FUNDAMENTAL TRANSITION IN THE ELECTRONIC NATURE OF SOLIDS
Striking evidence for a fundamental covalent-ionic transition in the electronic nature of solids is presented.
Materials Literature
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Tunneling-Assisted Nuclear Spin-Lattice Relaxation
The tunneling splitting of the torsional-oscillator ground state of a hindered methyl group is taken into account in calculating the temperature dependence of the proton spin-lattice relaxation time. Thermal vibrations cause spin-independent transitions leading to a fluctuation in the sign of the splitting parameter.…
Quasielastic Rayleigh Scattering in Nematic Liquid Crystals
Using a light-beat laser spectrometer, we observe the relaxation of the thermally excited fluctuations of anisotropy in the nematic phase of $p\ensuremath{-}\mathrm{azoxyanisole}$. We identify the two low-frequency purely dissipative modes recently predicted. A first study of the angular dependence of the width of the…
3,4-Dihydroxyproline: A New Amino Acid in Diatom Cell Walls
An analog of proline, 2, 3-cis-3, 4-trans-3, 4-dihydroxy-L-proline, was found in the cell walls of the eight species of diatoms studied and was isolated from the proteinaceous material of the wall of Navicula pelliculosa. The properties of this substance are described; its structure was confirmed by nuclear magnetic r…
Magnetism in Ni-Cu Alloys
On the assumption that in Ni-Cu alloys the spin moment on a Ni atom depends on the local atomic environment, it was possible to find moment values for the various atomic configurations so as to give average moments in reasonable quantitative agreement with the values measured in the ferromagnetic composition range. Th…
Band Shape and Phonon Broadening ofUBands in Alkali Halides
The remarkable similarity of the $U$ band originating from the first electronic transition of the ${\mathrm{H}}^{\ensuremath{-}}$ or ${\mathrm{D}}^{\ensuremath{-}}$ centers in an alkali halide to the $F$ band in the corresponding alkali halide is pointed out. The band shape and phonon broadening of $U$ bands in alkali…
Carrier-Concentration Dependence of Electron-Phonon Scattering in Te-Doped GaSb at Low Temperature
The thermal conductivity $K$ between 5 and 100\ifmmode^\circ\else\textdegree\fi{}K was measured on Te-doped samples with excess donor concentrations $n$ ranging between \ensuremath{\sim}${10}^{17}$ and 2\ifmmode\times\else\texttimes\fi{}${10}^{18}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. At temperatures below that of the p…
Resistivity Studies of Single-Crystal and Polycrystal Films of Aluminum
The resistivities of condensed polycrystal and single-crystal aluminum films have been measured as a function of thickness (1600-36000 \AA{}) and temperature (4.2-300\ifmmode^\circ\else\textdegree\fi{}K). Both the temperature-independent residual resistivity and the temperature-dependent resistivity increase with decr…
High-pressure scandium oxide and its place in the molar volume relationships of dense structures ofM2X3andABX3type
Sc2O3 has been transformed at 1000°C and 130 kb from the relatively open C-rare-earth structure type to the monoclinic B-rare-earth form with unit cell dimensions α = 13.173 A, b = 3.194 A, c = 7.976 A, and β = 100.40°. The calculated density, 4.16 g/cm3, represents an increase of 8.3% over the density of C-type Sc2O3…
Lattice Dynamics of Potassium Chloride
Phonon dispersion curves along the $[00\ensuremath{\zeta}]$, $[0\ensuremath{\zeta}1]$, $[0\ensuremath{\zeta}\ensuremath{\zeta}]$, and $[\ensuremath{\zeta}\ensuremath{\zeta}\ensuremath{\zeta}]$ directions in KCl at 115\ifmmode^\circ\else\textdegree\fi{}K have been measured by inelastic scattering of slow neutrons using…
Molecular Charge Distributions and Chemical Binding. IV. The Second-Row Diatomic Hydrides AH
