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Noble gases are ideal natural tracers to characterize the storage, migration and origin of fluids in geological environments. They are chemically and biologically inert and therefore are only partially separated by physical processes including the one related to the molecular diffusion phenomenon, so called kinetic fractionation. However, its precise quantification is difficult to achieve and its modeling is still open for debates. Thus, in this work, we have investigated the capability of simple and predictive models to estimate elemental and isotopic fractionation of noble gases in various geological fluids. To do so, molecular dynamics simulations on noble gases in water, gas and oil under sub-surface conditions were performed. These numerical results were found to be consistent with previous ones including experiments and molecular simulations when available, i.e. in water. Interestingly, it appeared that the widely used square-root law is able to provide a good prediction for elemental fractionation between noble gases in all solvents, except for helium. Such unexpected result from the theoretical point of view is explained by a peculiar relationship between the molecular mass and the molecular size of noble gas elements. Regarding the noble gas isotopic fractionation, the square-root law is shown to be unable to provide reasonable results, confirming recent experimental and numerical works. As expected, it has been noticed that the kinetic theory relation provides a reasonable estimate of the isotopic fractionation in gas whereas it deteriorates in water and in oil. Finally, using the previous findings, we propose a simple and predictive scheme for the isotopic fractionation of noble gases in all studied geo-fluids which is noticeably better than both the square-root and the kinetic theory relations.

We report detailed characterizations of the petrology, mineralogy, and noble gas signatures of Renazzo-type (CR) chondrites EET 92048, MIL 090657, NWA 801, and hydrothermally treated MIL 090657 samples to investigate primordial noble gases hosted by water-susceptible materials in aqueously less-altered CR chondrites. The noble gases were extracted by a stepwise heating method. The hydrothermal treatment on MIL 090657 resulted in the alteration of amorphous silicates in the matrix and the removal of large amounts of He and Ne that were released at low temperature from the untreated sample. The 36Ar/132Xe ratios in EET 92048 and MIL 090657 are ~5 times higher than that of the Q noble gas component, although both meteorites do not show any evidence for solar wind noble gases. The analyses revealed that aqueously less-altered CR chondrites contain two distinct primordial noble gas components hosted by water-susceptible materials: an isotopically Q-like Ne-rich component and an Ar-rich component. The characteristics of the Q-like Ne-rich component are consistent with those of Q-like Ne in cometary materials. We propose that the CR chondrites formed at a greater heliocentric distance and share similar materials hosting the Q-like Ne-rich component with comets. The presence of the Ar-rich component in the CR chondrites, as well as in ordinary chondrites and other anhydrous carbonaceous chondrites, provides evidence of the global distribution of the Ar-rich carriers in the ordinary and carbonaceous chondrite forming regions.

129Xe NMR has been proven to be a powerful tool to investigate the structure of porous materials. Xenon is a monatomic noble gas which could be used as a probe due to the extremely sensitive to its local environment. Optical pumping techniques for production of hyperpolarized (HP) xenon have led to an increase of sensitivity up to orders of magnitude compared with traditional 129Xe NMR. This review summarizes the application of this technique in porous materials and heterogeneous catalysis in recent ten years, involving of zeolites, metal-organic frameworks (MOFs), catalytic process and kinetics.

The article provides a review of the research results obtained during of more than 20 years concerning using the gaseous radiochemical method (GRCM) for detecting of ionizing radiation. This method based on threshold nuclear reactions with production of radioactive noble gas which does not interact with the materials of gaseous tract. The applications of GRCM in the diagnostics of neutrinos, neutrons, charged particles, thermonuclear plasma thermometry, and the study of the structure and dynamics of astrophysical objects, position-sensitive dosimetry of neutron targets with accelerator driving, spatial distribution of the fast neutron flux density in a nuclear reactor allowing the transformation of longitudinal coordinate of neutron flux distribution into a temporal distribution of the radiochemical gas decay counting rate (“barcode” semblance) and measurement of bombarding particles spectra are described. Experimental testing of the described technologies was made on the neutron target driven with the linear proton accelerator of Institute for Nuclear Research of Russian Academy of Sciences (INR RAS).

Heavy noble gas (Ne, Ar, Xe) isotopic compositions provide powerful constraints on the nature of mantle heterogeneities. The North Atlantic popping rock sample 2ΠD43 is unusually gas-rich and has long formed the basis of our understanding of the noble gas composition of the mid-ocean ridge basalt (MORB) mantle source. Here we present new high-precision He, Ne, Ar and Xe isotopic compositions as well as He, Ne, Ar and Xe abundances measured in a split of the 2ΠD43 sample. After correcting the measured values for syn- to post-eruptive atmospheric contamination, we estimate a mantle source 21Ne/22Ne of 0.0590 ± 0.0002, 40Ar/36Ar of 23,900 ± 100 and 129Xe/130Xe of 7.41 ± 0.02 for 2ΠD43. Significant regassing of atmospheric Xe into the North Atlantic popping rock mantle source is evident, though differential regassing cannot explain systematic variations between MORB and plume-derived signatures. Rather, the fissiogenic Xe isotope signature of the 2ΠD43 mantle source indicates a greater extent of long-term degassing of the upper mantle relative to the plume mantle to explain heavy noble gas isotopic variations. The popping rock data also add to growing evidence that the MORB mantle differentiated from the reservoir supplying noble gases to plume sources within the first 100 Myr of Earth history, and that the two reservoirs have not been homogenized though 4.45 Ga of mantle convection.

Subduction of atmospheric noble gases has been considered to play an important role in altering the primordial isotopes of Earth’s mantle over geological time. Analysis of natural samples and experiments indicate that large quantities of noble gases can be dissolved in volatile-bearing hydrous minerals in the subduction slabs. To quantitatively investigate the recycling efficiency of noble gases and relevant consequences on the mantle noble gas isotopic evolution, the diffusivities of noble gases in these minerals are needed. In this study, diffusion of He, Ne, Ar, Kr and Xe in lizardite, antigorite and tremolite have been calculated by first-principles methods based on density functional theory. Our results disclose that diffusion is slower with increasing radius of the noble gas atom (DHe > DNe > DAr > DKr > DXe) as expected. The common ring-structures in hydrous silicate minerals provide incorporation sites for the noble gas atoms and control their mobility. The diffusion activation energies are 84.9, 157.3, 287.5, 347.4, 414.9 kJ/mol from He to Xe in lizardite, and despite the very similar lattice structure between lizardite and antigorite, the activation energies are found to be significantly higher in antigorite, which are 120.6, 267.3, 449.6, 497.9 and 550.0 kJ/mol, respectively. In tremolite, the energy barriers are 93.6, 158.2, 266.3, 322.2 and 385.0 kJ/mol, which are also found to be in very good agreement with available experimental values and similar to those in lizardite. We also calculated diffusion activation energies at higher pressures (1 GPa for liazardite, 3 GPa for antigorite and tremolite) to better understand how much noble gases can be preserved against diffusive loss during subduction. Our result show that the oceanic crust and the lithospheric mantle of the subduction slab play different roles in delivering noble gases into the mantle. We find that all Ar, Kr, Xe and possibly part of the Ne can be entrained by the serpentine-dominated lithospheric mantle into the deep mantle due to the high diffusive energy barriers in antigorite. In contrast, noble gases in the amphibole-enriched oceanic crust would be characterized by fractionated noble gas signature, with the concentrations of retained noble gases in the crust following their respective ionic radius (Ne

Understanding microstructural and strain evolutions induced by noble gas production in the nuclear fuel matrix or plasma-facing materials is crucial for designing next generation nuclear reactors, as they are responsible for volumetric swelling and catastrophic failure. We describe a multimodal approach combining synchrotron-based nanoscale X-ray imaging techniques with atomic-scale electron microscopy techniques for mapping chemical composition, morphology and lattice distortion in a single crystal W induced by Kr irradiation. We report that Kr-irradiated single crystal W undergoes surface deformation, forming Kr containing cavities. Furthermore, positive strain fields are observed in Kr-irradiated regions, which lead to compression of underlying W matrix.

