bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamical Behavior of Dislocations in the Primary Slip Systems of Body-Centered Cubic Crystals
Authors: Teutonico L. J.
Published: April 2005

The general analysis of uniformly moving dislocations in anisotropic media is applied to investigate the dynamical behavior of dislocations in the primary slip systems of body-centered cubic crystals. Both edge and screw dislocations on the {110}, {112}, and {123} slip planes are considered; in each case, the Burgers vector of the dislocation lies along a 〈111〉 direction. Numerical solutions are obtained for the force exerted by a uniformly moving dislocation on a parallel dislocation of similar type on the same slip plane. The bcc elements treated are niobium, molybdenum, vanadium, tungsten, tantalum, iron, potassium, sodium, and lithium. Calculated values of the limiting velocities both of edge and screw dislocations are presented, as well as the threshold velocities for the interaction of two edge or two screw dislocations. These calculations determine, for each slip system in each of the elements listed, the extent of the velocity range of anomalous behavior in which two like dislocations attract rather than repel each other.
Gas Bubbles in a Charged Liquid
Authors: Stuetzer Otmar M.
Published: April 2005

Gas bubbles in charged regions of a dielectric liquid move away from high fields. They do not acquire a net charge of their own, but are moved by electrical pressure gradients and polarization forces. The phenomenon is of interest for a variety of applications.
Diffraction of Fast Electrons After Single Plasmon Loss
Authors: Heidenreich R. D.
Published: April 2005

The diffraction of eigen-loss electrons is examined in some detail. It is shown that the collision zone with a crystal is sufficiently diffused that a significant fraction (10% at E = 105 V) of E1 = E−δE electrons are produced outside the crystal boundaries. These electrons behave like an incident beam of energy E1 and appear to be responsible for Watanabe's observations with an energy selecting electron microscope.
Prediction of Curie Temperatures in Ternary Fe-Co-Ni Alloys
Authors: Artley J. L. , Pilkington T. C. , Wooten F. T.
Published: April 2005

Empirical data concerning the Curie temperatures of binary Co-Ni, Fe-Ni, and Fe-Co alloys is used to predict the Curie temperature of ternary fcc Fe-Ni-Co alloys. The predicted values of the Curie temperature of the ternary alloys agree within 30° over the entire range of fcc structure with much better agreement over most of the range of concentrations. The model used to make this prediction is an extension of the approach introduced by Zener and developed by Carr.
Effect of Gas Flow on the Microwave Dielectric Breakdown of Oxygen
Authors: Skinner John G. , Brady James J.
Published: April 2005

Pulsed microwave power is used to produce breakdown in a constricted 3-cm waveguide containing oxygen gas in the pressure range from 15 to 25 mm Hg. The breakdown characteristics are studied as a function of the flow velocity of the gas. The power necessary to maintain the discharge after it has been initiated increases with flow velocity up to a critical velocity because the electron density at the constriction is reduced by the flow. Beyond the critical velocity the necessary power decreases with flow velocity. This latter phenomenon is believed to be due to ``back flow'' of the gas.
Diffusion Layer Ultrasonic Transducer
Authors: Foster N. F.
Published: April 2005

By diffusing copper into the surface of conductive cadmium sulfide single-crystal samples, thin piezo-electrically active layers have been formed. Such diffusion layers have been shown to act as ultrasonic transducers with operating frequencies well above 100 Mc. Short delay lines with less than 30 dB of insertion loss at 175 Mc have been made using such diffusion layer transducers.
Structures of Clean Surfaces of Germanium and Silicon. I
Authors: Lander J. J. , Morrison J.
Published: April 2005

Low-energy electron diffraction patterns obtained from Ge(100) and Ge(111) clean surfaces are described and analyzed. The Ge(100) surface structure is the same as that observed with Si (100) surfaces. Parameters for the atom sites are reported. Structural units for both Ge and Si (111) clean surfaces are strongly suggested by the data reported for these surfaces. They have an atom defect of about 25% in the top layer. A wide variety of such structures can be proposed and three of them appear to have been observed. The importance of long-range order on the density of semiconductor chemical ``surface states'' is emphasized and surface bands are discussed.
Resonance Phenomena in a Gaseous Discharge in a Strong Magnetic Field
Authors: Beeken Basil , Goldman Robert , Oster Ludwig
Published: April 2005

The rf spectrum of a gaseous discharge in a strong magnetic field is measured with the aid of a fixed frequency receiver by sweeping the magnetic field by approximately two percent. Source of radiation and receiving equipment are described. The following results were obtained: (1) A series of emission lines around the cyclotron frequency. (2) An emission at a frequency which increases with increasing magnetic field strength and decreases with increasing external voltage. (3) A strong resonance when both frequencies coincide: the intensity increases by a factor of 100 and more.

