[en] Present report is the proceedings of the 4th Meeting on Tunneling Reaction and Low Temperature Chemistry held in August 3 and 4, 1998. The main subject of the meeting is 'Tunneling Reaction and Its Theory'. In the present meeting the theoretical aspects of tunneling phenomena in the chemical reaction were discussed intensively as the main topics. Ten reports were presented on the quantum diffusion of muon and proton in the metal and H₂^- anion in the solid para-hydrogen, the theory of tunnel effect in the nuclear reaction and the tunneling reaction in the organic compounds. One special lecture was presented by Prof. J. Kondo on 'Proton Tunneling in Solids'. The 11 of the presented papers are indexed individually. (J.P.N.)

[en] Full text: The field of Ion Beam Analysis has steadily developed over the past forty yields to provide more detailed information for the analyst from a wider range of materials analysis tools. The first technique to be well developed was Rutherford Backscattering Spectrometry (RBS) which relied on the elastic and inelastic scattering of H and He projectiles to provide composition and structural information in the near surface region. From this grew Ion Channeling which provided a valuable structural tool for the crystallographic location of impurities in solids. The field expanded to include Proton Induced X-ray Emission (PIXE) and Nuclear Reaction Analysis (NRA) which pushed the detection limits beyond the range of RBS for most elements. Apart from different techniques the energy range was extended to develop Medium Energy Ion Scattering (MEIS, 100-500 keV) which has been shown to probe the first 3-10 atomic layers with almost layer by layer resolution and Low Energy Ion Scattering (LEIS) which is exceedingly sensitive to the outermost one or two atomic layers. By pushing the limits of techniques we can push the detection limits. This will be shown for MEIS and for recoils. The use of recoils over a wide range of energies will be discussed to show the range of applications and the versatility of the techniques. At the low energy end this technique has the flexibility to not only detect 10^-4 of a mono-layer of O on a clean surface and locate it crystallographically at the low energy end, while at the high energy end it also allows multi-element depth profile analysis with a uniform detection sensitivity over half the periodic table. The power and capacity of these scattering and recoil methods as well as future developments will provide an insight to the future expansion of techniques and applications

[en] Semiconductor nanocrystals have been the focus of much attention in the last ten years due predominantly to their size dependent optical properties. Namely, the band gap of nanocrystals exhibits a shift to higher energy with decreasing size due to quantum confinement effects. Research in this field has employed primarily optical techniques to study nanocrystals, and in this respect this system has been investigated extensively. In addition, one is able to synthesize monodisperse, crystalline particles of CdS, CdSe, Si, InP, InAs, as well as CdS/HgS/CdS and CdSe/CdS composites. However, optical spectroscopies have proven ambiguous in determining the degree to which electronic excitations are interior or surface admixtures or giving a complete picture of the density of states. Photoemission is a useful technique for understanding the electronic structure of nanocrystals and the effects of quantum confinement, chemical environments of the nanocrystals, and surface coverages. Of particular interest to the authors is the surface composition and structure of these particles, for they have found that much of the behavior of nanocrystals is governed by their surface. Previously, the authors had performed x-ray photoelectron spectroscopy (XPS) on CdSe nanocrystals. XPS has proven to be a powerful tool in that it allows one to determine the composition of the nanocrystal surface

