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.     

Photoemission studies of Ar,Kr and Xe adsorbed on Al(111): Dipole moments,polarizabilities and spatial distributions

Submonolayers of rare gases adsorbed on Al(111) have been studied using photoemission techniques. Coverage-dependent core level binding energy shifts and work function changes have been measured; polarizabilities and dipole moments are deduced. Results indicate that adatom spatial distributions for Xe submonolayers adsorbed on Al(111) at 40 K are best described by a random 2-dimensional distribution, and there is negligible charge transfer from the Al substrate onto the Xe adatoms in the photoionization process.     

Kr/Xe气体在塑料闪烁体表面的吸附与扩散行为研究

采用基于Compass力场的分子动力学(MD)方法,研究了惰性气体氙(Xe)和氪(Kr)在塑料闪烁体(聚乙烯基对甲苯)的平整和粗糙表面的吸附和扩散行为.由惰性气体吸附曲线的均方根位移(MSD),得到了Xe/Kr气体在聚乙烯基对甲苯表面的扩散系数.研究结果表明,Kr/Xe气体均被稳定地吸附在塑料闪烁体表面,其稳定性随着温度的升高而增加,Xe分子的吸附性强于Kr分子. Kr/Xe气体在聚乙烯基对甲苯表面具有较强的扩散性能,扩散深度随着温度与厚度的增加而增加,最大为22.865?,Kr分子扩散能力强于Xe分子.基底粗糙表面增加了两种惰性气体分子的吸附和扩散.     

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 [11̄0] 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.     

Efficient fluorescence in solid noble gases excited by 10—30 kV electrons

Fluorescent spectra and efficiency of vacuum ultraviolet generation have been investigated for solid Ar, Kr and Xe excited by 10–30 kV electrons. Overall conversion efficiency of e-beam energy into a single 7 nm wide band centered near 175 nm for Xe was measured to be 30%, indicating high intrinsic efficiency when electron backscatter is taken into account. In Ar and Kr the presence of trace amounts of O₂was found to cause energy transfer from the excimer bands to longer wavelengths.     

产生惰性气体高价离子的新方法

此文介绍了一种产生惰性气体高价离子的新方法。在飞行时间质谱仪（ＴＯＦ－ＭＳ）上，把聚焦后的３０８ｎｍ激光掠射到不锈钢栅网上，产生超短脉冲的电子束，利用这种电子束来轰击惰性气体（Ｈｅ，Ｎｅ，Ａｒ，Ｋｒ，Ｘｅ），产生高价离子，并给出了这些离子的飞行时间质谱。这些高价离子可能是电子逐次电离气体原子产生的。这种方法可作为飞行时间质谱的一种理想的“软电离”的“点”离子源     

The influence of dipoles in intermediate layers on the electronic levels of physisorbed species studied by UPS

Angle-resolved UV photoelectron spectra were measured at 20 K on Xe/ N₂/X/Ni (110) multilayers in which X were chemisorbed H₂O, N₂ and CO molecules. The chemisorbed molecules change the work function by different amounts. The binding energy of Xe referred to the Fermi edge of the substrate is shifted according to these work-function changes, but it stays constant with respect to the vacuum level. This experiment proves that there is no measurable interaction between the photon created hole and the dipole of the chemisorbed molecule, in the final state of the photoemission process.     

Ar and Kr adsorption on Ag(111)

Precise structural and thermodynamic studies of Kr and of Ar adsorbed on Ag(111) are made using low energy electron diffraction. The phase diagram, lattice constants of the unconstrained monolayer and of the monolayer in equilibrium with the bilayer, latent heats of adsorption and isosteric heats are measured. The results are similar to those of an earlier study of Xe adsorbed on Ag(111). The results are compared to model calculations using effective lateral interactions which are similar to those for Xe/Ag(111). Comparison of the results for Xe, Kr, and Ar on Ag(111) is made using corresponding states scalings. A comparison is also made with properties of the non-registry phases of Xe, Kr, and Ar on basal plane graphite.     

Sputtering gases and pressure effects on the microstructure,magnetic properties and recording performance of TbFeCo films

The MsHc value is considered to be a key factor in high-density recording, and controlling the microstructure on the magnetic underlayer was found to be an effective way of increasing the MsHc of the amorphous TbFeCo magneto-optical (MO) medium. In this paper, we investigate the TbFeCo film's magnetic properties and the effects on the microcolumnar structure, which depends on the sputtering conditions of using various sputtering gases including Ar, Kr, and Xe, and the recording characteristics of TbFeCo memory layers. With heavy sputtering gases such as Kr or Xe, the columnar structure can be prepared in a TbFeCo film at a pressure lower than 1.0 Pa. The columnar structure of a recording layer can be effectively formed thanks to the effects of the magnetic underlayer, which has a fine surface even in the sputtering process in which Xe gas is used. The above applies to the sputtering process in which Ar gas is used. Also, when Xe gas is used in the sputtering process, coercivity Hc is increased through the formation of a well-segregated microcolumnar structure built on domain wall pinning sites, and we obtain a large MsHc and a high squareness ratio of the Kerr-hysteresis loop. Our results indicate that processing a TbFeCo film with heavy sputtering gases is suitable for tiny mark stability because the temperature gradient of Hc is increased. The objective of the low-pressure sputtering process using Xe gas to produce the columnar structure is to achieve ultra-high-density recording with tiny mark stability in the TbFeCo medium. This has been confirmed with magnetic force microscope (MFM) images of stable tiny marks recorded on TbFeCo film.     

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.     

