Noble Gases Xe Research Articles

Frequency-Dependent Quadratic Response Properties and Two-Photon Absorption from Relativistic Equation-of-Motion Coupled Cluster Theory.

We present the implementation of quadratic response theory based upon the relativistic equation-of-motion coupled cluster method. We showcase our implementation, whose generality allows us to consider both time-dependent and time-independent electric and magnetic perturbations, by considering the static and frequency-dependent hyperpolarizability of hydrogen halides (HX, X = F-At), providing comprehensive insights into their electronic response characteristics. Additionally, we evaluated the Verdet constant for noble gases Xe and Rn and discussed the relative importance of relativistic and electron correlation effects for these magneto-optical properties. Finally, we calculate the two-photon absorption cross sections of transition [ns1S0 → (n + 1)s1S0] of Ga+ and In+, which are suggested as candidates for new ion clocks. As our implementation allows for the use of nonrelativistic Hamiltonians as well, we have compared our EOM-QRCC results to the QR-CC implementation in the DALTON code and show that the differences between CC and EOMCC response are in general smaller than 5% for the properties considered. Collectively, the results underscore the versatility of our implementation and its potential as a benchmark tool for other approximated models, such as density functional theory for higher-order properties.

Investigating the Effects of Ag, Cu, and Pd Functionalized Chabazite on the Adsorption Affinities of Noble Gases Xe, Kr, and Ar

Separation of the noble gases from air is typically done through a cryogenic distillation process that is both energy intensive and expensive. Ag-functionalized zeolites and MOFs have a well-documented affinity for Xe and, to a lesser extent, Kr that could serve as an economical alternative to this process on a commercial scale. The mechanism driving the Ag–Xe interaction, however, is still a matter of debate, and the use of other metals in place of Ag is not as thoroughly documented. In this study, Ag, Cu, and Pd functionalized chabazite specimens were prepared, and their affinities for the noble gases Xe, Kr, and Ar were investigated and compared to each other and an unexchanged Na-chabazite. From these analyses, Ag-functionalized chabazite displayed the highest affinity for Xe among these samples, but there was not a similar affinity for Kr or Ar. From the results, a mechanism is proposed such that the strong Ag–Xe interaction contains both an underlying physical and electronic aspect related to the formation of Ag nanoclusters within the chabazite pore geometry that alters the chabazite surface state such that Xe is preferentially adsorbed.

Characteristics of Hydrogen and Oxygen Isotopes and Noble Gas Isotopes in the Groundwater of Weishan, Wudalianchi, Northeast China

AbstractAccording to the hydrochemical characteristics, hydrogen and oxygen isotope characteristics and the ratio of noble gas isotopes of the sandstone aquifer and basalt aquifer, this study calculated the recharge temperature and residence time of groundwater in the Weishan area of Wudalianchi, also calculating the contribution of noble gas components from different sources to the samples. Based on the characteristics of hydrogen and oxygen isotopes and noble gases Xe and Ne, the recharge altitude and recharge temperature of the two aquifers were estimated, and the recharge temperature fitting with the NGT model as verified, the results showing that the main recharge altitude of groundwater in the region was 500–600 m, the recharge temperature being 2–7°C. Heeq and Heea of the samples have been simulated using the OD model, the content of radioactive 4He in the crust being obtained, the groundwater ages under the two conditions (closed condition and open condition) both being simulated. The results show that groundwater from the sandstone layer water is older than groundwater from the basalt layer. Hydrochemical characteristics and noble gas isotope ratios indicate that in the basalt aquifer and sandstone aquifer in the Weishan area, in addition to atmospheric and crustal helium, there is also an input of mantle‐derived helium. The fault constitutes the uplift channel for groundwater containings mantle components, which results in the mantle source composition in water samples near the fault being much higher than those form non‐fault areas.

