Noble Gases Ne Research Articles

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

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 ( fO 2) of IW + 0.9 (i.e., 0.9 log units higher than the iron-wüstite buffer) and the other at high pressures ( P total ∼ 2 × 10 8 Pa), 1500°C and fO 2 ∼ IW + 6. For the former experiment, isotopically labeled-nitrogen ( 15N 15N-enriched) was used to distinguish dissolved nitrogen from contaminating atmospheric or organic nitrogen and to examine dissolution mechanisms of nitrogen in silicate melts. The results obtained for the two series of experiments are consistent with each other, suggesting that Henry's law is satisfied for fN 2 of up to ∼250 atm (2.5 × 10 7 Pa). The results are also consistent with our earlier results (Miyazaki et al., 1995) obtained at highly oxidizing conditions ( fO 2 ∼ IW + 10). All these results support physical dissolution of nitrogen as N 2 molecules in silicate melts for fO 2 from ∼IW + 10 down to ∼IW. The observed solubility (Henry's constant) of nitrogen (3–5 × 10 −9 mol/g/atm) is comparable to that of Ar (2–4 × 10 −9 mol/g/atm), and much lower than that of Ne (11–14 × 10 −9 mol/g/atm) at 1300°C. A preliminary experiment was also performed for partitioning of nitrogen and noble gases between clinopyroxene (cpx) and basaltic melt using a piston cylinder-type apparatus at 1.5 GPa and at 1270 to 1350°C. The obtained cpx/melt partition coefficient of nitrogen is 0.06, slightly lower than those of noble gases (∼0.1 for Ne to Xe), suggesting that nitrogen is as incompatible as or even slightly more incompatible than noble gases. The present results imply that a large nitrogen/Ar fractionation would not be produced by magmatic processes. Therefore, the two orders of magnitude difference between the N 2/ 36Ar ratios in the Earth's atmosphere (∼10 4) and that in the mantle (∼10 6) must be explained by some other processes, such as incomplete segregation of metal blobs into the core and their later oxidation.

Construction of I-Xe and 40Ar-39Ar Dating System Using a Modified VG3600 Mass Spectrometer and the First I-Xe Data Obtained in Japan

Improvements in ion collectors of the VG3600 mass spectrometer used for 40Ar-39Ar dating in the Radioisotope Center, University of Tokyo, have been performed. We also constructed a new compact vacuum line for extraction and purification of noble gases, and connected it to the mass spectrometer. The new noble gas mass spectrometry system enables us to measure all noble gases (He, Ne, Ar, Kr, and Xe) at low detection limits corresponding to 2×10-15 cm3 STP or 5×103 atoms of Kr and Xe. A newly designed W-coil furnace effectively heats small samples (1-100 mg) in a Mo-crucible with condition of low blank levels (10-10 and 10-15 cm3 STP for Ar and Xe). Smaller sample sizes required for 40Ar-39Ar dating have reduced activity levels. The system was preliminarily applied to I-Xe dating of neutron irradiated meteorites, Bjurbole, Allende and Yamato-74191, and discovered a late formation age of Yamato-74191 (26 Ma after Bjurbole) compared with the Allende meteorite.

Noble gases in the lunar regolith

The most fundamental character of lunar soil is its high concentrations of solar-wind-implanted elements, and the concentrations and behavior of the noble gases He, Ne, Ar, and Xe, which provide unique and extensive information about a broad range of fundamental problems. In this paper, the authors studied the forming mechanism of lunar regolith, and proposed that most of the noble gases in lunar regolith come from the solar wind. Meteoroid bombardment controls the maturity of lunar soil, with the degree of maturation decreasing with grain size ; the concentrations of the noble gases would be of slight variation with the depth of lunar soil but tend to decrease with grain size. In addition, the concentrations of noble gases in lunar soil also show a close relationship with its mineral and chemical compositions. The utilization prospects of the noble gas3He in lunar regolith will be further discussed.

Perturbational ab initio calculations of relativistic contributions to nuclear magnetic resonance shielding tensors

We present perturbational ab initio calculations of the leading-order one-electron relativistic contributions to the nuclear magnetic resonance shielding tensor based on the Pauli Hamiltonian. The scalar relativistic and spin–orbit interaction effects, including both relativistic corrections to the wave function (“passive” relativistic effects) and relativistic magnetic perturbation operators (“active” effects), are considered for H2X (X=O, S, Se, Te, Po), HX (X=F, Cl, Br, I, At), and noble gas (Ne, Ar, Kr, Xe, Rn) systems. The perturbational corrections are calculated using linear and quadratic response theory applied to nonrelativistic reference states. We use the uncorrelated self-consistent field as well as correlated, multiconfigurational complete active space self-consistent field models. Results for the 1H and heavy-atom shielding constants and anisotropies are compared with Dirac–Hartree–Fock and quasirelativistic data.

