Xe Interaction Research Articles

Unveiling the Inverse Sandwich Complexes of XeO3: A Computational Exploration.

Our study introduces the design of inverse sandwich (iSw) complexes incorporating a noble gas compound: xenon trioxide (XeO3). Through comprehensive computational analyses, we have investigated the critical factors influencing their stability by employing a variety of state-of-the-art computational tools. We demonstrated that the coordination number of xenon in the iSw complex of XeO3 with 18-crown-6 is influenced by the presence of a rare, weakly stabilizing Xe···Xe interaction between the XeO3 molecules. Furthermore, we observed that the stability of iSw complexes of 1,3,5-triphenylbenzene (TPB) and its derivatives is not solely attributed to aerogen bonding, but also involves contributions from C-H···O interactions and back-donation from the lone pair of Xe to the antibonding C-C orbitals of TPB. Additionally, the significant contributions from orbital interactions and dispersion interactions in the TPB derivatives highlight the multifaceted amphoteric properties of XeO3 and reveal that the iSw complexes of TPB and derivatives are not predominantly governed by electrostatic interactions, contrary to conventional belief.

3D ultra-micropore organic polymers with fixed group and thieno[3,2-b]thiophene to enhance adsorption and separation of Xe/Kr

The reduction of environmental pollution and the exploration of economic values require the efficient separation and purification of xenon (Xe) and krypton (Kr) from radioactive gases generated during nuclear fission processes. To address this issue, we have synthesized three thieno[3,2-b]thiophene-based porous organic polymers (POP-ch-ET, POP-ch-SP and POP-ch-ME) via high yield C–H direct arylation reaction, all of which exhibited excellent thermal and acid-base stability. Notably, the three-dimensional (3D) structures of POP-ch-SP and POP-ch-ME allowed higher Xe capacity compared to the two-dimensional (2D) structure of POP-ch-ET. Density functional theory (DFT) calculations confirmed that thieno[3,2-b]thiophene moieties contributed to a more negative adsorption energy for Xe than benzene. Among them, POP-ch-SP with fixed group showed superior Xe capacity (2.37 mmol/g) at 298 K and 1.0 bar and the highest ideal adsorption solution theory (IAST) selectivity (11.5). This superior performance is attributed to its 3D ultra-micropore structure, which enables closer proximity between aromatic rings, thereby enhancing Xe interaction. The DFT calculation further revealed that the adsorption energy of Xe in POP-ch-SP was more negative compared to other POPs, indicating a stronger interaction. In addition, POP-ch-SP exhibited the largest ΔQst (14.2 kJ/mol) between Xe and Kr, highlighting a marked affinity difference. In dynamic breakthrough experiments, POP-ch-SP demonstrated robust Xe/Kr separation efficiency under both low (400 ppm Xe and 40 ppm Kr in dry air) and high concentration scenarios (Xe/Kr, v/v, 20/80), underscoring its promising potential for practical applications in radioactive gas management.

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.

Construction of a Magnetic Bottle Electron Spectrometer for Electron Energy Measurement in BISER X-Rays and Xe Interaction

Construction of a Magnetic Bottle Electron Spectrometer for Electron Energy Measurement in BISER X-Rays and Xe Interaction

Particle simulation of an anode-layer Hall thruster plume using an anisotropic scattering model

The large-angle scattered ions are generated in the plasma plume mainly due to the ion-atom collisions. These ions can induce thrust loss, backflow, or sputtering on the spacecraft. It is necessary, therefore, to give an accurate prediction of ion movement for the study on electric propulsions. In the present work, a particle simulation procedure, which includes (1) a Direct Simulation Monte Carlo method and (2) a particle-in-cell method with a Monte Carlo collisions technique coupled with an anisotropy scattering model, is applied to simulate the plume of a D55 anode-layer Hall thruster. The effective Xe+-Xe and Xe2+-Xe interaction potentials are employed to simulate the ion-atom scattering. The electron properties are obtained via a Boltzmann relation and a model that utilizes conservation-law-type equations, respectively. Comparisons are made between the experimental data together with the simulation results from the anisotropy model and those from an isotropic scattering model to analyze their disparities. Results show that, compared with the isotropic model, the electron number density from the anisotropy model matches better with the experimental data. However, the differences in ion current density, plasma potential, and electron temperature between the two scattering models are insignificant. The anisotropy model can give a more accurate prediction of the ion energy distribution, resulting from its more reasonable hypothesis than the isotropic model. For different electron models, the computed results from one using conservation-law-type equations are in better agreement with the measurements than a simple Boltzmann relation.

