bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Lattice and Thermal Mismatch on the Coercive Force of GdIG Films
Authors: Stein B. F. , Kestigian M.
Published: February 2004

The effect of lattice and thermal mismatch on the coercive force and the perfection of GdIG films grown by chemical vapor deposition has been studied. The films were deposited on YAG, GdGaG, and mixed (GdNd) GaG and (GdLa) GaG substrates, which were prepared with lattice parameters closely matching the lattice parameter of GdIG. A decrease in coercive force by a factor of four was found between films grown on YAG and Gd0.75Nd2.25 GaG substrates. This improvement is discussed in terms of interfacial and volume strains which are caused by lattice and thermal mismatch.
Control of Domain Propagation in Magnetic Thin Films
Authors: Matsushita S. , Konishi S. , Sakurai Y.
Published: February 2004

Magnetic domain propagation behavior in narrow channels composed of a Permalloy thin film imbedded in a high coercive film is discussed in this paper. The domain propagation is affected by channel shape and by magnetic potential barriers in the channel. The domain-wall velocity along the channel can be controlled by the demagnetizing field in the channel. The domain grows along the channel under applied pulse fields. To obtain a stepwise movement of domain wall under pulse fields, periodic barriers of magnetic potential comprising high coercive force film were introduced. When the demagnetizing field in the channel is larger than 1/3 of the intrinsic coercive force of the channel material, an oval domain nucleates and shifts along the channel under successive applied field pulses. Reversed domains are observed using the Kerr magneto-optic effect.
Movement of Crystal Inclusions in a Centrifugal Field
Authors: Wilcox W. R. , Shlichta P. J.
Published: February 2004

A centrifugal field can cause migration of solvent inclusions in crystals, both by the preferential sedimentation of the denser solute ions and by diffusion across the concentration gradient caused by the variation of solubility with pressure. The two mechanisms can act either in the same or in opposite directions so that both centripetal and centrifugal migration are possible. Aqueous inclusions in KI were observed to move centripetally at about 0.05 mm/h at room temperature in centrifugal fields of 210 000 G; at higher temperatures the direction of migration was reversed. Inclusion movement was also observed in KCl and Pb(NO3)2. Plastic deformation, cracking, and changes in inclusion shape were also encountered.
Resistivity Tensor Elements in Silver Measured Using Helicon-Like Waves
Authors: Giovanielli D. V. , Merrill J. R.
Published: February 2004

Elements of the anisotropic resistivity tensor R of silver were measured for a large range of field directions. Helicon standing-wave resonances in flat plate samples were used to measure the tensor elements Rij. Samples were tipped in the magnetic field. Data were taken for crystallographic directions of B0 which completely outlined the unit stereographic triangle. Measurements were also made for many directions in the interior of the unit triangle. Hall effect and transverse-even voltage terms were measured, as well as the transverse magnetoresistance. Results are presented which can be compared to the predictions provided by Fermi surface shape.
Binary Light Beam Deflection in Single Crystal Barium Titanate
Authors: Drake Marvin D. , Joseph Richard I. , Palmer C. Harvey
Published: February 2004

This paper describes a new type of binary electro-optic light beam deflector capable of wide angle deflection. A linearly polarized light beam is deflected by total internal reflection at the boundary of a 90° domain wall wedge in single-crystal barium titanate. The wedge is moved through the crystal by an applied electric field. The crystal is held at a temperature where it is ferroelectric, birefringent, and has tetragonal 4-mm symmetry. The angle of deflection can be set at any angle from 0° to greater than 45°, limited only by the exit aperture of the temperature bath. The electric field required to operate the deflector varies from approximately 200 V/mm at 80°C to less than 50 V/mm at 130°C. It is shown theoretically and experimentally that a threshold field exists for the operation of the beam deflector, and that this threshold field is a function of temperature. The operating frequency of the deflector is limited by heating effects, and the switching risetime is limited by the presence of 180° domain walls. Two possible modes of operation are suggested: (1) continuously operating binary switch, and (2) gated switch.
Nonlinear Interaction Between Circularly Polarized Waves and Electron Plasma Waves
Authors: Kim H. , Harker K. J. , Crawford F. W.
Published: February 2004

