ar ages fit well into established systematics. They are between 2.5 and 4.5 Ga for the carbonaceous chondrites, older than 3.6 Ga for the L and H chondrites, and about 2.4 Ga for the R chondrite as well as for the ungrouped chondrite. Interestingly, none of our studied L chondrites has been degassed in the 470 Ma break-up event. Using the amount of trapped 36Ar as a proxy for noble gas contamination due to terrestrial weathering we are able to demonstrate that the samples studied here are not or only very slightly affected by terrestrial weathering (at least in terms of their noble gas budget).

Leya, I.; Ammon, K.; Cosarinsky, M.; Dalcher, N.; Gnos, E.; Hofmann, B.; Huber, L.

2013-08-01

172

Optical properties of explosive-driven shock waves in noble gases  

SciTech Connect

High explosives have been used to shock-heat rare gases to brightness temperatures up to 36,000/sup 0/K, with large radiating areas. Temperatures were determined from radiometer signals at both 280 and 520 nm. Shock velocities up to 9 mm/..mu..s were used in both plane and cyclindrical geometries. Neon, argon, krypton, and xenon gases at atmospheric initial pressure were examined in plane shocks. Using argon, the effects of increased initial pressure were studied. For cylindrical shock expansion in argon, brightness temperatures were measured over a range of shock velocities from 3 to 9 mm/..mu..s. Up to 4% of the explosive energy was emitted as radiation. The shock waves are found to be reasonable approximations to blackbodies.

Jones, C.R.; Davis, W.C.

1983-01-01

173

Noble Gases and Siderophile Elements in the Mantle: Unconventional Experimental Results and Their Implications for Chemical Geodynamics  

NASA Astrophysics Data System (ADS)

Recent and ongoing experimental studies reveal unexpected behavior of noble gases and siderophile elements that may affect future geodynamic interpretations. Ar-uptake experiments on mantle minerals provide insight into Ar compatibility (solubility) and diffusivity in these phases. Contrary to expectation, solubility results suggest that Ar behaves as a compatible element during mantle melting, favoring residence in point defects in minerals over 'escape' to the melt. In terms of diffusion, Ar is sufficiently mobile in olivine and orthopyroxene to ensure effective dispersal from relatively K-rich minerals on a geodynamically short time scale. Solid-liquid equilibration during melting of the MORB source is also likely; however, Ar diffusion is slow enough for disequilibrium to arise during phenocryst growth in a pre-eruption setting. The main implications of these results are that: 1) Ar degassing of the mantle through MORB volcanism may be an inefficient process; and 2) the existence of deeply-sequestered Ar (and other noble gases?) is plausible. New data on the behavior of siderophile elements (Os, Ir, Ru, Rh, Pt, Re, Au, W, Mo, Co, Cu and C) in polycrystalline MgO and synthetic peridotite reveal that these elements are highly mobile in the grain boundaries of mantle assemblages and analogs. W, Au and C have the highest diffusivities (10-8 to 10-7 m2/s); Ir, Ru, Re and Os are at the low end of the range (~10-12 to 10-11 m2/s). There is no discernible correlation between grain-boundary diffusivity and any particular property of the atoms or elements. These new data imply that Earth's outer core may 'leak' siderophile elements into the lower mantle over distances exceeding 100 km in 4 GYr for W, Au and C. Although not significant in itself as a whole-mantle transport process, grain boundary diffusion appears capable of 'contaminating' the lower mantle over a sufficient distance to enable entrainment of a core signature into plume- or convective mantle flow. If the outer core contains C, our data suggest that there may be a significant core-to-mantle flux of this element.

Watson, E. B.; Hayden, L. A.; Thomas, J. B.; Cherniak, D. J.

2007-12-01

174

Recombination-amplitude calculations of noble gases, in both length and acceleration forms, beyond the strong-field approximation  

NASA Astrophysics Data System (ADS)

Transition of an electron from a free to a bound state is critical in determining the qualitative shape of the spectrum in high-order-harmonic generation (HHG), and in tomographic imaging of orbitals. We calculate and compare the recombination amplitude, from a continuum state described by a plane wave and an outgoing scattering eigenstate, to the bound state for the noble gases that are commonly used in HHG. These calculations are based on the single active electron model and the Hartree-Fock-Slater method, using both the length form and the acceleration form of the dipole matrix element. We confirm that the recombination amplitude versus emitted photon energy strongly depends upon the wave function used to describe the free electron. Depending on the choice of the wave function and the dipole form, the square of the absolute value of the recombination amplitude can differ by almost two orders of magnitude near the experimentally measured Cooper minima. Moreover, only the outgoing scattering eigenstates with the length form roughly predict the experimentally observed Cooper minimum for Ar (50eV) and Kr (85eV). We provide a detailed derivation of the photorecombination cross sections from photoionization cross sections (PICSs) calculated by the relativistic random phase approximation (RRPA). For Ar, Kr, and Xe, we compare the total PICSs calculated using our recombination amplitudes with that obtained from RRPA. We find that PICS calculated using the outgoing scattering eigenstates with the length form is in better agreement with the RRPA calculations than the acceleration form.

Bhardwaj, Siddharth; Son, Sang-Kil; Hong, Kyung-Han; Lai, Chien-Jen; Krtner, Franz X.; Santra, Robin

2013-11-01

175

Noble gases in the Xinjiang (Armanty) iron meteorite--A big object with a short cosmic-ray exposure age  

NASA Astrophysics Data System (ADS)

We measured the concentrations and isotopic ratios of the cosmogenic noble gases He, Ne, and Ar in the very large iron meteorite Xinjiang (IIIE). The 3He and 4He data indicate that a significant portion of the cosmogenic produced helium has been lost via diffusion or in a recent impact event. High 22Ne/21Ne ratios indicate that contributions to the cosmogenic 21Ne from sulfur and/or phosphorous are significant. By combining the measured nuclide concentrations with model calculations for iron meteorites we were able to determine the preatmospheric diameter of Xinjiang to 260-320 cm, which corresponds to a total mass of about 70-135 tons. The cosmic-ray exposure age of Xinjiang is 62 16 Ma, i.e., relatively short compared to most of the other iron meteorites. With the current database we cannot firmly determine whether Xinjiang experienced a complex irradiation history. The finding of 3He and 4He losses might argue for a recent impact event and therefore for a complex exposure.

Ammon, Katja; Leya, Ingo; Lin, Yangtin

2011-06-01

176

Volatiles (nitrogen, noble gases) in recently discovered SNC meteorites, extinct radioactivities and evolution  

NASA Astrophysics Data System (ADS)

We report noble gas and nitrogen analyses of newly discovered SNC meteorites, one nakhlite (NWA817) and four shergottites (NWA480, NWA856, NWA1068, and SaU 005). The K-Ar age (1.3 Ga) as well as the cosmic-ray exposure (CRE) age (10.01.3 Ma) of nakhlite NWA817 agree with data of Nakhla. The CRE ages of NWA480, NWA856, and NWA1068 (2.350.20, 2.600.21 and 2.010.65 Ma, respectively) are consistent, within uncertainties, with other basaltic shergottites, but the CRE age of SaU 005 (1.250.07 Ma) is distinct and indicates a different ejection event. Bulk K-Ar ages of all shergottites exceed the reported radiometric ages and reveal the presence of inherited radiogenic 40Ar in basaltic lavas. The isotopic composition of nitrogen trapped in these SNC meteorites is not homogeneous, since ? 15N values of either +15 to 20 or +45, indicate different nitrogen reservoirs. All shergottites contain fission xenon from 238U, and fission Xe of extinct ( T1/2=82 Ma) 244Pu, previously identified in ALH84001, in Chassigny and in Nakhla is also present in at least one shergottite (NWA856). The shergottites contain less fissiogenic Xe than other SNC, suggesting that either their source was more degassed or that the magma source region closed at a later time. In nakhlites, fission xenon from 244Pu correlates with uranium, a geochemical proxy of plutonium. Thus it is possible that fissiogenic Xe was not inherited during magma differentiation, but rather was produced in situ and retained in refractory mineral assemblages. In this interpretation, the magma evolution that settled the mineralogy and geochemistry of nakhlites took place at a time when 244Pu was alive and pre-dated the (late) events recorded in their radiometric ages. Alternatively, fissiogenic xenon was trapped from a mantle source during closed system evolution of the parent magmas, in which case such evolution might have taken place at considerable depth (pressure) in order to inhibit magma degassing during the course of differentiation.

Mathew, K. J.; Marty, B.; Marti, K.; Zimmermann, L.

2003-09-01

177

Environmental isotopes and noble gases in the deep aquifer system of Kazan Trona Ore Field, Ankara, central Turkey and links to paleoclimate  

NASA Astrophysics Data System (ADS)

Environmental isotopes and noble gases in groundwater samples from the Kazan Trona Ore Field are studied to establish the temperature change between the Holocene and the late Pleistocene. Noble gas temperatures (NGTs) presented in this study add an important facet to the global paleotemperature map in the region between Europe and North Africa. The groundwater system under investigation consists of three different aquifers named shallow, middle and deep in which ?18O and ?2H vary from - 8.10 to - 12.80 and from - 60.89 to - 92.60 VSMOW, respectively. The average isotopic depletion between unconfined and confined parts of the system is - 2.5 in ?18O and - 20 in ?2H. It is not possible to explain this depletion solely with the elevation effect. Recharge temperatures derived from dissolved atmospheric noble gases reflect the current average yearly ground temperatures (13C) for samples collected near the recharge area but are 3 to 8C lower than today's temperatures in the deep aquifer system. Low 14C activities and high He excesses in the confined parts of the aquifer system suggest that the water in the deep aquifer was recharged during the last Pleistocene under considerably cooler climatic conditions.

Arslan, Sebnem; Yazicigil, Hasan; Stute, Martin; Schlosser, Peter

2013-03-01

178

Genesis Noble Gas Measurements  

NASA Technical Reports Server (NTRS)

The original thrust of our Genesis funding was to extend and refine the noble gas analytical capabilities of this laboratory to improve the precision and accuracy of noble gas measurements in order to optimize the scientific return from the Genesis Mission. This process involved both instrumental improvement (supplemented by a SRLIDAP instrument grant) and refinement of technique. The Genesis landing mishap shifted our emphasis to the irregular aluminum heat shield material from the flat collector wafers. This has required redesign of our laser extraction cells to accommodate the longer focal lengths required for laser extraction from non-flat surfaces. Extraction of noble gases from solid aluminum surfaces, rather than thin coatings on transparent substrates has required refinement of controlled-depth laser ablation techniques. Both of these bring new problems, both with potentially higher blanks form larger laser cells and the larger quantities of evaporated aluminum which can coat the sapphire entrance ports. This is mainly a problem for the heavy noble gases where larger extraction areas are required, necessitating the new aluminum vapor containment techniques described below. With the Genesis Mission came three new multiple multiplier noble gas mass spectrometers to this laboratory, one built solely by us (Supergnome-M), one built in collaboration with Nu-Instruments (Noblesse), and one built in collaboration with GVI (Helix). All of these have multiple multiplier detection sections with the Nu-Instruments using a pair of electrostatic quad lenses for isotope spacing and the other two using mechanically adjustable positions for the electron multipliers. The Supergnome-M and Noblesse are installed and running. The GVI instrument was delivered a year late (in March 2005) and is yet to be installed by GVI. As with all new instruments there were some initial development issues, some of which are still outstanding. The most serious of these are performance issues with the miniature channel electron multipliers. The delayed installation of Helix by the GVI is partly due to failure of the initial batch of Burle channel multipliers to perform as expected. A number of the channel multipliers designed for Noblesse by Burle have also failed upon baking. Burle has now refined the design of these and we have installed two of the new multipliers and are assessing their performance. The remaining multipliers Will be upgraded to the new design from Burle once we confirm that the problem has been fixed.

Hohenberg, Charles M.

2005-01-01

179

The L3-6 chondritic regolith breccia Northwest Africa (NWA) 869: (II) Noble gases and cosmogenic radionuclides  

NASA Astrophysics Data System (ADS)

We measured cosmogenic radionuclides and noble gases in the L3-6 chondrite breccia Northwest Africa (NWA) 869, one of the largest meteorite finds from the Sahara. Concentrations of 10Be, 26Al, and 36Cl in stone and metal fractions of six fragments of NWA 869 indicate a preatmospheric radius of 2.0-2.5 m. The 14C and 10Be concentrations in three fragments yield a terrestrial age of 4.4 0.7 kyr, whereas two fragments show evidence for a recent change in shielding, most likely due to a recent impact on the NWA meteoroid, approximately 105 yr ago, that excavated material up to approximately 80 cm deep and exposed previously shielded material to higher cosmic-ray fluxes. This scenario is supported by the low cosmogenic 3He/21Ne ratios in these two samples, indicating recent loss of cosmogenic 3He. Most NWA samples, except for clasts of petrologic type 4-6, contain significant amounts of solar Ne and Ar, but are virtually free of solar helium, judging from the trapped 4He/20Ne ratio of approximately 7. Trapped planetary-type Kr and Xe are most clearly present in the bulk and matrix samples, where abundances of 129Xe from decay of now extinct 129I are highest. Cosmogenic 21Ne varies between 0.55 and 1.92 10-8 cm3 STP g-1, with no apparent relationship between cosmogenic and solar Ne contents. Low cosmogenic (22Ne/21Ne)c ratios in solar gas free specimens are consistent with irradiation in a large body. Combined 10Be and 21Ne concentrations indicate that NWA 869 had a 4? cosmic-ray exposure (CRE) age of 5 1 Myr, whereas elevated 21Ne concentrations in several clasts and bulk samples indicate a previous CRE of 10-30 Myr on the parent body, most probably as individual components in a regolith. Unlike many other large chondrites, NWA 869 does not show clear evidence of CRE as a large boulder near the surface of its parent body. Radiogenic 4He concentrations in most NWA 869 samples indicate a major outgassing event approximately 2.8 Gyr ago that may have also resulted in loss of solar helium.

Welten, Kees; Caffee, Marc W.; Franke, Luitgard; Timothy Jull, A. J.; Leclerc, Marlene D.; Metzler, Knut; Ott, Ulrich

2011-07-01

180

Noble gases in submarine pillow basalt glasses from the Lau Basin: Detection of a solar component in backarc basin basalts  

Microsoft Academic Search

Noble gas elemental and isotopic abundances have been analysed in eight samples of youthful basaltic glass dredged from three different locations within the Lau Backarc Basin: (1) the King's Triple Junction, (2) the Central Lau Spreading Center at 18 deg S and (3) the Eastern Lau Spreading Center at 19 deg S. Samples from the Lau central and eastern spreading

Masahiko Honda; Desmond B. Patterson; Ian McDougall; Trevor J. Falloon

1993-01-01

181

Crustal noble gases in deep brines as natural tracers of vertical transport processes in the Michigan Basin  

Microsoft Academic Search

Noble gas concentrations and isotopic ratios are presented for 38 deep (?0.53.6 km) brine samples in the Michigan Basin. These brine samples clearly show the presence of an important crustal component of 4He, 21Ne, 40Ar, and 136Xe. Both 40Arcrust and 136Xecrust display the presence of a strong vertical gradient along the sedimentary strata of the basin. We show that the

Lin Ma; Maria Clara Castro; Chris M. Hall

2009-01-01

182

Noble gases in submarine pillow basalt glasses from Loihi and Kilauea, Hawaii - A solar component in the Earth  

Microsoft Academic Search

Noble gas elemental and isotopic abundances have been analyzed in 22 samples of basaltic glass dredged from the submarine flanks of two currently active Hawaiian volcanoes, Loihi Seamount and Kilauea. Neon isotopic ratios are enriched in Ne-20 and Ne-21 by as much as 16 percent with respect to atmospheric ratios. All the Hawaiian basalt glass samples show relatively high He-3\\/He-4

Masahiko Honda; Ian McDougall; Desmond B. Patterson; Anthony Doulgeris; David A. Clague

1993-01-01

183

A 30,000 yr Continental Paleotemperature Record Derived from Noble Gases Dissolved in Groundwater from the San Juan Basin, New Mexico  

NASA Astrophysics Data System (ADS)

Paleotemperatures for the last glacial maximum (LGM) have been derived from noble gases dissolved in 14C-dated groundwater of the Ojo Alamo and the Nacimiento formations in the San Juan Basin, northwestern New Mexico. The difference in mean annual (ground) temperature between the Holocene and the LGM was determined to be 5.5 0.7C. A practically identical result, 5.2 0.7C, has been obtained previously from the Carrizo aquifer in southern Texas. This suggests that the southwestern United States was uniformly cooler during the LGM and that the mean annual temperature gradient along a transect from the Gulf of Mexico to northwestern New Mexico has been unchanged since the LGM. The noble gas paleotemperatures are supported by paleoecological evidence in the region. The Holocene/LGM temperature difference of 5.4C indicates that a simple lapse rate calculation may be applied to convert the 1000-m glacial depression of snowlines in the Colorado Front Range into a temperature decrease. A continental temperature change of 5.4 0.7C is inconsistent with a temperature change of about 2C determined for the surface waters of the Gulf of Mexico.

Stute, Martin; Clark, Jordan F.; Schlosser, Peter; Broecker, Wallace S.; Bonani, Georges

1995-03-01

184

Stopping powers of gases for very heavy ions.  

National Technical Information Service (NTIS)

The stopping powers of gases have been measured for incident 24 MeV/u (sup 238)U and 29 MeV/u (sup 208)Pb projectiles, using the LISE spectrometer at GANIL. The results show the persistence of the 20% gas-solid effect observed at lower energy. The effecti...

R. Bimbot S. Barbey T. Benfoughal F. Clapier M. Mirea

1995-01-01

185

Pressure broadening and shift of the cesium D transition by the noble gases and N, H, HD, D, CH, CH, CF, and He with comparison to the D transition  

Microsoft Academic Search

The pressure broadening and shift rates for the cesium D (6 P (<-) 6 S) transition with the noble gases and N, H, HD, D, CH, CH, CF, and He were obtained for pressures less than 300 Torr at a temperature of 40 deg. C by means of laser absorption spectroscopy. The collisional broadening rate {sub L} for He, Ne,

Greg A. Pitz; Charles D. Fox; Glen P. Perram

2010-01-01

186

Population Dose Estimation from a Hypothetical Release of 2.4 X 10 exp 6 Curies of Noble Gases and 1 X 10 exp 4 Curies of exp 131 I at the Three Mile Island Nuclear Station, Unit 2.  

National Technical Information Service (NTIS)

Beginning on March 28, 1979, a sequence of events occurred at the Three Mile Island Nuclear Station Unit 2 (TMINS-2) nuclear power reactor which resulted in the accidental release of approximately 2.4 x 10 exp 6 Ci of noble gases and 13 to 15 Ci exp 131 I...

C. D. Berger B. H. Lane S. J. Cotter C. W. Miller S. R. Glandon

1981-01-01

187

Solubility investigations in support of ultrasensitive noble gas detector development.  

SciTech Connect

Argonne National Laboratory (ANL) and the University of Cincinnati (UC) have been developing a new class of ultrasensitive noble gas detectors that are based upon the ANL discovery that corn oil has a high affinity for heavy noble gas absorption at room temperature, but releases the noble gases with warming or by other low-energy-input means. Environmental applications for this new class of fluid-based detectors include ultrahigh sensitivity radioxenon detectors for Comprehensive Test Ban Treaty Surveillance, improved fission gas detectors for enhanced environmental surveillance in the vicinity of DOE, DOD, and NRC-licensed facilities, and improved integrating Rn detectors for earthquake prediction. The purpose of the present paper is to present the results of theoretical and experimental investigations into the solubility phenomena of heavy noble gases (Rn, Xe, and Kr) in triglyceride oils. It is the authors' intention that the findings presented herein may be used to guide future selection, development, and refinement of vegetable and other hydrocarbon oils to bring further enhancements to noble gas detection efficiencies.

Gross, K. C.

1998-08-05

188

Solubility investigations in support of ultrasensitive noble gas detector development  

SciTech Connect

Argonne National Laboratory (ANL) and the University of Cincinnati (UC) have been developing a new class of ultrasensitive noble gas detectors that are based upon the ANL discovery that corn oil has a high affinity for heavy noble gas absorption at room temperature but releases the noble gases with warming or by other low-energy-input means. Environmental applications for this new class of fluid-based detectors include ultrahigh sensitivity radioxenon detectors for comprehensive test ban treaty surveillance, improved fission gas detectors for enhanced environmental surveillance in the vicinity of US Department of Energy, US Department of Defense, and US Nuclear Regulatory Commission licensed facilities, and improved integrating Rn detectors for earthquake prediction. They present the results of theoretical and experimental investigations into the solubility phenomena of heavy noble gases (Rn, Xe, and Kr) in triglyceride oils. They intend for the findings presented herein to be used to guide future selection, development, and refinement of vegetable and other hydrocarbon oils to bring further enhancements to noble gas detection efficiencies.

Gross, K.C.; Andersen, A. [Argonne National Lab., IL (United States); Russ, W.R.; Stuenkel, D.; Valentine, J.D. [Univ. of Cincinnati, OH (United States)

1998-12-31

189

Dissolved noble gases and stable isotopes as tracers of groundwater dynamics in the Lower Rhine Embayment, Germany  

NASA Astrophysics Data System (ADS)

A multiple environmental tracer approach has been applied to achieve an improved understanding of groundwater dynamics in the Lower Rhine Embayment, Germany. The main emphasis has been to utilise dissolved noble gas and noble gas determined excess air concentrations in addition to the stable isotopes of hydrogen, oxygen, carbon and strontium. It is hypothesised that a relationship between noble gas excess air concentrations and the magnitude and frequency of water table fluctuations, both natural and as a result of large scale water abstraction can be quantified and used as an indicator of groundwater recharge, flow rate and residence times. The research has also provided further insight into the role of fault zones on local and regional groundwater dynamics. The hydrogeology of the Lower Rhine Embayment is complex and dynamic, and consists of unconsolidated sedimentary deposits with a number of laterally continuous lignite seams. Large scale open pit mining has a significant impact on the regional groundwater system primarily due to water abstraction and subsequent lowering of the water table. The layered aquifer system is intersected by numerous NW-SE striking fault zones that have been shown to have the potential to act as both barriers to groundwater flow and as preferential flow paths. Groundwater samples taken from observation boreholes in close proximity to fault zones have provided preliminary results that indicate hydrogen and oxygen isotope anomalies and extremely high helium-4 concentrations in the shallow aquifer layers. Groundwater exchange between the lower and upper aquifer systems is impeded by confining clay layers and a continuous lignite seam of very low permeability. This suggests that palaeowater from depth is mixing with modern water of meteoric origin in the upper aquifer as a result of conduit flow from depth towards the upper aquifer layer within the fault zone.

Gumm, L. P.; Dennis, P. F.; Bense, V. F.; Hiscock, K. M.; Cremer, N.

2009-04-01

190

Noble gases as natural tracers of water circulation in the Paris Basin: 2. Calibration of a groundwater flow model using noble gas isotope data  

NASA Astrophysics Data System (ADS)

Using the rare gas concentrations in the aquifers of the Paris Basin (see part 1 of this series), a numerical model of a two-dimensional cross section of the entire Paris Basin was built to simulate groundwater flow and the transport of 3He, 4He, and 40Ar isotopes. The model included seven aquifers separated by seven aquitards in a steady state flow regime. Transport of the gases is by advection, diffusion, and dispersion in steady or transient states. The 4He transport was simulated first and made it possible to calibrate both the crustal flux of this isotope and the average permeability of each aquifer, which were then favorably compared with measured values. These values present a high variability from aquifer to aquifer, between 8.5 10-7 and 3.5 10-4 m s-1. The water velocities and average residence times were also estimated. Average turnover times for the different aquifers are highly variable, ranging from 8700 years for the shallowest one (Ypresian) to 30 Myr for the deepest one (Trias). The calibrated model was also able to correctly represent the distribution of 3He and 40Ar in the basin. Diffusion proved to be an important mechanism for vertical transfer through the aquitards of the helium isotopes, as opposed to 40Ar, which is transported mainly by advection. On the basis of the (4He/40Ar) radiogenic ratio a constant value of 10-l1 m s-1 was attributed to the permeability of all the aquitards. A sensitivity study showed that the permeability of the aquitards situated in the lower part of the basin (Lias and aquitards in the Triassic and Dogger) could not be higher than 10-11 m s-1 given the observed distribution of the radiogenic 4He/40Ar ratio, but a lower limit could not be defined. The crustal fluxes of 3He, 4He, and 40Ar in the basin were estimated at 4.33 10-13 mol m-2 yr-1, 4. 10-6 mol m-2 yr-1 and 2.52 10-7 mol m-2 yr-1, respectively. The simulation of the 3He and 4He transport showed that theR/Ra ratio (value of the measured R = 3He/4He ratio normalized to the atmospheric ratio Ra) entering at the base of the Trias from the bedrock remained constant while crossing the basin except in the zones close to the recharge areas where it is influenced by the atmospheric component. This constancy is due to the low radiogenic/nucleogenic production rate of these isotopes inside the basin, as compared to the crustal flux.

Castro, Maria Clara; Goblet, Patrick; Ledoux, Emmanuel; Violette, Sophie; de Marsily, Ghislain

1998-10-01

191

Solubility and diffusivity study for light gases in heavy oil and its fractions  

NASA Astrophysics Data System (ADS)

Solvent-based recovery (VAPEX) is one of the most promising alternatives to thermal techniques to enhance heavy oil/bitumen recovery. Knowledge of the phase behavior and diffusion coefficients of gases in heavy oil is very important when designing recovery operations and facilities. In this work, a gravimetric microbalance was used to measure the solubility of carbon dioxide, ethane, propane and butane in a Lloydminster heavy oil and its fractions. Measurements were carried out on carbon dioxide and ethane at (290, 298 and 313) K over a pressure range from (200 to 2000) kPa. Similar measurements were performed on propane and butane below their vapor pressures. The Peng-Robinson equation of state was used to correlate the experimental results. The Solubility Parameter Theory was used to predict the solubility of CO2 and propane in heavy oil/bitumen over a wide range of pressures and temperatures. The associated Henry's Law constants for carbon dioxide, ethane and propane in heavy oil, its saturate fractions and aromatic fractions, were also determined from the absorption data. The gases had higher solubilities and the strongest interactions at lower temperatures in the heavy oil and its fractions. The diffusion coefficients of carbon dioxide, ethane and propane in heavy oil, its saturate and aromatic fractions were calculated using a simple diffusion model. The diffusion coefficient of carbon dioxide, ethane, propane and butane in heavy oil were calculated at different pressures. Estimated values were in agreement with published results and were found satisfactory.

Ganapathi, Rajkumar

192

Basin scale natural gas source, migration and trapping traced by noble gases and major elements: the Pakistan Indus basin  

Microsoft Academic Search

He, Ne and Ar concentrations, He and Ar isotopic ratios, carbon isotopic ratios and chemical compositions of hydrocarbon gases were measured in natural gas samples from gas-producing wells in the Indus basin, Pakistan, where no oil has ever been found. 3He\\/4He ratios are in the range 0.010.06 Ra (Ra is the atmospheric value of 1.3810?6) indicating the absence of mantle-derived

Anne Battani; Philippe Sarda; Alain Prinzhofer

2000-01-01

193

Comparisons of sets of electron-neutral scattering cross sections and swarm parameters in noble gases: I. Argon  

NASA Astrophysics Data System (ADS)

This paper describes work done in the context of the Gaseous Electronics Conference (GEC) Plasma Data Exchange Project (PDEP) as discussed in the preface to this cluster issue. The purposes of this paper and its companion papers are to compare sets of cross sections for electron scattering from ground-state noble gas atoms in the energy range from thermal to about 1 keV and to comment on their applicability for plasma modelling. To these ends, we present in this paper intercomparisons of the nine independently derived sets of cross sections for electron scattering from ground-state argon atoms that have been posted in databases on the LXCat open-access website (www.lxcat.laplace.univ-tlse.fr). We show electron transport, excitation and ionization coefficients (swarm parameters) calculated using these cross section data in Boltzmann solvers and we compare calculated values with measurements. For the most part, the cross section sets have been compiled by co-authors on this paper and appendices giving details about how the various cross sections datasets were compiled have been written by the individual co-authors. Additional appendices discuss our criteria for selection of experimental data to be included in the comparisons and give a brief overview of the methods used here for solving the Boltzmann equation.

Pitchford, L. C.; Alves, L. L.; Bartschat, K.; Biagi, S. F.; Bordage, M. C.; Phelps, A. V.; Ferreira, C. M.; Hagelaar, G. J. M.; Morgan, W. L.; Pancheshnyi, S.; Puech, V.; Stauffer, A.; Zatsarinny, O.

2013-08-01

194

Comparisons of sets of electron-neutral scattering cross sections and swarm parameters in noble gases: II. Helium and neon  

NASA Astrophysics Data System (ADS)

This paper is the second of a series of four reports, describing work carried in 2011 in the context of the Plasma Data Exchange Project with the Gaseous Electronics Conference, devoted to intercomparisons between different sets of electron-neutral scattering cross sections from ground-state noble gas atoms, in the energy range from thermal to about 1 keV. The present work compares cross section sets for helium and neon, determined independently, which are available on the open access LXCat website (www.lxcat.laplace.univ-tlse.fr/). The cross sections are used as input data in an electron Boltzmann solver or in Monte Carlo simulations, to calculate different swarm parameters (transport parameters and rate coefficients). The calculated quantities are compared with measurements to assess the quality of the cross sections in providing data for modelling low-temperature plasmas or analysing experiments. The paper includes several appendices prepared by co-authors to the work, presenting details on how the various cross section datasets were compiled or evaluated.

Alves, L. L.; Bartschat, K.; Biagi, S. F.; Bordage, M. C.; Pitchford, L. C.; Ferreira, C. M.; Hagelaar, G. J. M.; Morgan, W. L.; Pancheshnyi, S.; Phelps, A. V.; Puech, V.; Zatsarinny, O.

