bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic Relaxations in Zirconium-Niobium Alloys
Authors: Nelson C. W. , Gibbons D. F. , Hehemann R. F.
Published: April 2005

Acoustic measurements are reported which were made by the composite resonator technique on poly-crystalline and single-crystal specimens of Zr-Nb alloys (0%-25% Nb). Three distinct thermally activated relaxation peaks have been observed. In the frequency range 80–300 kc/sec, the relaxations occur in the neighborhood of 160°, 40°, and 12°K, with activation energies of 0.3, 0.05, and ∼0.02 eV, respectively. The relaxation which occurs at 12°K has only been observed in Zr-5% Nb. The 160° and 40°K relaxations have been demonstrated to be associated with the β → ω, athermal transformation. An atomic model for the 160°K relaxation process is presented and a tentative suggestion made for the origin of the relaxation at 40°K. No mechanism for the 12°K relaxation is attempted.
Yield and Angular Distribution of Cesium-Sputtered Molybdenum
Authors: Green J. B. , Olson N. Thomas , Smith Harold P.
Published: April 2005

A radioactive tracer technique has been adapted to the measurement of the yield (atoms/ion) and angular distribution (atoms/ion/sr) of molybdenum sputtered by a cesium ion beam normal to the (100) crystallographic face. The energy of the ion was varied from 1 to 7.5 keV, and the target temperature was varied from 77° to 473°K. The yield increased with energy and decreased with target temperature. Preferred emission in the 〈100〉 direction was measured, but emission in the 〈111〉 direction could not be resolved. The importance of ion channeling and the effects of thermal annealing on ion-induced damage are emphasized.
Role of the Cathode Field Emission in the Streamer-Spark Transition
Authors: Nasser E.
Published: April 2005

In a point-to-plane gap in atmospheric air streamers propagate under a voltage pulse from the point anode into the low-field region at high velocities and under continuous branching. It was found that electron emission from the copper cathode occurs under the effect of the high field between the streamer tips and the cathode just before impact. Photographic evidence by means of paper films placed on the cathode with sensitive emulsion facing it showed that at the points where strong streamer tips approached the back side of the film great concentrations of minute dots appeared. These dots are attributed to electron avalanches produced by those electrons liberated from the cathode and accelerated towards the streamer tip. The liberation of electrons was ascribed to the high field intensities at the tips since radiation cannot penetrate the paper. To confirm this, the back side of the paper was blackened at spots with no change in pictures. To further substantiate this, a thin metallic layer was placed at the back of the paper. No electrons were liberated and no dots appeared opposite the metallic layer because asymmetrical fields cannot build up between the two plane surfaces. The avalanches between film and cathode became diffuse when the air gap was increased to 3 mm since they merged into each other. At a gap of 5 mm, only a few avalanches were observed, of which some formed negative streamers as evidenced by distinct negative Lichtenberg figures on the film.
Technique for Measuring Vacancy Concentrations in Metals at the Melting Point
Authors: King D. , Cornish A. J. , Burke J.
Published: April 2005

A technique is described for measuring vacancy concentrations at the melting point by measuring the difference between the linear thermal expansion and the lattice thermal expansion. The method uses small specimens to facilitate eventual study of alloys and involves separate measurements of length change and lattice parameter change, the former by an interferometric technique and the latter by a diffractometer technique. The results of a study of 99.995% pure aluminum agree closely with the earlier measurements of Simmons and Balluffi, giving a vacancy concentration at the melting point of 8.7±1.2×10−4.
Acoustoelectric Waves in Piezoelectric Materials
Authors: Prohofsky E. W.
Published: April 2005

The electron-piezoelectric sound wave interaction gives rise to three distinguishable phenomena: gain, acoustoelectric effects, and nonlinear mixing. The acoustoelectric effects, through coupling to the gain, cause interaction between sound waves which give rise to flux wave propagations. These waves travel at the velocity of sound and can have gain much larger than that of the ordinary peizoelectric waves.

When the nonlinear mixing is taken into account, the mixing may be rapid enough to alter the collective wave to that of a second sound wave with velocity 1/√3 vs. The nonlinear mixing is examined, and it is proposed that the second sound conditions can only exist when a delicate balance is achieved between coherent gain and loss.
Multilayer Ohmic Contacts on CdS
Authors: Böer K. W. , Hall R. B.
Published: April 2005

A multilayer technique for evaporation of Ohmic contacts onto CdS is described. The electrical properties of these contacts do not change markedly after vacuum heat treatment up to 350°C. This technique consists of a sequential evaporation of a preparative layer, an active metal and possibly a covering metal. The Ti (preparative)-Al (active)-Pt (cover) sequence has been found most successful. All the more than forty evaporations investigated on CdS single crystals, or on evaporated recrystallized layers, showed Ohmic characteristics between 2 mV and 200 V and showed only generation-recombination noise above (at most) 300 Hz.
Some Transformations of the Onsager Relations of Nonequilibrium Thermodynamics
Authors: Lee J. S. , El-Saden M. R.
Published: April 2005

The Onsager relations of nonequilibrium thermodynamics are developed for cases where the phenomenological equations are subjected to a general transformation which embodies different types of partial inversions. The relations between the new and the old coefficients are established. Two significant cases are treated. In the first case the forces involved all have similar dependence on the particles' velocities. In the second case some of the forces are even functions and some are odd functions of the particles' velocities.
Spectral Extension of Potassium Photocathode Sensitivity
Authors: Ward Samuel A.
Published: April 2005