Placebo-controlled study of xenon effect on the emotions and frequency of the EEG alpha-oscillations

Background: A partial blocker of N-methyl-D-aspartate (NMDA) receptors, the noble gas Xe in sub-anesthetic (2550%) doses performs its neuroprotective effects on the brain structures functions through binding to glycine site. According to the single studies, Xe reveals the thymoleptic properties, which are reflected in the strengthening of positive emotional activation and a decreasing ― negative. The purpose of this placebo-controlled pilot study in healthy volunteers was to evaluate the translational potential of Xe as a possible antidepressant.
 Methods: In placebo-controlled, double-blind study 14 right-handed healthy volunteers (males, right handed) were randomly assigned to 15 min inhalation session either of an admixture of up to a maximum of 25% Xe (25% Хе/30% О2/45% N2) or placebo (70% N2/30% О2) for 15 min. The inspiratory Xe concentration was titrated during the first 5 min until 25% was achieved and maintained for 5 min. Across the study, we had recorded, ECG, SGR, and 64-channel EEG. As a neurophysiological index of the experienced emotion intensity changes individual alpha peak frequency (iAPF) shift was studied. Changes in intensity of experiencing ten discrete emotions (surprise, joy, happiness, bliss, awe, fear, sadness, anxiety, anger, disgust) as indexed by visual analog scales (VAS) were recorded in pre- and post Xe and placebo inhalation conditions. The research received approval of the institutional ethics committee.
 Results: Repeated measures ANOVAs of the emotional reactivity [(GAZ 2: Xe, placebo) CONDITION (2: pre, post) EMOTION (10)] and of the iAPF [(GAZ 2: Xe, placebo) CONDITION: 2 (pre, post) established high significant specific effects of the Xe compared with placebo. The impact of Xe in a sample of examined subjects revealed two types of responses: in one part, an increase in the experiencing positive emotions intensity, accompanied by the rise in iAPF, in the other, insignificant changes in the initial emotional profile with a tendency to decrease in combination with a decrease in iAPF. Thus, in agreement with ad hoc hypothesis, Xe in sub-anesthetic doses induced the enhancement of the positive emotion intensity experience only in those participants who demonstrated the increasing of the iAPF. Correlation and regression analyses revealed a positive correlation of iAPF changes with an intensity of positive emotional activation (increased power of experiencing emotions of joy, happiness, and bliss), as well as the iAPF shift ability to predict the thymoleptic effect of Xe with 74% probability. Additionally, we were able to deduce that individual nature of changes in iAPF and the nature of emotional-reactivity in response to Xe depend on the absolute value of the baseline iAPF.
 Conclusions: We had first established that Xe as a blocker of NMDA receptors in sub-anesthetic doses enhances positive emotional activation (increased intensity of experiencing discrete emotions of joy, happiness, and bliss) in healthy volunteers. The presence or absence of the thymoleptic response to Xe varies due to the individual characteristics of the neurophysiological endophenotype of the EEG alpha activity ― iAPF. The obtained data allow us to consider iAPF as a potential neurophysiological endophenotypic predictor of an individual thymoleptic response to Xe in sub-anesthetic doses in the clinic of the affective disorders. To assess the real Xe translational potential, as a clinical thymoleptic and antidepressant agent, it is necessary to perform large-scale placebo-controlled clinical studies in patients with various clinical forms of negative affect pathology.

Atomic simulation of Xe and Kr separation in silica-templated amorphous mesoporous carbons CMK-3 and CMK-5

We perform a molecular simulation study on adsorption and separation of the noble gases Xe and Kr in silica-templated amorphous mesoporous carbons (CMK) materials. We generate the atomic models of CMK-3 and CMK-5 materials by adsorbing carbon in a model MCM-41 pore. Our carbon structures can capture the surface roughness and the disordered nature of the carbon rods and carbon pipes as reported in the experiment. The adsorption isotherms and isosteric heats of pure gases have been examined further. We find that the existence of the carbon interconnections between nanorods for CMK-3 and between nanopipes for CMK-5 will reduce the excess uptakes of the noble gases, whereas the isosteric heats are favoured in the materials with interconnections. The carbon interconnections are not advantageous to the adsorption storage of pure gases, but they can improve the separation ability of Xe for gas-mixture adsorption. The effects of temperature and concentration on the Xe separation are investigated and it is shown that the selectivities of Xe in the CMK-5 materials are insensitive to the two factors. We also find that both gas storage and separation of CMK materials are comparable to IRMOF-1 and UMCM-1 metal-organic frameworks.

