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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

Localized electrons in dense heavy noble gases  

Microsoft Academic Search

The paper addresses counterintuitive behavior of electrons injected into dense cryogenic media with negative scattering length a0. Instead of the expected polaronic effect (formation of density enhancement clusters) which should substantially reduce the electron mobility, an opposite picture is observed: with increasing |a0| (the trend taking place for inert gases with the growth of atomic number) and the medium density,

S. Nazin; V. Shikin

2009-01-01

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 (4×10-15 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

Noble gases in meteorites  

Microsoft Academic Search

The measurement of isotopic abundances of the noble gases in meteorites and other extraterrestrial samples became a large and active field during the past decade, especially within the last four years. The five stable noble gases proved to be excellent keys for unlocking the secrets of past physical events in the solar system and are used in studies of such

Donald D. Bogard

1971-01-01

5

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

6

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

NASA Astrophysics Data System (ADS)

A bulk sample and three density separates of the Martian orthopyroxenite ALH 84001 were studied with the objective of deciphering the noble gas (Xe, Kr, and Ar) and nitrogen components. The results clearly show the presence of a Martian atmospheric component which is characterized by xenon isotopic ratios very similar to those found in EET 79001,C. Trapped xenon and nitrogen in ALH 84001 are consistent with a two-component mixture of Chassigny type and EET 79001,C type components. In addition, xenon shows a small contribution from in situ fission from U-238 and also a Xe-129 excess due to in situ decay of live I-129 in high temperature fractions. The implications of the analysis results for the evolution of the Martian atmosphere are discussed

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

1997-12-01

7

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.

8

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

9

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

10

Measurements of Gas Amplification in Noble Gases  

NASA Astrophysics Data System (ADS)

Avalanche multiplication in noble gases with ethane and methane quenchers were measured in the ``gain" region of 10^3 - 10^5. The data provide future chamber designers with useful information concerning the effects of changes in pressure and voltage on the gain as well as absolute gain calculations from knowledge of the First Townsend Coefficient.

Wyatt, Julie

1999-11-01

11

EOSN: A TOUGH2 module for noble gases  

Microsoft Academic Search

We developed a new fluid property module for TOUGH2, called EOSN, to simulate transport of noble gases in the subsurface. Currently, users may select any of five different noble gases as well as CO2, two at a time. For the three gas components (air and two user-specified noble gases) in EOSN, the Henry's coefficients and the diffusivities in the gas

Chao Shan; Karsten Pruess

2003-01-01

12

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

NASA Astrophysics Data System (ADS)

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 ~14,400 to 160,000; 3He/4He of 50 to 4.5 RA), and exhibit values both higher and lower than the canonical mid-ocean ridge basalt range (4He/3He of 80,000 to 100,000; 3He/4He of 9 to 7 RA). Low 4He/3He ratios indicate a relatively undegassed mantle source that has preserved high 3He/(U+Th) over time, compared to the volatile-depleted MORB source. On the other hand, high 4He/3He ratios are attributed to the presence of recycled oceanic crust. Therefore, the occurrence of 4He/3He ratios both higher and lower than normal MORB along the SWIR provides a unique window into upper mantle heterogeneity. We have measured heavy noble gas (Ne, Ar, Xe) isotopic compositions in high- and low- 4He/3He glasses from the SWIR in order to investigate the nature and distribution of heterogeneities in the upper mantle, and to explore the implications for mantle structure and dynamics. Noble gas isotopes are sensitive indicators of degassing and recycling processes. 4He is produced by the radioactive decay of U and Th, while 3He is primordial. 21Ne is also produced via nuclear reactions in association with U and Th decay. Recycled crust is expected to develop strongly radiogenic He and nucleogenic Ne compositions over time. High 4He/3He ratios in SWIR glasses are paired with Ne more nucleogenic than N-MORB, consistent with mixing between recycled material and ambient upper mantle. On the other hand, high 4He/3He ocean island basalts from the Cook-Austral chain do not exhibit nucleogenic Ne compositions; in fact, Cook-Austral neon is less nucleogenic than N-MORB, indicating mixing of recycled crust with relatively undegassed mantle material (Parai et al., EPSL 2009). Our observations suggest a dual fate for oceanic crust subducted back into the mantle: some fraction of crust circulates within the volatile-depleted upper mantle, while some fraction is injected into a less degassed lower mantle. Volcanism at ocean islands may sample ancient recycled crust stored in the lower mantle, while mid-ocean ridges may tap crust residing in the upper mantle. If high 4He/3He ratios at the SWIR do reflect a greater proportion of recycled crust, then the occurrence of 129Xe/130Xe ratios up to ~7.3 in the SWIR basalts indicates that significant amounts of atmospheric Xe are not recycled back into the mantle. Alternately, high 4He/3He ratios may reflect the residue of an ancient depletion event, but this requires that the residue have (U+Th)/3He ratios higher than the normal MORB source (Hart et al., EPSL 2008).

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

2009-12-01

13

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

14

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

15

Sorption and desorption of radioactive noble gases in polycarbonates  

Microsoft Academic Search

The remarkable ability of some polycarbonates to absorb noble gases makes them an useful tool for measurements of radioactive noble gases. In this paper the kinetic of sorption and desorption processes is theoretically and experimentally studied. A theoretical model is proposed that considers diffusion and radioactive decay. Experimental results for 85Kr, 133Xe and 222Rn are presented. They include experimental determination

D. Pressyanov; K. Mitev; S. Georgiev; I. Dimitrova

2009-01-01

16

Sir William Ramsay and the noble gases.  

PubMed

Sir William Ramsay was one of the world's leading scientists at the end of the 19th century, and in a spectacular period of research between 1894 and 1898, he discovered five new elements. These were the noble gases, helium, neon, argon, krypton, and xenon; they added a whole new group to the Periodic Table of the elements, and provided the keystone to our understanding of the electronic structure of atoms, and the way those electrons bind the atoms together into molecules. For this work he was awarded the Nobel Prize in Chemistry in 1904, the first such prize to come to a British subject. He was also a man of great charm, a good linguist, and a composer and performer of music, poetry and song. This review will trace his career, describe his character and give and account of the chemistry which led to the award of the Nobel Prize. PMID:22574384

Davies, Alwyn G

2012-01-01

17

Partition of noble gases between olivine and basalt melt  

NASA Astrophysics Data System (ADS)

The distribution coefficients ( K i ) of noble gases were determined for synthesized olivine-basalt melt pairs. Seven samples (BH-series) were synthesized at 1370 ~ 1300°C under a one atmospheric pressure (~ 10 5 Pa) noble gas mixture, and four samples (HPP- and HPG-series) at 1360-1050°C at high pressures (0.2-1.5 GPa). The two different experiments gave consistent results with each other. Some BH-series olivine samples were apparently contaminated with gas-rich inclusions or the glass phase, and the effects of such interferences on the calculated distribution coefficients were evaluated. The possible ranges of the distribution coefficients of noble gases thus obtained are: K He 0.07, K Ne = 0.006-0.08, K Ar = 0.05-0.15, K Kr 0.15, and K Xe 0.3. These show remarkable features compared to solid element distribution coefficients: the distribution coefficients of noble gases are rather insensitive to, or even positively correlated with the atomic size of noble gases. The striking contrast between the partition of noble gases and that of solid elements may be attributed to the electrical neutrality of noble gases and the increasing electronic polarizability from He to Xe.

Hiyagon, H.; Ozima, M.

1986-09-01

18

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

19

REMOVAL OF TITAN'S ATMOSPHERIC NOBLE GASES BY THEIR SEQUESTRATION IN SURFACE CLATHRATES  

SciTech Connect

A striking feature of the atmosphere of Titan is that no heavy noble gases other than argon were detected by the Gas Chromatograph Mass Spectrometer aboard the Huygens probe during its descent to Titan's surface in 2005 January. Here we provide an explanation of the mysterious absence or rarity of these noble gases in Titan's atmosphere: the thermodynamic conditions prevailing at the surface-atmosphere interface of the satellite allow the formation of multiple guest clathrates that preferentially store some species, including all heavy noble gases, over others. The clean water ice needed for the formation of these clathrates could be delivered by successive episodes of cryovolcanic lavas that have been hypothesized to regularly cover the surface of Titan. The formation of clathrates in the porous lavas and their propensity for trapping Ar, Kr, and Xe would progressively remove these species from the atmosphere of Titan over the course of its history. In some circumstances, a global clathrate crust with an average thickness not exceeding a few meters could be sufficient on Titan for a complete removal of the heavy noble gases from the atmosphere.

Mousis, Olivier; Picaud, Sylvain [Universite de Franche-Comte, Institut UTINAM, CNRS/INSU, UMR 6213, Observatoire des Sciences de l'Univers de Besancon (France); Lunine, Jonathan I. [CRSR, Cornell University, Ithaca, NY 14853 (United States); Cordier, Daniel [Universite de Rennes 1, Institut de Physique de Rennes, CNRS, UMR 6251 (France); Mandt, Kathleen E. [Space Science and Engineering Division, Southwest Research Institute, San Antonio, TX 78228 (United States); Hunter Waite, J. Jr., E-mail: olivier.mousis@obs-besancon.fr

2011-10-10

20

The role of clathrate hydrates in cleaning the noble gases of Titan's atmosphere  

NASA Astrophysics Data System (ADS)

A striking feature of the atmosphere of Titan is that no heavy noble gases other than argon were detected by the Gas Chromatograph Mass Spectrometer (GCMS) aboard the Huygens probe during its descent to Titan's surface in January 2005. Here we provide an explanation of the mysterious absence or rarity of these noble gases in Titan's atmosphere: the thermodynamic conditions prevailing at the surface-atmosphere interface of the satellite allow the formation of multiple guest clathrates that preferentially store some species, including all heavy noble gases, over others. The clean water ice needed for formation of these clathrates could be delivered by successive episodes of cryovolcanic lavas that have been hypothesized to regularly cover the surface of Titan. The formation of clathrates in the porous lavas and their propensity for trapping Ar, Kr and Xe would progressively remove these species from the atmosphere of Titan over its history. In some circumstances, a global clathrate crust with an average thickness not exceeding a few meters could be sufficient on Titan for a complete removal of the heavy noble gases from the atmosphere.

Mousis, O.; Lunine, J. I.; Picaud, S.; Cordier, D.; Waite, J. H.; Mandt, K. E.

2011-10-01

21

Removal of Titan's Atmospheric Noble Gases by Their Sequestration in Surface Clathrates  

NASA Astrophysics Data System (ADS)

A striking feature of the atmosphere of Titan is that no heavy noble gases other than argon were detected by the Gas Chromatograph Mass Spectrometer aboard the Huygens probe during its descent to Titan's surface in 2005 January. Here we provide an explanation of the mysterious absence or rarity of these noble gases in Titan's atmosphere: the thermodynamic conditions prevailing at the surface-atmosphere interface of the satellite allow the formation of multiple guest clathrates that preferentially store some species, including all heavy noble gases, over others. The clean water ice needed for the formation of these clathrates could be delivered by successive episodes of cryovolcanic lavas that have been hypothesized to regularly cover the surface of Titan. The formation of clathrates in the porous lavas and their propensity for trapping Ar, Kr, and Xe would progressively remove these species from the atmosphere of Titan over the course of its history. In some circumstances, a global clathrate crust with an average thickness not exceeding a few meters could be sufficient on Titan for a complete removal of the heavy noble gases from the atmosphere.

Mousis, Olivier; Lunine, Jonathan I.; Picaud, Sylvain; Cordier, Daniel; Waite, J. Hunter, Jr.; Mandt, Kathleen E.

2011-10-01

22

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, D.F.

1986-07-01

23

Interlayer trapping of noble gases in insoluble organic matter of primitive meteorites  

NASA Astrophysics Data System (ADS)

Noble gases in primitive meteorites are trapped in a residue left after demineralization of bulk meteorite by HF and HCl. Most of the primordial Ar, Kr and Xe and small amounts of He and Ne are removed by oxidation of this acid-resistant residue, e.g. with HNO3. These gases, referred as P1, are trapped in a poorly characterized, presumably organic, phase labeled phase Q. In order to understand the siting of P1 noble gases, we have performed a solvation experiment on insoluble organic matter of Orgueil (CI). Pyridine was used because it presents an important swelling ratio of about 2 potentially able to change considerably the structure of phase Q without affecting the crystalline structure of nanodiamonds, chromite, spinel and metal alloys present in acid residue. Heavy noble gases are largely lost upon pyridine treatment at room temperature. However, the elemental pattern of the remaining Ar, Kr and Xe is not different from that of the starting acid residue, showing similar losses of all the heavy noble gases during solvation. Xenon stepwise heating data and deconvolution of different components based on isotopic ratios show that Xe-P1 is mainly affected by loss (? 60%), following by Xe-P3 (? 25%) and Xe-HL (? 12%). The xenon release is maximum at temperatures ? 1300 °C (? 70 80%) whereas only 23% is lost at 1600 °C and no further loss occurs at 2100 °C. These results suggest the existence of at least two substructures in phase Q, with Xe-P1 being trapped preferentially in the less retentive phase. As macromolecular organic matter is the only phase of acid residue sensitive to solvation, this study demonstrates the organic nature of phase Q. The behavior of heavy noble gases upon pyridine solvation supports interlayer trapping of these elements, probably within organic layers of aromatic moieties linked by short aliphatic chains.

Marrocchi, Yves; Derenne, Sylvie; Marty, Bernard; Robert, François

2005-08-01

24

Where do noble gases hide in space?  

Microsoft Academic Search

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

F. Pauzat; Y. Ellinger

2005-01-01

25

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 4.5±0.5 (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 (1.97±0.15.10-3) while the I/Cl molar ratio varies significantly by up to one order of magnitude, ranging from 1.2±0.3.10-6 to 9.9±0.8.10-6. 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

26

Medical Imaging with Laser Polarized Noble Gases  

NASA Astrophysics Data System (ADS)

In the past five years, techniques of magnetic resonance imaging with laser polarized ^3He and ^129Xe have emerged along with the promise of entirely new ways to use NMR information from gas in the lungs and of xenon dissolved in tissue. This marriage of laser/optical physics and medical imaging has the potential to provide new ways to study and map function in the brain, measure physiological parameters, and diagnose diseases of the lungs, heart, and brain. Static and dynamic images of the lung air spaces already provide much greater spatial resolution than standard nuclear medicine techniques, and preliminary clinical studies of various pulmonary diseases are underway. Imaging of ^129Xe dissolved in tissue of the vital organs has potential applications to medicine as well as basic research in physiology and neuroscience. The use of ^129Xe as a magnetic tracer provides a measure of blood flow to several types of tissue in the brain and can be used to map and study neural function. Though a great deal of AMO physics research is still needed to advance noble gas polarization techniques, the rapid emergence of noble gas imaging was made possible in large part by advances motivated by basic research in nuclear and high energy physics. I will describe this remarkable new field of noble gas imaging, its beginnings in fundamental physics research, and AMO physics research that will continue to advance the field.

Chupp, Timothy

2000-06-01

27

EOSN—a new TOUGH2 module for simulating transport of noble gases in the subsurface  

Microsoft Academic Search

Noble gases widely exist in nature, and except for radon, they are stable. Modern techniques can detect noble gases to relatively low concentrations and with great precision. These factors suggest that noble gases can be useful tracers for subsurface characterization. Their applications, however, require an appropriate transport model for data analyses. A new fluid property module, EOSN, was developed for

Chao Shan; Karsten Pruess

2004-01-01

28

EOSN - A new TOUGH2 module for simulating transport of noble gases in the subsurface  

Microsoft Academic Search

Noble gases widely exist in nature, and except for radon, they are stable. Modern techniques can detect noble gases to relatively low concentrations and with great precision. These factors suggest that noble gases can be useful tracers for subsurface characterization. Their applications, however, require an appropriate transport model for data analyses. A new fluid property module, EOSN, was developed for

Chao Shan; Karsten Pruess

2003-01-01

29

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.

30

Explosively Generated Plasmas in Noble Gases  

NASA Astrophysics Data System (ADS)

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 waves. The shock wave in the gas is generated by an explosive located at one end of a guide tube filled with a noble gas. The detonation produces a shock wave strong enough to ionize the gas. Spectral line emission profiles, recorded with a streak emission spectroscopy system, are used to ascertain neutral and ionized gas properties. The electric and magnetic fields are measured by electrostatic probes and magnetic induction coils which permit the measurement of the temperature, density, and electric potential of the non-ideal plasma; as well as the flow of net electric charges respectively. The results demonstrate there is a mixing of the detonation products and the noble gas and that there is a pulse of electrons that travel ahead of the shock wave as it travels down the guide tube.

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

2007-11-01

31

Nitrogen and light noble gases in Parsa enstatite chondrite  

NASA Astrophysics Data System (ADS)

Solar gases have been recently reported in Parsa, an EH3 chondrite. In an effort to check whether solar gases are uniformly distributed throughout Parsa or they are located in specific phases, we analyzed two additional samples of bulk Parsa and one aubritic nodule for N and noble gases. Nitrogen studies are intended for the understanding of the nitrogen components distribution in E-chondrites. The N-systematics of the nodule are entirely different from the bulk samples. The higher N contents in this nodule, as well as its complex delta15N structure, as compared to the normal aubrites, is suggestive that the nodule is not a genuine aubrite.

Murty, S. V. S.

1993-03-01

32

Noble gases as tools for subsurface monitoring of CO 2 leakage  

Microsoft Academic Search

We are developing the use of noble gases as tools to survey the integrity of CO2 geological storages. The advantage of using noble gases stems from their chemical inactivity which does not delay them when they migrate in leaking pathways. Using the aquifers located above the CO2 deep storages as leak integrators and monitoring them for noble gas contents could

Stéphane Lafortune; Manuel Moreira; Pierre Agrinier; Alain Bonneville; Héléne Schneider; Hubert Catalette

2009-01-01

33

Cosmogenic radionuclides and noble gases in the Wethersfield (1982) chondrite  

SciTech Connect

The Wethersfield (1982) chondrite was assayed for a suite of cosmogenic radionuclides shortly after fall. Data are reported for Be-7, Na-22, All-26, Sc-46, V-48, Cr-51, Mn-54, Co-56, Co-57, and Co-60. A comparison is made with predicted results based on a scaling to the Deep River Neutron Monitor. Noble gases were also assayed in a subsample. The cosmic-ray-exposure age is estimated to be 45 Myr. 9 references.

Evans, J.C.; Reeves, J.H.; Bogard, D.D.

1986-09-01

34

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

35

Experiments on thermal release of implanted noble gases from minerals and their implications for noble gases in lunar soil grains  

NASA Astrophysics Data System (ADS)

Experiments on ion implantation were performed in order to study the release mechanisms of solar particles from lunar soil grains. Helium, neon, and argon ions were implanted into olivine and ilmenite. The release temperatures of noble gases were investigated by heating samples stepwise; the results show that they depend on irradiation energy and dose. We conclude that the release temperature is related to the size of bubbles in which noble gases are trapped: noble gases in small and large bubbles are released at 400-600 C and 800-1200 C, respectively. In Ne and Ar implantation experiments into olivine, a component was released during recrystallization of amorphized surfaces. Based on these experimental results, we suggest that components released from lunar ilmenite grains at different temperatures would correspond to solar particles of different energies. We also suggest that He and Ne of solar wind energy (about 1 keV/amu) should be retained in lunar ilmenite grains, while they should be lost from olivine grains.

Futagami, T.; Ozima, M.; Nagai, S.; Aoki, Y.

1993-07-01

36

Nitrogen and Noble Gases in Mineral Separates from Zagami  

NASA Astrophysics Data System (ADS)

Isotopic compositions of nitrogen and noble gases have played a key role in understanding SNC meteorites and Mars. For example nitrogen and argon data from the glass of EET 79001 were one of the convincing evidences that linked these meteorites to Mars. Similarly, the observation of components with largely different isotopic compositions (of both nitrogen and noble gases in these meteorites has led to the realization that the martian atmosphere (as measured by Viking) is quite different from the martian interior (as pictured from data from these meteorites). But at the same time we have not yet been able to clearly define the (interior) mantle end member and reduce the uncertainties presented by the Viking data for the martian atmosphere. Similarly we do not know for sure the Ne-20/Ne-22 signature of Mars. It is clear that many of these ambiguities as to the indigenous martian components result from interferences from cosmogenic contributions and terrestrial contamination, which are impossible to avoid. But they can be minimized by step temperature heating, and selection of mineral phases rather than bulk samples. We have initiated a simultaneous nitrogen and noble gas isotopic study of mineral separates and a few bulk samples from martian meteorites with the newly set up experimental facility at Mainz. Here we report data for maskelynite and pyroxene separates from Zagami.

Schwenzer, S. P.; Mohapatra, R. K.; Herrmann, S.; Ott, U.

2002-01-01

37

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

Microsoft Academic Search

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

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

1993-01-01

38

The History of Planetary Degassing as Recorded by Noble Gases  

NASA Astrophysics Data System (ADS)

Noble gases provide unique clues to the structure of the Earth and the degassing of volatiles into the atmosphere. Since the noble gases are highly depleted in the Earth, their isotopic compositions are prone to substantial changes due to radiogenic additions, even from scarce parent elements and low-yield nuclear processes. Therefore, noble gas isotopic signatures of major reservoirs reflect planetary differentiation processes that generate fractionations between these volatiles and parent elements. These signatures can be used to construct planetary degassing histories that have relevance to the degassing of a variety of chemical species as well.It has long been recognized that the atmosphere is not simply a remnant of the volatiles that surrounded the forming Earth with the composition of the early solar nebula. It was also commonly thought that the atmosphere and oceans were derived from degassing of the solid Earth over time (Brown, 1949; Suess, 1949; Rubey, 1951). Subsequent improved understanding of the processes of planet formation, however, suggests that substantial volatile inventories could also have been added directly to the atmosphere. The characteristics of the atmosphere therefore reflect the acquisition of volatiles by the solid Earth during formation (see Pepin and Porcelli, 2002; Chapter 4.12), as well as the history of degassing from the mantle. The precise connection between volatiles now emanating from the Earth and the long-term evolution of the atmosphere are key subjects of modeling efforts, and are discussed below.Major advances in understanding the behavior of terrestrial volatiles have been made based upon observations on the characteristics of noble gases that remain within the Earth. Various models have been constructed that define different components and reservoirs in the planetary interior, how materials are exchanged between them, and how the noble gases are progressively transferred to the atmosphere (see Chapter 2.06). While there remain many uncertainties, an overall process of planetary degassing can be discerned. The present chapter discusses the constraints provided by the noble gases and how these relate to the degassing of the volatile molecules formed from nitrogen, carbon, and hydrogen (see also Chapter 3.04). The evolution of particular atmospheric molecular species, such as CO2, that are controlled by interaction with other crustal reservoirs and which reflect surface chemical conditions, are primarily discussed elsewhere (Chapter 8.09).Noble gases provide the most detailed constraints on planetary degassing. A description of the available noble gas data that must be incorporated into any Earth degassing history is provided first in Section 4.11.2, and the constraints on the total extent of degassing of the terrestrial interior are provided in Section 4.11.3. Noble gas degassing models that have been used to describe and calculate degassing histories of both the mantle ( Section 4.11.4) and the crust ( Section 4.11.5) are then presented. These discussions then provide the context for an evaluation of major volatile cycles in the Earth ( Section 4.11.6), and speculations about the degassing of the other terrestrial planets ( Section 4.11.7), Mars and Venus, that are obviously based on much more limited data. The processes controlling mantle degassing are clearly related to the structure of the mantle, as discussed in Section 4.11.4. Further descriptions of mantle noble gas reservoirs and transport processes based upon multi-tracer variations in mantle-derived materials are provided in Chapter 2.06. An important aspect is the origin of planetary volatiles and whether initial incorporation was into the solid Earth or directly to the atmosphere; these issues are discussed in detail in Chapter 4.12. Basic noble gas elemental and isotopic characteristics are given in Ozima and Podosek (2001) and Porcelli et al. (2002). The major nuclear processes that produce noble gases within the solid Earth, and the half-lives of the major parental nuclides, are given in Table 1. Table 1. Major

Porcelli, D.; Turekian, K. K.

2003-12-01

39

Heterogeneous distribution of solar and cosmogenic noble gases in CM chondrites and implications for the formation of CM parent bodies  

NASA Astrophysics Data System (ADS)

Distribution of solar, cosmogenic, and primordial noble gases in thin slices of Murchison, Murray, and Nogoya CM carbonaceous chondrites was determined by the laser microprobe analysis so as to put some constraints on the parent-body processes in the CM chondrite formation. The main lithological units of the three meteorite slices were located by electron microscope observations and classified into clastic matrix and clasts of primary accretionary rocks (PARs) based on the classification scheme of texture of CM chondrites. All sample slices contain both clastic matrix and PARs. Clastic matrix shows a comminuted texture formed by fragmentation and mechanical mixing of rocks due to impacts, whereas PARs preserve the original textures prior to the mechanical disruption. Solar-type noble gases are detected in all sample slices. They are located preferentially in clastic matrix. The distribution of solar gases is similar to that in ordinary chondrites where these gases reside in clastic dark portions of these meteorites. The heterogeneous distribution of solar gases in CM chondrites suggests that these gases were acquired not in a nebular accretion process but in parent body processes. Solar energetic particles (SEP) are predominant in CM chondrites. The low abundance of low energy solar wind (SW) component relative to SEP suggests preferential loss of SW from minerals comprising the clastic matrix, due to aqueous alteration in the parent bodies. Cosmogenic noble gases are also enriched in some portions in clastic matrix, indicating that some parts of clastic matrix were exposed to solar and galactic cosmic rays prior to the final consolidation of the CM parent bodies. Primordial noble gases are rich in fine-grained rims around chondrules in all three meteorites. However, average concentrations of heavy primordial gases in the rims differ among meteorites and correlate inversely to the degree of aqueous alteration that the meteorites have experienced. This appears to have been caused by aqueous alteration reactions between fluids and carbonaceous carrier phases of noble gases.

Nakamura, Tomoki; Nagao, Keisuke; Metzler, Knut; Takaoka, Nobuo

1999-01-01

40

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

41

Excited state positronium collisions with the noble gases  

NASA Astrophysics Data System (ADS)

Calculations of the discrete positronium (Ps) transition Ps(2s) ? Ps(2p) in collisions with the ground state noble gases helium, argon and xenon are presented at total and single differential levels. For collisions where the target atom is not excited or ionized the impulse approximation (IA) is used. For collisions where the target is excited or ionized the first Born approximation (FBA) is used. For this latter case the Hartley Walters approximation is used to sum over all possible final atom states.

Starrett, C.; Walters, H. R. J.

2008-07-01

42

Using Noble Gases to Identify Temperature and Amount Effects in Stable Isotope Records  

NASA Astrophysics Data System (ADS)

The interpretation of stable isotope records from many climate archives suffers from the difficulty of separating the various effects that influence the isotopic signature. This contribution evaluates the potential of dissolved noble gases in water as a complementary proxy for temperature (and in some cases precipitation), which is accessible in climate archives containing liquid water. The noble gas thermometer is based on the temperature dependence of noble gas solubilities in water and has primarily been applied to groundwater. Aquifers are no ideal paleoclimate archives in terms of resolution and age control, but provide the unique opportunity to relate stable isotope data to absolute noble gas temperatures (NGTs). In addition, the so-called excess air component in groundwater is increasingly being used as a proxy for precipitation and can be related to the amount effect in stable isotope data. In recent groundwater paleoclimate studies from regions affected by the Asian monsoon, noble gas data enabled a separation of temperature and amount effects in the stable isotope records. Although in principle this approach is rather straightforward, difficulties arise due to additional effects influencing both the stable isotopes and noble gases in groundwater, such as changes in vegetation cover and continentality of the sites and the global ice volume effect. In recent groundwater of East China affected by heavy exploitation, non-climatic effects on the stable isotope signature have also been detected. In Holocene groundwater from Northwest India, a covariation of the climate proxies stable isotopes and excess air has been found. A group of early to mid Holocene samples depleted in stable isotopes and enriched in excess air indicates a phase of strong monsoon during the Holocene climate optimum. Both tracers indicate a drying trend in the second half of the Holocene, followed by more humid conditions in the youngest part of the record. A temporary rise of NGT in the dry late Holocene phase may reflect a change in the soil temperature - air temperature relationship. Recent developments aim at expanding the use of NGTs to other archives than groundwater, such as fluid inclusions in speleothems and sediment pore waters. Although presently no complete data sets from such archives exist, the potential of noble gases in these new archives is promising, in particular with regard to complementing stable isotope data.

Aeschbach-Hertig, W.; Wieser, M.

2011-12-01

43

Noble gas systematics of the Réunion mantle plume source and the origin of primordial noble gases in Earth's mantle  

NASA Astrophysics Data System (ADS)

New noble gas data of ultramafic xenoliths from Réunion Island, Indian Ocean, further constrain the characteristics of primordial and radiogenic noble gases in Earth's 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 Réunion mantle source can be constrained to range between 8000 and 12?000, significant 129Xe and fission Xe excess are present. Regarding the relative contribution of primordial and radiogenic rare gas nuclides, the Réunion mantle source is intermediate between Loihi- and MORB-type reservoirs. This confirms the compositional diversity of plume sources recognized in other radioisotope systematics. Another major result of this study is the identification of the same basic primordial component previously found for the Hawaiian and Icelandic mantle plumes and the MORB reservoir. It is a hybrid of solar-type He and Ne, and 'atmosphere-like' or 'planetary' Ar, Kr, Xe (Science 288 (2000) 1036). 20Ne/ 22Ne ratios extend to maximum values close to 12.5 (Ne-B), which is the typical signature of solar neon implanted as solar corpuscular radiation. This suggests that Earth's solar-type noble gas inventory was acquired by small (less than km-sized) precursor planetesimals that were irradiated by an active early sun in the accretion disk after nebular gas dissipation, or, alternatively, that planetesimals incorporated constituents irradiated in transparent regions of the solar nebula. Previously, such an early irradiation scenario was suggested for carbonaceous chondrites which follow common volatile depletion trends in the sequence CI-CM-CV-Earth. In turn, CV chondrites closely match Earth's mantle composition in 20Ne/ 22Ne, 36Ar/ 22Ne and 36Ar/ 38Ar. This indicates that mantle Ar could well be a planetary component inherited from precursor planetesimals. However, a corresponding conclusion for mantle Kr and Xe is less convincing yet, but this may be just due to the lack of appropriate 'meteoritic' building blocks matching terrestrial composition. Alternatively, heavy noble gases in Earth's mantle could be due to admixing of severely fractionated air, but this effect must have affected all mantle sources to a very similar extent, e.g. by global subduction before the last homogenization of the mantle reservoirs.

Trieloff, Mario; Kunz, Joachim; Allègre, Claude J.

2002-06-01

44

Microdistribution of primordial noble gases in CM chondrites determined by in situ laser microprobe analysis: Decipherment of nebular processes  

NASA Astrophysics Data System (ADS)

In situ noble gas analyses using a laser microprobe with a beam diameter of 50-100 ?m were performed on thin slices of Murchison and Yamato (Y-) 791198 CM carbonaceous chondrites in order to see microdistribution of primordial noble gases. Petrographic observations prior to noble-gas analyses showed that the two meteorite slices are entirely composed of chondrules, PCPs (poorly characterized phases) and other chondritic components that are rimmed by layers of fine-grained dust. Based on an existing classification scheme for texture of CM chondrites, the two samples are classified as primary accretionary rocks (PARs). The noble gas analyses showed that primordial noble gases are rich in the fine-grained rims around chondrules in the two meteorite slices. This suggests that large amounts of carrier phases of the primordial noble gases in CM chondrites are located in these rims which seem to have accreted on the surfaces of chondrules prior to the formation of the meteorite parent bodies. Rims on different chondrules within a given meteorite showed similar concentrations of heavy primordial noble gases, suggesting that phase Q is distributed homogeneously in the rims and possibly in the nebular region where the chondrules had acquired their dust rims. ( 20Ne) diamond/( 20Ne) Q ratios are relatively constant among rims in a given meteorite, indicative of homogeneous mixing of interstellar diamonds and phase Q on a 10 ?g scale. One location in a rim around a chondrule in the Murchison sample showed an enrichment of 22Ne, which suggests presence of carrier phases of Ne-E in the rim. A stepped heating analysis of a chip of Y-791198 was carried out to characterize the noble gases of bulk PAR. Abundances of primordial noble gases are only ˜50% of those of rims around chondrules, consistent with the relative abundances of gas-rich fine-grained material and gas-poor chondrules and inclusions in PAR. Solar gases were not detected, which implies that PARs, the primitive CM bodies, had grown to at least centimeter size in a dense solar nebula which shielded these objects from direct exposure to solar wind.

Nakamura, Tomoki; Nagao, Keisuke; Takaoka, Nobuo

1999-01-01

45

Permeability of noble gases through Kapton, butyl, nylon, and “Silver Shield”  

NASA Astrophysics Data System (ADS)

Noble gas permeabilities and diffusivities of Kapton, butyl, nylon, and “Silver Shield” are measured at temperatures between 22 and 115?C. The breakthrough times and solubilities at 22?C are also determined. The relationship of the room temperature permeabilities to the noble gas atomic radii is used to estimate radon permeability for each material studied. For the noble gases tested, Kapton and Silver Shield have the lowest permeabilities and diffusivities, followed by nylon and butyl, respectively.

Schowalter, Steven J.; Connolly, Colin B.; Doyle, John M.

2010-04-01

46

Noble gases in Mars atmosphere: new precise analysis with Paloma  

NASA Astrophysics Data System (ADS)

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, we do not know the isotopic composition of helium, and only very poorly that of Ne, Kr and Xe. In planetary science, it is fundamental to have a good knowledge of the atmosphere because this serves as a reference for all further studies of volatiles. In addition, part of our present knowledge of Mars atmosphere is based on the SNC meteorites, and again points to important differences between the atmospheres of Earth and Mars. For example the 129Xe/132Xe ratio of martian atmosphere would be twice that of terrestrial air and the 36Ar/38Ar ratio strongly different from the terrestrial or solar value. There is a need for confirming that the atmospheric components found in SNC meteorites actually represents the atmosphere of Mars, or to determine how different they are. Paloma is an instrument designed to generate elemental and isotopic data for He, Ne, Ar, Kr and Xe (and other gases) using a mass spectrometer with a purification and separation line. Gas purification and separation did not exist on the Vicking instrument. Because Paloma includes purification and separation, we expect strong improvement in precision. Ne, Ar and Xe isotope ratios should be obtained with an accuracy of better than 1%. Determination of the presently unknown ^3He/^4He ratio is also awaited from this experiment. Knowledge of noble gas isotopes in Mars atmosphere will allow some insight into major planetary processes such as degassing (^3He/^4He, 40Ar/36Ar, 129Xe/130Xe, 136Xe/130Xe), gravitational escape to space (^3He/^4He, 20Ne/22Ne), hydrodynamic escape and/or impact erosion of the atmosphere (20Ne/22Ne, 21Ne/22Ne, 38Ar/36Ar, Xe isotopes), input of solar wind and galactic comic rays (^3He/^4He, 20Ne/22Ne, 21Ne/22Ne). Comparison with the Earth may also shed light on long standing problems such as the large isotopic mass fractionation of the Xe isotopes and the so-called missing xenon problem. Possible variations of Kr and Xe abundances due to adsorption phenomena related to the climatic cycle will be searched for by measuring along at least one martian year.

Sarda, Ph.; Paloma Team

2003-04-01

47

Noble gases from solar energetic particles revealed by closed system stepwise etching of lunar soil minerals  

Microsoft Academic Search

He, Ne, and Ar abundances and isotopic ratios in plagioclase and pyroxene separates from lunar soils were determined using a closed system stepwise etching technique. This method of noble gas release allows one to separate solar wind (SW) noble gases from those implanted as solar energetic particles (SEP). The major part of SEP-Ne possibly originates from solar \\

R. Wieler; H. Baur; P. Signer

1986-01-01

48

Atom-atom excitation and ionization in shock waves of the noble gases  

Microsoft Academic Search

Rate coefficients for electron production in the relaxation zone behind the shock front in the noble gases have been calculated on the basis of a simplified model using generalized cross sections for atom-atom excitation and ionization of noble gas atoms.

H. W. Drawin; F. Emard

1973-01-01

49

Experimental Determination of the Partitioning Behavior of Noble Gases Between Carbonate and Silicate Liquids  

NASA Astrophysics Data System (ADS)

Carbonatitic melts have been identified in the earth’s upper mantle and experimental evidence suggests that such melts are stable at mantle conditions. Due to high carbonatite/silicate partition coefficients for certain trace elements, and due to the low melting points, low viscosities and low dihedral angles of carbonatite liquids, these liquids play a significant role in trace element fractionation in the mantle. However, the solubilities of the noble gases in carbonatitic liquids are poorly constrained although initial data at low pressure (1 bar) surprisingly suggest that the noble gases are poorly soluble in carbonatite liquids [1]. Partitioning of noble gases relative to the parents of radiogenic noble gases - primarily U, Th and K - has consequences for the isotopic evolution of mantle noble gases, consequently determination of noble gas solubilities in carbonatite phases is of extreme interest for mantle geodynamics. Two-liquid experimental charges consisting of nephelenite and Na2CO3 were synthesized at 1145 C and pressures between 0.6 and 2.5 GPa in sealed Au-Pd capsules in a piston cylinder apparatus. The experimental runs were c. 12h in duration and the charges were quenched at >200 C min-1 to form two immiscibly separated glasses phases. The nephelenite glass starting material had been saturated with a noble gas mixture (0.5 He, 0.02 Ne, 0.48 Ar) prior to synthesis. This procedure introduced noble gases without creating a free gas phase. The noble gases (He and Ar only) were measured in 3 stages: 1) the capsule was pierced under vacuum and the ‘free gas’ residing in the capsule pore space was analysed; 2) the entire capsule was heated to 250 C and the gases liberated were analysed and 3) the nephelenite glass was melting by a CO2 laser and the gases liberated analysed. The first stage of the analysis was to measure any noble gases (principally He) that may have diffused out of the carbonatite during the quench or between the period (of a few weeks) between quench and analysis. The second stage was designed to extract noble gases by thermal decarbonation of the carbonate glass. The metal of the capsule itself was also measured, but this never contained any noble gas above blank levels. Our preliminary results show that the noble gases do not preferentially partition into carbonate liquids compared to silicate liquids: DHe(carbonate/silicate)=0.3-1.4 and DAr(carbonate/silicate)=0.15-0.17 (at 1 GPa) In a two phase carbonate - silicate system, the noble gases will essentially reside in the silicate portion of the system (particularly given that carbonatite liquids will represent a small volume fraction of the two phase magma). This partitioning behavior could nevertheless separate - decouple - noble gas isotope systematics from lithophile isotopes (Sr, Nd, Pb etc) as a significant fraction of these elements could partition into the carbonate phase while noble gases remain in the silicate portion of the magma. Further work investigating pressure, temperature and compositional effects on the noble gas partition coefficients is planned. References 1. Burnard, P., Toplis, M. J. and Medynski, S. (2010) Geochim. Cosmochim. Acta 74: 1672-1683.

Burnard, P.; Koga, K. T.

2010-12-01

50

Double ionization of noble gases by positron impact  

NASA Astrophysics Data System (ADS)

The cross sections for double ionization and the ratios of double to single ionization, including Ps formation for Ne, Ar, Kr, and Xe are presented from threshold to 100 eV. Within the energy region 6.8 eV below the second ionization potential, i.e., the second Ore gap, we find Ne to have a double-ionization cross section indistinguishable from zero, which is consistent with prior measurements. However, the total double-ionization cross sections for Ar, Kr, and Xe just below the thresholds for direct double ionization are around 7-24 % of the maximum cross-section value for each atom, all of which are of the order of 10-21 m2 and occur around 70-90 eV. In contrast to what has previously been found for He and Ne, this is direct evidence of a significant amount of transfer ionization for the three heavier noble gases in the second Ore gap, which is consistent with previous measurements for Ar and Xe.

Moxom, J.; Schrader, D. M.; Laricchia, G.; Xu, Jun; Hulett, L. D.

1999-10-01

51

Noble gases on metal surfaces: Insights on adsorption site preference  

SciTech Connect

We use a nonlocal van der Waals density functional (vdW-DF) approach to reexamine the problem of why noble gases are experimentally observed to adsorb on low-coordination atop sites rather than on high-coordination hollow sites for several different metal surfaces. Previous calculations using density functional theory (DFT) within the local density approximation (LDA) ascribed the site preference to reduced Pauli repulsion at atop sites, largely due to reduced exchange repulsion within LDA-DFT. In contrast, our vdW-DF calculations show that site preference is not due to differences in the exchange repulsion at all, but rather the result of a delicate balance between the electrostatic and kinetic energies; surprisingly, exchange-correlation energies play a negligible role in determining site preference. In contrast to previous calculations, we find that experimental results cannot be explained in terms of binding energy differences between atop and hollow sites. Instead, we show that the hollow sites are transition states rather than minima on the two-dimensional potential energy surface, and therefore not likely to be observed in experiments. This phenomenon is quite general, holding for close-packed and non-close-packed metal surfaces. We show that inclusion of nonlocal 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, W. A.; Johnson, J. Karl

2011-12-19

52

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

53

Noble Gases in Stratospheric Dust Particles: Confirmation of Extraterrestrial Origin  

Microsoft Academic Search

Noble gas elemental and isotopic ratios were measured in a group of 13 ``chondritic'' stratospheric dust particles. Neon and argon are present in ``solar'' proportions; xenon appears to be dominated by contributions from ``planetary'' sources. The apparent xenon concentration is higher than that measured in any bulk meteorite, approaching the concentration found in the noble gas-rich, acid-insoluble residues from carbonaceous

B. Hudson; G. J. Flynn; P. Fraundorf; C. M. Hohenberg; J. Shirck

1981-01-01

54

Provision of noble gases to Venus atmosphere from comets and volcanoes: constraints from Venus Express data  

NASA Astrophysics Data System (ADS)

In light of new data from Venus Express providing more detailed profiles of the variation in concentration of major and minor constituents with depth in Venus' atmosphere, we readdress the issue of the source of noble gases and minor constituent volatiles in Venus' atmosphere. We re-examine two hypotheses that have already been proposed for the sources of the noble gases: cometary impact and volcanic activity. In order to test the plausibility of the first source, we collect from the literature and analyse data (of both comet and atmosphere composition) from many studies including those that utilise recent spacecraft missions that have sampled comets directly, such as Stardust and Deep Impact. Where data is unavailable for some noble gas concentrations of comets, we estimate the likely concentrations inferred from the noble gas data that is available. For the volcanic hypothesis, we model the delivery of noble gases through volcanism and estimate the required rate of volcanic activity to produce the near-surface abundances of noble gases and other constituents as observed by instruments on board Venus Express. For both sources, we find the upper limit on the required rate of source activity assuming that only one of the sources is active. We envisage that the most likely situation in reality is a combination of the two sources, with the proportion of delivery from each source being between the two calculated extremes. The results could have implications for comet formation because we test whether the noble gas abundances in Venus' atmosphere are consistent with the noble gases of comets condensing at very low temperatures, or else being trapped as clathrates, or else inconsistent with either hypothesis, in which case comets would probably not have been a major source of gases for Venus. The calculated upper limit on the rate of volcanic activity may have significant implications for the geological evolution of the planet.