The frequency spectrum is discussed in terms of a simple theory, which accounts for local space-charge fields. Their spatial distribution is inferred from the frequency behavior of the emission lines. Finally, a mechanism is suggested which classifies the resonance effect as an energy transfer from a longitudinal plasma mode into e.m. radiation.
Parametric Coupling of the Magnetization and Strain in a Ferrimagnet. I. Parametric Excitation of Magnetostatic and Elastic Modes
Authors: Comstock R. L. , Auld B. A.
Published: April 2005

A theoretical treatment is presented of the parametric coupling between the magnetization and elastic strain in a ferrimagnet produced by magnetic pumping. In this paper the parametric coupling between resonant magnetostatic and elastic modes is discussed. The case of a disk vibrating in a longitudinal mode coupled to the uniform precession mode is discussed in detail. The oscillation threshold for this simple geometry is calculated and shows clearly the dependence of the threshold on the properties of the modes and the magnetoelastic coupling coefficients. It has been found that the threshold calculated for the disk geometry agrees to within an order of magnitude with measurements of the threshold for this effect using single-crystal YIG spheres.
Parametric Coupling of the Magnetization and Strain in a Ferrimagnet. II. Parametric Excitation of Magnetic and Elastic Plane Waves
Authors: Comstock R. L.
Published: April 2005

The parametric coupling between traveling electromagnetic and elastic waves in a ferrimagnet supplied by magnetic pumping is theoretically investigated. The pumping threshold is calculated for steady-state wave propagation in the presence of loss for plane electromagnetic and longitudinal elastic waves in an infinite ferrite medium. This threshold is compared to the threshold for second-order spin-wave instabilities and it is found that these spin wave processes should not prevent the magnetoelastic process from occurring.

It is shown that this traveling wave system may be useful for amplifying electromagnetic or elastic waves.
Use of Electron Paramagnetic Resonance for the Exploration of Radio Frequency Field Patterns in Microwave Structures
Authors: Robinson Laurence C.
Published: April 2005

It is proposed that a small sample of a dielectric material doped with paramagnetic ions be used as a probe to explore rf magnetic fields in microwave structures. The bandwidth of the electron paramagnetic resonance line under conditions of saturation is a measure of the microwave magnetic-field strength.
Defects Introduced in Neutron-Irradiated Esaki Diodes
Authors: Pierce C. B. , Kantz A. D.
Published: April 2005

Ge and Si Esaki diodes have been subjected to reactor neutron irradiation at 90°K. Ge diodes show no structure in the radiation-induced excess current during irradiation but develop a hump at 0.30-V bias upon anneal to above 250°K, when observed at 77°K. In accordance with a model interpreting hump structure as being due to direct tunneling involving narrow defect levels deep in the forbidden band, the lack of structure in the ``as-irradiated'' Ge diodes is interpreted as being associated with a continuum of levels arising from large clusters of defects. The growth of the hump (corresponding to an energy level at Ev+0.31 eV) during anneal is associated with the breakup of large clusters into smaller defects, giving rise to a discrete energy level. Most of the continuum of added excess current (at bias values away from the hump), as well as the hump current, anneals out below 450°K. Anneal of the continuum agrees closely with recovery of length change in deuteron bombarded Ge which has also been interpreted as being due to the breakup of clustered defects. Si diodes show hump structure at 0.3 and 0.6 V after irradiation and anneal to 195°K, upon observation at 77°K, and at 0.9 V in the course of further anneal. These humps are associated with energy levels at approximately Ev+0.35, Ec −0.45, and Ec −0.15 eV, respectively. Hump structure and annealing behavior are quite similar to that observed after low temperature electron irradiation, except that the structure is somewhat less distinct after neutron bombardment. According to the interpretation given the Ge results, this implies that large clustered defects in neutron irradiated Si must have already partially annealed below 195°K or are relatively less numerous or less evident in their effects than in Ge.
Ultrasonic Attenuation in Single-Crystal Cadmium
Authors: Abowitz G.
Published: April 2005

The attenuation of compressional and shear waves has been measured in cadmium single crystals at 300°K over the frequency range from 5 Mc/sec to approximately 60 Mc/sec. Above 20 Mc/sec attenuation follows the power law α=Cfn, where α is the attenuation, f is the frequency, n is a constant between one and two, and C a second constant. The results, however, cannot be accounted for by known thermoelastic losses in the case of compressional waves and dislocation damping in the case of shear waves. The phase velocities of all five modes of propagation were determined at 300°K and used to compute the adiabatic elastic constants C11, C12, C33, and C44.
Viscoelasticity of Polymer Solutions at High Pressures and Ultrasonic Frequencies
Authors: Philippoff W.
Published: April 2005

The torsionally vibrating quartz crystal has been used to measure the complex viscosity of polymer oil systems under different temperatures and hydrostatic pressures. An extension of the method of reduced variables has been proposed to take into account the changes in viscosity due to pressure. The application of this method to 4 polymer solutions has proven its validity. The use of the quartz crystal allows conditions of high rates of shear and hydrostatic pressures to be accessible without undue heating.
Investigation of the Oxidation of Copper by Electron Diffraction
Authors: Yoda Eiji , Siegel Benjamin M.
Published: April 2005

