He/Ar/Kr/F2混合气体中准分子KrF*和Kr2F*的动力学研究

本文用时间积分谱的方法研究了快放电激励下He/Ar/Kr/F₂混合气体中Kr₂F^*的动力学,探讨了Kr₂F^*形成的通道特性,理论分析和实验结果表明,在快放电激励下,三体碰撞过程KrF^*+Kr+M→Kr₂F^*+M是形成Kr₂F^*的主要通道,而置换反应ArF^*+Kr→KrF^*+Ar又能有效地产生KrF^*。实验测量了Kr₂F^*形成的有关速率常数。 关键词：     

Multiphoton mass spectra of XeKr molecules in the range of excited Xe*6<Emphasis Type="Italic">p</Emphasis>[5/2]<Subscript>2, 3</Subscript> atoms

Data on excited states of XeKr molecules in the energy range 78280–77600 cm^?1 are obtained. Using the method of multiphoton laser photoionization of molecules in a supersonic jet, five vibrational progressions of XeKr molecules are obtained, which are attributed to five electronic-vibrational transitions from the ground state of the XeKr molecule of the symmetry 0⁺ to excited states of the symmetry Ω = 0⁺, 1, 2 with the dissociation limit Kr¹ S ₀ + Xe*6p[5/2]₂ and of the symmetry Ω = 1, 2 with the dissociation limit Kr + Xe*6 p [5/2]₃. The molecular constants of the corresponding excited states of the XeKr molecule are estimated.     

The scattering of He from adsorbed layers of gases on Ag(110)

The adsorption of gases on Ag(110) has been studied using inelastic He atom scattering. Vibrational spectra have been obtained for Kr, Xe, C₂H₆, C₂H₄, CH₄, CF₄, CHF₃, CO₂ and H₂O. Spectra have also been obtained for multilayers of Xe (2 layers) and C₂H₆ (3 and 4 layers) where the energy changes move to lower values. The scattering from Kr and Xe can be shown to be dispersionless as has been previously found for these adsorbates on Cu(100) and Cu(110). The energy changes for Kr and Xe are smaller than on Cu surfaces and attempts were made to account for this based on an Einstein model of the adsorbed atoms in the surface holding potential.     

Electronic and geometric structure of doped rare-gas clusters: surface, site and size effects studied with luminescence spectroscopy

The electronic and geometric structure of rare gas clusters doped with rare-gas atoms Rg = Xe, Kr or Ar is investigated with fluorescence excitation spectroscopy in the VUV spectral range. Several absorption bands are observed in the region of the first electronic excitations of the impurity atoms, which are related to the lowest spin-orbit split atomic ³P₁ and ¹P₁ states. Due to influence of surrounding atoms of the cluster, the atomic lines are shifted to the blue and broadened (“electronical cage effect”). From the known interaction potentials and the measured spectral shifts the coordination of the impurity atom in Ar_N, Kr_N, Ne_N and He_N could be studied in great detail. In the interior of Kr_N and Ar_N the Xe atoms are located in substitutional sites with 12 nearest neighbours and internuclear distances comparable to that of the host matrix. In Ne_N and He_N the cluster atoms (18 and 22, respectively) arrange themselves around the Xe impurity with a bondlength comparable to that of the heteronuclear dimer. The results confirm that He clusters are liquid while Ne clusters are solid for N≥ 300. Smaller Ne clusters exhibit a liquid like behaviour. When doping is strong, small Rg_m-clusters (Rg = Xe, Kr, Ar, m≤10 ²) are formed in the interior sites of the host cluster made of Ne or He. Specific electronically excited states, assigned to interface excitons are observed. Their absorption bands appear and shift towards lower energy when the cluster size m increases, according to the Frenkel exciton model. The characteristic bulk excitons appear in the spectra, only when the cluster radius exceeds the penetration depth of the interface exciton, which can be considerably larger than that in free Rg_m clusters. This effect is sensitive to electron affinities of the guest and the host cluster.     

VUV spectra from the krypton-fluoride ionic excimer

New continuous VUV radiation near 148 nm was observed from Kr/NF₃/He and Kr/F₂/He mixtures under X-ray excitation from a laser-produced plasma. Theoretical and experimental analysis shows that the continuum can be attributed to the transition of the ionic excimer Kr²⁺F^–.     