Adsorption properties of fission gases Xe and Kr on pristine and doped graphene: A first principle DFT study

Graphene has excellent adsorption properties due to large surface area and has been used in applications related to gas sorption and separation. The separation of radioactive noble gases using graphene is an interesting area of research relevant to nuclear waste management. Radioactive noble gases Xe and Kr are present in the off-gas streams from nuclear fission reactors and spent nuclear fuel reprocessing plants. The entrapment of these volatile fission gases is important in the context of nuclear safety. The separation of Xe from Kr is extremely difficult, and energy intensive cryogenic distillation is generally employed. Physisorption based separation techniques using porous materials is a cost effective alternative to expensive cryogenic distillation. Thus, adsorption of noble gases on graphene is relevant for fundamental understanding of physisorption process. The properties of graphene can be tuned by doping and incorporation of defects. In this regard, we study the binding affinity of Xe and Kr in pristine and doped graphene sheets. We employ first principle calculations using density functional theory, corrected for dispersion interactions. The structural parameters obtained from the current study show excellent agreement with the available theoretical and experimental observations on similar systems. Noble gas adsorption energies on pristine graphene match very well with the available literature. Our results show that the binding energy of fission gases Xe and Kr on graphene can be considerably improved through doping the lattice with a heteroatom.

Gold-superheavy-element interaction in diatomics and cluster adducts: A combined four-component Dirac-Kohn-Sham/charge-displacement study.

The chemistry of superheavy elements (Z ≥ 104) is actively investigated in atom-at-a-time experiments of volatility through adsorption on gold surfaces. In this context, common guidelines for interpretation based on group trends in the periodic table should be used cautiously, because relativistic effects play a central role and may cause predictions to fall short. In this paper, we present an all-electron four-component Dirac-Kohn-Sham comparative study of the interaction of gold with Cn (Z = 112), Fl (Z = 114), and Uuo (Z = 118) versus their lighter homologues of the 6th period, Hg, Pb, and Rn plus the noble gas Xe. Calculations were carried out for Au-E (E = Hg, Cn, Pb, Fl, Xe, Rn, Uuo), Au7- and Au20-E (E = Hg, Cn, Pb, Fl, Rn) complexes, where Au7 (planar) and Au20 (pyramidal) are experimentally determined clusters having structures of increasing complexity. Results are analysed both in terms of the energetics of the complexes and of the electron charge rearrangement accompanying their formation. In line with the available experimental data, Cn and more markedly Fl are found to be less reactive than their lighter homologues. On the contrary, Uuo is found to be more reactive than Rn and Xe. Cn forms the weakest bond with the gold atom, compared to Fl and Uuo. The reactivity of Fl decreases with increasing gold-fragment size more rapidly than that of Cn and, as a consequence, the order of the reactivity of these two elements is inverted upon reaching the Au20-cluster adduct. Density difference maps between adducts and fragments reveal similarities in the behaviour of Cn and Xe, and in that of Uuo and the more reactive species Hg and Pb. These findings are given a quantitative ground via charge-displacement analysis.

Adsorption and Separation of Xe in Metal–Organic Frameworks and Covalent–Organic Materials

We use grand canonical Monte Carlo simulations to investigate adsorption and separation of metal–organic frameworks and covalent–organic materials for the noble gas Xe. Results indicate that PAF-302 among these materials studied shows not only the highest gravimetric excess uptake of 4009 mg/g but also the largest volumetric uptake of 216 V(STP)/V, due to its large pore size and high accessible surface area. The gravimetric excess uptake of Xe at intermediate pressure follows the order of PAF-302 > UMCM-1 > IRMOF-1 > Cu-BTC > COP-4 > ZIF-8, which is entirely consistent with the accessible surface areas. Moreover, the maximum gravimetric excess uptakes of Xe in different materials exhibit an entirely linear correlation with the accessible surface area. However, at low pressure of p ZIF-8 > COP-4 > IRMOF-1 > UMCM...

A combined surface stress and magneto-optical Kerr effect measurement setup for temperatures down to 30 K and in fields of up to 0.7 T

An optical 2-beam surface stress measurement and magneto-optical Kerr-effect has been combined with a liquid helium cooled cryostat. Sample temperatures down to 30 K and magnetic fields up to 0.7 T are achieved under UHV conditions. Low temperatures are exploited to obtain the first experimental data on the surface stress change induced by the adsorption of the noble gas Xe on Pt(111). High magnetic fields and low temperatures are used to characterize the magnetic properties of Co monolayers in longitudinal and polar Kerr geometries. The effective magnetic anisotropy is extracted from hard axis magnetization loops.

