XeO4 Research Articles

Universal Research Cryogenic Unit for Xenon Production

Xenon is a cryogenic product that is currently in short supply. Requirements for its purity are increasing. Its consumption in microelectronics, medicine, and space technology and for high-energy particle physics research is rising. The permissible impurity contents in Xe for various applications were analyzed. A universal research cryogenic unit for Xe production of throughput up to 10 Nm3/h of feedstock mixture was designed. A scheme with separation by rectification and preliminary catalytic and adsorptive purification of the feedstock was chosen. The unit was built in blocks so that processing schemes for Xe production from various mixtures, e.g., Kr–Xe, Xe–N2, Xe–O2, could be studied. Trace impurities in Xe were analyzed by gas chromatographs with thermal conductivity (TCD), He-ionization (HID), and flame-ionization detectors (FID). Water vapor in the analyzed gases was measured using laseroptical and coulometric hygrometers. The first runs showed that the unit could produce Xe of purity up to 99.9999 %. Experimental data for rectification of Xe to a purity of 99.999 % are presented. Xe could be purified experimentally from traces of CF4, C2F6, SF6, hydrocarbons, CO2, and H2 to 0.05; O2 and N2, 0.1; Kr, 0.01; and water vapor, 0.2 ppm.

Establishing an accurate gas phase reference frequency to quantify 129 Xe chemical shifts in vivo.

129 Xe interacts with biological media to exhibit chemical shifts exceeding 200 ppm that report on physiology and pathology. Extracting this functional information requires shifts to be measured precisely. Historically, shifts have been reported relative to the gas-phase resonance originating from pulmonary airspaces. However, this frequency is not fixed-it is affected by bulk magnetic susceptibility, as well as Xe-N2 , Xe-Xe, and Xe-O2 interactions. In this study, we addressed this by introducing a robust method to determine the 0 ppm 129 Xe reference from in vivo data. Respiratory-gated hyperpolarized 129 Xe spectra from the gas- and dissolved-phases were acquired in four mice at 2T from multiple axial slices within the thoracic cavity. Complex spectra were then fitted in the time domain to identify peaks. Gas-phase 129 Xe exhibited two distinct resonances corresponding to 129 Xe in conducting airways (varying from -0.6 ± 0.2 to 1.3 ± 0.3 ppm) and alveoli (relatively stable, at -2.2 ± 0.1 ppm). Dissolved-phase 129 Xe exhibited five reproducible resonances in the thorax at 198.4 ± 0.4, 195.5 ± 0.4, 193.9 ± 0.2, 191.3 ± 0.2, and 190.7 ± 0.3 ppm. The alveolar 129 Xe resonance exhibits a stable frequency across all mice. Therefore, it can provide a reliable in vivo reference frequency by which to characterize other spectroscopic shifts. Magn Reson Med 77:1438-1445, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Ultraviolet photolysis studies on XeO4 in noble-gas and F2 matrices and the formation and characterization of a new Xe(VIII) oxide, (η(2) -O2 )XeO3.

The photolytic behavior of the thermochemically unstable xenon(VIII) oxide XeO4 was investigated by UV irradiation in noble-gas and F2 matrices. Photolysis of Xe(16) O4 or Xe(18) O4 in noble-gas matrices at 365 nm yielded XeO3 and a new xenon(VIII) oxide, namely, (η(2) -O2 )XeO3 , which, along with XeO4 , was characterized by matrix-isolation IR spectroscopy and quantum-chemical calculations. Calculations of the UV spectrum showed that the photodecomposition is induced by an n→σ* transition, but the nature of the excitation differs when different light sources are used. There is strong evidence for the formation of mobile (1) D excited O atoms in the case of excitation at 365 nm, which led to the formation of (η(2) -O2 )XeO3 by reaction with XeO4 . Matrix-isolation IR spectroscopy in Ne and Ar matrices afforded the natural-abundance xenon isotopic pattern for the ν3 (T2 ) stretching mode of Xe(16) O4 , and (18) O enrichment provided the (16) O/(18) O isotopic shifts of XeO4 and (η(2) -O2 )XeO3 .

Spontaneous Dissociation of Xenon Tetroxide: Phase and Structural Changes

XeO(4) is a noble gas compound remarkable for its high explosiveness in the crystalline state and spontaneous explosion at melting temperature. Both phenomena are studied by analyzing potential energy surfaces corresponding to elementary dissociation acts. It is shown that a spontaneous explosion of xenon tetroxide can be explained by a phase transition associated with structural T(d) → D(2h) change and be triggered by rearrangement of electron levels due to the Jahn-Teller effect.