Photoelectric measurements on potassium deposited in argon at pressures of 1 to 24 Torr have shown photoemission which is spectrally extended into the red when compared to vacuum-deposited potassium. In addition, these cathodes have exhibited a larger magnitude of increase of output current with increase of anode voltage than that obtained with vacuum-deposited cathodes. A mechanism based upon the cathode structure formed by gas ambient deposition is presented to explain these effects.
Field Effect and Electrical Conduction Mechanism in Discontinuous Thin Metal Films
Authors: Milgram Alvin A. , Lu Chih-shun
Published: April 2005

A study has been made of the electrical conduction mechanism in discontinuous thin metal films. The high current density and field-dependent conductivity found in these films are shown to be due to the presence of trapping centers between metal aggregates. The charge carriers are created both by thermal excitation and by field injection. The charge transport mechanism is basically by tunneling via the trapping centers. The current I in a thin discontinuous metal film and the applied voltage V are shown to obey a simple relationship I = AV+BVn, where A and B are functions of temperature and n is a number equal to or greater than 2. Experimentally observed I–V characteristics of thin discontinuous chromium films over a wide temperature range are shown to be in good agreement with the theoretical model.
Dielectric Dissipation in NaCl and KCl below 4.2°K
Authors: Grissom David , Hartwig William H.
Published: April 2005

Dielectric loss tangents for NaCl and KCl single crystals are presented for the frequency range 40–1000 Mc/sec from 4.2° to 1.8°K. The tan δ-frequency-reciprocal temperature surface shows considerable structure with loss tangents in the range of 2–9×10−5. Debye relaxation associated with crystal defects appears to be the dominant mechanism, with individual peaks becoming resolved above the background caused by peaks at other frequencies.

A NaCl sample shows a loss peak near 300 Mc/sec at 4.2°K, with its high-frequency shoulder distorted by an adjacent peak. At lower temperatures the peaks move closer and to lower frequencies. The activation energy is estimated to be 0.0011 eV and occurs at approximately one lattice site in 5×1010. The loss mechanism suggested is electron relaxation between neighboring multivalent impurities. The loss would be indistinguishable at room temperature, but is calculated to occur at 4.6 Gc/sec with a peak loss tangent of 3.2×10−7.
Evidence of Turbulence in the Reaction Zone of Detonating Liquid Explosives
Authors: Mallory H. Dean
Published: April 2005

A technique is described which allows observation of small-scale pressure irregularities within and behind the detonation wave of condensed explosives. Photographs are shown which indicate strong turbulence in the detonation flow of some liquids.
Multiple Diffraction Effects in Annealed Permalloy Films
Authors: Alessandrini E. I.
Published: April 2005

Transmission electron diffraction and electron microscope techniques have been used in studying the effects of annealing temperatures on the structure of thin Permalloy films. Single-crystal and polycrystalline films were epitaxially grown by vapor deposition of an (81% Ni, 19% Fe) alloy on heated freshly cleaved (100) faces of rocksalt. Annealing experiments, at temperatures between 300° and 700°C, were carried out in an electron diffraction instrument after the films had been floated off the rocksalt and mounted on 200-mesh Ni grids.

The diffraction patterns of the single-crystal and polycrystalline as-grown and annealed films showed the effect of annealing twins on the number of extra reflections which appeared. The observed irrational spots and rings could be directly explained by the presence of twinning and double diffraction in a face-centered cubic structure. Weak reflections which appeared at forbidden (110) positions can be shown to result from double diffraction of (200), (020), and (002) positions, and are generated when {111} planes are textured and oriented in a [110] direction to the primary [100] orientation of the pattern. A dark-field electron microscopy study from these reflections further substantiates a double diffraction hypothesis. The reflections occur at temperature ranges below and above the critical ordering temperature for Permalloy and cannot be attributed to a superlattic structure. In addition, since annealing was carried out in vacuums in the high 10−7 Torr range, as well as in a reducing environment, the possibility that selective oxidation occurred was very unlikely.
Magnetic Hysteresis of Holmium Metal at 4.2°K
Authors: Safrata R. S. , Fisher T. R. , Shelley E. G.
Published: April 2005

Hysteresis loops are presented for a specimen of polycrystalline holmium metal at a temperature 4.2°K. The curves differ significantly from those previously reported, but such differences are not unexpected between two different samples of polycrystalline metal. Most qualitative features of the curves follow simply from single-crystal magnetization curves if a random distribution of c axes is assumed. The unusual position of the initial magnetization curve outside the hysteresis loops can be explained by a condition of zero-field stability for both a ferromagnetic and an antiferromagnetic structure.
Photoluminescence of Cu-Doped Gallium Arsenide
Authors: Queisser H. J. , Fuller C. S.
Published: April 2005