Bargery, A. S.; Tobie, G.; Sotin, C.; Choblet, G.; Le Mouélic, S.

2009-04-01

55

Fullerenes, Noble Gases and the Flux of Extraterrestrial Debris to  

NASA Astrophysics Data System (ADS)

The discovery of fullerenes in deposits associated with two separate impact events involving a large bolide with the Earth suggests that these carbon (C) molecules may also be an indicator of extraterrestrial (ET) events over geologic time. Fullerenes were detected in carbon-rich breccias (Onaping Fm.) associated with the 1.85 byr Sudbury Crater (Becker et al., Science 265, 1994) and in clay sediments within the 65 myr old Cretaceous/Tertiary (K/T) boundary (Heymann et al., Science 265, 1994). To determine the origin of the Sudbury fullerenes, we searched for noble gases trapped inside the fullerene molecules (Saunders et al., Science 259, 1993). The Sudbury fullerenes contain trapped 3He/4He ratios (~5.5 times 10^{-4}) similar to those found in meteorites and some interplanetary dust particles (Becker et al., Science 272, 1996). Preliminary measurements of He in a continental K/T fullerene residue from Raton Basin (Colorado) revealed ^3He/^4He ratios some 100 times above air. A marine K/T residue from Stevns Klint, (Denmark) revealed ^3He/^4He ratios several thousand times above air in the high temperature fraction! We attribute the anomalously high ^3He/^4He ratios and high ^3He concentration in Stevns Klint to the abundance of higher fullerenes in the residue. The high ^3He/^4He ratio in the K/T fullerenes suggests that they were present in the bolide and somehow survived the impact event. Confirmation of these results could have broad implications concerning the importance of exogenous delivery in providing carbon, volatiles and perhaps other organics to the early Earth's crustal reservoir.

Becker, Luann; Poreda, Robert; Bunch, Ted

56

Chemical reactions occurring during pyrolysis of presolar diamonds and release patterns of light nitrogen and noble gases  

Microsoft Academic Search

It has long been known that release of noble gases from Cdelta diamonds is not a pure diffusion process but is accompanied by the release of chemically active gases that suggest that chemical reactions occur between coexisting phases of the sample and its environment. Therefore the release temperatures of noble gases depend on sample purity; for the purest sample of

A. B. Verchovsky; C. T. Pillinger

1994-01-01

57

EOSN - A new TOUGH2 module for simulating transport of noble gases in the subsurface  

SciTech Connect

Noble gases widely exist in nature, and except for radon, they are stable. Modern techniques can detect noble gases to relatively low concentrations and with great precision. These factors suggest that noble gases can be useful tracers for subsurface characterization. Their applications, however, require an appropriate transport model for data analyses. A new fluid property module, EOSN, was developed for TOUGH2 to simulate transport of noble gases in the subsurface. Currently any of five different noble gases (except radon) as well as CO{sub 2} can be selected, two at a time. For the two selected gas components, the Crovetto et al. (1982) model is used to calculate the Henry's law coefficients; and the Reid et al. (1987) correlation is used to calculate the gas phase diffusivities. Like most other sister modules, TOUGH2/EOSN can simulate nonisothermal multiphase flow and fully coupled transport in fractured porous media. Potential applications of the new module include, but are not limited to: (a) study of different reservoir processes such as recharge, boiling, condensation, and fracture-matrix fluid exchange; (b) characterization of reservoir geometry such as fracture spacing; and (c) analysis of CO{sub 2} sequestration.

Shan, Chao; Pruess, Karsten

2003-04-02

58

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

59

Tunneling ionization of noble gases in a high-intensity laser field  

Microsoft Academic Search

Studies of multiphoton ionization of noble gases have been carried out using 1-mum, 1-ps laser pulses with intensities up to the mid- 1016 W\\/cm2. To our knowledge, this work represents the first study of the production of highly ionized noble-gas ions done exclusively in the tunneling regime. It is found in this regime that the ionization at a given intensity

S. Augst; D. Strickland; D. D. Meyerhofer; S. L. Chin; J. H. Eberly

1989-01-01

60

Crystal melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene  

Microsoft Academic Search

Mineral melt partition coefficients of all noble gases (min\\/meltDi) have been obtained for olivine (ol) and clinopyroxene (cpx) by UV laser ablation (213 nm) of individual crystals grown from melts at 0.1 GPa mixed noble gas pressure. Experimental techniques were developed to grow crystals virtually free of melt and fluid inclusions since both have been found to cause profound problems

Veronika S. Heber; Richard A. Brooker; Simon P. Kelley; Bernard J. Wood

2007-01-01

61

Deep-mantle-derived noble gases in metamorphic diamonds from the Kokchetav massif, Kazakhstan  

Microsoft Academic Search

Metamorphic diamonds from the Kokchetav massif in northern Kazakhstan are considered to have crystallized from a C–O–H fluid during ultra-high-pressure metamorphism of metasedimentary rocks subducted to 190–280km depth. Noble gases contained in the diamonds offer great potential to constrain the noble gas state of deep mantle reservoirs. Previous studies have revealed that secondary processes during the diamond residence in the

H. Sumino; L. F. Dobrzhinetskaya; R. Burgess; H. Kagi

2011-01-01

62

Isotopic measurements of solar noble gases in individual micrometeorites from Greenland and Antarctica  

SciTech Connect

Noble gases are studied in individual 100 micron-size particles selected from Greenland and Antarctic glacial sediments. Noble gas isotopic and elemental patterns confirm the extraterrestrial origin of 81 out of 302 particles studied. Micrometeorites in this size range are particularly interesting because they correspond to the peak of the meteoritic mass flux distribution. Many particles studied are compositionally and morphologically similar to known meteoritic materials.

Olinger, C.T.

1990-01-01

63

Seawater-Derived Noble Gases and Halogens Preserved in Peridotite and Eclogite from the Subduction-Type Sanbagawa Metamorphic Belt  

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, Earth Planet. Sci. Lett. 89, 173-183). Nevertheless, subduction of sediment and seawater-dominated pore fluids to the deep mantle has been proposed to account for heavy noble gas (Ar, Kr and Xe) non-radiogenic elemental abundance and isotopic pattern of the convecting mantle (Holland and Ballentine, 2006, Nature 441, 186-191). To verify whether and how subduction fluids preserve a seawater signature, we have determined noble gas and halogen compositions of the Higashi-akaishi peridotite and Western Iratsu eclogite bodies in the Sanbagawa metamorphic belt, southwest Japan, in which relicts of slab-derived water are contained as hydrous mineral inclusions in wedge mantle rocks exhumed from depths in excess of 100 km (Mizukami et al., 2004, Nature 427, 432-436) and aqueous fluid inclusions in associated slab-derived eclogites (Endo et al., 2009, J. Metamorphic Geol. 27, 371-384; Endo, 2010, Isl. Arc 19, 313-335). The striking similarities of the observed noble gas and halogen compositions of the Higashi-akaishi peridotite with marine pore fluids (Sumino et al., 2010, Earth Planet. Sci. Lett. 294, 163-172) challenge a popular concept, in which the water flux into the mantle wedge is only by hydrous minerals in altered oceanic crust and sediment (e.g., Schmidt and Poli, 1998, Earth Planet. Sci. Lett. 163, 361-379). The Western Iratsu eclogite also exhibits non-radiogenic noble gas elemental ratios well explained by a mixing between seawater-derived and sedimentary components. These results indicate that subduction and closed system retention of marine pore fluid occurs up to depths of at least 100 km. The subducted halogen and noble gas compositions are clearly distinct from those of arc volcanic gases. This implies that the ultramafic-mafic metamorphic rocks of the Sanbagawa belt appear to have frozen-in and preserved a previously unseen part of the deep water recycling process whereby noble gases and halogens (and probably other volatiles) are injected into the wedge mantle just above the subducting slab, requiring a reassessment of the dominant transport mechanism and source of water in subduction zones. A small proportion of marine pore fluid, preserved in the downgoing hydrous peridotite and/or eclogite, can account for the heavy noble gas composition observed in the convecting mantle.

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

2010-12-01

64

Crystal melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene  

NASA Astrophysics Data System (ADS)

Mineral-melt partition coefficients of all noble gases ( min/meltDi) have been obtained for olivine (ol) and clinopyroxene (cpx) by UV laser ablation (213 nm) of individual crystals grown from melts at 0.1 GPa mixed noble gas pressure. Experimental techniques were developed to grow crystals virtually free of melt and fluid inclusions since both have been found to cause profound problems in previous work. This is a particularly important issue for the analysis of noble gases in crystals that have very low partition coefficients relative to coexisting melt and fluid phases. The preferred partitioning values obtained for the ol-melt system for He, Ne, Ar, Kr, and Xe are 0.00017(13), 0.00007(7), 0.0011(6), 0.00026(16), and 0.0006(-6)(+9), respectively. The respective cpx-melt partition coefficients are 0.0002(2), 0.00041(35), 0.0011(7), 0.0002(2), and 0.0002(-2)(+3). The data confirm the incompatible behaviour of noble gases for both olivine and clinopyroxene but unlike other trace elements these values show little variation for a wide range of atomic radius. The lack of dependence of partitioning on atomic radius is, however, consistent with the partitioning behaviour of other trace elements which have been found to exhibit progressively lower dependence of min/meltDi on radius as the charge decreases. As all noble gases appear to exhibit similar min/meltDi values we deduce that noble gases are not significantly fractionated from each other by olivine and clinopyroxene during melting and fractional crystallisation. Although incompatible, the partitioning values for noble gases also suggest that significant amounts of primordial noble gases may well have been retained in the mantle despite intensive melting processes. The implication of our data is that high primordial/radiogenic noble gas ratios ( 3He/ 4He, 22Ne/ 21Ne, and 36Ar/ 40Ar) characteristic of plume basalt sources can be achieved by recycling a previously melted (depleted) mantle source rather than reflecting an isolated, non-degassed primordial mantle region.

Heber, Veronika S.; Brooker, Richard A.; Kelley, Simon P.; Wood, Bernard J.

2007-02-01

65

Solubilities of nitrogen and noble gases in silicate melts under various oxygen fugacities: implications for the origin and degassing history of nitrogen and noble gases in the earth  

Microsoft Academic Search

Solubility experiments for nitrogen and noble gases (Ar and Ne) in silicate melts were conducted using two experimental configurations: one was conducted at 1 atmospheric pressure, T =1300°C and oxygen fugacity (fO2) of IW + 0.9 (i.e., 0.9 log units higher than the iron-wüstite buffer) and the other at high pressures (Ptotal ? 2 × 108 Pa), 1500°C and fO2

Akiko Miyazaki; Hajime Hiyagon; Naoji Sugiura; Kei Hirose; Eiichi Takahashi

2004-01-01

66

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

67

Seeded optical breakdown of molecular and noble gases  

SciTech Connect

We report experimental results on the dual laser-pulse plasma excitation in various gases at atmospheric pressure. Dilute plasma channels generated through filamentation of ultraintense femtosecond laser pulses in air, argon, and helium are densified through the application of multi-Joule nanosecond heater pulses. Optical breakdown in atomic gases can be achieved for considerably longer delays between femtosecond and nanosecond pulses compared to that in molecular gases. The densification of the seed channel in molecular gases is always accompanied by its fragmentation into discrete bubbles, while in atomic gases the densified channel remains smooth and continuous.

Polynkin, Pavel; Scheller, Maik; Moloney, Jerome V. [College of Optical Sciences, University of Arizona 1630 E. University Blvd., Tucson, Arizona 85721 (United States)

2012-07-30

68

What CO2 well gases tell us about the origin of noble gases in the mantle and their relationship to the atmosphere.  

PubMed

Study of commercially produced volcanic CO2 gas associated with the Colorado Plateau, USA, has revealed substantial new information about the noble gas isotopic composition and elemental abundance pattern of the mantle. Combined with published data from mid-ocean ridge basalts, it is now clear that the convecting mantle has a maximum (20)Ne/(22)Ne isotopic composition, indistinguishable from that attributed to solar wind-implanted (SWI) neon in meteorites. This is distinct from the higher (20)Ne/(22)Ne isotopic value expected for solar nebula gases. The non-radiogenic xenon isotopic composition of the well gases shows that 20 per cent of the mantle Xe is 'solar-like' in origin, but cannot resolve the small isotopic difference between the trapped meteorite 'Q'-component and solar Xe. The mantle primordial (20)Ne/(132)Xe is approximately 1400 and is comparable with the upper end of that observed in meteorites. Previous work using the terrestrial (129)I - (129)Xe mass balance demands that almost 99 per cent of the Xe (and therefore other noble gases) has been lost from the accreting solids and that Pu-I closure age models have shown this to have occurred in the first ca 100Ma of the Earth's history. The highest concentrations of Q-Xe and solar wind-implanted (SWI)-Ne measured in meteorites allow for this loss and these high-abundance samples have a Ne/Xe ratio range compatible with the 'recycled-air-corrected' terrestrial mantle. These observations do not support models in which the terrestrial mantle acquired its volatiles from the primary capture of solar nebula gases and, in turn, strongly suggest that the primary terrestrial atmosphere, before isotopic fractionation, is most probably derived from degassed trapped volatiles in accreting material.By contrast, the non-radiogenic argon, krypton and 80 per cent of the xenon in the convecting mantle have the same isotopic composition and elemental abundance pattern as that found in seawater with a small sedimentary Kr and Xe admix. These mantle heavy noble gases are dominated by recycling of air dissolved in seawater back into the mantle. Numerical simulations suggest that plumes sampling the core-mantle boundary would be enriched in seawater-derived noble gases compared with the convecting mantle, and therefore have substantially lower (40)Ar/(36)Ar. This is compatible with observation. The subduction process is not a complete barrier to volatile return to the mantle. PMID:18826923

Ballentine, Chris J; Holland, Greg

2008-11-28

69

A portable membrane contactor sampler for analysis of noble gases in groundwater.  

PubMed

To enable a wider use of dissolved noble gas concentrations and isotope ratios in groundwater studies, we have developed an efficient and portable sampling device using a commercially available membrane contactor. The device separates dissolved gases from a stream of water and collects them in a small copper tube (6 mm in diameter and 100 mm in length with two pinch-off clamps) for noble gas analysis by mass spectrometry. We have examined the performance of the sampler using a tank of homogeneous water prepared in the laboratory and by field testing. We find that our sampling device can extract heavier noble gases (Ar, Kr, and Xe) more efficiently than the lighter ones (He and Ne). An extraction time of about 60 min at a flow rate of 3 L/min is sufficient for all noble gases extracted in the sampler to attain equilibrium with the dissolved phase. The extracted gas sample did not indicate fractionation of helium ((3) He/(4) He) isotopes or other noble gas isotopes. Field performance of the sampling device was tested using a groundwater well in Vienna and results were in excellent agreement with those obtained from the conventional copper tube sampling method. PMID:22924615

Matsumoto, Takuya; Han, Liang-Feng; Jaklitsch, Manfred; Aggarwal, Pradeep K

2012-08-27

70

Noble gases and the early history of the Earth: Inappropriate paradigms and assumptions inhibit research and communication  

NASA Astrophysics Data System (ADS)

The development of models as tracers of nobel gases through the Earth's evolution is discussed. A new set of paradigms embodying present knowledge was developed. Several important areas for future research are: (1) measurement of the elemental and isotopic compositions of the five noble gases in a large number of terrestrial materials, thus better defining the composition and distribution of terrestrial noble gases; (2) determinations of relative diffusive behavior, chemical behavior, and the distribution between solid and melt of noble gases under mantle conditions are urgently needed; (3) disequilibrium behavior in the nebula needs investigation, and the behavior of plasmas and possible cryotrapping on cold nebular solids are considered.

Huss, G. R.; Alexander, E. C., Jr.

71

Theoretical and experimental investigation of thermal diffusion in binary mixtures of noble gases  

Microsoft Academic Search

Measurements of partial densities within a plane heat conduction cell have been performed by means of an electron beam fluorescence technique in order to investigate thermal diffusion in binary mixtures of noble gases in the transition regime. A good agreement has been found between experimental results and theoretical calculations based on the four moment method and on the molecular model

F. Romani; R. Schilder; G. Wortberg

1979-01-01

72

Combustion vs. Pyrolysis of Presolar Diamonds: Association of P3 and HL Noble Gases with Carbon  

Microsoft Academic Search

Since it became clear that presolar diamonds are not identical and perhaps consist of several carriers of isotopically anomalous (like HL-Xe and light nitrogen) and isotopically normal (carbon and P3 noble gases) components, it is important to know how these components are related to the diamond carriers. Because of diamond grains are too small to be analyzed individually and the

A. B. Verchovsky; A. V. Fisenko; C. T. Pillinger

1995-01-01

73

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

Microsoft Academic Search

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

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

1993-01-01

74

Mantle deformation and noble gases: Helium and neon in oceanic mylonites  

Microsoft Academic Search

In an effort to constrain the behavior of noble gases during mantle deformation, we present new helium and neon data in mylonites from subaerial St. Peter and St. Paul Archipelago (Mid-Atlantic Ridge) and the submarine Southwest Indian Ridge. Coupled vacuum crushing and melting experiments show that most of the helium and neon within the mylonites is contained in the mineral

Mark D. Kurz; Jessica M. Warren; Joshua Curtice

2009-01-01

75

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

76

Recharge and source-water insights from the Galapagos Islands using noble gases and stable isotopes  

NASA Astrophysics Data System (ADS)

Through a combined noble gas and stable isotope study carried out in the Galapagos Islands of Santa Cruz and San Cristobal, we demonstrate the utility of atmospheric noble gases in identifying recharge areas and timing of recharge in fractured, basaltic systems. Timing of recharge obtained through noble gas temperatures (NGTs) for all samples is corroborated by stable isotopes. Except for one sample, combined NGTs and stable isotope analyses point to recharge during the hot season for all low-altitude (<˜420 m) spring samples from San Cristobal and all basal aquifer samples in Santa Cruz. Stable isotope comparisons also indicate that San Cristobal springs located at high altitudes (>420 m above sea level) are recharged during both the "garúa" and hot seasons. Preservation of seasonality independently recorded by NGTs and stable isotopes is further reinforced by estimated young water ages. Samples located at high-altitude display systematic deviations of dissolved noble gases from expected air saturated water values and lead to inconsistent recharge altitudes and temperatures using standard NGT models. Existing degassing models are unable to account for the observed noble gas pattern for most samples. We explore various mechanisms to assess their potential at reproducing the observed noble gas signature. In particular, the potential impact of fog droplets during the cooler "garúa" season on dissolved noble gas concentrations in groundwater and the effect of mixing high-altitude (?1500 m) rainwater with low-altitude (˜400 m) fog droplets is explored. This mixing hypothesis is capable of explaining Ne and Xe concentrations for most high-altitude samples.

Warrier, Rohit B.; Castro, Maria Clara; Hall, Chris M.

2012-03-01

77

Spectral line broadening of atoms by noble gases  

NASA Astrophysics Data System (ADS)

The complex universal approach for calculations of the binary broadening of atomic spectral lines by buffer noble gas atoms is presented. The interatomic interaction is described on the basis of the Buckingham potential, parameterized with the help of ab initio electron modeling. The Unified Frank-Condon Theory is used for the calculations of the total line profile. For the first time the impact limit is determined exactly using the Van der Waals long-range tail of the potential and taking into account the degeneracy of quasimolecular states but neglecting non-adiabatic effects. The general asymptotic wings dependences of the profile are established for the Buckingham parameterized potential. The receipts of the wings cut-offs are formulated for the approximate but sufficiently accurate evaluation of the total line profile using only the Van der Waals part of potential to be applied in large scale calculations of radiative transfer.

Demura, A. V.; Umanskii, S. Ya; Scherbinin, A. V.; Zaitsevskii, A. V.

2012-12-01

78

Electrical conductivity of noble gases at high pressures  

SciTech Connect

Theoretical results for the electrical conductivity of noble gas plasmas are presented in comparison with experiment. The composition is determined within a partially ionized plasma model. The conductivity is then calculated using linear response theory, in which the relevant scattering mechanisms of electrons from ions, electrons, and neutral species are taken into account. In particular, the Ramsauer-Townsend effect in electron-neutral scattering is discussed and the importance of a correct description of the Coulomb logarithm in electron scattering by charged particles is shown. A detailed comparison with recent experiments on argon and xenon plasmas is given and results for helium and neon are also revisited. Excellent agreement between theory and experiment is observed, showing considerable improvement upon previous calculations.

Adams, J. R.; Reinholz, H.; Redmer, R.; Mintsev, V. B.; Shilkin, N. S.; Gryaznov, V. K. [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany) and School of Physics, University of Western Australia, Crawley WA 6009 (Australia); Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany); Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region (Russian Federation)

2007-09-15

79

Noble gases dissolved in groundwater in a volcanic aquifer: Helium isotopes in the Kumamoto Plain  

NASA Astrophysics Data System (ADS)

This study Investigates a tracing method using dissolved noble gases to survey the groundwater flow in a large groundwater basin. The tracing method is based on measuring the concentrations of noble gases and the ratio of helium isotopes in groundwater samples. Since it is very difficult to detect trace amounts of noble gases and helium with high accuracy in a 15-ml groundwater sample, dissolved gases were extracted and purified, then a high-resolution mass spectrometer was used for measurement and comparison with standard samples. We used this method with samples from a confined aquifer formed by the deposition of pyroclastic flow in the Kumamoto Plain on the west side of Mt. Aso in central Kyushu, Japan. The groundwater basin under the plain is divided into four small basins, based on the helium concentrations and isotope ratios, with two major groundwater flows. One flow is buried by the Aso pyroclastic flow along the old Kase River; the other is along the Tsuboi River Valley. These two groundwater flows were identified from the different helium isotope-ratios. The helium component from the deep mantle is mixed into the groundwater under the Kumamoto Plain. Finally, data on the concentrations and ratios of3He to4He in groundwater samples were used to determine the location of faults in the volcanic aquifer.

Mahara, Y.

1995-06-01

80

Effect of noble gases on oxygen and glucose deprived injury in human tubular kidney cells.  

PubMed

The noble gas xenon has been shown to be protective in preconditioning settings against renal ischemic injury. The aims of this study were to determine the protective effects of the other noble gases, helium, neon, argon, krypton and xenon, on human tubular kidney HK2 cells in vitro. Cultured human renal tubular cells (HK2) were exposed to noble gas preconditioning (75% noble gas; 20% O(2); 5% CO(2)) for three hours or mock preconditioning. Twenty-four hours after gas exposure, cell injury was provoked with oxygen-glucose deprived (OGD) culture medium for three hours. Cell viability was assessed 24 h post-OGD by a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Other cohorts of cultured cells were incubated in the absence of OGD in 75% noble gas, 20% O(2) and 5% CO(2) and cellular signals phospho-Akt (p-Akt), hypoxia-inducible factor-1alpha (HIF-1alpha) and Bcl-2 were assessed by Western blotting. OGD caused a reduction in cell viability to 0.382 +/- 0.1 from 1.0 +/- 0.15 at control (P < 0.01). Neon, argon and krypton showed no protection from injury (0.404 +/- 0.03; 0.428 +/- 0.02; 0.452 +/- 0.02; P > 0.05). Helium by comparison significantly enhanced cell injury (0.191 +/- 0.05; P < 0.01). Xenon alone exerted a protective effect (0.678 +/- 0.07; P < 0.001). In the absence of OGD, helium was also detrimental (0.909 +/- 0.07; P < 0.01). Xenon caused an increased expression of p-Akt, HIF-1alpha and Bcl-2, while the other noble gases did not modify protein expression. These results suggest that unlike other noble gases, preconditioning with the anesthetic noble gas xenon may have a role in protection against renal ischemic injury. PMID:20472713

Rizvi, Maleeha; Jawad, Noorulhuda; Li, Yuantao; Vizcaychipi, Marcela P; Maze, Mervyn; Ma, Daqing

2010-05-14

81

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 20°C. The atmospheric rare gas retention values found for

E. Mazor; R. O. Fournier

1973-01-01

82

The Noble Gases in the HF-Susceptible Portion of Ivuna (CI), Analyzed by Closed System Step Etching  

NASA Astrophysics Data System (ADS)

Primordial noble gases (possibly similar to Q or HF) are released from the HF-solvable portion of Ivuna during closed system step etching, indicating that information about primordial components is lost when studied only in acid-resistant residues.

Riebe, M.; Busemann, H.; Wieler, R.

2013-09-01

83

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

84

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

85

The Carriers of Noble Gases in Presolar Diamonds--A Case of ALICE in Wonderland?  

NASA Astrophysics Data System (ADS)

The carrier of the P3 noble gas component in nanometre diamonds from primitive meteorites is still enigmatic. On the one hand it was found to be closely associated with the HL carrier: for P3 rich samples Xe-P3/Xe-HL ratio is remarkably constant. As might be expected, these two components are not separable during laboratory chemical treatment, although they are easily resolved by stepped heating. The fact that P3 noble gases are released at low temperature (300-800 degrees C) during pyrolysis led to the suggestion that they are located near diamond surface. Moreover the association of P3 noble gases released with chemically active gases in the same temperature range can be interpreted to indicate that P3 gases are evolved as a result of chemical reactions destroying diamond surface. At the present time it is not absolutely clear what is happening at the diamond surface during stepped pyrolysis. With no added oxygen, we observe CO + CO2 in the low temperature products in amounts corresponding to 10-15% of the total carbon: we therefore have argued that surface absorbed oxygen is responsible for the reactions. Huss and Lewis supposed that a reaction with hydrogen, also present on the diamond surface, might take place to induce restructuring of the outermost layers during pyrolysis. In our experience, destruction of diamond surface rather than modification is a real fact but how it relates to the release of P3 gases is not quite clear. Incidentally, the release of chemically active gases is observed irrespective of whether or not the P3 component is present in diamond. The same is true for the presence of surface bonded hydrogen and oxygen. Thus, if the mechanism of P3 gas loss under natural conditions is the same as that in the laboratory experiments, then later on the diamond surface acquires a new layer of oxygen and/or hydrogen. In other words the extraneous elements could act as agent(s) for release of P3 noble gases and need not represent a common constituent(s) of the carrier.

Verchovsky, A. B.; Pillinger, C. T.

1996-03-01

86

Gas-phase Sequestration of Noble Gases in the Protosolar Nebula: Possible Consequences on the Outer Solar System Composition  

NASA Astrophysics Data System (ADS)

We address the problem of the sequestration of Ar, Kr, and Xe by H_3^+ in the gas-phase conditions encountered during the cooling of protoplanetary disks when H_3^+ is competing with other species present in the same environment. Using high-level ab initio simulations, we try to quantify other sequestration possibilities involving He, H_5^+, H2O, and H3O+ present in the protosolar nebula. Apart from the fact that H_3^+ complexes formed with heavy noble gases are found to be by far much more stable than those formed with He or H2O, we show that H2D+ and H3O+, both products of the reactions of H_3^+ with HD and H2O, can also be efficient trapping agents for Ar, Kr, and Xe. Meanwhile, the abundance profile of H_3^+ in the outer part of the nebula is revisited with the use of an evolutionary accretion disk model that allows us to investigate the possibility that heavy noble gases can be sequestered by H_3^+ at earlier epochs than those corresponding to their trapping in planetesimals. We find that H_3^+ might be abundant enough in the outer protosolar nebula to trap Xe and Kr prior their condensation epochs, implying that their abundances should be solar in Saturn's current atmosphere and below the observational limit in Titan. The same scenario predicts that comets formed at high heliocentric distances should also be depleted in Kr and Xe. In situ measurements, such as those planed with the Rosetta mission on 67P/Churyumov-Gerasimenko, will be critical to check the validity of our hypotheses.

Pauzat, F.; Ellinger, Y.; Mousis, O.; Dib, M. Ali; Ozgurel, O.

2013-11-01

87

Production of noble gases near the surface of Europa and the prospects for in situ chronology  

NASA Astrophysics Data System (ADS)

The age of the surface of Europa is probably tens of Myr or less, but is poorly constrained. Two different geochronology schemes could potentially be applied to near-surface samples to provide far more precise ages. First, the surface salts apparently contain enough potassium to make potassium argon dating feasible. Second, the bombardment of the surface with both galactic cosmic rays and protons trapped within the jovian magnetosphere will cause nuclear reactions that can lead to measurable buildups of cosmogenic noble gases, which can be used to determine both cosmic-ray exposure ages and erosion, deposition, or mixing rates for surface modification. The major differences between Europa's salt-rich ice and the rocks (meteorites, lunar samples and terrestrial rocks) in which cosmogenic noble gases are normally measured are that the abundance of target elements for nuclear reactions creating neon and argon are lower (because of the high water content), but neutron-capture reactions, particularly 35Cl(n,?)36Cl(?-)36Ar, are enhanced because of the thermalizing effects of the water. As well as presenting calculations of noble gas production near the surface of Europa, we also show that the measurements required to determine ages are within reach of technology in the near future, if an instrument can be landed on the surface of Europa.

Swindle, T. D.; Masarik, J.; Kollár, D.; Kim, K. J.; Reedy, R. C.

2005-03-01

88

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

89

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

90

Phase equilibria for hydrate formation from binary mixtures of ethane, propane and noble gases  

Microsoft Academic Search

Equilibrium conditions for hydrate formation from binary mixtures of C2H6, C3H8 and noble gases such as Ar, Kr and Xe were experimentally determined at the temperatures of 273.5, 276.5 and 278.5K. The binary systems of Xe+C3H8, Kr+C3H8 and Kr+C2H6 mixtures have hydrate azeotropes with pressure minimum points in the isothermal pressure-composition diagrams. Hydrate structural transitions were also observed in the

Tatsuo Maekawa

2006-01-01

91

Crystal–melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene  

Microsoft Academic Search

Mineral–melt partition coefficients of all noble gases (min\\/meltDi) have been obtained for olivine (ol) and clinopyroxene (cpx) by UV laser ablation (213nm) of individual crystals grown from melts at 0.1GPa mixed noble gas pressure. Experimental techniques were developed to grow crystals virtually free of melt and fluid inclusions since both have been found to cause profound problems in previous work.

Veronika S. Heber; Richard A. Brooker; Simon P. Kelley; Bernard J. Wood

2007-01-01

92

Selling candles in a post-Edison world: phasing with noble gases bound within engineered sites.  

PubMed

The utility of noble gases for phase determination has been limited by the lack of naturally occurring binding sites in proteins. Wild-type T4 lysozyme contains one such binding site. By mutating large hydrophobic residues to alanine, additional noble-gas binding sites have been successfully introduced into this protein. Using data from xenon derivatives of the wild type, two single mutants and the corresponding double mutant, experimental phases for T4 lysozyme have been determined using standard multiple isomorphous replacement (MIR) techniques. These phases, which were obtained from room-temperature data collected on a rotating-anode source, are comparable in quality with phases calculated using selenomethionine-based multiwavelength anomalous dispersion (MAD) methods on frozen crystals at a synchrotron. In addition, this method of introducing noble-gas binding sites near specific residues should provide useful information for determining the register of amino acids within electron-density maps and the positions of molecules within the unit cell. PMID:14573947

Quillin, Michael L; Matthews, Brian W

2003-10-23

93

Deep mantle derived noble gases in metamorphic microdiamonds from Kokchetav massif, Kazakhstan  

NASA Astrophysics Data System (ADS)

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 implantation of ?-particle produced from decay of U, Th-series elements in the surrounding rocks [3]. On the other hand, while anomalously abundant 3He could be explained by nucleogenic production via 6Li (n, ?) 3H after the diamond formation, anomalous high Li content is required in the diamonds or ~20 ?m vicinity in the host rock. Alternatively, the highly concentrated 3He might reside in Li-rich contaminants in the analyzed samples [3]. In contrast to that the original noble gas signature of the diamonds has been severely modified by the secondary processes during the diamond residence in the host rock, nanometric solid/fluid inclusions in the microdiamonds, which represent a former diamond-forming fluid [1], have a potential to preserve noble gas signature trapped at the diamonds formation. We have performed noble gas analysis of the Kokchetav microdiamonds applying two gas extraction techniques, in vacuo crushing and stepwise heating; the latter selectively extracts noble gases from the inclusions with less noble gas extraction from diamond lattice. Our studies show that the 3He concentration and 3He/4He of our sample are several orders of magnitude lower than those previously reported, and we conclude that the “unprecedentedly” high 3He/4He reported earlier can be addressed to the contamination due to a procedure of the diamonds separation from the host rocks. The fact that most 3He was extracted by the crushing diamonds indicates that 3He occurs within inclusions trapped during diamond formation. Since recoil length of 3He-to-be 3H in the 6Li (n, ?) reaction is much larger than the size of the inclusions, the in situ production and retention of the nucleogenic 3He are unlikely to be the major source of the 3He in the inclusions. An estimate of the inclusion-hosted 3He/4He of 4.3E-5 is significantly higher than that of the MORB-source mantle (1.1E-5), but close to the highest values observed in Hawaiian- and Icelandic-hotspots (ca. 5E-5) where plumes are considered to brought primordial noble gases from deep mantle. Neon isotope ratios obtained with the stepwise heating also indicate presence of plume-like component. The result shows that plume-like, primordial noble gases were involved in the Kokchetav microdiamond formation, implying an interaction of the continental slab and a fragment of the very deep mantle. The latter was placed to the mantle wedge of subduction channel probably from deep lower mantle source due to a large scale mantle convection. References : [1] Dobrzhinetskaya et al. (2006) EPSL 243, 85-93. [2] Shukolyukov et al. (1993) Petrol. 1, 110-119. [3] Verchovsky et al. (1993) EPSL 120, 87-102.

Sumino, H.; Dobrzhinetskaya, L.

2009-12-01

94

Noble Gases in Desert Meteorites: Howardities, Unequilibrated Chondrites, Regolith Breccias and an LL7  

NASA Astrophysics Data System (ADS)

We present He, Ne, and Ar data of 39 samples from 17 meteorites of various types. For three CV3 and two unequilibrated ordinary chondrites Kr and Xe data are also reported. The analyses served various purposes, e. g. to check for presence of solar noble gases, to determine concentrations of primordial noble gases, to study cosmic ray exposure ages including possible parent body exposures, and to recognize paired meteorites. The data are shown in Tables 1 and 2. Ne-21 exposure ages are calculated with the cosmogenic nuclide production model by Leya et al., assuming average chemical composition of the respective meteorite class and taking the (Ne-22/Ne-21)cos ratio as shielding parameter. In some cases we had to assume additionally a meteoroid radius <32 cm. We report an age range (T(sup 21) min - T(sup 21) max) rather than a single age to indicate that even when (Ne-22/Ne-21)cos is available, meteoroid size and sample depth are not unambiguously known, hence the Ne-21 production rate is only constrained to within certain limits. The mean production rates used here compare well with those given by Eugster and Eugster and Michel for (Ne-22/Ne-21)cos values between 1.08 - 1.12 (chondrites) and 1.10 - 1.15 (howardites), respectively. On the other hand, our values are up to 30% lower for high (Ne-22/Ne-21)cos values, i.e. small meteorites and low shielding.

Wieler, R.; Baur, H.; Busemann, H.; Heber, V. S.; Leya, I.

2000-01-01

95

Laser-polarized noble gases: a powerful probe for biology, medicine, and subatomic physics  

NASA Astrophysics Data System (ADS)

For over a decade, laser-polarized noble gases such as ^3He and ^129Xe have proven useful for a wide range of scientific inquiries. These include investigations of pulmonary disease using the polarized gas as a signal source for magnetic resonance imaging (MRI), measurements of various aspects of nucleon structure, and tests of fundamental symmetries. Early efforts were often limited by expensive and bulky laser systems, but ongoing advancements in solid-state lasers have enabled increasingly large volumes of polarized gas to be produced with steadily improved polarization. Equally important have been advances in the fundamental understanding of spin exchange. This has led, for example, to the introduction of hybrid mixtures of alkali metals that can increase the efficiency of spin exchange by an order of magnitude. As a consequence of these advances, the figure of merit for polarized nuclear targets has increased by roughly three orders of magnitude in comparison to early accelerator-based experiments. And in MRI applications, it has become possible to pursue increasingly sophisticated imaging protocols that provide a wide range of diagnostic information. Even the earliest noble-gas MR images of the gas space of the human lung provided unprecedented resolution. More recent work includes the use of diffusion-sensitizing pulse sequences to study lung microstructure, and tagging techniques that enable the visualization (in real-time MRI movies) of gas flow during breathing. The range of applications of laser-polarized noble gases is continuing to grow, and it is notable that with an improved understanding of the underlying physics, it is quite likely that the capabilities of this useful technology will expand for some time to come.

Cates, Gordon

2010-03-01

96

Shock Compression of Liquid Noble Gases to Multi-Mbar Pressures  

NASA Astrophysics Data System (ADS)

The high pressure -- high temperature behavior of noble gases is of considerable interest because of their use in z-pinch liners for fusion studies and for understanding astrophysical and planetary evolution. However, our understanding of the equation of state (EOS) of the noble gases at extreme conditions is limited. A prime example of this is the liquid xenon Hugoniot. Previous EOS models rapidly diverged on the Hugoniot above 1 Mbar because of differences in the treatment of the electronic contribution to the free energy. Similar divergences are observed for krypton EOS. Combining shock compression experiments and density functional theory (DFT) simulations, we can determine the thermo-physical behavior of matter under extreme conditions. The experimental and DFT results have been instrumental to recent developments in planetary astrophysics and inertial confinement fusion. Shock compression experiments are performed using Sandia's Z-Accelerator to determine the Hugoniot of liquid xenon and krypton in the Mbar regime. Under strong pressure, krypton and xenon undergo an insulator to metal transition. In the metallic state, the shock front becomes reflective allowing for a direct measurement of the sample's shock velocity using laser interferometry. The Hugoniot state is determined using a Monte Carlo analysis method that accounts for systematic error in the standards and for correlations. DFT simulations at these extreme conditions show good agreement with the experimental data -- demonstrating the attention to detail required for dealing with elements with relativistic core states and d-state electrons. The results from shock compression experiments and DFT simulations are presented for liquid xenon to 840 GPa and for liquid krypton to 800 GPa, decidedly increasing the range of known behavior of both gases. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U. S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Root, Seth

2011-11-01

97

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

NASA Astrophysics Data System (ADS)

Noble gas concentrations and isotopic ratios are presented for 38 deep (˜0.5-3.6 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 in situ production for these two gases within the sedimentary strata is insufficient to account for the observed crustal component in the Michigan brines. These point to the presence of a deep, external source for crustal noble gases, likely the Precambrian crystalline basement beneath the Michigan Basin. Furthermore, observed elemental ratios of crustal noble gases (4He/40Ar, 21Ne/40Ar, 4He/136Xe, and 21Ne/136Xe) in these brines vary over several orders of magnitude with respect to the expected production ratios from the crystalline basement rocks and display a systematic pattern within the basin. Specifically, samples above the Salina Group (shallow formations) are relatively enriched in 4Hecrust and 21Necrust with respect to 40Arcrust and 136Xecrust, as opposed to those below the massive Salina evaporite layer (deeper formations) which exhibit complementary patterns. We show that such a general trend is best explained by a Rayleigh-type elemental fractionation model involving upward transport of crustal noble gases and associated elemental fractionation processes, controlled by both diffusion- and solubility-related mechanisms. As previously indicated by the mantle and atmospheric noble gas signatures in these same Michigan brine samples, release of deep crustal noble gases into the basin is yet another independent indicator pointing to the occurrence of a past thermal event in the basin. We suggest that recent reactivation of the ancient midcontinent rift system underneath the Michigan Basin is likely responsible for the upward transport of heat and loss of the atmospheric noble gas component, as well as release of crustal (still ongoing) and mantle noble gases into the basin via deep-seated faults and fracture zones. Such a model also supports an internal heat source hypothesis as being largely responsible for the existence of past high temperatures in the basin without involvement of large-scale brine migration from peripheral forming orogenic fold belts.

Ma, Lin; Castro, Maria Clara; Hall, Chris M.

2009-06-01

98

Testing the noble gas paleothermometer with a yearlong study of groundwater noble gases in an instrumented monitoring well  

NASA Astrophysics Data System (ADS)

We report the results of a yearlong noble gas study conducted in 2008-2009 together with continuous physical and chemical measurements collected in a monitoring well in an aquifer in southern Michigan. Conditions near the water table are correlated with noble gas concentrations, corresponding noble gas temperatures (NGTs), and precipitation events. This yearlong study is the first noble gas field test that has employed natural recharge and in situ monitored conditions, with minimal disturbance of the unsaturated zone. This detailed study demonstrates that significant changes in conditions near the water table can occur over a year that can greatly affect NGTs. Results show that precipitation events are detected within hours at the water table, but a lag in pressure response argues for a long time constant for gas transport within the unsaturated zone. There is strong evidence for the depletion of oxygen near the water table, which affects the noble gas air-saturated water component. During reducing conditions there is evidence for significant noble gas degassing. Rain from the passage of Hurricane Ike caused a significant shift in stable isotope ratios and injection of a large quantity of excess air and likely led to a much more oxygen-rich environment in the soil gas. Although individual models can account for NGTs over portions of the record, no single NGT model can account for all features observed over the entire study. It is likely that the NGT temperature proxy must be viewed as an average of recharge conditions over several years.