Experimental measurement of the van der Waals binding energy of X–O2 clusters (X=Xe,CH3I,C3H6,C6H12)

Van der Waals binding energies for the X-O(2) complexes (X=Xe, CH(3)I, C(3)H(6), C(6)H(12)) are determined by analysis of experimental velocity map imaging data for O((3)P(2)) atoms arising from UV-photodissociation of the complex [A. V. Baklanov et al., J. Chem. Phys. 126, 124316 (2007)]. Several dissociation pathways have been observed, we focus on the channel corresponding to prompt dissociation of X-O(2) into X+2O((3)P) fragments, which is present for complexes of O(2) with all partners X. Our method is based on analysis of the kinetic energy of all three photofragments, where the O atom kinetic energy was directly measured in the experiment and the kinetic energy of the X partner was calculated using momentum conservation, along with the measured angular anisotropy for O atom recoil. We exploit the fact that the clusters are all T-shaped or nearly T-shaped, which we also confirm by ab initio calculations, along with knowledge of the transition dipole governing radiative absorption by the complex. The effect of partitioning the kinetic energy between translation along the X-O(2) and O-O coordinates on the angular anisotropy of the O atom recoil direction is discussed. Van der Waals binding energies of 110±20 cm(-1), 280±20 cm(-1), 135±30 cm(-1), and 585±20 cm(-1) are determined for Xe-O(2), CH(3)I-O(2), C(3)H(6)-O(2), and C(6)H(12)-O(2) clusters, respectively.

LP-DOAS测量乙二醛时大气中干扰吸收的去除

When measuring glyoxal directly in the atmosphere by Long Path Differential Optical Absorption Spectroscopy(LP-DOAS),the analysis of glyoxal strongly suffers from the cross interference of other absorbers or structure(Xe lamp-structure,H2O,O4 and NO2 absorption).The retrieval method of glyoxal-the elimination of interfering absorption or structure was studied.The Xe lamp-structure will change nonlinearly resulted from the change of pressure broadening and Doppler Broadening with the change of of Xe lamp pressure or temperature.The different lamp reference spectra detected at different time were interpolated to eliminate lamp structure and the resulting residual structures caused by an incorrect elimination were a factor of three below the detection limit of glyoxal;high amount of H2O in the atmosphere cause the nonlinear absorption of H2O and the observed band shape to vary with the column density of H2O.Two H2O absorption spectra with higher and lower column density were interpolated to eliminate nonlinear H2O absorption and the resulting residual structures caused by an incorrect elimination were ten times below the detection limit of glyoxal.In addition,the strong absorption of interfering species NO2 and O4 were also accurately removed.Low detection limit(0.15 ppbv)and low systematic errors(~10 %)were achieved by the accurate elimination of interfering structures.In the end,glyoxal was routinely detected during the daytime on the outskirts of Guangzhou,where mixing ratios ranged from less than detection limit(0.15 ppbv)to 1.66 ppbv.The variation and range of glyoxal concentration detected agreed well with the results reported.

Thermal Decomposition of Xenon Tetroxide at 490–780 K

The decomposition of XeO4 was studied over the temperature range 490–780 K. A reaction mechanism was proposed. A conclusion on the high vibrational excitation of O2 molecules formed in the elementary reaction O + XeO4 → O2 + XeO3 and the branched-chain character of the decomposition with branching in the reaction O + XeO3 → 2O + O2 + Xe was drawn.

Solution multi-NMR and Raman spectroscopic studies of thermodynamically unstable XeO(4). The first (131)Xe NMR study of a chemically bound xenon species.

Xenon tetroxide is thermodynamically unstable, decomposing explosively in the gas phase and in the solid state. A modified and more detailed description of the procedure for the preparation of XeO(4) and its solutions is provided. Xenon tetroxide dissolves in SO(2)ClF, BrF(5), and HF solvents, giving solutions that are kinetically stable up to -30 degrees C. The preparation of kinetically stable XeO(4) solutions lays the groundwork for the solution chemistry of XeO(4) and for the extension of the presently limited chemistry of xenon(VIII). The (129)Xe and (17)O NMR spectra of XeO(4) were observed for the first time, and the tetrahedral symmetry of XeO(4) allowed for the observation of a surprisingly narrow (131)Xe resonance, the first (131)Xe NMR study of a xenon compound. A variable temperature and variable field strength study of the spin-lattice relaxation times for (129)Xe and (131)Xe show that the spin-rotation and the quadrupolar relaxation mechanisms, respectively, are dominant. The Raman spectrum of XeO(4) in anhydrous HF solvent confirms the absence of significant solvent-solute interactions.

Kinetics and mechanism of the reaction of xenon tetroxide with carbon disulfide

The dependence of the rate of the reaction of XeO4with CS2on the concentrations of reactants and diluent gases He, O2, and CO2was studied at room temperature. A reaction mechanism was proposed.

Absorption cross sections and products of photodissociation of xenon tetroxide

The photodissociation of xenon tetroxide under irradiation in the 200–300 nm wavelength region was studied. The absorption cross sections were measured. The main channel of xenon tetroxide photodissociation has been shown to be XeO 4+ hv → 40 + Xe.

Kinetics and mechanism of the photodecomposition of xenon tetroxide

The of photochemical decomposition of XcO4 under the action of UV-radia(ion in the wavelength range of 200–300 nm was investigated. The quantum yield of the formation of oxygen atoms upon XeO4 photodissociation was measured (Ф = 3.6±0.4). The results obtained point to the predominant role of the XeO4 +hv → 4O + Xe photodissociation channel of XeO4. The value of the rate constant of the reaction XeO4 + O → O2 + XeO3 was estimated (<4.5 · 10−16 cm2 s−1).