D. Porcelli, C.J. Ballentine and R. Wieler (Eds) Noble Gases in Geochemistry and Cosmochemistry. Reviews in Mineralogy and Geochemistry, 47 . Washington, D.C. (Mineralogical Society of America and the Geochemical Society) 2002. 844 pp. Price US $40. ISBN 0 939950 59 6.

Noble gas (He, Ne, Ar, Xe, and Kr) data are currently realizing their potential to provide information concerning the processes involved in the formation and evolution of the Earth and solar system. However, as Alex Haliday points out in his foreword to this volume, the technical difficulties in acquiring noble gas data are only matched by the complexity of the noble gas systematics involved in data interpretation. Therefore, dedicated analytical facilities available to obtain noble gas analyses are relatively few and require specialists both in instrument development and in Earth and planetary processes to overcome the problems involved in producing authoritative data. For the potential role of noble gases in interpretative geochemistry to be fully realized will require the spreading of the noble gas gospel to …

Solubility of Gases in Binary Liquid Mixtures: An Experimental and Theoretical Study of the System Noble Gas + Trifluoroethanol + Water

Solubilities of noble gases (He, Ne, Ar, Kr, and Xe) in mixtures of water + 2,2,2-trifluoroethanol (TFE) at 298.15 K and 101.33 kPa partial pressure of gas are reported. The procedure for the estimation of these solubilities from the experimental data is described in detail. From these data, the Henry's constants at the vapor pressure of water (the least volatile component), the standard changes in the Gibbs energy for both the solution process and the solvation process, and the so-called excess Henry's constant are calculated. Finally, three prediction methods are applied, and their results are compared and discussed.

Steady-state surface stress induced in noble gas sputtering

We have measured the surface stress on single crystal Cu(100) surfaces as induced by bombardment of the surface with the noble gas ions Ar, Ne and He at room temperature. Regardless of the ion type and energy, the induced stress is compressive and saturates as a function of sputter time at a value between 2 and 15 N/m. Saturation time and magnitude of the induced stress depend on the ion species and their energy. The time dependence can be accounted for by assuming a steady state thickness of a defective surface layer, which arises from a balance between sputtering and ion implantation.

TargetZdependence and additivity of cross sections for electron loss by 6-MeV/amuXe18+projectiles

The dependence of electron loss by 6-MeV/amu ${\mathrm{Xe}}^{18+}$ on target atomic number was investigated by measuring single-collision cross sections for loss of one to eight electrons in targets of the noble gases He, Ne, Ar, Kr, and Xe. The total-electron-loss cross sections were found to increase linearly with target atomic number, but an abrupt slope change was observed to occur between Ne and Kr. Calculated total-loss cross sections obtained using the n-body classical trajectory Monte Carlo method were in good agreement with the measurements. The dependence of the individual cross sections on the number of electrons lost was reasonably well represented by a semiempirical fitting procedure utilizing the independent-electron approximation. Additional measurements performed with a variety of molecular targets provided a rigorous test of cross-section additivity. It was found that the additivity rule works well in this collision regime and that the molecular nature of the target has remarkably little influence on the cross sections.

Cosmogenic nuclides in the Brenham pallasite

Abstract— Cosmic‐ray‐produced (cosmogenic) nuclides were studied in fragments of the Brenham pallasite, a large stony iron meteorite. The contents of light noble gases (He, Ne, and Ar) and long‐lived radionuclides (10Be, 26Al, 36Cl, and 53Mn), produced by nuclear reactions with cosmic rays, were measured in the separated metal and olivine phases from numerous samples representing a wide range of shielding conditions in the meteoroid. The distribution of cosmogenic nuclide concentrations in the metal follows patterns similar to that observed in large iron meteorites. Shielding effects were estimated from the relative proportions of low‐ and high‐energy reaction products. The production rates varied, from surface to interior, by a factor of more than several hundred. The 36Cl‐36Ar cosmic‐ray exposure age of Brenham is 156 ± 8 Myr. This determination is based on a multiple nuclide approach that utilizes cosmogenic nuclide pairs. This approach not only yields a “shielding independent” exposure age but also demonstrates that the production of cosmogenic nuclides occurred in a single stage. The depth profiles of 10Be in the stone phase and 53Mn in the metal phase are shown superimposed on corresponding profiles from the Apollo 15 long drill core.Surprisingly low abundances of lithophile elements, such as K, U, and Th, provided a unique opportunity to examine the production systematics of those nuclides whose inventories typically have significant contributions from non‐cosmogenic sources, particularly radiogenic contributions. The U and Th contents of the olivine samples are extremely low, allowing detection of cosmogenic 4He production from oxygen, magnesium, silicon, and iron.