The manner in which the oxide phase nucleates and grows on copper single crystals exposed to oxygen at a pressure of 1×10−2 mm of Hg and at temperatures between 300° and 400°C has been investigated by reflection electron diffraction and electron microscopy. Widely spaced oxide crystallites oriented with the [110] direction parallel to the [110] direction of the copper form and continue to grow at these temperatures even after the removal of the oxygen atmosphere. No polycrystalline phase was observed to form under these conditions, but the intensities of the copper spot pattern and Kikuchi lines decreased during exposure to oxygen and partially recovers in intensity during subsequent heat treatment.
A Note on Domain Conversions of BaTiO3
Authors: Fang P. H. , Brower W. S.
Published: April 2005

Some peculiar properties of single-crystal BaTiO3 that has been converted into a domain are discussed. The a domain shows a time instability. An intrusion of c domains is observed by x-ray diffraction and polarizing microscope with a monochromatic light source.
Proposal for Beating Two Optical Masers
Authors: Mahan G. D. , Hopfield J. J.
Published: April 2005

An experimental arrangement is proposed with which two optical masers may be made to beat to produce a far-infrared source. The beating process occurs in a semiconductor which lacks inversion symmetry, allowing the third-order process. By selecting a semiconductor with an appropriate energy gap, the energy denominators in the matrix element may be made small, enhancing the infrared intensity. Using the exciton states as the virtual intermediate states, the power output is calculated in the effective-mass approximation. For beating a ruby maser at T=−180°C (6934 Å) with one at T=20°C (6943 Å), a CdSe sample at 4.2°K is proposed because its exciton energies are just higher than the maser energies. For input power of 10 kW for each energy, a 19-cm−1 infrared beam of over a watt is expected. The competing process of two-photon absorption heats the sample to approximately 65°K during a pulse, but this effect is not disastrous.
Rate Analysis of Multiple-Step Excitation in Mercury Vapor
Authors: Zito Ralph
Published: April 2005

In the course of studying a multiple-step excitation process in mercury vapor for the possible application to a three-dimensional display of data, an analysis of the fluorescence mechanism was made. A dual optical-excitation process is employed by which mercury vapor is caused to radiate at a localized region in space. The radiation is in the ultraviolet and visible portions of the spectrum. A partial analysis and pertinent literature review is presented here for the resonance absorption and reradiation of light energy by mercury vapor at room temperature.
DC Magnetic Moment Induced by a Strong RF Magnetic Field Applied Parallel to the DC Field
Authors: Kohane T. , Schlömann E.
Published: April 2005

It is shown that the parametric excitation of spin waves by means of a microwave magnetic field applied parallel to the dc field is accompanied by a decrease of the dc magnetic moment. In the region immediately above the instability threshold, the magnitude of the dc moment is in good agreement with the theoretical predictions. The results indicate that, immediately above the threshold, spin-wave excitation is confined to a fairly narrow region in wavenumber space.
An Electrodynamic Foucault Pendulum
Authors: Shapiro A. R. , Watson W. K. R.
Published: April 2005

The trajectories of a single charged particle trapped in an electrodynamic, quadrupolar-containment device are studied in a uniformly rotating coordinate system, in an attempt to simulate the behavior of a Foucault pendulum.
Some Dielectric and Optical Properties of KD2PO4
Authors: Sliker T. R. , Burlage S. R.
Published: April 2005

The Curie point of KD2PO4 is found to be 222°±1°K, which is 9°K higher than previously reported. It is believed that the higher value is due to more complete deuteration. Other physical properties (at room temperature unless otherwise noted) are as follows: dielectric constant from 208° to 300°K; contour shearmode resonance-frequency constant from 270° to 320°K; elastic compliance, s66E=165±3×10−12 m2/N; piezoelectric constant, d36=58±2×10−12 C/N; electromechanical coupling, k36=0.22±0.01; optical absorption between 200 and 2600 mμ for both KD2PO4 and KH2PO4 (the transmission of a 7.4-mm-thick KD2PO4 sample was greater than 50 percent from 400 to 1850 mμ); zero stress electro-optic coefficient, r63=26.4±0.7×10−12 m/V; lattice constants for both KD2PO4 and KH2PO4; and spontaneous polarization and coercive field from 150° to 222°K.
Electrical and Optical Properties of Crystalline Black Phosphorus
Authors: Warschauer Douglas
Published: April 2005

Polycrystalline black phosphorus has been produced by the Bridgman method of combined temperature and pressure and found to be p type with room-temperature resistivity around one Ω-cm, in agreement with the observations of previous workers. From 300° to 700°K, the resistivity can be fitted by an expression ρav=4.6×10−3 exp(0.35/2kT) Ω-cm, and the Hall data by (ReT32)−1 = constant exp(−0.34/2kT). The product Rσ can be represented in this temperature range by (Rσ)av = 9×105T−1.4 cm2/V-sec. The deviation from this law toward lower mobility observed by Keyes from 250° to 350°K does not occur in these samples. The resistivity continues to rise even near liquid-helium temperature, and maxima in the Hall coefficient occur between 24° and 30°K. The low-temperature Rσ products also exhibit maxima, and the magnitude of this product is small near liquid-helium temperature. Although these characteristics are consistent with two-band conduction, the relative appearance of the two sets of maxima is not consistent with a prediction of the simplest two-band theory. An optical absorption edge is found in the 2- to 6-μ region and its temperature dependence yields dW/dT = 2.8×10−4 eV/deg. A sharp absorption peak observed near 21 μ moves to longer wavelengths with increasing temperature at a rate dW/dT = −2×10−6 eV/deg. At helium temperature the ac photoconductive response is substantially flat from one to 20 μ. At nitrogen temperature the response is peaked between 4 and 5 μ, while at room temperature a peak is observed in the same wave-length range but the sensitivity is considerably less.
Microwave Measurements of Moving Striations in a DC Glow Discharge
Authors: Sodomsky K. F.
Published: April 2005