This paper presents a general analysis of nonlinear three-wave interaction in a hot magnetoplasma between circularly polarized waves propagating at small angles to the static magnetic field, and electron plasma (Langmuir) waves propagating parallel. First, the coupled mode equations are derived by iterative solution of the Vlasov equation. Simplified expressions for the coupling coefficients are then obtained for all of the wave combinations for which the frequency and wave number synchronism conditions can be satisfied, and the wave coupling coefficients are nonzero. These comprise interactions among three right-hand polarized waves, two circularly polarized waves and one Langmuir wave, and three Langmuir waves. The paper concludes with a brief discussion of the specific cases most likely to be worth subjecting to detailed numerical analysis.
Dislocation Etch Pits in Silver
Authors: Chen C. C. , Hendrickson A. A.
Published: February 2004

A modification of the etchant used by Levinstein and Robinson is shown to be a reliable solution in producing etch pits at dislocations on the (111) surface of silver crystals and is used to investigate the dislocation structures in as-grown, annealed, and deformed silver crystals. Single crystals of silver with dislocation densities on the order of 104 cm−2 with a few subboundaries were prepared by high-temperature annealing. Two distinct sizes of dislocation etch pits are found in both as-grown and deformed crystals. The two sizes of etch pits are concluded to be associated with positive and negative edge dislocations through detailed observations of etch-pit rosettes produced by indentation. The modified Levinstein-Robinson etchant for silver thus corresponds to the Livingston etchant for copper. Additional observations are made on polygonization, dislocation interactions, and etch-pit morphology. Large etch pits not associated with individual dislocations are also described.
Properties of Vacuum-Insulated Single-Crystal Tungsten Electrodes in High Electric Fields. Part I. Surface Structural Changes
Authors: Fabiniak T. J. , Dodd R. A. , Jedynak L.
Published: February 2004

The surface structures of variously oriented single-crystal tungsten electrodes in a vacuum of ∼2×10−5 Torr have been examined after the application of electric fields leading to breakdown. Electron microscope replica techniques were chiefly used. Various surface irregularities were found, including ``splash'' and ``burn'' areas where material was transferred from one electrode to the other, protrusions and depressions, and identical twin or triplet defects of undetermined origin. However, the most interesting defects were characterized as thermal-electrical traces, and they clearly resulted from evaporation of atoms from slip steps. It is tentatively suggested that breakdown may be initiated by that electrode most likely to undergo plastic deformation, and that crystal orientation is important in this connection.
Ultra-Fast Diffusion of Copper in Praseodymium
Authors: Dariel M. P.
Published: February 2004

The serial sectioning method has been used to measure the solute diffusivities of copper in praseodymium. In the bcc phase the diffusivity of copper can be expressed by D=5.7×10−2 exp(−17 800/RT) cm2/sec, and in the double-hcp phase by D=8.4×10−2 exp(−18 100/RT) cm2/sec. It is most likely that copper diffuses in praseodymium by means of the combined substitutional-interstitial mechanism, similar to the other noble-metal solutes. Comparison of the present results with the previously measured diffusivities of zinc indicates that the solute diffusivities increase with decreasing solute valence.
Emission of Radiation from a Modulated Electron Beam
Authors: Marcuse D.
Published: February 2004

Schwarz and Hora have observed emission of radiation from an electron beam that was modulated by laser light in passing through a thin film. The modulated beam radiated at the modulation frequency on entering a dielectric (nonfluorescent) target material. In this paper the mechanism of emission of radiation of a modulated electron beam is studied on the simplified model of a klystron cavity. It is found that one modulated electron alone is incapable of emitting a photon coherently at the modulation frequency. However, the expectation value of the field intensity does show the expected resonance behavior. If the wave functions of n electrons per unit length overlap they contribute coherently to the expectation value of the field intensity. It is thus the collective interaction of many electrons with overlapping wave functions that makes possible the coherent emission of light at the modulation frequency.
Mössbauer Effect in Lithium-Zinc Ferrites
Authors: Young J. W. , Smit J.
Published: February 2004

