Materials Literature
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Abstract In magnetic fields up to 50 kOe and for photon energies greater than the band gaps for light polarized with E ⊥ c and E ‖ c oscillatory changes of reflectivity are observed on ZnO‐crystals at helium temperatures. The anisotropic reduced masses and hole masses and the energy gaps are deduced from the shift of…
Abstract Azo compounds are characterized by a low‐energy 1 (n,π * ) electronic state, which gives rise to a weak band at long wavelengths in the absorption spectrum. Coupling of this state with other low‐lying molecular states is responsible for the high intensity of the “azo band” compared to other forbidden transiti…
The addition of ${\mathrm{Ti}}^{3+}$ and ${\mathrm{Mg}}^{2+}$ to ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$ leads to the suppression of the antiferromagnetic insulating phase; whereas the addition of ${\mathrm{Ti}}^{4+}$, ${\mathrm{Zr}}^{4+}$, and ${\mathrm{Fe}}^{3+}$ results in a first-order transition from a metallic to a…
Extinction coefficients k(lambda) for water at 25 degrees C were determined through a broad spectral region by manually smoothing a point by point graph of k(lambda) vs wavelength lambda that was plotted for data obtained from a review of the scientific literature on the optical constants of water. Absorption bands re…
Recent re-evaluation of diffraction data from cubic spinel compounds has suggested that in many cases the crystal structure is properly referred to the noncentrosymmetrical space group F43m. This symmetry provides the possibility of antiferroelectric behaviour which may resolve previous theoretical difficulties concer…
There are fundamental differences in the behavior of alumina-supported samples of a platinum and a copper-chromium catalyst for oxidation of carbon monoxide in a simulated automotive exhaust stream. Ignoring such differences can result in inappropriate comparisons between oxidation catalysts for automotive application.
It is shown that the anomalous elastic behaviour of Invar alloys is due to the contribution f the exchange energy. Using a molecular field approximation the exchange contributions is given in terms of the first and second derivatives of the effectives fo the effective exchange integral J(r). These parameters are corre…
A new mechanism for sound absorption in disordered solids is proposed. The mechanism combines the following two effects: (i) A sound wave modulates the frequencies of the thermal phonons (phonons of frequency $\frac{\mathrm{kT}}{h}$). (ii) In a disordered solid, phonons are elastically scattered by the disorder. Becau…
Generalized x-ray scattering factors have been extended to include a 3d Slater-type atomic orbital. The new scattering functions include deformations that represent octapole and hexadecapole atomic charge distributions. These terms are suitable for charge density analysis of atoms with high site symmetry. For a reason…
Photoemission spectra for $\ensuremath{\hbar}\ensuremath{\omega}\ensuremath{\le}11.7$ eV were measured from thin CsI films at 77\ifmmode^\circ\else\textdegree\fi{}K. The distribution of emitted electrons is interpreted in terms of optical excitation from a valence band comprising three branches of Bloch bands derived…
We report measurements of the magnetic susceptibility, Knight shift, and nuclear spin-lattice relaxation rates in the pure compounds Au${\mathrm{Ga}}_{2}$ and Au${\mathrm{In}}_{2}$ and an alloy of nominal composition ${\mathrm{Au}}_{0.95}$${\mathrm{Pd}}_{0.05}$${\mathrm{Ga}}_{2}$. Measurements were made in both the so…
The kinetics of energy transfer from antimony sensitizer to manganese activator in fluorophosphate phosphors has been studied. The transfer mechanism is identified as an exchange interaction by a comparison of the manganese concentration dependence of experimental quantum yield and emission decay curves with theoretic…
A novel electro-optic effect has been observed in thin homeotropic nematic layers. Electrodes, such as a pair of parallel lines, are located on a planar surface in contact with the liquid. Deformation of the homeotropic ordering occurs when the applied field exceeds a threshold strength. Induced optical birefringence…
The qualitative features of the bulk and surface energy bands of ionic transition-metal perovskite crystals such as SrTi${\mathrm{O}}_{3}$, BaTi${\mathrm{O}}_{3}$, KTa${\mathrm{O}}_{3}$, and BaZr${\mathrm{O}}_{3}$ are discussed. The linear-combination-of-atom orbitals (LCAO) method is used in combination with a genera…
We consider classical transition-state theory of collinear atom-diatom reactions. There are (many) potential surfaces for which this theory is exact provided all trajectories with energy above some fixed value are disregarded; the energy cutoff of course depends on the surface. We develop a simple criterion for recogn…
The dielectric relaxation study of glass-forming liquids show the presence of two relaxation regions at temperatures above TQ. The low frequency relaxation is attributed to the cooperative rearrangement of molecules. The high frequency relaxation, which continues to exist in the glassy state, is suggested to arise fro…
The point-multipole model, together with the Sawatzky model for overlap effects, has been used to calculate the electric field gradient tensors at the two nonequivalent ferric sites in Ca 2 Fe 2 O 5 . Good agreement with Mossbauer results has been obtained if alpha D and alpha Q , which have been considered as variabl…
Normal incidence reflectivity spectra using polarized light have been measured with E perpendicular to c as well as E//c for the layer type crystals of transition metal dichalcogenides WS 2 , WSe 2 , alpha -MoTe 2 , NbS 2 and NbSe 2 at 78 K and 300 K. Reflectivity peaks observed in the spectra of two polarizations are…
The magnetization of single crystals of Eu, Sm, Nd, Pr, and Pr-Nd alloys has been measured in fields up to 37 T (370 kG). The results give new information on the magnetic properties of these metals. Of particular interest is a first-order transition from a nonmagnetic to a metamagnetic phase in double-hexagonal close-…
A method is described for the direct measurement of the shear-alignment angle in a nematic liquid crystal. Results of such measurements are reported for the nematic phases of three compounds: PAA ($p$, ${p}^{\ensuremath{'}}$-azoxydianisole), MBBA ($p$-methoxybenzylidene-${p}^{\ensuremath{'}}\ensuremath{-}n$-butylanili…