Materials Literature
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Polyacetylene (CH)z is a simple conjugated polymeric system, the electrical behaviour of which is considerably modified by doping processes: from an insulating behaviour it successively becomes semi-conducting and even metallic. In this work first the dopant profiles through the sample is measured and the macroscopic…
An electron trap which strongly affects the photoconductivity of colored $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ has been investigated from 10 to 300 K. The trap, which also causes the 260-K thermoluminescence peak and makes possible the interconversion of $F$ and ${F}^{+}$ centers by opti…
Photodissociation of XeF2 with synchrotron light pulses (0.3 ns duration) has been used as the source of the XeF(B, C, and D) excited states. The time-resolved profiles of the intensity of the resulting fluorescence have been recorded and partially analyzed. Most of the measurements were made in the strong XeF2 absorp…
The solid–vapor equilibrium line and the liquid–vapor equilibrium line near the melting region for classical two-dimensional systems of particles interacting by Lennard-Jones (12,6) pair potentials are determined from Monte Carlo simulations with 224 particles. Structural and thermodynamic properties are evaluated for…
A general formula is derived for the electron occupation numbers appropriate for multicharge centers in semiconductors, including excited states. The results are used to rederive and generalize several formulas of interest in the literature, in order to show exactly how the degeneracies of individual states enter in.…
A theoretical study of the electronic structure of amorphous $\mathrm{Si}{\mathrm{O}}_{x}$ is performed. The calculation is done using a realistic tight-binding Hamiltonian for a cluster-Bethe-lattice model. Results of the calculations are in good agreement with optical-absorption measurements for the entire range of…
The quantum statistical mechanics of a polarizable fluid model is considered using a path-integral approach. The quantum mechanical partition function associated with the internal degrees of freedom of each molecule is approximated by a classical partition function of a polymer ring, while the center-of-mass motion of…
Synchrotron radiation at the Synchrotron Ultraviolet Radiation Facility at the National Bureau of Standards has been employed to study the adsorption of oxygen on a Ti(001) surface using photon-stimulated desorption (PSD), electron-stimulated desorption (ESD), and ultraviolet photoemission spectroscopy (UPS). The domi…
The ground-state properties of diamond are investigated using an ab initio density-functional pseudopotential scheme. The calculated equilibrium lattice constant, cohesive energy, and bulk modulus are in excellent agreement with experiment. Unlike Si, a double hump is found in the valence-electron charge density along…
Excited $s$ states are added to the minimal-basis tight-binding theory of covalent solids using Louie's perturbation approach. This brings the conduction bands into better accord with experiment without appreciably complicating the calculation of properties in the bond-orbital approximation. Universal interatomic matr…
We report on a high-resolution photoluminescence and absorption study with the application of external stress and magnetic fields on the 0.97-eV ($G$) line. We determine the symmetry of the related center to be monoclinic $I$. It is shown that satellite lines $E$, ${E}^{\ensuremath{'}}$, and ${E}^{*}$, which are obser…
Elastic and hydrodynamic properties of biaxial nematics of D2 symmetry are theoretically studied. The treatment follows closely the classical formalism used for solids which is extended by inclusion of director fields. The resulting theory is a generalization of the well-established theory of uniaxial nematics. The el…
We present measurements of light emission from Al-${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$-Ag tunnel junctions on holographically produced, sinusoidal profile gratings. Sharp angle tunable emission peaks result from coupling out of the Ag-vacuum fast surface-plasmon polariton by the grating structure. The dependences of…
A method is proposed for calculating the photoionisation cross sections of many-electron atoms near the ionisation threshold of an inner shell. The method takes into account the variation of the field in which a photoelectron moves due to creation of a deep vacancy and its decay. For example the cross section of the 1…
The dielectric strength of hexafluoropropylene has been investigated under breakdown and prebreakdown conditions in the pressure range from 0.07 to 2 bar. Breakdown voltages measured in a uniform field gap have been found to be in good agreement with intrinsic dielectric strength evaluated from measurements of net ion…
The Ni L 2,3 M 4,5 M 4,5 Auger spectra, the conduction band X-ray photoemission spectra and the Ni 2p 3/2 X-ray photoemission spectra have been measured for Ni, Ni 50 Zn 50 , Ni 20 Zn 80 and Ni 50 Al 50 . The shape of the L 3 M 4,5 M 4,5 Auger spectrum changes as the band structure of the alloy changes in a way which…
Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6‐Oxo‐isophorone. II. A Novel Concept for the Synthesis of (3 RS , 3′ RS )‐Astaxanthin Starting from 6‐oxo‐isophorone ( 2 ) a new concept for a seven‐step synthesis of (3 RS , 3′ RS )‐astaxanthin ( 1 ) has been developed. As a key feature…
An experimental small-angle x-ray scattering study of a phase-separating quasibinary glass ${\mathrm{B}}_{2}$${\mathrm{O}}_{3}$-PbO(${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$) is compared with the predictions of nonlinear theories for advanced stages of decomposition. The time evolution of the moments and the scaling of th…
Spin-polarized, energy-resolved photoemission using monochromatized synchrotron radiation shows that the 6-eV satellite of Ni is highly spin polarized near to the $3p\ensuremath{-}3d$ excitation threshold ($h\ensuremath{\nu}\ensuremath{\approx}65$ eV). This observation proves the validity of the model involving ${M}_{…
Three-dimensional bond orientational order is studied via computer simulations of 864 particles interacting through a Lennard-Jones pair potential. Long-range orientational fluctuations appear upon supercooling about ten percent below the equilibrium melting temperature. The fluctuations suggest a broken icosahedral s…