The effects of moving striations in a glow discharge on microwave standing-wave patterns in a waveguide containing the discharge were measured. The data yielded estimates of the longitudinal variation of electron density along a striation which were compared to measured light intensity variations. It was found that there were large variations in both electron density and brightness with the brightness maximum just to the cathode side of the electron density maximum. These results are compared to the results of other investigations and some points of disagreement noted.
Self-Pinch Instabilities in Solid Sodium
Authors: Henson R. M. , Eisner M.
Published: April 2005

Taylor-type instabilities have been observed using sodium as a magnetohydrodynamic model of plasma. The wavelengths were found to be in fair agreement with the theory of Kruskal and Schwarzschild.
Heat-Wave Methods for the Measurement of Thermal Diffusivity
Authors: Cutler M. , Cheney G. T.
Published: April 2005

A simple method for measuring thermal diffusivity is considered. It consists in suddenly heating one end of a sample and measuring the time it takes for a heat wave to arrive at the other end. This paper considers the application of this method for two kinds of boundary conditions relating to the heat input. These conditions correspond to step-function heating (a) by radiation and (b) by a good contact to a constant-temperature heat source, such as liquid metal.

In addition to consideration of the effects on the analytic solution due to radiation heat loss, other factors which affect the accuracy and sensitivity of the technique are discussed. The heat-wave method is related to many other techniques for measuring thermal diffusivity, ranging from Angstrom's original method to several pulse heating techniques which have been described recently. The interrelationships between these different techniques are discussed.
Theory of Scattering for Diffusion-Controlled Phase Separations
Authors: Goldstein Martin
Published: April 2005

A quantitative theory of the scattering from systems in which a precipitating phase is undergoing diffusion-controlled growth is worked out by means of a Fourier transform method, and is applied to experimental data on light scattering from phase-separated glasses. The theory predicts an initial inverse eighth-power dependence of turbidity on wavelength, a great excess of backward scattering over forward scattering, and under certain conditions a minimum in the plot of intensity against scattering angle, all of which are in agreement with observation.
Surface Lines on Soda-Lime Glass Slides
Authors: Stilwell G. R. , Dove D. B.
Published: April 2005

It has been found that a remarkable line structure may be developed on the surface of soda-lime glass slides by treatment in a hot detergent solution (2% Alconox). The lines are produced by an etching process which exposes ridges or cords of less soluble material that have been introduced into the surface layer by the manufacturing procedure of drawing the glass through an orifice (Fourcault process). Details are given of etch rates, size and distribution of the ridges, and of the effect of annealing treatments.

The possibility of the inadvertent production of an anisotropic surface structure is of some importance since soda-lime microscope slides are frequently used as substrates for vapor deposition processes. Preliminary experiments to examine the effect of the line structure on vapor deposited Permalloy films are discussed.
Dislocation-Impurity Interactions and Strain Aging in AgCl
Authors: Kabler M. N. , Miller M. G. , Slifkin L. M.
Published: April 2005

Strain aging in silver chloride single crystals containing a few parts in 105 polyvalent metal impurity has been studied over the temperature range −12° to 51°C. At room temperature, the aging process requires of the order of half an hour to go to completion. The measured activation energy for the aging rate is 0.46±0.06 eV. The maximum stress increment due to aging decreases with increasing temperature with an effective activation energy of 0.1 eV. On the basis of the kinetics of the process, it is demonstrated that the dislocation pinning giving rise to strain aging is due to the migration to the dislocations of the impurity ions themselves rather than the vacancies they introduce. Sharp upper yield points have been observed; they are discussed in terms of current concepts of dislocation multiplication and unpinning.
Resistance of Elastically Deformed Shallow p-n Junctions. II
Authors: Rindner W. , Braun I.
Published: April 2005

An effect of large anisotropic stresses to lower the resistance of shallow p-n junctions reversibly by several orders of magnitude has been extensively investigated. Even though large stresses have been used it was found that their anisotropies were of greater significance than their magnitudes. The effect was found to increase strongly with decreasing junction depth. Of the crystal planes studied in Ge, the effect was largest with junctions lying in the (111) planes and smallest with junctions in the (100) planes. In both Ge and Si the effect increased with increasing temperatures. Stress-frequency response was observed from dc to 100 kc. The same effect in transitors caused reversible changes in collector current by factors up to nearly 1000 for a constant emitter current. Stress and strain analyses indicated large energy-gap changes with pronounced extrema. At the present stage, none of the known stress effects on the resistance of homogeneous semiconductors or junctions could be satisfactorily correlated with the magnitude and the various manifestations of the present stress effect. A tentative model is considered, based on a stress controlled generation-recombination rate of carriers due to generation and elastic distortion of dislocations.
Single- and Double-Deformation Faults in Face-Centered Cubic Crystals
Authors: Warren B. E.
Published: April 2005