The luminescence spectra for noble gases and their binary mixtures excited by Ar ions with energies up to 70 MeV were examined in the range of 200–980 nm. The emissions at the transitions of heteronuclear ionic molecules ArXe+, ArKr+, KrXe+ were studied for a gas-mixture, with a wide variation in the percentage composition. The noble gases atomic spectra are dominated by lines of (n + 1)p-(n + 1)s-transitions (2p-1s in Pashen’s notation); lines of d-(n + 1)p-transitions were also observed. The distribution of radiation over 2p-levels of noble gas atoms was also measured. The sharp predominance of the fraction of radiation from the levels 2p2 of Ar, 2p6 of Kr and 2p5 of Xe is partially explained by the relatively small values of the rate constants for the deactivation of these levels, by own atoms. The mechanisms of levels population under the excitation of noble gases by ionizing radiation are discussed.

The Karamaili ophiolite belt is an important tectonic unit in the East Junggar terrane, Xinjiang, China, and provides a material basis for the study of subduction, accretion and collision processes, regional tectonic evolution, and the exploration of oil (gas) reservoirs in the western part of the Central Asian Orogenic Belt (CAOB). In the late Paleozoic, an important tectonic transition from subduction to post–collisional extension occurred in the East Junggar terrane; however, the precise timing of the tectonic transition is still a matter of debate. The volcanic rocks in the Karamaili area, predominately rhyolite and basalt–andesite, are typical post–collisional volcanic rocks and thus provide important constraints on the tectonic setting of the East Junggar. Here, zircon U–Pb geochronology and He–Ne–Ar and Sr–Nd–Pb isotopic analyses were carried out on volcanic rocks from three localities in the Karamaili area. Four zircon U–Pb ages indicate that magmatism occurred in the Carboniferous at 335–310 Ma, which is interpreted as the age of post–collisional extension events. The 4He–3He/4He isotopic ratios of these samples are similar to those of the continental crust and show a weak contribution of mantle He, indicating the presence of mantle He in the orogenic belt. The 20Ne/22Ne, 21Ne/22Ne, and R/Ra–40Ar/36Ar ratios show that the air-like Ne and Ar are derived from dissolved atmospheric and continental crust sources in the subducted supracrustal rocks. Meanwhile, relatively low 87Sr/86Sr ratios of andesite and basalt (0.704–0.707) and high eNd(t) values (4.73–7.22) reveal the presence of depleted mantle components in their source regions. The heterogeneous isotopic signatures of the volcanic rocks in the East Junggar indicate that they formed via different processes or in multiphase settings, suggesting a significant tectonic transition from an island arc setting to a post-collisional extension regime during the Carboniferous period.

The migration of hydrocarbons from source-rock to reservoir is a critical stage in petroleum system evolution. However, as migration occurs along confined pathways over geologically rapid timescales it is challenging to place quantitative constraints on migration behaviour in terms of interaction with other basinal fluids, flux, and lengthscales associated with this process. Due to their inert nature, noble gases are ideal tracers of fluid provenance and physical processes in a variety of subsurface systems, and thus can serve as a potential geochemical indicator of migration distance. The recent proliferation of unconventional hydrocarbon production (i.e., production directly from source-rocks) allows for the analysis of fluids from these strata. Here we present noble gas data from natural gas samples produced from 27 related conventional and unconventional wells within the East Texas basin. These data enable characterisation of fluids during migration from source-rock to conventional reservoir. Unconventional gases and fluids are produced from the Haynesville shale (n = 8), and conventional gases and fluids are sourced from the overlying Cotton Valley (n = 5), Travis Peak (n = 9), and James Lime (n = 5) formations. Samples consist primarily of methane (>70%), with small contributions from longer-chain hydrocarbons, and other gases including CO2 and N2. Atmosphere-derived 36Ar, which is introduced into natural gas accumulations via interaction with groundwater during hydrocarbon generation and migration, is consistently higher in samples that have undergone a greater migration distance from the source interval. Thus, calculated volume ratios of gas-water interaction (Vg/Vw) show a far greater incidence of groundwater interaction in migrated samples. Radiogenically-produced 40Ar is also consistently elevated in migrated samples, despite these reservoirs being located in geologically younger strata. We derive the representative volume of rock required to produce the observed radiogenic 40Ar in each sample and show that samples that have migrated further have acquired radiogenic isotopes from larger volumes of rock. Furthermore, our volumetric parameters derived from atmospheric and radiogenic isotopes are consistent with a simple conceptual model of migration. We quantitatively apply this model to demonstrate that migration occurs along relatively localised pathways. Helium (3He/4He) and argon (40Ar/36Ar) isotopes are correlated and show elevated amounts of mantle-derived 3He and radiogenic 40Ar in migrated samples. We interpret this to represent mixing between a pristine source-rock signature and an endmember characterised by elevated 3He/4He and 40Ar/36Ar, likely representative of mantle-enriched groundwater circulating in the wider hydrogeological basin. Finally, we use an advection-diffusion model to show that enriched mantle 3He in the shallower strata and towards the southern edge of the basin can be explained by influx of mantle helium along the fault-bounded southern edge of the basin over timescales of millions of years. Together these approaches represent the first complete noble gas based characterization of a hydrocarbon system, sampling migration from source-rock to trap. We show conclusively that both atmospheric and radiogenic noble gases are entrained in the hydrocarbon phase during migration and that concentrations scale proportionally with migration distance, as greater volumes of groundwater and host rock are encountered.

The regularities of surface corrugation of polyacrylonitrile based carbon fibers reinforcing composite KUP-VM has been studied experimentally after high-fluence 30 keV Ne+, 20 and 30 keV Ar+, 30 keV N2+ ion irradiation at target temperatures ranging from 100 to 600 °C. It was found that periodic corrugated structure parameters, such as the angles of the inclination β of the corrugations and their fraction on the fiber surface have strong temperature dependences. The periodicity of corrugations for all used ions slightly decreases with increasing temperature and is of the order of hundreds of nanometers. For neon and argon ions the corrugation inclination angles and the fraction in contrary of nitrogen ions show minima at the temperatures near 400 °C which corresponds to the minimum of radiation-induced dimensional changes in carbon materials. The depth of the minima at 400 °C depends on the competition of the processes of ion-induced plastic deformation of carbon materials and ion bombardment sputtering. For nitrogen ions the inclination angles increase with temperature so that at temperature ∼270 °C they reach maximum values ∼40°, staying at this level at subsequent temperature elevation up to 600 °C. The qualitative difference in the temperature dependences of fiber corrugation for noble gas ions and nitrogen ones is connected to nitrogen chemical activity and the creation of C N bonds under nitrogen ion implantation.

Due to the momentum and energy exchange between the gas and solid surface molecules, by means of the accommodation coefficients in the Cercignani-Lampis-Lord (CLL) model, the velocity components used in the Direct Simulation Monte Carlo (DSMC) method can be studied more accurately. The coefficients can also be used in calculation of slip velocity, temperature jumping, drag force and shear stress. In the light of rising needs for polymers in industrial applications, the scattering behavior of noble gas molecules in their collision with a surface made of diglycidyl ether bisphenol A (DGEBA) epoxy resin, cured by tetrahydrophthalic anhydride (THPA) agent and reinforced by multi-layer graphite, was simulated and investigated by Molecular Dynamics (MD). The momentum and energy accommodation coefficients for gas–surface interactions were also calculated by MD simulation. The results indicated that temperature increase, change in the gas species, reduction in surface roughness, and increase in the Knudsen number ( Kn ) and the wall velocity could cause the accommodation coefficients to be less than one. Based on the scattering kernel of CLL boundary condition, a suitable distribution function for calculating the velocity components of noble gas molecules (e.g., argon molecules) after interaction with polymeric surface was proposed.

