Structure cristalline de Ga γ
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Phonon-Assisted Energy Transfer between Trivalent Rare Earth Ions
Nonresonant phonon-assisted energy transfer between trivalent rare earth ions is studied using Y 2 O 3 as the host crystal. The transfer probabilities are obtained from the analysis of the decay rates of donor luminescence for various combinations of donor and acceptor ions in which energy gap, i.e. mismatch of energy…
p−dHybridization of the Valence Bands of I-III-VI2Compounds
The valence bands of I-III-${\mathrm{VI}}_{2}$ compounds result from a hybridization of the noble-metal $d$ levels with $p$ levels on the other atoms. This results in large downshifts in the energy gaps relative to the binary analogs, and the absence of spin-orbit splitting in the uppermost valance bands of several su…
Lattice Dynamics of Pyrolytic Graphite
The frequencies of certain normal modes of vibration of the graphite lattice have been studied on samples of high-quality pyrolytic graphite by coherent, inelastic-neutron-scattering techniques. Some of the data are not compatible with certain restrictions imposed by the valence-bond model as presented by Young and Ko…
High-Resolution X-Ray Photoemission Spectrum of the Valence Bands of Gold
High-resolution gold-valence-band photoemission spectra were obtained by the use of monochromatized $\mathrm{Al} K\ensuremath{\alpha}$ radiation and a single-crystal specimen. After background and scattering corrections were made, the results were compared directly with broadened theoretical density-of-states function…
Graphitization of diamond at zero pressure and at a high pressure
Abstract Natural diamonds have been heated in the temperature range of 1850 to 2000 °C at zero pressure and the rates at which diamond transforms to graphite measured. For {111} and {110} surfaces activation energies of 253+18 and 174+12 kcal mol-1 (1159 + 75 and 728 + 50 kJ/mol) respectively have been obtained. Diamo…
The vibrational spectra and structures of rare earth oxides in the A modification
Crystallographic studies of La 2 O 3 and the oxides isostructural with it have failed to decide between noncentrosymmetric space group D 3 2 (P321) and the centrosymmetric space group D 3d 3 (P3m1) for their structure. The infrared and Raman spectra of La 2 O 3 and Nd 2 O 3 have been obtained and the absence of coinci…
Spectroscopy of rare earth oxide systems. I. Far infrared spectra of the rare earth sesquioxides, cerium dioxide and nonstoichiometric praseodymium and terbium oxides
The far infrared spectra of the rare earth sesquioxides, cerium dioxide, and nonstoichiometric praseodymium and terbium oxides have been observed over the range 10-250 cm -1 at liquid helium temperatures. Absorption due to the excitation of phonons and low-lying electronic states of the rare earth ions occur in this r…
Temperature Dependence of Flow Alignment in Nematic Liquid Crystals
The temperature dependence of the flow alignment angle has been measured in two nematic liquid crystals, ${p}^{\ensuremath{'}}$-methoxybenzylidene-$p\ensuremath{-}n$-butylaniline and $p\ensuremath{-}n$-hexyloxybenzylidene-${p}^{\ensuremath{'}}$-aminobenzonitrile. For both compounds this angle reaches a peak value at t…
Nonanaliticity of the Magnetization Curve: Application to the Measurement of Anisotropy in Polycrystalline Samples
We studied the second derivative of the magnetization with respect to the magnetic field, $\frac{{d}^{2}M}{d{H}^{2}}$, for polycrystalline materials having uniaxial anisotropy. Evidence is given of a singular point located at $H={H}_{A}$, the anisotropy field. The observed sharp peak is associated with the infinity at…
Crystal Structure of the Solid Electrolyte(C 5 H 5 NH) Ag 5 I 6 at -30°C
The crystal structure of pyridinium hexaiodopentaargentate, (C(5)H(5)NH) Ag(5)l(6), is unique among those of the halide and chalcogenide solid electrolytes in that face-sharing iodide octahedra as well as face-sharing tetrahedra and face-sharing between octahedra and tetrahedra provide the paths for silver ion transpo…
Polymers: Synthesis and Characterization of Extremely High-Molecular-Weight Polystyrene
Polystyrenes with molecular weights up to 44 x 10(6) grams per mole have been characterized by light-scattering and equilibrium ultracentrifugation methods. The Mark-Houwink equation, which relates the molecular weight and the intrinsic viscosity of flexible polymers, can be used only if the measurements are made in a…
High Temperature Oxidation of Silicon Carbide
Thermogravimetric measurements were made for the oxidation of hot pressed silicon carbide at an oxygen pressure of 150 torr and at temperatures from 1300C to 1600C. Oxidized samples were then analyzed using X-ray, metallograph, and electron probe techniques. The oxidation rate was found to increase with temperature. T…
A DC and second derivative Langmuir probe measuring system
A phase-sensitive detection system is described in detail for measuring electron-energy distributions using conventional Langmuir probes. A switching circuit is also discussed which enables the system to measure the DC characteristics. A typical result is presented and modifications are suggested to enable probe chara…
Behavior of Ruthenium in Glass
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBehavior of Ruthenium in GlassJ. MukerjiCite this: Ind. Eng. Chem. Prod. Res. Dev. 1972, 11, 2, 178–183Publication Date (Print):June 1, 1972Publication History Published online1 May 2002Published inissue 1 June 1972https://pubs.acs.org/doi/10.1021/i360042a010https://doi.org/…
A symmetrically moving theta - theta X ray diffraction goniometer
An X ray goniometer is described in which the principal characteristic is that the sample, placed in a horizontal plane, remains motionless, while the X ray tube and X ray counter move symmetrically. This apparatus is specially designed for use with a high temperature X ray diffraction furnace associated with other te…
Punched-Out Dislocation Rosettes in Low-Dislocation-Density Copper
Copper single crystals of extremely low dislocation density have been obtained through a thermal cyclic annealing. Ball indentation in the dislocation-free area of (111) surface produced large dislocation rosettes, each arm extending in the 〈110〉 cystallographic orientations consisted of a row of prismatic dislocation…
The application of the partial Patterson method and the thirteenfold hexagonal superstructure of Cu7As6Se13
Derivative structures based upon sphalerite or galena often exhibit hexagonal superstructures characteristic of a peculiar thirteenfold multiplicity. A synthetic semiconductor, Cu 7 As 6 Se 13 , is one of the examples. Crystals of Cu 7 As 6 Se 13 are rhombohedral with a = 8.71 Å, α = 105°41′. The space group is R 3. T…
Radiation damage in annealed type 304 stainless steel
The defect structures in irradiated type 304 stainless steel were characterized by transmission electron microscopy for irradiation temperatures between 370 and 840°C and for fluences ranging from 1018 to 1023 neutrons/cm2 (> 0.1 MeV). Below about 550°C the interstitial atoms produced by the irradiation precipitate as…
Corrosive Effects of Various Salt Mixtures Under Combustion Gas Atmospheres
Laboratory studies are discussed in which steels were exposed to synthetic flue-gas atmospheres at temperatures ranging from 316 to 538 C (600 to 1000 F) in the presence of various salt mixtures. It was shown that the addition of chloride salts to mixed sulfates greatly accelerated the corrosion, particularly at 538 C…