Hall, Chris M.; Castro, M. Clara; Lohmann, Kyger C.; Sun, Tie

2012-04-01

99

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

100

Viscosity and thermal conductivity from non-conformal potentials. I Theory and application to noble gases  

NASA Astrophysics Data System (ADS)

The approximate non-conformal (ANC) theory provides effective spherical potentials for more than 40 pure real gases and predicts many of their binary mixtures in the case of the second volumetric virial coefficients B(T). Each substance is characterized by only three parameters; besides the usual minimum energy ? and its corresponding position rm, a softness parameter s is proposed to take account of the form of a particular potential. In this work the ANC theory is extended to take account of viscosity ?(T) and thermal conductivity ?(T) coefficients in dilute gases. Very simple expressions are derived to calculate the appropriate collision integral ? as a function of temperature and in terms of the parameters ?, rm and s, using a reference collision integral ?0(T). The theory is successfully applied to the noble gases Ne, Ar, Kr and Xe, with deviations from experiment for ?(T) and ?(T) within experimental uncertainties. In the case of Ne, the ANC potential obtained here reproduces simultaneously ?(T) and ?(T) as well as B(T) within experimental uncertainty, using a single set of parameters. A prediction for the radon gas is proposed.

Eloy Ramos, Jesús

101

Trapped Solar Wind Noble Gases, Kr81\\/Kr Exposure Ages and K\\/Ar Ages in Apollo 11 Lunar Material  

Microsoft Academic Search

Grain size and etching experiments show that the fine lunar material contains large amounts of trapped solar wind particles. Elemental and isotopic compositions of the noble gases in solar material and in the terrestrial atmosphere are significantly different, except for the Ar36\\/Ar38 and the Kr isotope ratios. Exposure ages of two rocks and of the fine material are between 380

P. Eberhardt; J. Geiss; H. Graf; N. Groegler; U. Kraehenbuehl; H. Schwaller; J. Schwarzmueller; A. Stettler

1970-01-01

102

Analysis of salt effects on solubility of noble gases in water using the reference interaction site model theory  

Microsoft Academic Search

We have developed robust and very efficient algorithms for solving the reference interaction site model (RISM) equations for salt solutions in the bulk and near a solute atom of noble gases. The theory of dielectric consistency recently developed for solutions at finite salt concentrations is employed in the formalism. The change in water structure in the bulk caused by addition

Masahiro Kinoshita; Fumio Hirata

1997-01-01

103

Evidence for molecular size dependent gas fractionation in firn air derived from noble gases, oxygen, and nitrogen measurements  

Microsoft Academic Search

We present elemental and isotopic measurements of noble gases (He, Ne, Ar, Kr, and Xe), oxygen and nitrogen of firn air from two sites. The first set of samples was taken in 1998 at the summit of the Devon Ice Cap in the eastern part of Devon Island. The second set was taken in 2001 at NGRIP location (North Greenland).He

C. Huber; U. Beyerle; M. Leuenberger; J. Schwander; R. Kipfer; R. Spahni; J. P. Severinghaus; K. Weiler

2006-01-01

104

Noble gases, Kr-81-Kr ages, and Be-10 of chondrites from China  

NASA Astrophysics Data System (ADS)

A comprehensive study of the cosmic-ray exposure history of ordinary chondrites from China was carried out using measurements of the noble gas isotopic abundances and Be-10 concentrations. The following average cosmic-ray exposure ages, based on cosmogenic Ne-21 and on Kr-81-Kr dating were obtained: Zhaodong (L4) - 15.7 + or - 3.0 Myr, Nan Yang Pao (L6) - 48 + or - 10.0 Myr, Guangrao (L6) - 16.8 + or - 3.5 Myr, and Lunan (H6) - 26.7 + or - 5.0 Myr. The H5 chondrite Zaoyang was exposed for only 0.90 + or - 0.12 Myr to Galactic cosmic rays, as calculated from the Be-10 activity and from the low amounts of cosmic-ray-produced noble gases. The Zaodong chondrite contains large amounts of Kr-80 and Kr-82 produced by neutron capture of bromine. From the high slowing down density for neutrons, a preatmospheric mass of more than 1800 kg is derived for this meteorite.

Eugster, O.; Shen, Ch.; Beer, J.; Suter, M.; Wolfli, W.; Yi, W.; Wang, D.

1987-06-01

105

Adsorption and separation of binary mixtures of noble gases on single-walled carbon nanotube bundles  

NASA Astrophysics Data System (ADS)

Adsorption and separation of binary mixtures of noble gases including Argon (Ar), Krypton (Kr), and Xenon (Xe) on (10,10) single-walled carbon nanotube (SWCNT) bundles is simulated by extensive equilibrium molecular dynamics (MD). Adsorption energies, diffusion coefficients, activation energies, and radial distribution functions (RDFs) were calculated to address the thermodynamics, transport and structural properties of adsorption process. The simulation results of exposing Ar-Kr, Ar-Xe, and Kr-Xe mixtures on (10,10) SWCNT bundles at temperatures of 75, 150, and 300 K, show that amount of adsorption is strongly influenced by the applied temperature. On the other hand, RDF plots show obviously that separation of binary gaseous mixture is occurred, where the heavier noble gas is adsorbed more than the lighter one in a selective manner by bundle. It is seen that the increase in the applied temperature results in more separation. These findings provide us a possible application of carbon nanotubes (CNTs) as efficient nanomaterials for separation and storage of gas mixtures.

Foroutan, Masumeh; Taghavi Nasrabadi, Amir

2011-02-01

106

Evidence for high saturation of porous amorphous carbon films by noble gases  

NASA Astrophysics Data System (ADS)

Results of the electron diffraction study of Kr and Xe deposits on amorphous porous carbon substrates are reported. We have observed mixtures of crystallites typical of condensates formed at such substrates at low deposition temperatures. However, in the warming process at temperatures about three to five degrees below the sublimation point characteristic of flat substrates, the diffraction patterns demonstrate that large crystallites gradually disappear and a highly disordered matter forms. Such transformed samples are kept inside substrates several dozens degrees above the sublimation points which are typical of these substances on flat (e.g., metallic) substrates. We ascribe these features to specificity of composites formed from noble gases strongly bonded inside porous carbon matrices due to capillary filling at temperatures close to the sublimation points.

Krainyukova, N. V.

2009-04-01

107

Model-potential approach to positron elastic scattering from noble gases  

NASA Astrophysics Data System (ADS)

In a recent publication [D. Assafrão , Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.84.022713 84, 022713 (2011)] a model-potential approach was proposed to positron-atom scattering based on an adiabatic method that treats the positron as a light nucleus. In this paper the formalism is further improved by the introduction of semiempirical energy terms which appropriately account for the positron-target interaction at long and short ranges. Our method allows us to describe the main observed features of the elastic cross sections for positron scattering from He, Ne, Ar, Kr, and Xe. Valuable insights into the cross-section behavior below the positronium formation threshold, the scattering lengths, and other aspects of the low-energy positron-noble gases scattering are presented.

Poveda, Luis A.; Dutra, Adriano; Mohallem, José R.; Assafrão, Denise

2013-05-01

108

Thermal Conductivity of Pure Noble Gases at Low Density from Ab Initio Prandtl Number  

NASA Astrophysics Data System (ADS)

The experimental data reported in the literature after 2000 have been investigated for the viscosity and thermal conductivity of helium-4, neon, and argon at low density. The well-established values of thermal conductivity by transient hot-wire measurements are not reliable enough for noble gases in the low-pressure gas region. These facts motivate us to determine the thermal conductivity from accurate viscosity data and the ab initio Prandtl number, with an uncertainty of 0.25 % for temperatures ranging between 200 K and 700 K. The theoretical accuracy is superior to the accuracy of the best measurements. The calculated results are accurate enough to be applied as standard values for the thermal conductivity of helium-4, neon, and argon over the considered temperature range.

Song, Bo; Wang, Xiaopo; Liu, Zhigang

2013-03-01

109

Observation of threshold effects in positron scattering from the noble gases.  

PubMed

Channel coupling is a phenomenon that has been investigated for many scattering processes, and is responsible for the formation of cusps or steps in the cross sections for open scattering channels at, or near, the onset of a new scattering channel. It has long been speculated that the opening of the positronium formation channel may lead to the formation of such cusp features in the elastic positron scattering cross section. In this work, elastic scattering of positrons has been measured in the region of the positronium formation threshold for the noble gases He-Xe. Cusplike behavior is observed and, while the features which are observed appear broad, they represent a magnitude of between 4 and 15% of the total elastic cross section. No evidence is found of any other features in this region, at least within the uncertainty of the present data, discounting the possibility of scattering resonances. PMID:20868040

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

2010-08-13

110

Cross-Section Measurements for Elastic and Inelastic Scattering of Neutrons from Noble Gases  

NASA Astrophysics Data System (ADS)

Neutron backgrounds are a significant concern to experiments that attempt to directly detect Weakly Interacting Massive Particle (WIMP) dark matter. Recoil nuclei produced by neutron elastic scattering can mimic WIMP signatures. There is insufficient experimental data available for the scattering cross-sections of neutrons with noble gases (Ne, Ar, Xe), which are candidate target materials for such experiments. Neutron elastic and inelastic scattering from neon of natural abundance was investigated at the Triangle Universities Nuclear Laboratory at neutron energies relevant to (?,n) and low-energy spallation neutron backgrounds in these experiments. The differential cross-section was measured using a time-of-flight technique at neutron energies of 8.0 and 5.0 MeV. Details of the experimental technique and current status of measurements will be presented.

Macmullin, Sean; Kidd, Mary; Tornow, Werner; Howell, Calvin; Brown, Michael; Henning, Reyco

2010-11-01

111

Paleotemperatures in the southwestern United States derived from noble gases in ground water.  

PubMed

A paleotemperature record based on measurements of atmospheric noble gases dissolved in ground water of the Carrizo aquifer (Texas) shows that the annual mean temperature in the southwestern United States during the last glacial maximum was about 5 degrees C lower than the present-day value. In combination with evidence for fluctuations in mountain snow lines, this cooling indicates that the glacial lapse rate was approximately the same as it is today. In contrast, measurements on deep-sea sediments indicate that surface temperatures in the ocean basins adjacent to our study area decreased by only about 2 degrees C. This difference between continental and oceanic records poses questions concerning our current understanding of paleoclimate and climate-controlling processes. PMID:17795002

Stute, M; Schlosser, P; Clark, J F; Broecker, W S

1992-05-15

112

Isotope systematics of noble gases in the Earth's mantle: possible sources of primordial isotopes and implications for mantle structure  

NASA Astrophysics Data System (ADS)

The Earth's mantle contains a mixture of primordial noble gases, in particular solar-type helium and neon, and radiogenic rare gases from long-lived U, 232Th, 40K and short-lived 129I, 244Pu. Rocks derived from deep mantle plume magmatism like on Hawaii or Iceland contain a higher proportion of primordial nuclides than rocks from the shallow upper mantle, e.g. mid ocean ridge basalts (MORBs). This is widely regarded as the key evidence for survival of a less degassed and more "primitive" reservoir within the lower mantle. We present an evaluation of noble gas composition showing the shallow mantle to have about five times more radiogenic (relative to primordial) isotopes than Hawaii/Iceland-type plume reservoirs, no matter if short- or long-lived decay systems are considered. This fundamental property suggests that both MORB and plume-type noble gases are mixtures of: (1) a homogeneous radiogenic component present throughout most of the mantle and (2) a uniform primordial noble gas component with very minor radiogenic ingrowth. This conclusion depends crucially on the observed excess of radiogenic Xe in plume-derived rocks, and is only valid if this Xe excess is inherent to the plume sources. Possible sources of the primordial component of mantle plume reservoirs—and possibly also the MORB mantle—could be mantle reservoirs that remained relatively isolated over most of Earth's history ("blobs", a deep abyssal layer, or the D" layer), but these need a considerable concentration of primordial gases to compensate U, Th, K decay over 4.5 Ga. Earth's core is evaluated as an alternative viable source feeding primordial nuclides into mantle reservoirs: even low metal-silicate partitioning coefficients allow sufficient primordial noble gases to be incorporated into the early forming core, as the undifferentiated proto-Earth was initially gas-rich. Massive mantle degassing soon after core formation then provides the opposite concentration gradient that allows primordial noble gases reentering the mantle at the core-mantle boundary, probably via partial mantle melts. Another possible source of primordial noble gases in Earth's mantle are subducted sediments containing extraterrestrial dust with solar He and Ne, but this supply mechanism crucially depends on largely unconstrained parameters. The latter two scenarios do not require the preservation of a "primitive" mantle reservoir over 4.5 Ga, and can potentially better reconcile increasing geochemical evidence of recycled lithospheric components in mantle plumes and seismic evidence for whole mantle convection.

Trieloff, Mario; Kunz, Joachim

2005-01-01

113

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

114

Characterization of air-sea gas exchange processes and dissolved gas/ice interactions using noble gases  

NASA Astrophysics Data System (ADS)

In order to constrain the processes controlling the cycles of biogeochemically important gases such as O2 and CO2, and thereby infer rates of biological activity in the upper ocean or the uptake of radiatively important ``greenhouse'' gases, the noble gases are used to characterize and quantify the physical processes affecting the dissolved gases in aquatic environments. The processes of vertical mixing, gas exchange, air injection, and radiative heating are investigated using a 2 year time-series of the noble gases, temperature, and meteorological data from Station S near Bermuda, coupled with a 1-dimensional upper ocean mixing model to simulate the physical processes in the upper ocean. The rate of vertical mixing that best simulates the thermal cycle is 1.1 +/- 0.1 × 10-4 m s-1. The gas exchange rate required to simulate the data is consistent with the formulation of Wanninkhof (1992) to +/-40%, while the formulation of Liss and Merlivat (1986) must be increased by a factor of 1.7 +/- 0.6. The air injection rate is consistent with the formulation of Monahan and Torgersen (1991) using an air entrainment velocity of 3 +/- 1 cm s-1. Gas flux from bubbles is dominated on yearly time-scales by larger bubbles that do not dissolve completely, while the bubble flux is dominated by complete dissolution of bubbles in the winter at Bermuda. In order to obtain a high-frequency time-series of the noble gases to better parameterize the gas flux from bubbles, a moorable, sequential noble gas sampler was developed. Preliminary results indicate that the sampler is capable of obtaining the necessary data. Dissolved gas concentrations can be significantly modified by ice formation and melting, and due to the solubility of He and Ne in ice, the noble gases are shown to be unique tracers of these interactions. A three-phase equilibrium partitioning model was constructed to quantify these interactions in perennially ice-covered Lake Fryxell, and this work was extended to oceanic environments. Preliminary surveys indicate that the noble gases may provide useful and unique information about interactions between water and ice. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Hood, Eda Maria

115

Testing The Noble Gas Paleothermometer With A Year-long Study Of Groundwater Noble Gases In An Instrumented Monitoring Well  

NASA Astrophysics Data System (ADS)

We report the results of a year-long noble gas study conducted in 2008 and early 2009, together with a wealth of continuous physical and chemical measurements collected in an instrumented monitoring well in the unconfined Glacial Drift aquifer in southern Michigan. Physical and chemical parameters at or near the water table are correlated with noble gas concentrations, corresponding noble gas temperatures (NGTs) and precipitation events. This year-long study is the first noble gas field test that has employed natural recharge, in situ monitored conditions, with minimal disturbance of the unsaturated zone. This study is unprecedented and demonstrates that there can be significant changes in physical and chemical conditions near the water table, over the space of a year, that can have profound effects on noble gas concentrations and hence, NGTs. The year-long record of conditions in the monitoring well show broad seasonal variations in pH, salinity, water temperature and water table depth. Results show that although precipitation events are detected within hours at the water table, there are significant pressure differences that persist for days at the water table, which argues for a very long time constant for gas transport within the unsaturated zone. There is strong evidence for the depletion of oxygen near the water table, which affects the noble gas air saturated water (ASW) component. When strongly reducing conditions prevail, as indicated by ORP, there is evidence for significant noble gas degassing. A major recharge event during the passage of the remnants of Hurricane Ike in the late summer 2008 caused a significant shift in H and O isotope ratios and it injected a large quantity of excess air into the groundwater. Hurricane Ike also appears to have caused a long-term change in the soil gas composition in the unsaturated zone, likely leading to a much more oxygen rich environment. Although individual competing NGT models can account for noble gas concentrations over portions of the record, no single NGT model can consistently account for all features observed over the entire year-long study. It is likely that the NGT temperature proxy must be viewed as an average of significant recharge conditions over the span of several years.

Castro, M. C.; Hall, C. M.; Lohmann, K. C.; Sun, T.

2011-12-01

116

Regularities And Irregularities Of The Stark Parameters For Single Ionized Noble Gases  

NASA Astrophysics Data System (ADS)

Spectroscopy of ionized noble gases has a great importance for the laboratory and astrophysical plasmas. Generally, spectra of inert gases are important for many physics areas, for example laser physics, fusion diagnostics, photoelectron spectroscopy, collision physics, astrophysics etc. Stark halfwidths as well as shifts of spectral lines are usually employed for plasma diagnostic purposes. For example atomic data of argon krypton and xenon will be useful for the spectral diagnostic of ITER. In addition, the software used for stellar atmosphere simulation like TMAP, and SMART require a large amount of atomic and spectroscopic data. Availability of these parameters will be useful for a further development of stellar atmosphere and evolution models. Stark parameters data of spectral lines can also be useful for verification of theoretical calculations and investigation of regularities and systematic trends of these parameters within a multiplet, supermultiplet or transition array. In the last years, different trends and regularities of Stark parameters (halwidths and shifts of spectral lines) have been analyzed. The conditions related with atomic structure of the element as well as plasma conditions are responsible for regular or irregular behaviors of the Stark parameters. The absence of very close perturbing levels makes Ne II as a good candidate for analysis of the regularities. Other two considered elements Kr II and Xe II with complex spectra present strong perturbations and in some cases an irregularities in Stark parameters appear. In this work we analyze the influence of the perturbations to Stark parameters within the multiplets.

Peláez, R. J.; Djurovic, S.; Cirišan, M.; Aparicio, J. A.; Mar S.

2010-07-01

117

Noble gas isotopic compositions of deep carbonate rocks from the Tarim Basin  

Microsoft Academic Search

Abundances and isotopic compositions of noble gases (He, Ne, Ar, Kr) with various existence states in carbonate rocks from\\u000a the Tacan1 Well have been investigated by means of the stepwise heating technique. The elemental abundance patterns of noble\\u000a gases in the samples show the enrichment of heavy noble gases and depletion of 20Ne relative to the atmosphere, which are designated

Shixin Zhou; Xianren Ye

2002-01-01

118

Neuroprotection (and lack of neuroprotection) afforded by a series of noble gases in an in vitro model of neuronal injury.  

PubMed

Xenon-induced neuroprotection has been well studied both in vivo and in vitro. In this study, the neuroprotective properties of the other noble gases, namely, krypton, argon, neon and helium, were explored in an in vitro model of neuronal injury. Pure neuronal cultures, derived from foetal BALB/c mice cortices, were provoked into injury by oxygen and glucose deprivation (OGD). Cultures were exposed to either nitrogen hypoxia or noble gas hypoxia in balanced salt solution devoid of glucose for 90min. The cultures were allowed to recover in normal culture medium for a further 24h in nitrogen or noble gas. The effect of noble gases on cell reducing ability in the absence of OGD was also investigated. Cell reducing ability was quantified via an MTT assay and expressed as a ratio of the control. The OGD caused a reduction in cell reducing ability to 0.56+/-0.04 of the control in the absence of noble gas (p<0.001). Like xenon (0.92+/-0.10; p<0.001), neuroprotection was afforded by argon (0.71+/-0.05; p<0.01). Neon and krypton did not have a protective effect under our experimental conditions. Helium had a detrimental effect on the cells. In the absence of OGD, krypton reduced the reducing ability of uninjured cells to 0.84+/-0.09 (p<0.01), but argon showed an improvement in reducing ability to 1.15+/-0.11 (p<0.05). Our data suggest that the cheap and widely available noble gas argon may have potential as a neuroprotectant for the future. PMID:19500647

Jawad, Noorulhuda; Rizvi, Maleeha; Gu, Jianteng; Adeyi, Olar; Tao, Guocai; Maze, Mervyn; Ma, Daqing

2009-06-07

119

Noble gases as proxies of mean ocean temperature: sensitivity studies using a climate model of reduced complexity  

NASA Astrophysics Data System (ADS)

Past global mean ocean temperature may be reconstructed from measurements of atmospheric noble gas concentrations in ice core bubbles. Assuming conservation of noble gases in the atmosphere-ocean system, the total concentration within the ocean mostly depends on solubility which itself is temperature dependent. Therefore, the colder the ocean, the more gas can be dissolved and the less remains in the atmosphere. Here, the characteristics of this novel paleoclimatic proxy are explored by implementing krypton, xenon, argon, and N2 into a reduced-complexity climate model. The relationship between noble gas concentrations and global mean ocean temperature is investigated and their sensitivities to changes in ocean volume, ocean salinity, sea-level pressure and geothermal heat flux are quantified. We conclude that atmospheric noble gas concentrations are suitable proxies of global mean ocean temperature. Changes in ocean volume need to be considered when reconstructing ocean temperatures from noble gases. Calibration curves are provided to translate ice-core measurements of krypton, xenon, and argon into a global mean ocean temperature change. Simulated noble gas-to-nitrogen ratios for the last glacial maximum are ?Kratm = -1.10‰, ?Xeatm = -3.25‰, and ?Aratm = -0.29‰. The uncertainty of the krypton calibration curve due to uncertainties of the ocean saturation concentrations is estimated to be ±0.3 °C. An additional ±0.3 °C uncertainty must be added for the last deglaciation and up to ±0.4 °C for earlier transitions due to age-scale uncertainties in the sea-level reconstructions. Finally, the fingerprint of idealized Dansgaard-Oeschger events in the atmospheric krypton-to-nitrogen ratio is presented. A ?Kratm change of up to 0.34‰ is simulated for a 2 kyr Dansgaard-Oeschger event, and a change of up to 0.48‰ is simulated for a 4 kyr event.

Ritz, Stefan P.; Stocker, Thomas F.; Severinghaus, Jeffrey P.

2011-12-01

120

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., Blättler, 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

121

Relativistic contributions to single and double core electron ionization energies of noble gases  

SciTech Connect

We have performed relativistic calculations of single and double core 1s hole states of the noble gas atoms in order to explore the relativistic corrections and their additivity to the ionization potentials. Our study unravels the interplay of progression of relaxation, dominating in the single and double ionization potentials of the light elements, versus relativistic one-electron effects and quantum electrodynamic effects, which dominate toward the heavy end. The degree of direct relative additivity of the relativistic corrections for the single electron ionization potentials to the double electron ionization potentials is found to gradually improve toward the heavy elements. The Dirac-Coulomb Hamiltonian is found to predict a scaling ratio of {approx}4 for the relaxation induced relativistic energies between double and single ionization. Z-scaling of the computed quantities were obtained by fitting to power law. The effects of nuclear size and form were also investigated and found to be small. The results indicate that accurate predictions of double core hole ionization potentials can now be made for elements across the full periodic table.

Niskanen, J. [Department of Physics, University of Oulu, Box 3000, 90014 Oulu (Finland); Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-106 91 Stockholm (Sweden); Norman, P. [Linkoeping University, SE-581 83 Linkoeping (Sweden); Aksela, H. [Department of Physics, University of Oulu, Box 3000, 90014 Oulu (Finland); Aagren, H. [Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, SE-106 91 Stockholm (Sweden)

2011-08-07

122

Relativistic contributions to single and double core electron ionization energies of noble gases  

NASA Astrophysics Data System (ADS)

We have performed relativistic calculations of single and double core 1s hole states of the noble gas atoms in order to explore the relativistic corrections and their additivity to the ionization potentials. Our study unravels the interplay of progression of relaxation, dominating in the single and double ionization potentials of the light elements, versus relativistic one-electron effects and quantum electrodynamic effects, which dominate toward the heavy end. The degree of direct relative additivity of the relativistic corrections for the single electron ionization potentials to the double electron ionization potentials is found to gradually improve toward the heavy elements. The Dirac-Coulomb Hamiltonian is found to predict a scaling ratio of ~4 for the relaxation induced relativistic energies between double and single ionization. Z-scaling of the computed quantities were obtained by fitting to power law. The effects of nuclear size and form were also investigated and found to be small. The results indicate that accurate predictions of double core hole ionization potentials can now be made for elements across the full periodic table.

Niskanen, J.; Norman, P.; Aksela, H.; A?Gren, H.

2011-08-01

123

A Method for the Determination of Isotopic and Elemental Abundances for Volatiles and Noble Gases in the Martian Surface Layer and Atmosphere  

Microsoft Academic Search

We describe a prototype gas enrichment device that, when coupled with a mass spectrometer, can be used for the in-situ measurement of volatiles and noble gases in the martian atmosphere and surface layer.

D. T. Young; J. H. Waite Jr.; G. P. Miller; D. S. Bass

1999-01-01

124

A Method for the Determination of Isotopic and Elemental Abundances for Volatiles and Noble Gases in the Martian Surface Layer and Atmosphere  

NASA Astrophysics Data System (ADS)

We describe a prototype gas enrichment device that, when coupled with a mass spectrometer, can be used for the in-situ measurement of volatiles and noble gases in the martian atmosphere and surface layer.

Young, D. T.; Waite, J. H., Jr.; Miller, G. P.; Bass, D. S.

1999-03-01

125

Diagnostics of dielectric barrier discharges in noble gases: atmospheric pressure glow and pseudoglow discharges and spatio-temporal patterns  

Microsoft Academic Search

We present experimental results of atmospheric pressure glow discharges (APGD) in a dielectric barrier discharge reactor. These are examined in different noble gases and in the N2\\/O2 system (air and pure N2), under varying experimental conditions (frequency f; gap length d; and electric field intensity E). Discharge diagnostics have been carried out using ultrahigh speed imaging, and synchronous dual-detection of

Ion Radu; Ray Bartnikas; Grzegorz Czeremuszkin; Michael R. Wertheimer

2003-01-01

126

Absolute cross sections for electron loss, electron capture, and multiple ionization in collisions of C3+ with noble gases  

Microsoft Academic Search

Absolute charge-state-correlated cross sections for projectile electron loss, electron capture, and target multiple ionization in collisions between C3+ ions and noble gases have been measured for energies between 1.3 and 3.5 MeV. The data have been compared with other similar absolute cross sections existent in the literature for several projectiles. Calculations for the single-loss-multiple-ionization channel have been performed for the

A. C. F. Santos; G. M. Sigaud; W. S. Melo; M. M. Sant'Anna; E. C. Montenegro

2010-01-01

127

Noble Gases in the Lunar Meteorites Calcalong Creek and QUE 93069  

NASA Astrophysics Data System (ADS)

Although the world's collections contain comparable numbers of martian and lunar meteorites (about 10 each), their ejection histories seem to be quite different [1]. We have sampled no more than four martian craters, but almost every one of the lunar meteorites apparently represents a separate cratering event. Furthermore, most lunar meteorites were apparently ejected from the top meter of the surface, unlike any of the martian meteorites. We have measured noble gases in two bulk samples of the lunar meteorite QUE93069 and three of Calcalong Creek, ranging in size from 7 to 15 mg. Averaged results are given in Table 1. Both meteorites contain solar-wind-implanted noble gas. QUE 93069, which is a mature anorthositic regolith breccia [2], contains amounts comparable to the most gas-rich lunar meteorites. The relatively low 40Ar/36Ar ratios of both meteorites suggest surface exposures no more than 2.5 Ga ago [3]. Calcalong Creek has readily observable spallogenic gas. The 131Xe/126Xe ratio of 4.8+/-0.3 corresponds to an average shielding depth of slightly more than 40 gm/cm^2 [4]. In common with many lunar breccias, Calcalong Creek has been exposed to cosmic rays for several hundred Ma (calculations based on [4] and [5]). The 3He apparent exposure age is much shorter, suggesting diffusive loss of He. To determine the detailed exposure history, it is necessary to have measurements of cosmogenic radionuclides. Our samples were too small to measure 81Kr, but [6] have measured 10Be, 26Al and 36Cl. Their data are consistent with either extended exposure at <70 gm/cm^2 in the lunar regolith followed by a short (200,000 years) transit to Earth, or with ejection from several meters depth about 2 Ma ago [6]. Our data, requiring several hundred Ma of exposure at an average depth of 40-50 gm/cm^2, are clearly more consistent with the first scenario. The only other lunar meteorite which could have been ejected at the same time is MAC 88104/5 [1], but the chemical differences between the two make it highly unlikely that they come from the same event. It is difficult to determine the amount of spallogenic gas in QUE 93069 because of the huge solar wind signature. However, a few isotopes that are normally dominated by spallation (3He, 21Ne, 80Kr and 126Xe) are enhanced by >1 sigma over solar wind values, although in every case the spallogenic gas is <25% of the total. The exposure ages derived [4,7] are comparable to those for Calcalong Creek, consistent with extensive near-surface lunar exposure. However, 131Xe is within 1 sigma of solar wind, so we can not constrain the average shielding depth. Measurements on separated clasts would be probably be required. In summary, both meteorites have typical exposure histories for lunar meteorites. Both contain solar wind gases and high cosmogenic noble gas contents suggesting ejection from near the lunar surface. We can not adequately constrain the ejection event for QUE 93069, but Calcalong Creek appears to be the only meteorite from its impact event. References: [1] Warren P. H. (1994) Icarus, 111, 338-363. [2] Lindstrom M. M. et al. (1995) LPS XXVI, 849-850. [3] McKay D. S. et al. (1986) Proc. LPSC 16th, in JGR, 91, D277-D303. [4] Hohenberg C. M. et al. (1978) Proc. LPSC 9th, 2311-2344. [5] Hill C. H. et al. (1991) Nature, 352, 614-617. [6] Nishiizumi K. et al. (1992) Meteoritics, 27, 270. [7] Kring D. A. et al. (1995) Meteoritics, submitted.

Swindle, T. D.; Burkland, M. K.; Grier, J. A.

1995-09-01

128

Index of refraction for cold lithium- and diatomic sodium waves traveling through cold noble gases  

NASA Astrophysics Data System (ADS)

In the present paper we propose to measure the index of refraction for diatomic sodium molecules traveling through a cold helium gas. Theoretical calculations of the index of refraction for this system are presented as a function of the molecule velocity and atom gas temperature. Whereas previous theoretical efforts to compute the refractive index have been concerned with atomic systems and atomic matter waves, we extend the investigation to diatomic molecules in the present work. To enable such calculations the potential energy surface for the atom-molecule interaction is calculated ab initio, along with the long range dispersion coefficients for the atom-molecule system. The full close-coupled equations, describing the atom-molecule collisions, are solved numerically to work out the influence of the collisions on the matter waves. We investigate the sensitivity of the results upon changes and inaccuracies in the potential energy surface. Several molecular rotational levels are included in the present study, and the index of refraction is found to depend on the rotational state. In addition, the index of refraction for atomic lithium matter waves traveling through the cold noble gases helium and argon are computed, motivated by a recent experiment with atomic lithium matter waves. Different resonances (glory- and scattering resonances) are identified from the results. Such resonances offer an important opportunity for the comparison of experiment and theory.

Bjørgen, H.; Lysebo, M.; Veseth, L.

2011-02-01

129

Combustion vs. Pyrolysis of Presolar Diamonds: Association of P3 and HL Noble Gases with Carbon  

NASA Astrophysics Data System (ADS)

Since it became clear that presolar diamonds are not identical and perhaps consist of several carriers of isotopically anomalous (like HL-Xe and light nitrogen) and isotopically normal (carbon and P3 noble gases) components, it is important to know how these components are related to the diamond carriers. Because of diamond grains are too small to be analyzed individually and the attempts to separate the diamonds [1] have had little, if any, success, the only method currently available to investigate the relationship between the carriers and corresponding components is the temperature dependence of their release pattern. The interpretation of the latter however is often not straight forward because the mechanism by which the gases are released is complicated and simultaneously involves several processes such as diffusion, chemical reactions between coexisting phases and/or their heating environment and phase transformations [2, 3]. To unravel this interdependent matrix we use several extraction methods applied to the same sample. In the present study we used a combination of stepped pyrolysis and combustion for investigation of the release pattern of Ar components for presolar diamonds concentrated from CI (Orgueil), and CV (Allende, Efremovka) meteorites. From the previous studies [2] it is known that Ar in the most primitive CI's and CM's meteorites consists mostly of P3 component while for CV3's like Allende and Efremovka it is represented mainly by HL component. This difference in the noble gas components composition probably reflects the thermal history of the corresponding parent bodies and the extreme sensitivity of the P3 component concentrations, in presolar diamonds, to the thermal metamorphism. Laboratory pyrolysis experiments show that most of the P3 argon is released at rather low temperature though some of the gas is still being liberated at temperatures as high as those usually associated with HL component [2]. The low release temperatures have led to the idea that P3 noble gases are located near the surface of the diamond grains which is destroyed by pyrolytically induced chemical reactions with surface bonded H atoms [2]. However the same authors did not comment on the high temperature part of the P3 release. Our previous investigations [4] however have clearly showed that the release of P3 component during pyrolysis is accompanied by of 8-15% of C present in the form of CO+C02. This observation is in agreement with the amount of oxygen which can be adsorbed on the surface of diamond grains. The evolution of C02+CO is in any case independent of whether or not external oxygen is used for the extraction. Analysis of a high resolution release pattern of 36Ar from Orgueil shows (Fig.) that it is bimodal and similar for pyrolysis and combustion. There is a fraction of P3 Ar (~40%) which is released at low temperature apparently by diffusion before the carbon begins to combust. The rest of the P3 Ar in the case of combustion, and another 40 - 50% in the case of pyrolysis, is released in close association with release of carbon. We conclude that the P3 component has a complicated nature and some difference in the isotopic composition of its constituents may be suggested. It is important to note that release of Ar P3 occurs over the whole temperature range of diamond combustion (450-600 degrees C) independent of how much oxygen is available (Fig.). This is evidence against a location of P3 gases on the surface of the diamond grains but suggests a separate camer for the component. The release of about 10% of P3 gases at very high temperature during pyrolysis [2] can be simply explained if the amount of the oxygen associated with the sample is not enough to oxidize all the P3-containing grains. The release of P3 gases together with HL component contradicts their surface location. We believe these is now a strong case for P3 gas (Ar at least) in Orgueil being associated with a distinct type of grain which constitutes ~10% by weight of the carbon. In contrast to the above a high resolution stepped combustion extract

Verchovsky, A. B.; Fisenko, A. V.; Pillinger, C. T.

1995-09-01

130

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

131

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

PubMed

Recent studies on the formation of XH(3)(+) 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 H(3)(+). It is the context in which the possibility for clustering with more than one noble gas (X(n)H(3)(+) 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 H(3)(+) triangle. The binding energy of the nth atom, defined as the X(n)H(3)(+) --> X(n-1)H(3)(+) + 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 H(3)(+) 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 H(3)(+) abundance is small. PMID:19425782

Pauzat, F; Ellinger, Y; Pilmé, J; Mousis, O

2009-05-01

132

Seawater-Derived Noble Gases and Halogens Preserved in Peridotite and Eclogite from the Subduction-Type Sanbagawa Metamorphic Belt  

Microsoft Academic Search

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, Earth Planet. Sci. Lett. 89, 173-183). Nevertheless, subduction of sediment and seawater-dominated pore fluids to the deep mantle has been proposed to account for heavy noble gas (Ar, Kr and Xe) non-radiogenic

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

2010-01-01

133

Extraction of Solar Wind Nitrogen and Noble Gases From the Genesis Gold Foil Collector  

NASA Astrophysics Data System (ADS)

The Genesis gold foil is a bulk solar wind collector, integrating fluences from all three of the wind regimes. Pyrolytic extraction of small foil samples at Minnesota yielded He fluences, corrected for backscatter, in good agreement with measurements by on-board spacecraft instruments, and He/Ne elemental ratios close to those implanted in collector foils deployed on the lunar surface during the Apollo missions. Isotopic distributions of He, Ne and Ar are under study. Pyrolysis to temperatures above the gold melting point generates nitrogen blanks large enough to obscure the solar-wind nitrogen component. An alternative technique for nitrogen and noble gas extraction, by room-temperature amalgamation of the gold foil surface, will be discussed. Ne and Ar releases in preliminary tests of this technique on small foil samples were close to 100% of the amounts expected from the high-temperature pyrolysis yields, indicating that amalgamation quantitatively liberates gases from several hundred angstroms deep in the gold, beyond the implantation depth of most of the solar wind. Present work is focused on two problems currently interfering with accurate nitrogen measurements at the required picogram to sub-picogram levels: a higher than expected blank likely due to tiny air bubbles rolled into the gold sheet during fabrication, and the presence of a refractory hydrocarbon film on Genesis collector surfaces (the "brown stain") that, if left in place on the foil, shields the underlying gold from mercury attack. We have found, however, that the film is efficiently removed within tens of seconds by oxygen plasma ashing. Potential nitrogen contaminants introduced during the crash of the sample return canister are inert in amalgamation, and so are not hazards to the measurements.

Schlutter, D. J.; Pepin, R. O.

2005-12-01

134

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

SciTech Connect

Gold Basin is a large L4 chondrite shower, that was recently discovered in the Mojave Desert, Arizona [1]. Based on {sup 109}Be and {sup 14}C concentrations in several fragments, the pre-atmospheric radius of this shower was estimated to be 3-4 meters [2]. Among chondrites, Gold Basin is one of the largest, thus providing a unique opportunity for comparing measured cosmogenic nuclide concentrations with model calculations for large objects. Noble gas measurements combined with {sup 10}Be data of most Gold Basin samples suggest a single-stage exposure of 15-30 Myr, although a few samples may require a complex exposure history [3]. We selected eight samples of the Gold Basin shower that were analyzed for noble gases; these samples represent a wide range of shielding depths.

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

2001-04-30

135

Absolute cross sections for electron loss, electron capture, and multiple ionization in collisions of C3+ with noble gases  

NASA Astrophysics Data System (ADS)

Absolute charge-state-correlated cross sections for projectile electron loss, electron capture, and target multiple ionization in collisions between C3+ ions and noble gases have been measured for energies between 1.3 and 3.5 MeV. The data have been compared with other similar absolute cross sections existent in the literature for several projectiles. Calculations for the single-loss-multiple-ionization channel have been performed for the screening mode, using both an extended version of the classical-impulse free-collision model and the plane-wave Born approximation (PWBA), and for the antiscreening mode within the PWBA. The energy dependence of the average number of target active electrons which contribute to the antiscreening has been described by means of a simple function, which is “universal” for noble gases but, in principle, projectile dependent. A method has been developed to obtain the number of active target electrons for each subshell in the high-velocity regime, which presented physically reasonable results. Analyses of the dependences of the single-capture and transfer-ionization (SC and TI, respectively) processes on the projectile charge states showed that, for He, equally charged bare and dressed projectiles have very similar cross sections; the latter thus acting as structureless point charges. A behavior similar to that in the SC has been observed for the pure single ionization of He by projectiles with different charge states and of the other noble gases by singly charged projectiles. It has been shown that the q2 dependence of the pure-single and total-ionization cross sections, predicted by first-order models, is only valid for high-collision velocities. For slower collisions, the electron capture process becomes more relevant and competes with the ionization channel, a feature which grows in importance as the projectile charge state increases.

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

2010-07-01

136

Elliptical Polarization Favors Long Quantum Orbits in High-Order Above-Threshold Ionization of Noble Gases  

NASA Astrophysics Data System (ADS)

We demonstrate the significant role of long quantum orbits in strong-field atomic processes by investigating experimentally and theoretically the above-threshold ionization spectra of noble gases in intense elliptically polarized laser pulses. With increasing laser ellipticity, the yields of different energy regions of the measured electron spectrum in high-order above-threshold ionization drop at different rates. The experimental features can be reproduced by a theoretical simulation based on quantum-orbit theory, revealing that increasing ellipticity favors the contributions of the long quantum orbits in the high-order above-threshold ionization process.

Lai, XuanYang; Wang, ChuanLiang; Chen, YongJu; Hu, ZiLong; Quan, Wei; Liu, XiaoJun; Chen, Jing; Cheng, Ya; Xu, ZhiZhan; Becker, Wilhelm

2013-01-01

137

Concentrations and isotope ratios of helium and other noble gases in the Earth's atmosphere during 1978-2011  

NASA Astrophysics Data System (ADS)

The evolution of the atmospheric noble gas composition during the past few decades has hardly been studied because, in contrast to many other atmospheric gases, systematic time-series measurements have not been available. Based on theoretical considerations, the atmospheric noble gas isotope composition is assumed to be stable on time scales of up to about 106 yrs, with the potential exception of anthropogenic changes predicted for the He concentration and the 3He/4He ratio. However, experimental assessments of the predicted changes in the atmospheric He isotope composition are controversial. To empirically test these assumptions and predictions, we analysed the noble gas isotope composition in samples of the Cape Grim Air Archive, a well-defined archive of marine boundary layer air in the southern hemisphere. The resulting time series of the 20Ne, 40Ar, 86Kr and 136Xe concentrations and 20Ne/22Ne and 40Ar/36Ar ratios during 1978-2011 demonstrate the stability of the atmospheric Ne, Ar, Kr and Xe composition during this time interval. The He isotope data indicate a decrease in the 3He/4He during the same time interval at a mean rate of 0.23-0.30‰ per yr. This result is consistent with most model predictions of the rate of decrease in the atmospheric 3He/4He ratio associated with mining and burning of fossil fuels.

Brennwald, Matthias S.; Vogel, Nadia; Figura, Simon; Vollmer, Martin K.; Langenfelds, Ray; Paul Steele, L.; Maden, Colin; Kipfer, Rolf

2013-03-01

138

Composition of solar wind noble gases released by surface oxidation of a metal separate from the Weston meteorite  

NASA Astrophysics Data System (ADS)

The paper reports on a set of experiments intended to test the feasibility of determining elemental and isotopic ratios of the noble gases and nitrogen in the solar wind in metal separates from gas-rich ordinary chondrites. Helium, neon, and argon show clear evidence of a solar wind signature, while no solar component could be identified for xenon and nitrogen. Helium, neon, and argon elemental isotopic ratios appear to depend on depth within the metal grains. The ratios derived indicate that the Weston meteorite did not acquire its solar wind gases from a recent exposure to solar wind, but more probably at a time in the past similar to or even earlier than the exposure time of Apollo 17 breccias. The Ar-36/Ar-38 ratio, in tandem with other recent determinations of this value, indicates that the solar and terrestrial values can no longer be assumed to be equivalent.