2013-08-01

195

Pressure broadening and shift of the cesium D1 transition by the noble gases and N2 , H2 , HD, D2 , CH4 , C2H6 , CF4 , and H3e  

Microsoft Academic Search

The pressure broadening and shift rates for the cesium D1 (6P21\\/2<--6S21\\/2) transition with the noble gases and N2 , H2 , HD, D2 , CH4 , C2H6 , CF4 , and H3e were obtained for pressures less than 300 torr at temperatures under 65C by means of laser absorption spectroscopy. The collisional broadening rate, gammaL , for He, Ne, Ar,

Greg A. Pitz; Douglas E. Wertepny; Glen P. Perram

2009-01-01

196

Pressure broadening and shift of the cesium D2 transition by the noble gases and N2, H2, HD, D2, CH4, C2H6, CF4, and He3 with comparison to the D1 transition  

Microsoft Academic Search

The pressure broadening and shift rates for the cesium D2 (62P3\\/2 <-- 62S1\\/2) transition with the noble gases and N2, H2, HD, D2, CH4, C2H6, CF4, and He3 were obtained for pressures less than 300 Torr at a temperature of 40C by means of laser absorption spectroscopy. The collisional broadening rate gammaL for He, Ne, Ar, Kr, Xe, N2, H2,

Greg A. Pitz; Charles D. Fox; Glen P. Perram

2010-01-01

197

Noble gases and chemical composition of Shergotty mineral fractions, Chassigny, and Yamato-793605: The trapped 40Ar/36Ar ratio and ejection times of martian meteorites  

NASA Astrophysics Data System (ADS)

We report the elemental and isotopic composition of the noble gases as well as the chemical abundances in pyroxene, maskelynite/mesostasis glass, and bulk material of Shergotty and of bulk samples from Chassigny and Yamato-793605. The 40K-40Ar isochron for the Shergotty minerals yields a gas retention age of 196 Ma, within errors in agreement with previously determined Rb-Sr internal isochron ages. Argon that was trapped at this time has a 40Ar/36Ar ratio of 1100. For Chassigny and Yamato-793605 we obtain trapped 40Ar/36Ar ratios of 1380 and 950, respectively. Using these results and literature data we show that the three shergottites Shergotty, Zagami, and QUE94001, the lherzolites ALH77005, LEW88516, and Yamato-793605, as well as Chassigny and ALH84001 contain a mixture of martian mantle and atmospheric Ar, whereas the trapped (40Ar/36Ar) ratio of the nakhlites Nakhla, Lafayette, and Governador Valadares cannot be determined with the present data. We show that martian atmospheric trapped Ar in martian meteorites is correlated with the shock pressure that they experienced. Hence, we conclude that the martian atmospheric gases were introduced by shock into the meteoritic material. For the Shergotty minerals we obtain 3He-, 21Ne-, and 38Ar- based cosmic-ray exposure ages of 3.0 Ma and for the lherzolite Yamato-793605 4.0 Ma, confirming our earlier conclusion that the lherzolites were ejected from Mars about 1 Ma before the shergottites. Chassigny yields the previously known ejection age of 11.6 Ma

Terribilini, Dario; Eugster, Otto; Burger, Mario; Jakob, Alfred; Krohenbohl, Urs

1998-07-01

198

Adsorption of inert gases including element 118 on noble metal and inert surfaces from ab initio Dirac-Coulomb atomic calculations  

NASA Astrophysics Data System (ADS)

The interaction of the inert gases Rn and element 118 with various surfaces has been studied on the basis of fully relativistic ab initio Dirac-Coulomb CCSD(T) calculations of atomic properties. The calculated polarizability of element 118, 46.3 a.u., is the largest in group 18, the ionization potential is the lowest at 8.91 eV, and the estimated atomic radius is the largest, 4.55 a.u. These extreme values reflect, in addition to the general trends in the Periodic Table, the relativistic expansion and destabilization of the outer valence 7p3/2 orbital. Van der Waals coefficients C3 and adsorption enthalpies ?Hads of Ne through element 118 on noble metals and inert surfaces, such as quartz, ice, Teflon, and graphite, were calculated in a physisorption model using the atomic properties obtained. The C3 coefficients were shown to steadily increase in group 18, while the increase in ?Hads from Ne to Rn does not continue to element 118: The large atomic radius of the latter element is responsible for a decrease in the interaction energy. We therefore predict that experimental distinction between Rn and 118 by adsorption on these types of surfaces will not be feasible. A possible candidate for separating the two elements is charcoal; further study is needed to test this possibility.

Pershina, V.; Borschevsky, A.; Eliav, E.; Kaldor, U.

2008-10-01

199

Solar noble gases in the Earth: The systematics of helium-neon isotopes in mantle derived samples  

NASA Astrophysics Data System (ADS)

Primordial 3He, together with neon showing enrichment in 20Ne and 21Ne relative to 22Ne compared with atmospheric values, have been identified in many samples derived from the Earth's mantle. To explain the enrichment of 21Ne and 20Ne in the mantle source regions for these samples, it is necessary to mix at least two distinct non-atmospheric neon components. The two most likely candidates are nucleogenic and solar neon. Nucleogenic 21Ne, produced by local decay of U and Th, elevates {21Ne }/{22Ne } ratios. Solar neon is the only known component which has a {20Ne }/{22Ne } ratio greater than both the atmospheric value and the {20Ne }/{22Ne } ratios observed in terrestrial samples. We suggest, therefore, as a working hypothesis to account for the observed non-atmospheric neon, that there has been mixing of two neon components, solar and nucleogenic, in the mantle. If the Earth's primordial composition was solar, then we expect to see a correlation between the helium and neon isotope systematics. This is because primordial helium and neon would all be solar, and variations in the observed {3He }/{4He } and {21Ne }/{22Ne } ratios in the mantle would be due to the time integrated ingrowth of radiogenic 4He ( 4He ?) and nucleogenic 21Ne ( 21Ne ?), having a constant {4He ?}/{21Ne ?} production ratio. This relationship can be explicitly stated as: {21Ne ?}/{22Ne s}=}( {4He }/{3He }) Mantle - ( {4He }/{3He }) s} {21Ne ?}/{4He ?}( {3He }/{22Ne }) s, where subscript S denotes the solar composition. Using the above equation we can calculate hypothetical {3He }/{4He } ratios related to the neon isotopic compositions in the mantle sources. We are able to correlate the observed {3He }/{4He } ratios of all available samples having non-atmospheric neon isotopic ratios with the slopes of neon mixing lines between mantle and present-day atmospheric neon in {20Ne }/{22Ne }- {21Ne }/{22Ne } space. Thus, the helium and neon isotopic signatures in the mantle can be explained by mixing of a primordial solar component, different fractions of radiogenic and nucleogenic components produced by radioactive processes inside the Earth, and a present-day atmospheric component. The correlation between observed helium and neon isotopic ratios in samples derived from the mantle provides strong support for the notion that a significant primordial noble gas component in the Earth was of solar composition. This provides a critical boundary condition for models regarding how and when the Earth acquired its volatiles, and how its atmosphere evolved.

Honda, Masahiko; McDougall, Ian; Patterson, Desmond

1993-09-01

200

New evidence of mantle heterogeneity beneath the Hyblean Plateau (southeast Sicily, Italy) as inferred from noble gases and geochemistry of ultramafic xenoliths  

NASA Astrophysics Data System (ADS)

We analyzed major and trace elements, Sr and Nd isotopes in ultramafic xenoliths in Miocenic age Hyblean diatremes, along with noble gases of CO 2-rich fluid inclusions hosted in the same products. The xenoliths consist of peridotites and pyroxenites, which are considered to be derived from the upper mantle. Although the mineral assemblage of peridotites and their whole-rock abundance of major elements (e.g., Al 2O 3 = 0.8-1.5 wt.%, TiO 2 = 0.03-0.08 wt.%) suggest a residual character of the mantle, a moderate enrichment in some incompatible elements (e.g., La N/Yb N = 9-14) highlights the presence of cryptic metasomatic events. In this context a deep silicate liquid is considered the metasomatizing agent, which is consistent with the occurrence of pyroxenites as veins in peridotites. Both the Zr/Nb and 143Nd/ 144Nd ratios of the investigated samples reveal two distinct compositional groups: (1) peridotites with Zr/Nb ? 4 and 143Nd/ 144Nd ? 0.5129, and (2) pyroxenites with Zr/Nb ? 20 and 143Nd/ 144Nd ? 0.5130. The results of noble-gas analyses also highlight the difference between the peridotite and pyroxenite domains. Indeed, the 3He/ 4He and 4He/ 40Ar* ratios measured in the fluid inclusions of peridotites (respectively 7.0-7.4 0.1 Ra and 0.5-8.2, where Ra is the atmospheric 3He/ 4He ratio of 1.38 10 - 6 ) were on average lower than those for the pyroxenites (respectively 7.2-7.6 Ra and 0.62-15). This mantle heterogeneity is interpreted as resulting from a mixing between two end-members: (1) a peridotitic layer with 3He/ 4He ? 7 Ra and 4He/ 40Ar* ? 0.4, which is lower than the typical mantle ratio (~ 1-4) probably due to melt extraction events, and (2) metasomatizing mafic silicate melts that gave rise to pyroxenites characterized by 3He/ 4He ? 7.6 Ra, with a variable 4He/ 40Ar* due to degassing processes connected with the ascent of magma at different levels in the peridotite wall rock. The complete geochemical data set also suggests two distinct mantle sources for the xenolithic groups highlighted above: (1) a HIMU (high-?)-type source for the peridotites and (2) a DM (depleted mantle)-type source for the pyroxenites.

Correale, A.; Martelli, M.; Paonita, A.; Rizzo, A.; Brusca, L.; Scribano, V.

2012-02-01

201

Noble gases as natural tracers of water circulation in the Paris Basin: 1. Measurements and discussion of their origin and mechanisms of vertical transport in the basin  

NASA Astrophysics Data System (ADS)

The concentrations and isotopic compositions of helium, neon, and argon were measured in 29 water samples collected from five superposed aquifers in the Paris Basin (Ypresian, Albian, Neocomian, Dogger, and Trias). In all these groundwater flow systems the data showed excesses of 3He, 4He, and 40Ar above the solubility equilibrium with the atmosphere (air saturated water (ASW)), as well as vertical concentration gradients of these isotopes throughout the basin. The water of the Dogger and the Trias formations also had a 21Ne excess above ASW values. The mean rate of radiogenic and nucleogenic isotope production in the entire sedimentary sequence of the basin cannot produce the measured quantities of 3He, 4He, 21Ne, and 40Ar, if reasonable water residence times are considered. The total calculated production is estimated to represent less than about 13% of the measured values for all isotopes. The greater part (>87%) of the radiogenic and nucleogenic noble gas isotopes is thus believed to originate from the bedrock, and the isotopes are transported vertically through the entire basin. Three mechanisms of transport are considered: advection, dispersion, and molecular diffusion. For the Trias the radiogenic/nucleogenic production ratios of 4He/40Ar and 21Ne/40Ar are close to the mean production rate in the crust (4 3 and 0.96 10-7, respectively). For the overlying Dogger, however, these ratios are much higher (4He/40Ar: 10 to 70; 21Ne/40Ar: 8 10-7 to 23 10-7). We suggest that differences in the vertical diffusive flux of 4He, 21Ne, and 40Ar are the reason for the high isotope ratios observed in the Dogger. In the vertical direction, 4He is transported mostly by diffusion, whereas 40Ar is transported mostly by advection. Neon 21 represents an intermediate situation. The distribution of 3He, 4He,21Ne, and 40Ar throughout the basin can be explained by the existence of only two sources: an atmospheric component contributed by recharge water and a radiogenic/nucleogenic component originating mainly in the bedrock. This concept is supported by two-dimensional cross-section modeling of the water flow in the Paris Basin and the advective, dispersive, and diffusive transport of these noble gases in its multiaquifer system presented in part 2 of this study.

Castro, Maria Clara; Jambon, Albert; de Marsily, Ghislain; Schlosser, Peter

1998-10-01

202

Recycled volatiles in mantle-derived diamonds Evidence from nitrogen and noble gas isotopic data  

NASA Astrophysics Data System (ADS)

Noble gas isotopic data from diamonds are commonly interpreted as a two component mixture of gases from the mantle source of mid oceanic ridge basalt (MORB) and air. The air-like component in diamonds is generally considered to have been acquired secondarily through atmospheric contamination. In a recent study [C. Gautheron, P. Cartigny, M. Moreira, J.W. Harris, C.J. Allgre, Evidence for a mantle component shown by rare gases, C and N isotopes in polycrystalline diamonds from Orapa (Botswana), Earth Planet. Sci. Lett. 240(2005) 559-572.] that involved analyses of noble gases, carbon and nitrogen, such interpretation based on noble gases is used to constrain the sources of carbon and nitrogen in diamond to be solely from the mantle. With the help of heavy noble gas and nitrogen isotopic data from diamonds, we show here that the air-like noble gas component in diamonds is actually a mixture of contributions derived from recycled materials and (minor) air contamination. This, in turn, suggests that some of the carbon in diamonds may also have a recycled origin.

Mohapatra, Ratan K.; Honda, Masahiko

2006-11-01

203

Basin scale natural gas source, migration and trapping traced by noble gases and major elements: the Pakistan Indus basin  

NASA Astrophysics Data System (ADS)

He, Ne and Ar concentrations, He and Ar isotopic ratios, carbon isotopic ratios and chemical compositions of hydrocarbon gases were measured in natural gas samples from gas-producing wells in the Indus basin, Pakistan, where no oil has ever been found. 3He/ 4He ratios are in the range 0.01-0.06 Ra (Ra is the atmospheric value of 1.3810 -6) indicating the absence of mantle-derived helium despite the Trias extension. 40Ar/ 36Ar ratios range from 296 to 800, consistent with variable additions of radiogenic argon to atmospheric, groundwater-derived argon. Rare gas concentrations show large variations, from 610 -5 to 110 -3 mol/mol for 4He and from 310 -7 to 310 -5 mol/mol for 36Ar. In general, 36Ar concentrations are high compared to literature data for natural gas. CO 2 and N 2 concentrations are variable, ranging up to 70 and 20%, respectively. Mantle-derived He is not observed, therefore CO 2 and N 2 are not mantle-derived either. Hydrocarbon gas maturity is high, but accumulation efficiency is small, suggesting that early-produced hydrocarbons, including oil, were lost as well as mantle helium. This is consistent with the generally late, Pliocene, trap formation, and explains the high N 2 concentrations, since N 2 is the final species generated at the end of organic matter maturation. Based on ? 13C data, CO 2 originates from carbonate decomposition. Very elevated 20Ne/ 36Ar ratios are found, reaching a maximum of 1.3 (compared to 0.1-0.2 for air-saturated water and 0.5 for air), and these high values are related to the lowest rare gas concentrations. We suggest that this highly fractionated signature is the trace of the past presence of oil in the basin and appeared in groundwater. We propose a model where oil-water contact is followed by gas-water contact, both with Rayleigh distillation for rare gas abundance ratios, thereby generating the fractionated 20Ne/ 36Ar signature in groundwater first and transferring it to gas later. Assuming the gas-water contact occurred shallower than present reservoir depths, this model explains the generally high 36Ar concentrations and low CH 4/ 36Ar ratios compared to other studies on younger basins. It thus provides a historical perspective on fluid transfer in a sedimentary basin, where a gas accumulation may have been buried to greater depth since formation. Rare gas and major element data point to mixing between two gas pulses produced successively. The very CO 2-N 2-rich gases are terminal products of organic matter maturation which have been trapped after important migration. This gas was followed by a more typical thermogenic gas which mixed with it.

Battani, Anne; Sarda, Philippe; Prinzhofer, Alain

2000-08-01

204

Electron loss and single and double capture of C3+ and O5+ ions in collisions with noble gases  

NASA Astrophysics Data System (ADS)

Cross sections for the processes of projectile electron loss and single and double capture of C3+ and O5+ projectile ions impinging on He, Ne, Ar, Kr, and Xe targets were measured in the energy range of 1.0-3.5 MeV. The measured cross sections present a strong saturation as the target atomic number increases, for all the systems and collision channels studied. The single-capture data are compared with calculations based on a semiclassical model and on the eikonal approximation, both presenting a good general agreement with the experiment. In the case of electron loss, the observed saturation is in accordance with previous measurements for He+ projectiles, and is present in the first-order calculations for the antiscreening contribution but not in those for the screening. This is due to the fact that, for heavy target atoms, the screening mode can be highly nonperturbative. Calculations for the screening contribution to the electron loss, based on the free-collision model, together with first-order results for the antiscreening, are compared with the experimental data, presenting good agreement in most cases. However, this comparison also shows that one has to include other competitive channels in order to give a better description of the collision.

Melo, W. S.; Sant'anna, M. M.; Santos, A. C.; Sigaud, G. M.; Montenegro, E. C.

1999-08-01

205

Fullerenes and the Nature of Planetary Gases  

NASA Technical Reports Server (NTRS)

Over the past several decades, two issues have dominated the discussion of planetary noble gas patterns: 1) the general resemblance of the noble gas abundances in carbonaceous chondrites to those measured in the Earth s atmosphere and; 2) atmospheric inventories of argon and neon that fall off significantly with increasing distance from the Sun. The recognition of the latter has led to the conclusion that the planetary component is not found on planets. In particular, the inability to explain the missing xenon reservoir, once thought to be sequestered in crustal rocks has been extremely troublesome. Some models have focused on various fractionations of solar wind rather than condensation as the process for the evolution of noble gases in the terrestrial planets. However, these models cannot explain the observed gradient of the gases, nor do they account for the similar Ne/Ar ratios and the dissimilar planetary Ar/Kr ratios. More recent studies have focused on hydrodynamic escape to explain the fractionation of gases, like neon, in the atmosphere and the mantle. Escape theory also seems to explain, in part, the isotopically heavy argon on Mars, however, it does not explain the discrepancies observed for the abundances of argon and neon on Venus and the Earth. This has led to the assumption that some combination of solar wind implantation, absorption and escape are needed to explain the nature of planetary noble gases.

Becker, Luann; Poreda, Robert J.; Nuth, Joe

2003-01-01

206

Noble gas anomalies and synthesis of the chemical elements  

NASA Astrophysics Data System (ADS)

The elemental and isotopic abundances of noble gases trapped in meteorites are discussed in relation to the origin of the chemical elements and the condensation of the solar system. The abundance patterns of the two types of planetary noble gases and of solar noble gases are examined, and it is suggested that type-X planetary noble gases, which contain isotopically anomalous argon, krypton and xenon and normal helium and neon, were derived from the outer regions of a supernova, while the Y-type planetary noble gases, which consist of isotopically normal argon, krypton and xenon, were derived from its inner regions. It is argued, however, that variations in the isotopic composition of neon can be explained by mass fraction or mass fractionation plus spallation without recourse to separate nucleogenetic anomalies. It is also concluded that the differences in the abundance patterns of planetary noble gases are primarily the result of stellar fusion reactions and adsorption, rather than gas solubility.

Sabu, D. D.; Manuel, O. K.

1980-06-01

207

Atmospheric Ar and Ne trapped in coesite eclogite during Late Miocene (U)HP metamorphism: implications for the recycling of noble gases in subduction zones  

NASA Astrophysics Data System (ADS)

Several isotopic methods, including 40Ar/39Ar dating of phengite, have been used to determine the timing and duration of (U)HP metamorphism. However, in some (U)HP terranes phengite 40Ar/39Ar data , has yielded anomalously old ages interpreted to result from the presence of extraneous Ar (i.e., either inherited or excess Ar). We analyzed Ar and Ne extracted from phengite and omphacite from coesite eclogite in the Papua New Guinea (U)HP terrane to 1) assess the reliability of 40Ar/39Ar phengite ages to record the timing of (U)HP metamorphism in the youngest (U)HP terrane on Earth, and 2) to assess the non-radiogenic trapped Ar and Ne compositions in minerals that crystallized during subduction zone metamorphism. Step heat experiments on irradiated phengite yielded a 40Ar/39Ar weighted mean age of 8.31 +/- 0.32 Ma (2?) corresponding to ~88% 39Ar released. These results are concordant with previously published 238U/206Pb zircon ages, and nearly concordant with a Lu-Hf garnet isochron age, both obtained on the same sample. Results suggest that phengite reliably records the timing of peak (U)HP metamorphism and that excess 40Ar is not present in this coesite eclogite. Step heat experiments on irradiated phengite and pyroxene yielded 38Ar/36Ar above atmospheric values (>0.1885). These higher 38Ar/36Ar ratios from outgassed irradiated samples results from reactor-produced 38ArCl likely due to the presence of Cl-derived from fluid inclusions (i.e., via the nuclear reaction 37Cl(n,?)38Cl(?)38Ar). The high temperature release of 38ArCl may result from smaller fluid inclusions (<1-2 ?m). To further investigate the composition of non-radiogenic trapped Ar and Ne in coesite eclogite, step heat experiments were performed on multiple unirradiated splits of phengite and omphacite. Both minerals yielded atmospheric 38Ar/36Ar, including for high temperature (>1400C) steps. The abundance of radiogenic 40Ar corresponds to the respective [K] and ~8 Ma age of minerals also suggesting the absence of excess 40Ar in these samples. Omphacite outgassed at high temperature (>1400C) also yielded atmospheric 20Ne/22Ne. Results indicate that atmospheric Ar and Ne were trapped when minerals crystallized at ~8 Ma during (U)HP metamorphism. The survival of trapped atmospheric Ar and Ne in minerals formed during (U)HP metamorphism supports models that call for recycling of noble gases from the atmosphere back into the mantle at subduction zones.

Baldwin, S.; Das, J. P.

2013-12-01

208

Noble gases, 81Kr-Kr exposure ages and 244Pu-Xe ages of six eucrites, Brba, Binda, Camel Donga, Juvinas, Millbillillie, and Stannern  

NASA Astrophysics Data System (ADS)

Noble gases including radioactive 81Kr ( t1/2 = 2.1 10 5 yr) have been measured for the cumulate eucrite Binda and five noncumulate eucrites, Brba, Camel Donga, Juvinas, Millbillillie, and Stannern, some of which have been repeatedly analyzed. Concentrations of 81Kr, which range from 4.2 10 -14 to 3.2 10 -13 cm 3 STP/g, roughly correlate with abundances of the main target elements, Sr, Y, and Zr. 81Kr-Kr cosmic-ray exposure ages are obtained as 24.5 0.6 Ma, 21.0 1.6 Ma, 36.6 1.4 Ma, 10.6 0.8 Ma, 20.8 0.5 Ma and 35.1 0.7 Ma, for Brba, Binda, Camel Donga, Juvinas, Millbillillie, and Stannern, respectively. All the measured eucrites have 244Pu-derived fission Xe. On the basis of fission 136Xe concentrations, 244Pu abundances are calculated to range from 0.40 ppb for Binda to 1.08 ppb for Juvinas. Following the method proposed by Shukolyukov and Begemann (1996a), 244Pu-Xe ages relative to the absolute crystallization age of 4.5578 Ga for Angra dos Reis are determined as -46 18 Ma (Brba), -29 34 Ma (Binda), -51 16 Ma (Camel Donga), -10 23 Ma (Juvinas), +8 24 Ma (fine-grained portion of Millbillillie), -51 21 Ma (coarse-grained portion of Millbillillie), and -124 13 Ma (Stannern), which correspond to absolute ages ranging from 4.434 Ga (Stannern) to 4.566 Ga (fine-grained portion of Millbillillie). Millbillillie is a mixture of materials with different 244Pu-Xe ages. Stannern's unusually young 244Pu-Xe age might reflect a secondary shock disturbance, but otherwise, it tends to confirm a distinctive mode of igneous petrogenesis in comparison to most other eucrites. The 244Pu-Xe ages of the cumulate eucrites obtained so far (Binda, this work; Moore County, Shukolyukov and Begemann, 1996a) do not differ systematically from those of noncumulate eucrites. The four eucrites with the older 244Pu-Xe ages, Brba, Binda, Juvinas, and the fine-grained portion of Millbillillie, show significant amounts of radiogenic 129Xe, (0.6-2.3) 10 -12 cm 3 STP/g (after correction for fission 129Xe), which imply earlier retention of radiogenic 129Xe from extinct 129I than other eucrites with young 244Pu-Xe ages.

Miura, Yayoi N.; Nagao, Keisuke; Sugiura, Naoji; Fujitani, Tatsuya; Warren, Paul H.

1998-07-01

209

Noble Gas Temperature Proxy for Climate Change  

EPA Science Inventory

Noble gases in groundwater appear to offer a practical approach for quantitatively determining past surface air temperatures over recharge areas for any watershed. The noble gas temperature (NGT) proxy should then permit a paleothermometry of a region over time. This terrestria...

210

Cosmogenic noble gas paleothermometry  

NASA Astrophysics Data System (ADS)

We present a theoretical basis for reconstructing paleotemperatures from the open-system behavior of cosmogenic noble gases produced in minerals at Earth's surface. Experimentally-determined diffusion kinetics predicts diffusive loss of cosmogenic 3He and 21Ne from common minerals like quartz and feldspars at ambient temperatures; incomplete retention has also been observed empirically in field studies. We show that the theory of simultaneous production and diffusion that applies to radiogenic noble gases in minerals-the basis of thermochronology-can also be applied to cosmogenic noble gases to reconstruct past surface temperatures on Earth. We use published diffusion kinetics and production rates for 3He in quartz and 21Ne in orthoclase to demonstrate the resolving power of cosmogenic noble gas paleothermometry with respect to exposure duration, temperature, and diffusion domain size. Calculations indicate that, when paired with a quantitatively retained cosmogenic nuclide such as 21Ne or 10Be, observations of cosmogenic 3He in quartz can constrain temperatures during surface exposure in polar and high altitude environments. Likewise, 21Ne retention in feldspars is sensitive to temperatures at lower latitudes and elevations, expanding the potential geographic applicability of this technique to most latitudes. As an example, we present paired measurements of 3He and 10Be in quartz from a suite of Antarctic sandstone erratics to test whether the abundances of cosmogenic 3He agree with what is predicted from first principles and laboratory-determined diffusion kinetics. We find that the amounts of cosmogenic 3He present in these samples are consistent with the known mean annual temperature (MAT) for this region of Antarctica between -25 and -30 C. These results demonstrate the method's ability to record paleotemperatures through geologic time.

Tremblay, Marissa M.; Shuster, David L.; Balco, Greg

2014-08-01

211

Noble Gas Compositions in Muong Nong-type Tektites  

NASA Astrophysics Data System (ADS)

Tektites are natural silica-rich glasses and are thought to be produced during meteorite collisions with the Earth, similar to impact glasses. They occur in four geographically restricted areas and can be divided in three subgroups: normal or splash-form tektites, aerodynamically shaped tektites, and Muong Nong-type tektites [1]. Splash-form and aerodynamically shaped tektites are several grams in weight and are generally homogeneous in chemistry. On the other hand, Muong Nong-type tektites are up to several kilograms in weight, are irregular in shape, and show layered structure. They are inhomogeneous in chemistry and are enriched in volatile elements such as halogens, boron, zinc, etc., compared to splash-form tektites [1]. Muong Nong-type tektites have larger vesicles than splash-form and aerodynamically shaped tektites. This shows that Muong Nong-type tektites are different from splash-form and aerodynamically shaped tektites in several aspects. We measured noble gas compositions in splash-form tektites [2] and impact glasses [3,4]. Although Ne concentrations in tektites and impact glasses were similar to each other, heavy noble gas (Ar, Kr, and Xe) concentrations in tektites were about 2 orders of magnitude lower than those in impact glasses. In this study, we studied noble gas compositions in some Muong Nong-type tektites in order to compare them with splash-form tektites. Muong Nong-type tektite samples used in this study originated from Ubon Ratchatani in East Thailand, near the border of Laos. Geochemical studies of the samples were made by Koeberl [5]. We measured noble gas concentrations and Ne and Ar isotopic compositions in four Muong Nong-type tektites using mass spectrometry. Noble gases were extracted by three methods: laser probe, crushing, and stepwise heating. Chipped samples of two Muong Nong-type tektites were used in laser probe analysis. We used 160-380 mg of samples for noble gas analysis by crushing and stepwise-heating methods. Noble gas concentrations in tektites, impact glasses, and Muong Nong-type tektites are shown in Fig. 1. Tektites shown are splash-form types collected from three strewn fields [2,6]. Impact glasses shown are Aouelloul, Zhamanshin, Libyan Desert glasses [4], and Darwin glass [3]. Heavy noble gas concentrations in Muong Nong-type tektites are higher than those in splash- form tektites and are similar to those in impact glasses. From the results of laser probe and crushing analysis of noble gases in Muong Nong-type tektites, it seems that vesicles are unevenly distributed in these samples and that large amounts of noble gases exist in theses vesicles. Neon isotopic compositions in vesicles in Muong Nong-type tektites agree well with a terrestrial atmosphere. 40Ar/36Ar ratios in vesicles are higher than that in air, suggesting that radiogenic 40Ar exists in vesicles and/or that radiogenic 40Ar in glass may degas by crushing. Fig. 1, which appears here in the hard copy, shows noble gas concentrations in splash-form tektites (open circles), impact glasses (open triangles), and Muong Nong-type tektites (filled cirles). References: [1] Koeberl C. (1988) Proc. NIPR Symp. Antarct. Meteorites, 1, 261-290. [2] Matsubara K. and Matsuda J. (1991) Meteoritics, 26, 217-220. [3] Matsuda J. et al. (1989) GCA, 53, 3025-3033. [4] Matsubara K. et al. (1991) GCA, 55, 2951-2955. [5] Koeberl C. (1992) GCA, 56, 1033-1064. [6] Hennecke E. W. et al. (1975) JGR, 80, 2931-2934.

Matsubara, K.; Matsuda, J.; Koeberl, C.

1993-07-01

212

Heavy Noble Gases from the Southwest Indian Ridge: Insights into the Nature and Distribution of Mantle Heterogeneities  

Microsoft Academic Search

Helium isotopic compositions measured in glasses from the ultra-slow spreading Southwest Indian Ridge (SWIR) range from 4He\\/3He of 51,000 to 120,000 (3He\\/4He of 14.1 to 6 RA) (Georgen et al., EPSL 2003). The extent of isotopic variability found at the SWIR is remarkable: SWIR helium isotopic compositions span approximately half of the range observed in all mantle-derived basalts (4He\\/3He of

R. Parai; S. Mukhopadhyay; J. J. Standish

2009-01-01

213

High abundances of noble gas and chlorine delivered to the mantle by serpentinite subduction  

Microsoft Academic Search

The Earths mantle contains non-radiogenic noble gas isotopes that imply transfer of noble gases from the atmosphere into the mantle through subduction. Hydrated serpentinite rocks within subducting oceanic lithosphere are recognized as key carriers of water and chlorine, but the pathways for noble gas subduction have been poorly constrained. Here we analyse the concentration of noble gas isotopes and halogens

Marco Scambelluri; Masahiko Honda; David Phillips; Mark A. Kendrick

2011-01-01

214

Silicate Perovskite and the Terrestrial Noble Gas Signature  

Microsoft Academic Search

The relative abundance of noble gases on Earth is very different from the solar abundance pattern. All noble gases are strongly depleted mostly due to loss to space. However, xenon appears to be particularly depleted on Earth. This cannot be explained simply by hydrodynamic escape. Moreover, the amount of radiogenic 40Ar that should have been produced over Earth's history is

S. S. Shcheka; H. Keppler

2010-01-01

215

Noble gas measurements from tiny water amounts: fluid inclusions in carbonates of speleothemes and coral skeletons  

Microsoft Academic Search

Based on the concentrations of dissolved noble gases in fluid inclusions in speleothems and corals, noble gas temperatures (NGT) might be derived, that would be important climate information [1]. In the case of terrestrial carbonates, it means that the temperature dependency of noble gases in the evolving fluid inclusions is suitable to determine the prevailing temperature. This recognition provides new

Laszlo Papp; Laszlo Palcsu; Zoltan Major

2010-01-01

216

Mantle Reservoirs From a Noble Gas Perspective  

NASA Astrophysics Data System (ADS)

The noble gases provide unique insight into mantle structure and the origin of the different mantle reservoirs. Many OIBs, such as Hawaii and Iceland, have 3He/4He ratios that are a factor of 4 to 6 higher than the canonical MORB value of 81 RA. The high 3He/4He ratios in OIBs are conventionally viewed as evidence for the existence of a primitive mantle reservoir. Such a view, however, is frequently challenged on the grounds that noble gas abundances in OIBs are an order of magnitude lower than in MORBs, an observation that traditional models of magmatic degassing cannot explain. The apparent concentration paradox has been resolved by incorporating kinetic fractionation of the noble gases during magmatic degassing of the erupting magma and it can be shown that higher CO2 and H2O content of OIBs, compared to MORBs, leads to more extensive degassing of He in OIB magmas (Gonnermann and Mukhopadhyay, 2007). In contrast to Hawaii and Iceland, some ocean islands, such as the Cook-Austral Islands and Canary Islands (HIMU ocean islands) have 3He/4He ratios of 4-7 RA, lower than the MORB range. The low 3He/4He ratios are attributed to the addition of radiogenic 4He from recycled slabs. Surprisingly, recent high-precision neon isotopic measurements made at Harvard in olivine phenocrysts from the Cook-Austral Islands indicate that HIMU neon is less nucleogenic than the MORB source. The He and Ne systematics from the Cook-Austral's demonstrate that the noble gas signature of HIMU basalts cannot arise either from simple diffusive equilibration of a recycled slab with a MORB source, or result from mixing of melts that are derived from recycled slabs and the MORB mantle. The He-Ne systematics, however, can be quantitatively modeled as a mixture of recycled slab and a primitive mantle reservoir. The scenario is consistent with He-Os and He- Nd correlations seen in the Cook-Austral basalts. Thus, both low and high 3He/4He OIBs incorporate the same primitive mantle reservoir, although in varying proportions. The notion of a reservoir that is primitive in its volatile content and sampled at ocean islands is very much alive. In spite of whole mantle convection, it appears that part of the Earth's mantle has remained largely undegassed. While significant progress has been made with respect to understanding the geochemical implications of He and Ne isotopic composition measured in MORBs and OIBs, our knowledge of Xenon in the mantle remains poor. Since 129Xe and 136Xe have been produced by the now extinct nuclides, 129I and 244Pu respectively, Xe isotopic composition of the mantle can be used to test models of atmosphere formation and provide unique clues to the volatile history of the Earth's mantle. Some of the outstanding issues that still need to be resolved are whether the Earth's mantle has solar or chondritic heavy noble gases, whether OIBs and MORB have the same Xe isotopic composition, and what fraction of the 136Xe is from 244Pu vs. 238U fission. Addressing these issues will require not only high precision measurements but also innovative experimental techniques to reduce air contamination that is ubiquitous in mantle-derived samples. High precision Xe isotopic measurements made at Harvard indicates that Samoa (a high 3He/4He ocean island) and MORBs have exactly the same proportion of radiogenic 129Xe to 136Xe. Although this result needs to be verified from other OIBs, it suggests that a single mantle reservoir supplies the excess 129Xe and 136Xe to both the MORB and OIB mantle source. The primitive mantle reservoir is the most likely carrier of the xenon isotopic anomaly.

