Heavy Noble Gases Research Articles

Insights on the Formation Conditions of Uranus and Neptune from Their Deep Elemental Compositions

This study, placed in the context of the preparation for the Uranus Orbiter Probe mission, aims to predict the bulk volatile compositions of Uranus and Neptune. Using a protoplanetary disk model, it examines the evolution of trace species through vapor and solid transport as dust and pebbles. Due to the high carbon abundance found in their envelopes, the two planets are postulated to have formed at the carbon monoxide ice line within the protosolar nebula. The time evolution of the abundances of the major volatile species at the location of the CO ice line is then calculated to derive the abundance ratios of the corresponding key elements, including the heavy noble gases, in the feeding zones of Uranus and Neptune. Supersolar metallicity in their envelopes likely results from accreting solids in these zones. Two types of solids are considered: pure condensates (Case 1) and a mixture of pure condensates and clathrates (Case 2). The model, calibrated to observed carbon enrichments, predicts deep compositions. In Case 1, argon is deeply depleted, while nitrogen, oxygen, krypton, phosphorus, sulfur, and xenon are significantly enriched relative to their protosolar abundances in the two planets. Case 2 predicts significant enrichments for all species, including argon, relative to their protosolar abundances. Consequently, Case 1 predicts near-zero Ar/Kr or Ar/Xe ratios, while Case 2 suggests that these ratios are 0.1 and 0.5–1 times their protosolar ratios, respectively. Both cases predict a bulk sulfur-to-nitrogen ratio consistent with atmospheric measurements.

The low primordial heavy noble gas and 244Pu-derived Xe contents of Earth's convecting mantle

Clues to unraveling the origin and history of terrestrial volatiles lie in the noble gas record of Earth's mantle. However, the low abundance of heavy noble gases (Ar-Kr-Xe) in mantle-derived rocks presents a major analytical challenge that limits our understanding of mantle volatile evolution. Here, we employ a new technique of ultrahigh precision dynamic mass spectrometry to measure Ar-Kr-Xe isotopes in mantle-derived gas collected from Mt. Etna (Italy) and Eifel (Germany), which both tap depleted convecting mantle reservoirs. We find that the fractions of primordial Kr-Xe from accretionary sources (≤ 7 % of non-radiogenic, non-fissiogenic isotopes) and 244Pu-derived 136Xe (≤ 9.8 ± 9.3 % of total fissiogenic Xe) are both markedly lower than previously estimated. For Mt. Etna, we find an apparent lack of detectable primordial Xe, which could reflect an additional contribution from recycled atmospheric volatiles from nearby subduction. In addition, slight excesses of 238U-derived fissiogenic Xe relative to the upper mantle composition may reflect the contribution of a crustal component related to the occurrence of a HIMU (“high μ” where μ = 238U/204Pb)-type source in Mt. Etna volcanic products. The low primordial heavy noble gas and 244Pu-derived Xe contents of Earth's convecting mantle, as derived from these new data, requires extensive volatile loss during terrestrial accretion, followed by long-term degassing and pervasive overprinting of primordial heavy noble gases by subduction recycling. In addition, we suggest that quantitative incompatible element (including Pu, U) extraction to the Hadean crust and subsequent reintroduction of U via subduction could have contributed to lowering the ultimate fraction of 244Pu-derived 136Xe in the upper mantle. The differences observed between this study and other upper mantle Xe studies may reflect mantle source heterogeneities (e.g. due to the heterogeneous overprinting of mantle volatiles by subduction) but could also result from analytical inconsistencies and/or subsurface isotope fractionation in natural systems. Future studies are crucial to gain insight into the origin of these different results.