The diffraction effects of a double-deformation fault (extrinsic fault) are readily derived for small faulting probabilities by using a faulted sequence with a layer added and subtracted. Let α′ and α″ be the probabilities for single- and double-deformation faults. If both types of faulting are present, with α′ and α″ both small and independent, the peak broadening depends upon α′+α″, the peak shift depends upon α′−α″, and there is a peak asymmetry proportional to α″ which is similar to that produced by twin faulting.
Recombination and Mobility of Nuclear Radiation Induced Ionization in Liquid Hydrogen
Authors: Zessoules N. , Brinkerhoff J. , Thomas A.
Published: April 2005

The development of apparatus and procedures to obtain experimental data on ionization in a flowing stream of liquid hydrogen is presented. For uniformly mixed positive and negative ions, the rate of recombination is actually seen to be proportional to the square of the ion density, and the velocity of the ions is seen to be proportional to the magnitude of the applied field. The values of the recombination coefficient α and ionic mobility μ represent reasonable extrapolations of the values for atmospheric pressure gases, assuming a simple inverse dependence on density. The relationship of the two values also satisfies Langevin's criterion α≤8πeμ, in that the result obtained is α≈4πeμ, which is also the relation observed for atmospheric pressure gases. In addition, the fraction ε of the volumetric ionization rate which is available for recombination and production of currents is computed. The values of α, μ, and ε obtained are: α=1.12×10−8 cm3/ion pairs·sec, μ=8.45×10−3 cm3/V·sec, and ε=1.7×10−4.
Evolution of the Giant Pulse in a Laser
Authors: Wagner William G. , Lengyel Bela A.
Published: April 2005

The differential equations governing inversion and photon density in a laser are solved for giant pulse operation. The simplifying assumptions which permit solution involve homogeneous excitation of the laser and the neglecting of changes produced by pumping and fluorescence during the formation of the giant pulse. Energy, peak output power, pulse delay, and pulse width are calculated.
Relation of Rate and Duration of Evaporation to Background Pressure for the Deposition of Thin Films in Vacuum
Authors: Schwarz Helmut
Published: April 2005

Measurements of the electrical resistivity of chromium films (50 to 10 000 Å thick) deposited on Pyrex glass at various evaporation rates and background pressures (achieved with an ``electronic'' ion pump) are reported and plotted against the ratio of the arrival rate of molecules from the background gas to that of the vapor atoms at the substrate surface. These points show a large degree of scatter. But, if one plots the resistivity versus the product, background pressure, and duration of evaporation, which determines the total amount of residual gas arriving at the substrate, the result is a smooth curve which can be used to derive an empirical relationship between the pertinent parameters.
Switch-On Transients in p-n Junctions
Authors: Chang Y. F.
Published: April 2005

The transient response of p-n junctions when switched-on in the forward direction is analyzed in this paper. This transient is complimentary to that analyzed by Lax and Neustadter and by Gossick. When a p-n junction is switched on in the forward direction, nonideal switching characteristics are produced—the transient voltage across the device has finite rise time and decay time. This transient appears capacitive at small signals and inductive at large signals. These nonideal switching characteristics have been explained by the present analysis. Excellent agreement is obtained between theory and experiments for an example diode (1N91). The basis for this analysis is the inclusion of the voltage drop across the bulk material of the base region. In other words, the effects of conductivity modulation are analyzed and added to the junction voltage. It is found that nearly ideal switching characteristics can be obtained if the applied signal is approximately I0, which is given by the intersection of the quiescent base-resistance Rir on the diode dc characteristic.
Interdependence of Plasma Frequency and Surface Diffusivity from Electromagnetic Scattering Analyses
Authors: Wyatt Philip J.
Published: April 2005

A thorough examination of the far field electromagnetic scattering characteristics of a spherically symmetric plasma indicates quite clearly the possibility of obtaining ambiguous results from microwave measurements. This ambiquity arises because of an interdependence of the average plasma frequency and the surface diffusivity. In order to differentiate between these two physical causes, an analysis of the differential scattered intensity is undertaken. This latter quantity is found to be extremely sensitive to variations in plasma frequency and surface diffusivity and may be used to separate the effects of each.
Electrolytic Conduction in Calcium-Doped Solid Cerium Oxide
Authors: Kevane C. J. , Holverson E. L. , Watson Robert D.
Published: April 2005

At 460°C the passage of direct current through ceramic pellets of cerium dioxide containing one weight percent calcium oxide caused distinct volume discolorations to appear. The current at constant applied bias increased gradually from its initial value during the formation of the discolored regions, finally reaching a new, stable, higher level if sufficient time elapsed. In the latter case, both anode and cathode surfaces were discolored and the discoloration extended completely through the body of a pellet. When insufficient time was allowed for the current to reach a new, stable level, only the cathode surface was discolored and the discoloration extended only part way through the material. The discolorations could always be removed by heating the pellets for one hour in air at 600°C and the entire process could be repeated many times. These effects are interpreted to indicate that a significant fraction of the current in this material at this temperature is carried by oxygen ions which move to the anode where they are ``plated-out'' leaving reduced, discolored material.
Constitutive Equations for a Plasma-Like Medium
Authors: Neufeld Jacob
Published: April 2005