Mukhopadhyay, S.

2007-12-01

217

Pressure broadening and shift of the cesium D1 transition by the noble gases and N2 , H2 , HD, D2 , CH4 , C2H6 , CF4 , and H3e  

NASA Astrophysics Data System (ADS)

The pressure broadening and shift rates for the cesium D1 (6P21/2?6S21/2) transition with the noble gases and N2 , H2 , HD, D2 , CH4 , C2H6 , CF4 , and H3e were obtained for pressures less than 300 torr at temperatures under 65C by means of laser absorption spectroscopy. The collisional broadening rate, ?L , for He, Ne, Ar, Kr, Xe, N2 , H2 , HD, D2 , CH4 , C2H6 , CF4 , and H3e are 24.13, 10.85, 18.31, 17.82, 19.74, 16.64, 20.81, 20.06, 18.04, 29.00, 26.70, 18.84, and 26.00 MHz/torr, respectively. The corresponding pressure-induced shift rates, ? , are 4.24, -1.60 , -6.47 , -5.46 , -6.43 , -7.76 , 1.11, 0.47, 0.00, -9.28 , -8.54 , -6.06 , and 6.01 MHz/torr. These rates have then been utilized to calculate Lennard-Jones potential coefficients to quantify the interatomic potential surfaces. The broadening cross section has also been shown to correlate with the polarizability of the collision partner.

Pitz, Greg A.; Wertepny, Douglas E.; Perram, Glen P.

2009-12-01

218

Noble gas loss may indicate groundwater flow across flow barriers in southern Nevada  

Microsoft Academic Search

Average calculated noble gas temperatures increase from 10 to 22 C in groundwater from recharge to discharge areas in carbonate-rock aquifers of southern Nevada. Loss of noble gases from groundwater in these regional flow systems at flow barriers is the likely process that produces an increase in recharge noble gas temperatures. Emplacement of low permeability rock into high permeability aquifer

James M. Thomas; Bryant G. Hudson; Martin Stute; Jordan F. Clark

2003-01-01

219

Noble gas diffusion in silicate liquids  

NASA Astrophysics Data System (ADS)

Fractionated noble gas relative abundances (Ne/Ar, Kr/Ar and Xe/Ar) and isotopic compositions (40Ar/36Ar, 38Ar/36Ar, 20Ne/22Ne, 21Ne/22Ne) are found in volcanic materials, notably in pumices (1-3). This has generally been interpreted as fractionation resulting from diffusion. However, there is some disagreement as to whether this fractionation occurs during high temperature magmatic processes (3) or due to diffusion of air into solidified pyroclastic deposits (2). We show that differences in relative noble gas diffusivities (e.g. D4He vs D40Ar, where D is the diffusivity) and isotopic diffusivities (e.g. D40Ar vs D36Ar) reduce at high temperatures (Fig). These results predict minimal fractionation of noble gases during magmatic processes. However, it is important to note that these diffusivities were measured in silicate glasses; the relative noble diffusivities in silicate liquids are poorly known. We have developed a new experimental protocol which will to determine the diffusivities of the noble gases and their isotopes in the liquid state. A graphite crucible c. 0.3 mm diameter and c. 20mm deep is filled with powdered glass of the desired composition, heated to 1773 K for 15 minutes and quenched to form a glass cylinder within the crucible. The crucible is then placed in a low pressure (1 bar) controlled atmosphere vertical furnace and heated at high temperatures (1673-1773K) for 2 hours in a pure N2 atmosphere. At this point noble gases (He and Ar) are introduced into the furnace and allowed to diffuse into the cylinder of liquid for durations of between 30 and 90. After quenching, the glass cylinder, preserving its' diffusion profile, is sawed into c. 1mm thick discs which are measured by conventional noble gas mass spectrometry for noble gas abundances (He, Ar) and isotopes (40,38,36Ar). The results will be presented at the conference. References 1 Kaneoka, I. Earth Planet Sci Letts 48, 284-292 (1980). 2 Pinti, D. L., Wada, N. & Matsuda, J. J. Volcan Geotherm Res 88, 279-289 (1999). 3 Ruzie, L. & Moreira, M. J. Volcan Geotherm Res 192, 142-150 (2010). FIGURE: diffusion of 4He, 40Ar, 38Ar, 36Ar in silicate glass. Our experiments show that at high temperature, there is little or no diffusive fractionation of noble gases (abundances or isotopes) in silicate glasses. Therefore diffusive fractionation of noble gas abundances or isotope ratios can only occur at relatively low temperatures (< 1113 K)

Amalberti, J.; Burnard, P.; Laporte, D.

2013-12-01

220

Pressure broadening and shift of the cesium D2 transition by the noble gases and N2, H2, HD, D2, CH4, C2H6, CF4, and He3 with comparison to the D1 transition  

NASA Astrophysics Data System (ADS)

The pressure broadening and shift rates for the cesium D2 (62P3/2 ? 62S1/2) transition with the noble gases and N2, H2, HD, D2, CH4, C2H6, CF4, and He3 were obtained for pressures less than 300 Torr at a temperature of 40C by means of laser absorption spectroscopy. The collisional broadening rate ?L for He, Ne, Ar, Kr, Xe, N2, H2, HD, D2, CH4, C2H6, CF4, and He3 are 20.59, 9.81, 16.47, 15.54, 18.41, 19.18, 27.13, 28.24, 22.84, 25.84, 26.14, 17.81, and 22.35 MHz/Torr, respectively. The uncertainty in the broadening rates is typically less than 0.3%. The corresponding pressure-induced shift rates ? are 0.69, -2.58, -6.18, -6.09, -6.75, -6.20, -4.83, -4.49, -4.54, -8.86, -9.38, -6.47, and 0.60 MHz/Torr with an uncertainty of less than 0.04 MHz/Torr. With the exception of diatomic collision partners, the broadening rates for Cs D2 are 5%-15% less than the rates for Cs D1. For light collision partners with a blue shift, the D1 is shifted more than the D2 line. The broadening cross sections for Cs and Rb are similar. However, the cross sections for K are about 70% larger and for Na, about 30% less.

Pitz, Greg A.; Fox, Charles D.; Perram, Glen P.

2010-10-01

221

Study on evolution of gases from fluoropolymer films bombarded with heavy ions  

NASA Astrophysics Data System (ADS)

Ion beam bombardment provides a unique way of material modification by inducing a high degree of localized electronic excitation. The ion track, or affected volume along the ion path through the material is related to the total damage and possible structural changes. Here we study the evolution of gases emitted by poly(tetrafluorethylene-co-perfluoro-(propyl vinyl ether)) (PFA) fluoropolymer bombarded with MeV gold ions. The gas was monitored by a residual gas analyzer (RGA), as a function of the ion fluence. Micro-Raman, atomic force microscopy and optical absorption were used to analyze the chemical structure changes and sputtering yield.

Minamisawa, Renato Amaral; Zimmerman, Robert Lee; Budak, Satilmis; Ila, Daryush

2008-04-01

222

A Philippinite with an Unusually Large Bubble: Gas Pressure and Noble Gas Composition  

Microsoft Academic Search

Bubbles are common in tektites, but usually their sizes range up to only a few mm. They are most abundant in Muong Nong-type tektites. The gases contained in these bubbles are of terrestrial atmospheric composition, with pressures below 1 atm (e.g., [1]). The abundances of light noble gases (He, Ne) are controlled by diffusion from the atmosphere [2], and noble

J. Matsuda; T. Maruoka; D. L. Pinti; C. Koeberl

1995-01-01

223

Experimental Method for Measuring Solubilities of Heavy Fossil-Fuel Fractions in Compressed Gases to 100 Bar and 300 exp 0 C.  

National Technical Information Service (NTIS)

A new experimental method has been developed to measure solubilities of narrow-boiling, heavy fossil-fuel fractions in compressed gases. Solubilities are determined from the volume of gas required to vaporize completely a small, measured mass of fossil-fu...

A. Monge J. M. Prausnitz

1981-01-01

224

Three-dimensional model for simulating atmospheric dispersion of heavy-gases over complex terrain  

SciTech Connect

To help understand heavy gas releases and simulate the resultant dispersion, we have developed a three-dimensional finite element model called FEM3 and an improved version names FEM3A for solving the time dependent conservation equations based on generalized anelastic approximation. Recent enhancements to the model to include the treatment of dispersion scenarios involving density variations much larger than the liquefied natural gas range and an advanced turbulence submodel based on the buoyancy-extended transport equations. This paper presents the main features of the present model FEM3C and numerical results from the simulations of a field-scale LNG spill experiment.

Chan, S.T.

1997-09-01

225

Air-Xe enrichments in Elk Hills oil field gases: role of water in migration and storage  

Microsoft Academic Search

Hydrocarbons from the Elk Hills Naval Petroleum Reserve (NPR#1), Bakersfield, CA, are enriched in heavy noble gases. The 132Xe\\/36Ar ratios are as high as ?576 times the ratio in air and represent the largest relative Xe-enrichments ever observed in terrestrial fluids. The Xe isotopic composition is indistinguishable from air. We show that these samples cannot be explained by equilibration of

T. Torgersen; B. M. Kennedy

1999-01-01

226

Advances in noble gas paleothermometry on speleothems  

NASA Astrophysics Data System (ADS)

The application of the noble gas paleothermometer on speleothem fluid inclusions promises to provide absolute paleotemperatures from stalagmites. These noble gas temperatures (NGTs) are based on the temperature dependent solubility of gases in water and could help to interpret other speleothem proxies. In particular NGTs may help to better understand oxygen isotope records. In summer and autumn 2009 a measurement run with 26 (sub-)samples from 9 different caves was performed. The water and the noble gases were released using a stepwise extraction technique by online in vacuo crushing and thermal heating. Depending on the sample water amount about three extraction steps were performed for each sample, so that the total number of speleothem measurements exceeded 80 in this run. NGTs were determined from noble gas concentrations by inverse modeling. Only the equilibrium solubility component, which contains the temperature information, and an atmospheric air component from air-filled inclusions are included in the calculations. Plots of two noble gas concentrations against each other (Xe-Ne, Kr-Ar) show that the measured concentrations are in general agreement with this simple model. Unfortunately the combined mass spectrometric measurement of Ar, Kr and Xe turned out to be slightly problematic. A separated measurement should solve the corresponding problems. Furthermore, a lab water standard for noble gases will be prepared to further examine the measurements in the future. In this measurement run samples from not only Bunker Cave (Germany) showed suitable properties for NGT determination but also samples from Katerloch Cave (Austria) where the water concentration varies between 0.4 to 4 ?l per g calcite which is comparable to the Bunker Cave stalagmites. The air to water volume ratio is below 0.1 which in principle allows the determination of NGTs with errors in the range of 1 C. The calculated NGTs are in the range of the modern cave air temperature.

Marx, Thomas; Kluge, Tobias; Mangini, Augusto; Aeschbach-Hertig, Werner

2010-05-01

227

Explosively Generated Plasmas in Noble Gases  

Microsoft Academic Search

Non-ideal plasmas occur as a result of the stimulation of matter by strong shocks, detonation waves, or concentrated laser irradiation. Since all of these methods of generating non-ideal plasmas are already in use to address other problems, we focus on a detailed understanding of this plasma. In particular, we study the generation of this plasma by strong, ionizing guided shock

C. J. Boswell; J. R. Carney; J. M. Lightstone; J. Wilkinson; G. Pangilinan

2007-01-01

228

A proper mobility formula for large, heavy particles in gases in any regime  

NASA Astrophysics Data System (ADS)

The age-old problem of the derivation of a proper formula for the mechanical (or electrical) mobility of large, heavy (l.h.) particles in a simple neutral gas in any regime is carefully examined and solved under the usual hypotheses that the l.h. particles are subject to the action of a constant external force and undergo only elastic collisions with the gas particles. By a convenient procedure, a general mobility formula is obtained which not only properly corrects the well-known result derived by Cunningham for an l.h. hard sphere in a hard-sphere gas, but also applies to the general case in which both the l.h.-particle-gas-particle and gas-particle-gas-particle interactions are arbitrary. In addition, on the basis of the new formula, the fair success of the Cunningham formula (regarded as a semiempirical formula) in fitting the experimental results is explained. Other interesting aspects of the new formula are also examined, and its limits of validity are briefly discussed.

Ferrari, Leonardo

2000-07-01

229

Mineralogy and noble-gas signatures of the carbonate-rich lithology of the Tagish Lake carbonaceous chondrite: evidence for an accretionary breccia  

Microsoft Academic Search

The carbonate-rich lithology of the Tagish Lake carbonaceous chondrite was characterized by noble-gas mass spectrometry, synchrotron X-ray diffraction analysis, and transmission and scanning electron microscopy. Noble-gas analysis was performed on two samples and the results showed that primordial noble gases are abundant and solar noble gases are absent in the samples of carbonate-rich lithology. The concentrations of Ne-A2 and -E

Tomoki Nakamura; Takaaki Noguchi; Michael E. Zolensky; Masahiko Tanaka

2003-01-01

230

LaRC results on nuclear pumped noble gas lasers  

NASA Technical Reports Server (NTRS)

The recent experiment and theoretical results obtained for noble gas nuclear laser systems are presented. It is shown that the noble gas lasers are among the easiest systems to pump by nuclear excitation and as a result, all of the noble gases except He have lased under nuclear excitation. The noble gas systems are not ideal for high-power applications but they do give valuable insight into the operation and pumping mechanisms associated with nuclear lasers. At present, the Ar-Xe system is the best noble gas candidate for (U-235)F6 pumping. It appears that the quenching of Ar-Xe lasing is a result of the fluorine and not the uranium or fission fragments themselves. Thus, to achieve lasing with UF6, a fluorine compatible system must be found.

Deyoung, R. J.

1979-01-01

231

Mantle Reservoirs From a Noble Gas Perspective  

Microsoft Academic Search

The noble gases provide unique insight into mantle structure and the origin of the different mantle reservoirs. Many OIBs, such as Hawaii and Iceland, have 3He\\/4He ratios that are a factor of 4 to 6 higher than the canonical MORB value of 81 RA. The high 3He\\/4He ratios in OIBs are conventionally viewed as evidence for the existence of a

S. Mukhopadhyay

2007-01-01

232

Genesis Noble Gas Measurements.  

National Technical Information Service (NTIS)

The original thrust of our Genesis funding was to extend and refine the noble gas analytical capabilities of this laboratory to improve the precision and accuracy of noble gas measurements in order to optimize the scientific return from the Genesis Missio...

C. M. Hohenberg

2005-01-01

233

Neutron detection by scintillation of noble-gas excimers  

NASA Astrophysics Data System (ADS)

Neutron detection is a technique essential to homeland security, nuclear reactor instrumentation, neutron diffraction science, oil-well logging, particle physics and radiation safety. The current shortage of helium-3, the neutron absorber used in most gas-filled proportional counters, has created a strong incentive to develop alternate methods of neutron detection. Excimer-based neutron detection (END) provides an alternative with many attractive properties. Like proportional counters, END relies on the conversion of a neutron into energetic charged particles, through an exothermic capture reaction with a neutron absorbing nucleus (10B, 6Li, 3He). As charged particles from these reactions lose energy in a surrounding gas, they cause electron excitation and ionization. Whereas most gas-filled detectors collect ionized charge to form a signal, END depends on the formation of diatomic noble-gas excimers (Ar*2, Kr*2,Xe* 2) . Upon decaying, excimers emit far-ultraviolet (FUV) photons, which may be collected by a photomultiplier tube or other photon detector. This phenomenon provides a means of neutron detection with a number of advantages over traditional methods. This thesis investigates excimer scintillation yield from the heavy noble gases following the boron-neutron capture reaction in 10B thin-film targets. Additionally, the thesis examines noble-gas excimer lifetimes with relationship to gas type and gas pressure. Experimental data were collected both at the National Institute of Standards and Technology (NIST) Center for Neutron Research, and on a newly developed neutron beamline at the Maryland University Training Reactor. The components of the experiment were calibrated at NIST and the University of Maryland, using FUV synchrotron radiation, neutron imaging, and foil activation techniques, among others. Computer modeling was employed to simulate charged-particle transport and excimer photon emission within the experimental apparatus. The observed excimer scintillation yields from the 10B( n, alpha)7Li reaction are comparable to the yields of many liquid and solid neutron scintillators. Additionally, the observed slow triplet-state decay of neutron-capture-induced excimers may be used in a practical detector to discriminate neutron interactions from gamma-ray interactions. The results of these measurements and simulations will contribute to the development and optimization of a deployable neutron detector based on noble-gas excimer scintillation.

McComb, Jacob Collin

234

An Air Noble Gas Component in the Mantle  

NASA Astrophysics Data System (ADS)

Noble gas geochemistry has for long attempted to recover isotopic signatures of mantle components through analyses of basalt glass or xenoliths, but this quest has been plagued by the occurrence of a conspicuous air component, which appears to have both the isotopic and elemental composition of air (except for helium). It is classically considered to be air added to samples close to the surface, in a poorly understood process called "contamination", due to the interaction of rocks and melts with air or water on emplacement. Focusing on Mid-Ocean Ridge Basalts (and Ocean Island Basalts), gases are mostly borne by vesicles and a number of puzzling observations can be made: - vesicles appear to be heterogeneous at the scale of a centimeter, as shown by stepwise crushing experiments, some vesicles having air, some having mantle gases, some having mixtures of both, - vesicles appear over-pressured (P > 1 bar) in fresh samples, as shown by highly vesiculous samples such as Popping Rocks, - the air component appears to be borne by the largest vesicles, as it is recovered in the first steps of stepwise crushing analyses, - larger samples seem to have more of the air component than smaller ones, - in Popping Rocks, the air component borne by the largest vesicles is overwhelming, - the isotopic composition of Pb-Sr-Nd in Popping Rocks was interpreted as indicating a recycled component (related to the HIMU and EM1 mantle end-members). The air noble gas component was suggested recently to be not seawater, but modern air located in fractures of the glass, which should have opened on cooling and resealed immediately [1]. This model faces some difficulties, such as keeping pressure high in the vesicles. I suggest another interpretation, namely that a large part of the air noble gases in oceanic basalts is recycled in origin [2]. It would have been carried down into the mantle at subduction zones, even if most (typically 90%) of the air noble gases in the slab returns to the atmosphere there [3]. The upper mantle would thus be a marble cake and, on melting, the recycled, more fertile component would melt first. The first vesicles would then bear the atmospheric noble gas component, while the next liquids would be produced more from the peridotite matrix, and would eventually generate vesicles with mantle noble gases (40Ar/36Ar > 10,000, 129Xe/130Xe > 7, . . .). A simple model for this double-step melting, using classical equations for trace elements and assuming that vesicles appear as soon as melt is generated, reproduces the 40Ar/36Ar pattern seen on step-crushing of popping rocks, with reasonable values for partition coefficients and proportion of recycled matter. Although this model remains to be investigated, part of the atmospheric noble gases in oceanic basalts may be recycled in origin. This hypothesis simply explains several of the observations above. Especially, it can reconcile noble gas and non-gaseous isotopic tracers by allowing recycled noble gases to occur together with mantle noble gases, in vesicles with different sizes. [1] C.J. Ballentine and D.N. Barfod, The origin of air-like noble gases in MORB and OIB, Earth Planet Sci. Lett. 180, 39-48, 2000. [2] Ph. Sarda, Surface noble gas recycling to the terrestrial mantle, Earth Planet Sci. Lett. 228, 49-63, 2004. [3] T. Staudacher and C.J. Allegre, Recycling of oceanic crust and sediments: the noble gas subduction barrier, Earth Planet. Sci. Lett. 89, 173-183, 1988.

Sarda, P.

2005-12-01

235

Noble Gas Proxy Evidence Of Holocene Climate Fluctuations In The Elwha Watershed, Olympic Mountains, Washington  

EPA Science Inventory

Paleotempertures retrieved from the groundwater archives in the largest watershed (?800 km2) in the Olympic Mountains suggest asynchronous Olympic Peninsula climate responses during the Everson interstade period after the last continental glacial maximum. Dissolved noble gases fr...

236

Biomedical Investigations with Laser-Polarized Noble Gas Magnetic Resonance  

NASA Technical Reports Server (NTRS)

We pursued advanced technology development of laser-polarized noble gas nuclear magnetic resonance (NMR) as a novel biomedical imaging tool for ground-based and eventually space-based application. This new multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI)-e.g., of lung ventilation-as well as studies of tissue perfusion. In addition, laser-polarized noble gases (3He and 129Xe) do not require a large magnetic field for sensitive detection, opening the door to practical MRI at very low magnetic fields with an open, lightweight, and low-power device. We pursued two technology development specific aims: (1) development of low-field (less than 0.01 T) noble gas MRI of humans; and (2) development of functional MRI of the lung using laser-polarized noble gas and related techniques.

Walsworth, Ronald L.

2003-01-01

237

Multiple ion Counting for Noble gas Mass Spectrometry  

Microsoft Academic Search

In geo- and cosmochemistry noble gases are analyzed for their abundance and isotopic composition by mass spectrometry in the static mode (no pumping). This results in that they are among the elements with the highest detection efficiency. This is especially so for xenon, where during the course of a normal measurement almost all atoms will have been ionized. Not all

U. Ott

2008-01-01

238

Noble gas dependence of single-bubble sonoluminescence in phosphoric acid  

NASA Astrophysics Data System (ADS)

Single-bubble sonoluminescence (SL) from a concentrated solution of phosphoric acid doped with various noble gases has been studied using a hydrochemical model. The results indicate that in agreement with experiment, the SL temperature increases with the atomic mass of the noble gases. Also, both the temperature and the intensity of SL are remarkably higher for lower partial pressures of a noble gas. Our calculations show that the maximum acquirable SL intensity from phosphoric acid is considerably greater than that of water. This mainly originates from the lower vapor pressure and the higher viscosity of phosphoric acid relative to water making the instability mechanisms completely different for these liquids.

Faraji, Mehdi; Moshaii, Ahmad

2012-09-01

239

Air-Xe enrichments in Elk Hills oil field gases: role of water in migration and storage  

NASA Astrophysics Data System (ADS)

Hydrocarbons from the Elk Hills Naval Petroleum Reserve (NPR#1), Bakersfield, CA, are enriched in heavy noble gases. The 132Xe/ 36Ar ratios are as high as 576 times the ratio in air and represent the largest relative Xe-enrichments ever observed in terrestrial fluids. The Xe isotopic composition is indistinguishable from air. We show that these samples cannot be explained by equilibration of oil with air saturated water and secondary enrichment via a Rayleigh distillation gas stripping process. Based on laboratory studies of others with potential petroleum source rocks, we believe the source of this enriched heavy noble gas component was adsorbed air initially trapped in/on the source rocks that was expelled and mixed with the hydrocarbons during expulsion and primary migration. Kr and Xe enrichments decrease with increasing 36Ar concentration. We propose a model in which an initial Kr-Xe-enriched hydrocarbon becomes diluted with noble gases extracted from air saturated groundwater during expulsion, migration, and storage. The model generates an integrated water/hydrocarbon ratio for the production fluid which indicates a minimal role for water in hydrocarbon expulsion and migration. The results are interpreted to provide time/geometrical constraints on the mechanisms by which hydrocarbons can migrate as a separate phase.

Torgersen, T.; Kennedy, B. M.

1999-04-01

240

Determination of Natural In Vivo Noble-Gas Concentrations in Human Blood  

PubMed Central

Although the naturally occurring atmospheric noble gases He, Ne, Ar, Kr, and Xe possess great potential as tracers for studying gas exchange in living beings, no direct analytical technique exists for simultaneously determining the absolute concentrations of these noble gases in body fluids in vivo. In this study, using human blood as an example, the absolute concentrations of all stable atmospheric noble gases were measured simultaneously by combining and adapting two analytical methods recently developed for geochemical research purposes. The partition coefficients determined between blood and air, and between blood plasma and red blood cells, agree with values from the literature. While the noble-gas concentrations in the plasma agree rather well with the expected solubility equilibrium concentrations for air-saturated water, the red blood cells are characterized by a distinct supersaturation pattern, in which the gas excess increases in proportion to the atomic mass of the noble-gas species, indicating adsorption on to the red blood cells. This study shows that the absolute concentrations of noble gases in body fluids can be easily measured using geochemical techniques that rely only on standard materials and equipment, and for which the underlying concepts are already well established in the field of noble-gas geochemistry.

Tomonaga, Yama; Brennwald, Matthias S.; Livingstone, David M.; Tomonaga, Genevieve; Kipfer, Rolf

2014-01-01

241

Determination of natural in vivo noble-gas concentrations in human blood.  

PubMed

Although the naturally occurring atmospheric noble gases He, Ne, Ar, Kr, and Xe possess great potential as tracers for studying gas exchange in living beings, no direct analytical technique exists for simultaneously determining the absolute concentrations of these noble gases in body fluids in vivo. In this study, using human blood as an example, the absolute concentrations of all stable atmospheric noble gases were measured simultaneously by combining and adapting two analytical methods recently developed for geochemical research purposes. The partition coefficients determined between blood and air, and between blood plasma and red blood cells, agree with values from the literature. While the noble-gas concentrations in the plasma agree rather well with the expected solubility equilibrium concentrations for air-saturated water, the red blood cells are characterized by a distinct supersaturation pattern, in which the gas excess increases in proportion to the atomic mass of the noble-gas species, indicating adsorption on to the red blood cells. This study shows that the absolute concentrations of noble gases in body fluids can be easily measured using geochemical techniques that rely only on standard materials and equipment, and for which the underlying concepts are already well established in the field of noble-gas geochemistry. PMID:24811123

Tomonaga, Yama; Brennwald, Matthias S; Livingstone, David M; Tomonaga, Genevive; Kipfer, Rolf

2014-01-01

242

A mass spectrometric line for tritium analysis of water and noble gas measurements from different water amounts in the range of microlitres and millilitres  

Microsoft Academic Search

This paper describes the procedure followed for noble gas measurements for litres, millilitres and microlitres of water samples in our laboratory, including sample preparation, mass spectrometric measurement procedure, and the complete calibrations. The preparation line extracts dissolved gases from water samples of volumes of 0.2? l to 3l and it separates them as noble and other chemically active gases. Our

Laszlo Papp; Laszlo Palcsu; Zoltan Major; Laszlo Rinyu; Istvan Tth

2012-01-01

243

Silicate Perovskite and the Terrestrial Noble Gas Signature  

NASA Astrophysics Data System (ADS)

The relative abundance of noble gases on Earth is very different from the solar abundance pattern. All noble gases are strongly depleted mostly due to loss to space. However, xenon appears to be particularly depleted on Earth. This cannot be explained simply by hydrodynamic escape. Moreover, the amount of radiogenic 40Ar that should have been produced over Earths history is twice larger than the amount of Ar found in the atmosphere. These observations may be related to trapping of noble gases in some lower mantle reservoir. Numerous studies on noble gas solubility and noble gas partitioning involving upper mantle minerals demonstrated that noble gases are extremely incompatible. However, the solubility of noble gases in MgSiO3 perovskite, the main constituent of the lower mantle, has never been measured. We have therefore investigated the solubility of argon and xenon in both pure and Al-bearing magnesium silicate perovskite. Glasses of appropriate composition were loaded together with 40-80 bars of Ar or Xe into platinum capsules and converted to dense crystalline phases in a 1200t multianvil press at 1200C and 10GPa. Recovered capsules were re-run in a 5000t multianvil press at 1800C and 23 GPa for 1 h. Numerous empty cavities indicating saturation of the samples with Ar or Xe were observed in the run products. Electron microprobe analyses of recovered perovskites show that 0.5-1.3 wt% of Ar is dissolved in perovskite whereas no Ar was found in other high-pressure minerals (e.g. ringwoodite, majorite, akimotoite; detection limit 35-40 ppm by weight). The scatter in measured Ar content is probably due to release of gas under the electron beam. Perovskite produced in the presence of excess xenon contained numerous cavities, sometimes still filled by high-density xenon after the experiment. However, microprobe analyses of the perovskite showed xenon contents close to detection limit (about 100 ppm). Xenon solubility therefore appears to be orders of magnitude lower than argon solubility in perovskite. The high solubility of argon in perovskite is probably due to the presence of oxygen vacancies that are being filled by argon. The occurrence of oxygen vacancies in magnesium silicate perovskite is well documented. Microprobe analyses of our samples show a clear deficiency in Si, which for reasons of charge balance requires oxygen vacancies. Moreover, up to 0.5 wt % Ar was found in occasionally grown phase X, which contains abundant potassium vacancies, comparable in size with argon atom. The low solubility of xenon in perovskite is probably related to its large atomic radius, which makes it unable to occupy the oxygen vacancies. Crystallization of perovskite from a magma ocean at early stages of the Earth formation could trap a significant fraction of primordial argon, but much less xenon. The primordial atmosphere was likely lost at some stage due to strong hydrodynamic escape and/or the effects of a giant impact. Therefore, the observed noble gas pattern of the Earths atmosphere is probably a combination of such massive loss of noble gases during the Hadean and later outgassing of a lower mantle noble gas component selectively depleted in xenon. Accordingly, a layering in the noble gas content of the mantle is a primary feature, in contrast to the traditional models of noble gas evolution.

Shcheka, S. S.; Keppler, H.