The thermal equation of state of xenon: Implications for noble gas incorporation in serpentine minerals and their transport to depth

Isotopic signatures of heavy noble gases in the Earth's mantle contain a major component recycled by subduction. The experimental and field studies reported in the literature show increasing evidence that serpentine minerals can hold large quantities of noble gases, potentially serving as their primary vectors to depth. However, at present, their retention mechanism in these minerals is not fully understood. Additionally, noble gas solubilities from field and experimental studies show large differences in terms of elemental concentrations. Here, we performed crystal chemical modeling to evaluate the incorporation mechanism of noble gases and their solubilities in serpentine minerals along subduction zone geotherms. To this end, we determined the thermal equation of state of xenon using in situ X-ray diffraction and absorption up to 60 GPa and 728 K. In this range, the xenon equation of state is well-adjusted using the Mie-Grüneisen-Debye formalism with relevant fitting parameters. We show that the experimentally observed solubility trend, which follows the order Ne < He < Ar < Kr < Xe, can be explained by the incorporation of noble gases at two distinct crystallographic sites. The light noble gases He and Ne are most likely retained at the van der Waals hydrogen-oxygen bond position between the layers, while the heavy and larger noble gases enter the voids between the six-membered SiO4 rings. It should be noted that octahedral sites can potentially host xenon, but cannot accommodate argon and krypton. Indeed, this would require unrealistic flexibility of the crystal lattice. Our models extended to mantle wedge conditions predict decreasing solubilities, particularly for light noble gases, in agreement with observations from natural samples. Compared to the noble gas concentrations determined experimentally in serpentine, natural concentrations are much higher and very variable. Our solubility model confirms that equilibrium processes cannot explain these observations. We therefore suggest that the high and variable noble gas concentrations found in natural samples must be due to hybrid hydration processes in ultramafic rocks that involve different degrees of water activities.

Ab initio determination of melting and sound velocity of neon up to the deep interior of the Earth.

The thermophysical properties and elemental abundances of the noble gases in terrestrial materials can provide unique insights into the Earth's evolution and mantle dynamics. Here, we perform extensive abinitio molecular dynamics simulations to determine the melting temperature and sound velocity of neon up to 370GPa and 7500K to constrain its physical state and storage capacity, together with to reveal its implications for the deep interior of the Earth. It is found that solid neon can exist stably under the lower mantle and inner core conditions, and the abnormal melting of neon is not observed under the entire temperature (T) and pressure (P) region inside the Earth owing to its peculiar electronic structure, which is substantially distinct from other heavier noble gases. An inspection of the reduction for sound velocity along the Earth's geotherm evidences that neon can be used as a light element to account for the low-velocity anomaly and density deficit in the deep Earth. A comparison of the pair distribution functions and mean square displacements of MgSiO3-Ne and Fe-Ne alloys further reveals that MgSiO3 has a larger neon storage capacity than the liquid iron under the deep Earth condition, indicating that the lower mantle may be a natural deep noble gas storage reservoir. Our results provide valuable information for studying the fundamental behavior and phase transition of neon in a higher T-P regime, and further enhance our understanding for the interior structure and evolution processes inside the Earth.

Assessing the potential for CO2 storage in shallow coal seams using gas geochemistry: A case study from Qinshui Basin, North China

Shallow coal seams are a target reservoir for CO2 sequestration. So far efforts to trace CO2 sequestration by coal beds have largely focussed on short-term monitoring or theoretical modelling. To evaluate the feasibility of safe long-term storage of CO2 in shallow coal beds, we report the first systematic gas geochemical study at a shallow injection site in Shizhuang, Qinshui Basin, one year after CO2 injection ceased. The injected CO2 is isotopically distinctive and appears to be enriched in heavy noble gases (Kr and Xe). The high CO2 content and light δ13CCO2 of gases from production wells confirm the migration of injected gas to the northeast and east of the main injection well previously tracked by geophysical studies. The migration of injected gas to the southeast has not been identified before, and exceeds that to the northeast, implying that gas geochemistry provides a more robust method of tracking migration. Less than 1 % of the total injected CO2 has been extracted from production wells in the year since injection ceased. We estimate that the target coal seam in the study area can store about 0.08 billion tonnes of CO2. Scaling up we estimate that the Qinshui Basin has the potential to store about 19 billion tonnes of CO2. This is significantly more than previous estimates. This study demonstrates the importance of geochemical tracers in quantifying and monitoring CO2 sequestration and also implies that unmined coal seams have high potential for the long-term storage of CO2.