Photoluminescence measurements made at 20° and 77°K on Cu-diffused GaAs are compared with Hall-effect measurements on the same specimens. The level of the singly charged Cu acceptor lies 0.155 eV (20°K) above the valence band, compared to 0.145 eV (0°K) as determined by Hall effect. Intense phonon replicas indicate that this acceptor is strongly cojpled to the lattice; the observed discrepancy in the ionization energies may therefore be caused by a Stokes shift. Cu introduced into acceptor-doped GaAs under intrinsic conditions shows the same acceptor level, but this level is absent when Cu is diffused into extrinsic p GaAs. No luminescence is found which can be assigned to the interstitial Cu donor, possibly because this donor level is paired with the acceptor is 77°K. Diffusion of Cu into Te-doped GaAs causes the shift of a luminescence band at 1.2–1.33 eV; this is interpreted as a transformation of a donor-vacancy center into a donor—Cu center. Shallow acceptor levels at 0.020 and 0.027 eV are found in as-grown GaAs. These levels are not caused by Cu but are attributable, respectively, to carbon and possibly to silicon introduced during crystal preparation.
Annealing of Fast Neutron Damage in Impurity-Conducting n-Type Germanium
Authors: Wolf E. L. , Compton W. Dale , Depp S. W.
Published: April 2005

An annealing study of neutron-irradiated germanium containing 2.2×1017 cm−3 antimony is described. The samples originally exhibit a temperature-independent resistivity below 10°K, corresponding to an impurity conduction band distinct from the conduction band of the germanium. Irradiation introduces a small activation energy ε2 in the resistivity below 10°K. The activation energy ε2 and the 78°K carrier concentration change anneal together at about 300°C. The annealing results are compared with those obtained on more pure germanium irradiated with x rays.
Production and Diagnostic Measurements of Kilovolt High-Density Deuterium, Helium, and Neon Plasmas
Authors: Beckner Everet H.
Published: April 2005

This paper reports successful production and diagnostic measurements of kilovolt high-density plasmas of deuterium, deuterium-helium mixtures, helium, and neon. Particular attention was given to obtaining a systematic understanding of the electron and ion heating and cooling processes, as well as the attendant equilibration processes. These plasmas typically psosessed 1<Te<10 keV, 2×1019 <ne<1020 cm−3, 2×1018 <ni<1020 cm−3, copper contamination levels of nCu∼5×1017 cm−3, energy densities ∼105 J/cm3, and effective lifetimes ∼0.5 μsec. Diagnostic measurements were made with absolute time-resolved x-ray and neutron detectors, magnetic and electric probes, and high-speed visible photography. The plasmas were generated in a coaxial discharge tube, with the ions being heated primarily through collapse of the quasicylindrical current sheet, in a manner reminiscent of the linear pinch effect. The electrons rapidly achieved kilovolt temperatures via collisions with the energetic ions; radiation cooling of the electrons was observed, late in time, particularly for those plasmas consisting of high-Z ions.
Plasma Formed by a Laser Pulse on a Tungsten Target
Authors: Ehler A. W.
Published: April 2005

Results are presented of an experimental study of the plasma produced by the interaction of the focused light from a Q-switched laser with a tungsten target in a vacuum. The plasma radius, temperature, and radiative properties were measured during the period of the laser pulse. In addition, the target mass loss and plasma velocity and impulse were observed. Based on these experimental results, a model was developed which provides an energy and power balance for the expanding, radiating plasma.
Temperature Dependence of the Widths and Positions of the R and N Lines in Heavily Doped Ruby
Authors: Powell Richard C. , DiBartolo Baldassare , Birang Behzad , Naiman Charles S.
Published: April 2005

The widths and positions of the R and N lines in heavily doped ruby have been measured at temperatures from 13° up to 450°K. The results for the temperature dependence of the linewidths are explained in terms of microscopic strains, Raman scattering of phonons by the impurity ions, and direct phonon processes. The results for the lineshifts with temperature are due to the absorption and emission of virtual phonons. A Debye model of phonons is used with different effective phonon distributions for the linewidth and lineshift processes. Also the effective phonon distribution for the broadening of pair (N) lines is different from that for the broadening of single ion (R) lines.
Influence of Jog Concentration on the Conservative Motion of Dislocations in Copper
Authors: Petroff Pierre , Washburn Jack
Published: April 2005

In an annealed crystal of low dislocation density, the critical resolved shear stress necessary to move circular prismatic edge-dislocation loops along their glide cylinders was compared to the range of stresses within which various segments of the three-dimensional network began to move. Etch-pit observations showed that the first segments of the network moved at 2 g/mm2 but that only 60% had moved when the maximum resolved shear stress had reached 38 g/mm2.

Circular prismatic loops, which because of their shape have a high jog concentration, were found to move at a critical resolved shear stress greater than 50 g/mm2. It was suggested that jog concentration should be expected to vary from one segment to another of the three-dimensional network in an annealed crystal, and that this is probably one important reason for the widely different stresses at which individual segments begin to move.
Electronic Beam Scanning of Injection Lasers
Authors: Fenner G. E.
Published: April 2005

Experiments are described that resulted in the spatial scanning of the coherent emission of a GaAs junction laser at 77°K. By electrically separating the p side of the junction into several sections the current distribution is deliberately made nonuniform. Necessary conditions for the continuous shifting of the beam across the width of the diode are given. Several geometries, satisfying these conditions, are considered and evaluated with respect to simplicity of experimental verification. It was found possible to actually scan the beam continuously across the entire width of the diode (about ½ mm) by employing two fixed, pulsed, current sources and only one variable resistor.