2010-12-01

244

Isotopic fingerprints of shallow gases in the Western Canadian sedimentary basin: tools for remediation of leaking heavy oil wells  

Microsoft Academic Search

Thousands of wells have been drilled in northeastern Alberta and adjacent Saskatchewan in order to develop the heavy oil reservoirs of the Lower Cretaceous Mannville Group. In a large number of these wells, vertical migration of gas from unknown sources to the surface via well casings and surrounding soils represents a serious environmental problem. Mud samples from new wells drilled

Devon Rowe; Karlis Muehlenbachs

1999-01-01

245

Noble gas isotopic composition as a key reference parameter in a planetary atmospheric evolution model  

NASA Astrophysics Data System (ADS)

The isotopic composition of noble gases is a key reference parameter in discussing the evolution of planetary atmospheres. Currently, two widely occurring noble gas components are identified in the early solar system, one is the Solar Wind noble gas (SW-noble gas, hereafter) and another is the Q-noble gas in unaltered meteorites: both noble gases are characterized by their ubiquitous occurrence and high isotopic homogeneity. Since the SW-noble gas is directly ejected from the Sun, it has been assumed to be a good proxy of the average noble gas isotopic composition in the Sun, namely the solar noble gas. The systematic enrichment of the heavier isotopes in the Q-noble gas relative to the SW-noble gas is then commonly attributed to its isotopic fractionation from the SW-noble gas. However, the isotopic compositions of the SW-noble gas either implanted on lunar soils or trapped by artificial targets show considerable isotopic variation depending on the velocity of the Solar Wind. Therefore, it is important to examine how closely the SW-noble gas represents the indigenous solar noble gas component or the mean isotopic composition of noble gases of the Sun. Here we show that the isotopic composition of the SW-noble gas is substantially fractionated relative to the solar value, and therefore should not be used as a reference parameter. We further suggest that the post D-burning Q-noble gas (see below) is the better proxy of the solar noble gas, and this should be used as a reference of the Solar noble gas isotopic composition in discussing the planetary atmospheric evolution. The most distinct difference between the Q- and the SW-noble gas is apparent in a 3He/4He isotopic ratio: 4.64e-4 in Q-He [1], but 1.23e-4 in SW-He[2]. The difference is attributed to the conversion of deuteron (D) to 3He in the Sun, namely the D-burning [3], due to high temperature during the pre-main sequence stage of the Sun. With the use of recent data on D/H ratios from helio-seismology [4] and spectroscopic observation of the inter-stellar cloud [5], we estimated that the 3He/4He ratio in the post D-burning He in the Sun is 3.98e-4. The latter value is considerably smaller than the recent estimate of the SW-He ratio by the GENESIS mission of 3He/4He = 4.64e-4 [2]. We conclude that this difference is due to isotopic fractionation during the ejection of the Solar Wind from the solar atmosphere. The further interesting implication of this conclusion is that the marked difference in 3He/4He between the SW- and Q-noble gases can be used as an unique chronological marker in the planetary atmospheric evolution. [1] Busemann H. et al., Meteoritics & Planetary Science, 35, 949-973, 2000. [2] Heber V. et al. Geochimica Cosmochimica Acta, 73, 7414-7432, 2009. [3] Geiss J. and Reeve H. Astronomy Astrophysics, 18, 126-132, 1972. [4] Basu S. and Antia H.M. Astrophysical J. , 606:L85-L88, 2004. [5] Linsky J.L. et al. Astrophysical J., 647:1106-1124, 2006.

Ozima, M.

2010-12-01

246

Automation of a mass spectrometer and extraction line for the determination of noble gas isotopes in rocks  

Microsoft Academic Search

This paper describes the automation of an extraction line and mass spectrometer for the determination of noble gas isotope concentrations in rock and mineral samples, housed in the Isotope Geochemistry Facility at Woods Hole Oceanographic Institution (WHOI). The gas extraction occurs in an automated ultra-high-vacuum system designed and fabricated at WHOI. The noble gases of interest are extracted in vacuo

R. Singer; J. Curtice; M. Kurz

2000-01-01

247

Accurate analysis of noble gas concentrations in small water samples and its application to fluid inclusions in stalagmites  

Microsoft Academic Search

The concentrations of dissolved noble gases in water are widely used as a climate proxy to determine noble gas temperatures (NGTs); i.e., the temperature of the water when gas exchange last occurred. In this paper we make a step forward to apply this principle to fluid inclusions in stalagmites in order to reconstruct the cave temperature prevailing at the time

Yvonne Scheidegger; Heinrich Baur; Matthias S. Brennwald; Dominik Fleitmann; Rainer Wieler; Rolf Kipfer

2010-01-01

248

Pressure broadening and shift of the potassium D1 transition by the noble gases and N2, H2, HD, D2, CH4, C2H6, C3H8, and n-C4H10 with comparison to other alkali rates  

NASA Astrophysics Data System (ADS)

The pressure broadening and shift rates for the potassium D1(42P?42S) transition with the noble gases and 3He, H2, HD, D2, N2, CH4, C2H6, C3H8, and n-C4H10 were obtained for pressures up to 80 Torr and at a temperature of 55 C by means of laser absorption spectroscopy. The collisional broadening rate, ?L, for He, 3He, Ne, Ar, Kr, Xe, H2, HD, D2, N2, CH4, C2H6, C3H8, and n-C4H10 are 13.08, 17.46, 6.14, 19.45, 16.64, 20.02, 22.15, 19.36, 17.47, 17.78, 29.35, 26.63, 27.27, and 27.85 MHz/Torr, respectively. The uncertainty in the broadening rates is typically less than 1.6%. The corresponding pressure induced shift rates, ?, are 1.63, 6.82, -1.27, -6.44, -5.42, -6.54, -5.34, -5.10, -4.70, -6.80, -7.41, -8.32, -8.59, and -8.80 MHz/Torr with a uncertainty of less than 2.4%. A comparison with the other alkali D1 broadening cross-sections is presented.

Pitz, Greg A.; Sandoval, Andrew J.; Zameroski, Nathan D.; Klennert, Wade L.; Hostutler, David A.

2012-03-01

249

An overview of noble gas (He, Ne, Ar, Xe) contents and isotope signals in terrestrial diamond  

NASA Astrophysics Data System (ADS)

The noble gas geochemistry of different types of terrestrial diamond including coated stones, alluvial diamonds, framesites, carbonados and impact diamonds yields a wealth of information on the sources of volatiles responsible for diamond formation. We present an illustrated compilation of published analyses of noble gases in different types of natural diamond. Noble gases in diamond record primary signatures from the mantle indicative of their integrated sources, and, the contribution of different metasomatic agents including subducting fluids and kimberlitic melt sampled during diamond growth. In addition, they show evidence of secondary processes such as resorption. Most data are available for coated stones, which trap abundant volatile-rich microscopic inclusions in their rims. While the coated stones are dominated by Mid-Oceanic-Ridge-Basalt (MORB) type noble gas signatures, the other diamond types contain predominantly crustal and atmospheric components although some mantle gases may be present, the latter indicated in elevated 20Ne/22Ne and/or 129Xe/132Xe ratios relative to atmospheric values. Some alluvial diamonds have very high 3He/4He that may represent the presence of a solar component trapped during their formation, but are just as likely to be the result of cosmogenic 3He implantation during their prolonged residence at the Earth's surface. Oceanic-Island-Basalt (OIB) type noble gases occur in nanometer sized inclusions in metamorphic diamond from Kazakhstan, yet their significance as a fingerprint of mantle processes is not fully understood. Implanted noble gases occur near the outer surfaces of individual crystals, and are generally not a major hindrance for the study of mantle signatures, except for polycrystalline diamond like framesites with small grain size. Some diamonds including the polycrystalline carbonados, are dominated by crustal noble gases with no discernible mantle component evidenced by very low 3He/4He and 20Ne/22Ne ratios, and very high 21Ne/22Ne and 131,134,136Xe/132Xe ratios. In many diamonds, variations in both concentration and isotopic composition within samples from the same geographical location require complex diamond growth. For example, coated stones of Zaire trap noble gases from multiple sources and different generations of diamond growth. Thus noble gas studies have the potential to record major processes during the complex growth histories of natural diamond and also to provide valuable information about the sub-continental mantle. Noble gas signatures may be affected by diffusive losses, notably in some framesites.

Basu, S.; Jones, A. P.; Verchovsky, A. B.; Kelley, S. P.; Stuart, F. M.

2013-11-01

250

On the possible noble gas deficiency of Pluto's atmosphere  

NASA Astrophysics Data System (ADS)

We use a statistical-thermodynamic model to investigate the formation and composition of noble-gas-rich clathrates on Pluto's surface. By considering an atmospheric composition close to that of today's Pluto and a broad range of surface pressures, we find that Ar, Kr and Xe can be efficiently trapped in clathrates if they formed at the surface, in a way similar to what has been proposed for Titan. The formation on Pluto of clathrates rich in noble gases could then induce a strong decrease in their atmospheric abundances relative to their initial values. A clathrate thickness of order of a few centimeters globally averaged on the planet is enough to trap all Ar, Kr and Xe if these noble gases were in protosolar proportions in Pluto's early atmosphere. Because atmospheric escape over an extended period of time (millions of years) should lead to a noble gas abundance that either remains constant or increases with time, we find that a potential depletion of Ar, Kr and Xe in the atmosphere would best be explained by their trapping in clathrates. A key observational test is the measurement of Ar since the Alice UV spectrometer aboard the New Horizons spacecraft will be sensitive enough to detect its abundance 10 times smaller than in the case considered here.

Mousis, Olivier; Lunine, Jonathan I.; Mandt, Kathleen E.; Schindhelm, Eric; Weaver, Harold A.; Alan Stern, S.; Hunter Waite, J.; Gladstone, Randy; Moudens, Audrey

2013-07-01

251

Study of performance characteristics of noble metal thermocouple materials to 2000 C  

NASA Technical Reports Server (NTRS)

Three performance characteristics of noble metal thermocouples in various environments are discussed. Catalytic effects cause significant errors when noble metal thermocouple materials are exposed to air containing unburned gases in temperature ranges from 25 C to 1500 C. The thermoelectric stability of the iridium 40 rhodium to iridium thermocouple system at 2000 C in an oxidizing medium is described. The effects of large and small temperature gradients on the accuracy and stability of temperature measurements are analyzed.

Freeze, P. D.; Thomas, D.; Edelman, S.; Stern, J.

1972-01-01

252

Greenhouse Gases  

MedlinePLUS

... are greenhouse gases? Many chemical compounds present in Earth's atmosphere behave as 'greenhouse gases'. These are gases ... direct sunlight (relative shortwave energy) to reach the Earth's surface unimpeded. As the shortwave energy (that in ...

253

Manure Gases  

MedlinePLUS

... gases of most concern are ammonia and hydrogen sulfide. Other gases of concern include methane and carbon ... Since most of these gases in particular hydrogen sulfide are heavier-than-air, they tend to settle ...

254

Perspectives of hyperpolarized noble gas MRI beyond 3He  

NASA Astrophysics Data System (ADS)

Nuclear Magnetic Resonance (NMR) studies with hyperpolarized (hp) noble gases are at an exciting interface between physics, chemistry, materials science and biomedical sciences. This paper intends to provide a brief overview and outlook of magnetic resonance imaging (MRI) with hp noble gases other than hp 3He. A particular focus are the many intriguing experiments with 129Xe, some of which have already matured to useful MRI protocols, while others display high potential for future MRI applications. Quite naturally for MRI applications the major usage so far has been for biomedical research but perspectives for engineering and materials science studies are also provided. In addition, the prospects for surface sensitive contrast with hp 83Kr MRI is discussed.

Lilburn, David M. L.; Pavlovskaya, Galina E.; Meersmann, Thomas

2013-04-01

255

Perspectives of hyperpolarized noble gas MRI beyond 3He.  

PubMed

Nuclear Magnetic Resonance (NMR) studies with hyperpolarized (hp) noble gases are at an exciting interface between physics, chemistry, materials science and biomedical sciences. This paper intends to provide a brief overview and outlook of magnetic resonance imaging (MRI) with hp noble gases other than hp (3)He. A particular focus are the many intriguing experiments with (129)Xe, some of which have already matured to useful MRI protocols, while others display high potential for future MRI applications. Quite naturally for MRI applications the major usage so far has been for biomedical research but perspectives for engineering and materials science studies are also provided. In addition, the prospects for surface sensitive contrast with hp (83)Kr MRI is discussed. PMID:23290627

Lilburn, David M L; Pavlovskaya, Galina E; Meersmann, Thomas

2013-04-01

256

Perspectives of hyperpolarized noble gas MRI beyond 3He  

PubMed Central

Nuclear Magnetic Resonance (NMR) studies with hyperpolarized (hp) noble gases are at an exciting interface between physics, chemistry, materials science and biomedical sciences. This paper intends to provide a brief overview and outlook of magnetic resonance imaging (MRI) with hp noble gases other than hp 3He. A particular focus are the many intriguing experiments with 129Xe, some of which have already matured to useful MRI protocols, while others display high potential for future MRI applications. Quite naturally for MRI applications the major usage so far has been for biomedical research but perspectives for engineering and materials science studies are also provided. In addition, the prospects for surface sensitive contrast with hp 83Kr MRI is discussed.

Lilburn, David M.L.; Pavlovskaya, Galina E.; Meersmann, Thomas

2013-01-01

257

Vesiculation, melt formation, noble gas/nitrogen behaviour, and impact chronology on a planetary regolith : the case of Benccubbin (CB) meteorite  

NASA Astrophysics Data System (ADS)

The Benccubbin meteorite is a member of the CB peculiar meteorite family, which all have reduced silicates, metal zoning, solar Ni/Co and large enrichments in 15N, that have been regarded as relics of their very primitive character. However, these meteorites also show tugsten isotopic ratios suggesting metal differentiation events several Ma after start of solar system formation. The Benccubbin mineralogy is best explained as being an heterogeneous planetary regolith containing clasts of different origins (e.g., CO, CI chondrules and clasts, silicates of unknown origin). This meteorite presents evidence of having been impacted, such as melt, temperature gradient recorded at the silicate/metal interface, and textures indicative of rapid cooling. Notably, Benccubbin contains vesicles in several phases : partially molten silicate clasts and CO chondrules, impact melt, and the so-called bubble grains 1. We have analysed several Benccubbin mineral and metal phases for N and noble gas isotopes and abundances by both laser fusion and vacuum crushing. 15N-rich nitrogen (d15N up to +1,000 per mil) is ubiquituous, particularly inside vesicles, and is associated with noble gases. Notably, N and noble gases appear to have largely exchanged between silicate and vesicles, reaching locally equilibrium partitioning. Gases are still released after extensive crushing up to 4,000 strokes, in contrast to the case of MORB glasses and suggesting a foam-like, decompression structure of the impacted melt. N and Ar correlate well, showing that the N solubility was comparable to that of Ar and therefore that the redox conditions were above IW, according to 2. From the N content of the glass, we estimate that it equilibrated with a vapor plume in which the pressure of nitrogen was ~300 Bar. Radiogenic 40Ar is present inside the vesicles, showing that the vesiculation event was not an early process. Ar-Ar dating of Benccubbin suggests involvement in an impact around 4.2 Ga. In contrast to very variable N and primordial noble gas contents among different phases, cosmogenic 3He, 21Ne and 38Ar abundances are uniform, and vesicles contain little cosmogenic isotopes, showing that space exposure occurred after the vesicle forming impact event. Hence the event that led to the ejection of the Benccubbin meteorite was distinct from the vesiculation one, and occurred 40-50 Ma ago according to cosmogenic 3He, 21Ne and 38Ar isotopes and 38Ar-37Ar correlation. Noble gases have been well preserved in vesicles from cosmic ray isotope contributions, permitting to determine their origin precisely despite extensive exposure in space. Noble gases present Q-like isotopic ratios but highly fractionated abundances with respect to Q. The fact that comets are definitely rich in 15N 3 and may also have Q-like noble gas signature in their refractory phases 4 is suggestive of a possible link between cometary matter and CBs. 1. Perron, C., Fieni, C. and Guilhaumou, N. Geochim.Cosmochim. Acta 72, 959-977 (2008). 2. Libourel, G., Marty, B. and Humbert, F. Geochim. Cosmochim. Acta 67, 4123-4135 (2003). 3. Bockelee-Morvan, D. et al. Large excess of heavy nitrogen in both hydrogen cyanide and cyanogen from comet 17P/Holmes. Ap J.679, L49-L52 (2008). 4. Marty, B. et al. Science 319, 75-78 (2008).

Marty, B.; Turner, G.; Kelley, S. P.

2008-12-01

258

High Sensitivity Mass Spectrometer for Noble Gas Analysis  

Microsoft Academic Search

A high-sensitivity mass spectrometer for noble gas analysis is described in detail. Ultra-high vacuum techniques have been used throughout so that small rare gas samples can be closed off within the spectrometer envelope and analyzed statically. This procedure is of considerable advantage in analyzing argon and lighter rare gases. The background spectrum when the spectrometer pressure is 51010 mm Hg

John H. Reynolds

1956-01-01

259

High temperature, oxidation resistant noble metal-Al alloy thermocouple  

NASA Technical Reports Server (NTRS)

A thermocouple is disclosed. The thermocouple is comprised of an electropositive leg formed of a noble metal-Al alloy and an electronegative leg electrically joined to form a thermocouple junction. The thermocouple provides for accurate and reproducible measurement of high temperatures (600 - 1300 C) in inert, oxidizing or reducing environments, gases, or vacuum. Furthermore, the thermocouple circumvents the need for expensive, strategic precious metals such as rhodium as a constituent component. Selective oxidation of rhodium is also thereby precluded.

Smialek, James L. (inventor); Gedwill, Michael G. (inventor)

1994-01-01

260

Pressure broadening and shift of the cesium D{sub 1} transition by the noble gases and N{sub 2}, H{sub 2}, HD, D{sub 2}, CH{sub 4}, C{sub 2}H{sub 6}, CF{sub 4}, and {sup 3}He  

SciTech Connect

The pressure broadening and shift rates for the cesium D{sub 1} (6 {sup 2}P{sub 1/2}<-6 {sup 2}S{sub 1/2}) transition with the noble gases and N{sub 2}, H{sub 2}, HD, D{sub 2}, CH{sub 4}, C{sub 2}H{sub 6}, CF{sub 4}, and {sup 3}He were obtained for pressures less than 300 torr at temperatures under 65 deg. C by means of laser absorption spectroscopy. The collisional broadening rate, gamma{sub L}, for He, Ne, Ar, Kr, Xe, N{sub 2}, H{sub 2}, HD, D{sub 2}, CH{sub 4}, C{sub 2}H{sub 6}, CF{sub 4}, and {sup 3}He are 24.13, 10.85, 18.31, 17.82, 19.74, 16.64, 20.81, 20.06, 18.04, 29.00, 26.70, 18.84, and 26.00 MHz/torr, respectively. The corresponding pressure-induced shift rates, delta, are 4.24, -1.60, -6.47, -5.46, -6.43, -7.76, 1.11, 0.47, 0.00, -9.28, -8.54, -6.06, and 6.01 MHz/torr. These rates have then been utilized to calculate Lennard-Jones potential coefficients to quantify the interatomic potential surfaces. The broadening cross section has also been shown to correlate with the polarizability of the collision partner.

Pitz, Greg A.; Wertepny, Douglas E.; Perram, Glen P. [Department of Engineering Physics, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson Air Force Base, Ohio 45433-7765 (United States)

2009-12-15

261

The trapped noble gas component in achondrites  

NASA Astrophysics Data System (ADS)

The trapped noble gases Ar, Kr and Xe in several achondrites were analysed. We chose separates of the lodranites Lodran and Graves Nunataks 95209 and bulk samples of the Tatahouine diogenite, Pasamonte eucrite, five aubrites and two angrites. Among these, Lodran, Tatahouine, Pasamonte and the aubrite Norton County have been reported to contain U-Xe, a noble gas component assumed to be the most primitive component in the solar system. U-Xe might have been incorporated into the early Earth. We found large concentrations of Xe in several separates of the Lodran lodranite, however, none of the measurements revealed U-Xe composition. The Xe composition of all achondrites can straightforwardly be explained with mixtures of trapped common Xe-Q, absorbed air and various amounts of fissiogenic and cosmogenic Xe. Reanalysis of literature data for Pasamonte, Angra dos Reis and some aubrites is consistent with Xe-Q as the trapped endmember component and contributions of fissiogenic Xe. The presence of Xe-Q in many primitive achondrites is in agreement with the formation of their parent bodies from originally chondritic precursor material. The Ar-Xe elemental composition of Lodran and the aubrites indicate subsolar composition, which is commonly found in E chondrites. This result supports a model of formation of the aubrites from E-chondritic precursor material.

Busemann, Henner; Eugster, Otto

2002-12-01

262

Condensation process for separating air pollutants from waste gases, and specifically from flue gases  

Microsoft Academic Search

A condensation process for separation of air pollutants from waste gases and, specifically, from flue gases. Sulfurous components of the waste gases in particular, but also heavy metals contained therein, can be separated at a very high degree of separation by fractional condensation when certain parameters are followed. The energy withdrawn from the waste gases during condensation is available as

Faatz

1984-01-01

263

Noble gas content and isotope abundances in phases of the Saint-Aubin (UNGR) iron meteorite  

NASA Astrophysics Data System (ADS)

We analyzed the noble gas isotopes in the Fe-Ni metal and inclusions of the Saint-Aubin iron meteorite, utilizing the stepwise heating technique to separate the various components of noble gases. The light noble gases in all samples are mostly cosmogenic, with some admixture from the terrestrial atmosphere. Total abundances of noble gases in metal are one of the lowest found so far in iron meteorites and the 4He/21Ne ratio is as high as 503, suggesting that the Saint-Aubin iron meteorite was derived from a very large meteoroid in space. The exposure ages obtained from cosmogenic 3He were 9-16 Ma. Saint-Aubin is very peculiar because it contains very large chromite crystals, whichlike the metalcontain only cosmogenic and atmospheric noble gases. The noble gases in all the samples do not reveal any primordial components. The only exception is the 1000 C fraction of schreibersite which contained about 5% of the Xe-HL component. The Xe-Q and the El Taco Xe components were not found and only the Xe-HL is present in this fraction. Some presolar diamond, the only carrier for the HL component known today, must have been available during growth of the schreibersite. However, it is also possible that this excess is due to the addition of cosmogenic and fission components. In this case, all the primordial components are masked (or lost) by the later events such as cosmic-ray irradiation, heating, and radioactive decay.

Nishimura, Chikako; Matsuda, Jun-Ichi; Kurat, Gero

2008-08-01

264

Signal-to-noise ratio comparison of encoding methods for hyperpolarized noble gas MRI  

NASA Technical Reports Server (NTRS)

Some non-Fourier encoding methods such as wavelet and direct encoding use spatially localized bases. The spatial localization feature of these methods enables optimized encoding for improved spatial and temporal resolution during dynamically adaptive MR imaging. These spatially localized bases, however, have inherently reduced image signal-to-noise ratio compared with Fourier or Hadamad encoding for proton imaging. Hyperpolarized noble gases, on the other hand, have quite different MR properties compared to proton, primarily the nonrenewability of the signal. It could be expected, therefore, that the characteristics of image SNR with respect to encoding method will also be very different from hyperpolarized noble gas MRI compared to proton MRI. In this article, hyperpolarized noble gas image SNRs of different encoding methods are compared theoretically using a matrix description of the encoding process. It is shown that image SNR for hyperpolarized noble gas imaging is maximized for any orthonormal encoding method. Methods are then proposed for designing RF pulses to achieve normalized encoding profiles using Fourier, Hadamard, wavelet, and direct encoding methods for hyperpolarized noble gases. Theoretical results are confirmed with hyperpolarized noble gas MRI experiments. Copyright 2001 Academic Press.

Zhao, L.; Venkatesh, A. K.; Albert, M. S.; Panych, L. P.

2001-01-01

265

Fluorescent noble metal nanoclusters  

NASA Astrophysics Data System (ADS)

Water-soluble fluorescent metallic clusters at sizes comparable to the Fermi wavelength of an electron (0.5 nm for gold and silver) were created and their photophysical properties were investigated at the bulk and single molecule levels. We employed biocompatible dendrimer and peptide to prepare a series of strong fluorescent gold and silver clusters with chemical or photo reduction methods. Facilitated by the well-defined dendrimer size, electrospray ionization mass spectrometry indicates that the fluorescent silver nanocluster size ranges from 2 to 8 Ag atoms. The correlation of emission energy with the number of atoms, N, in each gold nanocluster is quantitatively fit for the smallest nanoclusters with no adjustable parameters by the simple scaling relation of EFermi/N1/3, in which EFermi is the Fermi energy of bulk gold. The transition energy scaling inversely with cluster radius indicates that electronic structure can be well described with the spherical jellium model and further demonstrates that these nanomaterials are "multi-electron artificial atoms". Fluorescence from these small metal clusters can be considered protoplasmonic, molecular transitions of the free conduction electrons before the onset of collective dipole oscillations occurring when a continuous density of states is reached. In addition, very strong single molecular Stokes and anti-Stokes Raman enhancement by fluorescent silver clusters was observed. Pushing to larger sizes, we also created 2nm diameter glutathione encapsulated luminescent gold nanoparticles. Distinct from similarly sized but nonluminescent gold nanoparticles, these 2 nm gold nanoparticles show bright, long lifetime emission but no plasmon absorption. The emission might arise from charge transfer between gold atoms and the thiol ligand. Providing the "missing link" between atomic and nanoparticle behavior in noble metals, these highly fluorescent, water-soluble gold and silver nanoclusters offer complementary transition energy size scalings at smaller dimensions than do semiconductor quantum dots. The unique discrete excitation and emission and strong Stokes and anti-Stokes Raman enhancement coupled with facile creation in aqueous solution open new opportunities for noble metal nanoclusters as biological labels, energy transfer pairs, and other light emitters in nanoscale electronics.

Zheng, Jie

266

Helium Solubility in Cyclosilicates and Implications for Noble Gas Recycling  

NASA Astrophysics Data System (ADS)

It is commonly assumed that noble gases strictly flux from the mantle to the atmosphere, with negligible recycling, because noble gases are thought to be extremely insoluble in all minerals. To test this hypothesis, we have experimentally determined the He solubility in a suite of cyclosilicate minerals: beryl, tourmaline and cordierite. The experiments were run in a gas pressure vessel. Run products were analyzed by UV laser ablation, noble gas mass spectrometry. He has a remarkably high solubility (>1000 ppm/1.8 kbar PHe) in cyclosilicates with nominally vacant six-member Si-Al-tetrahedra rings. Cyclosilicates with nominally occupied ring sites have substantially lower solubility. This suggests that He dissolution is facilitated by unfilled six-member rings. If true, He should have a high solubility in other minerals that include ring sites, such as phyllosilicates and amphiboles. Subduction zones commonly recycle these minerals, providing a possible mechanism for recycling of noble gases back into the mantle. Gem quality, natural, polished crystals of each mineral were placed into graphite capsules. Pure He gas was used as the pressure medium (1800 bar), allowing for precise control of PHe. Temperatures were held at 750 C and the experimental durations were 8 hours. A capsule of hydrated MgO powder was loaded in the TZM to maintain a non-zero fugacity of water during the experiment. Close visual inspection of the run products gave no indication of breakdown products. Depth profiles (10s of microns) of the mineral faces were completed using a 193 nm excimer laser. Multiple measurements were made on each phase. He concentrations were homogenous, both vertically and horizontally, indicating a close approach to equilibrium and absence of inclusions. Compared to tourmaline, we observe that He is >1000 and >100 times more soluble in cordierite and beryl, respectively. The ring sites, also known as A sites, in beryl and cordierite are nominally vacant, where as the ring sites in tourmaline, with the exception of foitite, are nominally full, suggesting the density of vacant rings in cyclosilicates is a primary control on He solubility. Ring sites are large (hosting LILEs) and have no net charge when vacant, making them an ideal candidate for hosting noble gases in general. This is also evidenced by high Ar solubilties (750 ppm/kbar PAr) measured in cubic leucite with similar lattice structures (1) and large He and Ar excesses reported for cyclosilicates (2). Many subduction zone minerals contain six-member Si-Al-tetrahedra rings (mica group, serpentine group, amphibole group and chlorite)(3,4). If recycled, these minerals could constitute a significant flux of noble gases back into the mantle. The magnitude and consequences of the flux will depend on the fugacity of noble gases during mineral formation and on how closed the system remains after eventual breakdown. 1. Wartho et al, Am Min, 2005 2. Damon and Kulp, Am Min, 1958 3. Schmidt and Poli, EPSL, 1998 4. Green et al, Nature, 2010

Jackson, C.; Kelley, S. P.; Cooper, R. F.; Parman, S. W.

2011-12-01

267

Dating native gold by noble gas analyses  

NASA Technical Reports Server (NTRS)

Our recent work on He, Ne, and Ar in Alpine gold samples has demonstrated that gold is extremely retentive for He and could thus, in principle, be used for U/Th-He-4 dating. For vein-type gold from Brusson, Northern Italy, we derived a U/Th-He-4 age of 36 Ma, in agreement with the K-Ar formation age of associated muscovites and biotites. However, in placer gold from the Napf area, Central Switzerland, we observed large excesses of both He-4 and radiogenic Ar-40 (Ar-40 sub rad, defined as Ar-40-295.5-Ar-.36). The gas release systematics indicate two distinct noble gas components, one of which is released below about 800 C and the other one at the melting point of gold (1064 C). We now present results of He and Xe measurements in a 1 g placer gold sample from the river Kruempelgraben, as well as He and Ar data for Brusson vein-type gold and for gold from the Lily Gold Mine, South Africa. We calculate reasonable U/Th-He-4 as well as U-Xe ages based on those gases which are released at approximately 800 C. Probably the low-temperature components represent in-situ-produced radiogenic He and fission Xe, whereas the gases evolving when gold melts have been trapped during gold formation. Therefore, only the low-temperature components are relevant for dating purposes.

Niedermann, S.; Eugster, O.; Hofmann, B.; Thalmann, CH.; Reimold, W. U.

1993-01-01

268

Relationship between recent cave temperatures and noble gas temperatures derived from fluid inclusions of modern soda straw stalactites  

NASA Astrophysics Data System (ADS)

Recently, strong effort is devoted to establish a new method to derive palaeotemperatures from noble gas (Ne, Ar, Kr, Xe) concentrations dissolved in fluid inclusions of speleothems [1-2]. It has been already shown that the water content of the speleothems can be determined via the water vapour pressure after the water has been released from the carbonate samples and collected in a cold finger and then heated up to room temperature. Additionally, the noble gas contents can be precisely measured with noble gas mass spectrometers. Based on these noble gas concentration data sets, a so-called noble gas temperature (NGT) can be calculated meaning a temperature at which the noble gases have been dissolved in water. To use these NGT's as a palaeoclimate proxy, one of the main questions is how these noble gas temperatures reflect the prevailing cave temperature in which the carbonate has grown. We studied noble gas significances in recent soda straw stalactites from more than ten Central European caves covering a temperature range of 1 to 14 C. Kluge et al. (2008) has shown the soda straw stalactites might contain less excess air, hence they are more suitable samples to derive NGT's, because noble gas abundances from large air inclusions can mask the temperature information. The 14C ages of these soda straw dripstones were obtained to be recent or at least Holocene ages. Thus one can assume that the cave temperatures during carbonate formation were as same as at present. We measured the water and noble gas contents of numerous carbonate samples from soda straw stalactites and calculated noble gas temperatures by a precision of 1 C or better. Comparing these temperatures with cave temperatures we obtained that they agree well within the uncertainty of the noble gas temperature determination. Therefore, we can conclude if diffusion of noble gas isotopes does not play a significant role in the carbonate lattice this new tool helps the palaeoclimate community to gain reliable palaeotemperature information on the time range from present back to hundred thousand years. [1] Kluge T., Marx T., Scholz D., Niggermann S., Mangini A., Aeschbach-Hertig W., 2008. A new tool for palaeoclimate reconstruction: Noble gas temperatures from fluid inclusions in speleothems. Earth and Planetary Science Letters 269, 408-415. [2] Brennwald M.S., Scheidegger Y., Tomonaga Y., Holzner C.P., Wieler R., Kipfer R., 2006. New applications of noble gases as environmental proxies in unusual aquatic environments. Geochimica et Csomochimica Acta 70, Supplement, A66.

Palcsu, Laszlo; Papp, Laszlo; Major, Zoltan; Molnar, Mihaly

2010-05-01

269

Production Rates for Noble-Gas Isotopes in Eucrites  

NASA Technical Reports Server (NTRS)

To get cosmic-ray exposure ages of meteorites from measured concentrations of cosmic-ray-produced ("cosmogenic") noble-gas isotopes, production rates for those isotopes are needed. The best production rates take into consideration the composition of the meteorite and the "shielding" of the sample (the pre-atmospheric size and shape of the meteoroid and the sample s location in the meteoroid). For ordinary chondrites, there have been many sets of measurements to establish production systematics. The Ne-22/Ne-21 is often used to help to get shielding-dependent production rates. We report here numerical simulations for the production of isotopes of the light noble gases He, Ne, and Ar in both basaltic and cumulate eucrites for several sizes.

Reedy, R. C.; Kim, K. J.