We discuss elemental abundances of noble gases in targets exposed to the solar wind (SW) onboard the “Genesis” mission during the three different SW “regimes”: “Slow” (interstream, IS) wind, “Fast” (coronal hole, CH) wind and solar wind related to coronal mass ejections (CME). To this end we first present new Ar, Kr, and Xe elemental abundance data in Si targets sampling the different regimes. We also discuss He, Ne, and Ar elemental and isotopic abundances obtained on Genesis regime targets partly published previously. Average Kr/Ar ratios for all three regimes are identical to each other within their uncertainties of about 1% with one exception: the Fast SW has a 12% lower Xe/Ar ratio than do the other two regimes. In contrast, the He/Ar and Ne/Ar ratios in the CME targets are higher by more than 20% and 10%, respectively, than the corresponding Fast and Slow SW values, which among themselves vary by no more than 2–4%. Earlier observations on lunar samples and Genesis targets sampling bulk SW wind had shown that Xe, with a first ionisation potential (FIP) of ∼12 eV, is enriched by about a factor of two in the bulk solar wind over Ar and Kr compared to photospheric abundances, similar to many “low FIP” elements with a FIP less than ∼10 eV. This behaviour of the “high FIP” element Xe was not easily explained, also because it has a Coulomb drag factor suggesting a relatively inefficient feeding into the SW acceleration region and hence a depletion relative to other high FIP elements such as Kr and Ar. The about 12% lower enrichment of Xe in Genesis’ Fast SW regime observed here is, however, in line with the hypothesis that the depletion of Xe in the SW due to the Coulomb drag effect is overcompensated as a result of the relatively short ionisation time of Xe in the ion-neutral separation region in the solar chromosphere. We will also discuss the rather surprising fact that He and Ne in CME targets are quite substantially enriched (by 20% and 10%, respectively) relative to the other solar wind regimes, but that this enrichment is not accompanied by an isotopic fractionation. The Ne isotopic data in CMEs are consistent with a previous hypothesis that isotopic fractionation in the solar wind is mass-dependent.

Limited reserves and insecure resource supply have led to global shortage crises in helium, a vital gas for cryogenic engineering and other countless industrial manufacturing processes. Despite the attention drawn by global supply disruptions, the helium accumulation mechanism in natural gas fields remains poorly understood. Noble gases are excellent tracers for studying migration and accumulation processes of fluids in the subsurface and can be used to investigate the influence of subsurface fluids on helium accumulation. We present noble gas isotope and abundance data as well as major gas compositional data from 10 producing wells in three gas fields in the North Qaidam Basin, China. Helium is more concentrated in the Mabei and Dongping gas fields (2.06–48.4 × 10−4 cm3 STP/cm3) than in the Niudong gas field (1.15–1.42 × 10−4 cm3 STP/cm3). The helium is mainly radiogenic, with 3He/4He ratios of 0.01–0.05 Ra, where Ra is the atmospheric value of 3He/4He, and lacks significant contribution from the mantle (0.03–0.67%). The noble gases derived from air-saturated water (20Ne, 36Ar, 84Kr and 130Xe) can be explained by an oil-modified groundwater-exsolution model with excess heavy noble gases. The calculated Voil/Vwater and Vgas/Vwater ratios indicate that the Mabei region is the most oil-rich area and the Dongping region has the driest natural gas, which is consistent with the geological context. These ratios further support the fractionation models. The strong linear relationship between 4He and 20Ne (R2 = 0.98) suggested that 4He was dissolved into groundwater before migrating into the oil or gas phase. The initial 4He concentrations in groundwater can accumulate within 0.31–2.78 Myr assuming a 4He flux from the entire crustal section. According to the fractionation model, helium in groundwater partitions into the gas phase when contacting hydrocarbons. The different volume ratios among oil, gas and water during the equilibration process cause much greater variability in the helium concentrations in the gas phase (e.g., 6.08 × 10−4 to 2.01 × 10−3 cm3 STP/cm3 in Mabei) than those in the groundwater phase (e.g. 9.18 × 10−3 to 1.39 × 10−2 cm3 4He STP/cm3 H2O in Mabei). Hydrocarbons play a critical role in helium accumulation and dilution. Helium-rich natural gas fields are characterized by old groundwater systems and moderate hydrocarbon abundance. This study has succeeded in quantitatively assessing the helium accumulation process in natural gas fields in the North Qaidam Basin and revealed that both groundwater and hydrocarbon phases control the helium accumulation in the subsurface environment. This outcome has broad implications for the prediction of hydrocarbon and helium as resources.

The interaction of 2-methyl-1,3-butadiene (isoprene) with a methanol molecule in low-temperature noble gas (Ar, Kr) matrices was investigated using infrared absorption spectroscopy. The spectra were more perplexed than those of the analogous isoprene-H2O complex, and consistent with the complicated potential energy landscape of this complex obtained from quantum chemical calculations. A comparison of vibrational peaks of 1:1 isoprene-CH3OH adducts and the quantum chemical calculations led to the conclusion that the CH3OH molecule in the complex H-bonds to the two unsaturated C C bonds, and that the binding energy of the complex is comparable to that of the C6H6-CH3OH complex. The natural bond orbital analyses revealed that the weak interaction between CH3 group of methanol and π-electrons augment the OH–π H-bonds in these complexes.

International audience; The origin and evolution of terrestrial volatiles is a fundamental question in Earth and planetary sciences. To better address this, it is necessary to estimate the present-day isotopic and elemental composition of volatiles in the mantle, which is difficult because degassing during magma transport to the surface changes the initial elemental composition. However, some basalts are considered to be relatively un-degassed and therefore can be used to determine the concentrations of C, N, H2O and noble gases in the mantle. This is the case of the so-called popping rock sample 2πD43, found near 14 °N on the Mid-Atlantic Ridge in 1985, which has been considered as a reference for upper mantle isotopic and elemental volatile compositions due to its high gas content. Such gas-rich samples have been recovered in only a few places on mid-ocean ridges but are crucial to characterizing the heterogeneities in mantle composition and therefore the cycling of volatiles on Earth. In order to better understand the occurrence of popping rocks, mantle heterogeneities and volatile cycling on Earth, cruise AT33-03 on R/V Atlantis was conducted in 2016 on the Mid-Atlantic Ridge near 14 °N. Popping rocks were found in the same area as sample 2πD43, using the submersible Alvin, and their noble gas compositions were determined by step-crushing and laser ablation. A new anaerobic sampling protocol was tested in an attempt to minimize atmospheric contamination, which is ubiquitous in basaltic glass samples used for noble gas analyses, and to evaluate laser extraction techniques. Preliminary step-crushing results suggest that the new anaerobic sampling protocol reduces atmospheric influence on the noble gas measurements. Comparison with laser ablation data shows that there is still some atmospheric contamination, suggesting that contamination begins on the seafloor. Two groups of samples have been identified based on their noble gas compositions: one group with their highest measured ratios similar to those of sample 2πD43 (20Ne/22Ne of ~ 12.5, 40Ar/36Ar of ~ 27,000), and another group with lower maximum noble gas ratios (20Ne/22Ne of 12.2, 40Ar/36Ar of 16,100) and higher argon concentrations. Based on these results, along with Cl/K and H2O/Ce ratios and preliminary lead, strontium and neodymium isotope data, it is suggested that these two groups of samples reflect separate eruptive events that originated from distinct mantle sources. This provides evidence for upper mantle heterogeneity at small scales and could imply that the mantle source with lower neon and argon isotopic ratios has been more influenced by recycling of atmospheric noble gases.

A geochemical survey of the Las Tres Virgenes geothermal field (LTVGF), Baja California Sur, Mexico, was carried out to determine the origin and evolution of its fluids, along with the influence of injection of local brines, and inhibitors intended to manage carbonate scaling issues. Major and minor cations, Cl, Br, Sr, O, H, and noble gas (He, Ne, Ar, Kr and Xe) isotopes were measured in fluids collected from four production wells, two injection wells, and one fumarole (El Azufre) in 2016 and 2018. Variations in the stable isotopes of water (δD and δ18O) and halogens (δ37Cl, δ81Br) over the years suggest that local brine reinjection might have started to modify the pristine chemistry of the fluids. However, relevant information on the original geothermal fluids has been preserved. The Na/Br and Cl/Br ratios suggest that LTVGF brines are seawater having leached evaporite deposits (halite). These deposits are absent in the area, but were likely present during the Miocene, prior to the breakup of the Gulf of California, suggesting that the saline fluid end-member at the LTVGF could be several million years old. Measured 3He/4He ratios (R) normalized to the atmospheric ratio Ra (= 1.384 × 10−6) plotted against the 4He/20Ne ratios suggest mixing between a mantle fluid with a R/Ra of 6.19, typical of the sub-continental lithospheric mantle and an atmospheric helium component. The R/Ra versus the 132Xe/36Ar ratio normalized to air suggests mixing between a mantle-rich pre-production fluid and air. The source of air appears to be linked to local gravity-controlled flow reinjection which causes the entrapment of air bubbles, leading to a fluid supersaturated in atmospheric noble gases. This pattern suggests that reinjection fluids are impacting the production area.