Mössbauer effect measurements have been made on 57Fe in the lithium-zinc ferrites, ZnxLi0.5 − x/2Fe2.5 − x/2O4, for 0≤x≤1 and at temperatures from 22° to 700°C. The spectra taken at 22° and 330°C are fit by a superposition of components due to ions on tetrahedral sites and on octahedral sites with different numbers of magnetic neighbors. Calculations of the saturation magnetizations based upon the Mössbauer results and the assumption that no significant spin canting occurs are in good agreement with published experimental data. The variation with x of the quadrupole splitting is determined from spectra taken above the Curie temperatures of all samples.
Hot-Electron Faraday Effect in Nonparabolic Semiconductors at Low Temperatures
Authors: Sodha Mahendra S. , Sharma Satish K. , Dubey Prabhat K.
Published: February 2004

This paper presents an analytical investigation of the dependence of Faraday rotation and ellipticity on the heating dc electric field in III-V semiconductors at low temperatures (k0T<ℏωl). The inelastic scattering of electrons by optical phonons in the active region (ε>ℏωl), and the elastic scattering by ionized impurities and acoustic phonons in the passive region (ε<ℏωl), have been considered to be the dominant scattering mechanisms. The anisotropic components of the distribution function and the expressions for Faraday rotation and ellipticity have been obtained in the microwave range of frequencies by solving the Boltzmann transport equation with the appropriate collision term. The analysis has been applied to n-InSb at 77°K. It is seen that the variation of both the Faraday rotation and ellipticity with the heating field is not large in magnitude, and is almost linear over the range of interest. The effect of changes in the wave frequency and electron concentration on Faraday rotation and ellipticity has also been investigated.
Very-Low-Frequency Plasma Oscillations in a Spherical, Magnetized, Cold Cathode Discharge
Authors: Schmidt Pierre , Quinn Robert G.
Published: February 2004

Coherent very-low-frequency (VLF) oscillations in the range 0–30 kHz, due to a plasma transport across magnetic field lines, have been found in a cold cathode dc discharge, where the cathode is a uniformly magnetized sphere. Similar oscillations are found to occur in coaxial cylindrical discharges with a uniform external magnetic field. The frequency of the oscillations decreases with increasing discharge current, decreasing discharge voltage, background gas pressure, magnetic field strength, ion mass, and increasing diameter of the cathode. The oscillations are rich in harmonics. At the lower frequencies the discharge revolves in the equatorial plane of the cathode. A mixing phenomenon is reported in which sum and difference frequencies are obtained between the signals of the device and an external generator. Using probes as diagnostic tools the maximum of the oscillations has been located in the negative glow of the discharge. In addition it is found that two different modes of oscillation exist, the m=0 mode having no phase difference in the angular direction, and the m=1 mode having a phase difference of 2π in the angular direction. A simple theoretical model, based on the assumption that the frequency of oscillation is proportional to the rotation frequency of the plasma, is developed for the m=1 mode of oscillation. Finally the use of the device as a sensitive pressure gauge is suggested.
Photoconductivity in p-Type Silicon Irradiated with 1.2-MeV Electrons at ∼15°K
Authors: Vajda Peter , Cheng L. J.
Published: February 2004

Floating-zone refined (FZ) and pulled (oxygen-rich) p-type silicon crystals have been irradiated at ∼15°K with various doses of 1.2-MeV electrons. For wavelengths from 1.2 to 5.5 μ and temperatures from 23° to 80°K, their photoconductivity spectra have been measured before irradiation, after irradiation and after isochronal anneals up to 400°K. The 3.9-μ photoconductivity band appears immediately after irradiation in all crystals already at low temperatures, giving further evidence that it is due to the divacancy formed directly during irradiation by electrons. Three main annealing stages of the photoconductivity have been found: (a) below ∼150°K, (b) 160°–280°K and (c) 280°–360°K. Stage (a) is thought to be due to charge redistribution among some levels. A radiation-induced deep level at Ev+ (0.12±0.02) eV anneals out in stage (b) and is thought to be related to the neutral vacancy in some way. The third stage is attributed to the breaking up of vacancy-impurity complexes. The electrical conductivity, measured simultaneously with the photoconductivity, exhibits a large stage (b) and a small stage (c). The annealing behavior of the spectra and the conductivity depends strongly on the measuring temperature. The dependence of the spectra on chopper speed was also investigated. The dependence of Δσ in the low-temperature range (⪝45°K) can be explained by the existence of a shallow α-type trapping level, which is likely the dopant level.
Small-Signal Transient Double Injection in Semiconductors Heavily Doped with Deep Traps
Authors: Weber Willes H. , Elliott R. S. , Cederquist A. L.
Published: February 2004