2004-01-01

270

Noble Gas Isotopic Evidence for Primordial Evolution of the Earth's Atmosphere in Three Distinct Stages  

Microsoft Academic Search

The deep Earth is the key to understanding the primordial evolution of the Earth's atmosphere. However the atmosphere was not derived by degassing of the Earth, as widely held. Isotopic characterization of mantle noble gases and modeling based on this information [1] suggests the atmosphere experienced a 3-stage early history. This follows from 5 basic observations: (i) Ne in the

C. L. Harper Jr.; S. B. Jacobsen

1995-01-01

271

Calibration of HPGe gamma-ray detectors for measurement of radioactive noble gas sources  

Microsoft Academic Search

Measurements of radioactive noble gases are routinely made with gamma-ray spectrometers. This work describes the calibration of high purity germanium detectors provided by the full-energy-peak efficiency as a function of the gamma-ray energy. A comparison of measured efficiency values with a new, simplified method based on a direct mathematical method is given here.

L. Pibida; S. S. Nafee; M. Unterweger; M. M. Hammond; L. Karam; M. I. Abbas

2007-01-01

272

Pressure broadening and shift of the cesium D{sub 2} transition by the noble gases and N{sub 2}, H{sub 2}, HD, D{sub 2}, CH{sub 4}, C{sub 2}H{sub 6}, CF{sub 4}, and {sup 3}He with comparison to the D{sub 1} transition  

SciTech Connect

The pressure broadening and shift rates for the cesium D{sub 2} (6 {sup 2}P{sub 3/2} (<-) 6 {sup 2}S{sub 1/2}) transition with the noble gases and N{sub 2}, H{sub 2}, HD, D{sub 2}, CH{sub 4}, C{sub 2}H{sub 6}, CF{sub 4}, and {sup 3}He were obtained for pressures less than 300 Torr at a temperature of 40 deg. C by means of laser absorption spectroscopy. The collisional broadening rate {gamma}{sub L} for He, Ne, Ar, Kr, Xe, N{sub 2}, H{sub 2}, HD, D{sub 2}, CH{sub 4}, C{sub 2}H{sub 6}, CF{sub 4}, and {sup 3}He are 20.59, 9.81, 16.47, 15.54, 18.41, 19.18, 27.13, 28.24, 22.84, 25.84, 26.14, 17.81, and 22.35 MHz/Torr, respectively. The uncertainty in the broadening rates is typically less than 0.3%. The corresponding pressure-induced shift rates {delta} are 0.69, -2.58, -6.18, -6.09, -6.75, -6.20, -4.83, -4.49, -4.54, -8.86, -9.38, -6.47, and 0.60 MHz/Torr with an uncertainty of less than 0.04 MHz/Torr. With the exception of diatomic collision partners, the broadening rates for Cs D{sub 2} are 5%-15% less than the rates for Cs D{sub 1}. For light collision partners with a blue shift, the D{sub 1} is shifted more than the D{sub 2} line. The broadening cross sections for Cs and Rb are similar. However, the cross sections for K are about 70% larger and for Na, about 30% less.

Pitz, Greg A.; Fox, Charles D.; Perram, Glen P. [Department of Engineering Physics, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson Air Force Base, Ohio, 45433-7765 (United States)

2010-10-15

273

Mass Spectrometry Analysis of Noble Gases Produced in Spallation Reactions.  

National Technical Information Service (NTIS)

Cross sections for exp 20 Ne, exp 21 Ne, exp 22 Ne and exp 36 Ar, exp 38 Ar, exp 39 Ar, exp 42 Ar produced in aluminium and copper targets bombarded with 0.08, 0.15, 0.6, 1.05 and 24GeV protons have been measured with high sensitivity mass spectrometer. (...

M. F. Heland

1976-01-01

274

X-ray transitions from antiprotonic noble gases  

NASA Astrophysics Data System (ADS)

The onset of antiprotonic X-ray transitions at high principal quantum numbers and the occurrence of electronic X-rays in antiprotonic argon, krypton, and xenon has been analyzed with the help of Multiconfiguration Dirac-Fock calculations. The shell-by-shell ionisation by Auger electron emission, characterised by appearance and disappearance of X-ray lines, is followed through the antiprotonic cascade by considering transition and binding energies of both the antiproton and the remaining electrons. Electronic lines could be attributed partly to specific states of the antiprotonic atom de-excitation.

Gotta, D.; Rashid, K.; Fricke, B.; Indelicato, P.; Simons, L. M.

2008-04-01

275

Noble Gases in the LEW 88663 L7 Chondrite  

Microsoft Academic Search

LEW88663 and some meteorites (e.g. Shaw) are the most highly metamorphosed meteorites among L group chondrites. Although the abundances of lithophile elements and oxygen isotopic compositions of the L7 chondrite LEW88663 (total recovered mass: 14.5g) are close to those of the range for L chondrites [1,2], metallic iron is absent and concentrations of siderophile elements are about half of typical

Y. N. Miura; N. Sugiura; K. Nagao

1995-01-01

276

Nitrogen, Carbon, and Noble Gases in Apollo Lunar Samples  

NASA Astrophysics Data System (ADS)

A suite of five powdered lunar basalt samples have been analysed for nitrogen, carbon, helium, neon, and argon, using a high-sensitivity stepped combustion mass spectrometer system at the Open University, UK. Preliminary results indicate the presence of cosmogenic nitrogen and carbon, released in small amounts at high temperatures, as well as small amounts of cosmogenic neon and argon (mixed with a trapped non-cosmogenic component). Low temperature steps are dominated by contamination release, although 15555 displays an unusually abundant, isotopically light carbon component, released at 500 C.

Mortimer, J.; Verchovsky, A. B.; Anand, M.

2013-09-01

277

Noble gases in hydrothermal plumes of Loihi Seamount  

NASA Astrophysics Data System (ADS)

Seawater samples from hydrothermal plumes of Loihi Seamount show very high 3He/ 4He ratios (up to 15.8 10 -6) and 4He/ 20Ne ratios higher than that of air-saturated seawater (ASSW). The 3He/ 4He ratio in the source from which the helium is released into the seawater is estimated as (23.1 2.3) 10 -6 from the correlation plot of 3He/ 20Ne vs. 4He/ 20Ne. The 3He/heat ratio at Loihi is 5-49 times higher than that at the Galapagos Rift and at 21N EPR. The difference may be attributed to the differences in the structure of the mantle beneath hot spots and the mid-ocean ridge, the former representing the deeper mantle region and the latter the shallower, depleted mantle. These observations are consistent with the view that helium in hydrothermal plumes of Loihi Seamount was derived from a deeper mantle region via a hot spot, where more primordial helium is still preserved.

Kodera, Masako; Igarashi, George; Ozima, Minoru

1988-02-01

278

The Potential for Dating Groundwater Using Radiogenic Noble Gases  

SciTech Connect

The accumulation in groundwater of products from the radioactive decay of elements naturally found in rocks offers a potential for measuring the time that the groundwater has been contact with the rock. This dating method has an advantage over using decay products from the atmosphere in that the amount of decay products increases with age rather than decreases. However, different decay products accumulate at different rates and, thus, have a different potential usefulness in age determinations. The most useful decay product is helium, produced from uranium and thorium. The use of Ar-40 produced from potassium is limited because Ar-40 is abundant in meteoric water. Neon, xenon and krypton are useful with great difficulty because they are produced in extremely small quantities. In general, the potential for error increases when a long time is required to produce a small quantity of the dating nuclide.

Cornman, W.R.

2001-03-23

279

Tectonic implications of radiogenic noble gases in planetary atmospheres  

SciTech Connect

An account is given of the ways in which the He-4 and Ar-40 radiogenic isotopes furnish important constraints on planetary interior tectonics. In the case of the earth, where there are such independent constraints on radiogenic isotope concentrations as observed surface heat flow, the specification of radiogenic isotope concentration allows the interpretation of data on the Ar-40 atmospheric mass and mantle He-4 in terms of models for the entire mantle and of layered mantle convection. He loss rate estimates through the Venus atmosphere indicate a flux that is nearly equal to that through the earth atmosphere. 34 references.

Turcotte, D.L.; Schubert, G.

1988-04-01

280

The Chemistry of the Noble Gases, Understanding the Atom Series.  

ERIC Educational Resources Information Center

The history of the discovery, isolation, characterization, production and use of argon, krypton, xenon, helium, and radon is followed by an account of early attempts to react them with other elements. The use of the electron shell theory of valence to explain their inertness and the reactions of chemists to the production of xenon compounds is

Chernick, Cedric L.

281

Method for the purification of noble gases, nitrogen and hydrogen  

DOEpatents

A method and apparatus for the purification and collection of hydrogen isotopes in a flowing inert gaseous mixture containing impurities, wherein metal alloy getters having the capability of sorbing non-hydrogen impurities such as oxygen, carbon dioxide, carbon monoxide, methane, ammonia, nitrogen and water vapor are utilized to purify the gaseous mixture of impurities. After purification hydrogen isotopes may be more efficiently collected. A plurality of parallel process lines utilizing metal getter alloys can be used to provide for the continuous purification and collection of the hydrogen isotopes.

Baker, John D. (Blackfoot, ID); Meikrantz, David H. (Idaho Falls, ID); Tuggle, Dale G. (Los Alamos, NM)

1997-01-01

282

Method for the purification of noble gases, nitrogen and hydrogen  

DOEpatents

A method and apparatus are disclosed for the purification and collection of hydrogen isotopes in a flowing inert gaseous mixture containing impurities, wherein metal alloy getters having the capability of sorbing non-hydrogen impurities such as oxygen, carbon dioxide, carbon monoxide, methane, ammonia, nitrogen and water vapor are utilized to purify the gaseous mixture of impurities. After purification hydrogen isotopes may be more efficiently collected. A plurality of parallel process lines utilizing metal getter alloys can be used to provide for the continuous purification and collection of the hydrogen isotopes. 15 figs.

Baker, J.D.; Meikrantz, D.H.; Tuggle, D.G.

1997-09-23

283

Shock Effects and Noble Gas Concentrations in Chondrites  

NASA Astrophysics Data System (ADS)

A correlation has been observed between radiogenic 40Ar in chondrites and their shock stages and implications for different shock histories of L and H chondrites have been pointed out [1,2]. Here we extend this investigation to nonradiogenic solar noble gases, in particular, to solar 4He and 20Ne. Such a complementary study appeared worthwhile because solar noble gases in chondrites presumably date to very early in their history. These gases are prone to be affected by shock at any time in their history. Radiogenic gases, on the other hand, are rather insensitive sensors of shock events during the first 500 Ma or so in the life of meteorites. Measured concentrations of solar 4He in bulk samples (only the highest concentration of each meteorite is taken from [3]) are given in Fig. 1 for meteorites of different shock stages. Apparently, solar He is only present in chondrites of low shock metamorphism (S1 to S3). Either solar gases were lost during or after shock event (> S3) or impacts do not subject regolithic surface material to high stages of shock metamorphism. Figure 2 shows the distribution of radiogenic 4He in H and L chondrites. As expected, a general trend of loss of radiogenic 4He (and 40Ar) with increasing shock stage is seen. However, four meteorites of shock stages S1 and S2 also have low concentrations of radiogenic 4He. Apparently, there must be loss mechanisms for noble gases besides shock. These four chondrites (Ambapur Nagla, Densemore, Menow, and Sutton) also show a deficit of cosmogenic 3He, as seen by their low 3He/21Ne ratios. This loss of cosmogenic and radiogenic gas can be explained by solar heating during the flight as meteoroids and is not due to shock metamorphism. The ratio of H to L chondrites in S1 + S2 is about 4:1 while that in S5 + S6 is about 1:10. This different distribution of shock stages between chondrite groups is also evident in the concentrations of radiogenic gases confirming distinctly different collision histories of H and L chondrite parent bodies. References: [1] St"ffler D. et al. (1991) GCA, 55, 3831-3844. [2] St"ffler D. et al. (1992) Meteoritics, 24, 292-293. [3] Schultz L. and Kruse H. (1989) Meteoritics, 24, 155-172.

Schultz, L.; Stoffler, D.

1993-07-01

284

Evaluation and Testing of Noble Metals Surrogates.  

National Technical Information Service (NTIS)

This report summarizes the results of testing and evaluation of noble metal surrogates that will support testing of noble metals in melters. The candidate system, potential surrogates, model glass systems, and test conditions have been chosen based on the...

S. K. Sundaram A. R. Cooper J. J. Holbrook B. C. Maclsaac C. H. Trader

2002-01-01

285

Thermal diffusion factors and intermolecular potentials for noble gas-SF sub 6 systems  

SciTech Connect

Experimental thermal diffusion factors for equimolar mixtures of He-, Ne-, Ar-, Kr-, and Xe-SF{sub 6} have been measured in the temperature range from 225 to 500 K. The data were obtained in a 20-tube trennschaukel, or swing separator.'' The systems containing the four lighter noble gases all exhibited a normal'' thermal diffusion factor, {alpha}{sub T}, that is concentration of the heavy species, SF{sub 6}, in the cold region of the apparatus and increase of {alpha}{sub T} with temperature. Xe-SF{sub 6}, the system with the smallest mass difference, exhibited abnormal'' behavior. The spherically symmetric Pack potentials were used to calculate the thermal diffusion factor with reasonable success. Recently published dipole-dipole dispersion coefficients were used to construct intermolecular potentials of the Hartree-Fock-Dispersion functional form with individually damped attractive terms. The potentials, when tested against the available transport and thermodynamic data, improved the fit to experiment in almost all cases. 35 refs., 7 figs., 2 tabs.

Taylor, W.L.; Hurly, J.J. (EG and G Mound Applied Technologies, Miamisburg, OH (USA) Cincinnati Univ., OH (USA). Dept. of Chemistry) [EG and G Mound Applied Technologies, Miamisburg, OH (USA) Cincinnati Univ., OH (USA). Dept. of Chemistry

1990-01-01

286

Capture of negative muons and antiprotons by noble-gas atoms  

NASA Astrophysics Data System (ADS)

Cross sections for capture of negative muons (?^-) and antiprotons (barp) by helium, neon, argon, krypton, and xenon atoms are calculated using the fermion molecular dynamics (FMD) method. Although the quasiclassical method may overestimate correlation, it seems clear that multiple electrons participate in the capture. The He capture cross section decreases abruptly at collision energies exceeding its first ionization potential, rather like capture by the hydrogen atom, but the capture cross sections of the heavier noble gases are smooth at this juncture. The associated relative capture probabilities in mixtures increase with Z due to the higher-Z capture cross sections being larger at a given energy as well as extending to higher collision energies. We have estimated capture ratios in two ways: (i) in the limit that the calculated partial slowing-down cross sections (not including elastic or non-ionizing inelastic) are nearly complete and (ii) in the limit that the true slowing-down cross sections are actually much larger. These two treatments yield significantly different values, with the former seeming to work better for ?^- capture by the light elements and the latter better for ?^- capture by the heavy elements.

Cohen, James S.

2001-10-01

287

Development of a portable membrane contactor sampler for noble gas analyses of surface and groundwater samples  

NASA Astrophysics Data System (ADS)

Noble gas isotopes dissolved in groundwater provide valuable information about climatic conditions during air-water exchange, as well as the residence time of groundwater and its renewal rate. The isotope composition of noble gases can also serve as geochemical fingerprints to decipher the origin of groundwater and its flow system. Conventionally, groundwater is sampled using a copper tube, which is subsequently degassed using a vacuum extraction system for isotope analysis by a mass spectrometer. Although this conventional and well-established way of sampling is widely recognised as being reliable and robust, a major drawback to this method is its size and weight. For example, our sampler consists of a copper tube of 10 mm diameter x 1000 mm length and a metal casing with pinch-off clamps with its total weight to be 2 kg each. A box of 24 samplers well exceeds 40 kg. Considering that sampling fields are not necessarily easily accessible by vehicle, taking hundreds of samples in the field is generally a tough task for everyone. There is a different type of sampler, which is comprised of a much smaller copper tube (6 mm in diameter and 100 mm long for our case) with clamps and a semi-permeable membrane filter. It is sunk into water and left there for dissolved gases to diffuse into the sampler until their concentrations in water become equilibrated with those in the tube. This diffusion sampler is small and easy to handle in the field; it has an advantage over conventional copper tubes, as the diffusion sampler collects gases so that there is no gas extraction process needed before isotope analysis. However, this method requires an equilibration time of 24 hours or more, which could result in lower time-efficiency for sampling work. In order to enable time-efficient and less-painstaking sampling of noble gases dissolved in surface and groundwater, we have developed a portable and self-powered sampling device specified to noble gas analysis by mass spectrometer, following the design of a similar device reported in literatures. The sampling device uses a commercially available membrane contactor which can separate gas phase from continuous from of water. We have examined its extraction performance by preparing several samples for different time spans. We found that our membrane contactor can extract heavier noble gases (Ar, Kr, and Xe) more efficient than lighter noble gases (He and Ne), implying that sorption of gas atoms to the membrane contactor is controlling the transport of noble gases through the membrane. We confirmed that extraction of about 60 min is sufficient for all noble gases reach equilibrium with those dissolved in the water. 3He/4He ratios and other noble gas isotope ratios showed no signs of isotope fractionation, suggesting that the device can be applicable for sampling of dissolved noble gases from the water aiming to the groundwater dating and paleo-climate reconstruction.

Matsumoto, T.; Han, L. H.; Jaklitsh, M.; Aggarwal, P. K.

2012-04-01

288

Noble gas mass spectrometry with a compressor driven recycling system for improved sensitivity  

NASA Astrophysics Data System (ADS)

In noble gas (He, Ne, Ar, Kr and Xe) isotope geo- and cosmochemistry and geochronology, there is an increasing need for better precision and sensitivity of the mass spectrometers. Although the presently available noble gas mass spectrometers detect trace amounts (down to 105 atoms) of noble gas atoms contained in natural samples, isotopic ratios measured at that extremely low level are in many cases not precise enough to resolve specific problems. Also, the instrumental limitation narrows the kinds of rocks suitable for analysis. Thus, in order to expand the analytical capability of noble gases to a wider range of samples with possibly much smaller sizes, it is desirable to have a mass spectrometer with better sensitivity. In order to increase the sensitivity of static-mode noble gas mass spectroscopic analysis, we have developed and tested a gas re-circulation system, which uses a commercially available turbo molecular pump (TMP). During the analysis, the sample gases are directed from the collector end towards the ionization source part of the flight tube. Our preliminary results indicate that the apparent sensitivity of krypton and xenon can be increased by a factor of about 20 and 50, respectively. We also found that the gain factor of helium was somewhat smaller and was approximately 2. Such mass-dependence is quite consistent with the compressibility of TMP which is larger for the heavier molecules.

Matsumoto, T.; Matsuda, J.; Ozima, M.; Yatsevich, I.

2009-12-01

289

Noble gas studies on regolith materials from Apollo 14 and 15.  

NASA Technical Reports Server (NTRS)

Abundances and isotopic compositions of the five stable noble gases, He, Ne, Ar, Kr, and Xe in soils and breccia were determined. The samples investigated included material from a range of depths in a trench and a core tube. Noble gas determinations were performed in a 6-inch all-metal mass spectrometer of high sensitivity. The grain size separates and stepwise heating experimental methods used give results that supplement each other. Calculated concentrations of spallation Xe-126 in many of the fines and gas-rich breccia are presented in a table. Bulk soil samples obtained by Apollo 14 show an inverse correlation of spallation Xe-126 with grain size.

Bogard, D. D.; Nyquist, L. E.

1972-01-01

290

Noble gas composition of the solar wind as collected by the Genesis mission  

NASA Astrophysics Data System (ADS)

We present the elemental and isotopic composition of noble gases in the bulk solar wind collected by the NASA Genesis sample return mission. He, Ne, and Ar were analyzed in diamond-like carbon on a silicon substrate (DOS) and 84,86Kr and 129,132Xe in silicon targets by UV laser ablation noble gas mass spectrometry. Solar wind noble gases are quantitatively retained in DOS and with exception of He also in Si as shown by a stepwise heating experiment on a flown DOS target and analyses on other bulk solar wind collector materials. Solar wind data presented here are absolutely calibrated and the error of the standard gas composition is included in stated uncertainties. The isotopic composition of the light noble gases in the bulk solar wind is as follows: 3He/ 4He: (4.64 0.09) 10 -4, 20Ne/ 22Ne: 13.78 0.03, 21Ne/ 22Ne: 0.0329 0.0001, 36Ar/ 38Ar 5.47 0.01. The elemental composition is: 4He/ 20Ne: 656 5, and 20Ne/ 36Ar 42.1 0.3. Genesis provided the first Kr and Xe data on the contemporary bulk solar wind. The preliminary isotope and elemental composition is: 86Kr/ 84Kr: 0.302 0.003, 129Xe/ 132Xe: 1.05 0.02, 36Ar/ 84Kr 2390 150, and 84Kr/ 132Xe 9.5 1.0. The 3He/ 4He and the 4He/ 20Ne ratios in the Genesis DOS target are the highest solar wind values measured in exposed natural and artificial targets. The isotopic composition of the other noble gases and the Kr/Xe ratio obtained in this work agree with data from lunar samples containing "young" (100 Ma) solar wind, indicating that solar wind composition has not changed within at least the last 100 Ma. Genesis could provide in many cases more precise data on solar wind composition than any previous experiment. Because of the controlled exposure conditions, Genesis data are also less prone to unrecognized systematic errors than, e.g., lunar sample analyses. The solar wind is the most authentic sample of the solar composition of noble gases, however, the derivation of solar noble gas abundances and isotopic composition using solar wind data requires a better understanding of fractionation processes acting upon solar wind formation.

Heber, Veronika S.; Wieler, Rainer; Baur, Heinrich; Olinger, Chad; Friedmann, Tom A.; Burnett, Donald S.

2009-12-01

291

Greenhouse Gases  

MedlinePLUS

... were not for naturally occurring greenhouse gases, the Earth would be too cold to support life as ... the greenhouse effect, the average temperature of the Earth would be about -2F rather than the ...

292

Single-particle kinetic energies of noble-gas solids and liquids: Xenon, krypton, and argon  

SciTech Connect

Direct measurements have been made on the average single-particle kinetic energies, {l angle}{ital E}{sub {ital k}}{r angle}, of a series of solid and liquid specimens of heavy noble gases near melting. To do this, the distributions of energy losses of incident eV neutrons, scattered at angles ranging from 87 to 136 deg, were analyzed on the assumptions that atoms in these specimens have a Gaussian momentum distribution {ital n}({ital p}) and that for these experimental conditions the atoms scatter independently of one another. It is known that the solids, Ar, Kr, and Xe show considerable differences in such characteristics as (a) their respective ratios of triple point to Debye temperatures, (b) the extent of multibody force contributions to cohesion, and (c) phonon anharmonicity. Regardless, it is found for all three solids near their respective triple points that {l angle}{ital E}{sub {ital k}}{r angle} is equal to the equipartition value (3/2){ital kT} well within the various estimated experimental uncertainties of 3% to 7%. Moreover, liquid Kr near its triple point yields the same result, as does liquid Xe at temperature up to 1.8 times its triple point temperature. Because all these systems are expected to be classical at these temperatures, these results demonstrate applicability of this neutron recoil method to determine {l angle}{ital E}{sub {ital k}}{r angle} even of heavy atoms in suitable cases where a value may not be known in advance.

Peek, D.A.; Simmons, R.O. (University of Illinois at Urbana-Champaign, Urbana, IL (USA). Physics Department University of Illinois at Urbana-Champaign, Urbana, IL (USA). Materials Research Laboratory)

1991-02-15

293

Noble Gas Analysis in the Quest to Find "Regolithic" Howardites  

NASA Technical Reports Server (NTRS)

The howardite meteorites consist of approximately 200 polymict breccias of eucrite (basaltic) and diogenite (orthopyroxenitic) material (collectively, the HED group) that originate from the asteroid belt. Infrared reflectance spectroscopy of asteroids and laboratory studies of HEDs have indicated that the asteroid 4-Vesta is the likely parent body, and the partially-demolished south pole may be the source region. Asteroid regolith formation processes may be responsible for a number of observed petrological features including impact melt clasts, reworked clasts and mosaisicm. We have identified such features in a study of 30 howardites and polymict eucrites, and developed a regolith grading scheme based on petrology. However, the true regolithic nature of the howardite suite is not well defined, and previous research has suggested correlations between Ni contents of 300 - 1200 micron / g, a minimal variation in Al2O3 content around 8-9 wt% and the presence of solar wind noble gases are key hallmarks of an ancient regolith on Vesta . Through combined petrological, compositional and noble gas research, we aim to better understand howardite petrological diversity, regolith formation processes on parent asteroids, and to establish what defines a truly "regolithic" howardite. Our research will play an integral part in the interpretation of data gathered by the Dawn mission. Here we report the preliminary results from our noble gas analyses of four howardites: LEW 85313, EET 99408, MET 96500 and PCA 02066. Bulk major element compositional data have been collected, further petrological data for the HED group are reported by our colleagues, whilst trace-element analyses are underway. Our work will investigate the extent of whether previously described Ni, Al2O3 and noble gas characteristics are in fact indicative of a "regolithic" howardite.

Cartwright, Julia A.; Hermann, S.; Herrin, J.; Mittlefehldt, D. W.; Ott, U.

2011-01-01

294

Hole dynamics in noble metals.  

PubMed

Hole dynamics in noble metals (Cu and Au) is investigated by means of first-principles many-body calculations. While holes in a free-electron gas are known to live shorter than electrons with the same excitation energy, our results indicate that d holes in noble metals exhibit longer inelastic lifetimes than excited sp electrons, in agreement with experiment. The density of states available for d-hole decay is larger than that for the decay of excited electrons; however, the small overlap between d and sp states below the Fermi level increases the d-hole lifetime. The impact of d-hole dynamics on electron-hole correlation effects is also addressed. PMID:11019311

Campillo, I; Rubio, A; Pitarke, J M; Goldmann, A; Echenique, P M

2000-10-01

295

Deep plume origin of the Louisville hotspot: Noble gas evidence  

NASA Astrophysics Data System (ADS)

gas compositions have been reported for basaltic core samples from Louisville seamounts recovered during IODP Expedition 330. The in-vacuum crushing techniques were employed to extract noble gases from fresh olivine phenocrysts and submarine glasses with ages between 50 and 74 Ma. Stepwise crushing tests confirmed the extraction of magmatic noble gases from the olivine samples with minimal release of posteruption radiogenic nuclides; however, this was not always the case for the glass samples. The 3He/4He ratios of the studied samples range from a value similar to those of mid-ocean ridge basalts (MORB) to slightly elevated ratios up to 10.6 Ra. These ratios are not as high as those observed in other ocean island basalts, suggesting that the Louisville mantle plume was weak or the samples represent late-stage magmatic activity of the seamounts. However, two Louisville seamount basalts exhibit a primordial Ne isotopic signature that can be clearly discriminated from MORB Ne ratios. The He and Ne isotopic compositions of the Louisville seamount basalts can be explained by the mixing of less degassed mantle and depleted upper mantle with different He/Ne ratios. The presence of the less degassed mantle component in the source of the Louisville seamounts documents a deep origin of their mantle plume.

Hanyu, Takeshi

2014-03-01

296

Molecular Structure and Nonequilibrium Polarizations: Recent Experiments on Polar Gases.  

National Technical Information Service (NTIS)

Senftleben-Beenakker experiments are reported on the thermal conductivity and visosity of polyatomic gases. Polar molecules of linear and symmetric top structure have been investigated in a magnetic field. NH sub 3 -noble gas mixtures and CH sub 3 CN mixt...

B. J. Thijsse

1978-01-01

297

Noble gas isotope measurements for spent nuclear fuel reprocessing. IAEA Task 90/0A211 interim report  

SciTech Connect

The nuclear fission of actinides in reactor fuel produces large quantities of Kr and Xe as fission products. Because of the high levels of fission Kr and Xe, sample collection and analysis of noble gases for spent fuel diagnostic measurements is a simple, straight-forward technique. In modern reprocessing plants with continuous dissolvers, it will not be possible to use traditional methods for isolating input batches of fuel. This study investigates the feasibility of using noble gas isotope abundance measurements (isotope correlation techniques - ICT) to solve safeguards requirements. Noble gas measurements might be able to provide an independent analysis of Pu contained within dissolves fuel, on an individual fuel assembly basis. The isotopic composition of Kr and Xe in spent fuel reflects both the composition (isotope abundance ratios) of the fission products and the effects of neutron capture on those fission products. We have reviewed the available literature for noble gas analyses of spent reactor fuel. While references are made to noble gas isotope correlations over the last 20 years, we have found little if any detailed analysis of large data sets. The literature search did find several useful reports. Of these papers, one is particularly useful for evaluating noble gas isotopic compositions. The ``Benchmark-paper`` (1) contains 54 Kr and 56 Xe isotopic composition analyses for 4 different reactors with a variety of fuel enrichment factors. Burnup ranges from 8000 to 37000 MWd/tU. Besides the noble gas measurements, a variety of other measurements are reported (actinides and fission products).

Hudson, G.B.

1993-02-17

298

Development of hyperpolarized noble gas MRI  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging using the MR signal from hyperpolarized noble gases 129Xe and 3He may become an important new diagnostic technique. Alex Pines (adapting the hyperpolarization technique pioneered by William Happer) presented MR spectroscopy studies using hyperpolarized 129Xe. The current authors recognized that the enormous enhancement in the detectability of 129Xe, promised by hyperpolarization, would solve the daunting SNR problems impeding their attempts to use 129Xe as an in vivo MR probe, especially in order to study the action of general anesthetics. It was hoped that hyperpolarized 129Xe MRI would yield resolutions equivalent to that achievable with conventional 1H 2O MRI, and that xenon's solubility in lipids would facilitate investigations of lipid-rich tissues that had as yet been hard to image. The publication of hyperpolarized 129Xe images of excised mouse lungs heralded the emergence of hyperpolarized noble-gas MRI. Using hyperpolarized 3He, researchers have obtained images of the lung gas space of guinea pigs and of humans. Lung gas images from patients with pulmonary disease have recently been reported. 3He is easier to hyperpolarize than 129Xe, and it yields a stronger MR signal, but its extremely low solubility in blood precludes its use for the imaging of tissue. Xenon, however, readily dissolves in blood, and the T1 of dissolved 129Xe is long enough for sufficient polarization to be carried by the circulation to distal tissues. Hyperpolarized 129Xe dissolved-phase tissue spectra from the thorax and head of rodents and humans have been obtained, as have chemical shift 129Xe images from the head of rats. Lung gas 129Xe images of rodents, and more recently of humans, have been reported. Hyperpolarized 129Xe MRI (HypX-MRI) may elucidate the link between the structure of the lung and its function. The technique may also be useful in identifying ventilation-perfusion mismatch in patients with pulmonary embolism, in staging and tracking the success of therapeutic approaches in patients with chronic obstructive airway diseases, and in identifying candidates for lung transplantation or reduction surgery. The high lipophilicity of xenon may allow MR investigations of the integrity and function of excitable lipid membranes. Eventually, HypX-MRI may permit better imaging of the lipid-rich structures of the brain. Cortical brain function is one perfusion-dependent phenomena that may be explored with hyperpolarized 129Xe MR. This leads to the exciting possibility of conducting hyperpolarized 129Xe functional MRI (HypX-fMRI) studies.

Albert, M. S.; Balamore, D.

1998-02-01

299

Atmospheric gases  

NSDL National Science Digital Library

Which gases make up the atmosphere? This activity page, part of an interactive laboratory series for grades 8-12, introduces students to the gaseous components of the atmosphere. Students explore the main gases of the atmosphere using a pop-up pie chart. Descriptions of the gases and their percentages in the atmosphere are provided. Students read about water vapor in the atmosphere, and an animation shows a simplified process of precipitation. A pop-up window explains the effects of dust on the atmosphere, and a photograph shows how large amounts of dust in the atmosphere create the reds and oranges displayed in sunsets. Finally, ozone is introduced to students as a necessary component of human life on Earth. Copyright 2005 Eisenhower National Clearinghouse

University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

2003-01-01

300

21 CFR 872.3060 - Noble metal alloy.  

... Noble metal alloy. (a) Identification. A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver, that is intended for use in the fabrication of cast or porcelain-fused-to-metal...