An effective Xe+–Xe interaction potential for electric propulsion systems

An effective Xe+–Xe interaction potential for electric propulsion systems is proposed based on both spin–orbit free interaction potentials and the screened-Coulomb potential. The model not only conforms with the potential obtained by an ab initio method at large internuclear distances but also matches well with the potential derived from experimental scattering data at short internuclear distances. The scattering angles and differential cross sections computed by the effective potential are in good agreement with those obtained by the Morse potential in low-energy regions and those via two screened-Coulomb potentials (the Ziegler–Biersack–Littmark and Zinoviev potential) in high-energy regions, respectively. To further validate the effective potential, a particle-in-cell method with a Monte Carlo collisions technique, coupled with a direct method for solving the scattering equation, was applied to simulate the collisions of 1500-eV and 7000-eV single-charged xenon ions with background xenon atoms in a test cell. The simulated currents on the inner cylinder, exit plate, exit orifice, and front plate are calculated by different potentials. Results show that the effective potential can give a good prediction of the Xe+–Xe elastic collisions in the wider energy region compared with the Morse, Ziegler–Biersack–Littmark, and Zinoviev potentials.

Genotype X Environment Interaction for Yield of Pickling Cucumber in 24 U.S. Environments

Abstract Reliable yield performance is important in cucumber because seed companies prefer to market cultivars adapted to multiple rather than single regions of the U.S. Also, growers benefit by using a cultivar that performs well in many environments. Future performance of cultivars is also important. The objectives of the study were to (i) evaluate the yield of cucumber genotypes over successive years and in different locations, and (ii) identify cucumber genotypes with high stability for yield. A diverse set of 22 pickling genotypes was evaluated over 3 years (1986, 1987 and 1988) and in 7 locations across the United States. Yield traits were evaluated using once-over harvest and counting the number of fruit that were marketable, culled or oversize. Total yield, marketable yield (total minus culled fruit), early yield (number of oversize fruit), percent culls and fruit per plant were calculated. Data were analyzed with SASGxE and RGxE programs using SAS and R programming languages, respectively. There were strong effects of environment(E) as well as genotype(G) xE interaction for all traits. Genotypes ‘Regal F1’, ‘Calypso F1’, ‘Carolina F1’, ‘Gy 3’, ‘Gy 14’ and ‘Fremont F1’ had high marketable yield and medium to high stability for all traits. There was an advantage of hybrids over inbreds for trait performance. Hybrids fell into a single cluster with large prediction intervals. Based on the stability statistics and divisive clusters, it appears possible to breed stable cucumber genotypes with high yield. The genotype with highest performance for marketable yield, greatest stability for yield, lowest 1-R2 ratio value (diverse and representative) were ‘Marbel F1’ and Gy 14.

G XE Interaction and ammi biplot analysis of harvest index and test grain weight in direct seeded basmati rice

G XE Interaction and ammi biplot analysis of harvest index and test grain weight in direct seeded basmati rice

Programming A Molecular Relay for Ultrasensitive Biodetection through 129Xe NMR

AbstractA supramolecular strategy for detecting specific proteins in complex media by using hyperpolarized 129Xe NMR is reported. A cucurbit[6]uril (CB[6])‐based molecular relay was programmed for three sequential equilibrium conditions by designing a two‐faced guest (TFG) that initially binds CB[6] and blocks the CB[6]–Xe interaction. The protein analyte recruits the TFG and frees CB[6] for Xe binding. TFGs containing CB[6]‐ and carbonic anhydrase II (CAII)‐binding domains were synthesized in one or two steps. X‐ray crystallography confirmed TFG binding to Zn2+ in the deep CAII active‐site cleft, which precludes simultaneous CB[6] binding. The molecular relay was reprogrammed to detect avidin by using a different TFG. Finally, Xe binding by CB[6] was detected in buffer and in E. coli cultures expressing CAII through ultrasensitive 129Xe NMR spectroscopy.

Programming A Molecular Relay for Ultrasensitive Biodetection through (129)Xe NMR.

