Materials Literature
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The crystal structure of α-Ga2O3, which is isostructural with α-corundum, has been refined from single-crystal x-ray diffraction data. The bond lengths have been determined to an accuracy of about 0.01 Å. The bond lengths in the GaO6 octahedron are 2.077 and 1.921 Å. The short Ga–O distance corresponds to the oxygens…
The magnetocrystalline anisotropy of several intermetallic phases of the type RCo5 (R = Y, Ce, Pr, Sm, Y-rich and Ce-rich mischmetals) has been investigated, and it is concluded that these alloys are promising candidates for fine-particle permanent magnets. They have extremely high uniaxial anisotropy (K = 5.4 to 7.7…
Share Icon Share Twitter Facebook Reddit LinkedIn Reprints and Permissions Cite Icon Cite Search Site Citation John R. Lamarsh, George I. Bell; Introduction to Nuclear Reactor Theory. Physics Today 1 March 1967; 20 (3): 110–111. https://doi.org/10.1063/1.3034192 Download citation file: Ris (Zotero) Reference Manager E…
This paper deals with various aspects of crystallization leading to oriented textures. In the first place it attempts to clarify the problem of melt-extruded polyethylene sheet, which leads to the more general problem of crystallization under stress. Lamellar crystal growth, normal to the stress direction nucleated al…
The long-range particles emitted during the spontaneous fission of $^{252}\mathrm{Cf}$ have been investigated, confirming the emission of $^{1}\mathrm{H}$, $^{2}\mathrm{H}$, $^{3}\mathrm{H}$, $^{3}\mathrm{He}$, $^{4}\mathrm{He}$, and $^{6}\mathrm{He}$. In addition it was found that $^{8}\mathrm{He}$, $^{6}\mathrm{Li}$…
A mass-spectrometric stirred-reactor technique was used to study the reaction of atomic oxygen with methane with low concentrations of molecular oxygen. An overall rate constant for oxygen-atom disappearance due to added methane was obtained for the temperature range 375 to 576°K. This rate constant was 4 × 10 14 exp…
The fluorescence and infrared absorption spectra of Sm3+ in single crystals of LaF3 have been observed and analyzed. Fluorescence was observed in the spectral range of 0.55 to 1.1 μm, and absorption in the region of 0.9 to 10 μm. The intermediate coupling free-ion energy levels of the 6FH multiplets have been calculat…
Ionization-efficiency measurements on species produced in the pyrolysis of B2H6 have led to A (B+), A (BH+), A (BH2+), A (BH3+), and A (B2H5+) from B2H6 and to A (B+), A (BH+), A (BH2+), and I (BH3) from BH3. These experimental results have permitted a rather complete development of the energetics of the BH3; B2H6 sys…
It is pointed out that the Raman spectrum of a color center gives significant information on the vibration spectrum associated with an electronic transition of the center itself. The formal theory of the first-order Raman scattering by substitutional defects in alkali halides is developed in detail. The coupling coeff…
An empirical rule for the type of luminescence (fluorescence only, fluorescence and phosphorescence, phosphorescence only) to be expected, which depends on the position of the respective ligands in the spectrochemical series, has been found for octahedral chromium (III) complexes. This correlation is discussed in term…
The energy levels of the configurations fd and f13d in cubic crystal fields have been calculated as a function of the f- and d-electron crystal-field parameters. The results are used to explain the spectrum of Yb++ in SrCl2. Both the calculated energies and calculated intensities agree well with experiment.
A study of the 2.3-eV absorption band in MgO crystals irradiated with electrons and gamma rays at 7, 80, and 305\ifmmode^\circ\else\textdegree\fi{}K has been made. This broad band, which has been designated as ${V}_{1}$, has a half-width of 0.96 eV at 5 and 78\ifmmode^\circ\else\textdegree\fi{}K and could be optically…
In all the infrared quantum counter systems reported to date, a single rare-earth ion dopant was used as the activator. This limits the optimum concentration to about 1%, since above this value nonradiative processes begin to dominate. In order to increase the number of ions which can absorb the infrared signal Yb3+ w…
The ESR spectra of Mn2+ ions have been observed in borate glasses of the composition (MnO)x(B2O3+0.04 K2O)1−x with x from 0.001 up to 0.030. For small concentrations of Mn2+ the central fine-structure transitions (M = +½↔—½), although broadened by the random orientation of small noncubic crystalline fields, show a wel…
Proustite (Ag3AsS3), a new acentric crystal for optical mixing, has been synthesized as large transparent single crystals. It is uniaxial, having point group symmetry 3m. Proustite transmits from 0.6 to 13 μm, and has a large negative birefringence (n0 − nE ∼ 0.2). Using second-harmonic generation from a 1.152-μm lase…
The results of an extensive study of the intrinsic viscosity [η] of a series of linear, homogeneous (anionically prepared) polystyrenes (1.9<10−4M<440) over a wide temperature interval (10°<T<110°C) in decalin and toluene are described. The data are discussed in relation to the interaction…
The sedimentation coefficient for the Kratky—Porod wormlike coil is calculated with the effects of excluded volume taken into account. The statistical length of native DNA is found to be 900 Å. The hydrodynamic diameter of the Watson—Crick helix is 26–27 Å. Sedimentation coefficients are calculated to decrease by abou…
Optical absorption and electron spin resonance (ESR) spectra of a chromium-doped phosphate glass have been studied as a function of Cr2O3 concentration. While the optical spectrum appears to be independent of chromium-ion density, the ESR spectrum exhibits a pronounced concentration dependence. The spectra have been a…
Volumetric and thermal measurements on its undercooled liquid indicate that o-terphenyl undergoes a glass transition in the vicinity of −30°C. This glass temperature is about 60°C higher than that predicted by correlations applicable to simple molecular glass formers. The viscosity of the undercooled liquid was measur…
Detailed studies have been made of the emission and associated excitation and absorption spectra of x-irradiated LiF. By studies of changes in the spectra during periods in the dark and during subsequent reirradiation, and by use of the Mollwo-Ivey relationships, it has been possible to identify optical bands associat…