Structure of Silica Glass
From configurational entropy considerations, it is estimated that the grains in silica glass are far more likely to have a cristobalite structure than a pentagonal dodecahedral one.
Materials Literature
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The recombination of nitrogen atoms and the nitrogen afterglow
Abstract The recombination of nitrogen atoms has been studied photometrically in a fast flow system. The concentration of nitrogen atoms was determined by nitric oxide titration. The measured bimolecular rate constant has the form kB = A + B[M] for M = N2, Ar and He with a constant value of A. The surface process was…
Properties of the Group VI B Elements Under Pressure. III. Phase-Diagram Studies of Various Forms of Sulfur
The phase diagram of sulfur has been investigated up to 60 kbar by differential thermal conductivity analysis in piston-cylinder and tetrahedral devices. The data indicate that the melting curve of orthorhombic sulfur rises to a triple point between orthorhombic, fibrous, and liquid sulfur at 37 kbar and 410\ifmmode^\…
Effect of Hydrogen Bonding on the Electrical Conductivity of Organic Solids
The bulk electrical conductivities of a series of monocarboxylic and polycarboxylic aromatic acids and some derivatives of these acids have been measured in order to study the effect of hydrogen bonding on conductivity. Electrical measurements were made on carefully purified, polycrystalline samples, compressed to rem…
Effects of Crystal Surface on the Optical Absorption Edge of AgBr
The absorption edge (380-500 m\ensuremath{\mu}) of AgBr was investigated with fine-grain suspensions in water. When the small amount of Rayleigh scattering was subtracted, the absorption coefficient was calculated from the remaining specular density. Comparison of crystals of about 65 \AA{} radius with bulk material s…
ESR Study of Mn2+ in α- and β-Mg2P2O7
The electron spin resonance of magnesium pyrophosphate (Mg2P2O7) doped with 0.3% manganese pyrophosphate has been studied at room temperature and in the temperature range of 55° to 94°C using a microwave frequency of 35 Gc/sec. The parameters of the spin Hamiltonian and the orientation of the principal axes of the Mn2…
Mechanisms of Energy Transfer Involving Trivalent Eu and Nd
The mechanism of energy transfer between Eu and Nd and the migration of excitation between Eu ions in the Na0.5(Y, Eu, Nd)0.5Wo4 tungstates and (Y, Eu, Nd)2O3 sesquioxides are examined. Transfer from Eu to Nd appears to be predominately by dipole—dipole interactions. At high Eu concentrations energy may migrate betwee…
Some Properties of Defects Produced by Ionizing Radiation in KCl between 80 and 300°K
A number of experimental techniques have been combined to study radiation-induced defects that are complementary to $F$ centers. One series of experiments, in which the resistance to dislocation motion due to interstitial centers was monitored by means of flow-stress changes, indicated that the centers produced by irr…
Temperature Dependence of Short-Range Order inβ-Brass
Critical scattering of neutrons around the superlattice reflections (1, 0, 0) and (1, 1, 1) from a single crystal of $\ensuremath{\beta}$-brass has been measured at temperatures from 2 to 25\ifmmode^\circ\else\textdegree\fi{}C above the transition temperature. The temperature dependence of the critical peak intensity,…
Lattice Dynamics of Sodium Fluoride
Phonons in sodium fluoride have been studied at room temperature using inelastic neutron scattering techniques. Consistent results were obtained using a cold neutron time-of-flight apparatus and a triple-axis spectrometer. The time-of-flight results were interpolated on to symmetry directions from the observed scatter…
Spectrum of Gaseous UCl4
The spectra between 4000 and 23 000 cm−1 of gaseous UCl4 have been obtained for the temperature range 950° to 1250°K. These spectra have been compared with those of single-crystal UCl4 at 77°K and room temperature. Spectra of solid UCl4 were obtained over the temperature range 300° to 827°K in order to compare with th…
Resistance Anomaly and Negative Magnetoresistance inn-Type InSb at Very Low Temperatures
The electrical resistivity and the magnetoresistance in $n$-type InSb containing more than 1.8\ifmmode\times\else\texttimes\fi{}${10}^{14}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ carriers have been measured from 4.2 to 0.1\ifmmode^\circ\else\textdegree\fi{}K. The resistivity increases logarithmically as the temperature is…
Exciton Structure and Magneto-Optical Effects in ZnS
The exciton structure in hexagonal ZnS has been studied in transmission and interpreted in terms of an effective-mass formalism. The ${n}_{1}=1,2,3,4,\mathrm{and}5$ states of the first (${\ensuremath{\Gamma}}_{7}\ensuremath{-}{\ensuremath{\Gamma}}_{9}$) series, and the ${n}_{2}=1,2,\mathrm{and}3$ states of the second…
Excitons in Degenerate Semiconductors
The band-to-band optical absorption is calculated for a direct-band-gap semiconductor that has one band degenerate $n$ or $p$ type. The degenerate band is treated as a high-density Fermi gas. It is shown that exciton states, arising from the electron-hole Coulomb attraction, still affect the optical absorption. The ca…
Self-Consistent Energy Bands and Cohesive Energy of Potassium Chloride
The valence and conduction bands of potassium chloride were determined by the augmented-plane-wave method from a potential of a more general functional form than that usually assumed in this method. With a few iterations of the band calculation within the Hartree-Fock-Slater (HFS) approximation, a good degree of self-…
Polycondensation‐addition. IV. Polysulfonamide‐ureas from isocyanatobenzenesulfonyl chlorides and diamines
Abstract p ‐Isocyanatobenzenesulfonyl chloride (I) and m ‐isocyanatobenzenesulfonyl chloride (II) were prepared by treating the corresponding aminobenzenesulfonic acids with phosgene and phosphorous pentachloride in dioxane. Tha compounds I and II were subjected to polycondensation‐addition with several diamines to ob…
Biotite Flakes: Alteration by Chemical and Biological Treatment
Biotite alteration under acid conditions proceeds differently from the generally accepted pathway of transformation to vermiculite in which hydrated cations cause interlayer expansion, resulting in a dark-colored peripheral band on mica particles. Acid solutions of synthetic or biologic origin remove octahedral ions,…
Single-Ion Magnetostriction in the Iron Group Monoxides from the Strain Dependence of Electron-Paramagnetic-Resonance Spectra
The single-ion contribution to magnetostriction in the transition metal monoxides NiO, MnO, FeO, and CoO is calculated on a very simple model and found to account for substantially all the observed magnetostriction. Exchange is included in a molecular-field approximation, and the single-ion magnetoelastic parameters $…
Energy Transfer in Ruby
The transfer of energy from single chromium ions to closely coupled pairs of chromium ions in ruby has been investigated. Ruby samples whose concentrations ranged from 0.003 to 1.0% ${\mathrm{Cr}}_{2}$${\mathrm{O}}_{3}$ were prepared and in each crystal the intensity of single-ion fluorescence and of pair fluorescence…
Single-Electron Capture and Loss Cross Sections for 2-50-keV Hydrogen Atoms Incident upon Hydrogen and the Inert Gases
The single-electron capture and loss cross sections ${\ensuremath{\sigma}}_{0,\ensuremath{-}1}$ and ${\ensuremath{\sigma}}_{01}$ for 2-50-keV hydrogen atoms incident upon hydrogen molecules and inert-gas atoms have been measured directly by observing the growth of the fast-collision products (i.e., the fast primary $\…