A supramolecular strategy for detecting specific proteins in complex media by using hyperpolarized (129) Xe NMR is reported. A cucurbit[6]uril (CB[6])-based molecular relay was programmed for three sequential equilibrium conditions by designing a two-faced guest (TFG) that initially binds CB[6] and blocks the CB[6]-Xe interaction. The protein analyte recruits the TFG and frees CB[6] for Xe binding. TFGs containing CB[6]- and carbonic anhydrase II (CAII)-binding domains were synthesized in one or two steps. X-ray crystallography confirmed TFG binding to Zn(2+) in the deep CAII active-site cleft, which precludes simultaneous CB[6] binding. The molecular relay was reprogrammed to detect avidin by using a different TFG. Finally, Xe binding by CB[6] was detected in buffer and in E. coli cultures expressing CAII through ultrasensitive (129) Xe NMR spectroscopy.

Transferability and accuracy by combining dispersionless density functional and incremental post-Hartree-Fock theories: Noble gases adsorption on coronene/graphene/graphite surfaces.

The accuracy and transferability of the electronic structure approach combining dispersionless density functional theory (DFT) [K. Pernal et al., Phys. Rev. Lett. 103, 263201 (2009)] with the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)], are validated for the interaction between the noble-gas Ne, Ar, Kr, and Xe atoms and coronene/graphene/graphite surfaces. This approach uses the method of increments for surface cluster models to extract intermonomer dispersion-like (2- and 3-body) correlation terms at coupled cluster singles and doubles and perturbative triples level, while periodic dispersionless density functionals calculations are performed to estimate the sum of Hartree-Fock and intramonomer correlation contributions. Dispersion energy contributions are also obtained using DFT-based symmetry-adapted perturbation theory [SAPT(DFT)]. An analysis of the structure of the X/surface (X = Ne, Ar, Kr, and Xe) interaction energies shows the excellent transferability properties of the leading intermonomer correlation contributions across the sequence of noble-gas atoms, which are also discussed using the Drude oscillator model. We further compare these results with van der Waals-(vdW)-corrected DFT-based approaches. As a test of accuracy, the energies of the low-lying nuclear bound states supported by the laterally averaged X/graphite potentials (X = (3)He, (4)He, Ne, Ar, Kr, and Xe) are calculated and compared with the best estimations from experimental measurements and an atom-bond potential model using the ab initio-assisted fine-tuning of semiempirical parameters. The bound-state energies determined differ by less than 6-7 meV (6%) from the atom-bond potential model. The crucial importance of including incremental 3-body dispersion-type terms is clearly demonstrated, showing that the SAPT(DFT) approach effectively account for these terms. With the deviations from the best experimental-based estimations smaller than 2.3 meV (1.9%), the accuracy of the combined DFT and post-HF incremental scheme is established for all the noble-gas atoms. With relative deviations smaller than 4% and 11%, good agreement is also achieved by applying the vdW-corrected DFT treatments PBE-D3 and vdW-DF2 for noble-gas atoms heavier than neon.

FTIR investigation of the O–H···Xe interaction in simple carboxylic acids in solid xenon

The O-H stretching region of the infrared spectra of a series of carboxylic acids in Xe matrices was investigated as a function of temperature. Upon increasing the temperature, the νO-H band site-components undergo reversible frequency blue-shifts, which are larger for the lowest-frequency components. This unprecedented observation indicates both that different types of O-H···Xe specific interactions occur, depending on different trapping sites, and the prevalence of stronger interactions of this type for molecules trapped in sites corresponding to lower frequency νO-H band site-components. These results are in agreement with previous investigations pointing to an increased stabilization and larger νO-H frequency red-shifts in carboxylic acid∕Xe complexes bearing a specific H-bond like O-H···Xe interaction. O-H···Xe interaction energies were obtained theoretically and also estimated from the spectroscopic data. Changes in the interaction energies upon temperature variation were also evaluated.