[en] The aim of this work is to characterize the orbital structure of the fullerenes, and to pursue its evolution from a cluster to the infinite solid. For obtaining a complete picture of the electronic structure the authors compare a variety of experimental techniques, i.e. photoemission and core level emission for occupied orbitals and inverse photoemission and core level absorption for unoccupied orbitals. Their experimental results focus on optical probes involving the C 1s core level, i.e. absorption via transitions from the C 1s level into unoccupied π* and σ* orbitals and emission involving transitions from occupied orbitals into a C 1s hole. Due to the simplicity of the C 1s level there exist clear selection rules. For example, only transitions to and from orbitals with p-character are dipole-allowed. These results on the p-projected density of states are compared with inverse photoemission and photoemission results, where the selection rules are less definitive. In addition, a first-principles quasiparticle calculation of the density of states is used to assign the orbital features. The spectra from C₆₀ and C₇₀ are still far from their infinite analog, i.e., graphite, which is also measured with the same techniques. In order to determine the effect of electron transfer onto C₆₀, as in superconducting alkali fullerides, the authors are studying resonant emission of C₆₀. An electron is placed in the lowest unoccupied molecular orbital (LUMO) by optical absorption from the C 1s level and the C 1s emission detected in the presence of this spectator electron

[en] The authors have determined the atomic spatial structure of c(2x2) N2Ni(100) with Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) from the nitrogen 1s core level using monochromatized x-rays from beamline 6.1 at SSRL and beamline 9.3.2 at the ALS. The chemically shifted N 1s peak intensities were summed together to obtain ARPEFS curves for both nitrogen atoms in the molecule. They used a new, highly-optimized program based on the Rehr-Albers scattering matrix formalism to find the adsorption site and to quantitatively determine the bond-lengths. The nitrogen molecule stands upright at an atop site, with a N-Ni bond length of 2.25(1) angstrom, a N-N bond length of 1.10(7) angstrom, and a first layer Ni-Ni spacing of 1.76(4) angstrom. The shake-up peak shows an identical ARPEFS diffraction pattern, confirming its intrinsic nature and supporting a previous use of this feature to decompose the peak into contributions from the chemically inequivalent nitrogen atoms. Comparison to a previously published theoretical treatment of N-N-Ni and experimental structures of analogous adsorbate systems demonstrates the importance of adsorbate-adsorbate interactions in weakly chemisorbed systems

No abstract available

[en] Mass transfer over stretching surface with variable concentration in a transverse magnetic field is examined. The boundary layer equations are transformed to ordinary differential equations, containing the magnetic parameter Mn and the concentration parameter λ. Numerical results for different values of the Schmidt number are presented. It is observed that the local mass transfer and concentration profile are very sensitive to the change in the values of the magnetic parameter Mn and the concentration parameter λ

[en] We have measured autocorrelation functions for light scattered from capillary waves at the interface in a near-critical binary liquid mixture both at two-phase equilibrium and after abruptly raising the temperature to drive the system toward one-phase equilibrium. Use of the capillary-wave dispersion relation allows the extraction of an effective ''surface tension.'' This surface tension represents a dynamical integrity of the nonequilibrium interface which may affect pattern formation when the interface is driven

[en] In this paper, the authors report results from a first-principles local spin density quantum mechanical study of the energetics and elastic properties of a series of magnesium-oxygen clusters of various morphologies. The role of quantum effect, e.g. covalency, in the bonding character of diatomic M_gO is determined by comparison of classical and quantum restoring force curves. The dependence of binding properties on geometry and metal to oxygen ratio is determined by comparison of binding energy curves for a series of clusters. Results show that while gross features of the binding curves may be represented by simple interatomic potentials, details require the many body corrections of a full quantum treatment

[en] ESR (Electron Spin Resonance) spectra in X-band and at room temperature, of dental composites containing Bis-GMA type resin were obtained after irradiated wit conventional curing lamp of visible-light and laser light of red, green and blue colors. The blue light is the most suitable to produce methacrylate free radicals needed to its polymerization. However, Vickers hardness number determined in samples cured with conventional light indicated that their hardness number are equivalent to that obtained with blue light even producing less radicals, probably because conventional lamp generates more heat in the sample which helps its polymerization. Examining samples irradiated with green light, which is inadequate for usual practice by its lacking in energy, it has observed that this material has a striking ability to post cure by itself. It has concluded that the observation made by Ottaviani and collaborators, in a previous publication, that the time recommended by composite makers was insufficient, analyzing only ESR measurements, must be revised. (author)