Nonhomogeneities in emission intensity are related to the presence of ``spots'' reported since the early measurements in GaAs lasers. It is shown that these ``spots'' are determined by material parameters in the vicinity of the junction itself rather than by local conditions which might be caused by the current distribution.
Theoretical Efficiency of Pyroelectric Power Converters
Authors: Fatuzzo E. , Kiess H. , Nitsche R.
Published: April 2005

In recent years, a number of power converters utilizing the pyroelectric effect have been reported in the literature, and attempts at computing their efficiency have been made. In this paper the maximum efficiency for power converters made with nonferroelectric pyroelectrics, with ferroelectric pyroelectrics having a first-order ferroelectric-paraelectric transition, and with ferroelectric pyroelectrics having a second-order transition is computed. The last two cases have been evaluated starting from Devonshire's equations, which describe the properties of ferroelectrics better than other equations used in previous calculations of efficiency.
Photoelectric Properties of Lead Sulfide near the Threshold Region
Authors: Oman R. M. , Priolo Marilyn J.
Published: April 2005

The photoemission properties of the (100) surface of lead sulfide prepared by cleaving, cleaving and annealing, and ion bombarding and annealing have been investigated in the region within about 2 eV of the threshold. For the cleaved and annealed, or ion bombarded and annealed surface, the photothreshold is 3.8±0.1 eV giving an electron affinity of 3.4±0.1 eV. This value of electron affinity is lower than the 4.6 eV value previously reported and is found to be primarily dependent on surface preparation; the surface prepared in vacuum by cleaving and annealing or ion bombarding and annealing gives the lower threshold. Surfaces prepared by cleaving in air and then mounting in the vacuum apparatus have a higher threshold and lower yield than those prepared in vacuum. Subsequent anneal and/or ion bombardment of a surface prepared by cleaving in vacuum lowers the threshold and increases the yield even more significantly. Exposure of the freshly cleaved surfaces to oxygen at room temperature indicated a sticking coefficient of less than 10−4.
Stability of Coincidence Lattices for Chemisorbed Structures
Authors: Tucker Charles W.
Published: April 2005

The author previously reported a variety of coincidence lattices for oxygen chemisorbed on single-crystal faces of platinum by low-energy electron diffraction. The purpose of the present work is to show that theoretical calculations confirm the stability of such structures. For the case of two one-dimensional lattices it is shown that both a coulomb and a cosine interaction potential do not lead to any significant lowering of the energy for coincidence lattices. However, a variety of other potentials do favor the formation of coincidence lattices when the lattice parameters are in the ratio of small whole numbers. Since the Coulomb interaction leads to a potential which is virtually indistinguishable from the cosine potential for cases of interest, it is concluded that deviations from the cosine potential favor the formation of coincidence lattices. It is further concluded that in real cases such deviations exist.
Mode Selection Properties of Segmented-Rod Giant Pulse Lasers
Authors: Birnbaum Milton , Stocker Tom L.
Published: April 2005

The segmented-rod ruby laser structure has been operated as a giant pulse laser by use of a Kerr cell to provide the required Q switching. The giant pulse output, peak power of 106 W/cm2 and pulse width of 30 nsec, has been analyzed by use of Fabry-Perot etalons. The number of oscillating modes is shown to be similar to that previously observed in pulsed operation. Good agreement is found between the measured and computer-calculated frequency differences. The computer calculations presented indicate that the best performance can be expected when the two laser rod segments are of approximately equal length.
Mechanism of Ultrasonic Loss in Silicon and Aluminum
Authors: Sylwestrowicz W. D.
Published: April 2005

Attenuation in single crystals of silicon was measured as a function of frequency with a previously described technique. It was confirmed that, as in the case of aluminum, this dependence, in the range of frequencies from 20 to 110 Mc/sec, is of the form α=α0 exp (Cf), where α is attenuation, f is frequency, and α0 and C are constants. Heat-treating experiments indicate that the form in which oxygen is present in the material has a pronounced effect on the energy loss. Multiple scattering is proposed as a mechanism of loss in silicon and aluminum single crystals. An empirical model of multiple scattering is discussed.

It is confirmed that dislocations in silicon, at room temperature, do not contribute to the observed energy loss. Also it is proposed that the accepted relation for the evaluation of thermoelastic losses should be modified.
Observations of Dislocations in Ammonium Dihydrogen Phosphate: Production of Dislocation-Free Crystals
Authors: Deslattes Richard D. , Torgesen John L. , Paretzkin Boris , Horton Avery T.
Published: April 2005

The results of etch-pit and diffraction topographic studies on ammonium dihydrogen phosphate (ADP) are reported. These studies were carried out on specimens sectioned by abrasive wheel and string-saw from large single crystals grown from aqueous solution. The two characterization methods are shown to be in approximate one-to-one correspondence in the case of sections produced by abrasive sawing. Absence of both etch pits and topographic images in sections made by string-sawing of material well removed from the seed region is taken to indicate that this material is dislocation-free. Preliminary results on the plasticity of ADP are reported.
Observation of Earth Tides using a Laser Interferometer
Authors: Vali V. , Krogstad R. S. , Moss R. W.
Published: April 2005

