Materials Literature
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The linear chain model of Wieting is used here to predict the frequency of the E 1g Raman active mode in the layer compound 2H-niobium selenide. A careful Raman study near this predicted frequency has shown a weak band whose polarisation suggests that it is the E 1g mode.
The latest model proposed for the P2 centre shows that the paramagnetic electron is associated mainly with one carbon atom. The observation of the carbon-13 hyperfine interaction with this carbon is reported, and the appropriate hyperfine parameters for this interaction are given.
Time correlation formulae for the phenomenological coefficients for isothermal matter transport in solids have been derived earlier by application of the linear response method to a system whose kinetics is characterised by the jump probabilities for vacancy, interstitial or other defect mechanisms. These formulae are…
The literature data on polyelectrolyte complexes (PEC), mainly non-stoichiometric PEC (N-PEC), are analysed. Interpolyelectrolyte reactions, leading to the formation of N-PEC as well as the methods of synthesis of these macromolecular compounds are examined. The structure of water-soluble N-PEC, which constitute a new…
Picosecond self-diffraction is observed from transient orientational gratings produced in germanium by an anisotropic (in $k$ space) filling of the optically coupled states by direct absorption of the nearly monochromatic polarized exciting radiation, the first direct observation of anisotropic state filling in semico…
An inelastic scattering process is observed between 2.5 and 4.0 eV when clusters of 10- to 50-nm-diam aluminum spheres are excited by a 1-nm-diam probe of 100-keV electrons. This inelastic scattering is a maximum when the incident electron probe is positioned within 10 nm of the smaller of two touching spheres. The ob…
ABSTRACT The erosion and cleaning effects of jets are enhanced when the degree of cavitation occurring on or near the bottom of the hole is increased. A new, STRuctured Acoustically Tuned Oscillating Jet ("STRATOJET") system causes the formation of large discrete vortex rings that promote cavitation to depths several…
Four UHV spectroscopies used for the compositional and chemical analysis of surfaces are discussed. These are X-ray Photoemission, Auger Spectroscopy, Secondary Ion Mass Spectroscopy, and Ion Scattering (both low and high energy). Descriptions of the basic processes and information contents are given, followed by a co…
Gd 3+ in glasses exhibit sharp g approximately=6.0 features in the EPR spectra. It is demonstrated that these features can be adequately accounted for by using the 'rhombic' spin Hamiltonian H=g c beta H.S+D(S z 2 -(S/3)(S+1))+E(S x 2 -S y 2 ) in the strong crystal field case. Computer simulations of the experimental…
Magnetic susceptibility, Mossbauer spectroscopy and powder neutron diffraction experiments have shown that iron(III) phosphate, FePO 4 , undergoes a novel spin reorientation transition at 17K between two antiferromagnetic phases. The ordered magnetic moments lie in the basal plane of the trigonal unit cell between the…
Transverse magnetoresistance is measured at magnetic fields up to 6.5 T at temperatures of 77K and 4.2K for highly oriented graphites; four samples of kish graphite with different crystallinity. The effect of the structural perfection of graphite on the field dependence of the exponent n in he magnetoresistance Delta…
The rate of oxidation of ammonia at atmospheric pressure on single wires and ribbons has been determined as a function of a gas flow rate and catalyst size. In agreement with boundary layer diffusion theory the function rx 1/2, where r is the average rate of reaction/unit area, and x is the length of the surface measu…
The rate of catalytic "NO" reduction by hydrogen and carbon monoxide over a char surface was measured and compared with the rate of noncatalytic "NO" reduction by char which has been previously reported to have a significant effect on "NO" emission control in a fluidized bed combustor of coal. In the presence of hydro…
X-ray diffraction peaks recorded from hematite derived from goethite by a dehydration reaction and its isostructural system corundum from diaspore exhibit systematic peak broadening for l ≠ 3n, which corresponds to the reflections belonging to either the obverse or reverse variant of hematite. The peak width of l = 3n…
Compositions GdF3Ce, Tb are efficient green phosphors under short-wavelength ultraviolet excitation. The Ce3+ → Tb3+ energy transfer occurs via the Gd3+ ions. Without Gd3+ ions the total transfer efficiency is considerably lower.
Optical data from single-crystal Mg[Pt${(\mathrm{CN})}_{4}$]\ifmmode\cdot\else\textperiodcentered\fi{}7${\mathrm{H}}_{2}$O together with calculations of the exciton energies allow us to draw conclusions on the existence of a self-trapped exciton, which becomes metastable by changing the relevant material parameters wi…
The crystal structure of the organic charge-transfer salt DBTTF–TCNQF4 is reported. The structure has been determined by single-crystal x-ray diffraction techniques and has been shown to consist of segregated stacks of donor and acceptor molecules. Within both the donor and acceptor stacks, significant dimerization is…
The low-frequency properties of a disordered one-dimensional diffusion model are determined. Of particular interest is the case where the distribution of hopping elements diverges for small values of the hopping elements. The density of states and the leading correction terms are calculated at low frequencies and the…
We describe a quantum Hamiltonian in one dimension with a quasiperiodic interaction, giving rise to a metal-insulator transition at high coupling. This model applies to a linear wave propagation in a modulated medium, naturally resulting in potentials with incommensurate periods, as is the case for organic linear cond…
Experimental results on Cu(001), Ni(001), and Ni(110) with the use of the newly developed technique of $k$-resolved inverse photoelectron spectroscopy (or angle-resolved ultraviolet bremsstrahlung isochromat spectroscopy) are presented and compared with the predictions of bulk band-structure theory. A theoretical mode…