bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrodynamic Analysis of Noise in a Finite-Temperature Electron Beam
Authors: Hsieh H. C.
Published: April 2005

On the basis of a small-signal, one-dimensional analysis, a set of basic macroscopic differential equations, governing the fluctuations in quantities such as the electron-beam temperature, the mean velocity, and the current density, has been derived by taking moments of the Liouville equation with respect to the velocity variable. This set of differential equations expresses the conservations of charge, momentum, and energy, and is valid for an arbitrary amount of velocity spreading and includes the effect of heat conduction.

A system of differential equations, governing the correlation among the fluctuations in the mean velocity, current density, and beam temperature, is also derived. The relationship among the various noise parameters along the electron beam is obtained in the form of a system of differential equations whose solution gives detailed information on the variation of the noisiness parameter along the beam. The solution of the system of differential equations thus derived is also discussed.
Shear and Longitudinal Magnetoelastic Waves in Transversely Magnetized Rods
Authors: Comstock R. L. , Wigen P. E.
Published: April 2005

An analysis is presented of the propagation of magnetoelastic waves in transversely magnetized rods. Efficiencies for longitudinal wave-spin wave and shear wave-spin wave conversion are evaluated for the case of a [1̄10] rod magnetized along [111]. A longitudinal to shear wave converter in yttrium iron garnet is discussed which is estimated to have 20-dB conversion efficiency at 3 Gc/sec.
Extension of the Aukerman-Willardson Two-Band Hall Coefficient Analysis
Authors: Allgaier R. S.
Published: April 2005

Aukerman and Willardson's analysis of the temperature dependence of the two-band Hall coefficient is extended to higher carrier concentrations, where the statistics are no longer classical. It is shown that the Hall coefficient behavior evolves in a characteristic fashion, and that useful information may be extracted from this behavior. Experimental Hall data on n-type GaAs and GaSb and on p-type GeTe, SnTe, PbTe, and Bi2Te3 are found to conform to the predictions of the theory. The importance of distinguishing carefully between the effects of temperature and carrier concentration is emphasized, and it is shown that confusing the two can and has led to erroneous interpretations of experimental data.
Radiation-Induced Conductivity in Plastic Films at High Dose Rates
Authors: Compton D. M. J. , Cheney G. T. , Poll R. A.
Published: April 2005

A study has been made of the radiation-induced conductivity (RIC) in poly[ethyleneterephthalate] (Mylar) films, using pulses of electrons of energies up to 30 MeV from a linear accelerator. The absence of polarization indicates that electronic conduction is responsible for the RIC, which has typical values of ∼10−8 Ω−1 cm−1 at 5×109 rad(Mylar)sec−1. The RIC is a bulk effect and shows both a ``prompt'' portion which falls very rapidly at the end of an electron pulse and a ``delayed'' portion which persists for milliseconds. The prompt portion varies as the 0.8 power of the dose rate and is independent of pulse width. The delayed portion varies as a lower power, saturating at dose rates of ∼1010 rad(Mylar)sec−1. The decay of the delayed portion is hyperbolic, and its rate is independent of temperature. The RIC increases monotonically with temperature in the range 100°–300°K. This behavior corresponds to a model in which one sign of carrier is rapidly and permanently trapped, the delayed conductivity being due to the other sign of carrier remaining free until it recombines. The saturation of the delayed conductivity is ascribed to a finite number of such traps.
Infrared Properties of NiO and CoO and Their Mixed Crystals
Authors: Gielisse P. J. , Plendl J. N. , Mansur L. C. , Marshall R. , Mitra S. S. , Mykolajewycz R. , Smakula A.
Published: April 2005

The room-temperature reststrahlen spectra of flame fusion grown NiO and CoO, as well as those of three intermediate members of this solid solution series, are presented. A full Kramers-Kronig analysis on all members has been performed and checked with damped oscillator calculations. The resulting refractive indices, extinction coefficients, dielectric constants, effective ionic charges (Szigeti q*), and characteristic frequencies are presented along with the lattice constants and are discussed in the light of their interrelation.
Localized Mode Measurements of Boron- and Lithium-Doped Silicon
Authors: Spitzer W. G. , Waldner M.
Published: April 2005

High-resolution, room-temperature, infrared absorption measurements of boron- and lithium-compensated silicon are reported. Isotopic shifts of the observed absorption bands with changes in lithium and boron isotopes are given. The absorption strengths of the bands at 681, 655, 584, 564, and 522 cm−1 associated with lithium-boron pairs, are all proportional to the impurity concentration from ∼2×1018 to 1020 cm−3. Weak bands associated with unpaired boron are also observed in the same samples at 644 and 620 cm−1. The 522 cm−1 band shifts to 534 cm−1 with change in lithium isotope and is nearly independent of the boron isotope. The frequencies of the remaining bands depend almost completely on the boron isotope.
Electrical and Thermal Resistivities of the Nonmagnetic Transition Metals with a Two-Band Model
Authors: Colquitt Leroy
Published: April 2005