The possibility of using a laser interferometer as a geophysical strainmeter was examined. A thermally stabilized laser was used and the results compared with a quartz Benioff strainmeter. From these measurements both long- and short-term stability of the laser radiation were calculated. The results indicate that the long-term stability is sufficient to observe earth tides while the short-term stability is better than 1:1010.
Pressure Dependence of the emf of Thermocouples
Authors: Hanneman R. E. , Strong H. M.
Published: April 2005

Possible factors contributing to relative and absolute emf corrections for thermocouples due to the effect of high pressure are evaluated in the present paper. These factors include contamination, plastic deformation, electrical shunting, and pressure and temperature gradients. The relative correction data from different experiments and different types of cells are compared. A method for obtaining the proper absolute corrections for Pt/Pt10Rh and Chromel-Alumel thermocouples for any type of high-pressure cell is presented.
Length Changes in Electron-Irradiated High-Purity Germanium
Authors: North J. C. , Buschert R. C.
Published: April 2005

Irradiation of a high-purity intrinsic single-crystal germanium sample at either liquid-helium or liquid-nitrogen temperature by 4.5-MeV electrons produced a large initial expansion which approached saturation with flux. The initial expansion at liquid-helium temperature of ΔL/L=+78×10−24 per incident electron/cm2 is nearly an order of magnitude larger than has been observed in either n- or p-type material. The magnitude of this effect is difficult to account for on the basis of the observations of the n- and p-type samples, and the difficulty of interpretation is compounded by the fact that no electrical measurements can be made on pure material at low temperatures. Two highly speculative models are briefly discussed.
Polycrystalline Spin Wave Theory of Ferromagnetic Resonance Compared with the Tilting Experiment
Authors: Risley A. S. , Johnson E. G. , Bussey H. E.
Published: April 2005

Schlömann's spin wave theory of polycrystalline ferromagnetic resonance has been tested in detail using the tilting method reported earlier. Among the quantities measured were the linewidth ΔH, and the maximum value of the imaginary part of the effective susceptibility (χm″)eff. The measurement method is equivalent to measuring asymmetric (Nx≠Ny) ellipsoids and thus, introduces another shape dependence in addition to that due to spin waves. Direct comparison with the symmetric (Nx=Ny) form of the theory is inaccurate. A proper comparison can be made in two ways: (1) generalizing the theory to include the Nx≠Ny case and then using the data directly, (2) transforming the data and then comparing with the Nx=Ny theory. Both comparisons are reported and their equivalence is demonstrated.

It is concluded that Schlömann's theory does not fit the data within the spin wave (SW) manifold. It is suggested that the theory of Sparks may provide a better fit. The difference between coupling models seems to be the basic difference between the two theories.

Experimentally and theoretically, ΔH and (χm″)eff are different quantities. The dispersive effects of spin wave coupling are shown to be the cause of the difference between the theoretical ΔH and (χm″)eff.
Isotopic Mass Dependence of Li Diffusion in Rutile
Authors: Johnson O. W. , Krouse H. R.
Published: April 2005

Mass spectrometric measurements of isotope fractionation of interstitial Li in TiO2 (rutile) have been made which indicate, within experimental error, agreement with the expected M−½ dependence of the diffusion coefficient D. The major source of error apparently was variation of D due to inhomogeneities in the specimen.
Magnetization of Iron-Beryllium Alloys
Authors: Aldred A. T.
Published: April 2005

Saturation magnetizations of bcc iron-beryllium alloys were measured, and the results were used to calculate mean atomic magnetic moments. The linear rate of change of moment with solute concentration was found to be −2.262±0.108 Bohr magnetons per atom. This was considered to be consistent with a model where beryllium, a nontransition metal solute, dilutes a constant iron moment.
Quantitative Measurements of the Optical Emission from Dense Theta-Pinch Discharges
Authors: Feldman J. M.
Published: April 2005

Measurements of the optical emission of the high luminosity theta-pinch discharge are reported for seven gases over the interval 0.2 to 0.7 μ. The irradiance is typically 0.4 J/100 Å at 450-J input energy. The efficiency is typically 5% to 10%. The optical pulse duration is approximately 5 μsec. The dependence of the optical output power on bottle material, coupling parameters and input power is discussed.
Studies of Ruby Superfluorescence and Population Inversion
Authors: Avizonis Petras V. , Willoughby William R.
Published: April 2005

It was found that by observing the fluorescent intensity of ruby along its longitudinal axis during pumping, an appreciable amount of information may be obtained. It was observed that the time at which population inversion occurs during a pump cycle is directly observable from the time-resolved fluorescent intensity. A method for establishing the actual population in the metastable state from the fluorescent intensity is demonstrated and cross correlated with two other methods for measuring population inversion. The rate equation describing population inversion has been solved including the nonlinear stimulated emission loss term, and complete agreement with experiment is demonstrated. For the particular pumping geometry used, maximum energy available, and ruby quality and size, maximum metastable population of 1.21×1019 ions/cm3 was achieved, representing 75% inversion.
Diffusion of Hydrogen in Copper-Palladium Alloys
Authors: Piper John
Published: April 2005