2014-04-01

301

Efficient conversion of ^3He(n,tp) and ^10B(n,alpha^7Li) reaction energies into far-ultraviolet radiation by noble gas excimers  

Microsoft Academic Search

Previous work^1,2 showed that the ^3He(n,tp) reaction in a cell of ^3He at atmospheric pressure generated tens of far-ultraviolet (FUV) photons per reacted neutron. Here we report amplification of that signal by factors of 1000 when noble gases are added to the cell. Calibrated filter-detector measurements show that this large signal is due to noble-gas excimer emissions, and that the

Patrick P. Hughes; Michael A. Coplan; Alan K. Thompson; Robert E. Vest; Charles W. Clark

2011-01-01

302

A mass spectrometric line for tritium analysis of water and noble gas measurements from different water amounts in the range of microlitres and millilitres.  

PubMed

This paper describes the procedure followed for noble gas measurements for litres, millilitres and microlitres of water samples in our laboratory, including sample preparation, mass spectrometric measurement procedure, and the complete calibrations. The preparation line extracts dissolved gases from water samples of volumes of 0.2 ? l to 3 l and it separates them as noble and other chemically active gases. Our compact system handles the following measurements: (i) determination of tritium concentration of environmental water samples by the (3)He ingrowth method; (ii) noble gas measurements from surface water and groundwater; and (iii) noble gas measurements from fluid inclusions of solid geological archives (e.g. speleothems). As a result, the tritium measurements have a detection limit of 0.012 TU, and the expectation value (between 1 and 20 TU) is within 0.2 % of the real concentrations with a standard deviation of 2.4 %. The reproducibility of noble gas measurements for water samples of 20-40 ml allows us to determine solubility temperatures by an uncertainty better than 0.5 C. Moreover, noble gas measurements for tiny water amounts (in the microlitre range) show that the results of the performed calibration measurements for most noble gas isotopes occur with a deviation of less than 2 %. Theoretically, these precisions for noble gas concentrations obtained from measurements of waters samples of a few microlitres allow us to determine noble gas temperatures by an uncertainty of less than 1 C. Here, we present the first noble gas measurements of tiny amounts of artificial water samples prepared under laboratory conditions. PMID:22537518

Papp, Laszlo; Palcsu, Laszlo; Major, Zoltan; Rinyu, Laszlo; Tth, Istvan

2012-01-01

303

Investigation of the noble gas solubility in H 2O-CO 2 bearing silicate liquids at moderate pressure II: the extended ionic porosity (EIP) model  

NASA Astrophysics Data System (ADS)

A semi-theoretical model is proposed to predict partitioning of noble gases between any silicate liquid and a H 2O-CO 2 gas phase with noble gas as a minor component, in a large range of pressures (at least up to 300 MPa). The model is based on the relationship between the concentration of dissolved noble gas and ionic porosity of the melt, found by Carroll and Stolper [Geochim. Cosmochim. Acta 57 (1993) 5039-5051] for H 2O-CO 2 free melts. It evaluates the effect of dissolved H 2O and CO 2 on the melt ionic porosity and, consequently on Henry's constants of noble gases. The fugacities of the noble gases in the H 2O-CO 2-noble gas mixtures are also considered in our equilibrium calculations of dissolved gas by using a modified Redlich-Kwong equation of state for the H 2O-CO 2-noble gas system. The formulated model (referred to as the extended ionic porosity model) clearly predicts a positive dependence of noble gas solubility on dissolved H 2O in melt, which becomes negligible when water concentration is higher than 3 wt%. Oppositely, noble gas solubility decreases as a consequence of increasing CO 2 in both basaltic and rhyolitic melts. The increase of noble gas solubility as a consequence of H 2O addition to the melt grows exponentially with the increase of the noble gas atomic size. As a result, although xenon solubility is much lower than the helium solubility in anhydrous melts, they become almost comparable at several percent of dissolved H 2O in the melt. On this basis, an exponential augmentation of the number of large free spaces in silicate liquid can be inferred in relation to increasing dissolved H 2O. Comparison between our predicted values and available experimental data [A. Paonita et al., Earth Planet. Sci. Lett. 181 (2000) 595-604] shows good agreement. At present, the EIP model is the unique tool which predicts how the main volatiles in magmatic systems affect the noble gas solubility in silicate melts, therefore it should be taken into account for future studies of noble gas fractionation in degassing natural magmas.

Nuccio, P. M.; Paonita, A.

2000-12-01

304

Noble gas anomalies related to high-intensity methane gas seeps in the Black Sea  

Microsoft Academic Search

Dissolved noble gases and tritium were analyzed at a series of high-intensity methane gas seeps in the Black Sea to study the transport and gas exchange induced by bubble-streams in the water column. These processes affect marine methane emissions to the atmosphere and are therefore relevant to climate warming. The seep areas investigated are located in the Dnepr paleo-delta, west

C. P. Holzner; D. F. McGinnis; C. J. Schubert; R. Kipfer; D. M. Imboden

2008-01-01

305

Measurement of Noble Gas Solubility in Seawater Using a Quadrupole Mass Spectrometer  

Microsoft Academic Search

A quadrupole-based mass spectrometric system for determining noble gas (He, Ne, Ar, Kr and Xe) abundances in a liquid sample has been developed and applied to seawater equilibrated with the atmosphere at several temperatures. After known amounts of isotopic spikes (22Ne, 36Ar, 86Kr and 124Xe) were introduced into the preparation vacuum line, dissolved gases were extracted from seawater and well

Yuji Sano; Naoto Takahata

2005-01-01

306

A quadrupole-based mass spectrometric system for the determination of noble gas abundances in fluids  

Microsoft Academic Search

We present details of the operation and performance of a quadrupole mass spectrometer-based system developed for the extraction, separation, and high-precision measurement of noble gases dissolved in fluid samples. The relatively inexpensive quadrupole mass spectrometer system, employed with the isotope dilution technique, achieves a precision for He, Ne, Ar, Kr, and Xe abundances of 0.4%, 0.7%, 0.1%, 0.8%, and 0.9%

Justin T. Kulongoski; David R. Hilton

2002-01-01

307

A quadrupole-based mass spectrometric system for the determination of noble gas abundances in fluids  

Microsoft Academic Search

We present details of the operation and performance of a quadrupole mass spectrometer-based system developed for the extraction, separation, and high-precision measurement of noble gases dissolved in fluid samples. The relatively inexpensive quadrupole mass spectrometer system, employed with the isotope dilution technique, achieves a precision for He, Ne, Ar, Kr, and Xe abundances of +\\/-0.4%, +\\/-0.7%, +\\/-0.1%, +\\/-0.8%, and +\\/-0.9%

Justin T. Kulongoski; David R. Hilton

2002-01-01

308

Early evolution of Martian volatiles: Nitrogen and noble gas components in ALH84001 and Chassigny  

Microsoft Academic Search

Studies on SNC meteorites have permitted the characterization of modern Martian atmospheric components as well as indigenous Martian nitrogen and solar-type xenon. New isotopic and elemental abundances of noble gases and nitrogen in ALH84001 and Chassigny provide important constraints on the early evolution of the planet. A primitive solar Xe component (Chass-S) and an evolved Xe component (Chass-E), augmented with

K. J. Mathew; K. Marti

2001-01-01

309

Cryogenic method for measuring nuclides and fission gases  

DOEpatents

A cryogenic method is provided for determining airborne gases and particulates from which gamma rays are emitted. A special dewar counting vessel is filled with the contents of the sampling flask which is immersed in liquid nitrogen. A vertically placed sodium-iodide or germanium-lithium gamma-ray detector is used. The device and method are of particular use in measuring and identifying the radioactive noble gases including emissions from coal-fired power plants, as well as fission gases released or escaping from nuclear power plants.

Perdue, P.T.; Haywood, F.F.

1980-05-02

310

The atmospheric inventory of Xenon and noble cases in shales The plastic bag experiment  

NASA Technical Reports Server (NTRS)

A novel trapped gas analysis protocol is applied to five shales in which the samples are sealed in air to eliminate the possibility of gas loss in the preanalysis laboratory vacuum exposure of a conventional protocol. The test is aimed at a determination concerning the hypothesis that atmospheric noble gases occur in the same proportion as planetary gases in meteorites, and that the factor-of-23 deficiency of air Xe relative to planetary Xe is made up by Xe stored in shales or other sedimentary rocks. The results obtained do not support the shale hypothesis.

Bernatowicz, T. J.; Podosek, F. A.; Honda, M.; Kramer, F. E.

1984-01-01

311

Greenhouse Gases  

NSDL National Science Digital Library

This is a lesson where learners engage in a radiating heat activity and an activity that measures temperature in models with and without greenhouse gases. Learners will draw conclusions about the effect of greenhouse gases on temperature and on human life and kinesthetically model the absorbing and re-radiation of heat. The lesson models scientific inquiry using the 5E instructional model and includes teacher notes, prerequisite concepts, common misconceptions, student journal and reading. This is lesson 3 in the Astro-Venture Atmospheric Science Training Unit. The purpose of the unit is to increase students awareness of and interest in astrobiology and the many career opportunities that utilize science, math and technology skills. The lessons are designed for educators to use in conjunction with the Astro-Venture multimedia modules.

312

Multicollector High Precision Resolution of Primordial Kr and Xe in Mantle CO2 Well Gases  

NASA Astrophysics Data System (ADS)

Noble gas isotopes in magmatic CO2 well gases provide a unique insight into mantle volatile origin and dynamics [1-3]. Previous work has resolved mantle 20Ne/22Ne ratios consistent with a solar wind irradiated meteoritic source for mantle He and Ne [1]. This is distinct from Solar Wind values that might be expected if the primary mechanism of terrestrial mantle volatile acquisition was through the gravitational capture of solar nebula gases [see 4]. Within the CO2 well gases a primordial component has also been resolved in the non- radiogenic Xe isotopic composition [2,3]. Using multicollector mass spectrometry we have observed a 124Xe/130Xe excess of 1.85 percent over air plus/minus 0.17 percent for the least air contaminated samples. At this level of precision we are for the first time able to differentiate between a trapped meteoritic origin (average carbonaceous chondrite or Q Xe) rather than Solar Wind origin as the primordial Xe component. The well gases also contain Kr which, in the least air contaminated sample, have a correlated 86Kr/82Kr excess of 0.55 percent over air plus/minus 0.04 percent. Whilst mass dependent fractionation can theoretically produce correlated excesses in 124Xe-128Xe and 82Kr-86Kr isotopes, no fractionation from air is observed in 38Ar/36Ar [3] and the Kr excesses are in the opposite sense to that of Xe. From 136Xe excesses, Kr fission yield from Pu and U can be calculated and subtracted from the Kr isotopic signature. This fission-corrected signature is most reasonably explained as a primordial component. This is the first time that primordial Kr has ever been resolved in a terrestrial sample. The primordial Kr isotopic signature is distinct from Solar Wind Kr and is consistent with the primordial Kr also originating as a trapped component within meteorites. We are now able to demonstrate that both the light (He and Ne) and Heavy (Kr and Xe) noble gas origin in the terrestrial mantle is consistent with a trapped component during the accretionary process and can discount gravitational capture as the principle mechanism of interior planetary volatile acquisition. References: [1] Ballentine, C.J. et al., Nature, 433. 33-38, (2005) [2] Caffee, M.W. et al., Science, 285, 2115- 2118, (1999) [3] Holland G. and Ballentine C. J., Nature, 441, 186-191 (2006) [4] Pepin R.O. and Porcelli D. Rev. Min. Geochem. 47, 191-246 (2002)

Holland, G.; Ballentine, C.; Cassidy, M.

2008-12-01

313

Quantum Number Dependence of Lineshift Coefficients Induced by Collisions with Noble Gas Perturbers in the nu(3) Band of NO(2).  

PubMed

To complete our study concerning lineshift in the rovibrational spectrum of (14)N(16)O(2), a pulse-driven three-channel lead salt diode laser spectrometer was applied to record high-resolution spectra at room temperature in the 6.2-m region corresponding to the nu(3) band at low NO(2) concentrations. The shift was studied for collisions with the noble gases He, Ne, Ar, Kr, and Xe. This paper extends our recently published data in order to analyze the quantum number dependence of the shift effect more precisely. Therefore, in this paper, additionally eight unresolved NO(2) doublets covering an enlarged quantum number range (10 noble gas) and additionally broadening coefficients gamma(NO(2)-noble gas) were determined. Hereby, the experimental data confirm general trends published recently. In this study, in the case of broadening for the lighter rare gases helium, neon, and argon, only a slight decrease of gamma(NO(2)-noble gas) was observed, whereas for the rare gases with a higher atomic weight, i.e., krypton and xenon, a pronounced decrease of gamma(NO(2)-noble gas) with increasing rotational quantum number N(") occurred. All measured lineshift coefficients were negative. The absolute value of the determined lineshift coefficient ||delta(NO(2)-noble gas) || increases with the mass of the noble gas perturber, i.e., ||delta(NO(2)-He) || < ||delta(NO(2)-Ne) || < ||delta(NO(2)-Ar) || < ||delta(NO(2)-Kr) || < ||delta(NO(2)-Xe) ||. Within the studied quantum number range, an increase ||delta(NO(2)-noble gas) || with increase of N(") was observed. A typical trend of the shift and broadening data on the quantum number K(")(a) was not observed. Copyright 2000 Academic Press. PMID:10637106

Sumpf; Bouazza; Kissel; Kronfeldt

2000-02-01

314

Incorporation of noble metals into aerogels  

DOEpatents

Aerogels or xerogels containing atomically dispersed noble metals for applications such environmental remediation. New noble metal precursors, such as Pt--Si or Pd(Si--P).sub.2, have been created to bridge the incompatibility between noble metals and oxygen, followed by their incorporation into the aerogel or xerogel through sol-gel chemistry and processing. Applications include oxidation of hydrocarbons and reduction of nitrogen oxide species, complete oxidation of volatile organic carbon species, oxidative membranes for photocatalysis and partial oxidation for synthetic applications.

Hair, Lucy M. (Livermore, CA); Sanner, Robert D. (Livermore, CA); Coronado, Paul R. (Livermore, CA)

1998-01-01

315

Incorporation of noble metals into aerogels  

DOEpatents

Aerogels or xerogels containing atomically dispersed noble metals for applications such as environmental remediation are disclosed. New noble metal precursors, such as Pt--Si or Pd(Si--P){sub 2}, have been created to bridge the incompatibility between noble metals and oxygen, followed by their incorporation into the aerogel or xerogel through sol-gel chemistry and processing. Applications include oxidation of hydrocarbons and reduction of nitrogen oxide species, complete oxidation of volatile organic carbon species, oxidative membranes for photocatalysis and partial oxidation for synthetic applications.

Hair, L.M.; Sanner, R.D.; Coronado, P.R.

1998-12-22

316

Physiological response of rats to delivery of helium and xenon: implications for hyperpolarized noble gas imaging  

NASA Technical Reports Server (NTRS)

The physiological effects of various hyperpolarized helium and xenon MRI-compatible breathing protocols were investigated in 17 Sprague-Dawley rats, by continuous monitoring of blood oxygen saturation, heart rate, EKG, temperature and endotracheal pressure. The protocols included alternating breaths of pure noble gas and oxygen, continuous breaths of pure noble gas, breath-holds of pure noble gas for varying durations, and helium breath-holds preceded by two helium rinses. Alternate-breath protocols up to 128 breaths caused a decrease in oxygen saturation level of less than 5% for either helium or xenon, whereas 16 continuous-breaths caused a 31.5% +/- 2.3% decrease in oxygen saturation for helium and a 30.7% +/- 1. 3% decrease for xenon. Breath-hold protocols up to 25 s did not cause the oxygen saturation to fall below 90% for either of the noble gases. Oxygen saturation values below 90% are considered pathological. At 30 s of breath-hold, the blood oxygen saturation dropped precipitously to 82% +/- 0.6% for helium, and to 76.5% +/- 7. 4% for xenon. Breath-holds longer than 10 s preceded by pre-rinses caused oxygen saturation to drop below 90%. These findings demonstrate the need for standardized noble gas inhalation procedures that have been carefully tested, and for continuous physiological monitoring to ensure the safety of the subject. We find short breath-hold and alternate-breath protocols to be safe procedures for use in hyperpolarized noble gas MRI experiments. Copyright 2000 John Wiley & Sons, Ltd.

Ramirez, M. P.; Sigaloff, K. C.; Kubatina, L. V.; Donahue, M. A.; Venkatesh, A. K.; Albert, M. S.; ALbert, M. S. (Principal Investigator)

2000-01-01

317

Chronology and shock history of the Bencubbin meteorite: A nitrogen, noble gas, and Ar-Ar investigation of silicates, metal and fluid inclusions  

NASA Astrophysics Data System (ADS)

We have investigated the distribution and isotopic composition of nitrogen and noble gases, and the Ar-Ar chronology of the Bencubbin meteorite. Gases were extracted from different lithologies by both stepwise heating and vacuum crushing. Significant amounts of gases were found to be trapped within vesicles present in silicate clasts. Results indicate a global redistribution of volatile elements during a shock event caused by an impactor that collided with a planetary regolith. A transient atmosphere was created that interacted with partially or totally melted silicates and metal clasts. This atmosphere contained 15N-rich nitrogen with a pressure ?3 10 5 hPa, noble gases, and probably, although not analyzed here, other volatile species. Nitrogen and noble gases were re-distributed among bubbles, metal, and partly or totally melted silicates, according to their partition coefficients among these different phases. The occurrence of N 2 trapped in vesicles and dissolved in silicates indicates that the oxygen fugacity ( fO2) was greater than the iron-wstite buffer during the shock event. Ar-Ar dating of Bencubbin glass gives an age of 4.20 0.05 Ga, which probably dates this impact event. The cosmic-ray exposure age is estimated at 40 Ma with two different methods. Noble gases present isotopic signatures similar to those of "phase Q" (the major host of noble gases trapped in chondrites) but elemental patterns enriched in light noble gases (He, Ne and Ar) relative to Kr and Xe, normalized to the phase Q composition. Nitrogen isotopic data together with 40Ar/ 36Ar ratios indicate mixing between a 15N-rich component (? 15N = +1000), terrestrial N, and an isotopically normal, chondritic N. Bencubbin and related 15N-rich meteorites of the CR clan do not show stable isotope (H and C) anomalies, precluding contribution of a nucleosynthetic component as the source of 15N enrichments. This leaves two possibilities, trapping of an ancient, highly fractionated atmosphere, or degassing of a primitive, isotopically unequilibrated, nitrogen component. Although the first possibility cannot be excluded, we favor the contribution of primitive material in the light of the recent finding of extremely 15N-rich anhydrous clasts in the CB/CH Isheyevo meteorite. This unequilibrated material, probably carried by the impactor, could have been insoluble organic matter extremely rich in 15N and hosting isotopically Q-like noble gases, possibly from the outer solar system.

Marty, Bernard; Kelley, Simon; Turner, Grenville

2010-11-01

318

Multiple ion Counting for Noble gas Mass Spectrometry  

NASA Astrophysics Data System (ADS)

In geo- and cosmochemistry noble gases are analyzed for their abundance and isotopic composition by mass spectrometry in the static mode (no pumping). This results in that they are among the elements with the highest detection efficiency. This is especially so for xenon, where during the course of a normal measurement almost all atoms will have been ionized. Not all of them will have been detected, however, even for 100 percent transmission of the mass spectrometer, if individual isotopes are measured by stepped change of the magnetic field setting. On the other hand, except for special cases, noble gas isotopes other than radiogenic 4He and 40Ar usually have abundances too low for useful detection by multicollection using Faraday cups. Multiple ion counting, i.e. parallel detection of all isotopes of a given noble gas element by ion counting, is the obvious choice to improve this situation and gain (in case of Xe with its 9 isotopes) up to an order of magnitude in sensitivity. We have exchanged the standard detection system of our Nu instruments Noblesse noble gas mass spectrometer with a multi-ion counting unit from Nu instruments, the second they have assembled (the other is at Washington University, St. Louis). The detector contains seven channeltrons and (at the high mass side) a Faraday collector. Xenon can be measured by multiple ion counting in two magnetic field steps, one for the seven even-numbered isotopes (masses 124-136) and a second for the high abundant odd- numbered isotopes 129,131Xe, for which we use a shorter counting time. Static measurement of xenon easily leads to memory effects from previously analyzed samples, depending on the history. Hence, often the real improvement is in the gain in speed by which useful data can be obtained, rather than the actual yield, since extrapolating to "time zero" (gas-inlet into the mass spectrometer) can be performed more reliably. "Real" samples will therefore often be measured for a shorter time than required to detect the maximum number of ions. I will report on first experiences with standard samples. Actual samples planned to be analyzed include presolar grains from meteorites, micrometeorites, and interplanetary dust particles.

Ott, U.

2008-12-01

319

Noble liquid detectors for dark matter  

Microsoft Academic Search

Experiments based on noble liquid targets are now providing competitive sensitivities in the race for the direct detection of particle dark matter. Theoretical estimates, based on supersymmetric models predict dark matter interaction rates from the best sensitivity of existing direct detection experiments of 1 evts\\/kg\\/month, down to rates of 1 evts\\/100 kg\\/yr, and below this. Current noble liquid experiments for

Richard Gaitskell

2007-01-01

320

A model to explain the various paradoxes associated with mantle noble gas geochemistry  

PubMed Central

As a result of an energetic accretion, the Earth is a volatile-poor and strongly differentiated planet. The volatile elements can be accounted for by a late veneer (?1% of total mass of the Earth). The incompatible elements are strongly concentrated into the exosphere (atmosphere, oceans, sediments, and crust) and upper mantle. Recent geochemical models invoke a large primordial undegassed reservoir with chondritic abundances of uranium and helium, which is clearly at odds with mass and energy balance calculations. The basic assumption behind these models is that excess primordial 3He is responsible for 3He/4He ratios higher than the average for midocean ridge basalts. The evidence however favors depletion of 3He and excessive depletion of 4He and, therefore, favors a refractory, residual (low U, Th) source Petrological processes such as melt-crystal and melt-gas separation fractionate helium from U and Th and, with time, generate inhomogeneities in the 3He/4He ratio. A self-consistent model for noble gases involves a gas-poor planet with trapping of CO2 and noble gases in the shallow mantle. Such trapped gases are released by later tectonic and magmatic processes. Most of the mantle was depleted and degassed during the accretion process. High 3He/4He gases are viewed as products of ancient gas exsolution stored in low U environments, rather than products of primordial reservoirs.

Anderson, Don L.

1998-01-01

321

Redistribution of implanted noble gas atoms by self-interstitials in molybdenum and nickel  

Microsoft Academic Search

Thermal Desorption Spectrometry (TDS) has been used to study the interactions of Self-Interstitial Atoms (SIA) with noble gas associated defects in Mo and Ni. Low energy heavy ion bombardment (100 eV Ar and Xe for Mo; 50 eV Kr for Ni) has been used to introduce SIA into the metals. Interactions have been observed of SIA with He n V

A. van Veen; W. Th. M. Buters; T. R. Armstrong; B. Nielsen; K. T. Westerduin; L. M. Caspers; J. Th. M. De Hosson

1983-01-01

322

ABOUT THE POSSIBLE ROLE OF HYDROCARBON LAKES IN THE ORIGIN OF TITAN'S NOBLE GAS ATMOSPHERIC DEPLETION  

SciTech Connect

An unexpected feature of Titan's atmosphere is the strong depletion in primordial noble gases revealed by the Gas Chromatograph Mass Spectrometer aboard the Huygens probe during its descent on 2005 January 14. Although several plausible explanations have already been formulated, no definitive response to this issue has yet been found. Here, we investigate the possible sequestration of these noble gases in the liquid contained in lakes and wet terrains on Titan and the consequences for their atmospheric abundances. Considering the atmosphere and the liquid existing on the soil as a whole system, we compute the abundance of each noble gas relative to nitrogen. To do so, we make the assumption of thermodynamic equilibrium between the liquid and the atmosphere, the abundances of the different constituents being determined via regular solution theory. We find that xenon's atmospheric depletion can be explained by its dissolution at ambient temperature in the liquid presumably present on Titan's soil. In the cases of argon and krypton, we find that the fractions incorporated in the liquid are negligible, implying that an alternative mechanism must be invoked to explain their atmospheric depletion.

Cordier, D. [Ecole Nationale Superieure de Chimie de Rennes, CNRS, UMR 6226, Avenue du General Leclerc, CS 50837, 35708 Rennes Cedex 7 (France); Mousis, O. [Universite de Franche-Comte, Institut UTINAM, CNRS/INSU, UMR 6213, 25030 Besancon Cedex (France); Lunine, J. I. [Dipartimento di Fisica, Universita degli Studi di Roma 'Tor Vergata', Rome (Italy); Lebonnois, S. [Laboratoire de Meteorologie Dynamique, Jussieu, P.O. Box 99, 75252 PARIS cedex 05 (France); Lavvas, P. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ (United States); Lobo, L. Q.; Ferreira, A. G. M., E-mail: daniel.cordier@ensc-rennes.f [Departamento de Engenharia Quimica, Universidade de Coimbra, Coimbra 3030-290 (Portugal)

2010-10-01

323

Simulations of physical adsorption of gases in IRMOFs  

NASA Astrophysics Data System (ADS)

We performed grand canonical Monte Carlo simulations to study the adsorption of noble gases, H2 and CO2 in IRMOF-1. The IRMOF is modeled as a simple structure where a cubic lattice is composed of adsorption centers that reproduce the strength of the metallic corners and organic linkers in the real structure. From the adsorption isotherms obtained in our simulations we calculated the isosteric heat of adsorption and compare with available experimental results. Research supported by NSF and ACS, PRF.

Harriott, Osaro; Gatica, Silvina

2012-02-01

324

Noble gas contents of shergottites and implications for the Martian origin of SNC meteorites  

NASA Technical Reports Server (NTRS)

Three meteorites belonging to the rare group of SNC achondrites, which may have originated in the planet Mars, have been subjected to noble gas isotopic concentration measurements. The elemental and isotopic ratios obtained are unlike those for any other noble gas components except those obtained in analyses of the Martian atmosphere by Viking spacecraft. It is hypothesized that the Kr and Xe gases represent a portion of the Martian atmosphere which was shock-implanted in the case of Elephant Moraine A79001, and that they constitute direct evidence of a Martian origin for the shergottite meteorites. If the SNC meteorites were ejected from Mars at the shergottite shock age of about 180 My ago, they must have been objects more than 6 m in diameter which experienced at least three space collisions to initiate cosmic ray exposure.

Bogard, D. D.; Nyquist, L. E.; Johnson, P.

1984-01-01

325

Influence of noble gas ion polishing species on extreme ultraviolet mirrors  

NASA Astrophysics Data System (ADS)

Low energy ion polishing is attractive in thin films because of the small interaction zone with the treated material. In this context, various noble gases (Ne, Ar, Kr, and Xe) have been applied for low energy ion polishing of interfaces in nanoscale optical Mo/Si multilayers in order to mitigate the evolving roughness during the deposition process. The interface morphology has been studied by grazing incidence small angle x-ray scattering, the multilayer composition by x-ray photoelectron spectroscopy, and the general performance by extreme ultraviolet (EUV) reflectometry. Both the average roughness level and the vertical correlation length of the roughness can be reduced significantly by increasing the atomic mass of the ion species applied for polishing. Maximum EUV reflectance is observed for Kr+-polishing, while Xe+-polishing shows a superior structure. This apparent contradiction is explained by taking into account the optical absorption from noble gas residuals in the amorphous silicon layers.

van den Boogaard, A. J. R.; Zoethout, E.; Makhotkin, I. A.; Louis, E.; Bijkerk, F.

2012-12-01

326

Far-ultraviolet signatures of the 3He(n,tp) reaction in noble gas mixtures  

NASA Astrophysics Data System (ADS)

Previous work showed that the 3He(n,tp) reaction in a cell of 3He at atmospheric pressure generated tens of far-ultraviolet photons per reacted neutron. Here we report amplification of that signal by factors of 1000 and more when noble gases are added to the cell. Calibrated filter-detector measurements show that this large signal is due to noble gas excimer emissions and that the nuclear reaction energy is converted to far-ultraviolet radiation with efficiencies of up to 30%. The results have been placed on an absolute scale through calibrations at the NIST SURF III synchrotron. They suggest possibilities for high-efficiency neutron detectors as an alternative to existing proportional counters.

Hughes, Patrick P.; Coplan, Michael A.; Thompson, Alan K.; Vest, Robert E.; Clark, Charles W.

2010-12-01

327

Noble Gas Studies on Martian Meteorites: Dar Al Gani 476/489, Sayh Al Uhaymir 005/060, Dhofar 019, Los Angeles 001 and Zagami  

NASA Astrophysics Data System (ADS)

We report the concentrations and isotopic ratios of noble gases of DaG 489, SaU 005/060, DHO 019, LA 001 and Zagami. Based on 81Kr-Kr apparent ages, the long terrestrial ages of DaG 476 and DHO 019 are also calculated. The concentrations of 80Kr produced by neutron capture from Br were calculated.

Park, J.; Okazaki, R.; Nagao, K.

2003-03-01

328

Noble gas measurements from tiny water amounts: fluid inclusions in carbonates of speleothemes and coral skeletons  

NASA Astrophysics Data System (ADS)

Based on the concentrations of dissolved noble gases in fluid inclusions in speleothems and corals, noble gas temperatures (NGT) might be derived, that would be important climate information [1]. In the case of terrestrial carbonates, it means that the temperature dependency of noble gases in the evolving fluid inclusions is suitable to determine the prevailing temperature. This recognition provides new opportunities for the research of paleoclimate. Additionally, the dissolved noble gases in the fluid inclusions represented in corals could be used to study past sea surface temperatures that are one of the most essential parameter of climate reconstructions. To measure dissolved noble gases in fluid inclusions of a few micro-litres, a noble gas mass spectrometer equipped with an ultra high vacuum preparation line is the most suitable way. The preparation of the carbonate samples is performed in a sample preparation system connected to a static mode VG 5400 noble gas mass spectrometer. As a first step of the sample preparation, one piece of a sample is put into a crusher of the preparation line and then evacuated and heated at night. The crushing of dripstone and coral samples is carried out in a stainless steel pipe with a ferro-magnetic ball at 150 C temperature, in such a way that the ball is kept on elevating and falling down onto the carbonate sample one hundred times. The aim of the heating is to avoid the water released from the fluid inclusions not to be adsorbed on the surface of the freshly broken carbonate [2]. The water released from the fluid inclusions is frozen into a cold finger, being held at temperature of -70 C for 15 minutes. In this case, the collection efficiency is better than 99.7 %. Then the cold finger is warmed to 27 C, and the pressure of the water vapour expanded to the volume of the cold finger is determined by a pressure gauge, which accuracy is better than 0.2 % in the pressure range of 10-2 mbar to 11 mbar. The water vapour pressure range has been calibrated by measuring ten well known water aliquots between 0.45 mg and 3.14 mg sealed in glass capillaries. With this method, the quantity of the water can be determined better than 1% uncertainty. After the dissolved noble gases has been released from the fluid inclusions, they are collected and separated from each other by a cryo system which consists of a stainless steel empty trap and a trap filled with charcoal. The argon, krypton, xenon fraction and the other chemically active gases (N2, O2, CO2, etc.) are trapped in the stainless steel trap at 25 K, while the isotopes of helium and neon in the charcoal trap held at 10 K. So far, the abundance of helium is not measured, because helium does not play a role in the NGT determination due to radiogenic helium component. The helium is pumped away. The neon is released from the stainless steel trap at temperature of 90 K and admitted to the noble gas mass spectrometer. The ion source is tuned for the best sensitivity for neon. The neon isotopes are detected by an electron multiplier in ion counting mode. The argon, krypton and xenon isotopes are measured simultaneously. The gases are released from the stainless steel trap at 150 K, and introduced into a getter trap in order to be purified from the other non-inert gases. Then the pure argon, krypton, xenon fraction is admitted to the mass spectrometer. The isotopes of argon are detected by a Faraday cup, while krypton and xenon isotopes are detected by an electron multiplier. After every single mass spectrometric measurement fast calibration are executed. The calibration of the mass spectrometric measurement is performed by means of well known air aliquots taken from an air reservoir in which the pressure is 2.0052 Pa. The results of the calibration measurements show that the reproducibility is about 2% for all noble gas isotopes measured. This error in noble gas concentrations results in an uncertainty of about 1 C or lower in the determination of NGT, if the amount of the excess air is smaller than 10 V/V %. To check the overall precis

Papp, Laszlo; Palcsu, Laszlo; Major, Zoltan

2010-05-01

329

Noble Gas Analysis for Mars Robotic Missions: Evaluating K-Ar Age Dating for Mars Rock Analogs and Martian Shergottites  

NASA Technical Reports Server (NTRS)

The purpose of this noble gas investigation was to evaluate the possibility of measuring noble gases in martian rocks and air by future robotic missions such as the Mars Science Laboratory (MSL). The MSL mission has, as part of its payload, the Sample Analysis at Mars (SAM) instrument, which consists of a pyrolysis oven integrated with a GCMS. The MSL SAM instrument has the capability to measure noble gas compositions of martian rocks and atmosphere. Here we suggest the possibility of K-Ar age dating based on noble gas release of martian rocks by conducting laboratory simulation experiments on terrestrial basalts and martian meteorites. We provide requirements for the SAM instrument to obtain adequate noble gas abundances and compositions within the current SAM instrumental operating conditions, especially, a power limit that prevents heating the furnace above approx.1100 C. In addition, Martian meteorite analyses from NASA-JSC will be used as ground truth to evaluate the feasibility of robotic experiments to constrain the ages of martian surface rocks.