Calculation of electron-impact total-ionization cross sections

A computationally efficient analytic form of the Born-approximation electron-impact ionization amplitude is derived for general neutral-atom targets. High-quality Hartree-Fock Slater orbitals are used to model the target wave function. Full orthogonalization of the continuum Coulomb wave to all occupied orbitals of the target atom is enforced. Results are presented for noble gases (Ne, Ar, Kr, and Xe), selected transition metals (Fe, Cu, and Ag), and elements from the fourth, fifth, and sixth columns of the periodic table (Si, Ge, Sn, P, As, Sb, S, Se, and Te), where theoretical comparisons are lacking. Full orthogonalization significantly improves agreement with experimental data for the noble-gas series compared to previous Born models. Overall agreement with all elements is uniformly good and variations within each series are systematic.

Noble gas compositions of Antarctic micrometeorites collected at the Dome Fuji Station in 1996 and 1997

Abstract— The noble gases He, Ne, Ar, Kr, and Xe were measured in 27 individual Antarctic micrometeorites (AMMs) in the size range 60 to 250 μm that were collected at the Dome Fuji Station. Eleven of the AMMs were collected in 1996 (F96 series) and 16 were collected in 1997 (F97 series). One of the F97 AMMs is a totally melted spherule, whereas all other particles are irregular in shape. Noble gases were extracted using a Nd‐YAG continuous wave laser with an output power of 2.5‐3.5 W for ˜5 min. Most particles released measurable amounts of noble gases. 3He/4He ratios are determined for 26 AMMs ((0.85‐9.65) × 10−4). Solar energetic particles (SEP) are the dominant source of helium in most AMMs rather than solar wind (SW) and cosmogenic He. Three samples had higher 3He/4He ratios compared to that of SW, showing the presence of spallogenic 3He. The Ne isotopic composition of most AMMs resembled that of SEP as in the case of helium. Spallogenic 21Ne was detected in three samples, two of which had extremely long cosmic‐ray exposure ages (> 100 Ma), calculated by assuming solar cosmic‐ray (SCR) + galactic cosmic‐ray (GCR) production. These two particles may have come to Earth directly from the Kuiper Belt. Most AMMs had negligible amounts of cosmogenic 21 Ne and exposure ages of <1 Ma. 40Ar/36Ar ratios for all particles (3.9–289) were lower than that of the terrestrial atmosphere (296), indicating an extraterrestrial origin of part of the Ar with a very low 40Ar/36Ar ratio plus some atmospheric contamination. Indeed, 40Ar/36Ar ratios for the AMMs are higher than SW, SEP, and Q‐Ar values, which is explained by the presence of atmospheric 40Ar. The average 38Ar/36Ar ratio of 24 AMMs (0.194) is slightly higher than the value of atmospheric or Q‐Ar, suggesting the presence of SEP‐Ar which has a relatively high 38Ar/36Ar ratio. According to the elemental compositions of the heavy noble gases, Dome Fuji AMMs can be classified into three groups: chondritic (eight particles), air‐affected (nine particles), and solar‐affected (eight particles). The eight AMMs classified as chondritic preserve the heavy noble gas composition of primordial trapped component due to lack of atmospheric adsorption and solar implantation. The average of 129Xe/132Xe ratio for the 16 AMMs not affected by atmospheric contamination (1.05) corresponds to the values in matrices of carbonaceous chondrites (˜1.04). One AMM, F96DK038, has high 129Xe/132Xe in excess of this ratio. Our results imply that most Dome Fuji AMMs originally had chondritic heavy noble gas compositions, and carbonaceous chondrite‐like objects are appropriate candidate sources for most AMMs.

High pressure operation of the triple-GEM detector in pure Ne, Ar and Xe

We study the performance of the triple-gas electron multiplier (GEM) detector in pure noble gases Ne, Ar and Xe, at different pressures varying from 1 to 10 atm. In Ar and Xe, the maximum attainable gain of the detector abruptly drops down for pressures exceeding 3 atm. In contrast, the maximum gain in Ne was found to increase with pressure, reaching a value of 10 5 at 7 atm. The results obtained are of particular interest for developing noble gas-based cryogenic particle detectors for solar neutrino and dark matter search.