A general formulation is obtained representing the constitutive equations for a plasma-like medium. These equations are of the type P=αeeE+αemB; M=αmeE+αmmB, where E is the electric intensity, B is the magnetic induction, P and M represent the electric and magnetic polarizations, respectively, and αee, αem, αme, and αmm are appropriate macroscopic parameters characterizing the medium. These equations differ from the constitutive equations for a molecular medium since in the latter case one has P=χeE and M=ξmB, where χe is the electric susceptibility and ξm is the ``proper magnetic susceptibility.'' A formulation is given for the constitutive parameters for two particular cases: (a) when the plasma-like medium is represented by a charge-equilibrated uniform electron beam of infinite width and (b) when the plasma-like medium is represented by a charge-equilibrated electron gas characterized by an isotropic velocity distribution f(v).
Spectral Characteristics of GaAs Lasers Operating in ``Fabry-Perot'' Modes
Authors: Sorokin P. P. , Axe J. D. , Lankard J. R.
Published: April 2005

High resolution measurements of the spectral output of GaAs injection lasers are made. It is found that the main features can be understood in terms of conventional line-narrowing theories. Additional oscillations are observed in modes other than the lowest loss ones.
Wave Propagation in an Active Dielectric Slab
Authors: Hall R. N. , Olechna D. J.
Published: April 2005

An analysis is made of the propagation of electromagnetic radiation in a dielectric slab having a negative electrical conductivity, sandwiched between semiinfinite regions having the same dielectric constant but positive conductivities. The threshold conditions corresponding to zero attenuation for waves propagating in the plane of the slab are determined. For slab thicknesses that are small, compared with a wavelength, the most easily excited wave is polarized with its electric vector perpendicular to the plane of the slab but for thicker active regions the threshold is independent of polarization. These results are compared with observations of stimulated emission in p-n junction lasers.
Theory of Space-Charge-Limited Emission in High-Pressure Gas Diodes
Authors: Forman R.
Published: April 2005

A theory for space-charge-limited current in gas-filled thermionic diodes has been developed which takes into consideration the variation of mean free path with electronic energy. The theory is applied to experimental data obtained on gas-filled diodes containing helium, neon, argon, and krypton, in the pressure range 1–700 Torr, and is shown to be in reasonable agreement with experiment.
Gain Saturation and Output Power of Optical Masers
Authors: Rigrod W. W.
Published: April 2005

The nonlinear gain characteristics of optical maser amplifiers at high beam intensities, and the optimum cavity coupling of maser oscillators for maximum output power, are computed for maser media with homogeneous and inhomogeneous line broadening. An approximate expression is derived for the power output of a gas maser oscillating simultaneously at many longitudinal cavity resonances, based on the assumption that the gain saturates independently at each frequency. In each case, the decrease of maser gain with radiation intensity involves an empiric constant, or saturation parameter, which is characteristic of the active medium.

Power and gain measurements at 1.15 μ on three He–Ne maser tubes of different diameter, in a cavity 1.75 m long, are found to satisfy the derived multifrequency power expression, and permit evaluation of the gain—saturation parameter for this gas mixture. The power expression, derived for a single transverse mode, is unexpectedly found to hold for multimode oscillations as well, within the range of measurements. From the measured saturation parameter and the derived expressions, the performance of amplifiers and other oscillators with the same active medium can be predicted.
Maximum Gain for Forward- and Backward-Wave Optical Maser Amplifiers
Authors: Jacobs H. , Holmes D. A. , Hatkin L. , Brand F. A.
Published: April 2005

An analysis has been made of the mechanism of amplification in a device consisting of three media. The first medium is considered to be air, the second medium a crystal having a specific dielectric constant and distributed negative conductivity of constant value, and the third medium is air. The equations for power gain in transmission and reflection are derived in a general manner. Following this, the condition on the length of the active region for maximum power gain in both forward and reflected modes of operation is approximated and also the magnitude of gain. When the development is applied to the ruby optical maser the length producing maximum gain is found to be the same for both the reflection and transmission-type amplifier. Furthermore as the length of the crystal is increased, oscillations are predicted at a single optimum value of the product of the negative attenuation constant and length.
Effective Diffusion Coefficient in Porous Media
Authors: Weissberg Harold L.
Published: April 2005

Recent calculations by Prager of upper bounds for the effective diffusion coefficient (or conductivity) in porous media, in terms of certain statistical parameters of the random geometry, are reformulated so as to apply specifically to a bed of spherical particles. The calculations are simplified by considering an idealized bed in which centers are randomly situated without restricting the spheres to nonoverlapping locations. The result, applicable to randomly overlapping spheres of either uniform or nonuniform sizes, gives the upper bound for the effective diffusion coefficient as φD0/[1−½lnφ], where D0 is the actual diffusion coefficient in a fluid which fills the void regions of the bed and φ is the void fraction. This result is compared with experimental results of various investigators for nonoverlapping spheres and also with Hashin and Shtrikman's expression for the best upper bound that can be calculated without taking the statistics of a particular random geometry into account.
Analytic Expressions Relating Surface Charge and Potential Profiles in the Space-Charge Region in Semiconductors
Authors: Lee Vin-Jang , Mason Donald R.
Published: April 2005