A two-band spherical model is used to represent the conduction electrons of the nonmagnetic transition metals with an incomplete d shell. It is shown by comparison with experimental results that phonon-induced interband s-d transitions are the major contributor to the electrical and thermal resistivities ρ and W at all but the lowest temperatures. Consequently, the momentum gap between the s and d bands is an important parameter of the theory and may be used to classify the behavior of ρ and W. At the lowest temperatures it is found that the experimental data for ρ of all the transition metals studied may be consistently interpreted if it is assumed that electron-electron scattering processes are important.
Cleavage Surface Energy of NaCl and MgO in Vacuum
Authors: Gutshall Paul L. , Gross Gordon E.
Published: April 2005

The cleavage energies of single crystals of NaCl and MgO were measured in vacuum and in liquid nitrogen. The average value of the cleavage energy of NaCl while submerged in liquid nitrogen was 317 erg/cm2 as opposed to 283 erg/cm2 in vacuum at 77°K. The cleavage energy of MgO is 1300 erg/cm2, which agrees with values obtained at 300°K in air and in liquid nitrogen. This lack of atmospheric influence may be due to the inability of contaminants to diffuse into the crack tip of the specimen.
Preparation and some Properties of Mg2Ge Single Crystals and of Mg2Ge p-n Junctions
Authors: Kroemer H. , Day G. F. , Fairman R. D. , Kinoshita J.
Published: April 2005

A technique was developed for the preparation of high-quality single crystals of Mg2Ge with controlled dopings. It utilizes the reaction of stoichiometric amounts of the constituents in a graphite crucible inside a hermetically sealed tantalum bomb, followed by the solidification of the molten compound into a single crystal by lowering the bomb through a temperature gradient (Bridgman technique). Several crystals without intentionally added dopants were grown as well as crystals to which the donors antimony, arsenic, boron, the acceptor sodium, or the apparently insoluble element uranium, had been added.

A technique was also developed for the preparation of p-n junctions on n-type Mg2Ge, utilizing the alloying to and diffusing into the Mg2Ge of a thin evaporated gold film. p-n junctions prepared in this way exhibit undesirably large reverse currents, but high breakdown field strength and very pronounced surface passivation properties, which might make Mg2Ge a desirable material for MOS (metal-oxide-semiconductor) devices.
Excitons in InP at High Excitation Levels
Authors: Casella R. C.
Published: April 2005

The possibility of observing collective effects of electrons and holes in InP under intense optical irradiation from GaAs lasers is examined. At 2°K, the exciton density at which a postulated Bose-Einstein condensation might occur is 1.3×1015 cm−3. It is shown that at this density another collective effect (shielding of the Coulomb potential) may cause excitons to dissociate. However, the criterion for exciton dissociation is too crude to resolve this question. The requisite light intensity to observe the effects discussed is estimated to be ∼5–100 W/cm2, whereas intensities ∼104 W/cm2 are available over a spot with diameter 0.1 mm.
Third-Order Elastic Constants of Ge, MgO, and Fused SiO2
Authors: Bogardus E. H.
Published: April 2005

The third-order elastic constants of germanium, magnesium oxide, and fused silica have been measured using the pulse superposition method for determining the ultrasonic velocity as a function of both uniaxial and hydrostatic pressure. From these measurements all six third-order elastic constants were calculated by using the equations of Thurston and Brugger for MgO and Ge, and the three independent isotropic third-order constants were calculated for fused SiO2.

The results for Ge are in good agreement with the most recent data of McSkimin and Andreatch. The results for MgO agree in part quite well with theoretical data calculated from a Born-Mayer potential. Drastic failure of the three Cauchy relations indicates the presence of many body forces. For fused silica, the remaining Cauchy relation is, as may be expected, not well fulfilled.
Effects of Uniaxial and Inhomogeneous Stress in Germanium and Silicon p-n Junctions
Authors: Rindner W.
Published: April 2005

Results are reported of experimental investigations of the effect of uniaxial compression up to 1.8×1010 dyn-cm−2 on grown Ge and Si junctions and of strongly inhomogeneous stress applied directly to the junctions. In Ge, agreement in sign and in magnitude within factors of about two and ten, respectively, was obtained between the currents induced by uniaxial stress in 〈111〉 and 〈110〉 directions and those predicted by a bandgap mechanism. No significant effect of uniaxial stress up to about 1.5×1010 dyn-cm−2 on the reverse-bias current was found in Si (111) junctions; however, changes in breakdown voltage and of forward-bias current were observed. The presence of crystal defects is shown to enhance sensitivity to uniaxial stress and, in Si, was found to be a necessary condition for an effect on the reverse-bias current. Defects introduced by strongly localized stress appear to play a similar role to those active in uniaxial stress effects. It is concluded that the bandgap mechanism proposed by Wortman et al. applies both in Ge and in Si, but that it is partially masked in the latter by stress-independent generation-recombination currents. The plausibility of a generation-recombination mechanism, possibly such as that proposed by Bernard et al., as an underlying cause of the effects of high localized stress is discussed.
Double Acceptor Behavior of Cu in Te-Doped GaAs
Authors: Allison H. W. , Fuller C. S.
Published: April 2005

Ionization energy levels introduced in Te-doped GaAs after conversion to p type by diffusion of 64Cu have been measured by means of Hall effect. Levels at 0.145, 0.166, 0.20, and 0.44 eV are observed after various sequential heat treatments. The 0.145 and 0.44 eV levels are attributed to the two acceptor levels expected of Cu on a Ga site. The 0.20 eV level is assumed to arise from a Ga vacancy as previously reported, and the 0.166 eV level is interpreted as an ion pair between Cu on a Ga site and Te on an As site.
Analytical Line Shapes for Lorentzian Signals Broadened by Modulation
Authors: Arndt Rolf
Published: April 2005