Studying the initial stages of surface oxidation is of great relevance to understand how oxygen alters the physical and chemical properties at the interface of the host material to the environment and is therefore, crucial for improvement in manifold technological applications. We investigated the influence of surface oxygen on ion spectra recorded for keV noble gas ions backscattered from metal surfaces in low energy ion scattering (LEIS). Initially pure Zn and Ta surfaces, chosen for their well-characterized properties in ion-neutralization in LEIS, have been oxidized and ion spectra for pure and oxidized surfaces have been compared. Oxygen on the surface significantly influences shape and intensity of the backscattered ion spectrum at all energies: for both metal systems, the surface scattered ion yield of the metal is drastically decreasing under oxygen presence. The observed decrease, however, cannot be explained by the reduction in the surface areal density of the metal constituents exclusively. At least for Zn an additional significant change in charge exchange behavior is necessary to explain the observations. In contrast to the generally observed decrease in the yield of ions scattered from the outermost surface, the change in shape and intensity of the reionization background are found to show opposing trends and different energy dependencies for Zn and Ta.

We have determined the concentrations of atmospheric helium, neon, argon, krypton , and xenon in distilled water and seawater equilibrated with moist marine air at one atmosphere over a temperature range from near freezing point to approximately 35 °C and a salinity range of zero to roughly 39.5 PSS78. In all, we made 74 sets of noble gas measurements at 34 distinct temperature and salinity combinations. The experiments included 35 replicate pairs of samples drawn from 35 separate equilibrations, which in turn had three pairs of repeat equilibrations run at close to identical temperatures. We fit the results to an eight-parameter function similar to one commonly used to compute solubility equilibrium concentrations of these gases for environmental waters. Based on an estimate of analytical accuracy, reproducibility of the comparison with secondary atmospheric standards, replicate sample reproducibility, and reproducibility of the repeat equilibrations, we estimate this function to predict equilibrium concentrations at a particular temperature and salinity within this range to overall precisions 0.10% or better. This includes the regression statistics associated with interpolation and analytical errors for fitting the 8-parameter smoothing function. There is an overall systematic uncertainty of 0.15% for all gases, based on our confidence in and experience with the integrity and cross-calibration of our air standards over recent years. Because our methods are calibrated using assumed and explicit atmospheric abundances of these noble gases, any subsequent uncertainties in atmospheric abundances cancel out in the determination, particularly when the oceanographic measurements utilize marine air as a primary standard. Furthermore, measurement at ambient atmospheric abundances avoids any potential co-solvency induced biases introduced by using ~1 atm pure noble gases, as has been done in most previous studies. We compare these determinations to those made by others in the past and find modest but significant systematic differences with those results.

Atmospheric radioactive noble gas radon (Rn-222) originates from soil gas exhaled in the atmospheric surface layer. Radon exhalation rates from soil as well as corresponding meteorological and soil parameters were recorded for two subsequent years. Based on long-term field data, a statistical regression model for the radon exhalation and the most important influencing parameters soil water content, temperature of soil and air, air pressure and autocorrelation of the exhalation rate was established. The fitting result showed that the multivariate model can explain up to 61% of the variation of the exhalation rate. First, the exhalation rate increases up to 80 Bq m(-2) h(-1) with increasing soil water content. Later, at water content N10%, increasing soil wetness suppressed the exhalation rate: at values higher than 24% to approximately one third. The air temperature had a distinct positive effectwhile the soil temperature had a strong negative effect on the exhalation rate, indicating their different influencing-mechanisms on the exhalation. The air pressure was negligible. The lagged values of radon exhalation had to be included in the model, as the variable shows strong autocorrelation. (c) 2018 Elsevier B. V. All rights reserved.

The diffusion of noble gas argon in the near-surface region of rutile TiO2 has been explored with the Temperature Programmed Out-Diffusion (TPOD) method. The Ar atoms were deposited in a several-nanometer-deep layer of the single-crystal TiO2(110) surface by bombardment with 1–5 keV energy Ar ions. Subsequently, in the TPOD experiments this sample was heated at a linear rate and the out-diffusion of argon was monitored with a mass-spectrometer. Surface conditions were probed with Auger Electron Spectroscopy (AES) and Low-Energy Electron Diffraction (LEED). The experimental results were analyzed with the aid of numerical simulations. The measurements showed a dependence of the Ar diffusion rates on the concentration of buried argon and composition of the surface layer. The kinetic parameters of Ar diffusion in pristine rutile TiO2 were estimated as Ea = 104 kJ/mol and D0 = 6 ⋅ 10−9 m2/s. A distinctive diffusion regime, related to the rock salt TiO phase formation, were identified.

Natural gas reserves with 0.3–2 mol% helium are considered as the only viable source for this noble gas. Currently, cryogenic separation is used to extract helium, but it is energy-intensive. While membrane-based separation is a promising alternative, it is still not considered economical. Even for an inorganic/silica membrane with relatively high selectivity and permeance, a multi-stage membrane system with inter-stage compression is required, which necessitates high CAPEX and OPEX. This study proposes a novel process to enhance the selectivity and permeance of an inorganic/silica membrane system to eliminate the costly inter-stage compression. A 16–24% reduction in the CAPEX and 23–57% in the OPEX are achievable for a natural gas feed with 3–5 mol% helium. In contrast, for a 2 mol% helium feed, the OPEX increases by 34%. However, a 30% decrease in the capital cost outweighs the OPEX increase to make the new process more profitable.

Uranium mononitride is a strong candidate for an advanced nuclear fuel. In this work we use density functional theory to model the diffusivity of matrix U atoms, as well as the noble gas (Ng) fission products Kr and Xe, at the atomic scale under three stoichiometric conditions (U-rich, stoichiometric, N-rich). U self-diffusion is found to be dependent on stoichiometry, being largest under N-rich conditions. The U formation entropy significantly affects the U self-diffusion coefficient, indicating that it is necessary to consider the vibrational properties of the system to accurately describe diffusion properties in UN. The calculated Kr and Xe diffusion coefficients from the U vacancy (VU)-assisted mechanism are much larger than by interstitial mechanisms under the three stoichiometric conditions studied. The two mechanisms show opposite stoichiometric dependence, with the former increasing from U-rich to N-rich conditions and the latter decreasing. Kr moves significantly more quickly than Xe via the interstitial mechanism due to the larger atomic radius of the latter, while the effect of atomic size on the VU-assisted mechanism is negligible, indicating similar diffusivity of Kr and Xe in UN. The good agreement with experiment of our calculated Xe monovacancy-assisted diffusion coefficient indicates that the monovacancy-assisted mechanism governs the Ng diffusion in UN, and supports the accuracy of our theoretical model.

To design monitoring schemes for CO2 storage sites, the composition of the injected CO2 needs to be characterized. Noble gases are one of the environmental tracers, which could be cost-effective since they are naturally inherent in the CO2 and the storage reservoir fluids. The elemental, e.g. He/Ne, He/CO2, or isotopic, e.g. 3He/4He ratios of a gas are potentially diagnostic fingerprints which can be used to discriminate gas sources in the environment, e.g. deep crustal versus shallow, biogenic gas. The waste-to-energy (WtE) plant Klemetsrud, which generates 460000 tCO2/a, was investigated as a future source of captured CO2 for storage in the up-coming large-scale CCS project ‘Longship’, in Norway, aimed to be operational by 2024. In 2019, a demonstration capture facility at the WtE plant was set up to establish the feasibility of future large-scale CO2 capture. We sampled the main gas streams on-site and present the analysis of noble gases in (I) the exhaust of the waste incineration, i.e. the flue gas stream with high concentrations of CO2, (II) the capture outlet, i.e. the CO2-depleted gas stream and (III) the captured, concentrated CO2 gas stream. Noble gas concentrations are depleted in the captured CO2 after the amine treatment by several orders of magnitude compared to the flue gas. Isotopic ratios are air-like. This behavior has been observed at other CO2 capture plants. However, absolute concentrations of noble gases measured at Klemetsrud are significantly lower for all species, except He, which is within the range of previously measured concentrations. Further, we apply phase partitioning calculations to investigate the application of inherent noble gas in CCS monitoring schemes. The low noble gas concentrations, and their associated elemental and isotopic ratios, would only be preserved when the injected CO2 remains almost pure and does not mix or interact with fluids already present in the reservoir (e.g. native gas, formation water). Interaction of the CO2 with the formation water will lead to noble gas stripping that overprints the highly depleted composition of the captured CO2 with a noble gas elemental and isotopic ratios characteristic of deep crustal fluids. This characteristic signature, especially when coupled with the distinct major gas composition of leaked CO2 (e.g. extreme CO2/CH4 ratios) may form an effective tracer to discriminate a CO2 leakage from other gas sources at the seabed (e.g. shallow biogenic, dissolved air or hydrate decomposition). To take advantage of this low cost tracer, baseline geochemical surveys should include inventories of the background dissolved noble gas load in the formation water of storage reservoirs, in other (hydrocarbon bearing) formations along the migration route and in existing seabed gas seeps overlying the storage site.