The small signal transient response is discussed for double-injection diodes operating in the low injection square-law regime. This regime occurs, preceding the negative resistance regime, in long structures heavily doped with deep recombination centers. An expression is derived for the ac impedance, and the result is characterized by a simple equivalent circuit. The theory predicts that two distinct decay modes with different time constants, one each for electrons and holes, should be observed in the transient response. Experimental results for Au-doped Si p-i-n diodes with three different doping concentrations are presented. These show generally good agreement with the theory. In particular the time constants and the relative magnitudes of the two decay modes observed in p-type Si slightly overcompensated with Au agree well with those calculated using known values for the capture coefficients and mobilities.
Influence of Size Effect on Low-Temperature Electrical Resistivity
Authors: Ehrlich Alexander C.
Published: February 2004

The low-temperature electrical resistivity in thin plates has been theoretically examined. It is shown that the bulk relaxation time τi is a reasonable approximation to describe the impurity scattering. In constrast, the low-temperature phonon-electron interaction is not properly described by the bulk thermal relaxation time τp. Nevertheless, expressions have been obtained for the Fermi function in thin plates correct to first order in τi/τp≪1. The predicted temperature-dependent resistivity obtained is smaller than the results predicted by Fuchs, which are also given explicitly in this limit for the first time. In the limit of very low temperatures and very thin plates a temperature dependence of resistivity greater than the bulk value, but ⅔ that obtained by Fuchs, is predicted. These results are discussed.
Nonlinear Behavior of Transverse-Wave Amplifiers
Authors: Briggs R. J.
Published: February 2004

The nonlinear behavior of traveling-wave amplifiers using transverse interaction modes (cyclotron and synchronous beam waves) is analyzed theoretically. An analytical solution for the circuit field amplitude as a function of distance is derived, under the assumption of a relatively slow growth per wavelength. Detailed calculations of the saturation characteristics (output power versus input power) are presented for several cases, and it is shown how the electronic efficiency can be improved by operating at a beam voltage above the synchronous voltage.
Generalized Plane Waves and Waveguide Modes in a Moving Isotropic Medium
Authors: Aalund Mogens , Johannsen Günther
Published: February 2004

The Lorentz transformation of plane-wave-like solutions and general waveguide modes is analyzed. A propagation and attenuation tensor is introduced. General Doppler equations and invariant phase quantities are shown to be simple consequences of the formalism. The concept of dispersion is discussed and a covariant condition connected with this concept is given. Covariant wave equations and dispersion relations are derived in a simple manner. The dispersion relations are used to analyze some special waveguide solutions including cutoff phenomena.
Faraday Rotation in Artificial Dielectrics
Authors: Srivastava G. P. , Mathur P. C. , Kumar Arun
Published: February 2004

The contribution to Faraday rotation in artificial dielectrics, arising due to complex nature of the permittivity of the semiconductor particles embedded in an artificial dielectric, is estimated theoretically on the basis of Lewin's expressions of permeability and permittivity for artificial dielectrics. On the basis of the above analysis the contribution to rotation is found to be appreciable, whereas Nag and Engineer and other previous workers considered it to be negligibly small.
Decrease in Spontaneous Emission at the Onset of Lasing in Semiconductors
Authors: Nicoll F. H.
Published: February 2004

It has been shown experimentally that spontaneous emission in semiconductors decreases at the onset of lasing. This has been observed qualitatively by a visual method in CdS and GaAs lasing in a total internal-reflection cavity under electron-beam pumping. More quantitative observations have been made on CdSe and CdS optically pumped by a HeNe laser and Argon laser, respectively. The decrease in spontaneous emission occurs across the entire spectrum. It seems reasonable to believe that this decrease also occurs in Fabry-Perot cavities. No explanation for the new phenomenon has been found and it seems to be inconsistent with earlier published theory suggesting that the spontaneous emission should saturate after lasing sets in.
Flux-Flow Effect in Josephson Tunnel Junctions
Authors: Barone A.
Published: February 2004