Fall, classification and cosmogenic records of the Sabrum (LL6) chondrite

Abstract— The petrographic and chemical characteristics of a fresh Indian meteorite fall at Sabrum are described. Its mean mineral composition is defined by olivine (Fa31.4), orthopyroxene (Fs25.1,Wo2.0), clinopyroxene (Wo45En45.6Fs9.4) and plagioclase (An10.6Ab83.6Or5.8). The meteorite shows moderate shock features, which indicate that it belongs to the S4 category. Based on mineralogical and chemical criteria the meteorite is classified as an LL6 brecciated veined chondrite. Several cosmogenic radioisotopes (46Sc, 7Be, 54Mn, 22Na and 26Al), noble gas (He, Ne, Ar, Kr and Xe), nitrogen isotopes, and particle tracks density have been measured. Concentrations of cosmogenic 21Ne and 38Ar indicate that its cosmic‐ray exposure age is 24.8 Ma. Small amounts of trapped Kr and Xe, consistent with petrologic class 5/6, are present. The track density in olivines is found to be (1.3 ± 0.3) × 106/cm2. Activities of most of the short‐lived isotopes are lower than those expected from solar cycle variation. 22Na/26Al (1.12 ± 0.02) is found to be significantly anomalous, being ˜25% lower than expected from the Climax neutron monitor data. These results indicate that the cosmic‐ray flux during the terminal segment of the meteoroid orbit was low. The activities of 26Al and 60Co and the track density indicate small meteoroid size with a radius ˜15 cm.

Precompaction exposure of chondrules and implications

Following the discovery of an apparent precompaction irradiation of a chondrule, we studied the isotopic abundances of noble gases He, Ne, and Ar in separated chondrule and matrix samples of eight ordinary chondrites. The chondrules show systematically larger concentrations of cosmogenic He, Ne, and with one exception, Ar when compared to the corresponding matrix samples. Different exposure times were calculated based on production rates, which take into account the abundances of relevant target elements in each chondrule and matrix sample. The 81Kr-Kr method was used for samples of Bjurböle to verify that different exposure times are not due to either a bias in production rates or to systematic losses of noble gases from matrix. This method self-corrects for variable shielding, is independent of calculated production rates, and insensitive to gas loss. The results show that differences in exposure ages are due to different precompaction exposures of chondrules, or components thereof, before final assembly of the meteorite. For the Sena chondrite we studied various chondrule and matrix constituents. For this meteorite we found chondrule preexposures relative to the matrix material, with magnetic chondrules showing the largest effect.

Influence of stress on the electron core level energies of noble gases implanted in hard amorphous carbon films

In this work, we report the influence of the structural properties of the amorphous carbon matrix on the core-level electrons of implanted noble gases (Ar, Ne and Kr) used in the sputtering deposition process. The films were prepared in an ion beam-assisted deposition chamber (IBAD) including two Kauffman ion sources. Some fractional noble gas is trapped in the film during the assisted deposition and is subjected to the highly strained environment of the carbon matrix. X-Ray photoelectron spectroscopy shows that the noble-gas core-level energies shift linearly to lower binding energies with increasing compressive stress. It is suggested that these shifts are caused by compression of the outer valence wave-function of the implanted gas and by an extra-screening effect from valence electrons of the host atoms. The use of noble-gas core-level energy is proposed as a probe to determine the film stress.

Analytical Formulae for Total Cross Sections for Electron Scattering by Atoms (N, O, F, Ne, P, S, Cl, Ar, As, Se, Br, Kr) Between 0.5–10 keV

Analytical formulae for total cross sections for electron scattering by atoms which are close to the noble gases (Ne, Ar and Kr), for electron energies ranging from 0.5 to 10 keV, have been obtained in this study. We have shown, previously, that molecular total cross sections, at these energies, depend on target polarizability and the number of target electrons. A similar behaviour has been supposed for total cross sections of some atoms (N, O, F, P, S, Cl, As, Se and Br). The obtained expression depends on atomic parameters and it is based in some correlation derived from noble gases. The applicability of the formula has been checked by comparison with available data for atomic oxygen.

