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X-Ray Diffraction and Diffusion in Metal Film Layered Structures
Artificial layered structures that produce sharp diffraction of x rays are described. The structures were made by alternately evaporating 140 Pb and Mg layers onto a glass slide (d=27 Å). The diffracting efficiency of the layered structures is compared with other structures used in soft x-ray spectroscopy. The usefuln…
Melting temperature and change of lamellar thickness with time for bulk polyethylene
The melting temperature of linear polyethylene has been obtained as a function of the time and temperature of crystallization. Recrystallization was minimized by a special melting procedure. By interpreting the melting points as characteristic of a given lamellar thickness, it was found that the thickness of crystals…
Infrared Reflectance of Aluminum Evaporated in Ultra-High Vacuum
The specular reflectance of aluminum films evaporated in ultra-high vacuum has been measured with precision in the 0.3- to 32-μ wavelength region. The measured reflectance of these films, which is good to ±0.1%, is significantly higher than that of films prepared under the usual high-vacuum conditions. The reflectance…
Diffusionless Phase Transformations in Zirconia and Hafnia
A study, by high‐temperature diffractometry, of the monoclinic‐tetragonal phase changes in pure ZrO 2 and HfO 2 disclosed that the hysteresis loops associated with the transformations have similar shapes which are typical of many martensitic phase changes, but that the widths of the loops differ greatly for the two ma…
Ballistic Perforation Dynamics
Analytical equations of the types required to define ballistic perforation dynamics are developed. These equations concern both blunt and sharp-nosed fragments, perforating plates normally and at oblique impact angles. Residual velocities are defined in terms of magnitude and direction. Analytical models and confirmin…
Lattice Thermal Conductivity of Disordered Semiconductor Alloys at High Temperatures
The high-temperature thermal conductivity of a disordered semiconductor alloy is derived using the Klemens-Callaway theory. It is assumed that the reciprocal relaxation times depend on frequency $\ensuremath{\omega}$ as ${\ensuremath{\omega}}^{4}$ for strain and mass point defects and as ${\ensuremath{\omega}}^{2}$ fo…
Coulomb Self-Energy of Axial Figures
A new method of computing the Coulomb self-energy of uniform axial figures is developed. The energy is expressed as a sum of slice-slice interactions plus the self-energy of each slice. Analytical formulas are derived for these energies and are presented in numerical tables. The method is tested numerically by compari…
Thermoelectric Effect in Single-Crystal Cuprous Oxide at High Temperatures
The thermoelectric effect in single-crystal cuprous oxide, measured at temperatures of 500° to 1130°C and oxygen pressures P of 160 to 2×10—6 Torr, was found always to be positive, indicating that the material is a p-type semiconductor in these ranges of conditions. Plots of the thermoelectric power Q vs 1/T at differ…
Magnetic Structures of Chromium-ModifiedMn2Sb
The magnetic structures of tetragonal chromium-modified ${\mathrm{Mn}}_{2}$Sb have been determined by neutron-diffraction studies of single crystals. Compositions of ${\mathrm{Mn}}_{2\ensuremath{-}x}{\mathrm{Cr}}_{x}\mathrm{Sb}$ for $x$ from 0.023 to 0.10 were examined. Three magnetic structures have been observed, de…
Influence of Localized Modes on Thermal Conductivity
The curves of the thermal conductivity versus temperature of some insulating crystals (alkali halides) which are doped with certain impurity centers exhibit a distinct indentation. This suggests a relaxation time of some resonance nature, which is independent of the temperature for molecular impurity centers (KCl: KN$…
Chemiluminescent Reactions Involving Atomic Oxygen and Nitrogen
The emission excited in the association of atomic oxygen and nitrogen has been studied in a fast-flow low-pressure system by photoelectric and spectroscopic methods. The absolute rates of excitation of the products of these associative processes have been measured, and the effects of added quenching gases have been in…
Diffusion processes in lead-uranium systems
The ratio rλ of radiogenic daughter to residual parent (with decay constant λ) was investigated for a continuous diffusion model for a diffusion coefficient that is an arbitrary function of time. A solution for simultaneous diffusion of both parent and daughter is given in closed form. A theory is also developed that…
Phonon Scattering by Lattice Defects
The Green's-function matrix method first developed by I. M. Lifshitz is applied to the problem of the scattering of phonons by a localized perturbation in the lattice. The scattering can be described by a $t$ matrix that is localized to the same extent as the perturbation and has similar symmetry properties. The $t$ m…
Hysteresis in the Palladium—Hydrogen System
When hydrogen is dissolved in palladium, the α phase forms first; the β phase nucleates and grows in this. Because of the large volume change which accompanies the α-to-β transition, plastic deformation of the α phase occurs as it is stretched beyond its elastic limit. Hence, absorption is accompanied by growth of the…
X-Ray and Electrical Conductivity Study of the Fluorite Phase in the System ZrO2–CaO
In the ZrO2–CaO system cubic solid solutions of the fluorite-type structure are formed between 12 and 22 mole % CaO for specimens fired at 2000°C and subsequently quenched from 1400°C. The lattice parameter increased linearly from 5.125 to 5.144 Å with increasing CaO content. Results of x-ray diffraction intensity stu…
Phonon Scattering by Point Defects
Phonon scattering by point defects was studied by measuring the thermal conductivity of KCl containing known amounts of Kl, NaCl, and Ca${\mathrm{Cl}}_{2}$ in solid solution. By also measuring the conductivity in crystals in which the impurities were allowed to coagulate, it was possible to distinguish between the eff…
Crystal-Field Spectra of d3,7 Ions. III. Spectrum of Cr3+ in Various Octahedral Crystal Fields
The spectra of eight crystals containing trivalent chromium have been measured, and the energy levels fitted to a four-parameter crystal-field theory. The values of the parameters derived from the spectra are discussed, and some mechanisms responsible for absorption intensities are evaluated.
Thermal Decomposition of Rare Earth Metal Oxalates. II. Oxalates of Samarium, Europium, Gadolynium, Terbium and Dysprosium
Abstract Thermal decomposition of the hydrated oxalates of the above rare earth metals was carried out on a Stanton thermobalance. The oxalates after precipitation were dried at 110° C for six hours and then used for the decomposition studies. No indications of the formation of stable lower hydrates or of intermediate…
Luminescence of Pure and Cu-Doped Alkali Halide Single Crystals
In order to understand some x-ray excited emission bands in pure alkali halides, crystals were doped with the corresponding copper halides. It has been found that a band, which is also often present in "pure" or thermally treated alkali halides, is due to a Cu center. The excitation spectrum of the Cu impurity at room…