The potential on the surface of a semiconductor is formulated analytically as a function of surface charge concentration by a double integration of Poisson's equation in one-dimensional form. All combinations of the types of semiconductors and surface charge have been considered, as they produce accumulation, depletion, or inversion layers. The variation of diffusion potential as a function of distance from the surface towards the interior of the semiconductor is also discussed.
Nonhydrodynamic Attenuation of Shock Waves in Aluminum
Authors: Curran Donald R.
Published: April 2005

The attenuation of shock waves in 2024 aluminum has been studied experimentally by impacting aluminum flyer plates upon aluminum targets and measuring the target-free surface velocity as a function of target thickness. The results disagree with the predictions of hydrodynamic theory, exhibiting premature attenuation. An elastic-plastic model is proposed which adequately describes the data. In this model, Poisson's ratio remains constant under compression and the tensile yield strength increases linearly with compression, attaining a value of 12 kbars at a relative volume V/V0 of 0.86.
Higher-Order Spin-Wave Instability Excited by Parallel Pumping
Authors: Joseph R. I. , Schlömann E. , White R. M.
Published: April 2005

The parametric excitation of spin waves has been investigated theoretically without using the conventionally adopted approximation of neglecting those terms in the equations of motion that lead to the excitation of nonresonant components of the magnetization. The usually neglected terms generate instabilities of higher order in which the resonant frequency of the unstable spin waves equals an integer multiple of half the pump frequency. These higher-order instabilities should become observable if the dc magnetic field is high enough to suppress the lower-order instabilities.
Damping Spectrum of Iron
Authors: Petarra D. P. , Beshers D. N.
Published: April 2005

The internal friction of iron was measured from 0° to 400°C at 1 cps. The results were analyzed in terms of the magnetomechanical contributions to the damping, discernible peaks, and the remaining background. Three new features of the damping spectrum are reported: a magnetomechanical rise above 200°C which corresponds to the ΔE effect; a sharp, but unstable, rise in the background damping above 150°C with an apparent activation energy of approximately 16 kcal/mole; and a dislocation dragging peak in the vicinity of 125°C. The variation of each feature with nitrogen concentration, amount of cold work, and some other variables is reported. Changes in the magnetomechanical and background damping at high nitrogen concentrations are associated with a change in the mode of precipitation. Maringer's magnetomechanical peak is confirmed.
Oxide Formation on Magnesium Single Crystals. I. Kinetics of Growth
Authors: Schwoebel Richard L.
Published: April 2005

The kinetics of oxide film formation on the basal and prismatic planes of magnesium single crystals were investigated in an ultra-high vacuum microbalance system. A parabolic rate law describes the oxide film growth in an average thickness range of 50–1000 Å when formed at 400°C and 2.5 Torr oxygen pressure. The parabolic rate constant varies approximately as the one-sixth power of the oxygen pressure. If the rate constant is expressed in terms of the Arrhenius expression, exp (−Eact/RT), the experimental activation energy for oxidation of high-purity samples is Eact=39±3 kcal/mole. These three results are consistent with the Wagner—Hauffe theory of oxide growth by diffusion of lattice defects. The activation energy for oxidation can be shown to be the sum of the energy for extrinsic diffusion of cation vacancies in the oxide and one-third of the energy required to create a vacancy at the oxide—oxygen interface. Furthermore, the experimental parabolic rate constant can be calculated approximately by consideration of the associated interfacial defect equation. The kinetics of oxidation for crystals containing impurities of various valencies substantiate the hypothesis that the defect nature of the oxide is determined primarily by the formation of cation vacancies at the oxide—oxygen interface. It is postulated that vacancy formation at the interface is related to an oxygen adsorption—dissociation process occurring at selected sites on the oxide surface.
Oxide Formation on Magnesium Single Crystals. II. Structure and Orientation
Authors: Schwoebel Richard L.
Published: April 2005

The separation and examination of oxide films of 100–200 Å thickness from magnesium single crystals is described. The film separation is accomplished by sublimation of the metal crystal, leaving large areas of the oxide film intact at the sublimation site. Electron microscopy and selected-area diffraction have been used to determine the continuity, crystallite size, and epitaxy of the oxide films. This information is particularly useful in establishing a mechanism for the kinetics of oxide-film growth described in Part I.
Macroscopic Plastic Properties of Dislocation-Free Germanium and Other Semiconductor Crystals. I. Yield Behavior
Authors: Patel J. R. , Chaudhuri A. R.
Published: April 2005