The diffusion of hydrogen in copper-palladium alloys has been studied by utilizing the dependence of electrical resistivity upon hydrogen concentration—a technique both rapid and simple. At 25°C the diffusion coefficient in the range 0–58 at.% Cu is relatively insensitive to alloy composition but is extremely sensitive to the α-β phase change: it increases two orders of magnitude to become 5×10−5 cm2/sec when the crystal structure of the alloy system changes from face-centered cubic to ordered body-centered cubic. Measurements at 130°C indicate that this large increase is due to a decrease by a factor of three in the activation energy for diffusion. The ratio of the diffusion coefficient for hydrogen to that for deuterium in the body-centered cubic alloy was found to be approximately 1.5.
Electroreflectance Studies in GaAs
Authors: Seraphin B. O.
Published: April 2005

Measurements of the electroreflectance effect on GaAs surfaces in the range of photon energies from 1.3 to 4.5 eV are reported. If an ac electric field modulates the surface potential in the reflecting surface, the reflectance responds in a sequence of pronounced peaks at the photon energies of interband transitions, as they are known from previous analysis of the band structure. However, the high resolution and sensitivity of this derivative technique adds a new kind of information. The shift of the observed groups of peaks with electric field establishes an experimental criterion which discriminates among parabolic edges of the M0 type and saddle-point edges of the M1 type. This provides, for the first time, an unambiguous guideline for the phase of band structure analysis which deals with the assignment of structure in the optical properties to interband transitions. Strong structure in the reflectance response below the fundamental absorption edge is tentatively assigned to an absorption for which the initial state is an impurity level. Information gained from such structure below the fundamental edge, approximately coinciding with the photon energy of radiative transitions in GaAs, complements the large amount of work, experimental and theoretical, aimed at this spectral region, particularly in GaAs.
Paramagnetic Resonance of Ce3+ in Yttrium Aluminum Garnet
Authors: Lewis H. R.
Published: April 2005

Paramagnetic resonance measurements have been made at 4.2°K and 9 kMc/sec on Ce3+ in Y3Al5O12(YAG). The measured g values are gZ=2.738, gX=1.872, and gY=0.91. These values can be fitted accurately if an admixture of ∼0.1 of the J=7/2 state is added to the J=5/2 ground state. There is evidence of a small, field-dependent component of the g value. This is used to get a rough estimate of the splitting of the lowest quartet state.
Electromagnetic Breakdown of Air
Authors: Clavier P. A. , Webb L.
Published: April 2005

A theory of breakdown is proposed based on the dynamic energy balance between competing physical phenomena and on the common formulation for electromagnetic energy absorption in a plasma. The comparison with experimental results is favorable.
Rapid Electron-Density Oscillations on the Axis of a Theta Pinch
Authors: Gerardo J. B. , Bialecke E. P. , Hirsch R. L.
Published: April 2005

A detailed temporal history of the electron density on the axis of a theta pinch is presented. During the magnetic compression, oscillations are superimposed on the electron density. The amplitude of these oscillations is, under some conditions, as large as 50% of the maximum value attained in the pinched state. These density variations are ascribed to radial hydromagnetic oscillations. The electron density measurements were made by means of a spherical laser interferometer and these were correlated with electron density measurements using Stark broadening techniques.
Deviations from BCS Behavior in the Temperature Dependence of the Ultrasonic Absorption in Superconducting Tin
Authors: Olsen Tore , Claiborne Lewis T. , Einspruch Norman G.
Published: April 2005

The temperature dependence of the attenuation of compressional ultrasonic waves has been measured in high-purity single crystals of superconducting Sn. Deviations from BCS behavior have been observed. The experimental results are compared on the basis of frequency dependence, state of anneal, deformation, and sample thickness. It is shown that the deviations from BCS behavior are similar to those found for Nb-Zr, Nb-Mo, La, and polycrystalline Sn. It is also demonstrated that the temperature-dependent absorption peaks are not a property of the pure type I superconductor but are related to both the defect structure and the sample size.
Effect of Chemical Combination on the Soft X-Ray K Emission Spectrum of Boron
Authors: Fischer David W. , Baun William L.
Published: April 2005

Major changes due to chemical combination are observed in the soft x-ray K emission spectrum of boron. The largest changes occur between elemental boron (B), boron nitride (BN), and boron oxide (B2O3). Spectra obtained from these compounds using a stearate crystal are compared with results of previous workers from a ruled grating. Points of agreement and differences are noted. The spectra were obtained from a flat-crystal vacuum spectrometer using a flow-proportional counter and electron excitation.
Influence of Electrode Curvature on Electrical Breakdown in Vacuum
Authors: Miller H. Craig
Published: April 2005

It has been observed by others that a decrease in curvature of one (or both) electrode(s) of a vacuum gap can lead to either an increase or decrease, depending upon the gap parameters, in the breakdown voltage. This electrode curvature effect is investigated theoretically for a system consisting of two isolated spheres. For each sphere the maximum surface field intensity and the area over which the field magnitude is no less than a given fraction of this maximum are found. These results are considered in conjunction with several theories of vacuum breakdown in order to predict the expected dependence of breakdown voltage upon electrode curvature at varying gap lengths. Comparisons with applicable published experimental results are made. The following conclusions are drawn: (1) The cathode crossover effect, that is, the observation that a decrease in curvature of the cathode can produce a decrease in breakdown voltage at short gap lengths and an increase in breakdown voltage at long gap lengths, can be predicted explicitly for a two-sphere system using any major vacuum breakdown theory. This crossover is confirmed experimentally. (2) The anode crossover effect is experimentally supported, but not as firmly as the cathode crossover. The theoretical analysis suggests that this anode crossover effect results from a transition, at a critical gap length, in the dominant mechanism in electrical breakdown in vacuum. (3) The increase in breakdown voltage accompanying an increase in curvature of one (or both) electrode(s) at short gap lengths is explained on the basis of a decrease in breakdown area (sites).
Screw Dislocation Arrays in a Plate
Authors: Chou Y. T.
Published: April 2005

