ChemInform Abstract: The Layered Compounds AMV(PO4)2 (A: K, Rb, Cs and M: Sb, Nb, Ta)
Abstract are prepared by solid state reactions and their structures are studied (XRD).
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Liquid, crystalline and glassy states of binary charged colloidal suspensions
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…
Photoemission study of the band bending and chemistry of sodium sulfide on GaAs (100)
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…
2.7-eV luminescence in as-manufactured high-purity silica glass
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?).
Radiation Damage Studies in Model Ferritic Alloys Using Micromagnetic Techniques
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…
Raman Spectra of LaNbO4 in the Ferroelastic Phase and the Relaxation after the State Shift
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…
Short S.O contacts: structure of 2,5-bis(p-methoxyphenylhydroxymethyl)thiophene
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,…
Near-infrared photoluminescence bands in diamond
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…
Infrared absorption cross section of arsenic in silicon in the impurity band region of concentration
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…
Simple method for the simulation of multiple elastic scattering of electrons
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…
Fermi-level pinning and intrinsic surface states in cleaved GaP
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…
Electronic properties of CoO(100) surfaces: Defects and chemisorption
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 oxides. I. Molecular and crystal-field effects in photoemission
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 Ferroelectric Hexagonal BaTiO3
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…
Direct determination of the self-diffusion mechanism in bccβ-titanium
With quasielastic neutron scattering the elementary diffusion jump (length and direction) and the jump frequency in bcc \ensuremath{\beta}-Ti single crystals have been determined at temperatures between 1460 and 1580 \ifmmode^\circ\else\textdegree\fi{}C. Supplementary measurements on polycrystalline samples extended t…
General dispersion formulas for molecular third-order nonlinear optical properties
For the electronic optical hyperpolarizabilities for molecules γω∥=γZZZZ(−ωσ;ω1, ω2,ω3) and γω⊥=γZXXZ(−ωσ;ω1, ω2,ω3), where Z and X are laboratory axes and ωσ=ω1+ω2+ω3, it is demonstrated that the following relationships exist: (1) γω∥/γ0∥ =1+Aω2L+⋅⋅⋅ , where ω2L=ω2σ+ ω21+ω22+ω23 and A is frequency independent; (2) γω…
Nonlinear lattice relaxation of photogenerated charge-transfer excitation in halogen-bridged mixed-valence metal complexes. II. Polaron channel
The one-dimensional extended Peierls-Hubbard model with half-filled-band electrons is studied in order to clarify the lattice relaxation path of the photogenerated charge-transfer excitation in halogen-bridged mixed-valence metal complexes. The ground and excited states are calculated within mean-field theory for elec…
Theoretical analysis of orbital and correlation effects on the electronic absorption spectrum of theMnS4center in zinc-blende crystals
Optical excitation energies ascribed to the ${\mathrm{Mn}}^{2+}$ center in ZnS:Mn are calculated from Gaussian-based self-consistent-field (SCF) molecular orbitals (MO's) obtained for the tetrahedral ${\mathrm{MnS}}_{4}^{6\mathrm{\ensuremath{-}}}$ cluster at three Mn-S distances in a static external potential, followe…
Light-induced oxidation and band-edge shifts in thermally evaporated films of germanium chalcogenide glasses
Films of amorphous ${\mathrm{GeSe}}_{2}$, ${\mathrm{GeSe}}_{3}$, and ${\mathrm{GeS}}_{2}$ have been deposited at various angles of incidence onto appropriate substrates and the nature of the photoinduced oxidation (as monitored by the Ge-O peak at \ensuremath{\sim}800 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in the…
Conductivity as a function of conjugation length: Theory and experiment for conducting polymer complexes
The dependence of electronic conductivity upon the length (L) of conjugated segments is calculated for conducting polymers for which (1) interruptions in conjugation on neighboring chains are uncorrelated, (2) all chains are equivalent, and (3) intersegment hopping controls chain-direction conductivity. If interchain…