We have carried out detailed noble gases and nitrogen isotopic study of two eucrites Vissannapeta, Piplia Kalan and one howardite Lohawat. Neon is mainly produced by Galactic Cosmic Ray (GCR) in all the three meteorites. The estimated cosmic ray exposure ages are 23.8 ± 6.1 Ma, 28.4 ± 8.1 Ma and 46.4 ± 17.3 Ma for Piplia Kalan, Vissannapeta and Lohawat, respectively. Light nitrogen composition is present in Vissannapeta and Lohawat, while heavy nitrogen composition is observed in Piplia Kalan. The nitrogen is distinctly trapped in the eucrites. Elemental ratios of the trapped noble gases such as argon, krypton and xenon together with nitrogen composition in eucrites indicate their distinct source region in Vesta. A younger potassium-argon age for the eucrites (3.71 ± 0.42 Ga for Vissannapeta and 3.60 ± 0.15 Ga for Piplia Kalan) than the solar system formation age, indicates partial loss of the radiogenic argon during the evolutionary stages of these meteorites plausibly due to impact metamorphic events. The radiogenic ages derived from the 4He are less than 1 Ma suggesting loss of helium from the eucrites.

The relativistic effects on energetic quantities of the HNgF → HF + Ng (Ng = Ar, Kr, Xe, and Rn) reactions were evaluated by means of advanced four-component calculations with high-level electron correlation treatment and adequate relativistic basis sets. The results indicate that the scalar relativistic corrections can provide classical barrier height increments of as much as 4.8% (1.9 kcal mol−1) for the reaction with the heaviest noble gas, radon, while the spin-orbit coupling is almost as important in this case, lowering the value by 3.8% (−1.5 kcal mol−1). Therefore, these two relevant relativistic corrections cancel almost completely. A similar picture is seen for the energy variation from the reactant (HRnF) to the products (HF + Rn), but the contribution signs are reversed now (−4.0 and 3.4 kcal mol−1). A partial cancelling is also noticed for the HXeF → HF + Xe reaction. Such pattern is surprising since scalar relativistic effects usually predominate by magnitude orders over the spin-orbit coupling. These conclusions are reflected in the changes observed in rate constant values. Finally, an alternative decomposition route catalyzed by HF is suggested for these HNgF compounds, which can shed some light on the controversies regarding their thermal stability.

The recent proliferation of tight or unconventional petroleum bearing reservoirs as an energy resource enables a more detailed investigation of the geochemical behaviour of these systems. In addition, it provides an opportunity to improve our understanding of low-permeability crustal fluid systems at depth. Organic-rich shales are not only the source-rocks in conventional petroleum systems, but potential seals, which may be important for the trapping and storage of CO2 and/or nuclear waste. The use of noble gas isotopes as tracers of fluid provenance and physical exchange processes is well established in other crustal fluid systems. Noble gas concentrations and isotopic characteristics were determined in 10 natural gas samples produced from the Eagle Ford shale, Texas, along with the concentration and δ13C and δD of hydrocarbon gases. By sampling gases produced directly from unconventional reservoirs we are able to determine their residence time and the extent of interaction of these fluids with other fluids in the wider hydrogeological system. The large range in thermal maturity exhibited across the basin, as demonstrated by the range in δ13C of methane from −37.8 to −47.5‰ VPDB, allows us to constrain the evolution of the noble gas signature within a source-rock during hydrocarbon generation and expulsion. For the first time, we show that 36Ar concentrations in hydrocarbon gases are not simply controlled by solubility exchange with formation water. Instead, they are shown to decrease dramatically (from 2.6 × 10−7 to 7.0 × 10−9 cm3STPcm−3) with increasing thermal maturity, which we attribute to a dilution effect as more short-chain hydrocarbon compounds are generated through cracking of kerogen and secondary cracking of oil. We develop a model that combines 36Ar concentrations with δ13C data in order to quantify the retention capacity for generated hydrocarbons, and show that between 40 and 80% of the hydrocarbons generated by the Eagle Ford shale are retained within the formation. We also calculate that radiogenic 4He concentrations within the Eagle Ford are well in excess of that which could have accumulated internally since deposition and requires contributions from external 4He sources. The identification of both hydrocarbon expulsion and helium addition to nominally ‘tight’ formations now provides a process driven and quantitative understanding of the fluid migration dynamics and processes controlling these critical formations.

The radiation-induced transformations of acetylene, ethylene and ethane molecules under X-ray radiolysis in cryogenic media (noble gas matrices and neat hydrocarbon ices) at 5 K were characterized by FTIR spectroscopy. The radiation-chemical yields of decomposition of isolated hydrocarbon molecules were estimated in different solid noble gas matrices (argon, krypton and xenon). It was found that the radiation resistance of hydrocarbons at molecular level increases in the order ethane

MgO is known to be a material suitable for barrier coating of commercial plasma display panel (PDP) cells owing to its excellent electrical insulating property, good resistance to sputtering, large secondary-electron emission coefficient and high transmittance. It is also a valuable information for improving the efficiency and the lifespan of the PDP. However, the effect of moisture emitted from the wall and phosphor materials of the PDP cells, an Mg(OH)2 is formed on the top surface of an MgO protective layer. In this work, the Monte Carlo simulation program SRIM-2013 was applied to calculate the sputtering yields of magnesium hydroxide Mg(OH)2 by low-energy noble-gas ion bombardment. The comparison between results obtained by Monte Carlo simulation and those obtained by experiments is elucidated in this paper. Furthermore, the surface binding energies for MgO and Mg(OH)2 layers on sputtering yield are discussed. It is found that the sputtering yield of Mg(OH)2 is generally lower than that of MgO at each incident energy. On the other hand, the sputtering yield depends on the properties of both the incident particle and the target.

We measured noble gas isotopic compositions of quenched lavas sampled from seamounts, so-called petit-spot volcanoes, on the 160-million-year-old northwestern Pacific Plate. The samples He-3/He-4 and Ar-40/Ar-36 ratios were, respectively, 2.5-8.3 Ra and up to 1735, where Ra stands for atmospheric He-3/He-4, which are analogous to or lower than those of MORB. Considering narrow sampling regions, a secondary effect might be responsible for variation of the data. During ascent and subsequent cooling of magma in the oceanic lithosphere, chemical components in the magma will be assimilated with those in the lithosphere. Correlation between CO2/He-3 ratios and carbon isotopic ratios suggests that carbon was affected by the incorporation of seafloor carbonate. The same would be true of noble gases. The mixing of noble gases among a mantle source, an atmospheric component dissolved in seawater and a radiogenic component can explain the data distribution. No He-3/He-4 ratio exceeds the MORB-like value. The mantle source of the petit-spot magma was likely to have had a MORB-like He-3/He-4 ratio originally. The eruption of petit-spot magma shows a close relation with the bending of subducting oceanic plates. The MORB-like He-3/He-4 ratio supports the hypothesis that the petit-spot magma is derived from the lithosphere-asthenosphere boundary. (C) 2018 Elsevier B.V. All rights reserved.