General analytical expressions are given for the line shapes of Lorentzian signals broadened by modulation. The results are discussed for the cases of the first and second harmonic. The linewidths and the signal intensities have been calculated analytically as a function of the modulation amplitude.
Field-Evaporation End Form of Tantalum
Authors: Nakamura Shogo , Müller Erwin W.
Published: April 2005

A field-evaporation end form depends in a complicated way upon many factors. The end form of a pure and nearly perfect metal crystal as obtained under various conditions must be established experimentally to permit proper interpretation of field-ion micrographs of general specimens of that metal. The end form of tantalum, distinctly different from other bcc metals such as tungsten, molybdenum, and iron, is shown in its dependence on temperature, hydrogen promotion, and field-stress-induced slip. Low-coordination atom sites stabilized by polarization occur in specific crystallographic regions.
Calculations of Midgap Breakdown in Gases
Authors: Ward A. L.
Published: April 2005

Calculations were made with an electronic computer for comparison with the measurements by Tholl of midgap breakdown in a N2–CH4 mixture. Tholl used a 3-cm gap, 400-Torr pressure, and an overvoltage of 20.7%. For the calculations, a one-dimensional Townsend avalanche model was used, which includes space charge but omits photoionization in the gas. The input data were adjusted to give agreement with Tholl's measured avalanche velocity and current-growth time constant in the absence of space charge. The initial effect of space charge was calculated to be a reduced current growth rate occurring concurrently with an increased avalanche velocity toward the anode, as noted by Tholl. The calculated values of these quantities for this current regime differ by a factor of ∼2 from the measured values, but this discrepancy could be due to the discharge channel expansion and to energy considerations. The later stage of current buildup is marked by a very rapid current buildup occurring at the time that the ``streamer'' propagates toward the cathode. Good agreement is obtained in this time regime. The cathode-directed streamer is shown to result from a secondary avalanche from the cathode. The moving junction between the primary and secondary avalanches is marked by a reduced channel diameter in Tholl's photographs. It is shown that this constriction of the discharge channel could not be caused by radial fields.
Instabilities in the Magnetization Vector in YIG at High Microwave Power Levels
Authors: Bodway George E. , Wang S.
Published: April 2005

At microwave power levels above that necessary for spin-wave growth in YIG coherent relaxation oscillations are observed for three distinct values of Hdc. The location of one of the regions and its change with power level agree closely with the location of a foldover region for Mz calculated by Suhl. Information is obtained on the relationship between the longitudinal relaxation time and the relaxation time of the oscillations by using spheres with different linewidths and by obtaining results at 300° and 77°K. The amplitude of the oscillations is also compared to the value of M0—Mz which is present just before the oscillations take place. The information obtained strongly indicates a foldover process is involved in the three regions.
Deformation Twinning in Face-Centered Cubic Crystals
Authors: Ramaswami B.
Published: April 2005

The twinning stress, the choice of the twinning plane, and the mode of propagation of twinning observed for silver single crystals are orientation-dependent. The concept that cross-slip and deformation twinning are dependent relief mechanisms and the onset of one increases the stress required for the other relief mechanism leads to a logical explanation of many observations on deformation twinning of fcc crystals.
Optical Properties of Cold- and Hot-Deposited Gold Films
Authors: Davey John E. , Pankey Titus
Published: April 2005

Gold films have been vacuum deposited onto quartz substrates in a temperature range from 5° to 750°C. Films which are deposited below about 50°C exhibit decreases in reflectivity of up to 25% over bulk values. Associated with this decrease are large increases in resistivity and near amorphous x-ray diffraction patterns yielding particle sizes of less than 250 Å. Films deposited above 350°C exhibit a superficial matte appearance and reflectivities which decrease to lower values with increasing deposition temperature. Associated with the onset of the matte appearance and the decrease of the reflectivity (for hot deposition) is lamellar particle growth in the plane of the films which increases, both in extent and depth, with increasing deposition temperature. Bulk values of reflectivity and electrical resistivity are observed with deposition in the temperature range between 240° and 350°C. The decrease in reflectivity for cold deposited films is explained on the basis of the Maxwell Garnett—Gans theories.
Sputtering Studies of Insulators by Means of Langmuir Probes
Authors: Jorgenson G. V. , Wehner G. K.
Published: April 2005

The sputtering threshold energy and low-energy sputtering yields for films of sputtered quartz and Pyrex were measured with Langmuir probes. The probe characteristic is very sensitive to deposits of insulating material because even very thin insulating films cause radical changes in electron acceptance. A thin insulator film of known thickness is deposited on the probe by rf sputtering, and a known fraction of that film is removed by enforcing a dc bias voltage on the probe. Different bias voltages require different times to remove the same amount of material (as monitored in the probe characteristic), and one can use this as a very sensitive method for collecting sputtering yield data. Analysis of the deposit sputtered from a quartz target in a 10−2 Torr Ar discharge shows it to be SiO1.6. The sputtering yield curve for this SiO1.6 is presented and shows a yield of ∼0.1 molecules/ion at 100 eV with a sputtering threshold of ∼16 eV.
Study of Ion-Bombardment Damage on a Ge (111) Surface by Low-Energy Electron Diffraction
Authors: Jacobson R. L. , Wehner G. K.
Published: April 2005