Park, J.; Ming, D. W.; Garrison, D. H.; Jones, J. H.; Bogard, D. D.; Nagao, K.

2009-01-01

330

Effects of atmospheric entry heating on the noble gas and nitrogen content of micrometeorites  

NASA Astrophysics Data System (ADS)

Fragments of the carbonaceous chondrite Orgueil were subjected to pulse-heating sequences in order to simulate the heating conditions experienced by micrometeorites (MMs) upon entry into Earth's atmosphere. By increasing the experimental run times from 2 to 120 s at a fixed temperature of 1350?C, the different textures of natural MMs (from non-vesicular fine-grained particles to melted cosmic spherules) were reproduced, and the noble gas (He, Ne, Ar) and nitrogen abundances and isotope ratios of the MM analogues were subsequently determined by CO2 laser extraction-static mass spectrometry analysis. The starting material shows a heterogeneous He-Ne-Ar-N signature, consistent with the mineralogical heterogeneity of CI chondrites and the inhomogeneous distribution of various noble gas and nitrogen components among meteoritic minerals. Nonetheless, our experiments demonstrate that moderately to strongly heated Orgueil fragments retain only a few percent of their initial noble gas and nitrogen inventories, indicating that atmospheric entry heating results in extensive degassing of meteoritic dust particles. The evolution of the noble gas and nitrogen isotope ratios may, in part, be explained by equilibration with the atmosphere; however, the decreasing ?15N values may also indicate preferential degradation of a 15N-rich component by thermal processing of chondritic matter. Furthermore, the efficient loss of helium and cosmogenic neon during heating will lead to an underestimate of the 3He and 21Ne exposure ages of MMs, as well as to large uncertainties for cosmic dust accretion rates derived from extraterrestrial 3He abundances in deep-sea sediments or polar ice cores. While the relative proportions of infalling cometary and asteroidal dust on Earth are unknown, the contribution of noble gases, nitrogen, and water from cosmic dust to the terrestrial volatile inventory appears negligible.

Fri, Evelyn; Alon-Toppani, Alice; Marty, Bernard; Libourel, Guy; Zimmermann, Laurent

2013-09-01

331

Noble Metal Nanoparticles for Biosensing Applications  

PubMed Central

In the last decade the use of nanomaterials has been having a great impact in biosensing. In particular, the unique properties of noble metal nanoparticles have allowed for the development of new biosensing platforms with enhanced capabilities in the specific detection of bioanalytes. Noble metal nanoparticles show unique physicochemical properties (such as ease of functionalization via simple chemistry and high surface-to-volume ratios) that allied with their unique spectral and optical properties have prompted the development of a plethora of biosensing platforms. Additionally, they also provide an additional or enhanced layer of application for commonly used techniques, such as fluorescence, infrared and Raman spectroscopy. Herein we review the use of noble metal nanoparticles for biosensing strategiesfrom synthesis and functionalization to integration in molecular diagnostics platforms, with special focus on those that have made their way into the diagnostics laboratory.

Doria, Goncalo; Conde, Joao; Veigas, Bruno; Giestas, Leticia; Almeida, Carina; Assuncao, Maria; Rosa, Joao; Baptista, Pedro V.

2012-01-01

332

Fossil brines preserved in the St-Lawrence Lowlands, Qubec, Canada as revealed by their chemistry and noble gas isotopes  

Microsoft Academic Search

Brines in Cambrian sandstones and Ordovician dolostones of the St-Lawrence Lowlands at Bcancour, Qubec, Canada were sampled for analysis of all stable noble gases in order to trace their origin and migration path, in addition to quantifying their residence time. Major ion chemistry indicates that the brines are of NaCaCl type, possibly derived from halite dissolution. 87Sr\\/86Sr ratios and Ca

Daniele L. Pinti; Catherine Bland-Otis; Alain Tremblay; Maria Clara Castro; Chris M. Hall; Jean-Sbastien Marcil; Jean-Yves Lavoie; Raynald Lapointe

2011-01-01

333

A fluid-based measurement system for airborne radioxenon surveillance  

Microsoft Academic Search

A new and innovative technique for concentrating heavy noble gases from the atmosphere and subsequently measuring the radioactive xenon isotopes has recently been developed at Argonne National Laboratory. The concentration technique is based on the discovery of a phenomenon where certain organic fluids absorb heavy noble gases with very high efficiency at room temperature and release the noble gases when

B. Rooney; K. C. Gross; R. Nietert; J. Valentine; W. Russ

1997-01-01

334

Results from the XENON10 and the Race to Detect Dark Matter with Noble Liquids  

ScienceCinema

Detectors based on liquid noble gases have the potential to revolutionize the direct search for WIMP dark matter. The XENON10 experiment, of which I am a member, has recently announced the results from it's first data run and is now the leading WIMP search experiment. This and other experiments using xenon, argon and neon have the potential to rapidly move from the current kg-scale target mass to the ton scale and well beyond. This should allow a (nearly) definitive test or discovery of dark matter if it is in the form of weakly interacting massive particles.

335

Bamboo Pointer belonging to Levi F. Noble  

USGS Multimedia Gallery

The pointer is a souvenir from the Third Pan-Pacific Science Congress held in Tokyo in 1926. A prominent geologist, Noble (1882-1965) spent his entire career with the U.S. Geological Survey. He began field investigations in 1917, which continued on and off for the next 45 years, where he observed an...

2009-07-20

336

Noble liquid detectors for dark matter.  

NASA Astrophysics Data System (ADS)

Experiments based on noble liquid targets are now providing competitive sensitivities in the race for the direct detection of particle dark matter. Theoretical estimates, based on supersymmetric models predict dark matter interaction rates from the best sensitivity of existing direct detection experiments of 1 evts/kg/month, down to rates of 1 evts/100 kg/yr, and below this. Current noble liquid experiments for dark matter searches, range in scale from 10 to 1000 kg, and are designed to rise to this challenge. Ar, Ne and Xe targets permit the discrimination of electron recoils, coming from gamma ray and beta backgrounds, versus nuclear recoils, characteristic of WIMP events. This is done using scintillation light pulse shapes, and/or the ratio of ionization to scintillation generated in the target by the interaction. The detectors are also able to significantly reduce backgrounds through the use of position resolution in large volumes, combined with active self-shielding, to reach very low levels in inner fiducial volumes. A growing understanding of how to exploit these characteristics, and construct larger detectors, will allow further significant improvements in the sensitivity of noble liquid experiments. Current and future noble liquid detector experiments include: ArDM, LUX, (mini)CLEAN/DEAP, WARP, XENON, XMASS, XMASS-DM, ZEPLIN

Gaitskell, Richard

2007-04-01

337

MICROWAVE-ASSISTED SYNTHESIS OF NOBLE NANOSTRUCTURES  

EPA Science Inventory

Microwave-assisted (MW) spontaneous reduction of noble metal salts, silver (Ag), gold (Au), platinum (Pt) and palladium (Pd) is reported using sugar solutions such as -D glucose, sucrose and maltose, etc. to generate nanomaterials. These MW-assisted reactions, conducted in aqueo...

338

Natural Death and the Noble Savage.  

ERIC Educational Resources Information Center

The belief that dying and grieving are natural processes is widely held in modern bereavement care. Examines four assumption often made in this connection: (1) most primitive cultures deal with death in an accepting way; (2) this way is different than our own; (3) it is a good and noble way; and (4) traditional societies see death as natural. (JBJ)

Walter, Tony

1995-01-01

339

Temporal changes in noble gas compositions within the Aidlinsector ofThe Geysers geothermal system  

SciTech Connect

The use of nonreactive isotopic tracers coupled to a full thermal-hydrological reservoir simulation allows for an improved method of investigating how reservoir fluids contained within matrix and fractures contribute over time to fluids produced from geothermal systems. A combined field and modeling study has been initiated to evaluate the effects of injection, production, and fracture-matrix interaction on produced noble gas contents and isotopic ratios. Gas samples collected periodically from the Aidlin steam field at The Geysers, California, between 1997 and 2006 have been analyzed for their noble gas compositions, and reveal systematic shifts in abundance and isotopic ratios over time. Because of the low concentrations of helium dissolved in the injection waters, the injectate itself has little impact on the helium isotopic composition of the reservoir fluids over time. However, the injection process may lead to fracturing of reservoir rocks and an increase in diffusion-controlled variations in noble gas compositions, related to gases derived from fluids within the rock matrix.

Dobson, Patrick; Sonnenthal, Eric; Kennedy, Mack; van Soest,Thijs; Lewicki, Jennifer

2006-05-03

340

Theory of warm ionized gases: equation of state and kinetic Schottky anomaly.  

PubMed

Based on accurate Lennard-Jones-type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analog in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed. In particular, the predicted plasma electron density in a sonoluminescent bubble turns out to be in good agreement with the value measured in recent experiments. PMID:24229140

Capolupo, A; Giampaolo, S M; Illuminati, F

2013-10-01

341

Microscopic theory of warm ionized gases: equation of state and kinetic Schottky anomaly  

NASA Astrophysics Data System (ADS)

Based on accurate Lennard-Jones type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analogue in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed.

Capolupo, A.; Giampaolo, S. M.; Illuminati, F.

2013-06-01

342

Theory of warm ionized gases: Equation of state and kinetic Schottky anomaly  

NASA Astrophysics Data System (ADS)

Based on accurate Lennard-Jones-type interaction potentials, we derive a closed set of state equations for the description of warm atomic gases in the presence of ionization processes. The specific heat is predicted to exhibit peaks in correspondence to single and multiple ionizations. Such kinetic analog in atomic gases of the Schottky anomaly in solids is enhanced at intermediate and low atomic densities. The case of adiabatic compression of noble gases is analyzed in detail and the implications on sonoluminescence are discussed. In particular, the predicted plasma electron density in a sonoluminescent bubble turns out to be in good agreement with the value measured in recent experiments.

Capolupo, A.; Giampaolo, S. M.; Illuminati, F.

2013-10-01

343

Applications of Noble Gas Radiation Detectors to Counter-terrorism  

NASA Astrophysics Data System (ADS)

Radiation detectors are essential tools in the detection, analysis and disposition of potential terrorist devices containing hazardous radioactive and/or fissionable materials. For applications where stand-off distance and source shielding are limiting factors, large detectors have advantages over small ones. The ability to distinguish between Special Nuclear Materials and false-positive signals from natural or man-made benign sources is also important. Ionization chambers containing compressed noble gases, notably xenon and helium-3, can be scaled up to very large sizes, improving the solid angle for acceptance of radiation from a distant source. Gamma spectrometers using Xe have a factor of three better energy resolution than NaI scintillators, allowing better discrimination between radioisotopes. Xenon detectors can be constructed so as to have extremely low leakage currents, enabling them to operate for long periods of time on batteries or solar cells. They are not sensitive to fluctuations in ambient temperature, and are therefore suitable for deployment in outdoor locations. Position-sensitive 3He chambers have been built as large as 3000 cm2, and with spatial resolution of less than 1 mm. Combined with coded apertures made of cadmium, they can be used to create images of thermal neutron sources. The natural background of spallation neutrons from cosmic rays generates a very low count rate, so this instrument could be quite effective at identifying a man-made source, such as a spontaneous fission source (Pu) in contact with a moderator (high explosive).

Vanier, Peter E.; Forman, Leon

2002-10-01

344

An Alteration Scale for CM Chondrites and Implications for Planetary Noble Gas Abundances  

NASA Astrophysics Data System (ADS)

Three progressive alteration parameters have been identified from the mineralogical and textural analyses of 7 CM chondritic falls. These indices predict the following order of progressive alteration [3]: Murchison (MC)noble gases, Ar^36, Xe^84, and Kr^132. Two of the progressive alteration parameters monitor the volumetric production of CM phyllosilicates, which was estimated from the modal analysis of 1 to 3 thin sections from each of the analyzed falls. These are the percentages of phyllosilicates in chondrules and the volume of anhydrous matrix silicates, which increase and decease, respectively, with progressive alteration. The third alteration index, the mean Fe^3+/(2-Si) ratio in phyllosilicates, is a stoichiometric-based approximation that monitors variations in mineral composition during progressive alteration, and decreases with increasing alteration. Values of Fe^3+/(2-Si) were calculated from an average of microprobe analyses of matrix phyllosilicates in each meteorite based on a generalized phyllosilicate stoichiometry, [(Fe, Mg)(sub)3-x (Al,Fe^3+)(sub)x(Si(sub)(2-x)(Al,Fe^3+)(sub)x)O(sub)5(OH)(sub)4], which accommodates a continuous transition from cronstedtite to serpentine compositions. The bulk Ar^36 content of the 7 investigated samples decreases with increasing alteration as predicted by the alteration parameters, which suggests the possibility of degassing events. The same trend is observed for Kr^84 and Xe^132. The loss of noble gases in CM chondritic meteorites has previously been noted [1,5], and may be related to the open-system behavior that is predicted for other volatile components in CM chondrites, such as C1 [4], water [3], and methane [2]. Although high-temperature minerals are depleted in noble gases relative to the low- temperature phases of CM chondrites, we observe decreasing noble gas abundances with increased volumes of low-temperature phases. This can be explained by a scenario similar to one proposed by Wood [7], in which all CM chondrites originally had high gas contents, and were subsequently degassed to varying degrees in response to aqueous alteration in a parent body setting. An alternate explanation is that the correlation between noble gas content and the degree of alteration is the fortuitous result of primary trapped gas abundances. If, however, degassing did occur in response to progressive alteration, then the sequence of alteration reactions in CM chondrites may provide additional constraints on the retention sites for trapped noble gases. References: [1] Bogard D. D. et al. (1971) JGR, 76, 4076-4083. [2] Bourcier W. L. et al. (1992) LPS XXIII, 143-144.[3] Browning L. B. et al. (1993) LPS XXIV. [4] Bunch T. E. and Chang S. (1980) GCA, 44, 1543-1577. [5] Mazor E. et al. (1970) GCA, 34, 781-824. [6] Schultz L. and Kruse H. (1989) Meteoritics, 24, 155-172. [6] Wood J. A. (1967) Icarus, 6, 1-49. Fig. 1, which appears here in the hard copy shows how averaged ^36Ar contents [6] for individual CM chondrites decrease with increasing alteration, as indicated by the mean composition of phyllosilicates.

Browning, L. B.; McSween, H. Y., Jr.; Zolensky, M.

1993-07-01

345

Electrical breakdown of gases  

Microsoft Academic Search

A collection of individual works on electrical discharges is presented. Topics covered include: fundamental processes in the electrical breakdown of gases; vacuum breakdown; spark breakdown in uniform fields; corona discharge; spark breakdown in non-uniform fields; breakdown voltage characteristics; irradiation and time lags; high-frequency breakdown of gases; laser-induced electrical breakdown of gases; spark channels; and electrode phenomena. (GHT)

J. M. Meek; J. D. Craggs

1978-01-01

346

A new noble gas paleoclimate record in Texas Basic assumptions revisited  

NASA Astrophysics Data System (ADS)

A generally accepted basic principle in relation to the use of the noble gas thermometer in groundwater flow systems is that high-frequency noble gas climatic signals are lost due to the effect of dispersion. This loss of signal, combined with 14C dating issues, makes it only suited to identify major climatic events such as the Last Glacial Maximum (LGM). Consequently, the identification of significant noble gas temperature (NGT) cooling (? 5 C) with respect to present time has systematically been associated with the occurrence of the LGM even when reasonable water age controls were unavailable. It has also become apparent at a number of studied sites that modern NGTs estimated through standard models [M. Stute, P. Schlosser, Principles and applications of the noble gas paleothermometer, in: P.K. Swart, K.C. Lohmann, J.A. McKenzie, S. Savin, (Eds), Climate change in continental isotopic records, Geophysical monograph 78, AGU (1993) 89-100.; W. Aeschbach-Hertig, F. Peeters, U. Beyerle, R. Kipfer, Paleotemperature reconstruction from noble gases in ground water taking into account equilibration with entrapped air, Nature 405(6790) (2000) 1040-1044.] are unable to reproduce ground temperatures at the interface with the unsaturated zone, a basic requirement for proper paleoclimate reconstruction through noble gases. Instead, a systematic bias to low NGTs in recharge areas is observed. The Carrizo aquifer, in which the LGM was previously identified [M. Stute, P. Schlosser, J.F. Clark, W.S. Broecker, Paleotemperatures in the Southwestern United States derived from noble gases in ground water, Science 256(5059) (1992) 1000-1001.] and which presents an NGT bias of over 4 C, is an ideal setting to analyze and revise basic principles and assumptions in relation with the use of the noble gas thermometer. Here, we present a new noble gas data set (49 measurements) collected at 20 different locations in the Carrizo aquifer. This new data set together with previously published data (20 measurements) was used to calibrate a 3-D groundwater flow and 4He transport model in which simulations of groundwater age were subsequently carried out. These account for mixing processes due to advection, dispersion, diffusion, and cross-formational flow. We first show that samples previously attributed to the LGM belong in fact to the middle Holocene. Through a step-by-step approach we then proceed to carry out a comparative analysis of both the impact of dispersion on high frequency climatic signals and assumptions underlying competing NGT models. Our combined analysis indicates that groundwater flow systems, at least those with similar characteristics to that of the Carrizo, do have the ability to preserve short term (100-200 yrs) climatic fluctuations archived by noble gases. It also shows that abrupt climate shifts during the mid-late Holocene which are associated with significant NGT changes (? 5 C) do not reflect equally important changes in the mean annual atmospheric temperature (MAAT). Instead, these reflect the combined effect of atmospheric temperature changes, seasonality of recharge and, above all, significant variations of the water table depth which result from shifts between humid and arid regimes. Together with NGTs, our excess air record plays a critical role in identifying such abrupt climate changes. Specifically, the Carrizo combined data set indicates an abrupt shift from a cool, humid regime to a warmer, arid one at 1 kyrs BP. A major Holocene ( 6 kyrs BP) NGT change of 7.7 C with respect to present now identified is mostly the result of a dramatic water table drop which occurred during the 1 kyrs BP transition period. Current NGTs in the Carrizo recharge area do not appear to be recording atmospheric changes. Rather, these are recording ground conditions reflecting mostly the impact of heat flow in the area. We also show that observed systematic offsets in NGT recharge areas can be reconciled through NGT estimation models which account for a noble gas partial pressure increase in the unsaturated zone, poten

Castro, Maria Clara; Hall, Chris Michael; Patriarche, Delphine; Goblet, Patrick; Ellis, Brian Robert

2007-05-01

347

Quantifying noble gas contamination during terrestrial alteration in Martian meteorites from Antarctica  

NASA Astrophysics Data System (ADS)

We investigated exterior and interior subsamples from the Martian shergottite meteorites Allan Hills (ALH) A77005 and Roberts Massif (RBT) 04261 for secondary minerals, oxygen isotopes, Ar-Ar, and noble gas signatures. Electron microprobe investigations revealed that RBT 04261 does not contain any visible alteration even in its most exterior fractures, whereas fracture fillings in ALHA77005 penetrate into the meteorite up to 300 ?m, beyond which the fractures are devoid of secondary minerals. Light noble gases seem to be almost unaffected by terrestrially induced alteration in both meteorites. Thus, a shock metamorphic overprint of 30-35 GPa can be deduced from the helium measurements in RBT 04261. Oxygen isotopes also seem unaffected by terrestrially weathering and variations can easily be reconciled with the differences in modal mineralogy of the exterior and interior subsamples. The measurements on irradiated samples (Ar-Ar) showed a clear Martian atmospheric contribution in ALHA77005, but this is less apparent in our sample of RBT 04261. Exterior and interior subsamples show slight differences in apparent ages, but the overall results are very similar between the two. In contrast, krypton and xenon are severely affected by terrestrial contamination, demonstrating the ubiquitous presence of elementally fractionated air in RBT 04261. Although seemingly contradictory, our results indicate that RBT 04261 was more affected by contamination than ALHA77005. We conclude that irrespective of on which planet the alteration occurred, exposure of Martian rocks to atmosphere (or brine) introduces noble gases with signatures elementally fractionated relative to the respective atmospheric composition into the rock, and relationships of that process with oxygen isotopes or mineralogical observations are not straightforward.

Schwenzer, S. P.; Greenwood, R. C.; Kelley, S. P.; Ott, U.; Tindle, A. G.; Haubold, R.; Herrmann, S.; Gibson, J. M.; Anand, M.; Hammond, S.; Franchi, I. A.

2013-06-01

348

Developments in Noble Gas mass spectrometry  

Microsoft Academic Search

D. HAMILTON*, J.B. SCHWIETERS, D. TUTTAS, M. KRUMMEN, M. DEERBERG, N.S. LLOYD1 1Thermo Fisher Scientific, Hanna-Kunath-Str. 11, 28199 Bremen, Germany (*correspondence: Doug.Hamilton@ThermoFisher.com) Recent advances in ion optics and electronic design have added features to the new range of Noble Gas mass spectrometers from Thermo Fisher Scientific that will enable the scientific community to resolve a number of existing analytical limitations.

J. B. Schwieters; N. S. Lloyd

2010-01-01

349

Complex oxide-noble metal conjugated nanoparticles.  

PubMed

Hybrid nanoparticles (NPs) composed of multiple components offer new opportunities for next-generation materials. In this study, a paradigm for the noble metal/ternary complex oxide hybrid NPs is reported by adopting pulsed laser ablation in liquids. As model hybrids, gold-spinel heterodimer (Au-CoFe2O4) and gold-pervoskite heterodimer (Au-SrTiO3) NPs are investigated. This work has demonstrated the diverse playgroup of NP conjugation enlarged by complex oxides. PMID:23427105

Guo, Jun-Ling; Chiou, Yao-De; Liang, Wen-I; Liu, Heng-Jui; Chen, Ying-Jiun; Kuo, Wei-Cheng; Tsai, Chih-Ya; Tsai, Kai-An; Kuo, Ho-Hung; Hsieh, Wen-Feng; Juang, Jenh-Yih; Hsu, Yung-Jung; Lin, Hong-Ji; Chen, Chien-Te; Liao, Xue-Pin; Shi, Bi; Chu, Ying-Hao

2013-04-11

350

Separation of polar gases from nonpolar gases  

DOEpatents

The separation of polar gases from nonpolar gases may be effected by passing a mixture of nonpolar gases over the face of a multicomponent membrane at separation conditions. The multicomponent membrane which is used to effect the separation will comprise a mixture of a glycol plasticizer having a molecular weight of from about 200 to about 600 and an organic polymer cast on a porous support. The porous support is pretreated prior to casting of the mixture thereon by contact with a polyhydric alcohol whereby the pores of the support are altered, thus adding to the increased permeability of the polar gas.

Kulprathipanja, S.

1986-08-19

351

Separation of polar gases from nonpolar gases  

DOEpatents

The separation of polar gases from nonpolar gases may be effected by passing a mixture of nonpolar gases over the face of a multicomponent membrane at separation conditions. The multicomponent membrane which is used to effect the separation will comprise a mixture of a glycol plasticizer having a molecular weight of from about 200 to about 600 and an organic polymer cast on a porous support. The porous support is pretreated prior to casting of the mixture thereon by contact with a polyhydric alcohol whereby the pores of the support are altered, thus adding to the increased permeability of the polar gas.

Kulprathipanja, Santi (Hoffman Estates, IL)

1986-01-01

352

Separation of polar gases from nonpolar gases  

DOEpatents

Polar gases such as hydrogen sulfide, sulfur dioxide and ammonia may be separated from nonpolar gases such as methane, nitrogen, hydrogen or carbon dioxide by passing a mixture of polar and nonpolar gases over the face of a multicomponent membrane at separation conditions. The multicomponent membrane which is used to effect the separation will comprise a mixture of a glycol plasticizer having a molecular weight of from about 200 to about 600 and an organic polymer cast on a porous support. The use of such membranes as exemplified by polyethylene glycol and silicon rubber composited on polysulfone will permit greater selectivity accompanied by a high flux rate in the separation process.

Kulprathipanja, S.; Kulkarni, S.S.

1986-08-26

353

Separation of polar gases from nonpolar gases  

DOEpatents

Polar gases such as hydrogen sulfide, sulfur dioxide and ammonia may be separated from nonpolar gases such as methane, nitrogen, hydrogen or carbon dioxide by passing a mixture of polar and nonpolar gases over the face of a multicomponent membrane at separation conditions. The multicomponent membrane which is used to effect the separation will comprise a mixture of a glycol plasticizer having a molecular weight of from about 200 to about 600 and an organic polymer cast on a porous support. The use of such membranes as exemplified by polyethylene glycol and silicon rubber composited on polysulfone will permit greater selectivity accompanied by a high flux rate in the separation process.

Kulprathipanja, Santi (Hoffman Estates, IL) [Hoffman Estates, IL; Kulkarni, Sudhir S. (Hoffman Estates, IL) [Hoffman Estates, IL

1986-01-01

354

Noble metallic nanostructures: preparation, properties, applications  

NASA Astrophysics Data System (ADS)

The process of formation and the characteristics are studied of noble metal nanostructures created by pulsed laser ablation in vacuum. Femtosecond (fs) and nanosecond (ns) laser systems lasing at different wavelengths are used. Several different modifications of the pulsed lased deposition (PLD) technique, as off-axis deposition and glancing angle deposition configurations are used to create nanostructures. Laser annealing of single or bimetal thin films is used to fabricate alloyed nanostructures. The possibility is demonstrated of tuning the optical properties of gold nanostructures on flexible substrates. Different experimental techniques, as fast photography, optical emission spectroscopy, FE-SEM, AFM, TEM, and Raman spectroscopy are applied to characterize the noble metallic nanostructures produced. The optical spectra of the Au and Ag nanostructures are also studied experimentally and theoretically. The theoretical simulation methods used are: molecular dynamic (MD), finite difference time domain (FDTD) and a method based on the generalized multi-particle Mie (GMM) theory. Applications of noble metal nanostructures to surface enhanced Raman spectroscopy (SERS) and biophotonics are briefly considered.

Atanasov, P. A.; Nedyalkov, N. N.; Dikovska, A. Og; Nikov, Ru; Amoruso, S.; Wang, X.; Bruzzese, R.; Hirano, K.; Shimizu, H.; Terakawa, M.; Obara, M.

2014-05-01

355

Detection of Noble Gas Radionuclides from an Underground Nuclear Explosion During a CTBT On-Site Inspection  

NASA Astrophysics Data System (ADS)

The development of a technically sound approach to detecting the subsurface release of noble gas radionuclides is a critical component of the on-site inspection (OSI) protocol under the Comprehensive Nuclear Test Ban Treaty. In this context, we are investigating a variety of technical challenges that have a significant bearing on policy development and technical guidance regarding the detection of noble gases and the creation of a technically justifiable OSI concept of operation. The work focuses on optimizing the ability to capture radioactive noble gases subject to the constraints of possible OSI scenarios. This focus results from recognizing the difficulty of detecting gas releases in geologic environmentsa lesson we learned previously from the non-proliferation experiment (NPE). Most of our evaluations of a sampling or transport issue necessarily involve computer simulations. This is partly due to the lack of OSI-relevant field data, such as that provided by the NPE, and partly a result of the ability of computer-based models to test a range of geologic and atmospheric scenarios far beyond what could ever be studied by field experiments, making this approach very highly cost effective. We review some highlights of the transport and sampling issues we have investigated and complete the discussion of these issues with a description of a preliminary design for subsurface sampling that addresses some of the sampling challenges discussed here.

Carrigan, Charles R.; Sun, Yunwei

2014-03-01

356

Subduction-related metasomatism recorded as noble gas compositions in the Finero Phlogopite-Peridotites, Italian Western Alps  

NASA Astrophysics Data System (ADS)

It has been demonstrated that noble gases trapped in fluid inclusions of ultramafic xenoliths are quite useful tracers of metasomatic events in the lithospheric mantle. Some recent study on noble gases in Horoman ultramafic complex, Hokkaido, Japan, revealed that the orogenic peridotites can also be a suitable target for noble gas study and that they contain a homogeneous mixture of mantle-He and air-Ar, suggesting a possible recycling and preservation of heavier noble gases of surface reservoirs in the deeper mantle domains (Matsumoto et al., 2001). Here we report results of our new investigation on noble gases in a unique specimen having thin layer of very fine-grained apatite and opx in the fresh phlogopite lherzolite from Finero ultramafic complex, Italian Western Alps. We have also examined fresh olivine grains separated from a phlogopite-lherzolite without such apatite-layer. The fluid inclusions of this olivine separates appeared to be very rich in radiogneic component such as 4He, 21Ne and 40Ar, suggesting the derivation of fluids from a crust-like reservoir. Such a crustal component appeared to be also contained in the samples with the apatite-opx layer, but we need to have an additional isotopically distinct component to explain progressive increase in 3He concentration and decrease in 40Ar/36Ar ratios observed towards the apatite-rich layer. High 3He contents and low 40Ar/36Ar ratios are consistent with the signature expected for the slab-derived metasomatic fluid as was observed in Horoman ultramafic complex. There is a clear mixing trend defined in a 3He/36Ar versus 40Ar/36Ar diagram with the crustal and slab-derived fluids as endmember compositions, suggesting that the complex had metsomatised by fluids derived from geochemically distinct regions at distinct geotectonic settings. The parental melt or fluids responsible for the formation of the apatite-rich layer should be derived from the slab-derived component, which is consistent with a notion that the Finero mantle was once in the mantle wedge.

Matsumoto, T.; Morishita, T.; Matsuda, J.; Fujioka, T.; Takebe, M.; Yamamoto, K.; Arai, S.