An interpretation of the binding in the second-row diatomic hydrides NaH, MgH, AlH, SiH, PH, SH, and HCl is presented based on the molecular charge distributions and the forces exerted on the nuclei. The total density distributions are discussed in relation to “molecular” size and the arbitrary partitioning of the tot…
Infrared spectroscopic studies of adsorption and catalysis. Part 3. Carboxylic acids and their derivatives adsorbed on silica
Infrared spectra in the region 4000–1300 cm −1 have been obtained of acetic acid, acetyl chloride, acetic anhydride, propionic acid, and propionyl chloride adsorbed on discs of pressed silica powder. In all cases the spectra showed the presence of both the simple hydrogen-bonded species[Formula: see text]where X = OH,…
Singularities in the X-Ray Absorption and Emission of Metals
It is shown that Nozières and de Dominicis's exact solution to Mahan's model x-ray problem may be obtained very simply using an equation-of-motion technique.Received 25 November 1968DOI:https://doi.org/10.1103/PhysRev.182.973©1969 American Physical Society
4f–5d Excitation Energy of Tb3+ in Solids
Excitation spectra of the D45 → 7F emission of Tb3+ were measured in Sc(or In) BO3, and Y (or Gd) BO3, Y3Ga5O12, Sc (or Y) PO4, and Sc2 (or Y2) O3 at room temperature. The 4f–5d excitation band is discriminated from the host lattice excitation band by inspecting the concentration dependences of the excitation spectra.…
Quantum and Other Oscillations of the Nuclear Spin-Lattice Relaxation Rate inn−InSb
Measurements of the nuclear spin-lattice relaxation rate $\frac{1}{{T}_{1}}$ for ${\mathrm{In}}^{115}$, ${\mathrm{Sb}}^{121}$, and ${\mathrm{Sb}}^{123}$ in $n$-type InSb at low temperatures (1.3-4.2\ifmmode^\circ\else\textdegree\fi{}K) are presented as a function of magnetic field $H$ and crystal orientation for sever…
Infrared Excitation Processes for the Visible Luminescence of Er 3 + , Ho 3 + , and Tm 3 + in Yb 3 + -Sensitized Rare-Earth Trifluorides
Infrared reflectance and excitation measurements, together with studies of the dependence of the luminescence on excitation intensity and sensitizer concentration, in the fluorides of La, Gd, and Y doped with ${\mathrm{Yb}}^{3+}$ and ${\mathrm{Er}}^{3+}$, ${\mathrm{Ho}}^{3+}$, or ${\mathrm{Tm}}^{3+}$ indicate that inf…
Electronic Properties of Two New Elemental Ferromagnets: fcc Pr and Nd
The fcc phases of Pr and Nd have been stabilized at room temperature and at liquid-helium temperatures and both prove to be ferromagnetic. The measured electronic properties of this new phase are discussed in the light of presently accepted phase diagrams. The existence of the fcc phase accounts for a variety of anoma…
Revised X-ray diffraction line intensities for silicon carbide polytypes
Revised intensity relationships for the three common silicon carbide polytypes (6H, 4H and 15R) are presented together with the details of a technique by which pure polytype samples may be prepared.
Oxidation and Adsorption of Hydrocarbons on Noble Metal Electrodes VI. A Discussion of the Mechanism of Saturated Hydrocarbon Oxidation on Platinum
The anodic oxidation of saturated hydrocarbons on Pt is discussed. Coulombic efficiency for CO 2 production is 100% even for complex fuels. The need to examine adsorption processes in mechanistic studies is emphasized. Such studies reveal three materials in the steady state: CH—β (polymeric), CH—α (alkyl radicals), an…
A STUDY OF THE EFFECTS OF TEMPERATURE AND OXYGEN CONTENT ON THE CORROSION OF SEVERAL METALS
The corrosion rates of stainless steels 304 and 316, mild steel, nickel, Monel, Inconel and brass were investigated by electrochemical polarization techniques in 5% aerated and deaerated HCl solutions.