Production of Kr2+ in collisions of rare gas ions with Kr

Total and differential cross sections for the production of fast Kr²⁺ ions in collisions of He⁺, Ne⁺ and Ar⁺ with Kr were measured at primary energies below 500 eV. In the system Ar⁺+Kr most of these reactions occur in close collisions and are accompanied by a large momentum transfer. For Ne⁺+ Kr collisions the angular distribution in the centre of mass system is approximately isotropic over a wide angular range. The cross section values for the Kr²⁺ production amount to 1% of the total charge transfer cross section in the investigated energy range.     

Infrared spectra of the Kr—CO and Xe—CO van der Waals complexes

The infrared spectra of the weakly bound complexes Kr—CO and Xe—CO have been studied in the region of the CO stretching vibration (4.7 μm) using a high-resolution tuneable diode laser probe. The complexes were observed in a long path (200 m) low temperature (76 K) gas cell (Kr—CO) and in a pulsed supersonic jet expansion (Kr—CO and Xe—CO). Previous long path cell measurements on these complexes at lower resolution analysed only the K = 0 and 1 stacks of rotational levels in the ground intermolecular vibrational state. The new data extend up to K = 3 (Xe—CO) or 4 (Kr—CO), and also include K = 0 and 1 stacks in the excited bending state, ν₂ = 1. The bending frequencies for Kr—CO and Xe—CO (in the ν_co = 1 upper state) were determined to be 13.156cm_?1 and 13.794cm^?1, respectively. Detailed molecular parameters were determined to describe the rotational energy levels of each complex using a simple empirical Hamiltonian. These results enable parameters to be compared for the entire series of rare gas—carbon monoxide complexes, from He—CO to Xe—CO. Also they will guide the future development and evaluation of accurate intermolecular potential energy surfaces for Kr—CO and Xe—CO.     

Experimental determination of the potential energy curves of the I(3/2u) and I(3/2g) states of Kr+ 2

The I(3/2u) and I(3/2g) states of Kr⁺ ₂ have been investigated by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy following (2 + 1′) resonance-enhanced multiphoton excitation via the 0⁺ _g Rydberg state located below the Kr?([4p]⁵5p[1/2]₀) + Kr(¹S₀) dissociation limit of Kr₂. From the positions of a large number of vibrational bands in the spectra of the ⁸⁴Kr₂ and ⁸⁴Kr-⁸⁶Kr isotopomers, the adiabatic ionization potentials (IP(I(3/2u)) = 112672.4 ± 0.8cm^?1, IP(I(3/2g)) = 111 395.0 ± 1.4cm^?1), the dissociation energies (D ⁺ ₀(I(3/2u)) = 368.8 ± 2.0cm^?1, D ⁺ ₀(I(3/2g)) = 1646.2 ± 2.3cm^?1) and vibrational constants for both ionic states have been determined. Potential energy curves have been extracted which perfectly reproduce all experimental observations and are accurate over a wide range of energies and internuclear distances. The equilibrium internuclear distances (R ⁺ _e(I(3/2u)) = 4.11 ± 0.04 Å, R ⁺ _e(I(3/2g)) = 3.35 ± 0.10 Å) have been derived by comparing the intensity distribution in the PFI-ZEKE photoelectron spectra to calculated Franck-Condon factors. The dissociation energy of the I(3/2g) state and the equilibrium internuclear distance of the I(3/2u) state differ markedly from previously reported values.     

Characterization of collisionally pumped optical-field-ionization soft X-ray lasers

We give an overview of recent experimental results on optical-field-ionization collisional soft X-ray lasers developed at LOA. By focusing a 30-fs, circularly polarized Ti-sapphire laser pulse at an intensity of up to 8×10¹⁷ Wcm^-2 into a low-density gas cell containing Xe or Kr, we produced a few mm long plasma column for soft X-ray amplifier. Saturated amplification has been achieved on the 4d⁹5d(¹S₀)–4d⁹5p(¹P₁) transition at 41.8 nm in Xe⁸⁺, and on the 3d⁹4d(¹S₀)–3d⁹4p(¹P₁) transition in Kr⁸⁺ at 32.8 nm. Under optimum pumping conditions the Xe⁸⁺ laser provides about (5±2)×10⁹ photons per pulse whilst the Kr⁸⁺ laser delivers up to (2.5±1)×10⁹ photons per shot. The repetition rate of these soft X-ray lasers is 10 Hz. The beam wavefront of the Xe⁸⁺ laser has been measured by a Shack–Hartmann soft X-ray wavefront sensor, and the pulse duration by a cross-correlation technique. PACS 42.55.Vc; 32.30.Rj; 52.50.Jm     

