Materials Literature
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A new ceramic, nitrogen-stabilized aluminum oxide spinel (ALON), has been developed at AMMRC which may have distinct advantages over sintered polycrystalline a-A1<sub>2</sub>0<sub>3</sub>. This material is isotropic and has been fabricated into dense, transparent bodies with the following properties: Knoop (100) hardn…
The infrared cut-off of glasses is primarily determined by the frequency of vibration of the cation-anion bonds. In order to extend infrared transmittance to longer wavelengths cations and anions of larger sizes and lower field strengths should be used; however, physical and chemical properties become poorer. For sili…
The valence of an atom occupying a particular crystal lattice site can be determined from the chemical shift in a transmission electron energy-loss spectrum obtained with the intensity of the incident electron wave maximized at that site by dynamical electron diffraction. The new technique is demonstrated by determini…
A laser-induced pressure-pulse method for measuring the charge distribution in (10 to 100 \ensuremath{\mu}m thick) dielectric samples with a resolution of about 4 \ensuremath{\mu} m is described. A short ( ns) energetic light pulse from a neodymium-doped yttrium aluminum garnet laser is applied to a specially coated s…
V centres have been studied in pure KBr using optical absorption and Raman scattering experiments. Raman spectra show that Br 3- ions can be created in samples X-irradiated at 190K. They are correlated with the V 4 absorption band (270 nm). After X-irradiation at room temperature, Br 2 -type (Br 5- centres are created…
Constant-psi constant-delta contour maps in the reduced angle-of-incidence-film-thickness plane that are useful in ellipsometry and in design of reflection-type optical devices are discussed. As a specific example, a contour map is given for the SiO(2)-Si film-substrate system at the 6328-A He-Ne laser wavelength.
Low-temperature microwave conductivity data for $\mathrm{Na}\ensuremath{\beta}$-alumina have been analyzed in terms of the standard tunneling model of disorder-induced two-level states. In addition, the microwave dielectric constant has been studied as a function of temperature between 0.3 and 15 K for Na, K, and ${\m…
The lattice vibration in 2$H$-Ta${\mathrm{Se}}_{2}$ was investigated by one- and two-phonon Raman scattering in the normal and the charge-density-wave (CDW) phases. From the integrated scattering intensity of the two-phonon-process peak, the temperature dependence of the generalized electronic susceptibility was obtai…
The theory of natural optical activity in the 4f→4f transitions of trigonal dihedral (D3) lanthanide(III) complexes is developed within the framework of a crystal field model. Within this model, both the chiral and achiral components of the crystal field are represented in terms of multipole-point charge and multipole…
Analysis of the temperature-dependent decay of surface voltage on an amorphous film after charging but prior to exposure (xerographic dark decay) and of residual decay after exposure can, in combination, be used to map the density of states and position the Fermi level. The procedure is illustrated for $a$-Se where bo…
A reexamination is made of previous resistivity data of the Ti${\mathrm{O}}_{0.80\ensuremath{-}1.23}$ metallic oxide system, in which very large positive and negative temperature coefficients of resistivity $\ensuremath{\alpha}$ are observed. Ti${\mathrm{O}}_{0.80\ensuremath{-}1.23}$ samples contain a large number of…
The electronic density-of-states and the partial-density-of-states functions for the 14 primary bands of the $\mathrm{AB}{\mathrm{O}}_{3}$ cubic $d$-band perovskites are derived as simple, closed form, analytical formulas with the use of an empirical linear-combinations-of-atomic-orbitals model. Comparisons of the mod…
Recent experimental evidence has established that the scattering of phonons by dislocations at low temperatures in [110] LiF rods is primarily a dynamic rather than a static process, but calculations of the effects of vibrating dislocations have failed to provide quantitative agreement with experimental observations o…
The interaction of H2O with the clean Fe(110) surface, Fe(110) surfaces with absorbed oxygen, and Fe(110) surfaces after bulk oxygen penetration were investigated using UPS. At 225 K, surface absorbed hydroxyl groups are present on all surfaces studied. On initially clean Fe(110) and surfaces with up to half monolayer…
Two clearly defined and chemically inequivalent Sn sites in the alloy glass (${\mathrm{Ge}}_{0.99}$${\mathrm{Sn}}_{0.01}$)${\mathrm{Se}}_{2}$ are observed using M\"ossbauer spectroscopy. These sites are identified with Sn impurity atoms replacing Ge in tetrahedral ${\mathrm{G}\mathrm{e}({\mathrm{Se}}_{1/2})}_{4}$ unit…
${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}$ Te alloys possess a homogeneous crystal phase having a zinc-blende structure for $0\ensuremath{\le}x\ensuremath{\le}0.7$. Their Raman spectra exhibit two pairs of sharp lines characteristic of the zone center "CdTe-like" and "MnTe-like" LO-TO modes. Some quasicontinu…
It is shown that by using the conical diffraction mount existing echelle gratings can be used at grazing incidence to achieve high spectral resolution in the extreme UV and soft x rays. Design considerations for grazing incidence echelle spectrographs are examined, and two sample designs are discussed. The first, for…
The OH-stretching fundamental, and the first, second, and third OH overtone vibrations have been examined using pure, GeO2-doped, graded index, fused silica optical fibers having OH contents from &lt;1 ppm to ≳103 ppm. The previously reported component substructure of the fundamental OH-stretching contour was foun…
A coupled Hartree–Fock method with individual gauge for localized orbitals (IGLO) proposed previously is reformulated and applied to the calculation of the magnetic susceptibility χ and the chemical NMR-shifts σ of various small molecules. The agreement with experiment is usually very good. Unlike in traditional metho…
Spin waves, elastic waves and their magnetostrictive coupling in KNiF 3 are studied as functions of temperature and of applied magnetic field by Brillouin scattering and ultrasonic measurements. The light scattering data provide the magnetic and elastic coefficients; in addition, they enable magnetostrictive coefficie…