An atomically clean and highly ordered Ge (111) surface was bombarded with Ar+ ions and the bombardment effects were studied by low-energy electron diffraction. Degradation characteristics of the (10) beam were most extensively investigated over an ion energy range from 10 eV to 1 keV with ion dosage ranging from 1012 to 1016 ions/cm2. The degradation characteristics determine the mean area of damage per incident ion. This area is 7×10−14 cm2 for a 1-keV Ar+ ion and 1×10−15 cm2 for a 40-eV ion. At low ion energies, some retention of (10) intensity is noted even for large dosages, indicating in this case that some short-range order is retained. The minimum ion energy for damage is ∼20 eV. This value is close to the sputtering threshold energy and the reported displacement energy of Ge. A bombardment damage model is proposed to explain the low-energy ion-bombardment characteristics. Thermal recovery of the bombarded surface shows a dependence on ion energy and also on total bombardment dose.
X-Ray Diffraction Study of Argon Crystal Growth
Authors: Peterson O. G. , Batchelder D. N. , Simmons R. O.
Published: April 2005

Diffraction studies were carried out near 4°K on the influence of rate and method of growth upon the perfection and microstructure of 99.998% purity argon crystals. The crystallography of the twinning observed was directly verified to be of the type expected for a fcc crystal. Some idea of the dislocation content of a well-annealed argon crystal was obtained. It was concluded that it should be possible to produce crystals having a perfection adequate for a variety of quantitative lattice studies.
Pressure Transmitters for use at Very Low Temperatures
Authors: Towle Laird C.
Published: April 2005

The shear strengths of solid argon and krypton have been measured by both direct and indirect extrusion techniques in the temperature ranges 32° to 81°K and 59° to 112°K, respectively. The shear strength of these materials is found to increase from 5 bars near the melting point to 100 bars near the lower temperatures indicated. Based on shear strength measurements these solidified gases are sufficiently soft and plastic somewhat below their melting points to serve as suitable pressure transmitters for high-pressure experiments. Because their shear strengths increase rapidly as temperature is reduced, it is recommended that, where practical, pressure be applied just below their melting points and the test apparatus subsequently cooled to the temperature of interest.
Diffusion-Limited Climb Rate of a Dislocation: Effect of Climb Motion on Climb Rate
Authors: Balluffi R. W. , Seidman D. N.
Published: April 2005

The diffusion-limited climb rate of a straight dislocation immersed in a nonequilibrium concentration of point defects was calculated in the quasisteady-state approximation. It was shown that this approximation should apply in many cases of interest. Full account was taken of the effect of the dislocation climb motion while treating the problem of the diffusion of defects from (or to) the dislocation. The effect of the climb motion was expressed in terms of the dimensionless parameter vR/2D, where v is the climb velocity, R is the radius of the diffusion field of the climbing dislocation, and D is the point-defect diffusivity. For vR/2D«1, the effect of the climb motion was negligible. For vR/2D»1, the climb rate tended to be faster than that calculated by ignoring the climb motion. It was shown, however, that under usual conditions the climb motion could never be an important factor affecting the diffusion-limited climb rate. The results were applied briefly to some recent data for climbing dislocations in gold.
Mechanical Properties of Thin Nickel Films
Authors: Grunes R. L. , D'Antonio C. , Kies F. K.
Published: April 2005

Vapor-deposited nickel films in the thickness range 700 to 4000 Å were stressed to fracture in uniaxial tension in the as-deposited condition and after annealing at 650°C for 3 h or at 700°C for 5 min. The existence of a strength dependence on thickness was observed for both the as-deposited and annealed films; however, the as-deposited films were 1½ to 2 times stronger than annealed films of comparable thickness. The thickness-strength relationship for as-deposited films was found to be σ = 134 kg/mm2+(1675 Å kg/mm2)t−½, while that for the annealed was σ = (−.0245 kg-mm−2/Å) t+155.6 kg/mm2. Both the annealed and as-deposited films exhibited fracture strengths in excess of bulk nickel of analogous structure.

It is believed that the observed high strengths of as-deposited nickel films are due in part to the high defect density arising from the vapor deposition process and to the proximity of the film surfaces which further inhibits dislocation motion. With regard to the latter, a mechanism involving dislocation pile-up is proposed.
Spectroscopic Technique for Probing an Ionized Gas
Authors: Winocur Joseph , Pyle Robert V.
Published: April 2005

Ionized strontium is studied by the method of resonant absorption of optical radiation. Because of an accidental frequency overlap, normal rubidium can be used in a lamp as the source of resonant light. Spectral profiles of absorption were made with a scanning Fabry-Perot interferometer. The 5s½−6p½ line of Rb and the 5s½−5p½ line of Sr+ are found to differ by 0.014 Å. Optical and Langmuir probe measurements of density compare favorably. Ion temperatures in a steady-state and a decaying plasma were determined from the Doppler width. Two different sources of ionized strontium plasma are described. Negative results were obtained in an attempt to optically pump strontium ions in a plasma.
Silicon/Corundum Epitaxy
Authors: Porter J. L. , Wolfson R. G.
Published: April 2005

The crystallographic aspects of silicon/corundum epitaxy were investigated. Epitaxial deposition was carried out on corundum substrates of two orientations, and the observed crystallographic relationships were shown to be determined by three-dimensional matching between the silicon structure and the sublattice of possible cation sites in corundum.