Dynamic changes in hydrogeochemical conditions caused by tunnel excavation at the Aspo Hard Rock Laboratory (HRL), Sweden

Hydraulic changes caused by tunneling at the Aspo Hard Rock Laboratory (HRL) in Sweden have been investigated over a period of 2a using different hydrochemical approaches, i.e. noble gas content, isotopic measurements and major ion concentrations. The dissolved noble gases ( 4He and Ne contents, and the ratio of 3He/ 4He, 40Ar/ 36Ar), stable isotopes, chemical concentrations of major ions, and 36Cl/Cl ratios, were determined in groundwater samples collected in the tunnel from borehole sections isolated by inflated packers. Groundwater was categorized into 3 groups based on 4He and Cl − contents: undisturbed groundwater (i.e. prior to tunnel construction) with high 4He and Cl − contents, groundwater that has been gradually changed by mixing with Baltic seawater and whose 4He and Cl − contents have gradually increased with increasing depth, and groundwater that has been totally changed due to a rapid mixing of Baltic seawater and/or shallow groundwater and whose 4He and Cl − contents are extremely low compared with other samples collected at the same surrounding depth. The oldest groundwater with a high salinity of more than 14,000 mg l −1 of Cl − is estimated to be more than 1.8 Ma old. The groundwater residence time ranges from 0.9 to 900 Ka in the mixing-zone. Groundwater in the disturbed zone where rapid mixing has occurred is hard to date reliably and its primary hydrochemical character has already been lost.

Analysis of dislocation mechanism for melting of elements: Pressure dependence

In the framework of melting as a dislocation-mediated phase transition we derive an equation for the pressure dependence of the melting temperatures of the elements valid up to pressures of order their ambient bulk moduli. Melting curves are calculated for Al, Mg, Ni, Pb, the iron group (Fe, Ru, Os), the chromium group (Cr, Mo, W), the copper group (Cu, Ag, Au), noble gases (Ne, Ar, Kr, Xe, Rn), and six actinides (Am, Cm, Np, Pa, Th, U). These calculated melting curves are in good agreement with existing data. We also discuss the apparent equivalence of our melting relation and the Lindemann criterion, and the lack of the rigorous proof of their equivalence. We show that the would-be mathematical equivalence of both formulas must manifest itself in a new relation between the Grüneisen constant, bulk and shear moduli, and the pressure derivative of the shear modulus.

Exposure history of the Mocs (L6) chondrite: A study of strewn field samples

Abstract— We measured cosmogenic radionuclides (10Be, 26Al, and 36Cl) and noble gases (He, Ne, and Ar) in 10 specimens of the Mocs L6 chondrite to determine the exposure history and preatmospheric relationship among fragments from known locations in the strewn field. Cosmogenic noble gas contents alone are consistent with a simple irradiation exposure of 15.2 Ma. However, Mocs has very low 22Ne/21Ne ratios indicative of deep burial in a large meteoroid, but radionuclide levels at saturation values typical for much smaller meteoroids: this paradox suggests a possible complex exposure. For the latter case, we propose a two‐stage exposure history in which Mocs initially was deeply buried in a large object for 110 Ma, followed by exposure in a 65 cm object for 10.5 Ma. Relative shielding was inferred from the measured 22Ne/21Ne ratios assuming constant 22Ne/21Ne production for all samples during the first stage. These shielding levels, which are supported by estimates based on 36Cl production by neutron capture, indicate a possible relationship between depth of samples in the Mocs meteoroid and fall location in the strewn field.

Evidence for common breakup events of the acapulcoites‐lodranites and chondrites

Abstract— Acapulcoites and lodranites are believed to originate on a common parent body and to represent some of the earliest events in the differentiation of the chondritic asteroids. We have conducted isotopic studies of the noble gases He, Ne, Ar, Kr, and Xe, and determinations of the concentrations of the major elements and of the radionuclides 10Be, 26Al, and 36Cl in an attempt to constrain the cosmic‐ray exposure history of two members of the acapulcoite‐lodranite clan recovered in Antarctica: Frontier Mountain (FRO) 95029 and Graves Nunataks (GRA) 95209. From cosmic‐ray‐produced 3He, 21Ne, and 38Ar and appropriate production rates, we derive parent‐body breakup times of 4.59 ± 0.60 and 6.82 ± 0.60 Ma for FOR 95029 and GRA 95209, respectively. These times are consistent with those obtained from the pairs 10Be‐21Ne and 26Al‐21Ne; whereas the times inferred from the pair 36Cl‐36Ar are slightly longer, perhaps because the 36Cl activities decreased as a result of decay on Earth. Terrestrial ages up to ∼50 ka for the two meteorites are consistent with the measured 36Cl activities of the metal phases. All acapulcoites and lodranites dated until now show cosmic‐ray exposure ages in the range of 4–10 Ma. This is the same range as that found for the major exposure age cluster of the H chondrites. As a common parent body is improbable on the basis of the O‐isotopic systematics, a common set of impactors might have affected the asteroid belt 4–10 Ma ago.