A simple analysis is presented of linear arrays of screw dislocations in a thin plate. A typical case is shown in which a symmetrical array (normal to the central plane) of positive and negative screw dislocations is blocked at both ends under a uniform shear stress. The relationship between number of dislocations, length of the array, applied stress, and thickness of the plate is derived. The number of dislocations increases rapidly as the ends of the array approach the surface. The equivalence of the symmetrical array to a longitudinal shear crack in a plate is also identified.
Polarization Reversal Electroluminescence at Low Frequencies in Barium Titanate Crystals
Authors: Bhide V. G. , Shringi S. N.
Published: April 2005

Audiofrequency-induced electroluminescence in BaTiO3 single crystals is studied as a function of the strength and the frequency of the applied field, the temperature of the crystal, the nature of the electrode material, and the biasing field. It is shown that this electroluminescence differs in characteristics and origin from the previously reported radiofrequency-induced electroluminescence and is intimately associated with polarization reversal.
Etches for Revealing Dislocations and Growth Striations in PtSb2
Authors: Sagar A. , Faust J. W.
Published: April 2005

The etching of PtSb2 was investigated. It was found that the common acids would not attack this material indicating that it has a low percentage of ionic character to the bonds. An etchant to reveal dislocations and segregation striations was found. To reveal segregation striations, an impurity is necessary. The dislocations can be revealed on the three major crystallographic directions on both n- and p-type material as can segregation striations.
Growth of Broad Linewidth Ruby Crystals
Authors: Adams I. , Nielsen J. W. , Story M. S.
Published: April 2005

Progress has been achieved in perfecting the technique for the growth of ruby from flux and broadening the fluorescent linewidth by Ga additions. Line broadening was achieved in flux-grown ruby crystals both by the deliberate addition of Ga and by the substitution of O2− by F− during crystal growth. Broadening in excess of 10 cm−1 was obtained due to a combination of these factors. Solubility of pure Al2O3 in PbF2 was found to be reduced about 10% by the addition of 0.02 mole % Cr. Chemical analysis of the crystals shows a concentration gradient exists for Cr but not for Ga.
Low-Temperature Thermal Conductivity of Amorphous Polymers: Polystyrene and Polymethylmethacrylate
Authors: Reese W.
Published: April 2005

Measurements of the thermal conductivity between 4.5° and 1°K are reported for four commercial samples of polymethylmethacrylate and two commercial samples of polystyrene. It is shown that the thermal conductivity in this temperature range can be understood in terms of Klemens' theory of the thermal conductivity of amorphous substances in which the role of transverse vibrations is unimportant at low temperatures. Further, it is shown that the thermal conductivity of a partially oriented sample of polymethylmethacrylate is but slightly higher along the direction of stretch than for an unoriented sample; hence that vibrations along the polymer chains do not play a dominant role in the transport of heat at liquid-helium temperatures. Indirect measurements of the specific heat of these substances have also been performed and yield C/T3=735±50 erg/cm3-(K°)4 for polystyrene and C/T3=446±38 erg/cm3-(K°)4 for polymethylmethacrylate.
A Test of Viscous Dislocation Damping Theory
Authors: Fiore Nicholas F.
Published: April 2005

The amplitude-independent dislocation damping of a series of dilute copper-germanium single crystals has been studied as a function of composition and frequency. The measurements have been performed at room temperature on annealed and γ-irradiated single crystals driven in longitudinal resonance at 80 and 240 kc/sec by means of the Marx piezoelectric oscillator.

The results indicate that the Granato-Lücke viscous damping analysis cannot account for the observed magnitude and composition dependence of the damping, although the damping is proportional to frequency in agreement with their theory. They further show that a γ-ray dose of 2×108 rad is sufficient to suppress the damping to a composition-independent value of 1×10−4 which does not decrease with further irradiation. There is evidence that the total damping consists of a composition-dependent edge dislocation loss superposed on a composition-independent screw dislocation loss.
Elastic Constants of Sodium Chlorate Single Crystals by Pulse-Echo Method
Authors: Viswanathan R.
Published: April 2005

The velocities of the ultrasonic waves in sodium chlorate crystal, viz., V12 and V13, with propagation direction (100) and vibration direction (010) and (001), respectively, are found to be equal to within 0.1%. This shows that the classical theory of elasticity is adequate to describe the elastic behavior. The elastic constants of this crystal, obtained by the author using the pulse-echo method, are also reported. The effect of piezoelectricity on the elastic constants of sodium chlorate crystal is shown to be too small, well within the present experimental accuracy.
Coherent Spin-Wave—Phonon Interactions in Thin Magnetic Films
Authors: Wigen P. E. , Dobrov W. I. , Shanabarger M. R.
Published: April 2005