Experimental results exhibiting the displaced linear slope effect in the volt-ampere characteristics of large Josephson junctions are reported. These data substantially confirm theoretical predictions based on the effect of magnetic flux flow.
Electroluminescence and Electrical Properties of High-Purity Vapor-Grown GaP
Authors: Craford M. G. , Groves W. O. , Herzog A. H. , Hill D. E.
Published: February 2004

The electroluminescence, Hall coefficient, and resistivity of high-purity GaP, grown by means of vaporphase epitaxy on bulk single-crystal GaP substrates, have been studied as functions of temperature. Hall mobilities as high as 2730 and 189 cm2/V sec have been obtained at 77° and 300°K, respectively. The electroluminescence (EL) of diodes fabricated by Zn diffusion exhibits intrinsic recombination. At 77°K, in addition to the narrow no-phonon line due to bound exciton recombination at a neutral donor site, the near-band-edge EL exhibits a well-defined series of peaks corresponding to the phonon-assisted recombination of free excitons. Peaks are observed associated with both the absorption and emission of TA, LA, and TO phonons with energies of 12.5, 31.0, and 44.0 meV, respectively. The intensities of the peaks associated with phonon emission have the approximate ratio 1:3:1.5 for the TO, LA, and TA phonons, respectively. These energies and relative intensities are in good agreement with absorption and cathodoluminescence data for intrinsic GaP. The temperature dependence of the electroluminescence demonstrates that in these devices, which have a low concentration of nitrogen and other unintentional impurities, the 300°K emission is dominated by intrinsic recombination.
Edge Emission Bands in High-Purity Cadmium Sulfide
Authors: Greene Lawrence C. , Wilson Henry A.
Published: February 2004

It is shown that there are nine clearly defined series of low-temperature phonon-assisted edge emission bands in pure cadmium sulfide crystals. Of these nine series, four have not been previously discussed. It is shown that eight of the series can be explained as arising from transitions involving a band model with two donor levels and three acceptor levels.
Effect of Torsion on Magnetostrictive Delay Lines
Authors: Bernini U.
Published: February 2004

In this study a method is suggested for the simultaneous production of two different stress pulses in a magnetostrictive material. The magnetostrictive effect for a wire subjected exclusively to a longitudinal tension is introduced and the study extended to the case where the material is also twisted. It is shown that when the twisted wire is excited by a longitudinal magnetic field, because of the easy magnetization axis skew, it is possible to obtain not only the simultaneous production of extensional and torsional pulses, but also the production of a pulsed emf at the ends of the wire. Finally, a possible application of the phenomenon is shown to the study of second-order elastic effects in magnetostrictive materials.
Static and Dynamic Experiments on the Stretch and Frequency Dependence of Elastic and Viscoelastic Coefficients of Latex Tubes
Authors: Klip Willem , van Loon Pieter , Klip Dorothea A.
Published: February 2004

Assuming for the wall material (supposed incompressible) of a latex tube a strain-energy function of the form W = ½Φ (I1−3) +½Ψ (I2−3), (Φ and Ψ constants, i.e., independent of the deformation) a stress-strain relationship for simple stretch, an equation of motion for small torsional vibrations, and a frequency equation for torsional waves of small amplitude are derived. In the equations of motion Φ and Ψ are replaced by Voigt operators Φ+Φvi (∂/∂t) and Ψ+Ψvi (∂/∂t). Experiments with simple large-stretch free torsional oscillations of small amplitude and torsional waves of small amplitude superposed on a large stretch showed that the postulates predict the behavior adequately. Φ and Ψ were found to be not only independent of the stretch (1≤λ≤2.3) but also independent of the frequency (0≤f≤33 cps). ωΦvi and ωΨvi appeared at the lower frequencies (free vibrations) to be independent of the stretch and of the frequency. At the higher frequencies a frequency and stretch dependence could not with certainty be detected. The importance of this phenomenon for the study of the arterial system, where waves of small amplitude superposed on a large deformation occur is briefly discussed.
Recombination Lifetimes in Gold-Doped p-Type Silicon
Authors: Wenaas E. P. , Leadon R. E. , Naber J. A. , Mallon C. E.
Published: February 2004

