Materials Literature
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Vibronic wavefunctions for trimers are used to calculate the A and B parameters characteristic of MCD spectra. In the weak-coupling limit both the A and the B parameters are zero for s = 0 states and nonzero for s = ±1 states. In the strong-coupling limit, the vibrationally induced 0–1 transition has nonzero A and B p…
The solution absorption spectrum of Es3+ has been measured in the region 10 000–34 000 cm−1. The observed band structure has been interpreted in terms of free-ion energy levels calculated using parameters that are consistent with those obtained in analyses of the specta of earlier members of the 5fN-series. The correl…
Crystals of DL-aspartic acid (C4NO4H7) were grown at room temperature from an aqueous solution of the commercially available sample. The crystals be- long to the monoclinic system with cell dimensions a= 18.947+0.002, b= 7.433 + 0.001, c=9.184 + 0.001 A and fl=123.75+0-02 °. The systematic absences are: hkl, h + k = 2…
Single crystals of silicon telluride, which has an unusual 2:3 stoichiometry, have been grown by a chemical vapor deposition technique. A photoluminescence level at 1.3 eV has been found as well as strong EPR signals, suggesting defects in the crystal which also could explain other unusual features. Thin films and bul…
α-VPO 5 crystallizes in the tetragonal space group P4/n with a = 6.014(7) and c = 4.434(2) Å. The structure, isotypic with that of α-VSO 5 , was refined by full-matrix least-squares method to an R value of 0.089 using 239 independent reflections. The vanadium ion lies on a crystallographic four-fold axis, as does one…
The Seebeck coefficient $\ensuremath{\alpha}$ for pure and V-doped ${\mathrm{Ti}}_{2}$${\mathrm{O}}_{3}$ single crystals has been measured between 54 and 500 K. A very strong peak in $\ensuremath{\alpha}$ near 75 K for ${\mathrm{Ti}}_{2}$${\mathrm{O}}_{3}$ is interpreted as arising from phonon-drag effects; this peak…
The electron spin resonance of the Gd3+ ion has been studied in two series of glasses having the molar compositions 6SiO2:5Na2O: x (Gd2O3 + Y2O3) with 0 ≤ x ≤ 0.5 and 500SiO2: x Na2O:1Gd2O3 with 2.5 ≤ x ≤ 494. The spectra were nearly independent of temperature and sample composition, but varied strongly with microwave…
The evolution with $x$ of the monoclinic-to-tetragonal transition temperature and of the room-temperature monoclinic structures of the system ${\mathrm{V}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x}{\mathrm{O}}_{2}$ have been reexamined and extended to cover the entire solid-solution range $0\ensuremath{\le}x<0.20$. The s…
We report the preparation of intercalation compounds of 2H–TaS2 with post transition period elements. In general we find that elements to the left of the metalloid line in the periodic table will intercalate TaS2. Crystallographic lattice parameters, the maximum amount intercalated per Ta, magnetic susceptibility, and…
A phenomenological dielectric approximation is proposed for studying the response of metal surfaces to external charge distributions and is illustrated by detailed calculations using the Thomas-Fermi model. The procedure is based on the replacement of the dielectric-response kernel in a constitutive relation by its as…
By using the techniques of wavelength-modulation spectroscopy, we have measured the reflectivity $R(\ensuremath{\omega})$ and the derivative of the reflectivity, $\frac{(\frac{1}{R})dR}{d\ensuremath{\omega}}$, for PbTe, PbSe, and PbS from 1.5 to 6 eV. We have independently calculated the band structure, frequency-depe…
We discuss the threshold conditions for the nucleation of a static Helfrich distortion of a planar cholesteric structure under a magnetic field or an ac electric field applied parallel to the helical axis. In opposition to the case of nematics, the magnetic threshold in cholesterics is definitely lower than the thresh…
We observe a second-order nematic to smectic-$A$ phase transition in $p$-nitrilebenzylidene-$p$-octyloxyaniline using the Rayleigh scattering technique. The twist elastic constant ${K}_{22}$ diverges at the transition, with the critical exponent $\ensuremath{\nu}=0.66\ifmmode\pm\else\textpm\fi{}0.05$ in agreement with…
The viscosity of liquid anorthite has been determined over the temperature ranges between 1450°–1620°C and 820°–950°C. The high-temperature data agree well with previous experimental data and with predictions of the Bottinga and Weill model. The overall log (viscosity) versus 1/T relation exhibits pronounced and rathe…
Tungsten carbide catalyzes the formation of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the presence of water, and the isomerization of 2,2-dimethylpropane to 2-methylbutane. This catalytic behavior, which is typical of platinum, is not exhibited at all by tung…
The splay and bend elastic constants of nematic $p$-cyanobenzylidene-${p}^{\ensuremath{'}}$-octyloxyaniline have been measured as a function of temperature. The bend constant diverges near the nematic-smectic-$A$ phase change, with the temperature dependence predicted by de Gennes. The splay constant shows no anomaly,…
A brief review is first made of systems for which the spin-1/2 Ising model in a transverse field provides a useful description (insulating magnetic systems, order-disorder ferroelectrics, cooperative Jahn-Teller systems and other systems with 'pseudo-spin'- phonon interactions). A perturbation expansion is then develo…
One of the problems associated with building any aberration-corrected electron microscope objective lens lies in the difficulty of obtaining a sufficiently short focal length. A number of systems have focal lengths in the 1cm. range, and these are more suitable for microprobe work. If the focal length can be made shor…
The image collecting system of the experimental high resolution electron microscope being developed in this laboratory must be compatible with the ultra-high vacuum (10 −10 Torr) maintained in the total column. The characteristics of an SEC porous KCl target used to record directly the primary high energy beam has bee…
Changes in dimensions which occur when fabric is released from loom are predicted. Analysis was not extended to finished fabrics, which is difficult. It is possible to predict the gray fabric dimensions of elastomeric fabrics, using relatively simple analytic methods.