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

1991-04-01

139

Ultrahigh Sensitivity Heavy Noble Gas Detectors for Long-Term Monitoring and for Monitoring Air  

SciTech Connect

The primary objective of this research project is to develop heavy noble gas (krypton, xenon, and radon) detectors for (1) long-term monitoring of transuranic waste, spent fuel, and other uranium and thorium bearing wastes and (2) alpha particle air monitors that discriminate between radon emissions and other alpha emitters. DOE needs that are addressed by this project include improved long-term monitoring capability and improved air monitoring capability during remedial activities. Successful development and implementation of the proposed detection systems could significantly improve current capabilities with relatively simple and inexpensive equipment.

John D. Valentine

2005-07-28

140

Noble Gases in the Light and Dark Phase of a Meteorite Found in Novato, California  

NASA Astrophysics Data System (ADS)

We present noble gas results on a solar wind free chondrite found with the help of a dedicated camera network near Novato, CA. The results are typical for L6 chondritic material that has experienced the parent body disruption 470 Ma ago.

Busemann, H.; Clay, P. L.; Jenniskens, P.; Meier, M. M. M.; Wieler, R.

2013-09-01

141

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

142

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

143

Variation of superconducting transition temperatures of transition-metal thin films deposited with the noble gases  

Microsoft Academic Search

Thin films of Cr, Mo, Ti, W, and Zr metals deposited by dc ion-beam sputtering in noble-gas atmospheres were found to be superconducting with transition temperatures substantially higher than those observed for the respective bulk metals. Mo films deposited with a Xe ion beam were found to be superconducting at a temperature of 7.2°K. A variation of Tc was observed

P. H. Schmidt; R. N. Castellano; H. Barz; A. S. Cooper; E. G. Spencer

1973-01-01

144

Double clathrate hydrates of cross-linked tetrabutylammonium polyacrylate and noble gases at high pressures  

Microsoft Academic Search

Temperatures of hydrate decomposition were measured by means of the differential thermal analysis at a pressures up to 800–900 Mpa\\u000a in the systems: cross-linked tetrabutylammonium polyacrylate–water and cross-linked tetrabutylammonium polyacrylate–water–noble\\u000a gas (He, Ne, Ar, Kr, Xe). The effect of the deformation of D- cavities of the hydrates on the temperature of their decomposition is discussed on the basis of the experimental

E. Ya. Aladko; E. G. Larionov; A. Yu. Manakov; I. S. Terekhova

2010-01-01

145

Sequestration of Noble Gases by H+3 in Protoplanetary Disks and Outer Solar System Composition  

Microsoft Academic Search

We study the efficiency of the noble gas sequestration by the ion H+3 in the form of XH+3 complexes (with X=argon, krypton, or xenon) in gas-phase conditions similar to those encountered during the cooling of protoplanetary disks. We show that XH+3 complexes form very stable structures in the gas phase and that their binding energies are much higher than those

O. Mousis; F. Pauzat; Y. Ellinger; C. Ceccarelli

2008-01-01

146

On the pressure dependence of the polarization of diamagnetic muons and muonium in pure noble gases: Is there a missing fraction?  

Microsoft Academic Search

The amplitudes of the signals in ?SR exhibit pressure dependencies which are associated with the stopping dynamics of muonium atoms and diamagnetic muon species observed when muons are thermalized in pure noble gases. To explain this effect, a set of coupled rate equations, with time dependent rates and based upon quantal Boltzmann equations, have been developed to describe the spin

Ralph Eric Turner; Masayoshi Senba

1986-01-01

147

Quantifying magmatic, crustal, and atmospheric helium contributions to volcanic aquifers using all stable noble gases: Implications for magmatism and groundwater flow  

Microsoft Academic Search

We measure all stable noble gases (He, Ne, Ar, Kr, Xe) in spring waters in the Oregon Cascades volcanic arc and in eastern Oregon, USA. We show that in order to estimate magmatic helium (He) contributions it is critical to simultaneously consider He isotopic ratios, He concentrations, and mixing of He components. Our component mixing analysis requires consideration of all

M. O. Saar; M. C. Castro; C. M. Hall; M. Manga; T. P. Rose

2005-01-01

148

Removal of Titan's noble gases by their trapping in its haze  

Microsoft Academic Search

Titan's haze, formed by photolysis of C2H2, C2H4 and HCN, was found experimentally to trap Ar, Kr and Xe with efficiencies of 3.5 × 10?4, 1.9 × 10?3 and 6.5 × 10?2 [noble gas atom]\\/[carbon atom] in the polymer, respectively. The rate of aerosol formation and settling down of 3 × 10?13?kg?m?2?s?1, as inferred from our experiments on CH4 photolysis

Ronen Jacovi; Akiva Bar-Nun

2008-01-01

149

Comparative study of the collisional electron detachment of C-, Si-, and Ge- by light noble gases  

NASA Astrophysics Data System (ADS)

Collisional electron detachment of anions with np3 structures (n=2, 3, and 4), namely, C-, Si-, and Ge-, was studied for He, Ne, and Ar targets and relative velocities ranging from 0.2 a.u. to 2.2 a.u.. Single, double, and triple electron ejection cross sections were also measured for the C- anion colliding with an Ar target, being observed to obey a binomial distribution. Two striking universal features were observed concerning the total detachment cross sections: for each target a multiplicative scaling may be made for the cross sections of the three projectiles, and these factors are target independent. The maxima of these three curves show a nonmonotonic correspondence with the noble-gas atomic numbers. A simple law, proposed for the scaling, indicates the presence of metastable states in the Si- and Ge- beams.

Luna, H.; Zappa, F.; Martins, M. H.; Magalhães, S. D.; Jalbert, Ginette; Coelho, L. F.; de Castro Faria, N. V.

2001-05-01

150

A Single Lodranite/Acapulcoite Parent Body: Noble Gases in Lodranite QUE 93148 and Acapulcoite ALH 81261  

NASA Astrophysics Data System (ADS)

We continue our comprehensive studies of the cosmic ray exposure history of lodranites [1] to include new noble gas measurements in the QUE 93148 lodranite and the ALH 81261 acapulcoite. In addition, we model the production rates of cosmogenic nuclides in lodranites and acapulcoites using the HERMES high energy transport code [2], in order to test whether conventional production rates can be extrapolated to this group of small meteoroids which reveal very large values of the shielding parameter 22Ne/21Ne (Table 1). The model calculations are based on the same excitation functions of p- and n-induced reactions as used in recent calculations [3,4]. We extended our studies to acapulcoites, since petrologic, mineralogic, and O-isotopic investigations [5] as well as chemical investigations [6] suggest that lodranites and acapulcoites are residues of varying degree of partial melting, consistent with an origin on a common parent body. Whether a collisional event on the common parent body ejected both types of meteorites can be investigated by an analysis of the transfer times to Earth, specifically their cosmic-ray exposure ages. Because the contents of trapped He, Ne, and Ar in lodranites and acapulcoites are very low we can derive reliable cosmogenic noble gas contents. Using the composition-adjusted production rates for cosmogenic noble gases in achondrites [7], and adopting the shielding-parameter dependence for H-chondrites the exposure ages of [1] are obtained. For lodranites these exposure ages overlap those calculated [8] from 26Al and 10Be measurements. For the acapulcoites our exposure ages agree with those [5] calculated with the Graf-model [9], as well as with the shielding-independent exposure age for Acapulco that is based on the 36Cl-36Ar method[10]. The large spread in the exposure ages can be attributed to the highly variable target element abundances, as multiple measurements on several aliquots show unusually large variations. The fact that the average exposure age T3 is 44% higher than the average T21 in the case of lodranites, and 13% higher for acapulcoites, cannot be explained by the variable chemical composition. Studies of Lodran mineral separates [1] suggest that the Lodran parent meteoroid was enriched in metal (up to 65%). This means that the Ne production rates for bulk samples are overestimated. The average cosmogenic noble gas contents, average shielding, and main target element abundances of lodranites and acapulcoites (Table 1) coincide fairly well. The slightly higher Mg abundance in lodranites translates into a higher Ne production rate and therefore a lower exposure age T21. The higher Ca abundance in acapulcoites leads to a higher Ar production rate and, therefore, a lower T38. The production of cosmogenic 3He, however, is quite insensitive to variations in chemical composition and shielding. We observe good agreement between the T3 values of lodranites (6.2+/-0.5Ma) and acapulcoites (6.8+/-1.1Ma) and conclude that a single collisional event can account for the currently known exposure ages of lodranites and acapulcoites. Acknowledgments: We thank NASA and the MWG for the meteorite samples. This work was supported by the Swiss NSF and partially by the Deutsche Forschungsgemeinschaft. References: [1] Weigel A. et al. (1994) Meteoritics, 29, 548. [2] Cloth P. et al. (1988) JUEL-2203. [3] Michel R. et al. (1995) Planet. Space Sci., in press. [4] Herpers U. et al. (1995) Planet. Space Sci., in press. [5] McCoy T. J. et al. (1995) GCA, submitted. [6] Zipfel J. and Palme H. (1993) LPS XXIV, 1579. [7] Eugster O. and Michel Th. (1995) GCA, 59, 177. [8] Xue et al. (1994) LPS XXV, 1523. [9] Graf Th. et al. (1990) GCA, 54, 2521. [10] Graf Th. et al., this volume. Table 1 shows average cosmogenic noble gas contents, main target element abundances, and exposure ages of eight lodranites and four acapulcoites.

Weigel, A.; Eugster, O.; Marti, K.; Michel, R.

1995-09-01

151

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

152

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

153

Absolute cross sections for electron loss, electron capture, and multiple ionization in collisions of C{sup 3+} with noble gases  

Microsoft Academic Search

Absolute charge-state-correlated cross sections for projectile electron loss, electron capture, and target multiple ionization in collisions between C{sup 3+} ions and noble gases have been measured for energies between 1.3 and 3.5 MeV. The data have been compared with other similar absolute cross sections existent in the literature for several projectiles. Calculations for the single-loss-multiple-ionization channel have been performed for

A. C. F. Santos; M. M. SantAnna; E. C. Montenegro; G. M. Sigaud; W. S. Melo

2010-01-01

154

Pressure dependence of the polarization of diamagnetic muons and muonium in pure noble gases: Is there a missing fraction  

SciTech Connect

The amplitudes of the signals in ..mu..SR exhibit pressure dependencies which are associated with the stopping dynamics of muonium atoms and diamagnetic muon species observed when muons are thermalized in pure noble gases. To explain this effect, a set of coupled rate equations, with time dependent rates and based upon quantal Boltzmann equations, have been developed to describe the spin dynamics for the thermalization of the two species. These, by definition positive, rates depend upon time through the translational single particle density operators associated with each species. Thus, to exactly solve the spin dynamics, the coupled kinetic Boltzmann equations for the stopping process must also be solved. Furthermore, the rate equations also contain spin dynamics generated by the muonium hyperfine interaction. It is the presence of this hyperfine interaction which leads to the loss of polarization for low pressure gases. The coupled quantal rate equations have been solved for a model of the stopping dynamics in which the rates, taken as square box functions of time, describe the charge exchange regime wherein muonium is both formed and ionized by subsequent collisions. Two post charge exchange extensions of this model are now considered. Following the charge exchange region, in the loss model, it is assumed that the rate of muonium formation is zero while the ionization rate is not. On the other hand, the capture model assumes that the ionization rate is zero while the muonium formation rate is not. Fits are presented to the available data for argon, krypton, xenon and neon. Since argon has both diamagnetic and paramagnetic signals then independent fits to each may be compared. A single set of fitting parameters has been found which describes both signals. This single fit requires a further extension of the models.

Turner, R.E.; Senba, M.

1986-04-01

155

Gradient-induced Longitudinal Relaxation of Hyperpolarized Noble Gases in the Fringe Fields of Superconducting Magnets Used for Magnetic Resonance  

PubMed Central

When hyperpolarized noble gases are brought into the bore of a superconducting magnet for magnetic resonance imaging (MRI) or spectroscopy studies, the gases must pass through substantial field gradients, which can cause rapid longitudinal relaxation. In this communication, we present a means of calculating this spatially dependent relaxation rate in the fringe field of typical magnets. We then compare these predictions to experimental measurements of 3He relaxation at various positions near a medium-bore 2-T small animal MRI system. The calculated and measured relaxation rates on the central axis of the magnet agree well and show a maximum 3He relaxation rate of 3.83 × 10?3 s?1 (T1 = 4.4 min) at a distance of 47 cm from the magnet isocenter. We also show that if this magnet were self-shielded, its minimum T1 would drop to 1.2 min. In contrast, a typical self-shielded 1.5-T clinical MRI scanner will induce a minimum on-axis T1 of 12 min. Additionally, we show that the cylindrically symmetric fields of these magnets enable gradient-induced relaxation to be calculated using only knowledge of the on-axis longitudinal field, which can either be measured directly or calculated from a simple field model. Thus, while most MRI magnets employ complex and proprietary current configurations, we show that their fringe fields and the resulting gradient induced relaxation are well approximated by simple solenoid models. Finally, our modeling also demonstrates that relaxation rates can increase by nearly an order of magnitude at radial distances equivalent to the solenoid radius.

Zheng, Wangzhi; Cleveland, Zackary I.; Moller, Harald E.; Driehuys, Bastiaan

2010-01-01

156

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

157

Noble gas anomalies and synthesis of the chemical elements  

Microsoft Academic Search

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

D. D. Sabu; O. K. Manuel

1980-01-01

158

Noble Gases in Alpine Gold: U/Th-He Dating and Excesses of Radiogenic He and AR  

NASA Astrophysics Data System (ADS)

Gold precipitates in hydrothermal fluids along with other heavy elements, such as Ag and Pt. In order to explore the possibility of dating the formation of gold we determined the concentrations of U, Th, and their decay product ^4He, as well as the K and ^40Ar concentrations in vein-type gold and in placer gold samples. The gold-quartz veins at Brusson in the south-western alps were formed approximately 32 Ma ago during an episode of tectonic uplift (Diamond, 1990). Alpine material was deposited as sediment layers in the region of central Switzerland and placer gold is thus relatively abundant in the rivers of the Napf area. We washed placer gold from the river Grosse Fontanne in 1990 and 1991. Placer gold that had been collected from the river Kruempelgraben in 1933 and a sample of vein-type free gold grown on quartz rock from the Brusson area (Val d'Ayas) have been obtained from the Museum of Natural History in Bern. Table 1 gives the results. Most of the ^4He is released above 1050 degrees C, that is when gold melts, indicating that gold is extremely well retentive for He. From the ^4He concentration of (269 +- 20) x 10^-8 cm^3 STP/g, (0.4 +- 0.1) ppm U, and (0.9 +- 0.3) ppm Th for vein-type gold we calculate a U/Th-He age of (36 +- 8)Ma. This age agrees within errors with the proposed age of 32 Ma. The data given in Table 1 show that all placer gold samples contain excesses of radiogenic ^4He and ^40Ar relative to the concentrations expected from the U/Th and K decay, respectively, if we assume a formation age of 32 Ma. The quartz sample is depleted in ^4He but strongly enriched in radiogenic ^40Ar. The excess of ^40Ar(sub)rad is easier to explain than that of ^4He. Vein-type gold and placer gold contain quartz inclusions (Schmid, 1973). The high ^40Ar(sub)rad content of quartz (Table 1) indicates that the ^40Ar(sub)rad excess of gold originates from quartz inclusions. Excess ^4He in gold must be of radiogenic origin. Taking ^20Ne and ^36Ar as a measure for the quantity of trapped atmospheric noble gases we estimate atmospheric ^4He in the gold samples to be three to five orders of magnitude below the observed ^4He concentration. Placer gold is finely distributed in rock material and might be exposed to an alpha-particle irradiation from neighboring U/Th-rich minerals. An alternative He source are inclusions of U/Th-rich minerals, such as zircon, either within the gold material or mechanically worked into the spangles as they were part of the river detritus. Acknowledgement: We thank the Swiss NSF for their support. References: Diamond L.W. (1990) Am. J. of Science 290, 912-958. Schmid K. (1973) Schw. Min. Petr. Mitt. 53, 125-156. Table 1, which in the hard copy appears here, shows concentrations of He, Ne, and Ar (10^-8 cm^3 STP/g) and of K, Th, and U (ppm) in vein-type free gold, placer gold, and quartz. The ^3He and ^21Ne signals were below detection limits, that is ^4He/^3He in gold is >100'000. Average ^20Ne/^22Ne ratios in gold and quartz are 10.2 +- 0.2, that is about 4% larger than in the terrestrial atmosphere. Average ^36Ar/^38Ar = 5.2 +- 0.2 (within errors identical to ^36Ar/^38Ar in air). 1) Sample sizes 50-100 mg. 2) Radiogenic ^40Ar = ^40Ar-295.5 x ^36Ar. 3) Calculated from U/Th and ^40K decay.

Eugster, O.; Hofmann, B.; Krahenbuhl, U.; Neuenschwander, J.

1992-07-01

159

Tracing the Galapagos Volcanic Groundwater System Using Noble Gases and Stable Isotopes  

NASA Astrophysics Data System (ADS)

Water samples were collected from springs and groundwater in the Galapagos Islands of San Cristobal and Santa Cruz and analyzed for He, Ne, Ar, Kr, and Xe concentrations and stable isotopes. One lake sample was also collected in San Cristobal and analyzed for the same elements. Noble gas temperatures (NGTs) were calculated for all samples for different assumed altitudes, and subsequently compared with possible temperature values within both islands. Many San Cristobal and Santa Cruz samples indicate recharge occurring at temperatures and altitudes which are consistent with those in place in the islands. Specifically, recharge altitudes between 229 and 730m and temperatures of 19.95 (±1.13) and 25.92 (±2.0)°C are found for San Cristobal, while recharge altitudes between 160 and 870m and temperatures between 20.05 (±2.07) and 27.12 (±0.47)°C are found for Santa Cruz, suggesting that these are the altitude and temperature range values at which recharge occurs in these two islands, respectively. Most samples which fall within expected altitude and temperature ranges are located at low altitudes (<~420m a.s.l) while all others are located at higher altitudes. Comparison of calculated NGTs of these low altitude samples to the average hot season (Jan-May) temperature along with the observed temperature gradient suggests that recharge occurs mostly during the hot season at low altitudes. Results also suggest that recharge likely occurs during both the hot and the Garua (June-December) seasons at high altitudes. ?D and ?18O were compared with volume-weighted mean monthly values for rainfall. All our samples fall within both stable isotope end-members, April and September. In particular, a set of samples lie close to the more depleted rainwater samples resulting from intense precipitation events during the hot season (Jan-May) and form the same subset of low altitude samples identified using NGTs. The stable isotopic composition of these water samples also suggest that recharge occurs mostly during the hot season at these low altitude locations. By contrast, the isotopic signature of high altitude samples lies between the subset of enriched Garua rainfall samples and that of the depleted hot season rainfall samples, strongly pointing to recharge during both seasons as previously suggested by NGTs. Our combined NGT and stable isotope analyses thus leads to a common conclusion, i.e., samples predominantly recharged during the hot season are found at lower altitudes, while samples pointing to recharge during both seasons appear to be located at higher altitudes. A number of samples point to altitudes that are far higher than the summit of these islands, with most of these samples displaying temperatures that are also too low to be consistent with the temperature range in place on both islands. Such a trend suggests that the available time for rainwater in these samples to re-equilibrate with the soil air of the islands might be insufficient due to rapid water infiltration where soils are very thin or absent, and fractured bedrock has high permeability.

Warrier, R. B.; Castro, M. C.; Hall, C. M.; D'Ozouville, N.

2010-12-01

160

Composition of solar flare noble gases preserved in meteorite parent body regolith.  

PubMed

The isotopic composition (long-term average) of solar flare (SF) Ne has been determined by three isotope correlation techniques applied to data measured on chemically etched pyroxene separates prepared from the Kapoeta meteorite, which is known to contain implanted solar gases. The SF 20Ne/22Ne ratio obtained is 11.6 +/- 0.2 and confirms previous determinations of this SF ratio in lunar and meteoritic samples. The same SF Ne composition is also obtained by applying an ordinate intercept technique to the same data set. The ordinate intercept technique was also applied to the Ar and He data, on which the three-isotope correlation technique cannot be applied. The isotopic composition of SF Ar and SF He so obtained are SF 36Ar/38Ar = 4.9 +/- 0.1 and SF 4He/3He = 3800 +/- 200, which are significantly different from the solar wind (SW) Ar and SW He values of approximately 5.35 and approximately 2500, respectively. Correlation between 20Ne/22Ne and 36Ar/38Ar for the same data set also gives a similar SF 36Ar/38Ar ratio of 4.8 +/- 0.2. The determined SF He, Ne and Ar isotopic ratios differ from those in SW by 52%, 17% and 9%, respectively, but the elemental compositions of 4He/36Ar and 20Ne/36Ar do not show obvious differences between SF and SW. The concentration of the SF component in Kapoeta pyroxenes is approximately 20% that of the SW component, which is orders of magnitude higher than expected from SW and SF proton flux measurements. Variations in elemental and isotopic composition of He, Ne and Ar in SF relative to SW are found to correlate well with a (Z/A)2 dependence, indicating a rigidity-dependent particle spectrum in solar flares. PMID:11538179

Rao, M N; Garrison, D H; Bogard, D D; Badhwar, G; Murali, A V

1991-11-01

161

Concerning the width of spark channels with different polarities in submicrosecond sliding discharges in noble gases  

SciTech Connect

Previously, the parameters of submicrosecond (with a duration of <200 ns) multichannel high-current discharges sliding along a ceramic surface in Ne, Ar, and Xe were studied only for the negative polarity of the applied voltage. The experimental data indicate that the channels expand in the transverse direction mainly due to electron drift from the channel surface layer under the action of the electric field perpendicular to the channel axis and subsequent gas ionization by these electrons. To investigate mechanisms for the channel development in a sliding discharge-in particular, to determine the contribution of electron drift-it is necessary to carry out experiments similar to those performed earlier for the opposite polarity of the applied voltage. Here, the results of measurements of the widths of the spark channels of negativeand positive-polarity sliding discharges excited in Ne, Ar, and Xe at pressures of 30 and 100 kPa are presented and discussed. It is shown that, depending on the pressure and sort of gas, the averaged optical width of positive-polarity channels is smaller by a factor of 1.27-1.60 than that of negative-polarity channels. The experimental data are analyzed using the theory of propagation of ionization waves with different polarities in gases. Analysis has shown that electron diffusion contributes insignificantly to channel expansion and that, for both polarities, the channel expansion rate exceeds the electron drift velocity in the transverse electric field near the channel. In the framework of the so-called approximation of nonlocalized initial conditions, the measured ratio between of the widths of negativeand positive-polarity channels and their relation to the electron mobility are explained by the channel expansion governed by both electron drift and primary free electrons produced by a short-term source in a narrow region ahead of the front of the expansion wave. Numerical simulations show that the width of this region is comparable with that of the wave front and is more than one order of magnitude smaller than the observed channel radius. Gas photoionization by the channel radiation can serve as a source of primary electrons.

Trusov, K. K. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)

2010-02-15

162

Absolute cross sections for electron loss, electron capture, and multiple ionization in collisions of C{sup 3+} with noble gases  

SciTech Connect

Absolute charge-state-correlated cross sections for projectile electron loss, electron capture, and target multiple ionization in collisions between C{sup 3+} ions and noble gases have been measured for energies between 1.3 and 3.5 MeV. The data have been compared with other similar absolute cross sections existent in the literature for several projectiles. Calculations for the single-loss-multiple-ionization channel have been performed for the screening mode, using both an extended version of the classical-impulse free-collision model and the plane-wave Born approximation (PWBA), and for the antiscreening mode within the PWBA. The energy dependence of the average number of target active electrons which contribute to the antiscreening has been described by means of a simple function, which is ''universal'' for noble gases but, in principle, projectile dependent. A method has been developed to obtain the number of active target electrons for each subshell in the high-velocity regime, which presented physically reasonable results. Analyses of the dependences of the single-capture and transfer-ionization (SC and TI, respectively) processes on the projectile charge states showed that, for He, equally charged bare and dressed projectiles have very similar cross sections; the latter thus acting as structureless point charges. A behavior similar to that in the SC has been observed for the pure single ionization of He by projectiles with different charge states and of the other noble gases by singly charged projectiles. It has been shown that the q{sup 2} dependence of the pure-single and total-ionization cross sections, predicted by first-order models, is only valid for high-collision velocities. For slower collisions, the electron capture process becomes more relevant and competes with the ionization channel, a feature which grows in importance as the projectile charge state increases.

Santos, A. C. F.; Sant'Anna, M. M.; Montenegro, E. C. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21945-970 (Brazil); Sigaud, G. M. [Departamento de Fisica, Pontificia Universidade Catolica do Rio de Janeiro, Caixa Postal 38071, Rio de Janeiro, RJ 22452-970 (Brazil); Melo, W. S. [Departamento de Fisica, Universidade Federal de Juiz de Fora, Juiz de Fora, MG 36036-330 (Brazil)

2010-07-15

163

Noble gases in olivine phenocrysts from drill core samples of the Hawaii Scientific Drilling Project (HSDP) pilot and main holes (Mauna Loa and Mauna Kea, Hawaii)  

NASA Astrophysics Data System (ADS)

We have determined concentrations and isotopic compositions of all noble gases in olivine phenocrysts from the Hawaii Scientific Drilling Project (HSDP) drill core, comprising Mauna Loa lavas in the top 247 m and Mauna Kea lavas down to the preliminary depth of 3109 m. Our aim was to describe the long-term isotopic evolution of noble gases over a significant time fraction of the active life of a major Hawaiian volcano. The He isotopic signature displays a clear temporal trend: 3He/4He ratios increase from MORB-like 9 RA in the youngest lavas to 15 RA in the Mauna Loa section and from ~7 RA to ~12 RA in the subaerial Mauna Kea deposits. They remain close to 12 RA in most of the submarine Mauna Kea samples, except for a few excursions with 3He/4He ratios of up to 21 RA in borehole depths between 2000 and 2600 m. The average 3He/4He ratio of 12 RA is lower than that observed in recent eruptions of Kilauea and Loihi seamount and supports the idea of a concentrically zoned Hawaiian plume [Kurz et al., 1996]. The Ne isotopic signature does not show a temporal evolution. It remains plume-like (plotting close to the Loihi-Kilauea correlation line in a Ne three-isotope diagram) over the whole Mauna Kea section in those samples which are not dominated by air-like Ne. Maximum 20Ne/22Ne and 21Ne/22Ne ratios reach 12.10 +/- 0.36 and 0.0360 +/- 0.0042, respectively. 40Ar/36Ar ratios vary widely between 360 and ~3300 in the >=1000°C release steps due to variable atmospheric contributions. In at least one sample, a 40Ar/36Ar ratio of 14,300 +/- 910 demonstrates the presence of a MORB-like Ar component. Kr and Xe isotopic compositions are atmospheric throughout. We discuss several possibilities on how to explain the isotopic trends of the noble gases and their correlation to other geochemical parameters. Simple admixture of MORB-like noble gases to the plume component cannot account for the observations. We favor a model involving early melt extraction from the outer plume sections, followed by radiogenic ingrowth and, possibly, some interaction with ambient mantle material.

Althaus, Tilmann; Niedermann, Samuel; Erzinger, Jörg

2003-01-01

164

Noble gases in olivine phenocrysts from drill core samples of the Hawaii Scientific Drilling Project (HSDP) pilot and main holes (Mauna Loa and Mauna Kea, Hawaii)  

NASA Astrophysics Data System (ADS)

We have determined concentrations and isotopic compositions of all noble gases in olivine phenocrysts from the Hawaii Scientific Drilling Project (HSDP) drill core, comprising Mauna Loa lavas in the top 247 m and Mauna Kea lavas down to the preliminary depth of 3109 m. Our aim was to describe the long-term isotopic evolution of noble gases over a significant time fraction of the active life of a major Hawaiian volcano. The He isotopic signature displays a clear temporal trend: 3He/4He ratios increase from MORB-like 9 RA in the youngest lavas to 15 RA in the Mauna Loa section and from ˜7 RA to ˜12 RA in the subaerial Mauna Kea deposits. They remain close to 12 RA in most of the submarine Mauna Kea samples, except for a few excursions with 3He/4He ratios of up to 21 RA in borehole depths between 2000 and 2600 m. The average 3He/4He ratio of 12 RA is lower than that observed in recent eruptions of Kilauea and Loihi seamount and supports the idea of a concentrically zoned Hawaiian plume [, 1996]. The Ne isotopic signature does not show a temporal evolution. It remains plume-like (plotting close to the Loihi-Kilauea correlation line in a Ne three-isotope diagram) over the whole Mauna Kea section in those samples which are not dominated by air-like Ne. Maximum 20Ne/22Ne and 21Ne/22Ne ratios reach 12.10 ± 0.36 and 0.0360 ± 0.0042, respectively. 40Ar/36Ar ratios vary widely between 360 and ˜3300 in the ?1000°C release steps due to variable atmospheric contributions. In at least one sample, a 40Ar/36Ar ratio of 14,300 ± 910 demonstrates the presence of a MORB-like Ar component. Kr and Xe isotopic compositions are atmospheric throughout. We discuss several possibilities on how to explain the isotopic trends of the noble gases and their correlation to other geochemical parameters. Simple admixture of MORB-like noble gases to the plume component cannot account for the observations. We favor a model involving early melt extraction from the outer plume sections, followed by radiogenic ingrowth and, possibly, some interaction with ambient mantle material.

Althaus, Tilmann; Niedermann, Samuel; Erzinger, JöRg

2003-01-01

165

Subduction of solar-type noble gases from extraterrestrial dust: constraints from high-pressure low-temperature metamorphic deep-sea sediments  

NASA Astrophysics Data System (ADS)

Solar-type helium (He) and neon (Ne) in the Earth’s mantle were suggested to be the result of solar-wind loaded extraterrestrial dust that accumulated in deep-sea sediments and was subducted into the Earth’s mantle. To obtain additional constraints on this hypothesis, we analysed He, Ne and argon (Ar) in high pressure low temperature metamorphic rocks representing equivalents of former pelagic clays and cherts from Andros (Cyclades, Greece) and Laytonville (California, USA). While the metasediments contain significant amounts of 4He, 21Ne and 40Ar due to U, Th and K decay, no solar-type primordial noble gases were observed. Most of these were obviously lost during metamorphism preceding 30 km subduction depth. We also analysed magnetic fines from two Pacific ODP drillcore samples, which contain solar-type He and Ne dominated by solar energetic particles (SEP). The existing noble gas isotope data of deep-sea floor magnetic fines and interplanetary dust particles demonstrate that a considerable fraction of the extraterrestrial dust reaching the Earth has lost solar wind (SW) ions implanted at low energies, leading to a preferential occurrence of deeply implanted SEP He and Ne, fractionated He/Ne ratios and measurable traces of spallogenic isotopes. This effect is most probably caused by larger particles, as these suffer more severe atmospheric entry heating and surface ablation. Only sufficiently fine-grained dust may retain the original unfractionated solar composition that is characteristic for the Earth’s mantle He and Ne. Hence, in addition to the problem of metamorphic loss of solar noble gases during subduction, the isotopic and elemental fractionation during atmospheric entry heating is a further restriction for possible subduction hypotheses.

Schwarz, W. H.; Trieloff, M.; Altherr, R.

2005-08-01

166

Fluorescence from Mixtures of Noble Gases and Various Substrates, Induced by Ns Pulses of 600 KeV Electrons.  

National Technical Information Service (NTIS)

We measured relative energy transfer probabilities from excited noble gas species, produced at high pressure (5-20b) by short (2 ns) pulses of 600 keV electrons, to a variety of substrates. Fluorescence spectra were recorded in two modes, (a) wavelength d...

S. H. Bauer J. Krasinski

1980-01-01

167

Noble gases in lunar anorthositic rocks 60018 and 65315 - Acquisition of terrestrial krypton and xenon indicating an irreversible adsorption process  

Microsoft Academic Search

Results are presented from noble gas analyses of the 60018 and 65315 lunar anorthositic breccias and from experiments designed to determine whether the atmospheric contamination is the only source of the terrestriallike Xe in lunar samples (and, if so, what is the nature of the contaminating process). Results clearly show that the anorthositic material was contaminated both by Kr and

S. Niedermann; O. Eugster

1992-01-01

168

Trapping of noble gases (He–Kr) by the aromatic H3+ and Li3+ species: a conceptual DFT approach  

Microsoft Academic Search

Stability, reactivity and aromaticity of clusters of various noble gas atoms\\u000atrapped in aromatic H3+ and Li3+ rings are studied at the B3LYP\\/6-311+G(d) and\\u000aMP2\\/6-311+G(d) levels of theory. Electrophilicity, gain in energy and nucleus\\u000aindependent chemical shift values lend additional insights into the overall\\u000abehavior of these clusters.

Arindam Chakraborty; Santanab Giri; Pratim Kumar Chattaraj

2010-01-01

169

Trapping of Noble Gases (He-Kr) by the Aromatic H3+ and Li3+ Species: A Conceptual DFT Approach  

Microsoft Academic Search

Stability, reactivity and aromaticity of clusters of various noble gas atoms trapped in aromatic H3+ and Li3+ rings are studied at the B3LYP\\/6-311+G(d) and MP2\\/6-311+G(d) levels of theory. Electrophilicity, gain in energy and nucleus independent chemical shift values lend additional insights into the overall behavior of these clusters.

Arindam Chakraborty; Santanab Giri; Pratim Kumar Chattaraj

2009-01-01

170

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

171

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

172

Combined action of the bound-electron nonlinearity and the tunnel-ionization current in low-order harmonic generation in noble gases.  

PubMed

We study numerically low-order harmonic generation in noble gases pumped by intense femtosecond laser pulses in the tunneling ionization regime. We analyze the influence of the phase-mismatching on this process, caused by the generated plasma, and study in dependence on the pump intensity the origin of harmonic generation arising either from the bound-electron nonlinearity or the tunnel-ionization current. It is shown that in argon the optimum pump intensity of about 100 TW/cm2 leads to the maximum efficiency, where the main contribution to low-order harmonics originates from the bound-electron third and fifth order susceptibilities, while for intensities higher than 300 TW/cm2 the tunnel-ionization current plays the dominant role. Besides, we predict that VUV pulses at 133 nm can be generated with relatively high efficiency of about 1.5 × 10-3 by 400 nm pump pulses. PMID:24150398

Sapaev, Usman; Husakou, Anton; Herrmann, Joachim

2013-10-21

173

Pump-probe studies of autoionizing states of noble gases combining laser and synchrotron radiation—The nf? Rydberg states of neon  

NASA Astrophysics Data System (ADS)

A mode-locked tunable Ti:Sapphire oscillator has been synchronized with the time structure of a storage ring and used to study the photoionization of noble gases. In multi-bunch operation of the ring the setup permits the observation of the dynamics from a few nanoseconds down to the tens of picoseconds range. The characteristics of the setup are demonstrated by following the two-color ionization of helium (via the 1s3p 1Po state) and argon (via the 3p5 (2P3/2) 3d state). In the CW mode we have also examined the two-color ionization of neon via the 2p5 (2P1/2) 3d? state. In neon the nf? Rydberg series was followed up to n˜50, and the quantum defect was determined.

Moise, Angelica; Alagia, Michele; Banchi, Luca; Ferianis, Mario; Prince, Kevin C.; Richter, Robert

2008-04-01

174

The heavy noble gas composition of the depleted MORB mantle (DMM) and its implications for the preservation of heterogeneities in the mantle  

NASA Astrophysics Data System (ADS)

To characterize the heavy noble gas composition of MORBs we present new He, Ne, Ar, and Xe abundances and isotopic compositions from the equatorial Mid-Atlantic Ridge. Both depleted MORBs nominally devoid of plume influence and more enriched MORBs thought to represent the influence of a HIMU mantle plume are present in close geographical proximity in this region. Ne-Ar-Xe isotopic compositions in individual step-crushes are correlated, which, along with significant radiogenic excesses, allows correction for shallow-level air contamination. Based on the relationship between the noble gases and the lithophile isotopes (Sr, Nd and Pb), the depleted MORB mantle has a 21Ne/22Ne between 0.0617 and 0.0646, 40Ar/36Ar ratio of 41,500±9000 and 129Xe/130Xe ratio of 7.77±0.06. On the other hand, the HIMU-type MORBs are characterized by far less radiogenic Ne, Ar and Xe isotopic compositions with mantle source 21Ne/22Ne between 0.0544 and 0.0610, and 40Ar/36Ar and 129Xe/130Xe ratios of 18,100±600 and 7.21±0.06, respectively. The observation of less nucleogenic 21Ne/22Ne in HIMU-type MORBs is similar to observations from HIMU ocean islands and requires the HIMU plume to be comprised of both recycled and primitive material. Within the depleted MORBs we observe He and Ne to be negatively correlated. The observation suggests that along the equatorial Atlantic the most depleted MORBs are related to normal MORBs through the addition of a small proportion of a HIMU plume component.Our new Xe isotopic measurements demonstrate distinct 129Xe/136Xe ratios in the mantle sources of depleted MORBs, HIMU-type MORBs and the Iceland plume. While substantial injection of atmospheric Xe into these mantle sources is implied, the differences in Xe isotopic composition cannot result solely from recycling of air. Rather, they require that mantle plumes sample a reservoir less degassed than the depleted MORB mantle. This conclusion is consistent with a higher proportion of Pu- to U-derived fission Xe in Iceland and HIMU-type MORBs compared to the depleted MORBs. Overall, the Xe isotopic compositions imply that mantle plumes tap a reservoir that separated from the MORB source within the first 100 million years of Earth's history and that the two reservoirs have had limited direct mixing since then.

Tucker, Jonathan M.; Mukhopadhyay, Sujoy; Schilling, Jean-Guy

2012-11-01

175

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

176

MEASUREMENT AND CORRELATION OF GAS-LIQUID EQUILIBRIA IN MIXTURES OF LIGHT GASES AND HEAVY HYDROCARBONS  

Microsoft Academic Search

Because of increased interest in coal conversion processes there is a growing need for basic information on the vapor-liquid equilibria of mixtures containing light non-condensable gases and heavy aromatic hydrocarbons found in coal derived liquids. These phase equilibrium data are required at the elevated temperatures and pressures at which most coal conversion processes will be run.^ In this work we

HERBERT M SEBASTIAN

1980-01-01

177

Strong configuration interaction in the double ionization spectra of noble gases studied by the relativistic propagator method  

NASA Astrophysics Data System (ADS)

In this work, the four-component two-particle propagator technique is employed for the calculation of double ionization spectra of the noble gas atoms Ne through Rn. For a correct assignment of the individual final states, inclusion of spin-orbit coupling and electron correlation is mandatory and is accounted for in the framework of the relativistic propagator. It was observed that the ns2np4(3P2,1,0, 1D2, 1S0) manifolds of all investigated noble gas dications exhibit a clear main-state character with only small admixture from other configurations. This also refers to the 2s12p5(3P2,1,0o, 1P1o) states of Ne2+. In the argon, krypton, and xenon dications, the ns1np5(3P2,1,0o) states, and especially the ns1np5(1P1o) ones, lose intensity due to pronounced configuration interaction. These states experience strong mixings with ground-state shake-up satellites, which occupy the same energy region. The composition of the 5s15p5(1P1o) singlet state of Xe2+ is studied in detail by analyzing the corresponding eigenvector. As long as a LS coupling picture can be approximately maintained, the amount of singlet-triplet splitting decreases in the sequence from neon to xenon. In the 6s16p5 manifold of Rn2+, a complete disappearance of well-defined main states takes place leading to a dense and complicated spectrum governed by very strong multiconfiguration effects. Relativistic corrections to the Coulomb interaction are accounted for by inclusion of the Gaunt (magnetic) term.

Pernpointner, Markus; Zobel, J. Patrick; Kryzhevoi, Nikolai V.

2012-01-01

178

Recycling of oceanic crust and sediments: the noble gas subduction barrier  

Microsoft Academic Search

We have determined the concentrations and isotopic composition of noble gases in old oceanic crust and oceanic sediments and the isotopic composition of noble gases in emanations from subduction volcanoes. Comparison with the noble gas signature of the upper mantle and a simple model allow us to conclude that at least 98% of the noble gases and water in the

Thomas Staudacher; Claude J. Allègre

1988-01-01

179

A two-component mantle extending from Hyblean Plateau to Mt Etna (Eastern Sicily) as inferred by an integrated approach with noble gases, trace elements and isotope geochemistry.  

NASA Astrophysics Data System (ADS)

We carried out a geochemical investigation of the mantle beneath Hyblean and Etnean area through ultramafic xenoliths (peridotites and pyroxenites) retained in Miocenic age Hyblean volcanics and primitive Etnean lavas and tephra, respectively. Major and trace elements and Sr-Nd isotopes (whole rock and /or minerals) were analysed together with noble gases entrapped in fluid inclusions hosted in olivines and pyroxenes phenocrysts. The geochemical results from Hyblean xenoliths study highlighted the presence of two distinct compositional groups: the peridotites, featured by a more enriched geochemical fingerprint (3He/4He ~7 Ra, 143Nd/144Nd ~0.5129 and Zr/Nb ~ 4) and the pyroxenites, characterized by a more primitive character (3He/4He up to 7.6 Ra, 143Nd/144Nd ~0.5130 and Zr/Nb ~30). Our interpretation is that metasomatic processes interested the Hyblean lithosphere and the pyroxenites (former primitive mantle melts) represent the metasomatizing agent. During their ascent these primitive melts permeated the peridotitic mantle at different levels, producing a variable degree of refertilization. The metasomatic processes affected distributions of both trace elements and noble gases, even though these geochemical tracers displayed very different sensitivity to the effects of metasomatic mixing between two end-members. The investigated primitive Etnean magmas showed a variable REE enrichment respect to MORB (Lan/Ybn =11-26) and isotopic values of Sr, Nd and He in the following ranges: 143Nd/144Nd = 0.512869-0.512896; 86Sr/87Sr = 0.70330-0.70370; 3He/4He = 7-7.6 Ra. A variable melting degree of a common mantle source together with a variable level of crystallization and crustal contamination is hypothesised to explain the variations exhibited by the above Etnean dataset. Numerical simulation performed on MELT code allowed to estimate the trace elements content of the Etnean mantle source. These results, joined to the most primitive isotopic values of He- Sr- Nd among the investigated products helped to geochemically characterize the mantle beneath the Etnean area, suggesting a strict relation with that Hyblean. Indeed, the modeled Etnean source locates on the mixing zone between the Hyblean peridotite and pyroxenite, so testifying a simultaneous contribution of two components in the genesis of the investigated lavas and supporting the hypothesis of an heterogeneous and metasomatized lithosphere common to both areas.

