Materials Literature
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The optical spectra of the lanthanides doped into single crystal LaF3 have been interpreted in terms of transitions within 4f N configurations. Energy matrices combining free-ion terms with a crystal field for an approximate model which assumes C2v instead of the actual C2 site symmetry were diagonalized. Excellent co…
The results obtained from studying the reactions of N-chloramines, N-halocarbamates, and N-haloamides of carboxylic, sulphonic, and phosphoric acids with unsaturated compounds have been correlated and classified. It is shown that the direction of addition of N-haloamines and N-haloamides to alkenes, dienes, alkenynes,…
Low-energy excitations between charge-density-wave metastable states are revealed in low-temperature specific-heat measurements in quasi-one-dimensional materials as an excess contribution (to the lattice one) following a ${\mathrm{C}}_{\mathrm{p}}$=${\mathrm{T}}^{\ensuremath{\nu}}$ law with \ensuremath{\nu}<1. In…
A new reconstruction structure, having a \ensuremath{\surd}3\ifmmode\times\else\texttimes\fi{}\ensuremath{\surd}3)R30\ifmmode^\circ\else\textdegree\fi{} unit cell, is reported for the Si(111) surface. Analysis of low-energy electron-diffraction intensity spectra by multiple-scattering theory revealed a vacancy model.…
We have measured the full spectrum of the third-order optical susceptibiltiy, ${\ensuremath{\chi}}^{(3)}$(\ensuremath{\omega}), in polyacetylene using an infrared free-electron laser. The magnitude of ${\ensuremath{\chi}}^{(3)}$(\ensuremath{\omega}) reaches \ensuremath{\sim}${10}^{\mathrm{\ensuremath{-}}8}$ esu at 0.6…
High-resolution, small-angle, synchrotron x-ray-scattering techniques were used to determine the phase diagram, structure factor, and pair distribution function for a charged colloidal suspension from 6% to 30% volume fraction. The expected correlated liquid and fcc and bcc solid phases were observed along with a glas…
Abstract are prepared by solid state reactions and their structures are studied (XRD).
The formation of the liquid, crystalline and glassy states in binary mixtures of aqueous suspensions of charged polystyrene spheres of different sizes is investigated using molecular dynamics simulations. It is shown that on merely mixing the particles, crystalline (a substitutional body-centered cubic) and glassy sta…
Recently, there has been a great deal of interest in Na2S⋅9H2O as a passivating chemical treatment for GaAs surfaces. It has been shown that it reduces the high surface recombination velocity characteristic of GaAs surfaces, and may offer hope for ‘‘unpinning’’ the surface Fermi level. We have used photoemission spect…
The nature of the 2.7-eV photoluminescence in as-manufactured oxygen-deficient high-purity silica glasses is studied. Luminescence lifetime measurements and ab initio molecular-orbital calculations are consistent with the luminescence being a triplet-to-ground transition of a neutral oxygen-vacancy defect (?Si-Si?).
The related micromagnetic techniques of Barkhausen emission (BE) and magneto-acoustic emission (MAE) are used to study neutron damage effects in α-iron and iron—copper alloys following irradiation to 2.4 to 2.9 × 1019 n cm−2 (> 1 MeV) at 60 and 290 °C, respectively. The role of initial heat treatment and thermal agein…
Polarized Raman spectra of LaNbO4 which is known to show a peculiar behavior of state shift in the ferroelastic phase are measured. All the observed bands are assigned. Raman spectra measurements are made on a newly extended region of a domain under an external stress at 90 K. The results reveal that the difference in…
C20H20O4S, Mr = 356.4, monoclinic, P2(1)/c, a = 5.045 (3), b = 29.115 (7), c = 11.924 (2) A, beta = 94.82 (3) degrees, V = 1745.2 A3, Z = 4, Dx = 1.357 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 17.86 cm-1, F(000) = 752, T = 298 K, R = 0.038, wR = 0.044 for 1212 reflections, I greater than 3 sigma(I). In the crystal,…
The photoluminescence of several natural and synthetic diamonds of type I and type II has been examined in the spectral range 1.35--1.85 eV (920--670 nm) at 300 and 79 K at ambient pressure. Two emission bands with zero-phonon lines at 1.575 and 1.770 eV are observed in all yellow type-Ia natural diamonds. These bands…
The spectral dependence of the infrared absorption cross section of As in Si near 0 K has been determined from infrared transmission measurements for three As concentrations (5.3, 8.4, and 15.9 x 10(17) cm(-3)) in the impurity band regime. The results demonstrate some features of physical interest. With increasing As…
A screened Rutherford cross section is modified by means of a correction factor to obtain the proper transport cross section computed by partial-wave analysis. The correction factor is tabulated for electron energies in the range 0–100 keV and for elements in the range from Z=4 to 82. The modified screened Rutherford…
We have performed photoelectron spectroscopy of the clean GaP(110) surface, obtained by cleaving n-type specimens. The results show that Fermi-level stabilization occurs in a wide range of positions. In some cases nearly flat bands were obtained. The surface Fermi-level position in n-type GaP(110) is then due to extri…
Ultraviolet photoemission spectroscopy, Auger-electron spectroscopy, and low-energy electron diffraction have been used to study the electronic structure of CoO(100) surfaces obtained by cleaving single crystals in ultrahigh vacuum. Two distinct types of surface defect states that can be produced by ${\mathrm{Ar}}^{+}…
Alkali-metal superoxides have been prepared in situ and studied by ultraviolet photoemission with use of synchrotron radiation. A consistent spectral assignment of the valence-band emission features has been achieved for the first time. The photoemission process corresponds to a transition from ${\mathrm{O}}_{2}^{\mat…
Dielectric properties of hexagonal BaTiO 3 have been studied under a variety of conditions. Anomalies are found in the dielectric constant ε ' c along the hexagonal c -axis: a cusp-like anomaly at T 0 =222 K and a peak at the ferroelectric Curie point of T c =74 K. After a dc field cooling treatment applied along the…