Inelastic atom scattering from layers of atoms and molecules on Cu(110)

The vibrational properties of adsorbed layers have been studied using inelastic He atom scattering. The substrate was Cu(110) viewed along the [001] and [11&#x0304;0] azimuth. The adsorbates included, Kr, Xe, CH₄, CD₄, C₂H₆, CO, CO₂ and O₂ and covered the region of both physisorption and chemisorption. Despite a range of binding energies and mass ratios the vibrational frequencies showed no dependence on the momentum change, i.e. scattering was dispersionless, although intensity changes occurred in the inelastic peaks. There seemed to be no dependence of the adsorbate spectra on coverage below a monolayer. The peaks of CH₄ and C₂H₆ appeared broader than those of Kr and Xe suggesting molecular motions. Further, CH₄ and C₂H₆ gave very similar spectra. Both energy gain and loss events were observed in the inelastic spectrum. For those adsorbates which gave multilayer adsorption (Xe, C₂H₆) changes in the spectra were observed as the second layer developed. In the latter category also, mixed layers (Xe on C₂H₆, Xe on CO and C₂H₆ on Xe) were studied.     

An experimental investigation of the pressure and concentration dependence of muonic Coulomb capture and cascade in gases

Muonic Coulomb capture ratios and x-ray intensity patterns in four binary mixtures of the gases N₂, Ne, Ar, Kr, and Xe have been measured at three atomic ratios. An influence of the concentration has been established. The Lyman series intensity patterns of pure N₂, Ne, Ar, Kr, and Xe were measured at pressures between 0.4 and 51 bar and found to depend on the pressure. Possible explanations are discussed.     

Excess Gibbs energy for six binary solid solutions of molecularly simple substances

In this paper we apply the method developed in a previous study of Ar + CH₄ to the evaluation of the excess Gibbs energy G^{E S} for solid solutions of two molecularly simple components The method depends on combining information on the excess Gibbs energy G^{E L} for the liquid mixture of the two components with a knowledge of the (T, x) solid-liquid phase diagram Certain thermal properties of the pure substances are also needed G^{E S} has been calculated for binary mixtures of Ar + Kr, Kr + CH₄, CO + N₂, Kr + Xe, Ar + N₂ and Ar + CO. In general, but not always, the solid mixtures are more non-ideal than the liquid mixtures of the same composition at the same temperature Except for the Kr + CH₄ system, the ratio $\text{r =}\text{G}{}^{\mathrm{E\; S}}\text{G}{}^{\mathrm{E\; L}}$ is larger the richer the solution in the component with the smaller molecules     

Heavy ion irradiation-induced phase transformation in polycrystalline Dy2O3

Radiation damage effects in polycrystalline pellets of the rare earth sesquioxide Dy₂O₃ irradiated with 300?keV Kr²⁺ ions were studied by combining grazing incidence X-ray diffraction (GIXRD) with transmission electron microscopy (TEM). Radiation damage was introduced using 300?keV Kr²⁺ ions to fluences up to 1?×?10²⁰?Kr?m^?2 at cryogenic temperature. GIXRD and cross-sectional TEM observations revealed that the crystal structure of the irradiated Dy₂O₃ transformed from a cubic, so-called C-type rare earth sesquioxide structure to a monoclinic, B-type rare earth sesquioxide structure upon ion irradiation. In addition, TEM and high-resolution electron microscopy (HREM) indicated that the transformed surface Dy₂O₃ layer adopts an epitaxial orientation relationship with the substrate Dy₂O₃.     

Nonresonant third order hyperpolarizability of rare gases and N2 determined by third harmonic generation

The third order hyperpolarizabikity γ⁽³⁾₁₁₁₁(-ω₃;ω₁,ω₁,ω₁) of the rare gases He, Ne, Ar, Kr, Xe and of N₂ are determined by third harmonic generation involving picosecond light pulses of a Nd-glass laser. The results are compared with reported experimental and theoretical values.     

Energy distribution of photoelectrons generated from highly charged ions in a circularly polarized intense laser field

We observed the energy distribution of the photoelectrons generated from the highly charged ions in the tunneling regime by using a circularly polarized Ti:Sapphire laser (745 nm, 100 fs). The peaks for each successive charge state up to Ar³⁺, Kr⁴⁺, and Xe⁵⁺ were clearly resolved, and the peaks due to higher charge states were flattened in the high-energy region and deviated from those predicted by the quasistatic model. This deviation is explained by pondero-motive acceleration in the strong field gradient. In Xe, Xe⁸⁺ was generated at a peak intensity of 2.0 × 10¹⁶ W/cm².     