Ligand Migration and Cavities within Scapharca Dimeric HbI: Studies by Time-Resolved Crystallo- graphy, Xe Binding, and Computational Analysis

As in many other hemoglobins, no direct route for migration of ligands between solvent and active site is evident from crystal structures of Scapharca inaequivalvis dimeric HbI. Xenon (Xe) and organic halide binding experiments, along with computational analysis presented here, reveal protein cavities as potential ligand migration routes. Time-resolved crystallographic experiments show that photodissociated carbon monoxide (CO) docks within 5 ns at the distal pocket B site and at more remote Xe4 and Xe2 cavities. CO rebinding is not affected by the presence of dichloroethane within the major Xe4 protein cavity, demonstrating that this cavity is not on the major exit pathway. The crystal lattice has a substantial influence on ligand migration, suggesting that significant conformational rearrangements may be required for ligand exit. Taken together, these results are consistent with a distal histidine gate as one important ligand entry and exit route, despite its participation in the dimeric interface.

Xenon in mercury–manganese stars

Previous studies of elemental abundances in mercury-manganese (HgMn) stars have occasionally reported the presence of lines of the ionized rare noble gas Xe II, especially in a few of the hottest stars with T eff ∼ 13 000-15 000 K. A new study of this element has been undertaken using observations from Lick Observatory's Hamilton Echelle Spectrograph. In this work, the spectrum synthesis program UCLSYN has been used to undertake abundance analysis assuming local thermodynamic equilibrium. We find that in the Smith & Dworetsky sample of HgMn stars, Xe is vastly overabundant in 21 of 22 HgMn stars studied, by factors of 3.1-4.8 dex. There does not appear to be a significant correlation of Xe abundance with T eff . A comparison sample of normal late B stars shows no sign of Xe II lines that could be detected, consistent with the expected weakness of lines at normal abundance. The main reason for the previous lack of widespread detection in HgMn stars is probably due to the strongest lines being at longer wavelengths than the photographic blue. The lines used in this work were λ4603.03, λ4844.33 and λ5292.22.

K-edge x-ray absorption spectra of Cs and Xe

X-ray absorption spectrum of cesium vapor in the K-edge region is measured in a stainless steel cell. The spectrum is free of the x-ray absorption fine structure signal and shows small features analogous to those in the spectrum of the neighbor noble gas Xe. Although the large natural width of the K vacancy $(g10\mathrm{eV})$ washes out most of the details, fingerprints of multielectron excitations can be recognized at energies close to Dirac-Fock estimates of doubly excited states $1s4(d,p,s)$ and $1s3(d,p).$ Among these, the $1s3p$ excitation 1000 eV above the K edge in both spectra is the deepest double excitation observed so far. Within the K-edge profile, some resolution is recovered with numerical deconvolution of the spectra, revealing the coexcitation of the $5(p,s)$ electrons, and even the valence $6s$ electron in Cs. As in homologue elements, three-electron excitations, either as separate channels or as configuration admixtures are required to explain some spectral features in detail.

Thermodynamic analysis of chemical states of fission products in uranium–zirconium hydride fuel

The chemical state of fission products (FPs) in U+ZrH 1.60 fuel was studied from the thermodynamic point of view. Twenty most abundant FP elements were taken into account in the system of U–Zr–H–O–FP in which oxygen is treated as an impurity. The Thermo-Calc computer code was used to calculate the equilibrium state of the multi-phase and multi-component system. This calculation shows that yttrium, the alkaline earth metals (Ba, Sr) and most of the lanthanides prefer to form corresponding binary hydrides. Oxygen impurities in the system are likely to form a mixture of Y 2O 3, Pr 2O 3, Sm 2O 3 as well as Ce 2O 3 depending on their fission yields. With increasing of burn-up, only a slight decrease of the hydrogen potential in the fuel pin can be expected because of the very little consumption of hydrogen in the hydrogenation process of the FP. In the gas phase, H 2, Cs, Rb, CsRb as well as CsI are the main vapor species apart from the noble gases Xe and Kr. Solid swelling of the fuel due to formation of condensed phases was calculated as a function of burn-up.

De-excitation of O(5S) metastables in inelastic collisions with noble gases

De-excitation of metastable O(5S) atoms in inelastic two-body collisions with inert gas atoms was observed. The cross section for the ground state product reaction was measured for metastable energies from about 0.5 eV to roughly 10 eV in the laboratory frame. For the heavy noble gases Xe and Kr, the cross section rose steeply from threshold to peak values of about 2-3*10-17 cm2 from where it decreased slightly in the case of Xe and steeply for Kr. Corresponding peak values for Ar were at least a factor of 30 smaller. No inelastic signal could be detected with Ne. The excited state product process involved several excited states for each rare gas. The summed cross sections for these inelastic processes were of the order of 10-16 cm2 for Xe and Kr.