Formation Of Xe Research Articles

ChemInform Abstract: Acid‐Base Properties of Xenon Di‐ and Tetrafluoride in High Temperature Reactions.

AbstractReactions of XeF2 and XeF4 with different fluoro complexes of Co, Ni, Cu, Pr, Mn, Ag, and Hg at high temp. result in the formation of Xe(IV) anionic complexes, M2XeF6 (M: K, Cs).

Excited-state dynamics of rare-gas clusters

In this paper we explore the dynamic implications of energy exchange in electronically vibrationally excited states of mixed rare-gas clusters. The classical molecular dynamics method was applied for the study of vibrational energy flow from electronically excited atomic Xe(3P1) states in Xe*Ar12 and Xe*Ar54, and the consequences of Xe*2 (3Σu) excimer formation in Xe*2 Ar11 and Xe*2 Ar53 clusters. We have established the occurrence of an ultrafast vibrational energy flow (∼300 fs) from local Rydberg atomic and excimer excitations into the cluster, which is accompanied by large configurational dilation around the excited state, due to short-range repulsive interactions. Size effects on cluster dynamics were elucidated, being manifested by vibrational predissociation in small clusters and by vibrational relaxation and vibrational energy redistribution in large clusters. A gradual transition from reactive molecular type relaxation in small clusters to nonreactive condensed-matter type relaxation in large clusters was documented. Qualitative and quantitative differences between relaxation of excited species initially located in the interior or on the surface of the cluster were established, being exhibited in the details of the vibrational energy flow. In the case of bulk Xe*2 Ar53, excessive local heating is manifested in cluster melting, which results in mass transport of the excimer to the cluster surface. The many facets of the dynamics of electronically excited mixed rare-gas clusters are amenable to experimental interrogations.

Kinetics of the reactions of xenon trioxide. Communication 4. Mechanism of the decomposition of xenon trioxide in aqueous solution

1. The decomposition of xenon trioxide in aqueous solution proceeds via a chain mechanism over the range 1 < pH < 10 with the formation of hydrogen peroxide and XeO2 (XeO) as intermediate substances. 2. Over the range pH >10 the chain mechanism changes to an ionic mechanism involving the di-sproportionation of Xe(VI) with the formation of Xe(VIII) perxenates.

H++Xe low-energy collisions: Opposite-phase oscillations of the elastic and charge transfer differential cross sections

Elastic as well as charge transfer collisions of H++Xe have been investigated in a crossed beam experiment atECM≈30 and 50 eV. Opposite-phase oscillations have been observed in the elastic differential cross section with respect to the charge transfer differential cross section for the formation of Xe+(2P1/2). Taking advantage of the asymptotic quasi-degeneracy of the channels in question, this behavior has been qualitatively interpreted in terms of a simplified two-curve crossing model. The conditions of the validity of the model are discussed and its relation to the potential symmetry scattering in homonuclear systems is pointed out.

Mass spectrometric and coincidence studies of double photoionization of small molecules

Current and future coincidence techniques in the study of double and multiple ionization by photon impact are reviewed. New results are presented on the formation of Xe+, Xe2+ and Xe3+ in the region of 4d−1 ionization and the triple ionization mechanism is discussed. The thresholds for Xe2+ and Xe3+ are determined as 33.05±0.3 and 64.1±0.3 eV respectively. Triple ionization of a molecule (OCS) followed by fragmentation into three cations is demonstrated for the first time. The formation and charge separation reactions of several molecular double cations are examined by coincidence techniques: intramolecular isotope effects, rearrangement reactions and slow dissociations are shown to occur in triatomic and other small doubly charged molecular ions.

Reaction of xenon difluoride with organomercury compounds

The Si-C bond is known not to split under the action of XeF/sub 2/. It is shown here that the compounds R/sub 2/Hg (R = PhC=C, p-MeO-C/sub 6/H/sub 4/, pMe/sub 2/N-C/sub 6/H/sub 4/, pEtO/sub 2/C-C/sub 6/H/sub 4/, PhCH/sub 2/) react with XeF/sub 2/ with splitting of the C-Hg bond. This results in the formation of Xe, RHgF (or a mixture of RHgF + HgF/sub 2/, where R = PhCH/sub 2/ is rapidly demercurated), RF (except for R = PhC=C), and R/sub 2/, as well as products of the reaction of the radicals R/sup -/ with the solvents, for which purpose dry CCl/sub 4/ or CHCl/sub 3/ was taken. The reaction was carried out in an argon atmosphere, since oxygen-containing compounds are otherwise obtained. The composition of the products was determined by gas-chromatographic-mass spectrometry.

Formation of Xe ∗2 by collision pair absorption at 158 nm

Pair absorption from colliding Xe atoms of the molecular fluorine laser radiation is reported. The absorption coefficient for this process at 300 K was found to be α = (4.32 ± 0.1) × 10 -9 Torr -2 cm -1. Fluorescence at 172 nm originating predominantly from the 1Σ + u state of Xe ∗ 2 indicates that by this mechanism the Xe dimer laser can be pumped optically.