The Temperature and Concentration Dependences of Diffusion Coefficients of the Systems Ne-O2, Kr-O2, Xe-O2 and He-NO

Diffusion coefficients have been measured for the systems Ne–O2, Kr–O2, Xe–O2 and He–NO at 10 K intervals from 280–320 K. The results differ by as much as 6% from literature values.

Mechanism of formation of XeF* and XeO* excimers by photoexcitation of Xe–F2and Xe–O2mixtures

An investigation was made of excitation transfer from xenon atoms and molecules to F2 and O2 molecules when Xe–F2 and Xe–O2 mixtures were subjected to photoexcitation at wavelengths shorter than 158 nm. This transfer produced XeF* and XeO* excimers. A comparison was made of the kinetics of various models of photoexcitation of Xe–F2 and Xe–O2 mixtures and experimental data. It was established that excitation is transferred from Xe2 molecules formed by photoexcitation to F2 and O2 molecules by a harpoon mechanism.

Contact interaction between 129Xe and nitric oxide

The chemical shift of 129Xe in nitric oxide gas has been observed as a function of temperature and density of NO. The derivative of the frequency with respect to density gives the second virial coefficient of chemical shielding of 129Xe in nitric oxide, σ1(Xe–NO) = −0.6840 + 1.5516 × 10−3τ − 1.3142 × 10−5τ2 +7.2769 × 10−8τ3 ppm amagat−1, in which τ=T−300, and T goes from 220 to 380 K. The results are compared with the Xe in oxygen gas and the contact contribution to σ1(Xe–NO) is determined. By using Ar as the diamagnetic counterpart of an NO or O2 molecule, empirical values of the integral ℱρspine−V/kTdx3 are obtained for the Xe–NO and the Xe–O2 interaction. The empirical values of this integral are greater for the Xe–NO pair than the Xe–O2 pair. Both exhibit a slight temperature dependence.

Vibrational Spectrum and Force Field of Xenon Tetroxide

Infrared and Raman spectra are reported for Xe16O4 and Xe18O4 vapor. The infrared band contours are analyzed to give values for the Coriolis constants and the xenon isotopic frequency shift, and anharmonicity corrections are estimated for the fundamental frequencies. General quadratic force constants are calculated, using as constraints the O16–18O and Xe129–132Xe frequency shifts and the Coriolis constants. The force field is significantly different from those of RuO4 and OsO4. Valence stretching force constants are fr=6.40 ± 0.10 mdyn/Å and frr=−0.08 ± 0.04 mdyn/Å; the negative value of the interaction constant frr indicates that the bonding differs appreciably from that in the transition metal tetroxides. Standard-state thermodynamic functions for XeO4 vapor are calculated for the temperature range 250–400°K.

Das ν1/ν3-Frequenzen-Verhältnis bei tetraedrischen Oxoanionen der Hauptgruppen- elemente und die Schwingungseigenschaften von Xenon-Tetroxid / The ν1/ν3 Frequency Ratio in Tetrahedral Oxoanions of The Main Group Elements and the Vibrational Properties of Xenon-Tetroxid

Abstract In an earlier work we have theoretically derived and explained certain rules relating the ν1/v3 frequency ratio of tetrahedral oxoanions of the transition metals with some basic properties of the anions. It is now demonstrated that these rules are also valid for oxoanions of the main group elements of the periodic system. Applying these and other relations it was possible to predict the value of the symmetric stretching frequency ν1(A1) of xenon tetroxide. Some vibrational properties of XeO4 (force constants, mean amplitudes of vibration, the Coriolis coupling constant and the bond order) are also calculated and compared with those of related species.

Molecular Structure of Xenon Tetroxide, XeO4

The molecular structure of XeO4 has been investigated in the gas phase by electron diffraction. The data are completely compatible with the tetrahedral structure proposed from analysis of the infrared spectrum. Refinement of the structure by least squares based upon intensity functions, treating each distance and amplitude as independent parameters, yielded the results rXe–O = 1.736 Å (0.0023), rO...O = 2.832 Å (0.0086), lXe–O = 0.0468 Å (0.0025), and lO...O = 0.0866 Å (0.0076). Parenthesized values are 2σ and include estimates of systematic error.

Suggested Semiempirical Molecular Orbital Schemes for Xenon Tetroxide

AbstractUsing recently published approximate SCF wave functions for Xenon, the one‐electron molecular orbital energies of xenon tetroxide have been determined in three approximations and within the general formalism of the semi‐empirical Mulliken‐Wolfsberg‐Helmholtz molecular orbital method. The bonding and symmetry‐allowed electronic transitions have been discussed qualitatively.

The Heat of Formation of Xenon Tetroxide1

The Heat of Formation of Xenon Tetroxide¹

Xenon Tetroxide: Preparation and Some Properties

Xenon tetroxide is a yellow solid at low temperature. It has a vapor pressure of about 25 mm-Hg at 0 degrees C. It is unstable at room temperature. The infrared spectrum of the vapor shows it to have tetrahedral symmetry.