Correale, A.; Martelli, M.; Paonita, A.; Rizzo, A.; Rotolo, S.

2012-04-01

180

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 0.01–0.06 Ra (Ra is the atmospheric value of 1.38×10?6) indicating the absence of mantle-derived

Anne Battani; Philippe Sarda; Alain Prinzhofer

2000-01-01

181

Ultrahigh sensitivity heavy noble gas detectors for long-term monitoring and monitoring air. 1998 annual progress report  

SciTech Connect

'The primary objective of this research project is to develop heavy noble gas (krypton, xenon, and radon) detectors for: (1) long-term monitoring of transuranic waste, spent fuel, and other uranium and thorium bearing wastes, and (2) alpha particle air monitors that discriminate between radon emissions and other alpha emitters. A University of Cincinnati/Argonne National Laboratory (UC/ANL) Team has been assembled to complete this detector development project. DOE needs that are addressed by this project include improved long-term monitoring capability and improved air monitoring capability during remedial activities. Successful development and implementation of the proposed detection systems could significantly improve current capabilities with relatively simple and inexpensive equipment. As of June 1, 1998, the UC/ANL Team has: (1) made significant progress toward characterizing the fluid transfer process which is the basis for this detector development project and (2) evaluated several radiation detectors and several potential pulse processing schemes. The following discussion describes the progress made during the first year of this project and the implications of this progress.'

Valentine, J.D. [Univ. of Cincinnati, OH (US); Gross, K. [Argonne National Lab., IL (US)

1998-06-01

182

Noble gas isotopes and the chemical composition of geothermal gases from the eastern part of the Büyük Menderes Graben (Turkey)  

NASA Astrophysics Data System (ADS)

We present noble gas isotope and gas composition data from eight production wells of the Kizildere geothermal field and from six gas discharging pools from the adjacent Tekke Hamam geothermal field, situated in the eastern segment of the Büyük Menderes Graben system in western Anatolia (Turkey). Gas from both locations is composed mainly of CO2 with minor contributions of N2, H2S, CH4, O2, Ar, H2, C2+ and He, with higher contents of H2S, He and C2+ in Tekke Hamam samples.Air corrected helium isotope ratios reveal a mantle origin for samples from both locations, but 3He/4He ratios are lower and more variable at Kizildere (0.96-2.06 Ra) than at Tekke Hamam (2.36-2.91 Ra, Ra is the atmospheric 3He/4He ratio of 1.39 × 10- 6). Kizildere gas contains less 4He (0.7-2.2 ppmv) and 3He (~ 2-5 × 10- 6 ppmv) than gas from Tekke Hamam (2.5-3.5 ppmv and ~ 1 × 10- 5 ppmv, respectively). CO2/3He ratios of 2-8 × 1011 at Kizildere and 0.7-1 × 1011 at Tekke Hamam are higher than average mantle values (~ 2 × 109). Within the Kizildere geothermal field, reservoir temperatures and CO2/3He and CH4/C2H6 ratios increase and 3He/4He ratios decrease from southwest to northeast. Interpolation of a linear trajectory between 3He/4He and temperature from Kizildere delivers temperature of 173 °C-184 °C for the source reservoir of Tekke Hamam, in good agreement with measured reservoir temperatures from well TH-2 at Tekke Hamam (171 °C).The low helium content, the variable helium isotope composition and the higher CO2/3He ratios at Kizildere can be explained by temperature-dependent partial removal of mantle-derived helium, e.g. through vapor separation, followed by addition of radiogenic helium. Kizildere samples derive from the remaining water phase after gas separation, while Tekke Hamam samples may represent the gas phase liberated by the former process. The pristine 3He/4He ratio of helium at Kizildere can be calculated as 2.2 Ra, close to helium isotope ratios observed at Tekke Hamam. Partial removal of helium may also account for the higher and T-dependent CO2/3He ratios at Kizildere, compared to Tekke Hamam, but such process alone cannot explain the overall high CO2/3He ratios (> 7 × 1010) and calls for contribution of CO2 from interaction between geothermal fluids and carbonate reservoir rock. Noble gas abundances indicate mixing with cold meteoric water in the reservoir.

Wiersberg, T.; Süer, S.; Güleç, N.; Erzinger, J.; Parlaktuna, M.

2011-12-01

183

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

PubMed

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 7p(3/2) orbital. Van der Waals coefficients C(3) and adsorption enthalpies DeltaH(ads) 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 C(3) coefficients were shown to steadily increase in group 18, while the increase in DeltaH(ads) 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. PMID:19045133

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

2008-10-14

184

Noble Gases in Alpine Gold: U\\/Th-He Dating and Excesses of Radiogenic He and AR  

Microsoft Academic Search

Gold precipitates in hydrothermal fluids along with other heavy elements, such as Ag and Pt. In order to explore the possibility of dating the formation of gold we determined the concentrations of U, Th, and their decay product ^4He, as well as the K and ^40Ar concentrations in vein-type gold and in placer gold samples. The gold-quartz veins at Brusson

O. Eugster; B. Hofmann; U. Krahenbuhl; J. Neuenschwander

1992-01-01

185

Light noble gases and cosmogenic radionuclides in Estherville, Budulan and other mesosiderites: Implications for exposure histories and production rates  

NASA Astrophysics Data System (ADS)

We report measurements of 26Al, 10Be, 41Ca, and 36Cl in the silicate and metal phases of 11 mesosiderites, including several specimens each of Budulan and Estherville, of the brecciated meteorite Bencubbin, and of the iron meteorite Udei Station. Average production rate ratios (atom/atom) for metal phase samples from Estherville and Budulan are 26Al/10Be = 0.79 ( 0.03; 36Cl/10Be = 5.3 ( 0.2. For a larger set of meteorites that includes iron meteorites and other mesosiderites, we find 26Al/10Be = 0.72 ( 0.01 and 36Cl/10Be = 4.5 ( 0.2. The average 41Ca/36Cl production rate ratio is 1.10 ( 0.04 for metal separates from Estherville and four small iron falls. The 41Ca activities in dpm/(kg Ca) of various silicate separates from Budulan and Estherville span nearly a factor of 4, from <400 to >1600, indicating preatmospheric radii of >30 cm. After allowance for composition, the activities of 26Al and 10Be (dpm/kg silicate) are similar to values measured in most ordinary chondrites and appear to depend only weakly on bulk Fe content. Unless shielding effects are larger than suggested by the 36Cl and 41Ca activities of the metal phases, matrix effects are unimportant for 10Be and minor for 26Al. Noble gas concentrations and isotopic abundances are reported for samples of Barea, Emery, Mincy, Morristown, and Marjalahti. New estimates of 36Cl/36Ar exposure ages for the metal phases agree well with published values. Neon-21 production rates for mesosiderite silicates calculated from these ages and from measured 21Ne contents are consistently higher than predicted for L chondrites despite the fact that the mesosiderite silicates have lower Mg contents than L chondrites. We suggest that the elevation of the 21Ne production rate in mesosiderite silicates reflects a "matrix effect," that is, the influence of the higher Fe content of mesosiderites, which acts to enhance the flux of low-energy secondary particles and hence the 21Ne production from Mg. As 10Be production is relatively insensitive to this matrix effect, 10Be/21Ne ages give erroneously low production rates and high exposure ages. By coincidence, standard 22Ne/21Ne based "shielding" corrections give fairly reliable 21Ne production rates in the mesosiderite silicates.

Albrecht, A.; Schnabel, C.; Vogt, S.; Xue, S.; Herzog, G. F.; Begemann, F.; Weber, H. W.; Middleton, R.; Fink, D.; Klein, J.

2000-09-01

186

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 CO2-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., Al2O3 = 0.8-1.5 wt.%, TiO2 = 0.03-0.08 wt.%) suggest a residual character of the mantle, a moderate enrichment in some incompatible elements (e.g., LaN/YbN = 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

187

Metamorphic fluid origins in the Osborne Fe oxide-Cu-Au deposit, Australia: evidence from noble gases and halogens  

NASA Astrophysics Data System (ADS)

The Osborne iron oxide-copper-gold (IOCG) deposit is hosted by amphibolite facies metasedimentary rocks and associated with pegmatite sheets formed by anatexis during peak metamorphism. Eleven samples of ore-related hydrothermal quartz and two pegmatitic quartz-feldspar samples contain similarly complex fluid inclusion assemblages that include variably saline (<12-65 wt% salts) aqueous and liquid carbon dioxide varieties that are typical of IOCG mineralisation. The diverse fluid inclusion types present in each of these different samples have been investigated by neutron-activated noble gas analysis using a combination of semi-selective thermal and mechanical decrepitation techniques. Ore-related quartz contains aqueous and carbonic fluid inclusions that have similar 40Ar/36Ar values of between 300 and 2,200. The highest-salinity fluid inclusions (47-65 wt% salts) have calculated 36Ar concentrations of approximately 1-5 ppb, which are more variable than air-saturated water (ASW = 1.3-2.7 ppb). These fluid inclusions have extremely variable Br/Cl values of between 3.8 × 10-3 and 0.3 × 10-3, and I/Cl values of between 27 × 10-6 and 2.4 × 10-6 (all ratios are molar). Fluid inclusions in the two pegmatite samples have similar 40Ar/36Ar values of ?1,700 and an overlapping range of Br/Cl and I/Cl values. High-salinity fluid inclusions in the pegmatite samples have 2.5-21 ppb 36Ar, that overlap the range determined for ore-related samples in only one case. The fluid inclusions in both sample groups have 84Kr/36Ar and 129Xe/36Ar ratios that are mainly in the range of air and air-saturated water and are similar to mid-crustal rocks and fluids from other settings. The uniformly low 40Ar/36Ar values (<2,200) and extremely variable Br/Cl and I/Cl values do not favour a singular or dominant fluid origin from basement- or mantle-derived magmatic fluids related to A-type magmatism. Instead, the data are compatible with the involvement of metamorphic fluids that have interacted with anatectic melts to variable extents. The ‘metamorphic’ fluids probably represent a mixture of (1) inherited sedimentary pore fluids and (2) locally derived metamorphic volatilisation products. The lowest Br/Cl and I/Cl values and the ultra-high salinities are most easily explained by the dissolution of evaporites. The data demonstrate that externally derived magmatic fluids are not a ubiquitous component of IOCG ore-forming systems, but are compatible with models in which IOCG mineralisation is localised at sites of mixing between fluids of different origin.

Fisher, L. A.; Kendrick, M. A.

2008-07-01

188

Noble gas concentrations in stalagmite fluid inclusions as a potential proxy for past cave temperatures  

NASA Astrophysics Data System (ADS)

Dissolved atmospheric noble gas concentrations in water can be used to determine the environmental conditions that prevailed at the time of the last gas exchange with the atmosphere, because the solubilites of noble gases are a well-defined function of the temperature and the salinity of the water. Accordingly, noble gas concentrations in fluid inclusions in stalagmites are a potential proxy for the cave temperature. In stalagmite research, independent and direct cave temperature proxies are still rare, but very important for the interpretation of the stable isotopic composition of the calcite. As the cave temperature is a good measure of the annual mean temperature outside the cave, noble gas concentrations in stalagmite fluid inclusions may also allow to directly reconstruct paleotemperatures. We developed a method to precisely determine noble gas concentrations (analytical error of 2-4%) in small amounts of water (1mg) extracted from stalagmite samples. It includes an extraction technique to separate water inclusions from air inclusions, which are also abundant in stalagmites and mask the temperature dependent noble gas signature of the water inclusions. To achieve such a separation, the samples are pre-crushed to a defined grain size to remove inter-crystalline air inclusions, before water and noble gases are extracted by heating. The pre-crushing occurs in a glove box filled with pure He to avoid any contamination by adsorption of atmospheric gases on the freshly produced surfaces of the calcite. The liberated water mass is determined by measuring its pressure in a known volume kept at a constant temperature of 40°C to prevent water condensation. The determined noble gas concentrations in modern stalagmite samples show that air and water inclusions are sufficiently separated with our extraction technique, resulting in low "excess air" amounts. The measured Kr and Xe concentrations are clearly different in samples from stalagmites that were deposited at a cave temperature of 27°C and of 13°C respectively. Both results are important steps towards the determination of noble gas temperatures (NGTs) in fluid inclusions in stalagmites. However, we also found an excess in Ar, which most likely adsorbed on the samples during pre-crushing in the glove box. Therefore, we plan to further purify the air in the glove box by connecting a liquid N2 cold trap to the glove box. The noble gas concentrations of all heavy noble gases are then expected to be composed air and air saturated water only, allowing to determine NGTs using standard least squares fitting methods.

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

2010-05-01

189

Common asteroid break-up events of eucrites, diogenites, and howardites and cosmic-ray production rates for noble gases in achondrites  

Microsoft Academic Search

We determined the cosmic-ray produced noble gas abundances in eight diogenites, four eucrites, and four howardites. Using these and additional noble gas and chemical data from the literature, composition and shielding dependent production rates of achondrites for 3He, 21Ne, 38Ar, 78Kr, 83Kr, and 126Xe were derived based on 81Kr?Kr exposure ages. The cosmogenic ratio 22Ne\\/21Ne is found to be a

O. Eugster; Th. Michel

1995-01-01

190

Noble gases in the sediment pore water as proxies for physical transport processes and past environmental conditions in Lake Van (Turkey)  

NASA Astrophysics Data System (ADS)

Since many decades unconsolidated sediments have been proposed as a potential archive for noble-gas records to reconstruct past environmental conditions in lakes and oceans. In addition, the accumulation of non-atmospheric noble-gas isotopes allows tracing the geochemical origin and transport processes of the pore fluids [7]. For instance, the abundance of terrigenic He isotopes reflects the residence time and transport dynamics of the dissolved species in the pore space. The 3He/4He ratio of terrigenic He can be used to constrain the geochemical origin of the pore fluids [3, 7]. However, methods for reliable and robust noble-gas analysis in pore water of unconsolidated sediments have been developed only recently [1, 6]. Lake Van (Turkey) is one of the largest terminal lakes and the largest soda lake on Earth. The physical conditions of the lake are known to react sensitively to changes in the hydrological cycle and to the environment of the lake catchment [2]. Therefore, the noble-gas record in the sediments of Lake Van have a great potential as an archive to reconstruct past climate evolution in eastern Anatolia where the atmospheric south-western jet stream intersects the northern branch of the subtropical high pressure belt [4]. Also, the basin of Lake Van is situated in a tectonically active region characterized by the presence of major faults and volcanos and is known to accumulate mantle fluids [3, 7]. Noble-gas isotopes are therefore expected to yield insights into the origin and transport processes of terrigenic fluids in the sediment pore space and their release into the water body [7]. In this study we present noble-gas and salinity data measured in the pore water of sediment samples collected in Lake Van. Noble-gas data from short cores (~ 2 m) taken at different sites throughout the lake basin are discussed from the point of view of the fluid transport in the pore space. In this context, we interpret the latest results from the noble-gas samples acquired in 2010 during the ICDP PaleoVan drilling operations from 220 m long cores [4, 5]. Noble-gas measurements are further linked to salinity measurements in terms of past lake level fluctuations and physical conditions of the water body of Lake Van.

Tomonaga, Y.; Brennwald, M. S.; Kipfer, R.

2012-04-01

191

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...

192

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

193

Spin-exchange optical pumping of noble-gas nuclei  

Microsoft Academic Search

Spin-exchange optical pumping of mixtures of alkali-metal vapors and noble gases can be used to efficiently polarize the nuclei of the noble-gas atoms. Liters of noble gases at standard temperature and pressure and with nuclear spin polarizations of several tens of percent are now used in many applications. The authors describe the basic phenomena that govern the spin-exchange process and

Thad G. Walker; William Happer

1997-01-01

194

Polarized noble gas MRI  

SciTech Connect

The development of convenient methods to polarize liter quantities of the noble gases helium-3 and xenon-129 has provided the opportunity for a new MRI method to visualize the internal air spaces of the human lung. These spaces are usually poorly seen with hydrogen-based MRI, because of the limited water content of the lung and the low thermal polarization of the water protons achieved in conventional magnets. In addition, xenon, which has a relatively high solubility and a sufficiently persistent polarization level in blood and biological tissue, offers the prospect of providing perfusion images of the lung, brain and other organs.

Brookeman, James R.; Mugler, John P. III; Lange, Eduard E. de; Knight-Scott, Jack; Maier, Therese [Department of Radiology, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908 (United States); Bogorad, Paul; Driehuys, Bastiaan; Cates, Gordon; Happer, William [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Daniel, Thomas M. [Department of Surgery, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908 (United States); Truwit, Jonathon D. [Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908 (United States)

1998-01-20

195

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 8±1 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

196

Single grain noble gas analysis of Antarctic micrometeorites by stepwise heating method with a newly constructed miniature furnace  

NASA Astrophysics Data System (ADS)

Ten micrometeorites weighing 0.14-18.5 ?g, each retrieved from surface snow near the Dome Fuji Station, Antarctica (snow-AMMs), were studied to elucidate their noble gases, mineralogy, morphology, and chemical compositions. Low densities in the range of 0.2-1.4 g/cm3 estimated for seven samples suggested a porous inner structure. Noble gases were extracted from each particle using stepwise heating with a laboratory manufactured miniature furnace. Isotopic ratios of He and Ne indicate that the light noble gases with high 4He concentrations ranging from 10-2 to 10-4 cm3 STP/g are mostly of solar origin. The higher concentrations of 4He observed for several samples are comparable with those of IDPs enriched in solar He, but exceed those reported for ice-AMMs. In contrast to He and Ne, heavy noble gases Ar, Kr, and Xe are primordial ones resembling Q-gas trapped in chondrites, although a small contribution of solar Ar is indicated for some samples with higher 36Ar/132Xe ratios than that for the Q-gas. Three particles released appreciable amounts of He at temperatures lower than 800°C, suggesting heating temperatures lower than 700°C at the time of atmospheric entry. Other particles released at most 10% of total He at the temperatures up to 800°C. Based on their sizes, weights, and release profiles of 4He, initial speeds of less than 14 km/s at atmospheric entry were indicated for the particles. The slow entry speeds imply that all the snow-AMMs studied in this work were likely derived from asteroids. The present work demonstrates that the miniature furnace can be applicable to noble gas analysis of tiny grains from the Itokawa asteroidal regolith materials returned by the Hayabusa mission.

Bajo, K.-i.; Akaida, T.; Ohashi, N.; Noguchi, T.; Nakamura, T.; Nakamura, Y.; Sumino, H.; Nagao, K.

2011-10-01

197

Modeling the atmospheric dispersion of accidentally released heavy gases from photovoltaic cell manufacturing facilities.  

National Technical Information Service (NTIS)

Many hazardous gases used in the photovoltaic cell industry are heavier than air. Following an accidental release, their dispersion in air, differs from the dispersion of a neutrally buoyant gas and, as such, it requires special consideration. This report...

V. M. Fthenakis

1986-01-01

198

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

NASA Astrophysics Data System (ADS)

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 portion of the Fayetteville (H4-6) chondrite that contained visible amounts (~25 vol%) of attached silicates was oxidized with CuCl(sub)2xnH2O-solutions (first proposed by Vilcsek and Wanke, 1965) in a pyrex-glass extraction line. Average procedural and reagent blank values for a typical step duration of one hour are [in 10^-10 cm^3 STP]: ^4He = 500; ^20Ne = 0.7; ^40Ar = 95. Here we report data of a preliminary experiment obtained on a small 9.2 mg sample, subjected to increasingly aggressive solutions. Blank corrections are substantial and only 5 steps yielded meaningful data. At the conference, we will present results of a considerably larger Fayetteville metal sample. The Ne isotopic data are rather similar to CSSE data of ilmenite, pyroxene, and plagioclase separates from lunar soils (Wieler et al., 1986; Wieler et al., 1987; Benkert et al., 1988). (^20Ne/^22Ne)(sub)tr starts at 13.1 and decreases to 11.6. The latter value is close to the SEP-Ne point (^20Ne/^22Ne ~ 11.3 +- 0.3) indicating that we succeeded to isolate SEP-Ne in rather pure form from Fayetteville metal. The first CSSE steps release isotopically slightly heavier Ne than the first combustion steps of a Weston metal separate analyzed by Becker and Pepin (1991), whereas in the last CSSE steps Ne is consideribly closer to the SEP composition than in the last combustion/pyrolysis steps. The air corrected ^36Ar/^38Ar ratios range between 4.0 to 2.6 (assuming all ^40Ar to be atmospheric). These values are clearly lower than the ratio of SW-Ar and SEP-Ar of ~5.5 and ~4.9, respectively, and show that cosmogenic Ar interfered severely. Only a more gentle etching at the start of the run could possibly reveal the undisturbed SW-Ar signature. Due to cosmogenic ^3He we can also not derive a (^3He/^4He)(sub)tr value from our first data set. The ^20Ne/^36Ar ratio corrected for air Ar and to first order also for cosmogenic Ar is between 40 and 50 in all steps with uncertainties of 5 to 10%. This is within error identical to the solar wind value of 45 +- 10 and indicates that Fayetteville metal indeed retains rather unfractionated solar Ne and Ar. Similar ^20Ne/^36Ar values were also observed in Weston metal (Becker and Pepin, 1991). In the first two steps corrected ^4He/^36Ar ratios are 15000 and 21000, respectively, close to the solar wind value of 25000, but later this ratio decreases to 8000, which is not yet well understood. We see no evidence for (^4He/^36Ar)(sub)sw = 36000 as claimed for Weston metal (Becker and Pepin, 1991). This pilot experiment indicates that solar wind gases in metal indeed are even less disturbed by diffusion than in ilmenites and further underscores the existence of SEP noble gases as an independent component in the solar corpuscular radiation. Work supported by the Swiss National Science Foundation. References: Becker R.H. and Pepin R.O. (1991) Earth Planet. Sci. Lett. 103, 55-68. Benkert J.P. et al. (1988) Lunar Planet. Sci. (abstract) 19, 59. Geiss J. et al. (1972) NASA SP-315, 14.1- 14.10. Wieler R. et al. (1986) Geochim. Cosmochim. Acta 50, 1997- 2017. Wieler R. et al. (1987) Lunar Planet. Sci. (abstract) 18, 1080. Vilcsek E. and Wanke H. (1965) Z. Naturforsch. 20a, 1282.

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

1992-07-01

199

Comparison of cosmic-ray exposure ages and trapped noble gases in chondrule and matrix samples of ordinary, enstatite, and carbonaceous chondrites  

NASA Astrophysics Data System (ADS)

We performed a comprehensive study of the He, Ne, and Ar isotopic abundances and of the chemical composition of bulk material and components of the H chondrites Dhajala, Bath, Cullison, Grove Mountains 98004, Nadiabondi, Ogi, and Zag, of the L chondrites Grassland, Northwest Africa 055, Pavlograd, and Ladder Creek, of the E chondrite Indarch, and of the C chondrites Hammadah al Hamra 288, Acfer 059, and Allende. We discuss a procedure and necessary assumptions for the partitioning of measured data into cosmogenic, radiogenic, implanted, and indigenous noble gas components. For stone meteorites, we derive a cosmogenic ratio 20Ne/22Ne of 0.80 ± 0.03 and a trapped solar 4He/3He ratio of 3310 ± 130 using our own and literature data. Chondrules and matrix from nine meteorites were analyzed. Data from Dhajala chondrules suggest that some of these may have experienced precompaction irradiation by cosmic rays. The other chondrules and matrix samples yield consistent cosmic-ray exposure (CRE) ages within experimental errors. Some CRE ages of some of the investigated meteorites fall into clusters typically observed for the respective meteorite groups. Only Bath's CRE age falls on the 7 Ma double-peak of H chondrites, while Ogi's fits the 22 Ma peak. The studied chondrules contain trapped 20Ne and 36Ar concentrations in the range of 10-6-10-9 cm3 STP/g. In most chondrules, trapped Ar is of type Q (ordinary chondritic Ar), which suggests that this component is indigenous to the chondrule precursor material. The history of the Cullison chondrite is special in several respects: large fractions of both CR-produced 3He and of radiogenic 4He were lost during or after parent body breakup, in the latter case possibly by solar heating at small perihelion distances. Furthermore, one of the matrix samples contains constituents with a regolith history on the parent body before compaction. It also contains trapped Ne with a 20Ne/22Ne ratio of 15.5 ± 0.5, apparently fractionated solar Ne.

Eugster, Otto; Lorenzetti, Silvio; KräHenbühl, Urs; Marti, Kurt

2007-08-01

200

Modeling the atmospheric dispersion of accidentally released heavy gases from photovoltaic cell manufacturing facilities  

Microsoft Academic Search

Many hazardous gases used in the photovoltaic cell industry are heavier than air. Following an accidental release, their dispersion in air, differs from the dispersion of a neutrally buoyant gas and, as such, it requires special consideration. This report reviews and evaluates basic theoretical models and selected computer codes. Model results also are compared with experimental data. Dispersion of selected

Fthenakis

1986-01-01

201

Noble Gas Thermometry and Hydrologic Ages: Evidence for Late Holocene Warming in Southwest Texas  

Microsoft Academic Search

Paleoclimatic reconstruction through the use of noble gases dissolved in groundwater has been the object of numerous studies in recent years. Unlike many other continental temperature proxies, noble gases have the advantage of providing direct information on atmospheric temperatures at the time rainwater penetrated the ground and joined a particular groundwater reservoir. In recent years, new methods for determination of

Maria Clara Castro; P. Goblet

2003-01-01

202

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

203

Removal of Noble Gases by Selective Absorption.  

National Technical Information Service (NTIS)

Process performance and reliability have been demonstrated on an engineering scale with 10 years of pilot plant operation, including extended testing with exp 85 Kr, exp 133 Xe, and exp 131 I. The selective absorption process is based on exploitation of s...

J. R. Merriman M. J. Stephenson B. E. Kanak D. K. Little

1980-01-01

204

Preserving noble gases in a convecting mantle  

Microsoft Academic Search

High 3He\\/4He ratios sampled at many ocean islands are usually attributed to an essentially undegassed lower-mantle reservoir with high 3He concentrations. A large and mostly undegassed mantle reservoir is also required to balance the Earth's 40Ar budget, because only half of the 40Ar produced from the radioactive decay of 40K is accounted for by the atmosphere and upper mantle. However,

Helge M. Gonnermann; Sujoy Mukhopadhyay

2009-01-01

205

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

206

A small 1 MeV electron accelerator for measuring heavy metal concentrations in smokestack gases  

NASA Astrophysics Data System (ADS)

A low-current electron beam may be used as a diagnostic tool to measure the concentrations of heavy metals (Cd, Pb, Hg) present in the flue gas particulates produced by smelters or cement kilns. A small electron accelerator is being constructed as part of a prototype emissions monitoring system. The electron beam energy has a design energy of 1 MeV, a peak current of 5 mA, and a duty factor of 0.1 percent. In this paper, we discuss the results of a set of EGS4 calculations used to model the transport properties of a 1 MeV electron beam passing through a thin vacuum window and the flue gas. Since the accelerator will be mounted in a harsh environment, we have investigated the effects of temperature variations on the linac structure and RF power source. The present status of the accelerator construction project is presented.

Reppond, A.; Redden, D. P.; Meitzler, C. R.; Swenson, D. A.

1997-05-01

207

Optimizing macromolecular tandem mass spectrometry of large non-covalent complexes using heavy collision gases  

NASA Astrophysics Data System (ADS)

We evaluated and optimized conditions for tandem mass spectrometry on macromolecular protein complexes, using a modified Q-ToF instrument varying the gas pressure inside the hexapole collision cell, and studied the influence of using different collision gases, e.g. argon, krypton and xenon. These variations affected ion transmission through the instrument and dissociation efficiency In particular the high mass fragment ions were generated more readily and transmitted more efficiently using the heavier xenon as collision gas. We used the 800 kDa GroEL 14-mer chaperone machinery for these initial studies. Applying the optimized tandem mass spectrometry conditions, i.e. relatively high pressures and xenon as collision gas, we studied in detail the influence the binding of one and two gp5 substrate proteins had on the gas-phase dissociation of the chaperonin complex constructing break-down diagrams. We observed that the binding of substrate polypeptides had a significant effect on the gas-phase stability of the chaperonin complex, with the complex containing one and two substrate molecules being less susceptible towards dissociation than the substrate free GroEL. Interestingly, the GroEL:gp5 and GroEL:(gp5)2 complexes dissociate exclusively via the elimination of GroEL monomeric ions, indicating that both gp5 substrates are likely encapsulated inside the two cavities of, respectively, the cis and trans ring of the GroEL. From all data acquired, we conclude that the heavier xenon is the preferred collision gas for tandem mass spectrometry on very large macromolecular complexes.

Lorenzen, Kristina; Versluis, Cees; van Duijn, Esther; van den Heuvel, Robert H. H.; Heck, Albert J. R.

2007-12-01

208

Heterogeneous upper mantle Ne, Ar and Xe isotopic compositions and a possible Dupal noble gas signature recorded in basalts from the Southwest Indian Ridge  

NASA Astrophysics Data System (ADS)

Variations in heavy noble gas (Ne, Ar, Xe) isotopic compositions provide unique insights into the nature of heterogeneities in the mantle. However, few precise constraints on mantle source heavy noble gas isotopic compositions are available due to ubiquitous shallow-level atmospheric contamination. As a result, the extent of heterogeneity in mid-ocean ridge basalt (MORB) mantle source Ne, Ar and Xe isotopic compositions is unknown. Basalts from the ultra-slow spreading Southwest Indian Ridge (SWIR) between 7°E and 25°E exhibit remarkable variability in He isotopic composition: SWIR 4He/3He spans half the total range observed in all mantle-derived basalts. Therefore, basalts from the SWIR provide a unique window into upper mantle heterogeneity and present an ideal opportunity to characterize variations in upper mantle heavy noble gas isotopic composition. Here we present new high-precision Ne, Ar and Xe isotopic compositions as well as He, CO2, Ne, Ar and Xe abundances measured in basalt glasses from the SWIR. After correcting the measured values for shallow-level atmospheric contamination, significant and systematic variations in mantle source Ne, Ar and Xe compositions are observed. We note that large variations in source 40Ar/36Ar and 129Xe/130Xe are observed in basalts removed from the influence of known hotspots, indicating a heterogeneous mid-ocean ridge basalt source. Thus, SWIR heavy noble gas data reveal a greater degree of source heterogeneity than is evident in the 4He/3He systematics alone. The observed heavy noble gas isotopic heterogeneities imply that the average MORB source 40Ar/36Ar and 129Xe/130Xe ratios are not yet well-determined.Variation in MORB source 40Ar/36Ar and 129Xe/130Xe at a given 4He/3He and 21Ne/22Ne may reflect heterogeneous recycling of atmospheric Ar and Xe. In particular, we find low mantle source 40Ar/36Ar and 129Xe/130Xe ratios in the eastern region of the study area, which may reflect the noble gas signature of the Dupal mantle domain. Our observations require that the sampled mantle domain either is very ancient (>4.45 Ga) or has been metasomatized by subduction zone fluids carrying recycled atmospheric Ar and Xe. However, our Xe isotopic measurements indicate that differences between MORB and ocean island basalt (OIB) source noble gas compositions cannot be explained by recycling of atmospheric noble gases alone. Instead, a relatively undegassed mantle reservoir is required to account for OIB noble gases. The SWIR data demonstrate that the reservoir supplying primordial noble gases to mantle plumes differentiated from the MORB source early in Earth history, and the two reservoirs have not been homogenized over 4.45 Ga of mantle convection.

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

2012-12-01

209

NO2Assisted Soot Regeneration Behavior in a Diesel Particulate Filter with Heavy-Duty Diesel Exhaust Gases  

Microsoft Academic Search

A major concern in operating a diesel engine is how to reduce the soot emission from the exhaust gases, as soot has a negative effect on both human health and the environment. More stringent emission regulations make the diesel particulate filter (DPF) an indispensable after-treatment component to reduce diesel soot from exhaust gases. The most important issue in developing an

Jong Hun Kim; Man Young Kim; Hyong Gon Kim

2010-01-01

210

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 (â??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...

211

Noble gas geochemistry in thermal springs  

SciTech Connect

The composition of noble gases in both gas and water samples collected from Horseshoe Spring, Yellowstone National Park, was found to be depth dependent. The deeper the sample collection within the spring, the greater the enrichment in Kr, Xe, radiogenic {sup 4}He, and {sup 40}Ar and the greater the depletion in Ne relative to {sup 36}Ar. The compositional variations are consistent with multi-component mixing. The dominant component consists of dissolved atmospheric gases acquired by the pool at the surface in contact with air. This component is mixed in varying degree with two other components, one each for gas and water entering the bottom of the pool. The two bottom components are not in equilibrium. In Horseshoe Spring, the bubbles entering at the bottom strip the atmospheric-derived pool gases from the surrounding water while en route to the surface. If the original bottom bubbles are noble gas, as in the case of Horseshoe, the acquired pool gases can then quickly obliterate the original bubble composition. These results are used to demonstrate that Yellowstone spring surface gas samples, and perhaps similarity sampled thermal springs from other hydrothermal systems, have gas abundances that depend more on spring morphology than processes occurring deeper in the hydrothermal system.

Kennedy, B.M.; Reynolds, J.H. (Univ. of California, Berkeley (USA)); Smith, S.P. (Charles Evans and Associates, Redwood City, CA (USA))

1988-07-01

212

DFT Energetics of Noble Gas Impurities and Schottky Defects in UO2  

Microsoft Academic Search

There is a strong need to better understand the mechanisms of nuclear fuel swelling in uranium dioxide (UO2) due to formation of fission product gases. Using density functional theory (DFT+U) calculations, we have explored the energetics of noble gases in UO2, Schottky defects (SD) in UO2, and the interaction between these defects. We find: (i) The noble gas atoms show

Alexander Thompson; Chris Wolverton

2009-01-01

213

Noble gas investigations of lunar rocks 10017 and 10071  

Microsoft Academic Search

The noble gases He, Ne, Ar, Kr and Xe and also K and Ba were measured in the Apollo 11 igneous rocks 10017 and 10071, and in an ilmenite and two feldspar concentrates separated from rock 10071. Whole rock K\\/Ar ages of rocks 10017 and 10071 are (2350 ± 60) × 10 6 yr and (2880 ± 60) × 10

P. Eberhardt; J. Geiss; H. Graf; N. Groegler; U. Kraehenbuehl; H. Schwaller; A. Stettler

1974-01-01

214

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

215

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

216

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

217

The Noble Savage.  

ERIC Educational Resources Information Center

|Traces the history of the "noble savage" concept, from the romantic view of the fifteenth through eighteenth centuries of American Indians as holdovers from the "golden age," to current media images of the medicine man or the Indian princess. Discusses how this patronizing stereotype continues to undermine Indian identity. (SV)|

Greer, Sandy

1993-01-01

218

Noble Gas Study On Deep Mine Waters, South Africa  

NASA Astrophysics Data System (ADS)

We analyzed the dissolved noble gases of 16 water samples taken in the deep gold mines in the Witwatersrand Basin, South Africa. The fissure and borehole waters originate from 0.98 to 3.3 km depth. The noble gas data (He, Ne, Ar, Kr, Xe concentration and isotope ratios), in combination with 36Cl, ? dD, ? 18O and 14C data, are used to characterize - ideally - pristine formation water pockets in the deep subsurface. They also provide information of hydrodynamic relevance. A sample taken from the lower parts of the local dolomite aquifer is fresh water of meteoric origin, with a 14C-age of about 5.8k years and a noble gas temperature of about 18 +/- 1° C. This is the shallowest (0.98 km b.s.l.) and youngest sample of the data set. In comparison, all other samples show a noble gas abundance pattern indicating losses of the non atmospheric noble gases up to 80%. This undersaturation is most likely the result of a significant pressure release of the water, either in the formation due to the mining activity or during sampling. In the latter case, the losses of the noble gases are an artifact and should be corrected for. 4He concentrations range between 10-4 to 10-3 cm3STP g-1, the Ar40/36 ratios range from some 300 to above 10,000, Xe134/132- and Xe136/132- ratios up to 0.42 and 0.37, respectively. Model results rule out the possibility that these high ratios are mainly caused by fractionation by diffusion during the degassing of the water. All results so far indicate very long subsurface residence times; for selected samples we calculate minimum ages of the order of some ten million years.

Lippmann, J.; Stute, M.; Moser, D. P.; Hall, J.; Lin, L.; Ward, J. A.; Slater, G. F.; Onstott, T. C.; Schlosser, P.

2001-12-01

219

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

220

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

Microsoft Academic Search

Noble gas investigation was organized for the possibility of measuring noble gases in martian rocks and air by future robotic missions such as MSL. We suggest the possibility of K-Ar age dating by lab simulation experiments on MORB and martian meteorites.

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

2009-01-01

221

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

NASA Astrophysics Data System (ADS)

Noble gas investigation was organized for the possibility of measuring noble gases in martian rocks and air by future robotic missions such as MSL. We suggest the possibility of K-Ar age dating by lab simulation experiments on MORB and martian meteorites.

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

2009-03-01

222

Large atmospheric noble gas excesses in a shallow aquifer in the Michigan Basin as indicators of a past mantle thermal event  

NASA Astrophysics Data System (ADS)

Significant atmospheric noble gas excesses in aquifer systems have systematically been linked to increased hydrostatic pressure, either due to increased water table levels or due to the development of ice cover. Measured noble gases (Ne, Ar, Kr, and Xe) in the shallow Saginaw aquifer in the Michigan Basin display both moderate (˜20–60% Ne excess) and large (˜80?>120% Ne excess) excesses of atmospheric noble gases with respect to air saturated water for modern recharge conditions. All large atmospheric noble gas excesses are located in the main discharge area of the Michigan Basin, in the Saginaw Lowlands region.

Warrier, Rohit B.; Castro, M. Clara; Hall, Chris M.; Lohmann, Kyger C.

2013-08-01

223

Challenges on the way to noble gas temperatures on speleothems  

NASA Astrophysics Data System (ADS)

In the last years, speleothems gained importance as a paleoclimate archive. Nonetheless, so far no proxy in speleothems has really gained acceptance as a commonly used paleotemperature indicator. Application of the noble gas thermometer to speleothem fluid inclusions promises in principle the determination of absolute paleotemperatures. Kluge et al. (2008) and Scheidegger et al. (2010) showed that the precise measurement of noble gas concentrations on fluid inclusions is possible in general. Unfortunately, the extraction and measurement technique presented by Kluge et al. (2008) allowed the determination of reasonable noble gas temperatures (NGTs) only for some samples. Some of the problems which occurred as well as some (possible) solutions will be presented. A general problem for the application of the noble gas thermometer on speleothems is the presence of air-filled inclusions in the speleothem. Noble gases released from them mask the temperature signal of the noble gases dissolved in the water-filled inclusions. In order to reduce the air/water volume ratio, a stepwise extraction technique has been developed successfully. However, often the different extraction steps on one sample lead to temperatures that do not agree well with each other. Samples of the stalagmite H12 from Hoti Cave in Oman showed an excess in neon. A similar neon excess was found by Scheidegger et al. (2010) but for a larger number of samples. They suggest that helium and neon can be situated in voids between the atoms forming the carbonate lattice. However, a sample of stalagmite H12 showed neon excess in the very first extraction step, which is not expected for a matrix related component. The NGTs reported by Kluge et al. (2008) seemed to be 2 to 3 °C too low compared to independent temperature reconstructions. In order to investigate this offset and the overall accuracy of the extraction and measurement technique, tiny amounts of air-equilibrated water (AEW) were measured as test samples. In a first test with these so-called ?AEWs the heavier noble gases (Ar, Kr, Xe) seemed to be underestimated, while a second measurement run did not show this offset. Overall, these tests demonstrated the good reproducibility of better than 5% for the noble gas concentrations.

Marx, T.; Aeschbach-Hertig, W.

2012-04-01

224

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

225

A combined vacuum crushing and sieving (CVCS) system designed to determine noble gas paleotemperatures from stalagmite samples  

NASA Astrophysics Data System (ADS)

This paper presents a novel extraction device for water and noble gases from speleothem samples for noble gas paleotemperature determination. The "combined vacuum crushing and sieving (CVCS) system" was designed to reduce the atmospheric noble gas contents from air inclusions in speleothem samples by up to 2 orders of magnitude without adsorbing atmospheric noble gases onto the freshly produced grain surfaces, a process that had often hampered noble gas temperature (NGT) determination in the past. We also present the results from first performance tests of the CVCS system processing stalagmite samples grown at a known temperature. This temperature is reliably reproduced by the NGTs derived from Ar, Kr, and Xe extracted from the samples. The CVCS system is, therefore, suitable for routine determinations of accurate NGTs. In combination with stalagmite dating, these NGTs will allow reconstructing past regional temperature evolutions, and also support the interpretation of the often complex stable isotope records preserved in the stalagmites' calcite.

Vogel, Nadia; Brennwald, Matthias S.; Fleitmann, Dominik; Wieler, Rainer; Maden, Colin; Süsli, Andreas; Kipfer, Rolf

2013-07-01

226

Noble gas, a potential nuclear proliferation indicator  

SciTech Connect

In the post-Cold War era, it appears that nuclear proliferation will be a continuing problem. At least one reliable technique to detect nuclear activities is needed to deter potential proliferators. This paper proposes a candidate technique for detection. Early efforts to measure nuclear fuel performance resulted in the consideration of a variety of potential techniques. In 1965, Maeck proposed determination of nuclear fuel burnup based on the ratio of two stable fission product isotopes of the same element. Maeck proposed using three ratios: [sup 84]Kr/[sup 83]Kr, [sup 132]Xe/[sup 131]Xe, and [sup 144]Nd/[sup 143]Nd. More recent work includes useful application of krypton and xenon isotope correlation techniques to safeguards at nuclear fuel reprocessing facilities. The safeguards application requires very precise measurement of the fission product isotopes, detailed fuel exposure history, and knowledge of the neutron spectrum. Meeting all these requirements is extremely difficult and requires carefully controlled conditions. The most likely scenario for a proliferator to produce nuclear material suitable for weapons applications is reprocessing of reactor fuel to recover the plutonium. Since useful amounts of plutonium are produced in all uranium-fueled reactors, reprocessing the reactor fuel would be much easier and less expensive than mining and enriching uranium to weapons-grade material. Reprocessing nuclear reactor fuel releases the noble gases krypton and xenon from the fuel. Because capture of the noble gases is difficult, expensive, and produces a radiation hazard, the gases will normally be released during reprocessing. These factors provide the basis for this proposed technique of detecting proliferators.