The excitation of microwave ultrasonics by ferromagnetic resonance in magnetic thin films at 10 Gc/sec has been analyzed on the basis of a spatial inhomogeneity in the internal field as treated by Kooi.1 Four types of magnetoelastic interaction processes were studied experimentally in thin Permalloy films at X band: phonon excitation by spin waves (M→P), spin-wave excitation by phonons (P→M), re-excitation of spin waves by phonons which were originally produced by spin waves (M→M) and the attenuation of piezoelectrically generated and detected phonons by spin waves (P→P). Observations were made in films with compositions varying from 77% Ni to 85% Ni. In each film distinct spin-wave modes were observed and a one-to-one correspondence between the spin-wave modes and the phonon modes could be determined. A value for the magnitude of the transverse magnetoelastic constant was obtained from the measurements of the P→P process. Using the measured value of b2, conversion coefficients were computed for the M⇆P and M→M processes. Comparison with experiment yields a discrepancy of approximately 5 dB for the M⇆P processes and about 15 dB for the M→M process for the modes n<6. The calculated value of the magnetoelastic constant, the mode number dependence of the spin-wave—phonon interaction intensities for the M⇆P and M→M processes, and the frequency dependence of the M→M process strongly favor the volume inhomogeneity model over the surface spin pinning model. The results of this work are reported in greater detail elsewhere.2
Magnetostriction in Nickel Ferrite and Cobalt—Nickel Ferrite
Authors: Smith A. B. , Jones R. V.
Published: April 2005

The magnetostriction constants λ100 and λ111 for nickel ferrite have been measured using a ferromagnetic resonance technique which also permits measurements of linewidth, g factor, and anisotropy on the same sample. Our measurements show that all of these parameters are essentially temperature independent from 4° to 300°K in contrast to the behavior of other ferrites. The magnetostriction results are: λ100=−46×10−6, λ111=−22×10−6 at room temperature with less than a 20% variation from these values down to 4°K. The temperature independence of the linewidth and its magnitude (∼20 Oe) both indicate an absence of the ferrous ions which have complicated measurements by some other investigators. Measurements have also been made of the magnetostriction of Co0.05Ni0.95Fe2O4 over the range ∼100° to 300°K. At room temperature both λ100 and λ111 have approximately the same values as in NiFe2O4, but at lower temperatures the cobalt contribution causes |λ111| to increase sharply while |λ100| is relatively unaffected. This behavior is qualitatively in agreement with a theory by Slonczewski for the similar problem of Co2+ in magnetite. The sign of λ111, however, is different in the two materials. Linewidth in the three principal directions in Co0.05Ni0.95Fe2O4 has also been measured.
Field Distribution in a Hard Superconductor with Adiabatic Field Change
Authors: Gauster W. F. , Ullmaier H. A.
Published: April 2005

Wipf and Lubell have investigated flux jumping in Nb-25%Zr under nearly adiabatic conditions.1 They considered a semi-infinite slab for the purpose of calculating a critical value of the external field under the condition that this value is reached before the magnetic wave front hits a boundary of the superconductor. These calculations hold approximately for solid cylinders with large diameters and agree well with experimental results.

We have extended Wipf and Lubell's calculations to solid and hollow cylinders of arbitrary radii. The shape of the penetrating magnetic wave has been computed. The boundaries of the superconductors are taken fully into account. As might be expected, the data with hollow cylinders deviate very appreciably from those obtained with solid cylinders. In the case of a semi-infinite superconducting slab the critical field depends only on the specific heat function of the superconductor. In our more general case, however, the critical field is affected also by the dependence of the critical current density upon the local values of the magnetic field and the temperature. Experiments on solid and hollow cylinders of NbZr and Nb3Sn verify these calculations.
Effects of Ferromagnetism and Local Order on Electrical Resistivity of Au-Fe Alloys
Authors: Sundahl R. C. , Chen T. , Sivertsen J. M. , Sato Y.
Published: April 2005

The electrical resistivity of a series of Au-Fe solid solutions, from 4.53 to 40 at. % Fe, has been measured from 1.50° to 350°K. Measurements were made on foils which had been (Q) quenched from 900°C and (A) quenched and subsequently aged at 75°C for 1 week. Results indicate that (1) the general shape of the ρ(T) curves can be explained by a spin-disorder scattering model for ferromagnetic alloys, (2) changes in the ρ(T) curves on aging are similar to those found in the magnetization and Curie temperature, and (3) alloys of less than 10% Fe exhibit a transition at temperatures similar to those found from Mössbauer measurements.

The residual resistivity ρ0 of these alloys goes through a maximum at 12% Fe and decreases for larger concentrations, indicating that all spins are not ferromagnetically ordered. This spin-disorder contribution to ρ0 decreases when the quenched alloy is aged at 75°C.
Interaction of Spin Waves with Drifted Carriers in Solids
Authors: Vural Bayram
Published: April 2005

Interaction of θ=0° spin waves with drifted helicons is analyzed, and a convective instability is predicted. The mechanism for amplification is due to the second-order rf electron field in the drift direction. This Lorentz field, Ez=ṽtrans×B̃trans=ṽtrans×μeffH̃trans is large because μeff is large in the region of synchronism between the spin wave and the electrokinetic wave.