Charge-transfer reactions in clusters excited with synchrotron radiation

Charge-transfer reactions are observed in a photoluminescence study of NF₃\rm NF_3-doped free krypton clusters. They show up in emissions from Kr⁺F^-\rm Kr^{+}F^{-}free excimers ejected from the clusters, and from excited Kr₂⁺F^-\rm Kr_2^{+}F^{-}and Kr₂⁺(NF₃)_m^-{\rm Kr}_2^{+}({\rm NF}_3)_m^{-} (m 3(m\geq 1) solvated in the clusters. The results show that reaction dynamics in clusters differs considerably from that in the gas and solid phases.     

Infrared diode laser spectroscopy of the Kr–N2O van der Waals complex: the v 1 symmetric stretch region of N2O

The rovibrational spectra of four isotopomers of the Kr–N₂O van der Waals complex, namely ⁸²Kr–N₂O, ⁸³Kr–N₂O, ⁸⁴Kr–N₂O and ⁸⁶Kr–N₂O, were measured in the v ₁ vibrational band region of the N₂O monomer (～1285?cm^?1) using a tunable diode laser spectrometer to probe a pulsed supersonic slit jet. Rotational constants for both ground and excited vibrational states of these four isotopomers were accurately determined. The band-origin of Kr–N₂O was observed to shift by +0.1065?cm^?1 from that of the monomer. The band-origin shifts of Rg–N₂O (Rg?=?Ne, Ar, Kr) in the v ₁ vibrational band region could also be well explained by the model based on a Buckingham intermolecular potential [W.A. Herrebout, H.-B. Qian, H. Yamaguchi and B.J. Howard, J. Mol. Spectrosc. 189, 235 (1998)]. But the band-origin shift of He–N₂O was found to deviate significantly from this model. The possible reason is discussed and the band-origin shift of Xe–N₂O predicted.     

Ion beam induced modifications of TiN and Ti films on Al-3% Mg substrates

Thin titanium nitride films (50–110 nm) deposited via magnetron sputtering on Al+3 wt.% Mg substrates were irradiated with Ar, Kr, and Xe ion beams at room temperature and with energies between 0.1–0.9 MeV. Sputtering yields and interface mixing rates were determined using Rutherford backscattering (RBS) as depth profiling method. The obtained TiN sputtering yields for Ar and Xe irradiation are found to be in good agreement with predictions of the Sigmund approach. A systematic study with Ar and Xe beams revealed a correlation of the mixing rate with the parameter d/R _p, where d denotes the layer thickness and R _p the mean projected ion range. The mixing data and Monte-Carlo calculations of the collision cascades elucidate the importance of focused recoil transport, especially in the case of Xe irradiations. The results from ion mixing experiments of titanium films (70–140 nm) on Al-3% Mg with 0.1–1.0 MeV Xe beams and 0.05–0.2 MeV Ar beams support these conclusions.     

On the spin-orbit splitting of the rare gas-monohalide molecular ground state

The spin orbit splitting of the molecular ground state of two atomsA(² P _{1/2, 3/2}) andB(¹ S ₀) is discussed. If the spin orbit matrix elements do not depend on the internuclear distance, it is sufficient to know any two of the three potentials of the ground state manifold. The third can then be calculated analytically. Data are presented for theA II 1/2 state of F+Ne; (F, Br)+(Ar, Kr, Xe); and Cl+Xe, as well as for theA I 3/2 state of HeNe⁺.     

UV photoemission from physisorbed atoms and molecules: Electronic binding energies of valence levels in mono- and multilayers

Angle-resolved UV photoemission spectra were measured for Ar, Kr, Xe, CO, O₂ and N₂ adsorbed on a Ni(110) surface at 20 K. The different gases were adsorbed also on the Ni(110) surface which had been precovered by mono- and multilayers of the same gases. Upon physisorbing one of these species onto the bare and precovered Ni surface, binding energy shifts up to 3 eV were found. These shifts will be explained by work function changes of the substrate onto which the gas is physisorbed. It will be shown that for the investigated gases the binding energy referred to the vacuum level is an atomic or molecular property which is independent of the substrate, to a first approximation. By physisorption of a known gas the work function of any substrate can be evaluated by UPS. The density of valence states for bulk Ar, Kr and Xe will be discussed. There is evidence that the conduction band can be seen in the secondary electron background of the UP spectra.