Chapman, T.C. (Westinghouse Idaho Nuclear Company, Idaho Falls (United States))

1993-01-01

227

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

228

Investigation of the noble gas solubility in H2O-CO2 bearing silicate liquids at moderate pressure II: the extended ionic porosity (EIP) model  

Microsoft Academic Search

A semi-theoretical model is proposed to predict partitioning of noble gases between any silicate liquid and a H2O-CO2 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

P. M. Nuccio; A. Paonita

2000-01-01

229

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

Microsoft Academic Search

A semi-theoretical model is proposed to predict partitioning of noble gases between any silicate liquid and a H2O–CO2 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

P. M. Nuccio; A. Paonita

2000-01-01

230

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

231

Non-Noble Colloidal Catalysts.  

National Technical Information Service (NTIS)

This investigation is concerned with the development of non-noble metal autocatalytic colloids suitable for initiating electroless copper plating of printed wiring boards (PWB's). Additionally, the processing materials and parameters are selected and adju...

N. Feldstein

1979-01-01

232

NOBLE GAS PRODUCTION FROM MERCURY SPALLATION AT SNS  

SciTech Connect

Calculations for predicting the distribution of the products of spallation reactions between high energy protons and target materials are well developed and are used for design and operational applications in many projects both within DOE and in other arenas. These calculations are based on theory and limited experimental data that verifies rates of production of some spallation products exist. At the Spallation Neutron Source, a helium stream from the mercury target flows through a system to remove radioactivity from this mercury target offgas. The operation of this system offers a window through which the production of noble gases from mercury spallation by protons may be observed. This paper describes studies designed to measure the production rates of twelve noble gas isotopes within the Spallation Neutron Source mercury target.

DeVore, Joe R [ORNL; Lu, Wei [ORNL; Schwahn, Scott O [ORNL

2013-01-01

233

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

234

First-principles study of noble gas impurities and defects in UO2  

Microsoft Academic Search

We performed a series of density functional theory + U (DFT + U) calculations to explore the energetics of various defects in UO2, i.e., noble gases (He, Ne, Ar, Kr, Xe), Schottky defects, and the interaction between these defects. We found the following: (1) collinear antiferromagnetic UO2 has an energy-lowering distortion of the oxygen sublattice from ideal fluorite positions; (2)

Alexander E. Thompson; C. Wolverton

2011-01-01

235

Near Threshold Polarization of Line Radiation From Noble Gases  

Microsoft Academic Search

Line radiation from atoms or ions excited with asial symmetry by electron beams is generally linearly polarized. At the excitation threshold, this polarization has a kinematically required value resulting from exclusive prodution of orbital magnetic sublevels with m_l=0. In the large majority of cases involving group I and II atoms or ions the polarization falls to less than half this

K. W. Trantham; M. E. Johnston; T. J. Gay

1996-01-01

236

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

237

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

238

Shock wave fractionated noble gases in the early solar system  

Microsoft Academic Search

Many processes in the active star-forming regions are accompanied by strong shock waves, in acceleration by which the nuclear-active particles form the power-law energy spectrum of high rigidity: F(> E0) ˜ Egamma , with the spectral index gamma <= 1.5-2. It must affect the production rates of spallogenic components of the isotopes, whose excitation functions depend on the shape of

G. K. Ustinova

2001-01-01

239

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.

240

Research of medical gases in Poland  

PubMed Central

Research of medical gases is well established in Poland and has been marked with the foundation of several professional societies. Numerous academic centers including those dealing with hyperbaric and diving medicine conduct studies of medical gases, in vast majority supported with intramural funds. In general, Polish research of medical gases is very much clinical in nature, covering new applications and safety of medical gases in medicine; on the other hand there are several academic centers pursuing preclinical studies, and elaborating basic theories of gas physiology and mathematical modeling of gas exchange. What dominates is research dealing with oxygen and ozone as well as studies of anesthetic gases and their applications. Finally, several research directions involving noble gas, hydrogen and hydrogen sulfide for cell protection, only begin to gain recognition of basic scientists and clinicians. However, further developments require more monetary spending on research and clinical testing as well as formation of new collective bodies for coordinating efforts in this matter.

2013-01-01

241

The noble cause: An empirical assessment  

Microsoft Academic Search

Literature on police ethics has employed the term “noble cause” to describe a utilitarian orientation toward crime control. No empirical research, however, has systematically investigated the noble cause, a shortcoming addressed in this study. A survey of deputies in a western sheriff's office provided the setting for the current research. Twelve items tapping the noble cause revealed a multidimensional latent

John Crank; Dan Flaherty; Andrew Giacomazzi

2007-01-01

242

Solution of protein crystallographic structures by high-pressure cryocooling and noble-gas phasing.  

PubMed

Room-pressure flash-cryocooling of protein crystals is the standard way to reduce radiation damage during data collection. Typically, it is necessary to find cryoprotection conditions by trial and error, a process that is not always successful. Recently, a new method, high-pressure cryocooling, was developed that does not require penetrative cryoprotectants and typically yields very high quality diffraction. Since this method involves helium gas as a pressurizing medium, it was of great interest to see whether the method could be extended to diffraction phasing by the incorporation of heavy noble gases such as krypton. A modified Kr-He high-pressure cyrocooling procedure is described wherein crystals are first pressurized with krypton gas to 10 MPa for 1 h. The krypton pressure is then released and the crystals are repressurized with helium over 150 MPa and cooled to liquid-nitrogen temperatures. Porcine pancreas elastase (PPE; 240 residues, 26 kDa) was selected as a test case for this study. Excellent diffraction was achieved by high-pressure cryocooling without penetrating cryoprotectants. A single 0.31 occupied krypton site in a PPE molecule [Bijvoet amplitude ratio (|DeltaF|/F) of 0.53%] was successfully used for SAD phasing at 1.3 A. This method has the potential to greatly simplify obtaining protein structures. PMID:16790924

Kim, Chae Un; Hao, Quan; Gruner, Sol M

2006-06-20

243

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

244

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

NASA Astrophysics Data System (ADS)

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 mantle is solar-like, with light (high) 20Ne/22Ne relative to the atmosphere [2]; (ii) mantle Xe has higher 128Xe/130Xe than the atmosphere [3], which carries an extreme heavy isotope enriched mass fractionation signature of >3%/amu (iii) most of the radiogenic Xe from l29I and 244Pu decay in the Earth is not present either in the mantle or in the atmosphere; (iv) the inferred abundances of noble gases in the deep Earth "plume source" are insufficient to generate the present atmospheric abundances, even for whole mantle degassing; and (v) mantle noble gases indicate a 2 component structure, with solar light gases (He and Ne) and planetary heavy gases [4]. The present day noble gas budgets (and likely also N2) must derive from late accretion of a volatile-rich "veneer." This is stage III. Stage II is a naked (no atmosphere) epoch indicated by evidence for Hadean degassing of 244Pu (T1/2 = 80 Ma) fission Xe from the whole mantle, which was not retained in the present atmosphere. The naked stage must have lasted for more than ~200 Ma, and was supported by the early intense solar EUV luminosity. Stage I, a massive solar-composition protoatmosphere, occurred during the Earth's early accretion phase. Its existence is indicated by the presence of the solar gas component in the Earth. This is not attributable to subduction of solar wind rich cosmic dust, or solar wind irradiation of coagulating objects. It is best explained by accretion of a solar composition atmosphere from the nebula. This provided a thermal blanket supporting a magma ocean in which solar gases dissolved. Under these conditions the H2-rich protoatmosphere was oxidized by reaction with the surface magma to yield H20(g) and gained further opacity, supporting a reducing high temperature condition which controlled liquid-liquid siderophile segregation near the magma ocean surface. According to this scenario, the planetary gas component in the mantle would have been accreted subsequently from planetesimals infalling after blowoff of the protoatmosphere. The impact-degassed portion was lost to space. Modeling of Xe isotope fractionahon by hydrodynamic escape is problematic because 84Kr/130Xe in the atmosphere is very close to solar. Hydrodynamic escape fraction (HEF) of a planetary-pattern degassed atmosphere cannot produce this, and HEF of a solar-pattern primordial protoatmosphere cannot preserve it. Comets have been suggested as a potential source of atmospheric 36Ar-84Kr-130Xe, based on ice trapping expenments at 50 degrees K [5]. However, 22Ne-36Ar-84Kr has a planetary-like pattem, whereas Ne does not condense in ice at 50 degrees K. As cometary ice may contain degassed icy molecular cloud (MC) grains formed at lower temperatures [6], experiments with analogs may hold the key to the conundrum of planetary-like 22Ne-36Ar-84Kr and solar-like 84Kr-130Xe, common to both Earth and Mars. References: [1] Jacobsen S. B. (1995) Eos Trans. AGU, 76, S42; O'Nions R. K. and Tolstikhin I. N. (1995) Eos Trans. AGU, 76, S43; Wasserburg G. J. and Porcelli D. (1995) Eos Trans. AGU, 76, S41. [2] E.g., Honda M. et al. (1993) GCA, 57, 859-874. [3] Caffee M. W. et al. (1988) LPS XIX, 154-155; Jacobsen S. B. and Harper C. L. Jr. (1995) AGU Monograph, in press. [4] Harper C. L. Jr. and Jacobsen S. B. (1995) Eos Trans. AGU, 76, S42, and Nature, submitted. [5] Owen T. et al. (1992) Nature, 358, 43-45. [6] Lunine J. I. et al. (1991) Icarus, 94, 333-344.

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

1995-09-01

245

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

246

The capture of slow antiprotons by noble gas atoms  

NASA Astrophysics Data System (ADS)

The capture of slow antiprotons (impact energies less than 1.0 au) by the noble gases krypton and xenon is studied following the paper of Briggs at al, where the transient collision complex is treated as a diatomic molecule with the positively-charged atomic ion and antiproton as `nuclei'. Estimates of the population of long-lived `circular' states suggest that the probability of capture of antiprotons into such states is negligible. The capture cross sections for Kr and Xe are two orders of magnitude smaller than for He in agreement with experimental data.

Briggs, J. S.; Jakimovski, D.; Solov'ev, E. A.

2005-10-01

247

A new stopping power parameterization for 0.1–15 MeV\\/nucleon heavy and superheavy ions in solids and gases  

Microsoft Academic Search

Electronic stopping powers of heavy ions in several media are deduced from the corresponding proton data by using new effective charge parameterizations. Separate sets of parameters were deduced for solid and gaseous materials using the available data for heavy ions in the energy range from 0.1 to 15MeV\\/nucleon. Using these results, predictions are made for stopping powers of heavy and

M. Barbui; D. Fabris; M. Lunardon; S. Moretto; G. Nebbia; S. Pesente; G. Viesti; K. Hagel; J. B. Natowitz; R. Wada

2010-01-01

248

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

249

Demonstration of noble gas collection using the cryogenic technique  

SciTech Connect

Monitoring devices used for detecting and measuring airborne radioactive noble gases in stack emissions have been limited in their precision and detection capability. Cryogenic sampling is one method used for sampling gamma emitting radioactive gases in stack emissions. A cryogenic air sampler, originally developed at the Oak Ridge National Laboratory (ORNL) and further developed by the Systems Demonstration and Environmental Air Sampling Group (SDEASG) at the Oak Ridge Gaseous Diffusion Plant (ORGDP) is being tested. The cryogenic sampler will be used to study the off-gas from various emission points at ORNL after completion of the preliminary study by SDEASG. Work is currently under way to demonstrate the effectiveness of the sampler and the efficiency of the sampling method. Various tests have been and are being conducted to determine the sample collection techniques which will result in the greatest sample transfer efficiency, sampling precision, and gamma emission counting efficiencies. 4 figs., 2 tabs.

Moser, L.V.; Delzer, D.B.

1988-09-01

250

The noble gas systematics of late-orogenic H 2O-CO 2 fluids, Mt Isa, Australia  

NASA Astrophysics Data System (ADS)

The noble gases (He, Ne, Ar, Kr and Xe) are powerful geochemical tracers because they have distinctive isotopic compositions in the atmosphere, crust and mantle. This study illustrates how noble gases can be used to trace fluid origins in high-temperature metamorphic and mineralising environments; and at the same time provides new information on the composition of noble gases in deeper parts of the crust than have been sampled previously. We report data for H 2O and CO 2 fluid inclusions trapped at greenschist to amphibolite facies metamorphic conditions associated with three different styles of mineralisation and alteration in the Proterozoic Mt Isa Inlier of Australia. Sulphide fluid inclusions are dominated by crustal 4He. However, co-variations in fluid inclusion 20Ne/ 22Ne, 21Ne/ 22Ne, 40Ar/ 36Ar and 136Xe/ 130Xe indicate noble gases were derived from three or more reservoirs. In most cases, the fluid inclusions elemental noble gas ratios (e.g. Ne/Xe) are close to the ranges expected in sedimentary and crystalline rocks. However, the elemental ratios have been modified in some of the samples providing evidence for independent pulses of CO 2, and interaction of CO 2 with high-salinity aqueous fluids. Compositional variation is attributed to mixing of: (i) magmatic fluids (or deeply sourced metamorphic fluids) characterised by basement-derived noble gases with 20Ne/ 22Ne ˜ 8.4, 21Ne/ 22Ne ˜ 0.4, 40Ar/ 36Ar ˜ 40,000 and 136Xe/ 130Xe ˜ 8; (ii) basinal-metamorphic fluids with a narrow range of compositions including near-atmospheric values and (iii) noble gases derived from the meta-sedimentary host-rocks with 20Ne/ 22Ne ˜ 8-9.8, 21Ne/ 22Ne < 0.1, 40Ar/ 36Ar < 2500 and 136Xe/ 130Xe ˜ 2.2. These data provide the strongest geochemical evidence available for the involvement of fluids from two distinct geochemical reservoirs in Mt Isa's largest ore deposits. In addition the data show how noble gases in fluid inclusions can provide information on fluid origins, the composition of the crust's major lithologies, fluid-rock interactions and fluid-fluid mixing or immiscibility processes.

Kendrick, M. A.; Honda, M.; Oliver, N. H. S.; Phillips, D.

2011-03-01

251

NEST: Noble Element Simulation Technique  

NASA Astrophysics Data System (ADS)

NEST (Noble Element Simulation Technique) offers comprehensive, accurate, and precise simulation of the excitation, ionization, and corresponding scintillation and electroluminescence processes in liquid noble elements, useful for direct dark matter detectors, double beta decay searches, PET scans, and general radiation detection technology. Written in C++, NEST is an add-on module for the Geant4 simulation package that incorporates more detailed physics than is currently available into the simulation of scintillation. NEST is of particular use for low-energy nuclear recoils. All available liquid xenon data on nuclear recoils and electron recoils to date have been taken into consideration in arriving at the current models. NEST also handles the magnitude of the light and charge yields of nuclear recoils, including their electric field dependence, thereby shedding light on the possibility of detection or exclusion of a low-mass dark matter WIMP by liquid xenon detectors.

Szydagis, M.; Barry, N.; Kazkaz, K.; Mock, J.; Stolp, D.; Sweany, M.; Tripathi, M.; Uvarov, S.; Walsh, N.; Woods, M.

2013-07-01

252

Covalency of noble metal halides  

Microsoft Academic Search

The covalency is calculated for several compounds with diamond structure, zinc blend structure and rock salt structure using the DV-X? cluster method. The covalency of noble metal halides is in the border between that of the four-fold coordinated compounds and that of the six-fold coordinated compounds. These calculation results on the covalency support the tendency of the Phillips's ionicity. The

S. Ono; M. Kobayashi; T. Tomoyose

2005-01-01

253

A new stopping power parameterization for 0.1-15 MeV/nucleon heavy and superheavy ions in solids and gases  

NASA Astrophysics Data System (ADS)

Electronic stopping powers of heavy ions in several media are deduced from the corresponding proton data by using new effective charge parameterizations. Separate sets of parameters were deduced for solid and gaseous materials using the available data for heavy ions in the energy range from 0.1 to 15 MeV/nucleon. Using these results, predictions are made for stopping powers of heavy and superheavy elements with Z = 100-130 in the energy range of 0.5-15 MeV/nucleon.

Barbui, M.; Fabris, D.; Lunardon, M.; Moretto, S.; Nebbia, G.; Pesente, S.; Viesti, G.; Hagel, K.; Natowitz, J. B.; Wada, R.

2010-08-01

254

Interpreting noble-gas concentrations as proxies for salinity and temperature in the world's largest soda lake (Lake Van, Turkey)  

NASA Astrophysics Data System (ADS)

In this work we present noble-gas concentration profiles measured in the water column and in the sediment pore water of the Earth's largest soda lake: Lake Van (eastern Anatolia, Turkey). The concentrations of noble gases (in particular Ar, Kr, and Xe) in the water body deviate significantly from the expected equilibrium concentrations calculated from the in situ temperature and salinity using existing solubility functions for seawater. The specific chemical composition of the water of the soda lake seems to be responsible for the observed deviations. Our measurements allow the identification and quantification of salinity factors that can be applied to correctly calculate the noble-gas equilibrium concentrations for the lake. These salinity factors provide a solid and robust empirical basis for the interpretation of noble-gas concentration signals measured in the sediment pore water of Lake Van in terms of palaeosalinity and palaeotemperature.

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

2012-10-01

255

Effect of the Fractional Composition of a Fine-Grained Adsorbent on the Efficiency with Which Furnace Gases are Cleaned of Heavy Metals  

Microsoft Academic Search

Air contains a large number of substances of natural and anthropogenic origins, and both the qualitative and quantitative composition of air is continually changing. Among the substances in air are water vapor, dust, and various chemicals present in the form of gases, vapors, and aerosols. The dispersed phase in an aerosol can be a solid or a liquid. The sizes

G. V. Kashakashvili; B. G. Gogichaishvili; O. Sh. Mikadze; G. G. Tsnoriashvili; G. A. Lomtatidze; Z. S. Svanidze; A. N. Gagnidze

2004-01-01

256

Greenhouse Gases  

MedlinePLUS

... support life as we know it. Without the greenhouse effect, the average temperature of the Earth would be ... regulated independently of its warming effects. More about greenhouse gases’ effect on the climate » Also on Energy Explained Energy ...

257

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 1H2O 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

258

Solvation theory to provide a molecular interpretation of the hydrophobic entropy loss of noble-gas hydration  

Microsoft Academic Search

An equation for the chemical potential of a dilute aqueous solution of noble gases is derived in terms of energies, force and torque magnitudes, and solute and water coordination numbers, quantities which are all measured from an equilibrium molecular dynamics simulation. Also derived are equations for the Gibbs free energy, enthalpy and entropy of hydration for the Henry’s law process,

Sheeba Jem Irudayam; Richard H Henchman

2010-01-01

259

Solvation theory to provide a molecular interpretation of the hydrophobic entropy loss of noble-gas hydration  

Microsoft Academic Search

An equation for the chemical potential of a dilute aqueous solution of noble gases is derived in terms of energies, force and torque magnitudes, and solute and water coordination numbers, quantities which are all measured from an equilibrium molecular dynamics simulation. Also derived are equations for the Gibbs free energy, enthalpy and entropy of hydration for the Henry's law process,

Sheeba Jem Irudayam; Richard H. Henchman

2010-01-01

260

Noble metal additive modulation of gas sensitivity of BaSnO 3, explained by a work function based model  

Microsoft Academic Search

Barium stannate, a semiconducting oxide with cubic perovskite structure, has been prepared by the thermal decomposition method. Of its several applications, this material has proved to be one of the successful candidates for chemical sensors to detect toxic and inflammable gases. BaSnO3 was incorporated with different noble metal additives and the gas sensing behavior of these materials to various reducing

C. V. Gopal Reddy; S. V. Manorama; V. J. Rao; Arun Lobo; S. K. Kulkarni

1999-01-01

261

Electric dipole polarizabilities at imaginary frequencies for hydrogen, the alkali-metal, alkaline-earth, and noble gas atoms  

SciTech Connect

The electric dipole polarizabilities evaluated at imaginary frequencies for hydrogen, the alkali-metal atoms, the alkaline-earth atoms, and the noble gases are tabulated along with the resulting values of the atomic static polarizabilities, the atom-surface interaction constants, and the dispersion (or van der Waals) constants for the homonuclear and the heteronuclear diatomic combinations of the atoms.

Derevianko, Andrei [Physics Department, Univ. of Nevada, Reno, NV 89557-0058 (United States)], E-mail: andrei@unr.edu; Porsev, Sergey G. [Physics Department, Univ. of Nevada, Reno, NV 89557-0058 (United States); Petersburg Nuclear Physics Institute, Gatchina, Leningrad District 188300 (Russian Federation)], E-mail: sporsev@gmail.com; Babb, James F. [ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138-1516 (United States)], E-mail: jbabb@cfa.harvard.edu

2010-05-15

262

Computational investigation of noble gas adsorption and separation by nanoporous materials.  

SciTech Connect

Molecular simulations are used to assess the ability of metal-organic framework (MOF) materials to store and separate noble gases. Specifically, grand canonical Monte Carlo simulation techniques are used to predict noble gas adsorption isotherms at room temperature. Experimental trends of noble gas inflation curves of a Zn-based material (IRMOF-1) are matched by the simulation results. The simulations also predict that IRMOF-1 selectively adsorbs Xe atoms in Xe/Kr and Xe/Ar mixtures at total feed gas pressures of 1 bar (14.7 psia) and 10 bar (147 psia). Finally, simulations of a copper-based MOF (Cu-BTC) predict this material's ability to selectively adsorb Xe and Kr atoms when present in trace amounts in atmospheric air samples. These preliminary results suggest that Cu-BTC may be an ideal candidate for the pre-concentration of noble gases from air samples. Additional simulations and experiments are needed to determine the saturation limit of Cu-BTC for xenon, and whether any krypton atoms would remain in the Cu-BTC pores upon saturation.

Allendorf, Mark D. (Sandia National Laboratories, Livermore, CA); Sanders, Joseph C.; Greathouse, Jeffery A.

2008-10-01

263

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

264

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

265

“Planetary” noble gas components and the nucleosynthetic history of solar system material  

Microsoft Academic Search

Models capable of explaining the differences between the isotopic compositions of the planetary noble gas components “Q” and “P3” (widespread in primitive meteorites) and average solar system material as sampled by the solar wind are presented, and their implications discussed.Small, variable amounts of known presolar components and 129Xe from 129I decay are present in Q gases alongside a solar composition

J. D. Gilmour

2010-01-01

266

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

Microsoft Academic Search

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. Allègre, Evidence for

Ratan K. Mohapatra; Masahiko Honda

2006-01-01

267

Dosimetry of noble-gas fission products  

Microsoft Academic Search

In the first minutes and hours following a reactor accident, personnel at the reactor facility, and possibly members of the public at off-site locations may be subjected to significant radiation dose from exposure to the entire spectrum of noble gas fission products and their daughter radionuclides. In order to measure the immersion dose of noble gas fission products following the

P. J. T

1989-01-01

268

Noble Gas Thermometry and Hydrologic Ages: Evidence for Late Holocene Warming in Southwest Texas  

NASA Astrophysics Data System (ADS)

Paleoclimatic reconstruction through the use of noble gases dissolved in groundwater has been the object of numerous studies in recent years. Unlike many other continental temperature proxies, noble gases have the advantage of providing direct information on atmospheric temperatures at the time rainwater penetrated the ground and joined a particular groundwater reservoir. In recent years, new methods for determination of noble gas temperatures have been developed, which provide a high level of accuracy on such temperature estimations. The issue of paleoclimatic reconstruction through noble gases however, is not only one of accurate temperature determination, but also one of accurate water age estimation so that a correct correspondence between noble gas temperatures and groundwater age can be established and proper paleoclimatic reconstruction attempted. The typical approach to estimate groundwater ages has been based on computing water travel times along streamlines from the recharge to the observation point taking into account only advection. This approach is limited because, like any other tracer, the movement of water in porous media is also affected by cinematic dispersion and molecular diffusion. We have therefore undertaken the formulation of hydrologic models that yield significantly better constraints on groundwater ages in the Carrizo aquifer and surrounding formations of south Texas, where noble gas temperatures have already been determined. To account for groundwater mixing we treat age as one would treat a solute concentration. In order to simulate groundwater ages we used a finite element model of groundwater flow that has been validated by 4He and 3He. The finite model spans a 120.6 Km cross-section between altitudes of +220m and -2210 m, and comprises 58,968 elements and 31,949 nodes. Combination of these newly calculated water ages and previously reported noble gas temperatures reveals new aspects of late Pleistocene and Holocene climate in southwestern Texas, in particular, an abrupt late Holocene temperature increase previously unidentified through 14C dating. Temperature increased by up to 3.4° C in the first half of the last millennium and by 1.5° C between ˜5.6 and 3.7 kyrs BP. More important than the resolution of individual paleoclimate episodes is the identification of a slow cooling trend between ˜1,200 kyrs and ˜200 kyrs, a trend that accelerates during the late Pleistocene and early Holocene. This cooling trend gives way to an extremely rapid increase in temperature in the late Holocene. Such abrupt warming seems to have accelerated in the last millennium and seems to continue at present. This temperature increase is the most striking feature arising from the determination of new groundwater ages.

Castro, M.; Goblet, P.

2003-12-01

269

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

270

Toxic gases.  

PubMed Central

An overview of the widespread use of gases and some volatile solvents in modern society is given. The usual circumstances in which undue exposure may occur are described. The most prominent symptoms and general principles of diagnosis and treatment are given and are followed by more specific information on the commoner, more toxic materials. While acute poisonings constitute the greater part of the paper, some indication of chronic disorders arising from repeated or prolonged exposure is also given.

Matthews, G.

1989-01-01

271

Positronium formation in positron-noble gas collisions  

NASA Astrophysics Data System (ADS)

Distorted-wave Born approximation calculations for Ps formation in positron impact on He, Ne, Ar, Kr and Xe are reported for the energy range up to 200 eV. Capture into the n=1, 2 and 3 states of Ps is calculated explicitly and 1/n3 scaling is used to estimate capture into states with n>3. The calculations for the heavier noble gases allow for capture not only from the outer np6 shell of the atom but also from the first inner ns2 shell. However, the inner shell capture is found to be very small. Although by no means unambiguous, the calculations provide some support to the conjecture of Larrichia et al. [J. Phys. B 35 (2002) 2525] that the double peak and shoulder structures observed experimentally for Ps formation in Ar, Kr and Xe arise from formation in excited states.

Gilmore, Sharon; Blackwood, Jennifer E.; Walters, H. R. J.

2004-07-01

272

Noble Foundation Plant Image Gallery  

NSDL National Science Digital Library

Provided by the Noble Foundation, a charitable foundation located in Ardmore, Oklahoma that focuses on agriculture and plant biology, this site contains images of over 600 vascular plants native primarily to the Oklahoma-Texas region. Offered as an educational tool for botanists, natural resource managers, and students, the site divides the images into three main categories: Grasses & grasslike plants; Forbs; and Trees, shrubs & woody vines. Within each, users can browse by common name, scientific name, or via a family or tribe index. Entries include a medium-sized image with some close-up thumbnails and information on species, family, longevity, season, origin, height, and flowers. A keyword/ natural language search engine that indexes the entire database is also available. Overall, this is a clean, fast-loading useful resource.

273

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

274

Imaging with SiPMs in noble-gas detectors  

NASA Astrophysics Data System (ADS)

Silicon photomultipliers (SiPMs) are photosensors widely used for imaging in a variety of high energy and nuclear physics experiments. In noble-gas detectors for double-beta decay and dark matter experiments, SiPMs are attractive photosensors for imaging. However they are insensitive to the VUV scintillation emitted by the noble gases (xenon and argon). This difficulty is overcome in the NEXT experiment by coating the SiPMs with tetraphenyl butadiene (TPB) to convert the VUV light into visible light. TPB requires stringent storage and operational conditions to prevent its degradation by environmental agents. The development of UV sensitive SiPMs is thus of utmost interest for experiments using electroluminescence of noble-gas detectors. It is in particular an important issue for a robust and background free ??0? experiment with xenon gas aimed by NEXT. The photon detection efficiency (PDE) of UV-enhanced SiPMs provided by Hamamatsu was determined for light in the range 250-500 nm. The PDE of standard SiPMs of the same model (S10362-33-50C), coated and non-coated with TPB, was also determined for comparison. In the UV range 250-350 nm, the PDE of the standard SiPM is shown to decrease strongly, down to about 3%. The UV-enhanced SiPM without window is shown to have the maximum PDE of 44% at 325 nm and 30% at 250 nm. The PDE of the UV-enhanced SiPM with silicon resin window has a similar trend in the UV range, although it is about 30% lower. The TPB-coated SiPM has shown to have about 6 times higher PDE than the non-coated SiPM in the range 250-315 nm. This is however below the performance of the UV-enhanced prototypes in the same wavelength range. Imaging in noble-gas detectors using UV-enhanced SiPMs is discussed.

Yahlali, N.; Fernandes, L. M. P.; González, K.; Garcia, A. N. C.; Soriano, A.

2013-01-01

275

Noble gas sputtering calculations using TRIM  

SciTech Connect

In conjunction with our experimental work on saddle field ion sputtering, we have attempted to apply the Monte Carlo program TRIM (Transport of Ions in Matter) to calculate the sputter yields for a variety of noble gas sputtering applications. Comparison with experiments are shown. Information extracted from these analyses have proved useful in optimizing the experimental sputtering parameters. Calculated sputter yields obtained utilizing TRIM are presented for noble gas sputtering of a variety of materials common to nuclear target production.

Greene, J.P.; Nemanich, J.; Thomas, G.E. [Argonne National Lab., IL (United States). Physics Div.; Schiel, S.L. [Illinois Univ., Urbana, IL (United States)

1996-12-31

276

Reservoir gases exhibit subtle differences; Part 4  

SciTech Connect

This segment of the reservoir fluids series describes the characteristics of wet and dry gases. At an initial producing gas-oil ratio greater than 15,000 scf/STB, engineers can treat the reservoir fluid as a wet gas. Gases with initial producing gas-oil ratios greater than 100,000 scf/STB can be treated as dry gases. Retrograde behavior has been observed in gases with initial producing gas-oil ratios greater than 150,000 scf/STB. The quantity of retrograde liquid in the reservoir is very small for gases this lean. If a gas has enough heavy components to release condensate at the surface, the gas will probably release some amount of condensate in the reservoir. This implies few true wet gases exist (liquid at the surface but no liquid in the reservoir).

McCain, W.D. Jr. (S.A. Holditch and Associates, College Station, TX (United States)); Piper, L.D. (Texas A M Univ., College Station, TX (United States))

1994-03-01

277

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

278

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

279

Noble gas and halogen constraints on regionally extensive mid-crustal Na–Ca metasomatism, the Proterozoic Eastern Mount Isa Block, Australia  

Microsoft Academic Search

Fluid inclusions in late-Isan quartz veins associated with regional Na–Ca alteration (albitisation), in the Mary Kathleen Fold Belt and the Cloncurry District of the Eastern Mt Isa Block, have been analysed for naturally occurring and neutron produced isotopes of Ar, Kr and Xe. The noble gases have been extracted using a thermal decrepitation procedure that enables partial deconvolution of the

M. A. Kendrick; T. Baker; B. Fu; D. Phillips; P. J. Williams

2008-01-01

280

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

281

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.

Füri, Evelyn; Aléon-Toppani, Alice; Marty, Bernard; Libourel, Guy; Zimmermann, Laurent

2013-09-01

282

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 strategies—from 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

283

Electronic transport through single noble gas atoms  

NASA Astrophysics Data System (ADS)

We present a theoretical study of the conductance of atomic junctions comprising single noble gas atoms (He, Ne, Ar, Kr, and Xe) coupled to gold electrodes. The aim is to elucidate how the presence of noble gas atoms affects the electronic transport through metallic atomic-size contacts. Our analysis, based on density functional theory and including van der Waals interactions, shows that for the lightest elements (He and Ne) no significant current flows through the noble gas atoms and their effect is to reduce the conductance of the junctions by screening the interaction between the gold electrodes. This explains the observations reported in metallic atomic-size contacts with adsorbed He atoms. Conversely, the heaviest atoms (Kr and Xe) increase the conductance because of the additional current path provided by their valence p states.

Zotti, L. A.; Bürkle, M.; Dappe, Y. J.; Pauly, F.; Cuevas, J. C.

2011-11-01

284

Solids Liquids and Gases  

NSDL National Science Digital Library

Compare and contrast the three states of matter: solids, liquids and gases. First you will begin by looking at characteristics of each solids, liquids and gasesGases, Liquids and Solids Facts. Then you will look at examples of each stateSolids, Liquids and Gases Video. Demonstrate an understanding of solids, liquids and gases by playing interactive gameSolids, Liquids and Gases Game. Graphic Organizer is here to be filled out as you learn during this lesson. Use the red ...

Salter, Ms.

2009-10-22

285

COMPRESSED MEDICAL GASES GUIDELINE  

Center for Biologics Evaluation and Research (CBER)

... COMPRESSED MEDICAL GASES GUIDELINE. (REVISED) FEBRUARY 1989. ... COMPRESSED MEDICAL GASES GUIDELINE. INTRODUCTION. ... More results from www.fda.gov/drugs/guidancecomplianceregulatoryinformation/guidances

286

High-index faceted noble metal nanocrystals.  

PubMed

The formation of novel and complex structures with specific morphologies from nanocrystals via a direct assembly of atoms or ions remains challenging. In recent years, researchers have focused their attention on nanocrystals of noble metals and their controlled synthesis, characterization, and potential applications. Although the synthesis of various noble metal nanocrystals with different morphologies has been reported, most studies are limited to low-index facet-terminated nanocrystals. High-index facets, denoted by a set of Miller indices {hkl} with at least one index greater than unity, possess a high density of low-coordinated atoms, steps, edges, and kinks within these structures and serve as more active catalytic sites. With the potential for enhanced catalytic performance, researchers have used the insights from shape-controlled nanocrystal synthesis to construct noble metal nanocrystals bounded with high-index facets. Since the report of Pt tetrahexahedral nanocrystals, researchers have achieved significant progress and have prepared nanocrystals with various high-index facets. Because of the general order of surface energy for noble metals, high-index facets typically vanish faster in a crystal growth stage and are difficult to preserve on the surface of the final nanocrystals. Therefore researchers have had limited opportunities to examine high-indexed noble metal nanocrystals with a controlled morphology and investigate their resultant behaviors in depth. In this Account, we thoroughly discuss the basic concepts and state-of-the-art morphology control of some noble metal nanocrystals enclosed with high-index facets. We briefly introduce high-index facets from both crystallographic and geometrical points of view, both of which serve as methods to classify these high-index facets. Then, we summarize various typical noble metal nanocrystals terminated by different types of high-index facets, including {hk0} (h > k > 0), {hhl} (h > l > 0), {hkk} (h > k > 0), and {hkl} (h > k > l > 0). In each type, we describe several distinct morphologies including convex, concave, and other irregular shapes in detail. Based on these remarks, we discuss key factors that may induce the variations of Miller indices in each class, such as organic capping ligands and metallic cationic species. In a look at applications, we review several typical high-indexed noble metal nanocrystals showing enhanced electrocatalytic or chemical catalytic activities. PMID:22587943

Quan, Zewei; Wang, Yuxuan; Fang, Jiye

2012-05-15

287

How Robust Is The Noble Gas Paleoclimate Proxy?  

Microsoft Academic Search

Noble gas temperatures (NGTs), which are derived from the air saturated water (ASW) component of noble gas concentrations (Ne, Ar, Kr, Xe) in groundwater, have long held the promise of providing a robust thermometer for use in paleoclimate reconstructions (Stute and Schlosser, 1993). In principle, groundwater noble gas concentrations are a simple function of temperature at the water table at

T. Sun; C. M. Hall; M. C. Castro

2008-01-01

288

Noble gas and carbon isotopic evidence for CO2-driven silicate dissolution in a recent natural CO2 field  

NASA Astrophysics Data System (ADS)

Secure storage of anthropogenic carbon dioxide (CO2) in geological reservoirs requires predicting gas-water-rock interactions over millennial timescales. Noble gases and carbon isotope measurements can be used to shed light on the nature of competing dissolution—precipitation processes over different timescales, from the fast dissolution of gaseous CO2 in groundwater to more sluggish reactions involving dissolution and precipitation of newly formed minerals in the reservoir. Here we study a compilation of gas analyses including noble gases and ?13C of CO2 from nine different natural CO2 reservoirs. Amongst these reservoirs, the Bravo Dome CO2 field (New Mexico, USA) shows distinct geochemical trends which are explained by degassing of noble gases from groundwater altering the composition of the gas phase. This groundwater degassing is synchronous with the dissolution of CO2 in groundwater. Progressive creation of alkalinity via CO2-promoted mineral dissolution is required to explain the observed positive correlation between CO2/3He and ?13C of the gas phase, a unique feature of Bravo Dome. The differences between Bravo Dome and other natural CO2 reservoirs are likely explained by the more recent filling of Bravo Dome, reflecting CO2-water-rock interactions over thousands of years rather than over millions of years in older reservoirs.

Dubacq, Benoît; Bickle, Mike J.; Wigley, Max; Kampman, Niko; Ballentine, Chris J.; Sherwood Lollar, Barbara

2012-08-01

289

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.

290

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

291

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

292

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.…

Walter, Tony

1995-01-01

293

Enhancing surface reactivity with a noble metal.  

PubMed

Gold, the archetypal noble metal, is usually associated with an inhibition of surface reactivity by site blocking. In this paper however, we show that on Cu(100) surfaces a gold adlayer can actually increase the extent of reaction with the substrate. PMID:23924973

Altass, Hatem; Carley, Albert F; Davies, Philip R; Davies, Robert J

2013-08-20

294

Sarkar on the Buddha's Four Noble Truths  

Microsoft Academic Search

:This is a critical comparison of two important figures, one ancient and one contemporary, in the Indian religious landscape: Gotama Buddha and Prabhat Ranjan Sarkar. Such comparison of their key ideas and practices is warranted for two reasons. First, Sarkar, a neo-Hindu thinker and reformer, has both praised the Buddha's humanism and criticized the Buddhist doctrine of the Four Noble

Chris Kang

2011-01-01

295

Electron-beam generation in a wide-aperture open gas discharge: A comparative study for different inert gases  

SciTech Connect

In the present study, electron-beam generation by open discharges was examined. The study was performed at gas pressures up to 20 Torr, and covered all inert gases. At voltages up to 8 kV, electron-beam currents up to 1600 A with current density {approx}130 A/cm{sup 2} and a beam generation efficiency in excess of 93% were obtained. The production of electrons from cold cathode was concluded to be of photoemissive nature, enabling the production of high-intensity electron beams in any noble gas or in a mixture of a noble gas with molecular gases irrespective of cathode material.

Bokhan, P. A.; Zakrevsky, Dm. E. [Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Prospekt Lavrent'eva 13, 630090 Novosibirsk (Russian Federation)

2010-08-30

296

Gravitational separation of gases and isotopes in polar ice caps  

Microsoft Academic Search

Atmospheric gases trapped in polar ice at the firn to ice transition layer are enriched in heavy isotopes (nitrogen-15 and oxygen-18) and in heavy gases (O2\\/N2 and Ar\\/N2 ratios) relative to the free atmosphere. The maximum enrichments observed follow patterns predicted for gravitational equilibrium at the base of the firn layer, as calculated from the depth to the transition layer

H. Craig; Y. Horibe; T. Sowers

1988-01-01

297

Void formation and closure under microgravity for different gases  

NASA Astrophysics Data System (ADS)

A self-consistent 2D dusty plasma fluid model used to model micro-gravity experiments in argon has been extended to allow the modeling of dusty plasmas in additional noble gases, including helium, krypton, neon, and xenon. The electron transport coefficients were obtained using BOLSIG+[1], whereas the ion transport coefficients were obtained from many literature sources, together with the thermal conductivity of the gases and the thermal accommodation coefficients. In this presentation we focus on the formation and closure of voids in microgravity experiments at different pressures and driving potentials, with the different noble gases. The goal is to provide a two-dimensional plot of the pressures and potentials at which 3D dust clouds under microgravity contain a dust-free void, or are void-free, for different carrier gases. This plot could serve as a road map for future experiments. [4pt] [1] G. J. M. Hagelaar and L. C. Pitchford, Plasma Sources Sci. Technol. 14 (2005) 722-733

Land, Victor; Bolser, Diana; Matthews, Lorin; Hyde, Truell

2009-11-01

298

New solvent purifies crude (and) coal acid gases  

Microsoft Academic Search

Allied Chemical Corp. has developed a new solvent process using the dimethyl ether of polyethylene glycol (called Selexol) for the selective absorption of sulfur gases and the bulk removal of acid gases in gasification plants fed with heavy crude oil or coal. The solvent has very different absorption characteristics for carbonyl sulfide, hydrogen sulfide, carbon dioxide, ammonia, and hydrocarbons. Commercial

Valentine

1974-01-01

299

Fast Plasma Shutdowns By Massive Hydrogen, Noble and Mixed-Gas Injection in DIII-D  

NASA Astrophysics Data System (ADS)

Experiments conducted with hydrogenic, noble and mixed (H2 + Ar and D2 + Ne) gases injected into H-mode plasmas are described. Gas species, quantity, delivery rate and intrinsic and added impurities (mixtures) all affect the disruption mitigation attributes of the resulting fast plasma shutdowns. With sufficient quantity, effective mitigation is obtained for all species. Optimal results for disruption and runaway avalanche mitigation are with 3x10^22 He delivery in ˜2 ms. This yields a favorable combination of moderately-fast current quench, high free-electron densities, ˜2x10^21,m-3, gas assimilation fractions ˜0.3 and avalanche suppression ratios, ne/nRB˜0.1. Favorable scaling of assimilation with increasing quantity is seen for all low-Z gases. The experiments provide validation data for emerging MHD/radiation simulation models and insight about design of injection systems for disruption and avalanche mitigation in ITER.

Wesley, J. C.; van Zeeland, M. A.; Evans, T. E.; Humphreys, D. A.; Hyatt, A. W.; Parks, P. B.; Strait, E. J.; Wu, W.; Hollmann, E. M.; Boedo, J. A.; Izzo, V. A.; James, A. N.; Moyer, R. A.; Rudakov, D. L.; Yu, J. H.; Jernigan, T. C.; Baylor, L. R.; Combs, S. K.; Groth, M.