Characterization of XUV+IR ionization using the circular dichroic phase

A strong helicity dependence of reconstruction of attosecond bursts by beating of two-photon transitions (RABBITT) with circularly polarized XUV and IR pulses was reported by Han [ and ]. They attributed a circular dichroic phase in RABBITT to the helical structure of the photoelectron wave packets in the final state. We exploit this effect to determine the magnitude and phase of two-photon XUV+IR ionization amplitudes. In s-electron targets (H, He, Li), such a determination is fully and requires no further approximations. In heavier noble gases like Ar, characterization of two-photon ionization amplitudes can be made from the circular dichroic phase with minimal and very realistic assumptions. Published by the American Physical Society 2024

Unveiling distinct bonding patterns in noble gas hydrides via interference energy analysis.

Despite their apparent simplicity, the helium hydride ion (HeH+) and its analogues with heavier noble gas (Ng) atoms present intriguing challenges due to their unusual electronic structures and distinct ground-state heterolytic bond dissociation profiles. In this work, we employ modern valence bond calculations and the interference energy analysis to investigate the nature of the chemical bond in NgH+ (Ng = He, Ne, Ar). Our findings reveal that the energy well formation in their ground-state potential energy curves is driven by a reduction in kinetic energy caused by quantum interference, identical to cases of homolytic bond dissociation. However, clear differences in bonding situation emerge: in HeH+ and ArH+, electron charge transfer leads to Ng+-H covalent bonds, while in NeH+, a preferred Ne + H+ valence bond structure suggests the formation of a dative bond. This study highlights the distinct bonding mechanisms within the NgH+ series, showcasing the interplay between quantum interference and quasi-classical effects in molecules featuring noble gases.

Doubly charged dimers and trimers of heavy noble gases.

Many doubly charged heteronuclear dimers are metastable or even thermodynamically stable with respect to charge separation. Homonuclear dicationic dimers, however, are more difficult to form. He22+ was the first noble gas dimer predicted to be metastable and, decades later, observed. Ne22+ is the only other dicationic noble gas dimer that has been detected so far. Here, we present a novel approach to form fragile dicationic species, by post-ionization of singly charged ions that are embedded in helium nanodroplets (HNDs). Bare ions are then extracted by colliding the HNDs with helium gas. We detect homonuclear doubly charged dimers and trimers of krypton and xenon, but not argon. Our multi-reference ab initio calculations confirm the stability of Kr22+, Kr32+, Xe22+, Xe32+, and Ar22+, but put the stability of Ar32+ towards dissociation to Ar+ + Ar2+ into question.

Kestabilan Pencucuhan Hidrogen dalam Persekitaran Gas Adi dalam Enjin Pencucuhan Mampatan

Hydrogen fuel promises a high engine efficiency and the ability to eliminate harmful emissions in an internal combustion engine. However, the ignition stability of hydrogen in compression ignition engine is unstable due to the high-auto ignition temperature of hydrogen. Noble gases such as argon, krypton and xenon have a larger molecular weight compared to nitrogen. Therefore, replacing nitrogen with noble gases appears to be a promising option due to their high specific heat ratio. This paper aims to investigate the ignition stability in a heavy molecular noble gases atmosphere in a CI engine. In this study, Converge CFD software simulates a singlecylinder compression ignition engine model based on the Yanmar NF19SK engine parameters. Hydrogen combustion in a noble gas atmosphere resulted in low ignition stability when operated at low intake temperature. Based on this study, we found that increasing intake temperature improves the ignition stability. As a result, argon is the most preferable among other noble gases. Nevertheless, future research should investigate the other noble gases’ capability under different parameters to improve the engine's thermal efficiency.