Single-crystal silicon layers were deposited onto (0001) and (8̄629) corundum substrates. For growth on (0001) corundum, (111) silicon is parallel to the interface with [1̄10] silicon parallel to [2̄110] corundum. For growth on (8̄629) corundum, the silicon plane parallel to the interface is irrational, but the epitaxial relationship closely approximates to the following: (001) silicon parallel to (0001) corundum with [1̄10] silicon parallel to [2̄110] corundum.

These two epitaxial relationships are the only ones which permit three noncoplanar symmetry axes of the silicon to coincide with three such axes of the cation site sublattice of the corundum. They insure compatible surface symmetries and similar surface densities on an arbitrary deposit/substrate interface. In general, the silicon atom density on the interface does not exceed the cation site density. When it does so, however, the rational crystallographic relationship is modified slightly in order to lower the density of silicon atoms below that of the possible cation sites.
Dislocations and Stacking Faults in Rutile Crystals Grown by Flame-Fusion Methods
Authors: Barber D. J. , Farabaugh E. N.
Published: April 2005

Single crystals of rutile, grown by the Verneuil method, have been chemically thinned and examined by electron transmission microscopy. The density and distribution of dislocations agree with that expected from etch pit data. This density is at least two orders of magnitude below that for rutile films formed by oxidizing titanium carbide. The etching of dislocations and stacking faults is described.

Some preliminary results of high-temperature studies in the microscope are reported. These include the discovery of a hitherto unknown slip system, {001} 〈100〉.
Quantum Efficiency and Radiative Lifetime in p-Type Gallium Arsenide
Authors: Vilms Jüri , Spicer William E.
Published: April 2005

A new method for the study of radiative recombination in uniformly doped semiconductors has been developed and applied to p-type gallium arsenide. The bulk quantum efficiency is obtained by measurement of photoluminescence as a function of the penetration length of the exciting radiation. Using an estimated electron mobility, the total recombination lifetime of electrons (minority carriers) is found from this photoluminescence measurement and also independently by the measurement of surface photovoltage. The radiative lifetime is determined from the bulk quantum efficiency and the total electron lifetime. The model on which these measurements are based accounts for the principal factors affecting the intensity of photoluminescence, i.e., bulk quantum efficiency, surface recombination, and refraction and reflection of luminescence at the sample surface. The model is consistent with the experimental data for the p-type gallium arsenide samples studied.

The bulk quantum-efficiency values obtained here are 8% at 300°K and 28% at 80°K for two higher-efficiency samples and 6 times lower for a third sample. The radiative lifetime of electrons is found to be approximately 2×10−8 sec at 300°K, and 3×10−10 sec at 80°K. The total lifetime of electrons (minority carriers) is found to be approximately 1.5×10−9 sec at 300°K and 10−10 sec at 80°K for the two higher-efficiency samples, and 10−10 sec at both temperatures for the third sample.
Dislocation Kink in a Crystal Model
Authors: Sanders W. T.
Published: April 2005

A modified Frenkel—Kontorova dislocation model, with a piecewise linear substrate potential, is extended to two dimensions to describe the entire slip plane of the dislocation with one kink. Accurate solutions are found, with the aid of several analytic techniques and a digital computer, for the static configuration under applied stress. The kink Peierls stress σk P, the kink width w, and the kink energy F, are determined for a range of values of γ, the perfect crystal shear strength. σk P is found to be very sensitive to γ, and to have maxima of the order of 10−6 to 10−5, in units of the shear modulus. w and E are less sensitive to γ; w ranges from ∼4 to ∼30 lattice parameters, while E varies from several hundred to several thousand degrees Kelvin for typical crystal parameters.
Proposed Gas Maser Pumping Scheme for the Far Infrared
Authors: Wells Willard H.
Published: April 2005

A scheme that is analogous to the operation of a heat engine is proposed for exciting maser action in the far infrared and submillimeter parts of the spectrum. A beam of hot molecules interacts through distant collisions with a cold gas of another species at very low pressure. Certain energy levels in the hot gas are cooled faster than others owing to coincidental resonances in the spectra of the two gases. In the partially cooled nonequilibrium state, population inversions are possible in the hot species.

To demonstrate feasibility, the interaction between pure rotational states of HCl and HF is discussed in detail. Barring unforeseen experimental difficulty (e.g., chemical activity of HF) the Schawlow-Townes condition for maser action can be satisfied by the J=3 → 2 transition in HF at 123.1 cm−1, or 81.25 μ.
Observations on Electromigration and the Soret Effect in Tungsten
Authors: O'Boyle Dennis
Published: April 2005

Observations on both electromigration and the Soret effect in tungsten have been recorded using silhouette electron microscopy and electron microscan techniques. The surface structure developed when a tungsten wire is heated by a current density of 3.3×104 A/cm2 depends on whether the current is direct or alternating. An alternating current produces a smooth surface structure while a direct current produces a steplike structure due to electromigration of tungsten ions. The direction of the electromigration of tungsten ions is toward the cathode in agreement with the theories of Huntington and Fiks.