Editorial

A high resolution electron spectroscopy technique is used to study the autoionization of noble gases excited by fast neutral noble gas atoms with 80–600 eV kinetic energy. The energy and notation of the excited states is determined by considering the proper quantum defects in the Rydberg series. The doubly excited states prevail over the singly excited ones. Like and unlike colliding pairs are studied and various excitation processes are suggested for the HeKr, ArKr and ArXe systems.     

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.     

The influence of hyperpolarisability and field-gradient polarisability on field adsorption binding energies for He on W(111)

The effects of imaging-gas hyperpolarisability and field-gradient polarisabuity terms on field-adsorption binding energies have been explored. At best image fields for the noble imaging gases and molecular hydrogen, the correction to long-range binding energy is at most a few percent and may be neglected. At the tungsten evaporation field the correction is significant in the cases of Ar, Kr, H₂, and especially Xe. The system He on W(111) has been used as a paradigm in the investigation of short-range binding energy. The largest correction here is due to one of the field-gradient polarisabuity terms. In the field range of most relevance to the field-ion techniques the total correction is about 15–20%, and should not be neglected in detailed treatments.     

Surface and interface effects in the optical properties of silver nanoparticles

We present novel experimental results about influences of surrounding foreign materials on optical properties of small silver clusters. First we show spectra of free cluster beams produced with different seeding gases Ar, Kr, Xe. Second, we estimate, from measured spectra, the cluster deformations and contact areas after deposition on different substrates (Cr₂O₃ and MgF₂) at room temperature and on SiO₂ at 110 K and between 160 K and 300 K. Third, we present and compare the static and dynamic charge transfer after embedding the clusters in various fluorides and compare with previous results on oxides. Received 2 September 1998 and Received in final form 3 January 1999     

Temperature effects on appearance potentials of gas phase field ions

Field ion appearance potential spectroscopy (FIAPS) measurements for the rare gases Ar, Kr, and Xe and for Ag vapour in front of a tungsten surface are performed by retarding grid energy analysis before a quadrupole mass analyzer. The temperature ranges are for Ar, Kr, and Xe 80 K ?T;? 700 K, for Ag;T;≈ 1300 K. The temperature alters the appearance potential up to 0.5 eV, depending on the experimental signal to noise ratio. For a typical signal-to-noise ratio of 10⁴, shifts are approximately 10kT. This can be ascribed to the high energy tails of the approximated Maxwell distribution of elastically reflected and of accommodated gas particles and of the Fermi distribution of unoccupied electronic states of the solid. At any of the temperatures of investigation, the appearance potential is found to be independent of the field strength values, at $\text{1 × 10}{}^{10}\text{V}\text{m}\text{<F;< 2.2 × 10}{}^{10}\text{V}\text{m}$     

Pressure broadening and shifting parameters for the spectral lines in the fundamental vibration-rotation bands of HBr and HI in mixtures with rare gases

We report measurements of the line broadening and shifting coefficients in the (1 ← 0) fundamental absorption bands of the HBr and HI molecules in mixtures with rare gases He, Ne, Ar, Kr, and Xe. Comparison is given with the published data on other HHal-Rg systems. The measured line shifts are separated into terms symmetric and asymmetric in the line number m. The magnitudes of the symmetric shifts change in a regular manner in the series of rare gases and reach perturber-specific asymptotic values at higher ∣m∣. It is found that the asymptotic values of the symmetric line shifts linearly correlate with the respective C₆ potential energy constants and that the slopes of these correlations are proportional to the vibrational ground state dipole moments squared of the hydrogen halide molecules.     

Interaction of H2O with a clean and oxygen precovered Ni(110) surface studied by XPS

The adsorption and reaction of H₂O on clean and oxygen precovered Ni(110) surfaces was studied by XPS from 100 to 520 K. At low temperature (T<150 K), a multilayer adsorption of H₂O on the clean surface with nearly constant sticking coefficient was observed. The O 1s binding energy shifted with coverage from 533.5 to 534.4 eV. H₂O adsorption on an oxygen precovered Ni(110) surface in the temperature range from 150 to 300 K leads to an O 1s double peak with maxima at 531.0 and 532.6 eV for T=150 K (530.8 and 532.8 eV at 300 K), proposed to be due to hydrogen bonded O_ads… HOH species on the surface. For T>350 K, only one sharp peak at 530.0 eV binding energy was detected, due to a dissociation of H₂O into O_ads and H₂. The s-shaped O 1s intensity-exposure curves are discussed on the basis of an autocatalytic process with a temperature dependent precursor state.     

Site induced structures in the lowest electronic transitions of naphthalene-H8 and -D8 in rare-gas matrices

Phosphorescence spectra and S₁ ← S₀ excitation spectra of naphthalene-h₈ and -d₈ in Ar, Kr and Xe matrices have been investigated with medium spectral resolution. Observed site structures in the spectra are depemdent on deposition conditions and annealing. Comparison of calculated and experimentally observed site shifts suggests that the matrix structure is preferentially ccp. Possible assignments of the site structures are given. Geometrical changes of naphthalene in excited states are important factors determining site structure in electronic transitions.     

Current characteristics of barrier discharges in inert gases (Ar,Kr, Xe)

The current characteristics of barrier discharges in inert gases (Xe, Kr, and Ar) are compared. It is shown that the shape of the current curve (the number of peaks and their amplitudes) depends on the kind of gas (breakdown voltage) and the frequency of the sinusoidal supply voltage; as the frequency of the voltage decreases, the number of breakdowns tends to increase. It is found that, under the experimental conditions (P = 300 Torr, d = 4 mm), the amplitude of the discharge current in Xe is two to three times higher, its time is tenfold shorter, and the diameter of the discharge channel is five to ten times smaller compared to other inert gases. These differences can be explained by a considerable difference of the transfer coefficients in Xe from those in Ar and Kr.