2008-11-01

300

Phase transition of adsorbed noble gas on suspended graphene  

NASA Astrophysics Data System (ADS)

Suspended graphene sheets are simultaneously 2D nanomechanical resonators, hosts to massless Dirac electrons, and 2D substrates for adsorption. Adsorption is expected to modulate the mechanical and elctrical properties in a number of ways. We therefore aim to investigate the effects of equilibrium adsorbates on the vibrational resonances and on the conductance. Beginning with noble gases on non-suspended graphene exfoliated on SiO2, for argon we have seen a gradual change in the conductance as a function of vapor pressure at temperatures below the 2D critical point (54 K), indicating gradual formation of a monolayer over a wide chemical potential range (although we have also seen signs of a sharp monolayer phase transition in a least one sample). The mechanism of conductance modulation is a topic of interest. The large broadening of the expected 2D vapor-liquid step is likely to be due to inhomogeneous binding caused by charge disorder, roughness, and other properties of the SiO2 substrate. We are developing pristine suspended graphene devices to eliminate these complications.

Fei, Zaiyao; Lee, Hao-Chun; Dzyubenko, Boris; Wu, Sanfeng; Cobden, David

2013-03-01

301

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

302

Noble gas-derived insights into carbon cycling into the deep biosphere  

NASA Astrophysics Data System (ADS)

Discovery of chemoautotrophic microbial communities at the mid-ocean ridges launched the exploration of the "deep hot biosphere". Recent advances have demonstrated however that chemoautotrophic communities are not restricted to high temperature hydrothermal settings. The discovery that the terrestrial subsurface too hosts chemoautotrophic ecosystems sustained by the products of water-rock reactions - albeit at lower temperatures and slower rates of reaction - has expanded our view of the extent of the planet that is habitable. Compelling questions remain. What are the ultimate limits to life in the Earth's deep subsurface? What are the underlying controls on microbial metabolic activity and biodiversity? The answers to these questions may provide insight into the evolutionary relationship of deep terrestrial microbial communities to marine sediment-hosted and vent-hosted communities, into the origin of life on Earth, and the potential for life on other planets and moons. At more than 2 km below surface, fracture waters accessed via mines in the tectonically quiescent Precambrian Shields of Canada and South Africa are dominated by radiogenic noble gases and crustal-derived carbon sources. Key uncertainties concerning the deep terrestrial biosphere in these settings include the rates and mechanisms of carbon cycling far from the photosphere, and hence the scale and significance of this remote and exotic reservoir of the global biogeochemical cycle. While carbon geochemistry and stable isotopes, as well as molecular microbiology, have facilitated major advances in identifying the geochemical and microbiological processes involved, this presentation will highlight how coupling these techniques with noble gases constrains the timescales for the deep carbon cycle. In particular, the coupling of noble gas tracers with carbon geochemistry provides the key to recognizing that hydrogeologically isolated fracture networks of geochemically distinct groundwaters exert a major control on the distribution and nature of microbial life and metabolic function in the deep surface. Understanding the nature and distribution of fluids in the subsurface is critical to deciphering the environmental constraints and potential for deep life. Noble gases provide a unique insight into both the sourcing of different components of these fluid-dominated systems and the residence times and timescales of fluid mixing and interaction and hence provide a powerful but to date still underutilized resource for deep biosphere research.

Sherwood Lollar, B.; Ballentine, C. J.; Lippmann-Pipke, J.; Slater, G. F.; Onstott, T. C.; Lin, L.; Moran, J.; Tille, S.; Moser, D. P.; Lacrampe-Couloume, G.

2009-12-01

303

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

304

Highly Fluorescent Noble-Metal Quantum Dots  

NASA Astrophysics Data System (ADS)

Highly fluorescent, water-soluble, few-atom noble-metal quantum dots have been created that behave as multielectron artificial atoms with discrete, size-tunable electronic transitions throughout the visible and near infrared. These molecular metals exhibit highly polarizable transitions and scale in size according to the simple relation EFermi/N1/3, predicted by the free-electron model of metallic behavior. This simple scaling indicates that fluorescence arises from intraband transitions of free electrons, and these conduction-electron transitions are the low-number limit of the plasmon—the collective dipole oscillations occurring when a continuous density of states is reached. Providing the missing link between atomic and nanoparticle behavior in noble metals, these emissive, water-soluble Au nanoclusters open new opportunities for biological labels, energy-transfer pairs, and light-emitting sources in nanoscale optoelectronics.

Zheng, Jie; Nicovich, Philip R.; Dickson, Robert M.

2007-05-01

305

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 environments—a 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

2012-08-01

306

Solids, Liquids, and Gases  

NSDL National Science Digital Library

Objective: Students will be introduced to solids, liquids, and gases. Students will identify key characteristics of the three states of matter. Everything is made of matter. Matter is made of atoms. Matter makes up solids, liquids, and gases. What are some similarities and differences between solids, liquids, and gases? Follow the link below to find out. Characteristics of the States of Matter The previous website gave some general characteristics for solids, liquids, and gases. Now ...

Rohlfing, Mrs.

2010-10-22

307

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

308

Actinide(lanthanide)-noble metal alloy phases, preparation and properties  

Microsoft Academic Search

Actinide (A--Th-Cm)-noble metal phases with platinum, palladium, rhodium, and iridium (--B)- and lanthanide-noble metal phases with platinum and palladium have been prepared by reduction of corresponding oxides or fluorides in the presence of noble metals by extremely purified hydrogen. Alloy phases of composition AB2, AB3, and\\/or AB5 have been identified, most of which crystallize in the Cu2Mg, Cu3Au, Ni3Ti, Cd3Mg,

B. Erdmann; C. Keller

1973-01-01

309

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

310

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, Peña 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, Peña 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, Peña 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, Peña 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

311

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

SciTech Connect

Previous work showed that the {sup 3}He(n,tp) reaction in a cell of {sup 3}He 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.; Thompson, Alan K.; Vest, Robert E. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Coplan, Michael A. [Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Clark, Charles W. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, Gaithersburg, Maryland 20899 (United States)

2010-12-06

312

Bonding of Multiple Noble-Gas Atoms to CUO in Solid Neon: CUO(Ng)(n) (Ng= Ar, Kr, Xe; n= 1, 2, 3, 4) Complexes and the Singlet-Triplet Crossover Point  

Microsoft Academic Search

Laser-ablated U atoms codeposited with CO in excess neon produce the novel CUO molecule, which forms distinct Ng complexes (Ng= Ar, Kr, Xe) with the heavier noble gases. The CUO(Ng) complexes are identified through CO isotopic and Ng reagent substitution and comparison to results of DFT frequency calculations.

Binyong Liang; Lester S. Andrews; Jun Li; Bruce E. Bursten

2003-01-01

313

On the Noble-Gas Induced Intersystem Crossing for the CUO Molecule: Experimental and Theoretical investigations of CUO(Ng)n (Ng = Ar, Kr, Xe; n = 1, 2, 3, 4) Complexes in Solid Neon  

Microsoft Academic Search

Uranium atoms excited by laser ablation react with CO in excess neon to produce the novel CUO molecule, which forms distinct Ng complexes (Ng = Ar, Kr, Xe) when the heavier noble gases are added. The CUO(Ng) complexes are identified through CO isotopic and Ng substitution on the neon matrix infrared spectra and by comparison to DFT frequency calculations. The

Binyong Liang; Lester S. Andrews; Jun Li; Bruce E. Bursten

2004-01-01

314

Ultrapure Gases - From the Production Plant to the Laboratory  

SciTech Connect

Radioactive noble gas isotopes are a potential source of background in low-level physics experiments, since they are present in the atmosphere and also in widely used gases produced from the atmosphere. We have studied the 39Ar, 85Kr and 222Rn contamination of commercially available nitrogen using low background proportional counters and a rare gas mass spectrometer. It was found that air separation plants are very effective in removing traces of radioactive noble gases and that the available purity can be significantly higher than commercial specifications. On the other hand the gas handling processes which are necessary to deliver gases from the production plant to the customer are a possible source of re-contaminations and determine in most cases the achievable purity. By simulating these processes under realistic conditions we have establish together with the Italian company 'SOL group' a well controlled delivery path which can hold the purity. For the short-lived 222Rn the initial contamination is less critical, because it decays away. Instead the emanation rate of the cryogenic tank was found to determine the achievable purity, since it permanently delivers new 222Rn.

Simgen, H.; Zuzel, G. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

2007-03-28

315

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

316

Identifying Recharge Location Using Noble Gas Recharge Temperatures, Pajarito Plateau, New Mexico  

NASA Astrophysics Data System (ADS)

The solubility of noble gases in water is temperature dependent. Noble gas concentrations in ground water can therefore be used to determine the temperature at the water table at the recharge location (recharge temperature). The Pajarito Plateau in Northern New Mexico is an example of a hydrogeologic setting where noble gas recharge temperatures provide valuable information about recharge location which could be utilized in numerical model calibration. Previous studies have identified two potentially significant components of recharge to the regional aquifer underlying the plateau: (1) infiltration of precipitation in the Jemez Mountains adjacent to the plateau (mountain-block recharge); and (2) infiltration of stream water in the bottoms of canyons that traverse the plateau (plateau recharge). However, results regarding the relative importance of these two components are conflicting and uncertain. Their relative magnitude is of particular concern because Los Alamos National Laboratory is located on the plateau, and the susceptibility of the regional aquifer to lab-generated wastes depends directly upon the amount of plateau recharge. The Pajarito Plateau is an ideal location for applying noble gas recharge thermometry; mountain-block recharge should have cool recharge temperatures (<12°C) due to the shallow water table in the mountains, whereas plateau recharge should have distinctly warmer recharge temperatures (18 to 21°C) due to water table depths of 200 to 300m on the plateau. Noble gas samples were collected from wells screened in the regional aquifer across the plateau. Those analyzed to date from wells screened in the upper 30m of the aquifer yield recharge temperatures of 18 to 23°C. Exceptions are two wells located within 2km of the mountain front, which have recharge temperatures of 12 and 13°C. The one sample analyzed to date from a well screened deeper in the aquifer (125m below the water table) yields a recharge temperature of 11°C. Preliminary results therefore suggest that plateau recharge comprises nearly all of the water in the upper 30m of the regional aquifer throughout much of the plateau. However, the cooler recharge temperatures closer to the mountains and at depth indicate that mountain-block recharge may still constitute most of the total recharge to the aquifer; plateau recharge may be limited to a thin layer along the top of the aquifer at distances >2km from the mountain front.

Manning, A. H.; Dale, M.

2008-12-01

317

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 13–23°S 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 20.7°S

Samuel Niedermann; Wolfgang Bach; Jörg Erzinger

1997-01-01

318

Vertically Aligned ZnO Nanorod Arrays Coated with $\\\\hbox{SnO}_{\\\\bf 2}$\\/Noble Metal Nanoparticles for Highly Sensitive and Selective Gas Detection  

Microsoft Academic Search

Mimicking the biological olfactory receptor array that possesses large surface area for molecule capture, vertically aligned ZnO nanowire arrays, used as structural templates, were coated with SnO2 \\/noble metal nanoparticles as active materials for fabrication of 3-D gas sensors. The gas sensors showed room- temperature responses to environmental toxic gases, such as NO2 and H2 S, down to ppb level,

Jiajun Chen; Kai Wang; Weilie Zhou

2011-01-01

319

Fractionation of the noble metals by physical processes  

Microsoft Academic Search

During partial melting in the earth’s mantle, the noble metals become fractionated. Os, Ir, Ru, and Rh tend to remain in the mantle residue whereas Pt, Pd, and Re behave mildly incompatible and are sequestered to the silicate melt. There is consensus that sulfide plays a role in the fractionation process; the major noble metal repository in the mantle is

Chris Ballhaus; Conny Bockrath; Cora Wohlgemuth-Ueberwasser; Vera Laurenz; Jasper Berndt

2006-01-01

320

USE OF SIX SIGMA TOOLS TO REDUCE NOBLE METAL LOSSES  

Microsoft Academic Search

The objective of this work is to utilize Sixx Sigma as the methodology to optimize the chemical process in a Chemical Company. The process involves an effective use of the noble metal based catalyst in a CSTR reactor; however, noble metal losses resulted in the nature of the process has impacted on the cost of the final product. The actual

P. C. Brito; J. F. Morais; Monsanto Nordeste

321

Noble gas trapping and fractionation during synthesis of carbonaceous matter  

Microsoft Academic Search

An investigation of noble gas entrapment during synthesis of carbonaceous, macromolecular, and kerogen-like substances is presented. High molecular weight organic matter synthesized in aqueous condensation reactions contained little gas, and the composition was consistent with fractionation due to noble gas solubility in water; however, propane soot produced during a modified Miller-Urey experiment in an aritificial gas mixture contained high concentrations

U. Frick; R. Mack; S. Chang

1979-01-01

322

Synthesis and characterization of a binary noble metal nitride  

Microsoft Academic Search

There has been considerable interest in the synthesis of new nitrides because of their technological and fundamental importance. Although numerous metals react with nitrogen there are no known binary nitrides of the noble metals. We report the discovery and characterization of platinum nitride (PtN), the first binary nitride of the noble metals group. This compound can be formed above 45-50

Eugene Gregoryanz; Chrystele Sanloup; M. Somayazulu; James Badro; Guillaume Fiquet; Ho-Kwang Mao; Russell J. Hemley

2004-01-01

323

21 CFR 872.3060 - Noble metal alloy.  

Code of Federal Regulations, 2013 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...

2013-04-01

324

Negative muon capture in noble gas mixtures  

NASA Astrophysics Data System (ADS)

We have determined the probabilities of atomic negative muon capture in binary mixtures of the gases He, Ne, Ar, and Kr at partial pressures near five atmospheres. Relative capture rates were deduced from measured muonic X-ray yields.

Hutson, R. L.; Knight, J. D.; Leon, M.; Schillaci, M. E.; Knowles, H. B.; Reidy, J. J.

1980-03-01

325

Potential energy curves for the interaction of Ag(5s) and Ag(5p) with noble gas atoms.  

PubMed

We investigate the interaction of ground and excited states of a silver atom with noble gases (NG), including helium. Born-Oppenheimer potential energy curves are calculated with quantum chemistry methods and spin-orbit effects in the excited states are included by assuming a spin-orbit splitting independent of the internuclear distance. We compare our results with experimentally available spectroscopic data, as well as with previous calculations. Because of strong spin-orbit interactions, excited Ag-NG potential energy curves cannot be fitted to Morse-like potentials. We find that the labeling of the observed vibrational levels has to be shifted by one unit. PMID:23464145

Loreau, J; Sadeghpour, H R; Dalgarno, A

2013-02-28

326

Heavy Gas Releases: Recent Dispersion Research.  

National Technical Information Service (NTIS)

The important liquefied fuels which form heavy gases are liquefied natural gas (LNG) (comprised chiefly of methane, but with small amounts of propane and ethane), and liquefied petroleum gas (LPG), (comprised of propane and butane in various ratios). In a...

J. H. Shinn D. L. Ermak R. P. Koopman

1981-01-01

327

Mass and temperature-dependent diffusion coefficients for lightnoble gases for the TOUGH2-EOSN Model  

Microsoft Academic Search

This report describes modifications made to the EOSN module(Shan and Pruess, 2003) of the nonisothermal multiphase flow simulatorTOUGH2 (Pruess, et al., 1999). The EOSN fluid property module simulatestransport of water, brine, air, and noble gases or CO2 in the subsurface.In the standard version of the EOSN module, diffusion coefficients can bespecified by the user, but there is no allowance for

J. L. Andrews; S. Finsterle; M. O. Saar

2007-01-01

328

Breakdown of Gases Below Paschen Minimum: Basic Design Data of High-Voltage Equipment  

Microsoft Academic Search

For the region pd<(pd)min, breakdown characteristics U2 = f(pd) are presented for both the noble and the more important molecular gases He, Ne, A, Kr, Xe, N2, H2, NH3, air, CO2, O2 (and Hg), particularly giving the probability of breakdown on which they are based, so that they can be used for dimensioning the relevant equipment. The design of vessel

MAX J. SCHONHUBER

1969-01-01

329

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...

330

Noble gas and isotope geochemistry in western Canadian Arctic watersheds: tracing groundwater recharge in permafrost terrain  

NASA Astrophysics Data System (ADS)

In Canada's western Arctic, perennial discharge from permafrost watersheds is the surface manifestation of active groundwater flow systems with features including the occurrence of year-round open water and the formation of icings, yet understanding the mechanisms of groundwater recharge and flow in periglacial environments remains enigmatic. Stable isotopes (?18O, ?D, ?13CDIC), and noble gases have proved useful to study groundwater recharge and flow of groundwater which discharges along rivers in Canada's western Arctic. In these studies of six catchments, groundwater recharge was determined to be a mix of snowmelt and precipitation. All systems investigated show that groundwater has recharged through organic soils with elevated PCO2, which suggests that recharge occurs largely during summer when biological activity is high. Noble gas concentrations show that the recharge temperature was between 0 and 5 °C, which when considered in the context of discharge temperatures, suggests that there is no significant imbalance of energy flux into the subsurface. Groundwater circulation times were found to be up to 31 years for non-thermal waters using the 3 H-3He method.

Utting, Nicholas; Lauriol, Bernard; Mochnacz, Neil; Aeschbach-Hertig, Werner; Clark, Ian

2013-02-01

331

Dating very old pore waters in impermeable rocks by noble gas isotopes  

NASA Astrophysics Data System (ADS)

The 4He, 40Ar, and 136Xe 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, we 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 informations of groundwater and pore water have been derived. We find palaeowaters from the last glaciation depleted in ?D and ? 18O with a 4He 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 4He and 40Ar close to diffusion in steady-state and from xenon isotopes produced by spontaneous fission of 238U in the rocks. A 4He flux of 2 · 10 -7 cc STP cm -2 yr -1 is derived from the profile, which is due to local 4He production within the investigated sediments.

Osenbrück, Karsten; Lippmann, Johanna; Sonntag, Christian

1998-09-01

332

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

1998-09-01

333

Laser microprobe analyses of noble gas isotopes and halogens in fluid inclusions: Analyses of microstandards and synthetic inclusions in quartz  

SciTech Connect

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{sup {minus} 11} liter 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.

Boehlke, J.K. (Geological Survey, Reston, VA (United States)); Irwin, J.J. (Univ. of California, Berkeley (United States))

1992-01-01

334

Heavy gas releases: recent dispersion research  

Microsoft Academic Search

The important liquefied fuels which form heavy gases are liquefied natural gas (LNG) (comprised chiefly of methane, but with small amounts of propane and ethane), and liquefied petroleum gas (LPG), (comprised of propane and butane in various ratios). In addition to other fuels with these properties, there are a variety of industrial gases transported in pressurized vessels, such as hydrocarbons

J. H. Shinn; D. L. Ermak; R. P. Koopman

1981-01-01

335

Muon spin depolarization in noble gases during slowing down in a longitudinal magnetic field  

NASA Astrophysics Data System (ADS)

The spin depolarization of the positive muon during slowing down in He, Ne and Ar has been calculated as a function of gas pressure and longitudinal magnetic field strength. The calculation is based on the cross sections for the atomic processes contributing to the slowing down of the positive muon 0953-4075/31/23/020/img1 and muonium 0953-4075/31/23/020/img2, obtained from the corresponding cross sections for the proton 0953-4075/31/23/020/img3 and hydrogen 0953-4075/31/23/020/img4 by simple scaling schemes. The depolarization mechanism taking place in the subpicosecond time regime is discussed in the context of recent experiments to determine the muon decay parameters precisely and accurately in the search for right-handed neutrinos. It has been shown that the polarization loss in He is 1% at 0953-4075/31/23/020/img5 and 1 atm pressure, an amount which is unacceptably large for accurate (100 ppm or better) measurements of the muon decay parameters. It is also pointed out that at this level of accuracy a strong longitudinal magnetic field is a much less effective means of quenching the muon spin depolarization mechanism than previously thought. Effects of the electron spin polarization induced by a strong longitudinal magnetic field are also discussed.

Senba, Masayoshi

1998-12-01

336

Total scattering cross sections and interatomic potentials for neutral hydrogen and helium on some noble gases  

SciTech Connect

Measurements of energy-dependent scattering cross sections for 30 to 1800 eV D incident on He, Ne, Ar, and Kr, and for 40 to 850 eV He incident on He, Ar, and Kr are presented. They are determined by using the charge-exchange efflux from the Princeton Large Torus tokamak as a source of D or He. These neutrals are passed through a gas-filled scattering cell and detected by a time-of-flight spectrometer. The cross section for scattering greater than the effective angle of the apparatus (approx. =20 mrad) is found by measuring the energy-dependent attenuation of D or He as a function of pressure in the scattering cell. The interatomic potential is extracted from the data.

Ruzic, D.N.; Cohen, S.A.

1985-04-01

337

Contribution to the theory of non-self-maintaining volume discharges in molecular and noble gases  

Microsoft Academic Search

Results are presented of investigations of non-self-maintaining volume (NV) gas discharges. The structure is investigated and the current-voltage characteristics are plotted of NV discharges in molecular gas. The characteristic times of the transient processes in the cathode layer of a nonstationary electron-beam-controlled (EBC) discharge are obtained. It is proposed to use an NV discharge as the nonlinear element of a

V. V. Aleksandrov; E. P. Glotov; V. A. Danilychev; V. N. Koterov; A. M. Soroka

1984-01-01

338

Relation of Electron Scattering Cross-Sections to Drift Measurements in Noble Gases  

Microsoft Academic Search

I investigate the classic ``inverse problem'' of extracting collision and scattering cross sections from measurements of electron swarm behavior. A Monte Carlo technique for simulating electron motion through a gas of isotropic scatterers is presented, providing a simplified version of Biagi's MAGBOLTZ algorithm. Using this Monte Carlo software, I examine the thermalization of electron swarms, focusing on their drift velocity

Blake Stacey

2005-01-01

339

Impact Event at the Permian-Triassic Boundary: Evidence from Extraterrestrial Noble Gases in Fullerenes  

Microsoft Academic Search

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

Luann Becker; Robert J. Poreda; Andrew G. Hunt; Theodore E. Bunch; Michael Rampino

2001-01-01

340

Variable flip angle schedules in bSSFP imaging of hyperpolarized noble gases.  

PubMed

Balanced steady-state free precession imaging sequences provide signal-to-noise ratio benefits for MRI of hyperpolarized nuclei. Hyperpolarized magnetization decays during the imaging sequence to thermal equilibrium, effectively necessitating imaging in a transient state characterized by nonconstant transverse magnetization and k-space filtering when using constant flip angles. This work presents an analytical method for calculation of variable flip angle schedules which maintain constant transverse magnetization in balanced steady-state free precession imaging of hyperpolarized nuclei. The approach is based on direct inversion of the Bloch equations and does not require any numerical optimization. Input parameters are pulse sequence timings and effective relaxation times, which take diffusion of hyperpolarized gas in imaging gradients into account. Provision of constant transverse magnetization is demonstrated in phantom experiments and human lung imaging using hyperpolarized (3) He. The benefit of a flat k-space filter is demonstrated by reduced blurring in (3) He and digital phantom data, and high quality (3) He ventilation images from human lungs are obtained. PMID:22134846

Deppe, Martin H; Wild, Jim M

2011-08-29

341

Regularities and irregularities of the Stark broadening parameters for singly ionized noble gases  

NASA Astrophysics Data System (ADS)

In the last years, different trends and regularities of Stark broadening parameters (halfwidths and shifts of spectral lines) have been analyzed. Conditions related to atomic structure of the element, as well as plasma conditions are responsible for regular or irregular behavior of the Stark broadening parameters . The absence of very close perturbing levels makes Ne II a good candidate for the analysis of the Stark broadening parameters regularities. The other two elements considered in this work, Kr II and Xe II, have complex spectra and present strong perturbations, leading to the appearance of Stark broadening parameters irregularities in some cases. In this work, we analyze the influence of perturbations on Stark broadening parameters within the multiplets.

Peláez, R. J.; Djurovi?, S.; ?irišan, M.; Aparicio, J. A.; Mar, S.

2010-11-01

342

Noble gases in individual L chondritic micrometeorites preserved in an Ordovician limestone  

NASA Astrophysics Data System (ADS)

We have measured the He and Ne concentrations and isotopic ratios of individual sediment-dispersed extraterrestrial chromite grains (63-180 ?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 ˜ 470 Ma ago. In this analysis of 37 individual extraterrestrial chromite grains of L chondritic major element composition, at least 35 (˜ 95%) contain surface-implanted helium and neon of fractionated solar wind composition, implying that these grains are (relict parts of) fossil micrometeorites of asteroidal origin. Similar to what has been observed in recent micrometeorites collected in the polar regions, significant amounts of cosmogenic 21Ne were found in several grains, resulting in cosmic ray exposure (CRE) ages of up to ˜ 77 Myr. These ages exceed both dynamical lifetimes for asteroidal micrometeorites of this size as well as CRE ages observed in chromites from fossil meteorites from the same sediment beds. Significant contributions from terrestrial sources, like nucleogenic and cosmic-ray muon induced 21Ne can be excluded in the extraterrestrial chromites, since 11 terrestrial chrome spinel grains from the same sediment beds did not contain any measurable 21Ne excesses. Having found micrometeorites of undisputed asteroidal origin with cosmic ray exposure ages of several 10 7 years implies that high cosmic ray exposure ages alone are not a good indicator of cometary origin, in opposition to what has been suggested for recent micrometeorites and IDPs. We propose instead that these grains collected their cosmogenic 21Ne while residing in the regolith layer of their parent body.

Meier, M. M. M.; Schmitz, B.; Baur, H.; Wieler, R.

2010-02-01

343

A generic biokinetic model for noble gases with application to radon  

SciTech Connect

The International Commission for Radiological Protection (ICRP) currently uses a dose conversion coefficient to calculate effective dose per unit exposure to radon and its progeny. The coefficient is derived by dividing the detriment associated with unit exposure to radon, as estimated from epidemiological studies, by the detriment per unit effective dose, as estimated mainly from atomic bomb survivor data and animal studies. In a recent statement the ICRP indicated that future guidance on exposure to radon and its progeny will be developed in the same way as guidance for any other radionuclide. That is, intake of radon and progeny will be limited on the basis of effective dose coefficients derived from biokinetic and dosimetric models. This paper proposes a biokinetic model for systemic (absorbed) radon for use in the calculation of dose coefficients for inhaled or ingested radon. The model is based largely on physical laws governing transfer of a non-reactive and soluble gas between materials. Model predictions are shown to be consistent with results of controlled studies of the fate of internally deposited radon in human subjects.

Leggett, Richard Wayne [ORNL; Marsh, James [Health Protection Agency of Great Britain; Gregoratto, Demetrio [Health Protection Agency of Great Britain; Blanchardon, Eric [IRSN

2013-01-01

344

Crustal Noble Gases in Jwaneng Diamonds With Links to Seismic Tomography  

Microsoft Academic Search

Recent seismic tomography studies of the Kaapvaal-Zimbabwe craton of southern Africa reveal distinct seismic velocity profiles at 150 km depth within the diamond stability field, that appear to correlate with differences in diamond paragenesis. Diamond mines with predominantly eclogitic diamond inclusions (e.g. Jwaneng, Orapa, Premier) overlie lithospheric mantle with relatively slow P-wave velocities, whereas localities with predominantly peridotitic diamond inclusions

M. Honda; D. Phillips; J. W. Harris; I. Yatsevich

2005-01-01

345

Carbon and Noble Gases in Sutter"s Mill: Relationship to CM Chondrites  

NASA Astrophysics Data System (ADS)

Sutter"s Mill fell in California in April 2012. Because of its fresh state, we are interested in the light element history of this meteorite, for comparison with other carbonaceous chondrites, particularly CM chondrites and the unusual Tagish Lake.

Grady, M. M.; Verchovsky, A. B.; Gilmour, I.; Yin, Q.-Z.

2012-09-01

346

A study of autoionizing resonances in noble gases using (e, 2e) spectroscopy  

NASA Astrophysics Data System (ADS)

A coplanar, asymmetric (e, 2e) spectrometer has been rebuilt and used to carry out measurements on atomic xenon. We have performed the first (e, 2e) measurements of the energy region containing the 5p5( 2P1/2)nd' , ms' Rydberg series of autoionizing resonances. The low ejected electron energies in this region (E < 1.3 eV) present a problem for conventional electrostatic spectrometers such as ours; however, we have developed and tested techniques that allow us to obtain accurate spectra at energies as low as E ? 0.2 eV. In each measurement, we simultaneously collect energy spectra at ejected electron angles 180° apart. The summation of these spectra eliminates differences clue to interference terms involving opposite-parity multipoles leaving a mostly dipole spectrum, while the difference between these spectra isolates these interference terms. In an (e, 2e) simulation of photo-electron spectroscopy, we have measured the photoabsorption spectrum and the beta-parameter spectrum using a relatively low incident energy of 1.50 eV. The results are in fair agreement with actual photoelectron measurements. We have pleasured the interference between opposite-parity multipole processes at an incident energy of 150 eV and low momentum transfer kinematics. Using a simple analysis, we have extracted information on the relative phases of the ionization amplitudes. We have also measured a series of ( e, 2e) spectra with increasing values of momentum transfer of magnitude K ˜ 0.2--0.6 a.u. at 150 eV incident energy and ejected electron angles parallel and antiparallel to the momentum transfer axis. We find in all these measurements that the intensity of the Binary peak is less than that of the Recoil peak. This is in contrast to the previous measurements on cadmium using the same kinematics in which it was found that the intensity of the Binary peak was greater than that of the Recoil peak.

Childers, James Gregory

347

Electron impact ionization and dielectric breakdown in the liquid noble gases: a Monte Carlo simulation  

Microsoft Academic Search

Determining whether electron avalanches can occur in the liquid phase is of fundamental importance when formulating models for electrical breakdown in liquids. The electron energy distribution function, drift velocity, and ionization rate for electrons in liquid xenon have been calculated using a kinetic model for electron transport. The electron scattering rates have been obtained using the Van Hove approach in

H. M. Jones; E. E. Kunhardt

1996-01-01

348

Submicron defects in rapidly solidified Type 304 stainless steel powders containing noble gases  

SciTech Connect

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 of the melt with argon. The entrapped argon in the melt, as well as the carrier argon associated with the melt stream, produces the molten droplets. Optical microscopy was performed on screened particle sizes to resolve the morphological features such as porosity and solidification microstructure.

Bae, J.C.; Kelly, T.F.; Flinn, J.E.; Wright, R.N.

1988-05-01

349

Mass fractionation of noble gases in diffusion-limited hydrodynamic hydrogen escape  

SciTech Connect

The theory of mass fractionation by hydrogen is presently extended to atmospheres in which hydrogen is not the major constituent. This theoretical framework is applied to three different cases. In the first, it is shown that the fractionation of terrestrial atmospheric neon with respect to mantle neon is explainable as a consequence of diffusion-limited hydrogen escape from a steam atmosphere toward the end of the accretion process. In the second, the anomalously high Ar-38/Ar-36 ratio of Mars is shown to be due to hydrodynamic fractionation by a vigorously escaping and very pure hydrogen wind. In the last case, it is speculated that the currently high Martian D/H ratio emerged during the hydrodynamic escape phase which fractionated Ar. 35 refs.

Zahnle, K.; Pollack, J.B.; Kasting, J.F. (NASA, Ames Research Center, Moffett Field, CA (USA) Pennsylvania State Univ., University Park (USA))

1990-04-01

350

Production of noble gases near the surface of Europa and the prospects for in situ chronology  

Microsoft Academic Search

The age of the surface of Europa is probably tens of Myr or less, but is poorly constrained. Two different geochronology schemes could potentially be applied to near-surface samples to provide far more precise ages. First, the surface salts apparently contain enough potassium to make potassium–argon dating feasible. Second, the bombardment of the surface with both galactic cosmic rays and

T. D. Swindle; J. Masarik; D. Kollárb; K. J. Kimc; R. C. Reedy

2005-01-01

351

Excitation of autoionization states of the atoms of noble gases by fast electrons: argon  

Microsoft Academic Search

The ionization of Ar atoms by electron impact in the neighborhood of a (3s)⁻¹(4p)¹P autoionization state is considered theoretically. Resonance profiles are calculated for the spectra of scattered electrons and of electrons under the conditions of a (e, 2e) coincidence experiment. The calculation is carried out in the Born approximation using a Herman-Skillman model and a Hartree-Fock model with a

V. V. Balashov; A. N. Grum-Grzhimailo; N. M. Kabachnik; A. I. Magunov; S. I. Strakhova

1980-01-01

352

Excitation of autoionization states of the atoms of noble gases by fast electrons: argon  

SciTech Connect

The ionization of Ar atoms by electron impact in the neighborhood of a (3s)/sup -1/(4p)/sup 1/P autoionization state is considered theoretically. Resonance profiles are calculated for the spectra of scattered electrons and of electrons under the conditions of a (e, 2e) coincidence experiment. The calculation is carried out in the Born approximation using a Herman-Skillman model and a Hartree-Fock model with a frozen core. The sensitivity of the resonance profile to the type of electron wave functions in the continuous spectrum is analyzed. The resemblance and difference in the characteristic peculiarities are discussed in the process of excitation of partially hole autoionization states in the Ar and Ne atoms.

Balashov, V.V.; Grum-Grzhimailo, A.N.; Kabachnik, N.M.; Magunov, A.I.; Strakhova, S.I.

1980-12-01

353

Tracing partial melting and subduction-related metasomatism in the Kamchatkan mantle wedge using noble gas compositions  

NASA Astrophysics Data System (ADS)

We determined noble gas composition of minerals separated from mantle-derived xenoliths hosted by andesites in the active Avacha volcano, Kamchatka peninsula, Russia in order to better constrain the provenance and nature of fluids involved in partial melting and metasomatism in the mantle wedge. The lithospheric mantle beneath Avacha mainly consists of spinel harzburgites produced by high degrees of melt extraction. Data on coarse olivine separated from seven harzburgite xenoliths constrain fluid regime during flux melting in arc settings. Pyroxenes from two websterite veins cross-cutting the harzburgites characterize post-melting metasomatism by subduction-related melts or fluids. 3He/ 4He-ratios of 5.2 ± 0.6 to 8.1 ± 0.3 R A obtained on both olivines and pyroxenes overlap the highest values reported for volcanic rocks from Kamchatka and fall into the typical range of continental lithospheric mantle worldwide. This rules out significant contributions of slab-derived radiogenic 4He*. The highest 40Ar/ 36Ar ratios are 400; Ne and Xe isotope ratios are indistinguishable from those in the air. We consider the slab as the initial source of a major portion of these 'atmospheric' gases. Element composition of noble gases in olivine differs markedly from that in vein pyroxene indicating that the composition of the fluid phase involved in partial melting was distinct from that during metasomatism. In particular, the harzburgites and veins define distinct linear trends on plots of 3He/ 36Ar vs. 40Ar/ 36Ar and of 132Xe/ 36Ar vs. 40Ar/ 36Ar. Estimates of 'mantle' 132Xe/ 36Ar values by extrapolating 40Ar/ 36Ar to 40 000 yield unrealistically high values of 0.5-0.8 (olivine) and 4-5 (vein pyroxene) ruling out a simple two-component mixing of mantle and atmospheric noble gases. Rather a two-stage mixing process applies: (1) Changes in relative proportions of slab-derived element-fractionated atmospheric gases and 'mantle' produce two hybrid mixtures dominated by atmospheric gases. This may reflect interaction of slab fluids with mantle wedge fluids on a regional scale within the melting zone. (2) Subsequently mixing of these mantle-atmosphere "hybrids" occurred shortly before the entrapment of the fluids and possibly represents locally restricted compositional variations within the source region of the xenoliths.

Hopp, Jens; Ionov, Dmitri A.

2011-02-01

354

NG09 And CTBT On-Site Inspection Noble Gas Sampling and Analysis Requirements  

NASA Astrophysics Data System (ADS)

A provision of the Comprehensive Test Ban Treaty (CTBT) allows on-site inspections (OSIs) of suspect nuclear sites to determine if the occurrence of a detected event is nuclear in origin. For an underground nuclear explosion (UNE), the potential success of an OSI depends significantly on the containment scenario of the alleged event as well as the application of air and soil-gas radionuclide sampling techniques in a manner that takes into account both the suspect site geology and the gas transport physics. UNE scenarios may be broadly divided into categories involving the level of containment. The simplest to detect is a UNE that vents a significant portion of its radionuclide inventory and is readily detectable at distance by the International Monitoring System (IMS). The most well contained subsurface events will only be detectable during an OSI. In such cases, 37 Ar and radioactive xenon cavity gases may reach the surface through either "micro-seepage" or the barometric pumping process and only the careful siting of sampling locations, timing of sampling and application of the most site-appropriate atmospheric and soil-gas capturing methods will result in a confirmatory signal. The OSI noble gas field tests NG09 was recently held in Stupava, Slovakia to consider, in addition to other field sampling and analysis techniques, drilling and subsurface noble gas extraction methods that might be applied during an OSI. One of the experiments focused on challenges to soil-gas sampling near the soil-atmosphere interface. During withdrawal of soil gas from shallow, subsurface sample points, atmospheric dilution of the sample and the potential for introduction of unwanted atmospheric gases were considered. Tests were designed to evaluate surface infiltration and the ability of inflatable well-packers to seal out atmospheric gases during sample acquisition. We discuss these tests along with some model-based predictions regarding infiltration under different near-surface hydrologic conditions. We also consider how naturally occurring as well as introduced (e.g., SF6) soil-gas tracers might be used to guard against the possibility of atmospheric contamination of soil gases while sampling during an actual OSI. The views expressed here do not necessarily reflect the opinion of the United States Government, the United States Department of Energy, or Lawrence Livermore National Laboratory. This work has been performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-418791

Carrigan, Charles R.; Tanaka, Junichi

2010-05-01

355

Noble metal abundances in an Early Archean impact deposit.  

PubMed

We report detailed analyses on the concentrations of the noble metals Pd, Os, Ir, Pt, and Au in an early Archean spherule bed (S4) of probable impact origin from the lower Fig Tree Group, Barberton Greenstone Belt, South Africa. Compared to other sedimentary deposits of known or suspected impact origin, some noble metals are present in exceptionally high concentrations. Noble metal abundances are fractionated relative to abundances in chondrites with ratios of Os/Ir, Pt/Ir, Pd/Ir, and Au/Ir at only 80, 80, 41, and 2% of these values in CI chondrites. Although an extraterrestrial source is favored for the noble metal enrichment, the most plausible cause of the fractionation is by regional hydrothermal/metasomatic alteration. PMID:11537203

Kyte, F T; Zhou, L; Lowe, D R

1992-01-01

356

Preparation method for noble metal-polymer matrix nanocomposites  

Microsoft Academic Search

A method is described for the preparation of new nanocomposites based on poly(ethylene terephthalate), poly(vinyl chloride),\\u000a and polypropylene on the one hand and on noble metals (Ag and Pt) on the other. The method comprises the formation of nanoporous\\u000a polymer matrices by crazing the polymers with simultaneous incorporation of noble metal precursors (AgNO3 or H2PtCl6) into the matrices. Subsequent in

A. L. Volynskii; N. I. Nikonorova; A. V. Volkov; M. A. Moskvina; A. A. Tunyan; N. G. Yaryshev; O. V. Arzhakova; A. A. Dolgova; E. G. Rukhlya; E. S. Trofimchuk; S. S. Abramchuk; L. M. Yarysheva; N. F. Bakeev

2010-01-01

357

The stacking fault energy in noble metal alloys  

Microsoft Academic Search

A model for the stacking fault energy, ?, in noble metals and their alloys is developed which qualitatively explains many\\u000a features of experimental observations. The model is based on bothd band and free electron contributions to the cohesion. An important prediction of the model is that ? can be decreased in\\u000a noble metal alloys by the addition of a solute

T. C. Tisone; R. C. Sundahl; G. Y. Chin

1970-01-01

358

Thermal expansion of noble metals using improved lattice dynamical model  

NASA Astrophysics Data System (ADS)

Isothermal bulk modulus and volume thermal expansion for noble metals have been studied on the basis of improved lattice dynamical model proposed by Pandya et al [Physica B 307, 138-149 (2001)]. The present study shows that for all three noble metals the approach gives satisfactory results, when they are compared with experimental findings. The present study thus confirms the use of improved model to study anharmonic property, and can be extended to study temperature dependent properties in high temperature range.

Kumar, Priyank; Bhatt, N. K.; Vyas, P. R.; Gohel, V. B.

2013-06-01

359

Continuum spectra and potentials of Li-noble gas molecules  

Microsoft Academic Search

The normalized emission spectrum of the Li(2p-2s) resonance transition has been measured in the presence of 10-1000 Torr of noble gas. Fluorescence at 100-3000 A˚ from the atomic line, due to the A-X and B-X bands of Li-noble gas molecules, has been measured as a continuum with 1.5 nm resolution. The lithium is optically excited in a 670 °K cell.

R. Scheps; Ch. Ottinger; G. York; A. Gallagher

1975-01-01

360

Continuum radiation and potentials of Na-noble gas molecules  

Microsoft Academic Search

The normalized emission spectra resulting from the perturbation of Na atoms by 1-1000 Torr of noble gas have been measured in the range 10-150 nm about the 589 nm resonance line. This spectrum, due to the A-X and B-X transitions of the Na-noble gas molecules, was measured with 1.5 nm resolution. The Na, in a cell at a temperature of

George York; Richard Scheps; Alan Gallagher

1975-01-01

361

Ultracold gases: Atom SQUID  

NASA Astrophysics Data System (ADS)

Superfluid ultracold gases in designer potentials are analogous to superconducting electronic circuits. The study of these systems refines our understanding of flow and dissipation in quantum fluids, and has applications for inertial sensing and metrology.

Edwards, Mark

2013-02-01

362

Electrochemistry of Dissolved Gases.  

National Technical Information Service (NTIS)

The electrochemistry of various dissolved gases has been investigated as a function of the gas, solution pH, supporting electrolyte, electrode material, and the preconditioning of the electrode surfaces. These investigations have been conducted through th...

D. T. Sawyer

1965-01-01

363

Regulating Greenhouse Gases  

NSDL National Science Digital Library

This video highlights the work of climate scientists in the Amazon who research the relationship between deforestation, construction of new dams, and increased amounts of greenhouse gases being exchanged between the biosphere and the atmosphere.

