Materials Literature
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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…
A study is made of relaxation processes in polymer molecules which proceed via conformational transitions of the chain backbone from one rotational isomeric state to another. The conformational time-correlation functions are determined for several models of the process. Each model allows for the occurrence of both ind…
The rate of molecular reorientation in solid ${\mathrm{N}}_{2}$O and $\ensuremath{\alpha}$-CO is obtained from audio-frequency dielectric measurements. Both sets of data obey the Arrhenius expression. The rates extrapolate to mean reorientation times of one hour at temperatures well above the predicted dipolar orderin…
The mixing effects in the fused system LiCl–KCl are studied by molecular dynamics simulation. The predominant contribution of the Coulombic interaction is clearly detected, its nonlinear variation gives rise to the main part of the excess internal energy. This change reflects the structural ionic arrangement; at high…
The core-level binding-energy shifts for surface atoms relative to bulk atoms ("surface shifts") have been measured for the $2p$ levels of Na (220 meV) and Mg (140 meV) using synchrotron-radiation-excited photoelectron spectroscopy. For Al, both a surface shift and a broadening are considered. The sign and magnitude o…
A b initio LCAO SCF MO calculations were carried out on Fe-porphine, Fe-porphine-pyridine, and Fe-porphine-pyridine-carbonmonoxide which are typical intermediate-, high-, and low-spin complexes, respectively. Mössbauer spectra of ferrous porphyrins were analyzed theoretically by the evaluation of isomer shift (IS), qu…
Raman scattering and optical-absorption spectra in low-pressure, rf-sputtered $a$-Si are shown to exhibit a continuous variation with deposition temperature. A direct correspondence between changes in the inverse width of the TO-like phonon band and the optical gap is observed in sputtered and chemical-vapor-deposited…
X-ray-absorption $K$-edge spectra of the V $1s$ core level in V${\mathrm{O}}_{2}$ exhibit broadening and splitting of the $1s\ensuremath{\rightarrow}{t}_{2g}$ core transition at the $K$ threshold at the semiconductor-to-metal phase transition. The three components observed in the metallic phase are assigned to final-s…
The bulk moduli of rocksalt-type divalent and trivalent rare-earth ($R$) monochalcogenides exhibit a linear relationship when plotted on a log-log scale against the unit-cell volume, but fall on two distinct straight lines according to the effective valence product of the compound. By comparing the bulk modulus ratio…
We report the first angle-resolved photoemission spectra (ARPES) of polar and nonpolar surfaces of an ionic wurtzite-type compound semiconductor. We present experimental results obtained at photon energies between 20 and 80 eV on the polar zinc and oxygen and the nonpolar ($10\overline{1}0$) surfaces of ZnO and identi…
Semiconducting organometallic films such as copper tetracyanoquinodimethane (CuTCNQ) have been observed to switch between two stable states when exposed to optical radiation. Observations of switching between two states in these films have been made by Raman spectroscopic methods and direct observation of electrical r…
The Raman spectra of tetragonal TlIn${\mathrm{Se}}_{2}$ and monoclinic TlGa${\mathrm{S}}_{2}$, TlGa${\mathrm{Se}}_{2}$, and TlIn${\mathrm{S}}_{2}$ have been investigated as a function of pressure at constant temperatures (300 and 110 K, TlIn${\mathrm{Se}}_{2}$ only at 110 K). Contrary to earlier assignment the structu…