The fluxes of volatile elements from the mantle have long been used to understand mantle structure and evolution, and are critical controls on Earth's climate stability. Because of the ubiquity of magmatic degassing, inferring pre-degassing volatile concentrations from measured basalts requires the application of a degassing model. Such models, including the commonly-applied equilibrium Rayleigh distillation, typically assume equilibrium or solubility-based partitioning between melt and vapor. Here, we demonstrate that ratios of radiogenic isotopes of He, Ne, Ar and, especially, Xe measured in global mid-ocean ridge basalts (MORBs) are inconsistent with equilibrium degassing models, even when not considering He. We conclude that kinetic disequilibrium is a crucial process affecting volatile abundances during degassing. We present a simple disequilibrium Rayleigh distillation model to reconstruct pre-degassing MORB noble gas and carbon concentrations, which predicts that He and Ne achieve nearly equilibrium partitioning between melt and vesicles, but the slower-diffusing heavier noble gases are strongly affected by disequilibrium, resulting in non-equilibrium fractionation of noble gas elemental ratios, and other volatile element ratios like CO2/He. We apply our model to a large set of MORB data, and find average pre-degassing 3He, 22Ne, and 36Ar concentrations of 4.4 ± 0.9 × 10−10, 6.6 ± 1.4 × 10−11, and 6.8 ± 4.5 × 10−10 ccSTP/g (2σ), with variations of approximately 2 orders of magnitude, similar to other highly incompatible elements. Pre-degassing noble gas concentrations imply a mid-ocean ridge 3He flux of 800 ± 170 mol/yr and upper mantle 3He/22Ne and 3He/36Ar ratios of 6.6 ± 2.0 and 0.64 ± 0.44, but substantial variability in these ratios between samples. Applying our model to CO2, we calculate an average mantle CO2/3He molar ratio of 1.67 ± 0.21 × 109, which, when combined with our estimate of 3He flux, implies an upper mantle CO2 flux of 5.9 ± 1.0 × 1013 g/yr and a CO2 concentration of approximately 110 ppm. Our estimate of the mantle 3He flux is the first determined independently of oceanographic 3He measurements, and consequently represents a time-integrated flux substantially longer than ∼1000 years. And although at the high end of the range of previous estimates, our estimate does not resolve the long-standing heat-helium paradox. Additionally, our requirement for heterogeneous pre-degassing 3He/22Ne and 3He/36Ar ratios between samples is contrary to conclusions of previous applications of disequilibrium degassing models, which advocated uniform ratios. Furthermore, we find that CO2/Ba ratios are highly variable in MORB samples, but still consistent with an average mantle mass ratio of ∼100. However, estimating pre-degassing CO2 concentrations and the mantle CO2 flux depend strongly on the poorly-constrained carbon diffusivity. Consequently, our demonstration of the prevalence of disequilibrium during mid-ocean ridge degassing, and the potential for disequilibrium in other volcanic settings, highlights the need for better characterization of the physical parameters associated with volcanic degassing.

Xenon is a rare, mostly inert, noble gas that has applications in a wide range of fields, including medicine. Xenon acts on the human body as a useful organ-protective and anesthetic agent and has also been previously studied for potential applications in fields such as optics, aerospace and medical imaging. Recently, it was discovered that xenon can boost erythropoietin production, and it has been used as a performance-enhancing agent in international sports competitions such as the Sochi Olympic Games. Therefore, screening methods to detect the misuse of xenon by analysis of biological samples and to monitor anesthesia kinetics and efficiency are being investigated. The aim of this study was to develop and validate an analytical method to detect xenon in blood samples using gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). Preliminary studies were conducted to determine the best parameters for chromatography and mass spectrometry for xenon. The analysis was performed using the multiple reaction monitoring (MRM) mode using the transitions m/z 129 → 129, 131 → 131 for xenon and 84 → 84, 86 → 86 for krypton, which was chosen as the internal standard. The LOD of GC-MS/MS was found to be 52 pmol on-column. Calibration lines and controls were made to obtain an accuracy profile at a range of 2.08-104 nmol with a β-expectation tolerance interval set at 80% and the acceptability limit set at ±30%. From the accuracy profile, the LOQ of 15 nmol on-column for the range of 2.08-104 nmol was obtained. The method was validated according to the guidelines of the French Society of Pharmaceutical Sciences and Techniques. The detection method was finally validated using blood from test persons subjected to a 15% or 30% xenon mixture with pure oxygen and air for 45 min. Even though the probes were already used for other projects, it was still possible to detect xenon.

In this study, the infrared absorption spectra of 2-methyl-1,3-butadiene (isoprene) in noble gas matrices (Ar, Kr, and Xe) have been reported. The vibrational structure observed at cryogenic temperature, in combination with anharmonic vibrational calculations using density functional theory, helped in unambiguously assigning the fundamental modes of isoprene unresolved in the previous gas phase measurements, which would be of basic importance in the remote sensing of this molecule. A careful comparison with the most recent gas phase study [Brauer et al., Atmos. Meas. Tech. 7 (2014) 3839–3847.] led us to alternative assignments of the weak bands.

Molecular diffusion is a key transport process for noble gases in water. Such diffusive transport is often thought to cause a mass-dependent fractionation of noble gas isotopes that is inversely proportional to the square root of the ratio of their atomic mass, referred to as the square root relation. Previous studies, challenged the commonly held assumption that the square root relation adequately describes the behaviour of noble gas isotopes diffusing through water. However, the effect of diffusion on noble gas isotopes has only been determined experimentally for He, Ne and Ar to date, whereas the extent of fractionation of Kr and Xe has not been measured. In the present study the fractionation of Kr and Xe isotopes diffusing through water immobilised by adding agar was quantified through measuring the respective isotope ratio after diffusing through the immobilised water. No fractionation of Kr and Xe isotopes was observed, even using high-precision noble gas analytics. These results complement our current understanding on isotopic fractionation of noble gases diffusing through water. Therefore this complete data set builds a robust basis to describe molecular diffusion of noble gases in water in a physical sound manner which is fundamental to assess the physical aspects of gas dynamics in aquatic systems.

We present the results of physical properties, petrography, bulk chemistry, mineral compositions, phase relations modelling and Noble gases study of the meteorite El Pozo. The petrography and mineral compositions indicate that the meteorite is an L5 chondrite with a low shock stage of S2-S3. Heterogenous weathering was preferentially along shock structures. Thermobarometric calculations indicate thermal equilibrium conditions between 768 °C and 925 °C at ∼4 to 6 kb, which are substantially consistent with the petrological metamorphism type 5. A pseudosection phase diagram is relatively consistent with the mineral assemblage observed and PT conditions calculated. Temperature vs. fO2 diagram shows that plagioclase compositional stability is very sensitive to Tschermack substitution in orthopyroxene, clinopyroxene and XAn plagioclase during the high temperature metamorphic process. Based on noble gases He, Ne, Ar and K contents a cosmogenic exposure age CRE of 1.9 Myr was calculated. The 21Ne would be totally cosmogenic, with no primordial Ne. The 21Ne/22Ne value (0.97) is higher than solar value. According to the cosmogenic Ne content, we argue that El Pozo chondrite originally had a pre-atmospheric mass of 9–10 kg, which would have been produced by a later collision after the recognized collision of the L-chondrite parent body ∼470 Ma ago.

Noble gas concentrations in water are ideal probes to study surface and groundwater dynamics by providing indications of flow paths, connectivity between aquifers, and water residence times. Recent studies have pointed out anomalies in noble gas concentrations derived from groundwater in fractured systems, likely due to the presence of rapid infiltration and preferential flow paths. It has been suggested that such anomalies originate from conditions at high altitude when rainwater has had insufficient time to equilibrate with surface conditions. Potential sources also include snow, never previously investigated for its noble gas composition. In order to document the noble gas signature in snow, noble gas concentrations and isotopic ratios were measured in samples collected between 2013 and 2016. Here, we outline a methodology for measuring noble gases in collected snow samples that involves a two-step procedure where He and Ne are measured independently from Ar, Kr and Xe. Our results show that snow has elevated He concentrations with depleted concentrations of other noble gases with respect to air-saturated water (ASW). However, samples collected in 2013 show significant He and Ne depletion compared to those collected in 2014, 2015 and 2016. We suspect that, despite the well-controlled conditions of storage, the 2013 batch sample might have significantly re-crystalized, leading to a reduction in the characteristic diffusion length scale of the snow crystal structure. In addition, He and Ne concentrations display relatively low variability among all measured samples ( 40%). Our results confirm that He and Ne, which have small atomic radii, are likely dissolved within the ice/snow crystal lattice itself while the heavy noble gases (Ar, Kr and Xe) are likely accommodated by fluid inclusions, including air and quenched liquid water inclusions. Consequently, the smaller variability recorded in light noble gases may be due to the fact that He and Ne are hosted within plentiful host sites within the snow crystal lattice structure, whereas heavy noble gases rely on the presence of comparatively rare fluid inclusions.