Kinetics of the formation of Xe(6p[1/2]) and Xe(6p[3/2]2) by vacuum-ultraviolet irradiation

The (6p[1/2]0) and (6p[3/2]2) states of Xe have been produced by vacuum-ultraviolet irradiation and selectively detected by their emissions at 828.01 and at 823.16 nm due to the transitions (6p[1/2]0→6s[3/2]1) and (6p[3/2]2→6s[3/2]2), respectively. Both states are not radiatively coupled to the ground (1S0) level according to the electric dipole selection rules. A study of the intensity of the emission lines and of the relative quantum yields as a function of pressure allows a kinetic mechanism to be outlined consistent with the present data. Experiments have been carried out at nine selected wavelengths corresponding to peculiar regions in the Xe vacuum-ultraviolet absorption spectrum and the main result is the observation of a marked difference in the behavior of the system as far as the formation of the two relevant Xe states is concerned. The (6p[1/2]0) level shows a pressure dependence which is very often higher than the (6p[3/2]2) level and very close to the pressure dependence of the absorption of the incident radiation.

Transient absorption in electron-beam-excited rare gases at XeF laser wavelengths

Transient absorption experiments in pure and mixed rare gases were performed at the XeF laser wavelength using a broadband probe technique. The major absorbing species in this region are identified. There is a strong broadband absorption in electron-beam-excited argon which is due to Ar+2. In neon plasmas the broadband absorption is much weaker. However, there are a number of strong line absorptions due to Ne(3s-4p) transitions, one of which coincides with the 351-nm emission band of the XeF laser. Addition of xenon reduces Ne* absorption. The amount of xenon used is limited by the formation of Xe+2, which is also a strong absorber in the 350-nm region.

A kinetics scheme for the XeF laser

A kinetics scheme is described for electron-beam excitation of the XeF laser in a neon diluent. Both Ne+ and Ne* channels contribute significantly to the formation of the upper laser level. In each chain an important Penning ionization process leads to the formation of Xe+, which is the major intermediary in forming the upper laser level. Xe+2 is found to be the dominant absorber of laser radiation. The effect of the weakly bound XeF ground state is discussed.

Photoemission Studies on Rare Gas Matrices

AbstractPhotoelectron energy distribution measurements with synchrotron radiation are very useful for the determination of energy levels and the band structure of pure and doped solid rare gas matrices and for the investigation of energy transfer processes. The band formation in Xe–Ar alloys with varying concentration and energy transfer processes in Xe doped Ar and Ne matrices are described and discussed.

Argon sensitized formation of Xe +2: A new mechanism for the Jesse effect

Photoexcitation of the argon resonance states in the presence of xenon leads to Xe + 2. Kinetic analysis indicates rapid near-resonant energy transfer between argon and xenon atoms. The possibility of an analogous mechanism in other rare gas systems is examined.

Electronic energy transfer in rare gas mixtures

In this paper we present the results of an experimental study of electronic energy transfer in xenon-argon and xenon-krypton gaseous mixtures excited by an α source. Spectroscopic evidence is presented for molecule-atom energy transfer from Ar*2(1,3Σu) to Xe(1P1) and from Kr*2(1,3Σu) to Xe(3P1). These two electronic energy transfer processes are characterized by large ∼ 10−14 − 10−13 cm2 cross sections. Information has been obtained for collision-induced energy conversion processes of the Xe energy acceptor involving 1P1 → 3P1 conversion and the formation of Xe*2(1,3Σu) at moderately low (≤ 200 ppm) Xe concentrations. A new emission band, observed in the xenon-krypton system, peaking at 1530Å, is tentatively assigned to a heteronuclear (KrXe)* diatomic molecule.

I [sbnd]Xe dating: Evidence for cold assembly of an unequilibrated chondrite

Essentially all of the more equilibrated meteorites which contain excess radiogenic 129Xe have well-defined I Xe formation intervals that apparently date the onset of proportional retention for iodine and radiogenic 129Xe from the decay of 129I. Precise data on the unequilibrated chondrite Manych, which contains large excesses of 129Xe, clearly demonstrates a lack of correlation between the radiogenic 129Xe and iodine. Although this effect might be accounted for by other mechanisms, it can also be interpreted as evidence for the cold accretion of constituent parts, some of which may have retained the I Xe record of a previous history. Re-examination of data from the unequilibrated chondrites Chainpur and Renazzo tend to support such an interpretation.

Photo-attenuation cross sections of Xe and Xe 2 between 1050 and 1550 Å

Total attenuation of radiation in the spectral region 1050-1550 Å has been measured for xenon gas. The attenuation does not follow Beer's law. The observed linear increase in attenuation cross section with rise in gas pressure, and the related decrease in attenuation cross section with increase in temperature, are ascribed to the formation of Xe 2 molecules. Using methods presented recently, (1) the attenuation cross sections of Xe and Xe 2 are derived from total attenuation measurements. The value of the heat of dissociation for Xe 2, 0·03±0·001 eV, has been confirmed.

Operation of Cofactors in Two-Stage Photophosphorylation

Chloroplasts illuminated at pH 6 accumulate a limited amount of “XE” — an unidentified component which can phosphorylate ADP in a dark reaction at pH 8. The maximum formation of XE requires 15 to 30 seconds’ light if a cyclic cofactor is present, and otherwise as much as 4 minutes’ light. Ferricyanide and cyclic cofactors provide the highest XE yields, with other cofactors giving a lower value. The cofactorless system appears to have two components of which one is ascorbate dependent. The results suggest that XE is located at or near the phosphorylation site as studied in one stage photophosphorylation at pH 8.