2002-12-01

357

Noble gas adsorption with and without mechanical stress: Not Martian signatures but fractionated air  

NASA Astrophysics Data System (ADS)

Sample preparation, involving physical and chemical methods, is an unavoidable step in geochemical analysis. From a noble gas perspective, the two important effects are loss of sample gas and/or incorporation of air, which are significant sources of analytical artifacts. This article reports on the effects of sample exposure to laboratory air without mechanical influence and during sample grinding. The experiments include pure adsorption on terrestrial analog materials (gibbsite and olivine) and grinding of Martian meteorites. A consistent observation is the presence of an elementally fractionated air component in the samples studied. This is a critical form of terrestrial contamination in meteorites as it often mimics the heavy noble gas signatures of known extra-terrestrial end-members that are the basis of important conclusions about the origin and evolution of a meteorite. Although the effects of such contamination can be minimized by avoiding elaborate sample preparation protocols, caution should be exercised in interpreting the elemental ratios (Ar/Xe, Kr/Xe), especially in the low-temperature step extractions. The experiments can also be transferred to the investigation of Martian meteorites with long terrestrial residence times, and to Mars, where the Mars Science Laboratory mission will be able to measure noble gas signatures in the current atmosphere and in rocks and soils collected on the surface in Gale crater.

Schwenzer, Susanne P.; Herrmann, Siegfried; Ott, Ulrich

2012-06-01

358

Seeding approach to noble metal decorated conducting polymer nanofiber network  

NASA Astrophysics Data System (ADS)

Metal displacement reactions between conducting polymers--``synthetic metals''--and noble metals (Pt, Au and Ag) have been demonstrated using a seeding polymerization technique, to produce a synthetic metal nanofiber network decorated with noble metal nanoparticles, in one-step.Metal displacement reactions between conducting polymers--``synthetic metals''--and noble metals (Pt, Au and Ag) have been demonstrated using a seeding polymerization technique, to produce a synthetic metal nanofiber network decorated with noble metal nanoparticles, in one-step. Electronic supplementary information (ESI) available: Enlarged images and the experimental details. See DOI: 10.1039/c1nr10994d

Liu, Zhen; Poyraz, Selcuk; Liu, Yang; Zhang, Xinyu

2011-12-01

359

Inert electrode containing metal oxides, copper and noble metal  

DOEpatents

A cermet composite material is made by treating at an elevated temperature a mixture comprising a compound of iron and a compound of at least one other metal, together with an alloy or mixture of copper and a noble metal. The alloy or mixture preferably comprises particles having an interior portion containing more copper than noble metal and an exterior portion containing more noble metal than copper. The noble metal is preferably silver. The cermet composite material preferably includes alloy phase portions and a ceramic phase portion. At least part of the ceramic phase portion preferably has a spinel structure.

Ray, Siba P. (Murrysville, PA); Woods, Robert W. (New Kensington, PA); Dawless, Robert K. (Monroeville, PA); Hosler, Robert B. (Sarver, PA)

2001-01-01

360

Inert electrode containing metal oxides, copper and noble metal  

DOEpatents

A cermet composite material is made by treating at an elevated temperature a mixture comprising a compound of iron and a compound of at least one other metal, together with an alloy or mixture of copper and a noble metal. The alloy or mixture preferably comprises particles having an interior portion containing more copper than noble metal and an exterior portion containing more noble metal than copper. The noble metal is preferably silver. The cermet composite material preferably includes alloy phase portions and a ceramic phase portion. At least part of the ceramic phase portion preferably has a spinel structure.

Ray, Siba P. (Murrysville, PA); Woods, Robert W. (New Kensington, PA); Dawless, Robert K. (Monroeville, PA); Hosler, Robert B. (Sarver, PA)

2000-01-01

361

Noble gas and oxygen isotope studies of aubrites: A clue to origin and histories  

NASA Astrophysics Data System (ADS)

Noble gas measurements were performed for nine aubrites: Bishopville, Cumberland Falls, Mayo Belwa, Mount Egerton, Norton County, Pea Blanca Spring, Shallowater, ALHA 78113 and LAP 02233. These data clarify the origins and histories, particularly cosmic-ray exposure and regolith histories, of the aubrites and their parent body(ies). Accurate cosmic-ray exposure ages were obtained using the 81Kr-Kr method for three meteorites: 52 3, 49 10 and 117 14 Ma for Bishopville, Cumberland Falls and Mayo Belwa, respectively. Mayo Belwa shows the longest cosmic-ray exposure age determined by the 81Kr-Kr method so far, close to the age of 121 Ma for Norton County. These are the longest ages among stony meteorites. Distribution of cosmic-ray exposure ages of aubrites implies 4-9 break-up events (except anomalous aubrites) on the parent body. Six aubrites show "exposure at the surface" on their parent body(ies): (i) neutron capture 36Ar, 80Kr, 82Kr and/or 128Xe probably produced on the respective parent body (Bishopville, Cumberland Falls, Mayo Belwa, Pea Blanca Spring, Shallowater and ALHA 78113); and/or (ii) chondritic trapped noble gases, which were likely released from chondritic inclusions preserved in the aubrite hosts (Cumberland Falls, Pea Blanca Spring and ALHA 78113). The concentrations of 128Xe from neutron capture on 127I vary among four measured specimens of Cumberland Falls (0.5-76 10 -14 cm 3STP/g), but are correlated with those of radiogenic 129Xe, implying that the concentrations of ( 128Xe) n and ( 129Xe) rad reflect variable abundances of iodine among specimens. The ratios of ( 128Xe) n/( 129Xe) rad obtained in this work are different for Mayo Belwa (0.045), Cumberland Falls (0.015) and Shallowater (0.001), meaning that neutron fluences, radiogenic 129Xe retention ages, or both, are different among these aubrites. Shallowater contains abundant trapped Ar, Kr and Xe (2.2 10 -7, 9.4 10 -10 and 2.8 10 -10 cm 3STP/g, respectively) as reported previously ( Busemann and Eugster, 2002). Isotopic compositions of Kr and Xe in Shallowater are consistent with those of Q (a primordial noble gas component trapped in chondrites). The Ar/Kr/Xe compositions are somewhat fractionated from Q, favoring lighter elements. Because of the unbrecciated nature of Shallowater, Q-like noble gases are considered to be primordial in origin. Fission Xe is found in Cumberland Falls, Mayo Belwa, Pea Blanca Spring, ALHA 78113 and LAP 02233. The majority of fission Xe is most likely 244Pu-derived, and about 10-20% seems to be 238U-derived at 136Xe. The observed ( 136Xe) Pu corresponds to 0.019-0.16 ppb of 244Pu, from which the 244Pu/U ratios are calculated as 0.002-0.009. These ratios resemble those of chondrites and other achondrites like eucrites, suggesting that no thermal resetting of the Pu-Xe system occurred after 4.5 Ga ago. We also determined oxygen isotopic compositions for four aubrites with chondritic noble gases and a new aubrite LAP 02233. In spite of their chondritic noble gas signatures, oxygen with chondritic isotopic compositions was found only in a specimen of Cumberland Falls (? 17O of 0.3). The other four aubrites and the other two measured specimens of Cumberland Falls are concurrent with the typical range for aubrites.

Miura, Yayoi N.; Hidaka, Hiroshi; Nishiizumi, Kunihiko; Kusakabe, Minoru

2007-01-01

362

Recycling of volatiles at subduction zones: Noble gas evidence from the Tabar-Lihir-Tanga-Feni arc of papua New Guinea  

NASA Technical Reports Server (NTRS)

Convergent margin processes play an important but poorly understood role in the distribution of terrestrial volatile species. For example, subduction processes filter volatiles from the subducting package, thereby restricting their return to the mantle. In addition, once extracted from the downgoing slab, volatiles become an essential component in the petrogenesis of island arc magmas. The noble gases, with their systematic variation in physical properties and diversity of radiogenic isotopes, should carry a uniquely valuable record of these processes. However, thus far studies of noble gases in arc volcanics have achieved only limited success in this regard. Subduction-related lavas and geothermal fluids carry (3)He/(4)He ratios equal to or slightly lower than those found in the depleted upper mantle source of mid-ocean ridge basalts. Apparently slab-derived helium (which should have (3)He/(4)He much less than MORB) is extensively diluted by MORB-like helium from the mantle wedge, making it difficult to use helium as a tracer of convergent margin processes. Interpretation of the heavier noble gases (Ne-Ar-Kr-Xe) in arc lavas has also proven difficult, because the lavas carry low noble gas concentrations and hence are subject to pervasive atmospheric contamination. The low noble gas concentrations may be a consequence of degassing in the high level magma chambers characteristic of arc stratovolcanos. We have recently initiated a project to better constrain the behavior of volatiles in subduction zones through geochemical studies of the tectonically unusual volcanoes of the Tabar-Lihir-Tanga-Feni (TLTF) arc in the Bismarck Archipelago, Papua New Guinea.

Farley, Kenneth; Mcinnes, Brent; Patterson, Desmond

1994-01-01

363

Isotopic studies of rare gases in terrestrial samples and natural nucleosynthesis  

SciTech Connect

This project is concerned with research in rare gas mass spectrometry. We read the natural record that isotopes of the rare gases provide. We study fluids using a system (RARGA) that is sometimes deployed in the field. In 1990 there was a strong effort to reduce the backlog of RARGA samples on hand, so that it was a year of intensive data gathering. Samples from five different areas in the western United States and samples from Guatemala and Australia were analyzed. In a collaborative study we also began analyzing noble gases from rocks associated with the fluids. An important objective, continuing in 1991, is to understand better the reasons for somewhat elevated {sup 3}He/{sup 4}He ratios in regions where there is no contemporary volcanism which could produce the effect by addition of mantle helium. Our helium data have given us and our collaborators some insights, which are to be followed up, into gold mineralization in geothermal regions. Our DOE work in calibrating a sensitive laser microprobe mass spectrometer for noble gases in fluid inclusions continues. Having completed a series of papers on noble gases in diamonds, we next will attempt to make precise isotopic measurements on xenon from mantle sources, in search of evidence for terrestrially elusive {sup 244}Pu decay.

Not Available

1990-07-01

364

New noble gas data of primitive and differentiated achondrites including Northwest Africa 011 and Tafassasset  

NASA Astrophysics Data System (ADS)

This work reports on the noble gas inventory of 3 new acapulcoites, 3 brachinites, 2 new eucrites from the Dar al Gani region in Libya, the unique achondrite Dar al Gani (DaG) 896 from the same locality, the new eucrite-like achondrite Northwest Africa (NWA) 011, and the controversial sample Tafassasset. We determined cosmic ray exposure and gas retention ages, evaluated shielding conditions, and discuss the trapped noble gas component of the specimens. All exposure ages are within the known range of stony meteorites and partly confirm previously established age clusters. Shielding conditions vary, suggesting substantial shielding for all 3 brachinites and Tafassasset. We cannot exclude, however, that the Mg-rich composition of brachinites simply simulates heavy shielding. Regarding the trapped component, we found Q-like compositions only for the acapulcoite Thiel Mountains (TIL) 99002. The brachinite Elephant Moraine (EET) 99402 yields a high, subsolar 36Ar/ 132Xe ratio of ~400 along with a slightly elevated 84Kr/132Xe ratio, indicating minor atmospheric contamination. All the other samples, particularly the eucrite DaG 983, are characterized by clearly elevated Ar/Kr/Xe ratios due to significant terrestrial alteration. Tafassasset exhibits noble gas parameters that are different from those of CR chondrites, including a relatively high cosmic ray exposure age, the absence of a solar component, low 132Xe concentrations, a low trapped 36Ar/132Xe ratio of ~30, and a noticeable amount of radiogenic 129Xe. Similar attributes have been observed for some primitive achondrites. These attributes are also consistent with the metamorphic character of the sample. We, therefore, consider Tafassasset's noble gas record to be inconclusive as to its classification (primitive achondrite versus metamorphosed CR chondrite).

Patzer, A.; Schultz, L.; Franke, L.

2003-10-01

365

Nitrogen and Carbon Isotopes in Presolar Diamond Samples with Known Noble Gas Isotope Signature  

NASA Astrophysics Data System (ADS)

Since the first analyses of C and N isotopes in presolar diamonds with known noble gas isotope composition more than a decade ago [1,2] the investigation of these isotope systems in the diamonds were developed practicallly independently. During this time many interesting details in isotopic systematics of all the elements involved were found and reviewed [3-5]. The main conclusion now reached from a decade of investigation is that presolar diamonds from different meteorites are not identical but appear to consist of several populations [6-8]. Therefore a variety of circumstellar conditions may be involved through a type II supernova model is a good start point in trying to understand diamond synthesis [9]. The evidences from experimental data for all the isotope systems however are still not entirely consistent in the sense that we actually do not know how many carriers the diamonds represent and how the various noble gas carriers are related to those for nitrogen. The finding of a consensus between noble gas and light element analyses would seem to be a vital step so that more detailed nucleosynthesis models may be developed tor the diamond formation. A first point is to answer the question whether HL noble gases and light nitrogen must have been formed at the same astrophysical site. Another important achievement in terms of presolar diamond investigations during the last decade is the purity and number of samples now available. However a well known difficulty is that C, N, and noble gases are never measured all together on the same sample. The purpose of collaboration initiated in this paper is to exploit the availability of good quality samples and to go some way towards overcoming the difficulties of measurement technique incompatibility. We have analyzed three pure diamond samples separated at CalTech from Allende, Orgueil, (henceforth CT samples) and Leoville for N and C isotopic composition by stepped pyrolysis and combustion. The samples preparation and the noble gas results are described in detail elsewhere [7]. It should be noted that sample purity is supposed to be an important condition affecting release pattern of noble gases and N due to chemical reaction between coexisting minerals (for further discussion see [10]. Therefore we expected the influence of the reactions to be eliminated or significantly reduced for the samples studied here compared to those (OU samples) analyzed [6,8] before. Surprisingly we did not find any particular difference in C and N isotope systematics for the CT and OU samples. In particular they have the same carbon and N release profiles and isotope systematics (Figs. 1,2) although OU samples were measured without any attempt to remove spinel, SiC, or other oxidizing acid resistant phases. At low temperature pyrolysis steps, the CT samples have a similar peak of C, which we have previously correlated with P3 noble gases [11]. More important, release temperature of the light nitrogen from the CT samples (Fig. 2) is now confirmed to be significantly lower than that for HL noble gases supporting the hypothesis [11,12] of different carriers for the components or an entirely different release mechanism. Perhaps the most surprising outcome of our investigation was that none of the CT samples measured appeared to be 100% carbon; the reason for this apparent discrepancy ;the at present not clear. References: [1] Swart P. K. et al. (1983) Science, 220, 406-410. [2] Lewis R. S. et a1. (1983) Nature, 305, 767-771. [3] Pillinger C. T. (1993) Phil. Trans. Roy. Soc. Lond. A, 343, 73-76. [4] Anders E. and Zinner E. (1993) Meteoritics, 28, 490-514. [5] Ott U. (1993) Nature, 364, 25-33. [6] Russell S. S. et al. (1991) Science, 254, 1188-1191. [7] Huss G. R. and Lewis R. S. (1994) Meteoritics, in press. [8] Verchovsky A. B. et al. (1993) LPS XXV, 1435-1436. [9] Clayton D. D. et al. (1994) Astrophysics J., in press. [10] Verchovsky A. B. et al. (1994) Meteoritics, this volume. [11] Verchovsky A. B. et al. (1993) Meteoritics, 28, 52-53. [12] Verchovsky A. B. et a1. (1993) LPS XXIV, 1461-1462. Fig. 1

Verchovsky, A. B.; Huss, G. R.; Pillinger, C. T.

1994-07-01

366

Trends in source gases  

NASA Technical Reports Server (NTRS)

Source gases are defined as those gases that, by their breakdown, introduce into the stratosphere halogen, hydrogen, and nitrogen compounds that are important in stratospheric ozone destruction. Given here is an update of the existing concentration time series for chlorocarbons, nitrous oxide, and methane. Also reviewed is information on halogen containing species and the use of these data for establishing trends. Also reviewed is evidence on trends in trace gases that influence tropospheric chemistry and thus the tropospheric lifetimes of source gases, such as carbon dioxide, carbon monoxide, or nitrogen oxides. Much of the information is given in tabular form.

Ehhalt, D. H.; Fraser, P. J.; Albritton, D.; Cicerone, R. J.; Khalil, M. A. K.; Legrand, M.; Makide, Y.; Rowland, F. S.; Steele, L. P.; Zander, R.

1989-01-01

367

Noble Gas Sampling System Model 1  

SciTech Connect

The Noble Gas Sampling System (NGSS) is one of the finest air sampling devices available. This instrument represents the successful culmination of many years of research and development in the field of air sampling and testing. The equipment is extremely versatile, reliable and operator-friendly to serve your needs for many years to come. The NGSS is a programmable controlled device that collects and stores air in sample tanks at a constant volumetric flow rate over a preset time period. Constant volumetric flow through an orifice or nozzle happens when the differential pressure across the orifice is sufficient to create a critical flow condition.

Not Available

1992-07-01

368

Noble gas evidence for a lower mantle component in MORBs from the southern East Pacific Rise: Decoupling of helium and neon isotope systematics  

Microsoft Academic Search

Abundances and isotopic compositions of all noble gases have been determined in basalt glasses from different latitudes on the 1323S section of the East Pacific Rise. In this region earlier work has identified isotopic signatures of Sr, Nd, and Pb as well as He which indicate a plume-like component admixed to the depleted MORB mantle between about 15.8 and 20.7S

Samuel Niedermann; Wolfgang Bach; Jrg Erzinger

1997-01-01

369

Evaluation of argon ages and integrity of fluid-inclusion compositions: stepwise noble gas heating experiments on 1.87 Ga alunite from Tapajs Province, Brazil  

Microsoft Academic Search

Quantitative analyses are reported for active (N2, CH4, CO, CO2, H2, O2, HF, HCl, H2S, SO2) and noble (He, Ar, Ne) gases released by crushing and step heating of magmatic-hydrothermal alunite from the Tapajs gold province in Brazil. This is the oldest known alunite (40Ar\\/39Ar age of 1.87 Ga), and because it has undergone minimal postdepositional thermal or tectonic strain,

G. P. Landis; L. W. Snee; C. Juliani

2005-01-01

370

21 CFR 872.3060 - Noble metal alloy.  

Code of Federal Regulations, 2010 CFR

...metal alloy. (a) Identification . A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver, that is intended for use in the fabrication of cast or porcelain-fused-to-metal crown and...

2010-04-01

371

21 CFR 872.3060 - Noble metal alloy.  

Code of Federal Regulations, 2011 CFR

...metal alloy. (a) Identification . A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver, that is intended for use in the fabrication of cast or porcelain-fused-to-metal crown and...

2011-04-01

372

21 CFR 872.3060 - Noble metal alloy.  

Code of Federal Regulations, 2012 CFR

...metal alloy. (a) Identification . A noble metal alloy is a device composed primarily of noble metals, such as gold, palladium, platinum, or silver, that is intended for use in the fabrication of cast or porcelain-fused-to-metal crown and...

2012-04-01

373

Noble-metal-free plasmonic photocatalyst: hydrogen doped semiconductors  

PubMed Central

The unique capacity of localized surface plasmon resonance (LSPR) offers a new opportunity to overcome the limited efficiency of semiconductor photocatalyst. Here we unravel that LSPR, which usually occurs in noble metal nanoparticles, can be realized by hydrogen doping in noble-metal-free semiconductor using TiO2 as a model photocatalyst. Moreover, its LSPR is located in infrared region, which supplements that of noble metal whose LSPR is generally in the visible region, making it possible to extend the light response of photocatalyst to infrared region. The near field enhancement is shown to be comparable with that of noble-metal nanoparticles, indicating that highly enhanced light absorption rate can be expected. The present work can provide a key guideline for the creation of highly efficient noble-metal-free plasmonic photocatalysts and have a much wider impact in infrared bioimaging and spectroscopy where infrared LSPR is essential.

Ma, Xiangchao; Dai, Ying; Yu, Lin; Huang, Baibiao

2014-01-01

374

ANALYSIS OF PROTOCOL GASES  

EPA Science Inventory

In 1992, EPA's Atmospheric Research and Exposure Assessment Laboratory initiated a nationwide QA program on the suppliers of EPA Protocol Gases. he program has three goals: to increase the acceptance and use of Protocol Gases by the air monitoring community, to provide a QA check...

375

Diagnostics and modelling of noble gas atmospheric pressure dielectric barrier discharges in homogeneous or diverging electric fields  

NASA Astrophysics Data System (ADS)

We present experimental results of 'atmospheric pressure glow discharges' in two different electrode configurations, plane-plane and cylinder-plane. Although many of the phenomena we report here have been observed in different noble gases, we restrict this presentation primarily to the case of helium. Discharge diagnostics have been carried out using ultra-high speed imaging, and synchronous detection of light emission and current-voltage measurements, the former using a photomultiplier. The discharge physics is discussed with reference to recent work reported by the present authors and others.

Radu, I.; Bartnikas, R.; Wertheimer, M. R.

2005-02-01

376

Hyperpolarized noble gas magnetic resonance imaging of the animal lung: Approaches and applications  

NASA Astrophysics Data System (ADS)

Hyperpolarized noble gas (HNG) magnetic resonance (MR) imaging is a very promising noninvasive tool for the investigation of animal models of lung disease, particularly to follow longitudinal changes in lung function and anatomy without the accumulated radiation dose associated with x rays. The two most common noble gases for this purpose are 3He (helium 3) and 129Xe (xenon 129), the latter providing a cost-effective approach for clinical applications. Hyperpolarization is typically achieved using spin-exchange optical pumping techniques resulting in ~10 000-fold improvement in available magnetization compared to conventional Boltzmann polarizations. This substantial increase in polarization allows high spatial resolution (<1 mm) single-slice images of the lung to be obtained with excellent temporal resolution (<1 s). Complete three-dimensional images of the lungs with 1 mm slice thickness can be obtained within reasonable breath-hold intervals (<20 s). This article provides an overview of the current methods used in HNG MR imaging with an emphasis on ventilation studies in animals. Special MR hardware and software considerations are described in order to use the strong but nonrecoverable magnetization as efficiently as possible and avoid depolarization primarily by molecular oxygen. Several applications of HNG MR imaging are presented, including measurement of gross lung anatomy (e.g., airway diameters), microscopic anatomy (e.g., apparent diffusion coefficient), and a variety of functional parameters including dynamic ventilation, alveolar oxygen partial pressure, and xenon diffusing capacity.

Santyr, Giles E.; Lam, Wilfred W.; Parra-Robles, Juan M.; Taves, Timothy M.; Ouriadov, Alexei V.

2009-05-01

377

Development of Laser-Polarized Noble Gas Magnetic Resonance Imaging (MRI) Technology  

NASA Technical Reports Server (NTRS)

We are developing technology for laser-polarized noble gas nuclear magnetic resonance (NMR), with the aim of enabling it as a novel biomedical imaging tool for ground-based and eventually space-based application. This emerging multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI)-e.g., of lung ventilation, perfusion, and gas-exchange. In addition, laser-polarized noble gases (3He and 1BXe) do not require a large magnetic field for sensitive NMR detection, opening the door to practical MRI with novel, open-access magnet designs at very low magnetic fields (and hence in confined spaces). We are pursuing two specific aims in this technology development program. The first aim is to develop an open-access, low-field (less than 0.01 T) instrument for MRI studies of human gas inhalation as a function of subject orientation, and the second aim is to develop functional imaging of the lung using laser-polarized He-3 and Xe-129.

Walsworth, Ronald L.

2004-01-01

378

Noble-gas enrichment in vapour-growth diamonds and the origin of diamonds in ureilites  

NASA Astrophysics Data System (ADS)

Ureilites show high carbon contents comparable with those of CM chondrites1,2. One of the major questions about ureilites is why they contain large amounts of noble gases concentrated in carbon-rich veins3,4. Diamond is shown to be one of the noble-gas carriers, while graphite is gas-free5. We synthesized diamonds by chemical vapour deposition (CVD)6-8 from gaseous mixtures of H2 and CH4 including Ar, and examined the Ar trapped in diamond by mass spectrometry employing the stepwise heating technique. The partial pressure of 36Ar in the gaseous mixture during the synthesis of diamond was 5.310-6 atm. The content of 36Ar was about as great as 810-6 cm3 STP g-1 which was extracted at 2,000C. Meanwhile, the 36Ar concentration in graphite was much less than 5% of that in diamonds. These results suggest that diamonds in ureilites may have been directly formed from the solar nebula.

Fukunaga, Kazuya; Matsuda, Jun-Ichi; Nagao, Keisuke; Miyamoto, Masamichi; Ito, Keisuke

1987-07-01

379

Dating very old pore waters in impermeable rocks by noble gas isotopes  

SciTech Connect

The {sup 4}He, {sup 40}Ar, and {sup 136}Xe content dissolved in the pore water of sedimentary rock samples was measured on samples from borehole cores near the repository for nuclear waste in Morsleben, Germany. Due to the very low permeabilities of the rock formations, conventional groundwater sampling was almost impossible. Hence, the authors developed a new sampling method for noble gases in the pore water of freshly drilled rock cores. This method provides vertical noble gas profiles in high depth resolution, even in impermeable rocks. By application of the new technique quantitative age information of groundwater and pore water have been derived. The authors find palaeowaters from the last glaciation depleted in {delta}D and {delta}{sup 18}O with a {sup 4}He age of about 55 kyr. The high saline pore solutions below are at least 6 Mio years old. This has been concluded from the profiles of radiogenic {sup 4}He and {sup 40}Ar close to diffusion in steady-state and from xenon isotopes produced by spontaneous fission of {sup 238}U in the rocks. A {sup 4}He flux of 2 {center_dot} 10{sup {minus}7} cc STP/cm{sup 2} yr is derived from the profile, which is due to local {sup 4}He production within the investigated sediments.

Osenbrueck, K.; Lippmann, J.; Sonntag, C. [Univ. Heidelberg (Germany). Inst. fuer Umweltphysik] [Univ. Heidelberg (Germany). Inst. fuer Umweltphysik

1998-09-01

380

Noble Metal Nanoparticles Applications in Cancer  

PubMed Central

Nanotechnology has prompted new and improved materials for biomedical applications with particular emphasis in therapy and diagnostics. Special interest has been directed at providing enhanced molecular therapeutics for cancer, where conventional approaches do not effectively differentiate between cancerous and normal cells; that is, they lack specificity. This normally causes systemic toxicity and severe and adverse side effects with concomitant loss of quality of life. Because of their small size, nanoparticles can readily interact with biomolecules both at surface and inside cells, yielding better signals and target specificity for diagnostics and therapeutics. This way, a variety of nanoparticles with the possibility of diversified modification with biomolecules have been investigated for biomedical applications including their use in highly sensitive imaging assays, thermal ablation, and radiotherapy enhancement as well as drug and gene delivery and silencing. Here, we review the available noble metal nanoparticles for cancer therapy, with particular focus on those already being translated into clinical settings.

Conde, Joao; Doria, Goncalo; Baptista, Pedro

2012-01-01

381

Laser microprobe analyses of noble gas isotopes and halogens in fluid inclusions: Analyses of microstandards and synthetic inclusions in quartz  

USGS Publications Warehouse

Ar, Kr, Xe, Cl, Br, I, and K abundances and isotopic compositions have been measured in microscopic fluid inclusions in minerals by noble gas mass spectrometry following neutron irradiation and laser extraction. The laser microprobe noble gas mass spectrometric (LMNGMS) technique was quantified by use of microstandards, including air-filled capillary tubes, synthetic basalt glass grains, standard hornblende grains, and synthetic fluid inclusions in quartz. Common natural concentrations of halogens (Cl, Br, and I) and noble gases (Ar and Kr) in trapped groundwaters and hydrothermal fluids can be analyzed simultaneously by LMNGMS in as little as 10-11 L of inclusion fluid, with accuracy and precision to within 5-10% for element and isotope ratios. Multicomponent element and isotope correlations indicate contaminants or persistent reservoirs of excess Xe and/or unfractionated air in some synthetic and natural fluid inclusion samples. LMNGMS analyses of natural fluid inclusions using the methods and calibrations reported here may be used to obtain unique information on sources of fluids, sources of fluid salinity, mixing, boiling (or unmixing), and water-rock interactions in ancient fluid flow systems. ?? 1992.

Bohlke, J. K.; Irwin, J. J.

1992-01-01

382

Trapping Planetary Noble Gases During the Fischer-Tropsch-Type Synthesis of Organic Materials  

NASA Technical Reports Server (NTRS)

When hydrogen, nitrogen and CO arc exposed to amorphous iron silicate surfaces at temperatures between 500 - 900K, a carbonaceous coating forms via Fischer-Tropsch type reactions!, Under normal circumstances such a catalytic coating would impede or stop further reaction. However, we find that this coating is a better catalyst than the amorphous iron silicates that initiate these rcactions:u . The formation of a self-perpetuating catalytic coating on grain surfaces could explain the rich deposits of macromolecular carbon found in primitive meteorites and would imply that protostellar nebulae should be rich in organic materiaL Many more experiments are needed to understand this chemical system and its application to protostellar nebulae.

Nuth, Joseph A.; Johnson, N. M.; Meshik, A.

2010-01-01

383

Impact Event at the Permian-Triassic Boundary: Evidence from Extraterrestrial Noble Gases in Fullerenes  

NASA Astrophysics Data System (ADS)

The Permian-Triassic boundary (PTB) event, which occurred about 251.4 million years ago, is marked by the most severe mass extinction in the geologic record. Recent studies of some PTB sites indicate that the extinctions occurred very abruptly, consistent with a catastrophic, possibly extraterrestrial, cause. Fullerenes (C60 to C200) from sediments at the PTB contain trapped helium and argon with isotope ratios similar to the planetary component of carbonaceous chondrites. These data imply that an impact event (asteroidal or cometary) accompanied the extinction, as was the case for the Cretaceous-Tertiary extinction event about 65 million years ago.

Becker, Luann; Poreda, Robert J.; Hunt, Andrew G.; Bunch, Theodore E.; Rampino, Michael

2001-02-01

384

Submicron defects in rapidly solidified Type 304 stainless steel powders containing noble gases  

Microsoft Academic Search

The purpose of this work is to examine the defect microstructure of 304 SS powders processed by different atomization methods. The powders examined were processed by centrifugal atomization (CA) and vacuum gas atomization (VGA). In the CA process the molten droplets exiting from the spinning cup were convectively cooled with flowing helium. The VGA process involves pressurizing and mechanical mixing

J. C. Bae; T. F. Kelly; J. E. Flinn; R. N. Wright

1988-01-01

385

Noble gases in individual L chondritic micrometeorites preserved in an Ordovician limestone  

Microsoft Academic Search

We have measured the He and Ne concentrations and isotopic ratios of individual sediment-dispersed extraterrestrial chromite grains (63180?m in diameter) from an Ordovician limestone in southern Sweden. In the same sediment, many fossil meteorites were found and have been attributed to the L chondrite parent body breakup event ?470Ma ago. In this analysis of 37 individual extraterrestrial chromite grains of

M. M. M. Meier; B. Schmitz; H. Baur; R. Wieler

2010-01-01

386

Deep mantle derived noble gases in metamorphic microdiamonds from Kokchetav massif, Kazakhstan  

Microsoft Academic Search

Metamorphic diamonds from the Kokchetav massif, northern Kazakhstan are considered to be crystallized from a C-O-H fluid during ultra-high pressure metamorphism of metasedimentary rocks subducted to the depth of 190-280 km [1]. The microdiamonds have been known for their ``unprecedentedly'' high 3He\\/4He of 6E-4 associated with very high He content [2,3]. The high 4He concentrations have been well explained by

H. Sumino; L. Dobrzhinetskaya

2009-01-01

387

CO2 Well Gas, Noble Gases and the Origin of Volatiles in the Earth's Mantle  

Microsoft Academic Search

Neon isotopes provide a unique opportunity to distinguish between volatiles introduced into the mantle during the accretion of the Earth by equilibration between a magma ocean with a massive early atmosphere, or as a component trapped within accreting material. A massive early atmosphere would have a Solar Ne isotopic composition (20Ne\\/22Ne=13.8) while accreting material that has been irradiated by solar

C. J. Ballentine; B. Sherwood Lollar; B. Marty; M. Cassidy

2003-01-01