The in vacuo release of Ar and rare gases from minerals: 3. The degassing of He, Ne, Ar, Kr and Xe from irradiated apatite

The mechanisms of in vacuo release of Ar are investigated by bringing them into context with nine other rare gas isotopes and by studying the mineralogical modifications that occur in their host mineral. A 200 mg shard of Durango fluorapatite was step-heated after neutron irradiation. It contained radiogenic 4He from natural U decay and artificially produced major rare gas isotopes: 20Ne from F, 37Ar from Ca, 38Ar from Cl, 80Kr and 82Kr from Br, 128Xe from I, 131Xe from Ba and 134Xe from U. The 4He release rate was compared with that from an unirradiated aliquot.Helium was expected, and observed, to degas at the lowest furnace temperatures, with nearly complete exhaustion by 1300 °C. Neon followed a bimodal degassing pattern, with a peak of the release rate at 1178 °C and a higher one at 1406 °C. Argon degassing showed a similar bimodality. Krypton and xenon were both mostly released in a single, concentrated burst between 1362 and 1460 °C.The two Xe isotopes 128 and 131, produced from I and Ba, respectively, followed exactly the same degassing pattern. The crystallographic site of the target element had no control on the movement of the irradiation-produced rare gas atom.The He release from the irradiated and unirradiated aliquots gave two overlapping alignments in the Arrhenius diagram at temperatures between 450 and 1300 °C. The two slopes are indistinguishable at the 1 sigma level and yield an average activation energy of 62 ± 5 kJ/mol. In the 450–1300 °C temperature interval, all five rare gases showed parallel trends with an activation energy around 62 kJ/mol and release rate constants decreasing from He to Xe by about 4 orders of magnitude. Arrhenian trajectories for the Kr and Xe degassing rate merge and sharply steepen in the 1362 °C step, with a degassing rate in the 1406 °C step about 400 times higher than at lower temperatures and an activation energy of 1.28 MJ/mol. The high-T modes of the bimodal Ar and Ne release also merge on the same steep Arrhenius line, with release rate constants indistinguishable from those of Kr and Xe. This break in Arrhenius slope and the merger of four trajectories that were widely separated below 1300 °C indicate a major, energetically very costly event between 1300 and 1362 °C.The possible structural reordering was investigated with four mineralogical techniques: Raman spectroscopy, X ray diffractometry, transmission electron microscopy, and microchemical analysis by laser induced breakdown spectroscopy. Total loss of F may have transiently modified the apatite structure. Complete outgassing of Ne, Ar, Kr and Xe was only achieved after the defluorination reaction and attending displacive structural reorganization. Like in hydrated minerals, in K-feldspar, and in leucite, degassing of heavy noble gases in apatite occurs by at least two different physical mechanisms. In all of these minerals downslope extrapolation of in vacuo Ar degassing in the laboratory to temperatures of geological interest does not appear warranted.

The effect of inert gases (Xe, Ar, Ne, He) on decomposition reactions of N2O, CH4 and CO2 at high pressures

In a pulsed compression reactor (PCR) experiments were done with N2O (4%mol), CH4 (1%mol) and CO2 (2%mol) diluted in the inert gases Xe, Ar, Ne and He. The mixtures were compressed up to 250 bar, reaching temperatures of up to 4000 K. At equal temperature, pressure and volume, significant differences (up to 20%) were measured in the conversion of the three species in different noble gases. The measurements with N2O decomposition showed that the reaction is the fastest in the most heavy noble gas tested. The conversion decreased as the molar mass of the noble gas decreased. Likewise, methane pyrolysis was measured to be the fastest in xenon and slowed down in accordance with the mass of the inert molecule. A reverse trend was measured for the decomposition of CO2 to CO and O⋅, which is explained by the dominant role of the reverse reaction. As a result, the CO2 data is also explained by conversion rates that are higher in heavier gases. This paper provides a first attempt to understand the observed influence of the molar mass of the inert bathing gas on the reaction rate in the high pressure domain. A theory is proposed based on a Newtonian description of reactant activation by the inert bathing gas.