The effect of the type of C3-C6 alcohol, solution temperature, and dissolved gas on the rate of Au(III) reduction was investigated in NaAuCl4 aqueous alcohol solution with a 200-kHz ultrasound irradiation system. It was confirmed in the presence of C3-C6 alcohol that more highly hydrophobic alcohols more effectively accumulated at the argon bubble interface region, and the reducing radicals formed here. To avoid changes in the bubble temperature during collapsing bubble, the effects of the solution temperature on the rate of Au(III) reduction and on the rate of formation of the gaseous compounds (CO, CO2, CH4, C2H2, C2H4, C2H6) were investigated in the presence of low concentration (1.0-mM) of 1-hexanol. Both of the rates showed a good relationship with the gas solubility: the amount of dissolved gas at different solution temperatures affected the number of high-temperature bubbles formed. The changes in the concentrations of the gaseous compounds formed from 1-hexanol degradation suggested that CO and the pyrolysis radicals acted as reductants. Finally, the effect of the type of dissolved gas was investigated in the presence of 1.0-mM Au(III) and 1.0-mM 1-hexanol. The rates of 1-hexanol degradation, Au(III) reduction, and gaseous compound formation increased in the order He

Noble gases have become a powerful tool to constrain the origin of fluids as well as the rates of fluid migration in sedimentary basins. The aim of this study was to apply these tracers to understand the genesis and the evolution of unconventional gas reservoirs, basin-centered gas reservoirs (also called tight-gas reservoirs). A natural laboratory for this study is the methane-rich gas field in Cretaceous tight sands from the Western Canadian Sedimentary Basin (WCSB). The selection of the WCSB was motivated by an easy access to wells that cover an extensive area from deep to shallow parts of the basin, as well as the relatively well documented geology and hydrology of the area. The elemental noble gas signature (He, Ar, Kr and Xe) of natural gas from 18 wells of the basin shows a mixture between the original low content noble gas signature of the hydrocarbon gas (after its charge into the reservoir) and water (trapped in intergranular volumes (IGV)), which is comparatively rich in noble gases. This difference in relative contents can be used to estimate the geographical position of the contact between the gas reservoir and the shallower IGV water. Furthermore, the ‘original’ noble gas signature, which is defined as the noble gases generated in the source, later transferred, and mixed with in situ produced noble gases in the reservoir, is mainly composed of radiogenic isotopes (40Ar and 4He). The comparison of 4He/40Ar ratios with an average value for potential source rocks and reservoir rocks production ratio (estimated with U, Th and K concentrations) allows us to understand how the gas was transferred from the source rock to the reservoir rock. These results, combined with the geological and hydrological knowledge of the WCSB, affords a new method to better understand the dynamics of unconventional gas reservoirs.

Summary The global demand for Xenon (Xe), a noble gas with applications in electronics, lighting, and the medical industry, is expected to increase significantly over the coming decades. However, the low abundance of Xe in the Earth's atmosphere and the costly cryogenic distillation process that is used to obtain Xe commercially via air separation have limited the scale of applications of Xe. A physisorption-based separation using porous materials could be a viable and cost-effective alternative to cryogenic distillation. In particular, metal-organic frameworks (MOFs) have shown promise as highly Xe-selective porous solids. In this review, we discuss the recent advances of MOFs as adsorbents for noble gas adsorption and separation and the role of computer simulation in finding optimal materials for Xe adsorption. Video Abstract

We have calculated the zero equation of state of solid helium using a two-body Hartree–Fock dispersion (HFD)-like potential from molecular dynamics (MD) simulation. To take many-body forces into account, our simple and accurate empirical expression is used with the HFD-like potential without requiring an expensive three-body calculation. This potential model also includes the quantum effects for helium at low temperatures. The results indicate that our effective HFD-like potential improves the prediction of the classical two-body results to get better agreement with experiment than many other two-body and three-body potentials of helium reported in the literature. We have also simulated the adsorption and desorption processes of the (He) 55 , (He) 147 , (He) 309 , (He) 561 , and (He) 923 icosahedral nanoclusters confined into the different armchair and zigzag CNTs from 0 to 50 K using our effective model. We have observed an interesting phenomenon at 0 K for helium. The nanoclusters adsorb to the inner CNT wall as a melting process. But, the heavier noble gas clusters (such as Ne and Xe) show the different behavior than the He clusters. They form a multilayered solid structure into the CNT at zero temperature and adsorb into the inner wall of the CNT at higher temperatures. Our results for He clusters show that the absolute value of the adsorption energy increases as the size of the nanocluster increases. The desorption process begins at a certain temperature and represents itself by a jump in the configurational energy values. We have also investigated the structural and dynamical properties of the confined helium nanoclusters during the adsorption and desorption processes at different temperatures.

Density functional theory calculations are used to explore the Li storage capacity of Ngm endohedral C60 fullerenes (Ng=He, Ne, Ar, Kr, Xe; m=1,2). Formation energies of Ng endohedral fullerenes are negative, ranging from -2.65 to -13.11 kcal/mol (at the PBE/DNP level). The incorporation of Ng and Ng2 moieties into C60 enhances the adsorption energy of Li. The maximum adsorption energy of the Li atom on Xe2 encapsulated C60 is about -45 kcal/mol, which is 7% larger than that of on pure C60. The presence of Ng atoms lowers the energy barrier for Li migration to neighboring pentagon or hexagon rings.

A uniform magnetic field is required to establish and preserve the spin-polarized state in noble gases with non-zero nuclear spins. Such spin-polarized noble gases, e.g. 3He and 129Xe, exhibit unique properties that are interesting in scientific and medical imaging applications. The balance of field uniformity, spatial accessibility, size and feasibility of construction is vital in the design and optimization of such magnet systems. magcoilcalc is an open-source Python library that enables users to efficiently model, simulate and optimize magnets consisting of axisymmetric circular current loops, such as solenoid coils and Helmholtz coils and their variants.

In regions where water resources are scarce and in high demand, it is important to safeguard against contamination of groundwater aquifers by oil-field fluids (water, gas, oil). In this context, the geochemical characterisation of these fluids is critical so that anthropogenic contaminants can be readily identified. The first step is characterising pre-development geochemical fluid signatures (i.e., those unmodified by hydrocarbon resource development) and understanding how these signatures may have been perturbed by resource production, particularly in the context of enhanced oil recovery (EOR) techniques. Here, we present noble gas isotope data in fluids produced from oil wells in several water-stressed regions in California, USA, where EOR is prevalent. In oil-field systems, only casing gases are typically collected and measured for their noble gas compositions, even when oil and/or water phases are present, due to the relative ease of gas analyses. However, this approach relies on a number of assumptions (e.g., equilibrium between phases, water-to-oil ratio (WOR) and gas-to-oil ratio (GOR) in order to reconstruct the multiphase subsurface compositions. Here, we adopt a novel, more rigorous approach, and measure noble gases in both casing gas and produced fluid (oil-water-gas mixtures) samples from the Lost Hills, Fruitvale, North and South Belridge (San Joaquin Basin, SJB) and Orcutt (Santa Maria Basin) Oil Fields. Using this method, we are able to fully characterise the distribution of noble gases within a multiphase hydrocarbon system. We find that measured concentrations in the casing gases agree with those in the gas phase in the produced fluids and thus the two sample types can be used essentially interchangeably. EOR signatures can readily be identified by their distinct air-derived noble gas elemental ratios (e.g., 20Ne/36Ar), which are elevated compared to pre-development oil-field fluids, and conspicuously trend towards air values with respect to elemental ratios and overall concentrations. We reconstruct reservoir 20Ne/36Ar values using both casing gas and produced fluids and show that noble gas ratios in the reservoir are strongly correlated (r2 = 0.88–0.98) to the amount of water injected within ~500 m of a well. We suggest that the 20Ne/36Ar increase resulting from injection is sensitive to the volume of fluid interacting with the injectate, the effective water-to-oil ratio, and the composition of the injectate. Defining both the pre-development and injection-modified hydrocarbon reservoir compositions are crucial for distinguishing the sources of hydrocarbons observed in proximal groundwaters, and for quantifying the transport mechanisms controlling this occurrence.