Soret effect diffusion has been observed in tungsten wires when subjected to a temperature gradient of 5000°C/cm. Either electromigration or Soret effect diffusion can produce pronounced changes in the original geometry of the conductor resulting in large current density variations over a short wire segment.
Volume Compressibility of BeO and Other II-VI Compounds
Authors: Cline Carl F. , Stephens Douglas R.
Published: April 2005

The volume compressibilities of BeO, ZnS, CdS, CdSe, and CdTe have been measured to 45 kbar. Solid-solid transitions were observed in CdS, CdSe, and CdTe at 17.5, 21.3, and 31.8 kbar, respectively, with corresponding volume changes of 16.0%, 16.4%, and 16.4%.
Light Scattering by Shock-Cooled Isotactic Polypropylene Film
Authors: Keijzers A. E. M. , Van Aartsen J. J. , Prins W.
Published: April 2005

An absolute low-angle light scattering photometer is described which is used for the quantitative evaluation of the light scattering exhibited by shock-cooled isotactic polypropylene films. Following Stein and Wilson the supermolecular order is considered to be describable in terms of a density correlation function γ(r) and an orientation correlation function f(r), which are both dependent only upon the magnitude of the distance r between individually scattering volume elements. By means of Fourier transformations performed upon the horizontally and vertically polarized components of the scattered light under polarized incident light, these functions can be obtained. It is found that γ(r)=exp(−r2/a2), with a ≅40 000 Å and f(r)=B exp(−r2/b2)+C exp(−r2/c2), with B=0.544, b=4500 Å, C=0.456, and c=17 000 Å. The density correlation thus reaches much further than the orientation correlation. This is ascribed to the poorly developed spherulitic crystallization due to the shock cooling of the sample. This meaning of the splitting up of f(r) into two Gaussian distributions needs to be explored further. The occurrence of a Gaussian density correlation function γ(r) rather than the simple exponential function γ(r)=exp(−r/a) found for amorphous polymers by Debye and Bueche, might be ascribed to the spherical crystalline aggregates in the sample, which are visible under the polarizing microscope. Calculation shows that a collection of spheres will indeed give a scattering pattern approximately describable by γ(r)=exp(−r2/a2). Further work on samples with varying thermal history will have to reveal the connection between the correlation functions and the molecular processes leading to specific supermolecular arrangements.
Variational Method of Determining Effective Moduli of Polycrystals: (A) Hexagonal Symmetry, (B) Trigonal Symmetry
Authors: Peselnick Louis , Meister Robert
Published: April 2005

Variational principles of anisotropic elasticity have been applied to aggregates of randomly oriented pure-phase polycrystals having hexagonal symmetry and trigonal symmetry. The bounds of the effective elastic moduli obtained in this way show a considerable improvement over the bounds obtained by means of the Voigt and Reuss assumptions. The Hill average is found to be in most cases a good approximation when compared to the bounds found from the variational method. The new bounds reduce in their limits to the Voigt and Reuss values.
Vapor Growth of GaP on GaAs Substrates
Authors: Oldham W. G.
Published: April 2005

An open-tube vapor deposition process has been used to grow GaP epitaxially on GaAs seeds. The overgrowths generally contain large numbers of defects including dislocations, stacking faults, impurity striae, and local strains. The stacking faults and impurity striae may be eliminated by growing on (1̄1̄1̄)-plane seeds under carefully controlled conditions. The mobility of electrons in n-type GaP is found to increase from approximately 120 cm2/V sec at 300°K to approximately 600 cm2/V sec at 77°K. Undoped GaP layers are invariably n-type with carrier concentration in the range 1015–1017/cm3.
Temperature Dependence of the Critical Fields of a Superconducting Pb-Tl Alloy
Authors: Sekula S. T. , Kernohan R. H.
Published: April 2005

Using a conventional ballistic technique, magnetization curves of a superconducting Pb-27% Tl alloy have been obtained from the transition temperature Tc=6.43°K down to 1.70°K. The thermodynamic critical field curve indicates that this alloy is of the strong coupling type. The Ginzburg-Landau parameters deduced from several features of the magnetization curves are given and their temperature dependence is compared to theoretical models.
Segregation of a Nonvolatile Impurity during Normal Freezing in an Off-Stoichiometric Melt under Constant Component Pressure
Authors: Lorenz M. R.
Published: April 2005

The effect of segregating a nonvolatile impurity during normal freezing in an off-stoichiometric melt under constant component pressure is examined. A modified normal freeze equation is derived relating the impurity concentration in the solid to the fraction of original melt solidified for any off-stoichiometric melt composition. The correction term in the modified equation becomes significant for segregation coefficients of the order of unity and melt compositions appreciably off stoichiometry.
Beam Divergence and Far-Field Patterns of Rubies of Varying Optical Quality
Authors: Kellington C. M. , Katzman M.
Published: April 2005

Beam divergences were measured and far-field patterns photographed for 37 ruby rods of different quality. The growth with pumping power of the most intense portion of the laser beam was measured for two rods of very different quality. An autocollimator reticle image was photographed after passage through each rod. Correlation of beam divergence with optical parameters is discussed.
Slip-Induced Directional Order in Fe-Ni Alloys. I. Extension of the Chikazumi-Suzuki-Iwata Theory
Authors: Chin G. Y.
Published: April 2005