Polarization control of RABBITT in noble gas atoms

The mutual angle formed by the non-collinear polarization axes of two laser pulses is used to control two-photon extreme ultraviolet and infrared ionization of noble gas atoms in the process of reconstruction of attosecond bursts by beating of two-photon transitions (RABBITT). The magnitude and the phase of this beating can be controlled very efficiently by the mutual polarization angle. The mechanism of this control can be understood within the lowest order perturbation theory and the soft photon approximation. We offer a very sensitive test on the polarization control of the angular dependent RABBITT process which validates our numerical simulations. We apply this test to the recent theoretical and experimental results of polarization controlled RABBITT on hydrogen and helium by Boll et al (2023 Phys. Rev. A 107 043113) and heavier noble gases by Jiang et al (2022 Nat. Commun. 13 5072).

Investigating noble gases and nitrogen in Zag (H3-6) and ALH 77216 (L3.7–3.9): The ordinary chondrites with solar type neon and argon

Concentrations and isotopic compositions of noble gases (He, Ne, Ar, Kr, and Xe) and nitrogen in two ordinary chondrites (OCs), Zag (H3-6) and ALH 77216 (L3.7–3.9), are presented. The aim of the study is to examine the cosmic ray exposure history, radiogenic ages and isotopic signatures of trapped gases in them. The results of stepwise heating analyses indicate that light noble gases (He and Ne) are mixture of trapped and cosmic ray produced components. Neon isotopes are enriched from solar wind (SW), while shows a trend towards galactic cosmic ray (GCR) region in both the meteorites. Phase-Q neon is not observed in any of the meteorite. The heavy noble gases Ar, Kr and Xe indicate mixture of Q-HL-SW and cosmogenic. Elemental ratios of trapped 36Ar, 84Kr and 132Xe indicate that noble gases in Zag and ALH 77216 are mixtures of the three components Q, HL and SW. The cosmic-ray exposure (CRE) ages calculated from neon for Zag and ALH 77216 are 5.6 ± 0.3 Ma and 28.5 ± 0.4 Ma, respectively. These ages are within the range typically observed for the respective meteorite types of OCs. Nitrogen isotopes indicate presence of multiple components in both the chondrites. Isotopic signature of trapped nitrogen in both the chondrites is distinct from that of SW, Q and HL, indicating additional source of nitrogen in the meteorites.

Dissolved gases in the deep North Atlantic track ocean ventilation processes

Gas exchange between the atmosphere and ocean interior profoundly impacts global climate and biogeochemistry. However, our understanding of the relevant physical processes remains limited by a scarcity of direct observations. Dissolved noble gases in the deep ocean are powerful tracers of physical air-sea interaction due to their chemical and biological inertness, yet their isotope ratios have remained underexplored. Here, we present high-precision noble gas isotope and elemental ratios from the deep North Atlantic (~32°N, 64°W) to evaluate gas exchange parameterizations using an ocean circulation model. The unprecedented precision of these data reveal deep-ocean undersaturation of heavy noble gases and isotopes resulting from cooling-driven air-to-sea gas transport associated with deep convection in the northern high latitudes. Our data also imply an underappreciated and large role for bubble-mediated gas exchange in the global air-sea transfer of sparingly soluble gases, including O2, N2, and SF6. Using noble gases to validate the physical representation of air-sea gas exchange in a model also provides a unique opportunity to distinguish physical from biogeochemical signals. As a case study, we compare dissolved N2/Ar measurements in the deep North Atlantic to physics-only model predictions, revealing excess N2 from benthic denitrification in older deep waters (below 2.9 km). These data indicate that the rate of fixed N removal in the deep Northeastern Atlantic is at least three times higher than the global deep-ocean mean, suggesting tight coupling with organic carbon export and raising potential future implications for the marine N cycle.