Dislocation-free crystals of the semiconductor elements germanium and silicon and the compounds indium antimonide and gallium antimonide have been deformed in tension over a range of temperatures, initial dislocation densities, and strain rates. In all of the dislocation-free crystals, plastic deformation occurs at stresses that are low compared to those predicted from theory. The large yield drop observed in all four types of crystals is related to the dynamical behavior of dislocations during the early stages of plastic flow. There is a marked effect of the initial dislocation density on the maximum and flow stresses reached during yielding. Dislocations introduced by surface damage also reduce the observed yield drop. The pronounced yield drop and relatively large strain rate dependence of the maximum stress are a direct result of the relatively small stress dependence of dislocation velocities in semiconductor crystals. The temperature dependence of the maximum and flow stresses also appears to be related to the temperature dependence of dislocation velocities in semiconductors.
Recovery of Defects from 78° to 300°K in Cadmium Elongated at 78°K
Authors: Peiffer H. R. , Stevenson F. R.
Published: April 2005

The motion of defects in polycrystalline cadmium (99.99%) deformed at 78°K has been studied from 78° to 300°K using electrical resistivity measured at the deformation temperature as an index of the defect concentration. There appear to be three stages of recovery, the first two are centered at 98° and 138°K with activation energies of 0.21 and 0.35 eV, respectively. The latter recovery state, which is attributed to the motion of vacancies, shows a similarity in several respects to recovery found in cold-worked copper. A mechanism for the former recovery stage cannot be given; however, there is agreement in the number of jumps the defect makes before annihilation with the number in a recovery stage found in cold-worked copper. A more complicated recovery stage occurs from 228° to 258°K with an energy increasing from 0.70 to 0.89 eV. Above this last stage, the resistance rises because of the anisotropy of the resistivity and a changed orientation of the recrystallized cadmium.
Long-Range Channeling Effects in Irradiated Crystals
Authors: Lehmann Christian , Leibfried Günther
Published: April 2005

If an energetic atom, a primary, slows down in a lattice, it has the possibility of traveling long distances without essential interaction along almost force-free channels bordered by close-packed atomic chains. This effect has not been considered until recently, because, for the sake of simplicity, the lattice has been replaced mostly by a corresponding random arrangement. This ``channeling'' behavior has been found in machine calculations by Robinson, Holmes, and Oen which take the lattice structure into account. In this paper, the behavior of a primary moving along a channel bordered by the most densely packed directions is investigated analytically. Numerical results are given for a Cu primary moving in a Cu crystal, but the results can easily be extended to other cases. Two potentials are used: an exponentially screened Coulomb potential after Bohr, used also in the machine calculations and thought to give an adequate description for relatively high energies and small interatomic distances; and a purely exponential potential after Born—Mayer, better suited for relatively low energies and large atomic distances. The maximum ranges are very large, for 10 keV in the order of 103 lattice parameters for the Born—Mayer potential and up to 107 for the Bohr potential. Presumably, the Born—Mayer potential is a better description for these events. The investigation is confined to motions near the channel axis. Therefore, we only obtain the range distribution near the maximum range. From an adequate analysis of experimental data on long ranges of primaries, shot onto crystals in low indexed directions, one can obtain information about the potential at distances of about half the lattice spacing.
Deformation of Graphite by Thermal Cycling
Authors: Jenkins G. M. , Williamson G. K.
Published: April 2005

The dimensional changes which occur when graphite specimens are thermally cycled under constant torque have been measured. It is shown that internal stresses due to the anisotropic thermal expansion of individual component crystallites cause strain increments to appear which are a function of the temperature change—not of the absolute temperature. A model used to describe the stress-strain relationships of graphite at constant temperature is extended to describe this new phenomenon in terms of a change in internal stress distribution with change in temperature.
Fracture of Ge and Al2O3
Authors: Johnson O. W. , Gibbs P.
Published: April 2005

The fracture strength σF of germanium at constant loading rate has been determined over a temperature range from −196°C to 500°C. σF decreases slowly up to about 200°C, then increases to about 400°C, followed by subsequent decrease. σF is found to be essentially independent of ambient for a wide variety of chemical species. These observations are analyzed in terms of fracture nucleation at a flaw near, but not exposed to, the surface, by a presently unknown kinetic process. The role of dislocations apparently is to inhibit fracture by relaxation of stress concentrations up to about 400°C, above which general plastic deformation precedes fracture, suggesting the possibility of fracture nucleation by dislocation interactions. The applicability of this analysis to another brittle system, Al2O3, is considered in the light of its reported fracture, deformation, wear and friction characteristics. Striking similarities are found in the behavior of these two crystals, suggesting that the underlying mechanisms must have much in common.
Co60 γ-Radiation-Induced Point Defects in Bi2Te3
Authors: Smith M. J.
Published: April 2005

The effects of extended Co60 γ radiation upon the electrical resistivity, Hall coefficient, and magneto-resistance of Bi2Te3 have been examined. Co60 γ radiation causes an increase in the Hall coefficient in n-type Bi2Te3 and a decrease in p type. For γ-ray exposures in the range of 1018 photons cm−2, the apparent carrier removal rate is ∼10−1 carriers per Co60 photon. Thermal annealing of radiation-induced damage was also investigated. The results may be most consistently analyzed in terms of a model which consists of radiation-induced tellurium vacancies and interlaminar clusters of Te interstitials. The effects of the radiation-induced point defects are discussed. Evidence of an effect on impurity band conduction at low temperatures in n-type Bi2Te3 is observed.