In the present paper, calculations have been made for the magnetic anisotropy developed in cold-worked iron-nickel alloys near the 75% Ni composition. The treatment is based on the slip-induced directional order theory of Chikazumi et al. [J. Phys. Soc. Japan 12, 1259 (1957)]. The theory states that in an ordered ferromagnetic solid solution (long- or short-range order, or clustering), slip results in the creation and preferential alignment of distinct type(s) of atom pairs (e.g., Fe–Fe) which lead to an induced magnetic anisotropy. The important conclusion from this theory is that the direction of the induced easy axis of magnetization depends sensitively on the orientation of the deforming crystal and the geometry of the deformation process, as well as the type and degree of ordering in the alloy. The present treatment extends the original analysis for the case of rolling to single crystals of several new orientations: (110)[1̄12], (110)[1̄10], (111)[1̄1̄2], (112)[1̄10], and (112)[1̄1̄1]. These orientations, plus those studied by Chikazumi et al. ((100)[001], (100)[011], and (110)[001]), contain the most likely operating slip systems whose slip directions are symmetrically disposed about the rolling direction and are hence more stable than others during rolling. Some of these orientations are important components of texture in recrystallized or cold-rolled polycrystalline face-centered cubic materials. In addition to the rolling analysis, calculations have been made for the anisotropy resulting from drawing of wires with 〈111〉 and 〈001〉 axial orientations. These two orientations are likewise prominent components of polycrystalline wire textures.

The present work shows that drawing of a 〈001〉 wire induces a hard magnetic direction along the wire axis, while this axis becomes an easy direction if the orientation is 〈111〉. For rolling, except for the cases of (001)[100] and (110)[001] studied by Chikazumi et al., where the induced easy axis lies along the transverse direction, most other orientations generally place the easy axis along the rolling direction. This suggests a plausible explanation for the observation that the rolling direction becomes an easy axis of magnetization when a randomly oriented polycrystalline aggregate is rolled. This work also predicts that rolling of {112}〈111〉 and {110}〈112〉 textures (symmetrical variants included), which are prominent texture components in rolled Permalloy, results in an easy axis along the rolling direction. Suggestions for experimental testing of the theory are discussed.
Absolute Instabilities of Perpendicularly Propagating Cyclotron Harmonic Plasma Waves
Authors: Crawford F. W. , Tataronis J. A.
Published: April 2005

Computed dispersion characteristics are presented for perpendicularly propagating electron cyclotron harmonic waves in an infinite plasma having a delta-function transverse electron velocity distribution and an arbitrary longitudinal velocity distribution. It is shown that in general the propagation occurs in passbands centered on the cyclotron harmonic frequencies and that a given mode can carry positive or negative rf energy depending on the frequency and wavenumber. This suggests the possibility of growing waves in finite plasmas due to interaction with slow wave circuits. Even in an infinite plasma, as the ratio of plasma frequency to cyclotron frequency increases, modes in successive passbands couple to each other, leading to wave growth in time. This represents absolute instability of a type which may be closely related to effects observed in some thermonuclear fusion studies and other laboratory plasmas. There may also be important applications of these modes to the construction of practical microwave oscillators and amplifiers.
Etching and Polarity in CdS Thin Films
Authors: Vecht A. , Grindle W. , Mears R.
Published: April 2005

The use of orthophosphoric acid for the observation of etch pits in CdS thin films is demonstrated. From these studies, some suggestions as to the polarity and crystal growth processes in these thin films are put forward.
Magnetization and Switching Characteristics of Composite Thin Magnetic Films
Authors: Goto Eiichi , Hayashi Nobuo , Miyashita Takaaki , Nakagawa Keisuke
Published: April 2005

Composite magnetic thin films consisting of layers of different magnetic materials in close molecular contact with one another are studied. Because of ferromagnetic exchange coupling between spins, the magnetization in the neighborhood of the interface of the layers is expected to rotate continuously as in Bloch walls. The experimental magnetization curve of an extremely soft magnetic layer on an extremely hard magnetic layer agrees well with the theoretical curve based on such rotation models. Drastic deformations in critical switching curves from the asteroid of conventional uniaxial films, improvement in nondestructive reading characteristics, and existence of a new switching mode which is dependent upon the sequence of external magnetic fields are also expected from a theory based on a lumped-constant approximation to the continuous rotation model. All of these theoretical predictions have been confirmed by experiments using electroplated composite films.
Thermoluminescent Formation of Cr2+ in Magnesium Oxide
Authors: Wertz John E. , Coffman Robert E.
Published: April 2005

In undoped crystals of MgO, x irradiation converts a large fraction of Cr3+ in octahedral symmetry to Cr2+. Heating such crystals until a blue thermoluminescence has been observed causes further reduction. Usually 95% or more of the Cr3+ is converted by the combined treatments. However, in Cr-doped MgO one is able to reduce only a small fraction of the octahedral chromium to Cr2+. The Cr2+ is reconverted to Cr3+ by heating. ESR measurements show that in the same temperature interval nearly all of the Fe1+ formed on x irradiation has disappeared. The source of electrons acquired by Cr3+ thus appears to be the Fe1+ ions. The thermoluminescence is ascribed to the Cr3+-electron interaction, as suggested by Hansler and Segelken.
Radiation from a Horizontal Dipole in a Semi-Infinite Dissipative Medium
Authors: Lien Roy Harold
Published: April 2005