Difluoromethane (CH2F2) is considered as an ecologically friendly alternative to conventionally used chlorofluorocarbons for various applications. Being photochemically inert in the broad UV range, this molecule can be decomposed only through the action of hard vacuum UV or ionizing radiation, while the corresponding mechanisms are poorly studied. In this work we report the results of model investigations of the X-ray induced decomposition of isolated CH2F2 in solid noble gas matrices at 6 K. The radiation-chemical yields of difluoromethane were found to decrease from 1.3 to 0.1 molecule/100 eV with decreasing the ionization energy of matrix (from Ne to Xe), which indicates significance of the “hot” ionic channels. Difluorocarbene (CF2) was detected as one of the principal radiolysis products in all the matrices, whereas the CHF⋯HF complex was detected in Ne, Ar, and Kr. Annealing of the irradiated samples results in thermally induced reactions of trapped H and F atoms yielding a number of various species, including the noble gas compounds. The radiolysis mechanism, nature of matrix effects and possible implications for atmospheric chemistry are discussed.

This work is focused on controlling and optimizing the inclusion of neon (Ne) and argon (Ar) impurities in tungsten (W) reference coatings. A tungsten target has been sputtered in monopolar and bipolar High Power Impulse Magnetron Sputtering (HiPIMS) operation modes, in Ar-Ne gas mixture. It has been found that the process of noble gas retention in W thin layers is strongly dependent on both ion energy and average flux to the substrate. The ion energy can be accurately controlled by the amplitude of the positive voltage pulse while the average ion flux can be controlled by the duration of the negative pulse. Measurements of the plasma potential in front of the substrate and the ion saturation current at the substrate position allow explaining the mechanism of ion acceleration and the control of ion energy and flux. The effect of the pulsing configuration on the microstructure of the co-deposited films has been investigated by X-ray Diffractometry, Scanning Electron Microscopy and Atomic Force Microscopy, while the amount of noble gas enclosed in the coatings has been measured by Non-Rutherford Backscattering Spectrometry. Ne and Ar amount in the W co-deposited layers increases up to 3.0 at.% each as the amplitude of the positive pulse increases to + 300 V or the negative pulse duration decreases to 3 µs. The highest film crystallinity, with W(1 1 0) preferential growth, has been obtained for a positive pulse voltage of + 200 V and a negative pulse duration of 5 µs. The thickness of the deposited layers ranges between 350 nm in bipolar HiPIMS with a positive pulse voltage of + 300 V and 550 nm in monopolar HiPIMS.

Helium is an unrenewable noble gas produced from natural gas with a wide range of scientific, medical, and industrial applications. Due to the large differences in the kinetic diameters between helium (0.26 nm) and nitrogen (0.364 nm) or methane (0.38 nm), membrane technology has been considered a promising alternative to traditional technologies for helium recovery and purification. This paper systematically reviews the advances in membrane material development for helium separation in recent years. Gas permeation data presented in this work were collected from over 1000 membrane materials, including polymeric, inorganic, and mixed matrix membranes. Moreover, membrane processes for helium recovery and purification from natural gas were critically analyzed and discussed concerning technical feasibility, energy consumption, and separation costs. Challenges in helium purification using membrane technology were also discussed, and potential solutions have been suggested. Lastly, future perspectives on research directions on membrane material development and hybrid helium purification process design and optimization are proposed.

The noble gas xenon possesses many characteristics of an ideal anaesthetic agent. However, its application is limited in daily clinical routine due to its elevated price. The present work proposes the use of a gas-ionic liquid membrane contactor system in anaesthesia closed-circuits, for the removal of carbon dioxide, to allow the recycling of the anaesthetic agents, as a route to enable the widespread use of xenon. In this work, different anaesthetic gas delivery conditions were simulated and explored, considering the use of different anaesthetic gas mixtures. The results obtained, using a cholinium lysinate ionic liquid solution as CO2 absorbent, expressed high efficiency, especially when xenon was used as the inhalational anaesthetic, leading to an overall CO2 mass transfer of 1.26 × 10−5 m.s−1. The ability of the proposed system to recover xenon allows to reduce drastically the cost per operation, which can be a step forward for the routine use of this gas on surgeries. Additionally, this work evaluates the use of thermal and chemical regeneration of the ionic liquid solution. It was found that the thermal regeneration approach was not adequate for the regeneration of the IL. On the other hand, the use of ion-exchange resins proved to be an efficient and simple strategy for IL regeneration, allowing for an easy integration in the proposed system. This study opens a new direction not yet explored that may lead to more efficient IL regeneration processes.

We investigated noble gas (He, Ne, Ar, Kr and Xe) and nitrogen isotopic composition in the carbonaceous chondrite Bukhara (CV3). This is the first report of N and noble gases measured in the same aliquot of bulk sample among the CV3 chondrites. Isotopic compositions of noble gases are mixtures of solar wind and Q-gases. We derive cosmic ray exposure (CRE) age of 22.6 ​± ​4.0 ​Ma from cosmogenic 21Ne and 38Ar for Bukhara. Nitrogen abundance observed in Bukhara is lowest compared with the data from CV3 chondrites. We estimate the trapped nitrogen composition of δ15N ​= ​+ 10.9 ​± ​1.6‰ for Bukhara, distinct from average (δ15N ​= ​- 16.3 ​± ​1.5‰) in the bulk CV3 chondrites. Bukhara shows signature of heavy nitrogen, which is distinct than the solar wind (SW) and Q-gas. Trapped nitrogen is mixture of the components, SW, Q and comet. It is observed that there is no correlation of nitrogen composition with N content in the CV3 chondrites.

We determined the heavy halogen (Cl, Br, and I) concentrations of fourteen powdered geological reference materials distributed by the Geological Survey of Japan (GSJ) and the US Geological Survey, and seven original blocks of GSJ geological reference materials, using neutron irradiation noble gas mass spectrometry (NI-NGMS). The halogen concentrations obtained from the powder and original blocks of geological reference materials are systematically lower than their reference values for low-concentration samples. This discrepancy can be explained by contamination on the sample surface during the preparation of the reference materials. Contaminated halogen-derived noble gases were, at least partially, removed before analysis during preheating of the samples under vacuum after sample loading. The presence of the contaminated component in the reference materials is not a matter for other analytical methods as long as the contaminated component is completely homogenized in the powder reference materials and not removed before analysis. However, the present results indicate that the standard materials used in NI-NGMS should be selected more carefully than those used in other methods. In addition, we propose an F-determination method using NI-NGMS based on Ne systematics of neutron-irradiated samples.

The large difference in carbon isotopic compositions of shale gases from the Lower Silurian Longmaxi Formation marine organic-rich shales between Changning and Weiyuan areas in Sichuan Basin, China is a still debate issue. In this study, 30 produced shale gas samples were collected during 3 years production period and analyzed for noble gas (He, Ne and Ar) abundances and isotopic compositions to reveal the origin and variation causes of shale gases. The results show that the Longmaxi shale gases show low 3He/4He and 20Ne/22Ne, and varied but high 21Ne/22Ne and 40Ar/36Ar ratios. The Weiyuan shale gases are characterized by low 3He/4He, high 40Ar/36Ar ratios and varied 4He and 40Ar abundances, and a large increase in 40Ar contents and a slight decrease in 40Ar/36Ar ratios display during 3 years shale gas production period from Jan. 2014 to Jun. 2016. Whereas the Changning shale gases are characterized by low and varied 3He/4He ratios and high 4He and 40Ar abundances, and small fluctuations in 40Ar contents and 40Ar/36Ar ratios exhibit during 3 years production period. In addition, the shale gases produced from horizontal wells in the Weiyuan area possessed higher 40Ar and 40Ar/36Ar ratio than that those from vertical wells at same well site. The noble gas isotopic compositions and variation of Longmaxi shale gases suggested that they are originated mainly from crust, air saturated fluid (ASF) and radiogenic accumulation. The variation of 40Ar and 4He contents during shale gas production mainly reflects the degree of shale gas source supply from mineral matrix to fracture network, and the greater increases in 40Ar and 4He contents with production time show less abundant shale gas supply. Therefore, the increase trend of 40Ar contents with shale gas production time in the Weiyuan area during 3 years production period possibly suggests less adequate shale gas supply. In contrast, the uniform or nearly constant of 40Ar content through production time in the Changing area indicates abundant supply of shale gas sources from mineral matrix, resulting in less production decline. Variation in 4He and 40Ar contents through shale gas production time could be sensitive indicators of abundant or depleted shale gas source supply.