Gas Discharge Properties of Inverse-Brush-Electrodes Driven by Alternating Current

The inverse-brush-electrodes (IBE) structure with a large area is designed to investigate the discharge mechanism driven by alternating current (ac). It is found that the IBE structure increases the number of secondary electrons and reduces the breakdown voltage by comparing the discharge processes of IBE and plate electrodes. Meanwhile, the breakdown mechanism of gas discharge driven by ac is analyzed in detail. Additionally, the designed IBE structure has a negative differential conductivity enhancement effect than that of plate electrodes when plasmas are generated in the heavy noble gas. Finally, the negative differential conductivity enhancement phenomenon of the IBE structure is analyzed by experiments and simulations. This effect originates from the non-equilibrium electron energy distribution function (EEDF), which is due to the more suprathermal electrons generated by the IBE structure.

The inert pair effect on heavy noble gases: insights from radon tetroxide.

A quantum chemical survey of radon and xenon tetroxides (NgO4, Ng = Xe, Rn) is reported herein. The intermediate species, which are formed in their explosive decomposition back to their elemental states (Ng and O2), were also studied and their energetics were compared. While Td symmetric RnO4 has a minimum energy structure, its standard enthalpy of formation is 88.6 kJ mol-1 higher than for XeO4. The reason for this higher instability lies in what is known as the inert pair effect. This work establishes that the high-valent chemical trends of the sixth period of groups 13-15 are indeed extended to group 18.

Modification and Mass Loss of Melamine Formaldehyde Particles in Dusty Plasma Formed in Heavy Noble Gas

Modification and Mass Loss of Melamine Formaldehyde Particles in Dusty Plasma Formed in Heavy Noble Gas

Features of the breakdown in heavy noble gases under the action of Novosibirsk free electron laser radiation

The results of experimental studies on the breakdown of noble gases (argon and krypton) by terahertz radiation from the Novosibirsk free electron laser (NovoFEL) are presented. For the first time, the breakdown thresholds of noble gases by terahertz radiation were measured in a wide pressure range (0.2-1.5 bar). Previous experiments to measure breakdown thresholds in the THz range in various gases were carried out for hundreds of GHz or at atmospheric pressure. Experimental breakdown thresholds are compared with calculated data using various simplified models. Keywords: THz radiation, gas breakdown, THz laser discharge.

Discharge of heavy noble gases induced by pulsed gyrotron radiation with 1 THz frequency

In this work, gas discharge ignited by girotron radiation with frequency 1 THz was carried out. Breakdown curves were calculated both for selfignited and initiated discharges. There was shown that in a case of breakdown by the pulse radiation with duration longer than several microseconds electric field threshold is the same as in a case of continuous wave breakdown. Also, the possibility of using a terahertz gyrotron as a radiation source for discharge in gas targets on installations for extreme ultraviolet photolithography was assessed. Keywords: girotron, terahertz breakdown, extreme ultraviolet lithography.

A Thermal Sublimation Generator of 131mXe

Stable and unstable isotopes of the heavy noble gas xenon find use in various medical applications. However, apart from 133Xe, used for Single Photon Emission Computed Tomography, radioactive isotopes of xenon are currently complicated to obtain in small quantities. With the GAMMA-MRI project in mind, we investigated a thermal sublimation generator of the long-lived excited state (isomer) 131mXe. This production method utilized the decay of 131I, obtained commercially from a hospital supplier in the form of Na131I powder. Heat treatments of the Na131I powder and cryogenic trapping of released 131mXe allowed us to collect up to 88% of the produced xenon. Our method provides an isomeric mixture of 131mXe and 131Xe. With improvements in scalability and chemical purification, this method could be a cost-effective source of 131mXe for small-scale experiments.