Matrix-isolation and ab initio study of the complex between formic acid and xenon

We report on the identification of the complexes of formic acid (FA) and Xe in an argon matrix. The geometries, interaction energies, reaction barriers, and vibrational spectra of the FA⋯Xe complexes are calculated at the MP2 level of theory. The calculations reveal four structures for the trans-FA⋯Xe complex and four structures for the cis-FA⋯Xe complex. In the experiments, two structures of the trans-FA⋯Xe complex are observed after deposition of FA/Xe/Ar matrices, with and without OH⋯Xe interaction (H-bonded and non-H-bonded structures). The cis-FA⋯Xe complex was synthesized by vibrational excitation of the non-H-bonded trans-FA⋯Xe complex. The non-H-bonded and H-bonded structures of the cis-FA⋯Xe complex are observed after the excitation. The decay of the H-bonded and non-H-bonded cis-FA⋯Xe complexes in an argon matrix is, respectively, substantially slower and faster compared to the cis-FA monomer. This observation is explained by the different tunnelling barriers for these species.

Radiative lifetime of the v′1(3 P 2) states of the HgAr, HgKr, and HgXe molecules and the probabilities A(v′, v″) of the v′1(3 P 2−v″0+(1 S 0) transitions

A semiempirical method of analysis of quasi-molecular terms in conjunction with experimental potentials of interaction of Hg(6(3P1)) atoms with Ar, Kr, and Xe atoms are used to obtain the Hg(63P2)-Ar, Kr, Xe interaction potential, which are applied to calculating the radiative lifetimes of the v′1(3P2) states of the HgAr, HgKr, and HgXe molecules and the probabilities of the v′1(3P2)−v″0+(1S0) transitions.

Noble Gas Atoms as Electron Donors: Is the Stabilization of Strongly Electrophilic Borylnitrenes Feasible?

AbstractThe possible interaction between an electrophilic borylnitrene, CatBN (Cat = Catecholato), with the noble gas atoms Rg (Rg = Kr, Xe) is probed by computational chemistry techniques including hybrid density functional (B3LYP), second‐order Møller–Plesset perturbation (MP2), and coupled‐cluster theory with singles, doubles, and a perturbative estimate of triple excitations [CCSD(T)] in conjunction with aug‐cc‐pVDZ and cc‐pVTZ and the corresponding small‐core pseudopotential correlation consistent basis sets for krypton and xenon. In the triplet manifold the interaction between CatBN and Rg is of the van der Waals type with a small N–Rg bond dissociation energy. In contrast, the singlet CatBNRg(1A′) has a short N–Rg distance (Kr: 1.962 Å; Xe: 2.029 Å) in agreement with a single bond character. The N–Xe bond dissociation energy is 17 kcal·mol–1 at the highest level of theory, while the N–Kr bond is significantly weaker. Experiments in xenon or xenon doped argon matrices do not give any indication for the formation of the CatBNXe(1A′) compound in spite of the strong N–Xe interaction predicted by theory. The experimental observation is explained by the existence of a crossing of singlet and triplet potential energy surfaces. At the geometry of triplet CatBNRg (large N–Rg distance) the singlet state is higher in energy whereas at the geometry of singlet CatBNRg (short N–Rg distance) the triplet is higher. Fast intersystem crossing to the lower lying triplet surface in the presence of Xe is assumed to preclude the formation of CatBNXe(1A′).

Large-angle xenon ion scattering in Xe-propelled electrostatic thrusters: differential cross sections

Elastic scattering between xenon ions and xenon atoms can produce ion currents at large angles with respect to the axis of electrostatic thrusters. Differential scattering cross sections are needed to properly predict off-axis currents that can cause significant material erosion due to sputtering. Guided-ion beam differential cross section measurements are presented for Xe+ + Xe and Xe2+ + Xe elastic scattering at laboratory ion energies between 5 and 40 eV per ion charge. For the singly charged system, the experimental absolute differential cross sections are in excellent agreement with classical elastic scattering calculations based on the most recent ab initio ion–atom interaction potentials. The measurements for the doubly charged system are used to derive an approximate effective Xe2+–Xe interaction potential. The potentials are used to calculate absolute differential cross sections for both ion charge states at a typical Hall thruster ion energy of 270 eV per unit charge. The differential cross sections for the doubly charged ions are approximately a factor of 3 smaller than those of the singly charged system at large scattering angles. The importance of doubly charged ions with respect to material erosion is discussed on the basis of known sputtering yields as a function of ion energy for molybdenum and boron nitride. It is concluded that at typical charge-state ratios, doubly charged ions only have an impact at elastic scattering angles where the scattered ion energy in the laboratory (thruster) frame of reference is low and the sputtering yields depend very strongly on ion kinetic energy.