Expressions for the electric field due to an oscillating horizontal dipole placed in a semi-infinite dissipative medium have been derived for the case when the frequency is low. The main work involves the evaluation of some complex integrals which have been reduced to forms suitable for numerical computation.
Reverse Characteristics of High Inverse Voltage Point Contact Germanium Rectifiers
Authors: Simpson J. H. , Armstrong H. L.
Published: April 2005

A theory of the reverse characteristic of high inverse voltage germanium rectifiers is developed, which takes account of the radial symmetry of the point contact and the presence of positive holes in the ``inversion region'' of the semiconductor. The field at the metal is found to consist of three components. The first component varies inversely with the radius of the contact and directly with the applied voltage for larger voltages. The second component is produced by the impurity centers and varies approximately as the cube root of the voltage. The third component is produced by the positive holes in the inversion region and is approximately constant. This last component lowers the effective barrier height for rectifiers made of very pure material. The first is the more important of the variable components and is responsible for increases in current resulting from image force and tunnel effect at high voltages. In the former case the logarithm of the current varies as V½ and in the latter as V2 approximately.

Current-voltage curves of the predicted forms have been found experimentally using short rectangular pulses varying in length from 2 to 10 μsec to minimize thermal effects. Where possible, barrier heights are determined by measurements over a range of temperatures and detailed numerical comparisons of theoretical and experimental data are made. The two sets of data are in remarkably good agreement thus implying that the theoretical picture is essentially correct.
Metrization of Phase Space and Nonlinear Servo Systems
Authors: Kang Chi Lung , Fett Gilbert H.
Published: April 2005

By introducing a proper distance function, the phase space for a servomechanism is completely metrized. A new approach is developed to study servo systems directly on the basis of instantaneous performance under an arbitrary input function. A criterion for determining the effect of nonlinearity on performance is obtained. It will serve as basis for the design of nonlinear servo systems.
Method of Time-Free Solutions for Radioactive Decay and Radionuclide Production
Authors: Gold Louis
Published: April 2005

A time-free recursion formula development for the classical radioactive decay leads to a distribution form of solution for both natural and artificial chains.
Preparation of Uniformly Dispersed Specimens of Particulate Matter for Electron Microscopy
Authors: Hartman R. E. , Green T. D. , Bateman J. B. , Senseney C. A. , Hess G. E.
Published: April 2005

The transfer of monolayers of proteins to solid surfaces from a liquid substrate is now a well-established procedure. It has been found that if particulate matter is present in the protein solution from which the monolayer is to be formed, the surface streaming set up by the spreading of the protein over the surface of a liquid substrate causes the particles to be distributed uniformly throughout the available surface. They can then be transferred to a solid surface along with the protein monolayer. This procedure has been used in the preparation of specimens for electron microscopy by raising previously immersed collodion-coated wire mesh screens, attached to glass microscope slides, through the interface occupied by the monolayer. Micrographs of viruses, bacteria, and other bodies mounted in this manner have been obtained. The method commends itself by virtue of the simplicity of the procedure, the uniform dispersion of the particles, the elimination of interference from extraneous dissolved substances, and the high quality of the micrographs obtained.
The Extinction of Predominantly Subharmonic Oscillations in Nonlinear Systems
Authors: Ludeke Carl A. , Pong William
Published: April 2005

This paper describes the use of an electromechanical analog to examine the limiting values of various parameters needed to destroy a predominantly subharmonic oscillation of order one-third, existing in a nonlinear system. The results of the analog are then compared with the limiting values suggested by existing theory.
Formation of Vortex Streets
Authors: Birkhoff Garrett
Published: April 2005

It is shown that, for vortex trails in a nonviscous fluid, the mean longitudinal spacing a and mean transverse spacing h are invariant. It follows from this and other known facts, that the periodicity of a vortex trail is unstable, not the ratio h/a.

In a viscous fluid, a is invariant but h increases. This fact explains various known experimental observations.

A rough explanation is given for the order of magnitude of the Strouhal number S, based on the inertia opposed by the wake to transverse oscillations.

Finally, using the theory of logarithmic potential, it is shown that, even in a nonviscous fluid, the concentration of vorticity is limited to circles whose diameter is about a/4.
Recovery Currents in Germanium p — n Junction Diodes
Authors: Shulman R. G. , McMahon M. E.
Published: April 2005

When a germanium p — n junction biased in the forward direction has a reverse voltage suddenly applied, a large transient current flows during the ``recovery time.'' A proposed mechanism for this current involving diffusion of stored minority carriers to the barrier is compared with experimental results. Since the current is related to the diode forward direction characteristics these are examined. Finally a variable time delay utilizing the recovery current effect is discussed.
The Ferry Reduction and the Activation Energy for Viscous Flow
Authors: Hopkins I. L.
Published: April 2005

The relationship proposed by Ferry and his co-workers for the effects of frequency and temperature on the dynamic properties of certain polymers is shown to lead to a method for calculating the activation energy of viscous flow from relaxation, creep, and dynamic test data, the results agreeing with those obtained in steady-state flow. The Ferry reduction explains, and is supported by, observed increases in dynamic modulus and viscosity with increasing temperature.