Kqed; Domain, Teachers'

364

Noble gas isotopic fractionation between solar wind and the Sun, and implications for Genesis solar wind oxygen measurements  

NASA Astrophysics Data System (ADS)

We urge that He is the best case for a meaningful estimation of solar composition without measurement of solar wind (SW) composition; the value of such an estimation is that it may then be compared to the actual measurements, thereby leading to an empirical constraint on the degree of isotopic fractionation arising in SW and thence to how much fractionation may have affected the SW composition of other elements. We take primordial 3He/4He to be as identified in the so-called Q component identified in meteoritic materials. In the Sun, however, 3He/4He is higher because of the augmentation of 3He by D-burning, the nuclear conversion of primordial deuterium. After accounting for the D-converted 3He, we estimate 3He/4He in the present Sun (post-D burning He), and then, from the difference between this and the 3He/4He found in Genesis SW, we estimate the isotopic fractionation between them. Then, from noble gas systematics, we show that Genesis SW noble gases may be related to Q-noble gases by a mass-dependent Rayleigh-type fractionation. We develop a kinetic description of isotopic fractionation of minor components in SW relative to the solar atmosphere, which is consistent with the Rayleigh-type fractionation. This predicts fractionation in the O mass range, which is significantly different from the value used by Heber et al. (2011). The latter value corresponds to the premise that Ca-Al-rich inclusion O is the same as solar O, whence this work does not support that premise.

Ozima, M.; Suzuki, T. K.; Yamada, A.; Podosek, F. A.

2012-12-01

365

Noble gas systematics of the Hawaiian volcanoes based on the analysis of Loihi, Kilauea and Koolau submarine rocks  

NASA Astrophysics Data System (ADS)

Noble gas isotopes were analyzed for glass and olivine phenocrysts of Hawaiian submarine volcanic rocks collected at depths of 2300-5700 m using submersibles "Shinkai 6500" and "Kaiko". Both crushing and heating methods were used for extracting noble gases. Loihi samples had 3He/4He of 21-32 Ra, 20Ne/22Ne of 10-12 and 40Ar/36Ar of 300-2700, while Kilauea samples had 3He/4He of 13-15 Ra, 20Ne/22Ne of 10.6-11.1, and 40Ar/36Ar of 800-3600. For all samples analyzed, the 129Xe/130Xe cannot be distinguished from the atmospheric value within analytical uncertainty. Olivine separates from two Koolau basaltic rocks collected at depths of about 3600 m and 3100 m have 3He/4He of about 19 Ra, whereas other Koolau samples collected at depths of less than 3000 m have 3He/4He of 14-15 Ra like subaerial Koolau rocks. The samples collected from Loihi, in the pre-shield stage, contain both higher and more variable values of 3He/4He compared to the shield-building stage of other volcanoes in the Hawaiian chain. The post-shield and rejuvenated stages show the lowest 3He/4He, overlapping values obtained for MORB. We interpret this age trend to reflect an increasing degree of interaction between the rising plume magma and the uppermost part of asthenosphere. The extreme He isotope variation shown at Loihi may represent additional interaction of the plume magma with the old, altered oceanic crust. The variation of heavier noble gases may indicate incorporation of seawater into the magma before eruption.

Kaneoka, Ichiro; Hanyu, Takeshi; Yamamoto, Junji; Miura, Yayoi N.

366

Noble gas tracing of groundwater/coalbed methane interaction in the San Juan Basin, USA  

NASA Astrophysics Data System (ADS)

The San Juan Basin natural gas field, located in northwestern New Mexico and southwestern Colorado in the USA, is a case-type coalbed methane system. Groundwater is thought to play a key role in both biogenic methane generation and the CO 2 sequestration potential of coalbed systems. We show here how noble gases can be used to construct a physical model that describes the interaction between the groundwater system and the produced gas. We collected 28 gas samples from producing wells in the artesian overpressured high production region of the basin together with 8 gas samples from the underpressured low production zone as a control. Stable isotope and major species determination clearly characterize the gas in the high production region as dominantly biogenic in origin, and the underpressured low producing region as having a significant admix of thermogenic coal gas. 3He/ 4He ratios increase from 0.0836R a at the basin margin to 0.318R a towards the center, indicating a clear but small mantle He signature in all gases. Coherent fractionation of water-derived 20Ne/ 36Ar and crustal 4He/ 40Ar* are explained by a simple Rayleigh fractionation model of open system groundwater degassing. Low 20Ne concentrations compared to the model predicted values are accounted for by dilution of the groundwater-associated gas by desorbed coalbed methane. This Rayleigh fractionation and dilution model together with the gas production history allows us to quantify the amount of water involved in gas production at each well. The quantified water volumes in both underpressured and overpressured zones range from 1.7 × 10 3 m 3 to 4.2 × 10 5 m 3, with no clear distinction between over- and underpressured production zones. These results conclusively show that the volume of groundwater seen by coal does not play a role in determining the volume of methane produced by secondary biodegradation of these coalbeds. There is no requirement of continuous groundwater flow for renewing the microbes or nutrient components. We furthermore observe strong mass related isotopic fractionation of 20Ne/ 22Ne and 38Ar/ 36Ar isotopic ratios. This can be explained by a noble gas concentration gradient in the groundwater during gas production, which causes diffusive partial re-equilibration of the noble gas isotopes. It is important for the study of other systems in which extensive groundwater degassing may have occurred to recognize that severe isotopic fractionation of air-derived noble gases can occur when such concentration gradients are established during gas production. Excess air-derived Xe and Kr in our samples are shown to be related to the diluting coalbed methane and can only be accounted for if Xe and Kr are preferentially and volumetrically trapped within the coal matrix and released during biodegradation to form CH 4.

Zhou, Zheng; Ballentine, Chris J.; Kipfer, Rolf; Schoell, Martin; Thibodeaux, Steve

2005-12-01

367

Noble magnetic barriers in the ASDEX UG tokamak  

NASA Astrophysics Data System (ADS)

The second-order perturbation method of creating invariant tori inside chaos in Hamiltonian systems (Ali, H.; Punjabi, A. Plasma Phys. Contr. F. 2007, 49, 1565-1582) is applied to the axially symmetric divertor experiment upgrade (ASDEX UG) tokamak to build noble irrational magnetic barriers inside chaos created by resonant magnetic perturbations (m, n)=(3, 2)+(4, 3), with m and n the poloidal and toroidal mode numbers of the Fourier expansion of the magnetic perturbation. The radial dependence of the Fourier modes is ignored. The modes are considered to be locked and have the same amplitude ?. A symplectic mathematical mapping in magnetic coordinates is used to integrate magnetic field line trajectories in the ASDEX UG. Tori with noble irrational rotational transform are the last ones to be destroyed by perturbation in Hamiltonian systems. For this reason, noble irrational magnetic barriers are built inside chaos, and the strongest noble irrational barrier is identified. Three candidate locations for the strongest noble barrier in ASDEX UG are selected. All three candidate locations are chosen to be roughly midway between the resonant rational surfaces ?32 and ?43. ? is the magnetic coordinate of the flux surface. The three candidate surfaces are the noble irrational surfaces close to the surface with q value that is a mediant of q=3/2 and 4/3, q value of the physical midpoint of the two resonant surfaces, and the q value of the surface where the islands of the two perturbing modes just overlap. These q values of the candidate surfaces are denoted by qMED, qMID, and qOVERLAP. The strongest noble barrier close to qMED has the continued fraction representation (CFR) [1;2,2,1?] and exists for ??2.6599×10-4; the strongest noble barrier close to qMID has CFR [1;2,2,2,1?] and exists for ??4.6311×10-4; and the strongest noble barrier close to qOVERLAP has CFR [1;2,2,6,2,1?] and exists for ??1.367770×10-4. From these results, the strongest noble barrier is found to be close to the surface that is located physically exactly in the middle of the two resonant surfaces.

Ali, Halima; Punjabi, Alkesh; Vazquez, Justin

368

The unsuspected origin of gold's nobleness  

NASA Astrophysics Data System (ADS)

Understanding the ``inertness'' of Au toward oxidizing agents - appreciated since long before the beginning of recorded history -- has remained a challenge. Its nobleness has long been attached to its weak interaction with adsorbates, which contrasts with the fact that Au forms stable alloys and can be made reactive. Density-functional-theory (DFT) calculations of the binding energy (BE) of O on (111) surfaces, in fact, have shown that Au stands out for rendering the weakest BE. Here, we reveal the origin of gold's unique inertness by revising the adsorption of this prototype oxidizing agent on several (111) metal surfaces. We show via DFT that, judging by BE of O on Au(111) and Ag(111), e.g., both the d-band-center argument and analysis of the electronic density of states fail to describe the relatively low reactivity of Au. Nevertheless, we establish that, rather than failure of the above paradigms, a key element to understand BE of adsorbates has been left behind so far. Namely, we demonstrate that, although BE of O is higher on Ag(111) than on Au(111), (1) The local Au-O bonds are indeed stronger than the Ag-O ones; (2) the low BE of O on Au is, paradoxically, caused by an unusually large perturbation on Au-Au bonds upon O adsorption.

Alcantara Ortigoza, Marisol; Stolbov, Sergey

2013-03-01

369

Noble gas atmospheric monitoring at reprocessing facilities  

SciTech Connect

The discovery in Iraq after the Gulf War of the existence of a large clandestine nuclear-weapon program has led to an across-the-board international effort, dubbed Programme 93+2, to improve the effectiveness and efficiency of International Atomic Energy Agency (IAEA) safeguards. One particularly significant potential change is the introduction of environmental monitoring (EM) techniques as an adjunct to traditional safeguards methods. Monitoring of stable noble gas (Kr, Xe) isotopic abundances at reprocessing plant stacks appears to be able to yield information on the burnup and type of the fuel being processed. To estimate the size of these signals, model calculations of the production of stable Kr, Xe nuclides in reactor fuel and the subsequent dilution of these nuclides in the plant stack are carried out for two case studies: reprocessing of PWR fuel with a burnup of 35 GWd/tU, and reprocessing of CAND fuel with a burnup of 1 GWd/tU. For each case, a maximum-likelihood analysis is used to determine the fuel burnup and type from the isotopic data.

Nakhleh, C.W.; Perry, R.T. Jr.; Poths, J.; Stanbro, W.D.; Wilson, W.B.; Fearey, B.L.

1997-05-01

370

Noble gas incorporation in sputtered and ion beam assisted grown silicon films  

SciTech Connect

Gas desorption measurements have been performed on sputter deposited silicon films. The sputter gas was argon or krypton. Parameters influencing the incorporation process e.g. bias voltage, substrate temperature and arrival rate ratio of silicon and noble gas atoms have been systematically varied. The films, a-Si and c-Si, have been characterised by various techniques for composition and defect analysis. A model has been applied to describe the composition of the growing silicon layer. Underlying mechanisms like gas-gas sputtering have been studied in separate ion implantation experiments. For a-Si concentrations as high as 6% Ar and Kr have been found. An important effect is the injection of self-interstitial atoms caused by the low energy heavy ion bombardment. It causes the layer to grow without large open volume defects.

van Veen, A. [Technische Hogeschool Delft (Netherlands). Inter-Faculty Reactor Inst.; Greuter, M.J.W.; Niesen, L. [Groningen Univ., (Netherlands). Dept. of Physics; Nielsen, B.; Lynn, K.G. [Brookhaven National Lab., Upton, NY (United States)

1991-12-31

371

Noble gas incorporation in sputtered and ion beam assisted grown silicon films  

SciTech Connect

Gas desorption measurements have been performed on sputter deposited silicon films. The sputter gas was argon or krypton. Parameters influencing the incorporation process e.g. bias voltage, substrate temperature and arrival rate ratio of silicon and noble gas atoms have been systematically varied. The films, a-Si and c-Si, have been characterised by various techniques for composition and defect analysis. A model has been applied to describe the composition of the growing silicon layer. Underlying mechanisms like gas-gas sputtering have been studied in separate ion implantation experiments. For a-Si concentrations as high as 6% Ar and Kr have been found. An important effect is the injection of self-interstitial atoms caused by the low energy heavy ion bombardment. It causes the layer to grow without large open volume defects.

van Veen, A. (Technische Hogeschool Delft (Netherlands). Inter-Faculty Reactor Inst.); Greuter, M.J.W.; Niesen, L. (Groningen Univ., (Netherlands). Dept. of Physics); Nielsen, B.; Lynn, K.G. (Brookhaven National Lab., Upton, NY (United States))

1991-01-01

372

METHODS AND RESULTS OF RECONSTRUCTION OF NOBLE GAS RELEASES FROM THE STACKS OF THE MAYAK PA GRAPHITE REACTORS OVER THE WHOLE PERIOD OF THEIR OPERATION  

SciTech Connect

Brief analysis of design features and operational modes of Mayak PA industrial graphite-uranium reactors (PUGRs) is given. The above mentioned Mayak PA PUGRs determined the rates of releases of radioactive noble gases (RNG) from activation (41Ar) and fission (isotopes of Krypton and Xenon) through the vent stack of the reactor. Information is given on methods and results of experimental determination of RNG atmospheric releases for the period starting from 1965 till PUGRs decommissioning in 1987-1990. A calculation method for reconstruction of radioactive noble gas releases is proposed and justified. The results of reconstruction are given. It is shown that maximum rates of RNG releases from PUGRs high stacks were observed in the 1950s, when ordinary atmospheric air was used as a cover gas for the reactor graphite stacks and gas purification systems (flow-type gas holders) had not been installed yet.

Glagolenko, Y. V.; Drozhko, Evgeniy G.; Mokrov, Y.; Pyatin, N. P.; Rovny, Sergey I.; Anspaugh, L. R.; Napier, Bruce A.

2008-06-01

373

Solids, Liquids, and Gases  

NSDL National Science Digital Library

In this project you will research solids, liquids, and gases. By the end of this project you will be able to answer the question: Can you tell what is alike and different between solids, liquids, and gases? Read the song about matter. song with music about matter Record your observations on the organizer provided by the teacher. On the diagram write the word solid in one of the circles. Write liquid in one of the circles and write gas in the last circle. As you collect your information write your information under ...

Sibley, Ms.

2009-10-22

374

Isotopic studies of rare gases in terrestrial samples and natural nucleosynthesis  

SciTech Connect

This project is concerned with research in rare gas mass spectrometry. Using a two-pronged attack, we study fluids using a system (RARGA) designed for fluid analysis in bulk which is sometimes deployed in the field and a laser microprobe mass spectrometer for fluid inclusion studies. In 1991 the RARGA project continued monitoring helium isotope variations associated with renewed seismic activity in Long Valley Caldera and expanded our geothermal data base to include Lassen National Park. An important objective, continuing in 1992, 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. To this end, 1991 saw continued efforts to understand variations in composition between fluids and associated reservoir rocks and extended the data base to include fluids from the Gulf of Mexico. Our DOE work in calibrating a sensitive laser microprobe mass spectrometer for noble gases in fluid inclusions continues with successful returns particularly in calibrating neutron irradiated samples for tracing halogen ratios. In connection with observations of neutron-produced noble gas nuclides in granites, we have begun comparing measurements with calculations for both thermal and epithermal neutrons. We submitted a third paper on noble gases in diamonds, concentrating on observed effects of {sup 4}He, {sup 3}He, and fission xenon implantation from nuclear processes in adjacent material in the matrix rock. 16 refs., 1 tab.

Not Available

1991-05-01

375

Isotopic studies of rare gases in terrestrial samples and natural nucleosynthesis. Progress report  

SciTech Connect

This project is concerned with research in rare gas mass spectrometry. Using a two-pronged attack, we study fluids using a system (RARGA) designed for fluid analysis in bulk which is sometimes deployed in the field and a laser microprobe mass spectrometer for fluid inclusion studies. In 1991 the RARGA project continued monitoring helium isotope variations associated with renewed seismic activity in Long Valley Caldera and expanded our geothermal data base to include Lassen National Park. An important objective, continuing in 1992, 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. To this end, 1991 saw continued efforts to understand variations in composition between fluids and associated reservoir rocks and extended the data base to include fluids from the Gulf of Mexico. Our DOE work in calibrating a sensitive laser microprobe mass spectrometer for noble gases in fluid inclusions continues with successful returns particularly in calibrating neutron irradiated samples for tracing halogen ratios. In connection with observations of neutron-produced noble gas nuclides in granites, we have begun comparing measurements with calculations for both thermal and epithermal neutrons. We submitted a third paper on noble gases in diamonds, concentrating on observed effects of {sup 4}He, {sup 3}He, and fission xenon implantation from nuclear processes in adjacent material in the matrix rock. 16 refs., 1 tab.

Not Available

1991-05-01

376

Noble Gas Tracing of Subsurface CO2 Origin and the Role of Groundwater as a CO2 Sink  

NASA Astrophysics Data System (ADS)

The source, generation, migration and accumulation of CO2 gas associated either alone or with hydrocarbons are unclear and therefore hard to predict. So far, noble gases provide one of the best tools to resolve this question, because they are conservative within the subsurface system. The atmosphere-derived noble gases dissolved in groundwater do not react with the rock system, while noble gases produced in the rock phase by radioactive decay or input from magmatic source are isotopically distinct and can be resolved from the dissolved air-derived noble gases. 10 samples were taken from a CO2-rich natural gas reservoir in Jackson Dome, Mississippi, USA to investigate its origin and extent of interaction with the groundwater system. The area lies within the Mississippi Interior Salt Basin. It is bounded on the north by the Pickens-Gilbertown fault system, the updip limit of the Jurassic Louann Salt unit, and on the south by basement highs of the Wiggins, South Mississippi, and Lasalle uplifts. We present compositional, stable isotope and noble gas results of Jackson Dome samples. Gas composition is 98.75-99.38% CO2, with small amounts of methane and nitrogen. CO2 content increases linearly with the decrease of CH4. d13C(CO2) in all samples ranges between -3.55 and -2.57 per mil, increasing with the increase of the CO2 content. Atmosphere-derived He contributions are negligible in all cases. 3He/4He ratios are between 4.27 and 5.01Ra, indicating a strong mantle signature. Crustal 4He in these samples therefore accounts for between 7.0% and 20.8%, the remainder being magmatic in origin. 40Ar/36Ar ratios are all above air ratio, ranging between 4071 and 6420. Air corrected 40Ar* vary between 92.7 and 95.4%, to give 4He/40Ar* ratios of between 1.26 and 2.52. This range is comparable with values estimated for the upper mantle. CO2/3He values are between 1.09E+9 and 4.62E+9, and also fall in the mantle range, indicating that the CO2 gas in Jackson Dome is also predominantly mantle in origin. 20Ne is dominantly sourced from the groundwater. A strong anti-correlation between 20Ne and CO2/3He, is indicative that groundwater plays the principle control in changing the CO2/3He ratio. Because 3He is conservative, this is probably by CO2 loss into the water phase and seems to account for the 75% reduction from initial CO2/3He

Zhou, Z.; Ballentine, C. J.; Schoell, M.; Stevens, S. H.

2003-12-01

377

Reply to: “Recycled” volatiles in mantle derived diamonds—Evidence from nitrogen and noble gas isotopic data  

NASA Astrophysics Data System (ADS)

In a reinterpretation of our published rare gas data obtained on polycrystalline diamonds from the Orapa kimberlite (Botswana) [C.E. Gautheron, P. Cartigny, M. Moreira, J.W. Harris and C.J. Allègre, 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.], Mohapatra and Honda [R.K. Mohapatra, and M. Honda, "Recycled" volatiles in mantle derived diamonds—evidence from nitrogen and noble gas isotopic data, Earth Planet. Sci. Lett., this issue, 2006.] claim that mixing between a-priori defined proportions of subducted seawater, subducted recycled oceanic crust, recycled sediments, air and the mantle would be more appropriate to account for the observations. This view sharply contrasts with our conclusions that the chemical and isotope compositions of rare gases record diamond formation from mantle-derived fluid(s) together with mantle post-crystallization radiogenic/nucleogenic/fissiogenic ingrowth and preferential diffusion of the lightest atoms out of the diamonds in the mantle [C.E. Gautheron, P. Cartigny, M. Moreira, J.W. Harris and C.J. Allègre, 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.]. We present here reasons why the alternative view of Mohapatra and Honda [R.K. Mohapatra and M. Honda, "Recycled" volatiles in mantle derived diamonds—evidence from nitrogen and noble gas isotopic data, Earth Planet. Sci. Lett., this issue, 2006.] is not supportable.

Gautheron, Cécile; Cartigny, Pierre; Moreira, Manuel; Harris, Jeff W.; Allègre, Claude J.

2006-11-01

378

Noble gas paleotemperatures and water contents of stalagmites - a new extraction tool and a new paleoclimate proxy  

NASA Astrophysics Data System (ADS)

Stalagmites represent excellent multi-proxy paleoclimate archives as they cover long timescales and can be dated with high precision [e.g., 1]. The absolute temperature at which a stalagmite grew, can be deduced from the amounts of atmospheric noble gases dissolved in the stalagmite's fluid inclusion water (= noble gas temperature, NGT) [2-4]. We present technical advances towards more robust NGT determinations and also propose a new paleoclimate proxy, namely the stalagmite's water content, which is a "by-product" of NGT determination. Water contents and oxygen isotope records of two Holocene stalagmites from Socotra Island (Yemen) were found to vary systematically: progressively lighter oxygen is accompanied by decreasing water contents and vice versa. Via the oxygen isotope records [5] the stalagmites' water contents are linked to the amounts of precipitation on Socotra Island. High precipitation, i.e., high drip rates lead to homogeneous calcite growth with low porosity and therefore a small number of water-filled inclusions, i.e. low water contents. A reduction of drip water supply fosters irregular crystal growth with higher porosity, leading to higher water contents of the calcite (see also [6]). Therefore the stalagmites' water contents seem to record changes in drip water supply and, under favourable conditions, changes in regional precipitation. The current method to extract water and noble gases from stalagmite samples is experimentally challenging and subject to certain limitations (e.g., time-consuming sample preparation in a glove box, temperature restrictions for water extraction, and the often inadequate correction for air from residual air-filled inclusions [3, 4]). To overcome these limitations we have developed a new type of crusher directly attached to our noble gas line. It not only allows crushing and separating the samples into different grain size fractions in vacuo, but the separates can be individually heated to significantly higher temperatures than before allowing a more quantitative water extraction. Additionally, air released from air-filled inclusions can be analyzed during the crushing procedure with a new quadrupole mass spectrometer. This additional piece of information will considerably improve the above mentioned corrections resulting in more robust and accurate NGTs. [1] Henderson G.M. (2006) Science, 313, 620-622. [2] Kluge T., et al. (2008) Earth Planet. Sc. Lett., 269, 408-415. [3] Scheidegger Y.M., et al. (2010) Chem. Geol., 272, 31-39. [4] Scheidegger Y.M., et al. (2011) Chem. Geol., 288, 61-66. [5] Fleitmann D., et al. (2007) Quart. Sci. Rev., 26, 170-188. [6] Fairchild I.J., et al. (2008) Speleothems, in Geochemical sediments and landscapes, Blackwell Publishing Ltd.: Oxford, UK. 200-245.

Vogel, N.; Scheidegger, Y.; Brennwald, M. S.; Fleitmann, D.; Figura, S.; Wieler, R.; Kipfer, R.

2012-04-01

379

Experimental Study of Noble Gas Partitioning and Diffusion in Common Crustal Minerals  

NASA Astrophysics Data System (ADS)

Recent study [e.g. 1,2,3] has shown that the partitioning of noble gases amongst system phases (including minerals, fluids, and grain boundaries) is fundamental to thermochronologic models and interpretations of the commonly used K/Ar and U-Th/He decay systems. However, little direct data on noble gas partitioning between common minerals of the crust exists. We have investigated two experimental methods to measure noble gas partitioning between quartz, K-feldspar, plagioclase feldspar, and phlogopite. First, piston cylinder experiments employed an irradiated fluorite powder as a solid source of Ar-37 and He-4 within which multiple minerals were packed and allowed to exchange noble gases over experimental durations of 1-2 weeks and conditions of 925 C and 1.5 GPa. This Ar-37 source was used to avoid analytical artifacts of atmospheric Ar surface contamination. Results from the piston cylinder experiment show marked diffusive loss from the doped fluorite, but virtually no diffusive uptake of Ar-37 into any of the mineral phases in the capsule. The lack of measurable Ar-37 in the minerals suggests that Ar-37 is heavily partitioned into the grain boundary network, or that Ar-37 has leaked from the capsule. At the same time, piston cylinder results also indicate near uniform uptake of more rapidly diffusing He-4 into all minerals, which would suggest that the partition coefficient of He-4 between all of the silicate mineral phases present in the experiments is roughly equal to 1. Additional experiments are being conducted to reproduce this preliminary result. Second, minerals were exposed to pressurized argon gas in cold seal experiments over a period of 20 days at temperatures ranging from 825 to 485 C. Diffusive uptake profiles measured by UV-laser depth profiling and, in the case of quartz, also by Rutherford Backscattering, are observed for Ar in phlogopite, quartz, and feldspars. To our knowledge, this is the first time that a combined RBS/UV-laser depth profile has been reported for a single sample. Theoretically, equilibrium surface concentrations extrapolated from simple diffusion profiles in each mineral may be ratio-ed to extract mineral-mineral partition coefficients. Apparently anomalous high surface Ar concentrations were found in all minerals during UV-laser analysis, corroborating observations from previous studies [cf. 4]. RBS analysis of quartz confirmed the high concentrations but revealed quite different diffusive behavior in the near surface ~200nm region versus deeper (~100 microns) diffusive penetration (measured by UV-laser). This suggests the possibility of multiple, discrete diffusive pathways thus complicating partitioning interpretations. Additional cold seal experiments will involve the use of He-3 and Ne-22 wherein further assessment of near surface versus deeper diffusion regimes should be possible in all minerals. [1] Kelley SP (2002) Chem. Geol. 188, p. 1-22; [2] Baxter EF (2003) EPSL 216, p. 619-634; [3] Watson EB & Cherniak DJ (2003) GCA 67, p. 2043-2062; [4] Wartho JA et al. (1999) EPSL 170, p. 141-153.

Clay, P. L.; Baxter, E. F.; Kelley, S. P.; Watson, E. B.; Thomas, J. B.; Cherniak, D. J.

2005-12-01

380

Solids, Liquids, and Gases  

NSDL National Science Digital Library

What do you know about the 3 states of matter? Good Morning 2nd graders! Today we will be learning about the different states of matter : solids, liquids, and gases . Have fun working with your partner and follow directions carefully! First, make sure you get a 3 column graphic organizer and fill ...

Swaim, Mrs.

2012-12-01

381

Strongly interacting Fermi gases  

NASA Astrophysics Data System (ADS)

Strongly interacting gases of ultracold fermions have become an amazingly rich test-bed for many-body theories of fermionic matter. Here we present our recent experiments on these systems. Firstly, we discuss high-precision measurements on the thermodynamics of a strongly interacting Fermi gas across the superfluid transition. The onset of superfluidity is directly observed in the compressibility, the chemical potential, the entropy, and the heat capacity. Our measurements provide benchmarks for current many-body theories on strongly interacting fermions. Secondly, we have studied the evolution of fermion pairing from three to two dimensions in these gases, relating to the physics of layered superconductors. In the presence of p-wave interactions, Fermi gases are predicted to display toplogical superfluidity carrying Majorana edge states. Two possible avenues in this direction are discussed, our creation and direct observation of spin-orbit coupling in Fermi gases and the creation of fermionic molecules of 23Na 40K that will feature strong dipolar interactions in their absolute ground state.

Bakr, W.; Cheuk, L. W.; Ku, M. J.-H.; Park, J. W.; Sommer, A. T.; Will, S.; Wu, C.-H.; Yefsah, T.; Zwierlein, M. W.

2013-08-01

382

Biomedical imaging using hyperpolarized noble gas MRI: Pulse sequence considerations  

NASA Astrophysics Data System (ADS)

Hyperpolarized noble gas MRI is a new technique for imaging of gas spaces and tissues that have been hitherto difficult to image, making it a promising diagnostic tool. The unique properties of hyperpolarized species, particularly the non-renewability of the large non-equilibrium spin polarization, raises questions about the feasibility of hyperpolarized noble gas MRI methods. In this paper, the critical issue of T1 relaxation is discussed and it is shown that a substantial amount of polarization should reach the targets of interest for imaging. We analyse various pulse sequence designs, and point out that total scan times can be decreased so that they are comparable or shorter than tissue T1 values. Pulse sequences can be optimized to effectively utilize the non-renewable hyperpolarization, to enhance the SNR, and to eliminate image artifacts. Hyperpolarized noble gas MRI is concluded to be quite feasible.

Zhao, Lei; Albert, Mitchell S.

1998-02-01

383

Quest for high brightness, monochromatic noble gas ion sources  

SciTech Connect

Focused ion beam (FIB) machines are key tools for state-of-the art sample preparation in electron microscopy, for characterization and repair in material sciences, for the semiconductor industry and for nanotechnology in general. Liquid-metal ion sources (LMIS) are widely used in FIB machines because they meet the minimum ion source requirements such as source brightness and reliability. However, in FIB machines, noble gas ion sources are favorable for sputtering, beam-induced etching and deposition, because the implanted ions do not change the electrical behavior of the substrate significantly. There are several efforts by various researchers to develop noble gas ion sources that can be used in FIB machines instead of LMIS. The gas ion sources could not meet the minimum ion source requirements. Therefore, LMIS are still a popular choice among FIB machine users. This review article takes a critical look at the reported efforts in the literature to develop noble gas ion sources for FIB machines.

Tondare, V.N. [Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft (Netherlands)

2005-11-15

384

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

NASA Astrophysics Data System (ADS)

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 in both samples are at the maximum level observed for CI and CM chondrites, suggesting high abundances of presolar diamonds and SiC/graphite, respectively. The cosmic-ray exposure age cannot be determined precisely, because the shielding depth of our Tagish Lake samples is unknown, but the minimum exposure age was determined to be 5.5±0.7 Myr on the basis of cosmogenic 21Ne concentrations and the highest 21Ne production rate. X-ray and electron-microscopic study showed that the carbonate-rich lithology is dominated by loosely packed porous matrix that consists mainly of fine-grained saponite and ferromagenesian carbonate. The matrix contains very few chondrules, but many fine-grained clasts having angular shape with longest dimensions up to 1 mm. The clasts differ from host matrix in both texture and mineralogy. They are massive, compacted material with porosity much lower than matrix and contain abundant magnetite and a coherent intergrowth of serpentine and saponite that is rare in matrix. The presence of texturally and mineralogically distinct clasts indicates that the carbonate-rich lithology is a breccia, but the absence of solar noble gases and impact-induced deformational features in host matrix distinguish it from an asteroid regolith breccia. Our results instead indicate that it is an accretionary breccia formed by simultaneous accretion of diverse objects in a massive dust cloud. The clasts often enclose chondrules and anhydrous silicate fragments such as low-iron-manganese-enriched olivines. This observation and their highly compacted, angular morphology suggests that the clasts derive from earlier-formed chondritic materials which have experienced compression and fragmentation due to mild impacts and from which they were excavated and incorporated into the final rock. It is thus suggested that, in the course of planetesimal formation, agglomeration and disagglomeration of small parent bodies occurred repeatedly in a dense dust cloud where solar wind from the infant sun was shielded. The fine-grained ferromagnesian carbonates must have precipitated from aqueous solutions after the assembly of the Tagish Lake asteroid from recycled materials from previous bodies, because the carbonates coat the surfaces of pores and fill in veins in the clasts.

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

2003-02-01

385

Noble liquid detectors for fundamental physics and applications  

NASA Astrophysics Data System (ADS)

Noble liquid detectors come in many sizes and configurations and cover a lot of ground as particle and radiation detectors: from calorimeters for colliders to imaging detectors for neutrino physics and proton decay to WIMP Dark Matter detectors. It turns out that noble liquid detectors are a mature technology for imaging and spectroscopy of gamma rays and for neutron detection, a fact that makes them suitable for applications, e.g. cargo scanning and Homeland Security. In this short paper I will focus on liquid xenon and liquid argon, which make excellent detectors for hypothetical WIMP Dark Matter and neutrinos and for much less exotic gamma rays.

Curioni, A.

2009-12-01

386

Use of noble metals in automobile exhaust catalysts  

SciTech Connect

This is a review of recent literature involving laboratory work on catalytic reactions of interest in automobile exhaust purification. The review is concerned with the noble metals Pt, Pd, and Rh, the oxidation of CO and hydrocarbons, the reduction of NO, and the water-gas-shift and steam-re-forming reactions. Current thoughts are given about the mechanisms of these reactions, the dependence of the reaction rates on particle size, when known, and the role of the impurity SO/sub 2/. The current opinion that alloy formation between the noble metals is detrimental and segregation beneficial is supported by literature references.

Kummer, J.T.

1986-09-25

387

Signal crayfish, Pacifastacus leniusculus, as a vector for Psorospermium haeckeli to noble crayfish, Astacus astacus  

Microsoft Academic Search

As part of investigations of the ecological impact and transmission of the crayfish parasite Psorospermium haeckeli, a laboratory experiment was performed where noble crayfish, Astacus astacus, and signal crayfish, Pacifastacus leniusculus, from populations in which P. haeckeli had not been detected, were fed with each other in all combinations. Noble crayfish fed noble crayfish did not acquire P. haeckeli during

Rolf Gydemo

1996-01-01

388

Spectroscopic enhancement from noble mettalic nanoparticles  

NASA Astrophysics Data System (ADS)

Resonant coupling of localized surface plasmon resonances (LSPRs) in noble metallic nanostructures to incident radiation and the related subject of localized behavior of electromagnetic waves are currently of great interest due to their potential application to sensors, biochemical assays, optical transmission, and photovoltaic devices. My thesis research is made up of two related parts. In part one I examined enhanced fluorescence in dye molecules in proximity to Ag nanostructures. In part two I studied the effect of Au nanostructure arrays on the performance of poly(3-hexylthiophene-2,5-diyl) : [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk heterojunction (BHJ) organic solar cells (OSCs). Nanostructures were fabricated by two different methods: e-beam lithography (top down) and spray pyrolysis (bottom up). Using e-beam lithography, we produced arrays of nanostructures with well defined shapes, sizes, and spacings. By systematically varying these topographical parameters, we measured their effect on nanometer-sized metallic structure-enhanced fluorescence (nMEF) and on absorption and external quantum efficiency (EQE) in OSC devices as a function of optical wavelength. In analyzing experimental results, we carried out numerical simulations of the local electric field under incident light, across plasmonic resonances. The comparison between the calculated local field squared and measured fluorescence/EQE provides physical insight on the configuration-dependence of these two processes. Our results indicate that local field enhancement near nanostructures is dominant in nMEF, and that the local field is strongly affected by the substrate and device architectures. For the OSCs, both measurements and calculations show that absorbance within the active layer is enhanced only in a narrow band of wavelengths (˜640-720 nm) where the active layer is not very absorbing for our prototype nanopillar-patterned devices. The peak enhancement for 180 nm wide Au nanopillars was approximately 60% at 675nm. The corresponding resonance involves both localized surface plasmon excitation and multiple reflections/diffraction within the cavity formed by the electrodes. Finally, we explore the role of the size of the nanostructures in such a device on the optical absorption in the OSC active layer. We find that small Au nanopillars produce strong internal absorption resulting in Joule heating, and suppressing the desired enhancement in EQE in OSC devices.

Tsai, Shu-Ju

389

Volcanic Gases and Their Effects  

MedlinePLUS

... Please see the web article, " Volcanic Gases and Climate Change Overview " for additional information. Hydrogen sulfide (H 2 S) ... Please see the web article, " Volcanic Gases and Climate Change Overview " for more information on Volcanic versus anthropogenic ...

390

Noble gas isotope sites and mobility in mafic rocks and olivine  

NASA Astrophysics Data System (ADS)

Important He and Ar isotope studies on rocks and minerals, relevant to the geochemical and degassing history of the Earth, are often hampered by insufficient knowledge of the retentivity of different types of sites in minerals (inclusions, matrix) for these species, and of the relative importance of radiogenic and trapped components and possible differences in their behavior. To identify sites of noble gas isotopes, shed some light on their origin and estimate their residence times in olivine, which is a mineral considered as a good natural sampler, we investigated 2.5 Ga old ultramafic rocks from the Monche Pluton (Kola Peninsula, north-east part of the Baltic shield) using several extraction methods: crushing, fusion, slow step-wise and rapid incremental heating. Previous studies indicated that these rocks contain mainly trapped noble gases; however, to constrain the possible contribution of in-situ generated radiogenic helium, U and Th concentrations were also measured in the samples. The helium release pattern obtained by relatively fast (˜1.5 h long) incremental heating of olivine includes three distinct release peaks for helium: a low-temperature (600 °C) l-peak, a middle (800-1100 °C) m-peak and a high-temperature (˜1400 °C) h-peak. However, helium extraction from a powdered aliquot of the same olivine yields mainly the middle m-peak indicating that gases released in the l- and h-peaks occupy gas-liquid inclusions opened in the course of crushing and grinding. Moreover, slow step-wise heating (14 h) also results in a broad He release peak but in two well-separated l- and h-peaks of non-atmospheric 40Ar?. This feature implies helium migration from l- and h-vesicles into the matrix m during long step-wise heating experiments, whereas less movable Ar remains in inclusions at even relatively high almost-magmatic temperatures. Using a simple phenomenological model envisaging the three different residence sites for noble gases, both fast- and slow-heating release patterns for 40Ar? and He, including those for the crushed sample, could be reproduced. The diffusion parameters inferred from the modeling of olivine ( D0 = 2.4 × 10 -2 cm 2 s -1 and Ea = 133 kJ mol -1) are similar to those published by Shuster et al. (2003) and Blard et al. (2008). The high matrix/fluid solubility coefficient for helium, HHe ˜ 0.01, exceeds estimates reported by Trull and Kurz (1993); however, the product DHe( T) × HHe, the "permeability" (that governs He migration in vesicles + matrix composed materials), is very similar to their value. Extrapolation to the ambient temperature (0 °C) gives long and similar helium residence times in l- and h-vesicles, exceeding 10 10 yrs, and even longer time scales ˜10 16 yrs are obtained for the helium residence in the matrix. Therefore, at low temperatures our samples may be considered as excellent samplers of trapped volatile species, including helium.

Tolstikhin, I.; Kamensky, I.; Tarakanov, S.; Kramers, J.; Pekala, M.; Skiba, V.; Gannibal, M.; Novikov, D.

2010-02-01

391

Gravitational separation of gases and isotopes in polar ice caps.  

PubMed

Atmospheric gases trapped in polar ice at the firn to ice transition layer are enriched in heavy isotopes (nitrogen-15 and oxygen-18) and in heavy gases (O(2)/N(2) and Ar/N(2) ratios) relative to the free atmosphere. The maximum enrichments observed follow patterns predicted for gravitational equilibrium at the base of the firn layer, as calculated from the depth to the transition layer and the temperature in the firn. Gas ratios exhibit both positive and negative enrichments relative to air: the negative enrichments of heavy gases are consistent with observed artifacts of vacuum stripping of gases from fractured ice and with the relative values of molecular diameters that govern capillary transport. These two models for isotopic and elemental fractionation provide a basis for understanding the initial enrichments of carbon-13 and oxygen-18 in trapped CO(2), CH(4), and O(2) in ice cores, which must be known in order to decipher ancient atmospheric isotopic ratios. PMID:17730578

Craig, H; Horibe, Y; Sowers, T

1988-12-23

392

Studies on PEM fuel cell noble metal catalyst dissolution  

Microsoft Academic Search

A combination of electrochemical, spectroscopic and gravimetric methods was carried out on Proton Exchange Membrane (PEM) fuel cell electrodes with the focus on platinum and ruthenium catalysts dissolution, and the membrane degradation. In cyclic voltammetry (CV) experiments, the noble metals were found to dissolve in 1M sulfuric acid solution and the dissolution increased exponentially with the upper potential limit (UPL)

Shuang Ma Andersen; Laila Grahl-Madsen; Eivind M. Skou

2011-01-01

393

A Model of Nuclear Recoil Scintillation Efficiency in Noble Liquids  

NASA Astrophysics Data System (ADS)

Scintillation efficiency of low-energy nuclear recoils in noble liquids plays a crucial role in interpreting results from some direct searches for Weakly Interacting Massive Particle (WIMP) dark matter. However, the cause of a reduced scintillation efficiency relative to electronic recoils in noble liquids remains unclear at the moment. We attribute such a reduction of scintillation efficiency to two major mechanisms: 1) energy loss and 2) scintillation quenching. The former is commonly described by Lindhard's theory and the latter by Birk's saturation law. We propose to combine these two to explain the observed reduction of scintillation yield for nuclear recoils in noble liquids. Birk's constants kB for argon, neon and xenon determined from existing data are used to predict noble liquid scintillator's response to low-energy nuclear recoils and low-energy electrons. We find that energy loss due to nuclear stopping power that contributes little to ionization and excitation is the dominant reduction mechanism in scintillation efficiency for nuclear recoils, but that significant additional quenching results from the nonlinear response of scintillation to the ionization density.

Mei, Dongming; Yin, Zhongbao; Stonehill, Laura; Hime, Andrew

2008-10-01

394

A model of nuclear recoil scintillation efficiency in noble liquids  

NASA Astrophysics Data System (ADS)

Scintillation efficiency of low-energy nuclear recoils in noble liquids plays a crucial role in interpreting results from some direct searches for weakly interacting massive particle (WIMP) dark matter. However, the cause of a reduced scintillation efficiency relative to electronic recoils in noble liquids remains unclear at the moment. We attribute such a reduction of scintillation efficiency to two major mechanisms: (1) energy loss and (2) scintillation quenching. The former is commonly described by Lindhard's theory and the latter by Birk's saturation law. We propose to combine these two to explain the observed reduction of scintillation yield for nuclear recoils in noble liquids. Birk's constants kB for argon, neon and xenon determined from experimental data are used to predict noble liquid scintillator's response to low-energy nuclear recoils and low-energy electrons. We find that energy loss due to nuclear stopping power that contributes little to ionization and excitation is the dominant reduction mechanism in scintillation efficiency for nuclear recoils, but that significant additional quenching results from the nonlinear response of scintillation to the ionization density.

Mei, D.-M.; Yin, Z.-B.; Stonehill, L. C.; Hime, A.

2008-08-01

395

NOBLE DOLLHOUSES, VIOLENT SHOOTER GAMES: REALITY, ABSTRACTION AND SHIFTING PERSPECTIVES  

Microsoft Academic Search

Dollhouses and shooter games provoke opposing associations: The cute world of the dollhouse versus the brutal realm of the shooter game. In a workshop, I combined the two and asked the participants to collaboratively design a dollhouse level for the shooter game Unreal Tournament. Dollhouses originally came into existence as beautifully crafted miniaturisations of noble households. A dollhouse offers a

Maia Engeli