Density Functional Theoretical Studies of the Re−Xe Bonds in Re(Cp)(CO)(PF3)Xe and Re(Cp)(CO)2Xe

Density functional calculations have been used to probe the electronic structures of Re(Cp)(CO)2Xe and Re(Cp)(CO)(PF3)Xe. The calculated CO stretching frequencies compare favorably with those determined experimentally. Our calculations of δXe and 3JXe-F for Re(Cp)(CO)(PF3)Xe represent the first for a well-characterized transition metal−noble gas compound and demonstrate that DFT using the BP86 and SAOP functionals reproduces these parameters to within 1% and 8% of their experimentally determined values. The calculated Re−Xe bond dissociation energies for Re(Cp)(CO)2Xe (12.3 kcal mol-1) and Re(Cp)(CO)(PF3)Xe (11.9 kcal mol-1) are also in excellent agreement with the lower limits for these energies estimated from the activation parameters for the reaction of the complexes with CO in supercritical Xe. A topological analysis of the electron density in Re(Cp)(CO)2Xe and Re(Cp)(CO)(PF3)Xe reveals positive ∇2ρ(r) at the critical points (∇2ρ(rc) = 0.1310 and 0.1396 e Å5 for Re(Cp)(CO)2Xe and Re(Cp)(CO)(PF3)Xe, respectively, indicating that the Re−Xe interaction is essentially closed-shell in both complexes. Fragment and overlap density of states analyses show that the orbital interactions in these compounds is dominated by overlap involving the Xe p orbitals and the orbitals of the Cp, CO, and/or PF3 ligands; the Re d orbitals appear to contribute little to the orbital interactions between the Re(Cp)(CO)2 and Re(Cp)(CO)(PF3), and Xe fragments.

The ordering of a Xe monolayer on quasicrystalline Al–Ni–Co

The ordering of physically adsorbed gases on quasicrystalline surfaces exemplifies the effects of competing interactions. In this study, grand canonical Monte Carlo simulations were performed to complement experimental measurements of the ordering of Xe adsorbed on the tenfold surface of decagonal Al–Ni–Co. The simulations employed a semi-empirical gas-surface interaction, based on conventional combining rules, and the Lennard–Jones Xe–Xe interaction. The simulation results are consistent with the experiment and provide a new insight into the ordering behavior. The film initially has a fivefold quasicrystalline symmetry, but it evolves into a close-packed structure during adsorption of the second layer. The presence of symmetry defects in the sixfold structure creates domains of Xe having different (but equivalent) rotational epitaxy, suggesting that even in the absence of substrate defects, the annealed film has the five different rotational alignments observed in the experimental studies.

129Xe NMR investigation of catalytic filamentous carbon

A series of catalytic filamentous carbons (CFC) obtained from gas phase reaction on iron subgroup metal catalysts was studied by 129Xe NMR. A connection between 129Xe NMR parameters and structural, textural and paramagnetic properties of CFC was discussed. The chemical shift ( δ) was shown to depend on the structure of the CFC surface formed by edge, basal or both (edge and basal) graphite faces. This dependence follows a general trend of the chemical shift to increase with adsorption potential of a surface. The term describing Xe–Xe interaction ( δ Xe–Xe) in confined space decreased with the average pore size of CFC granule. For hollow multi-wall carbon nanotubes two 129Xe NMR signals were attributed to voids inside nanotubes and to interstices between the interlaced nanotubes. However, analysis of experimental data is complicated due to the presence of paramagnetic metal particles necessary to the filament growth. Therefore, ESR data are given and correlated with 129Xe NMR results.

An oblique-incidence optical reflectivity difference and LEED study of rare-gas growth on a lattice-mismatched metal substrate

We studied the growth of Xe on Nb(110) from 33 K to 100 K using a combination of low-energy electron diffraction and an in situ oblique-incidence optical reflectivity difference technique. We found that a hexagonal close-packed Xe film grows after a transition layer of three monoatomic layers thick is formed. The first two monolayers, influenced by both the interaction with the Nb substrate and the Xe–Xe interaction, lack long-range order. The third monolayer forms a bulk-like hexagonal close-packed structure. Subsequently a bulk-phase Xe(111) film grows in step-flow mode from 54 K down to 40 K. At 40 K, we observed a brief crossover to a layer-by-layer mode. At 33 K the growth proceeds in a kinetically limited multilayer or a three-dimensional island mode.