Transient recombination lifetimes have been measured in gold-doped p-type silicon from 30°K to room temperature. Photoconductive decay curves and quiescent electrical conductivity have been obtained with the microwave reflection technique. The presence of a controlled amount of gold permits unambiguous determination of attractive and neutral capture cross sections which are compared with theoretical values obtained by Lax and with other experimental values. An unusual feature of the data is a dramatic drop in excess conductivity at temperatures below 50°K. The observed variations of lifetimes with temperature and the drop in excess conductivity are explained using a transient analysis similar to that of Sandiford and Wertheim.
Ultralow Gas Concentration Infrared Absorption Spectroscopy
Authors: Kreuzer L. B.
Published: February 2004

A new technique is presented for obtaining the absorption spectra of small samples and low concentrations of gases. The technique makes use of currently available sources of wavelength-tunable intense coherent light such as the optical parametric oscillator, dye laser, or tunable diode laser. The absorbed power is detected by the heating and resultant pressure rise in the absorbing gas. An initial experiment with a 15-mW He–Ne laser operating at 3.39 μ has shown a sensitivity adequate to measure the absorption of a concentration of 10−8 of methane in nitrogen. It is expected that, with higher-power sources of tunable ir radiation, it may be possible in the future to detect concentrations of impurities as low as 10−13.
Measurement of Free-Carrier Lifetimes in GaP by Photoinduced Modulation of Infrared Absorption
Authors: Afromowitz Martin A. , DiDomenico M.
Published: February 2004

A new technique is presented for measuring the lifetimes of both minority and majority photoexcited free carriers in GaP. The technique is useful for both n- and p- type material in any doping range and involves measurement of the modulation of the free-carrier infrared absorption induced by photoexcited free carriers. In GaP(Zn, O) we find that the minority-carrier (electron) lifetime ranges from 1 to 20 nsec, and the majority-carrier (hole) lifetime ranges from 0.1 to 2 μ sec. A saturation effect is observed which is consistent with the view that the dominant recombination path in GaP(Zn, O) is through a deep acceptor via an Auger mechanism.
Power-Flow Theorem for Acoustic Waves in Piezoelectric Semiconductors
Authors: Kak A. C.
Published: February 2004

A power-flow theorem which clearly brings out the contribution of various mechanisms to power flow, stored energy, and power dissipation has been derived for acoustic waves in piezoelectric semiconductors. A major feature of the theorem is that it holds for any direction of propagation of acoustic wave with respect to the direction of dc drift velocity of the carriers. Therefore, it is expected to be useful in understanding the effect of bulk-wave radiation on the performance of surface-wave interdigital transducers on piezoelectric semiconductors, such as in surface-wave amplifiers and unidirectional delay lines, where the bulk waves launched are at an angle to the drifting carriers.
Elastic Moduli and Thermal Expansion of Lutetium Single Crystals from 4.2 to 300°K
Authors: Tonnies J. J. , Gschneidner K. A. , Spedding F. H.
Published: February 2004

The adiabatic elastic moduli of hexagonal close-packed lutetium single crystals have been determined by the ultrasonic pulse superposition technique over the temperature range 4.2–300°K. The values at 300°K in units of 1011 dyn/cm2 are C11=8.62, C33=8.09, C44=2.68, C66=2.71, and C13=2.8; the values extrapolated to 0°K are C11=9.10, C33=8.40, C44=2.91, C66=2.96, and C13=2.9. The Debye temperature calculated using the elastic moduli at 0°K is 184.5°K. The bulk elastic properties have also been calculated and they agree favorably with previously predicted polycrystalline values. The linear thermal-expansion coefficients of the lutetium single crystals have been determined over the same temperature range by using a linear-variable-differential-transformer dilatometer. The room-temperature coefficients of thermal expansion are α∥=2.0×10−6 and α⊥=4.82×10−6°K−1. A maximum in α⊥ was found at 130°K, which apparently correlates with the maximum found in the γ⊥/γ∥ ratio at 130°K, where γ is the Grüneisen constant.
Annealing of Electron-Irradiated n-Type Silicon: Illumination and Fluence Dependence
Authors: Kimerling L. C. , Carnes C. P.
Published: February 2004

The effects of strong illumination and radiation fluence on the annealing behavior of the E center in electron-irradiated phosphorus-doped float-zoned silicon were studied by Hall-effect measurement. Illumination of the sample during anneal increased the rate of recovery significantly. Increasing the radiation fluence and, hence, the level of the induced-carrier compensation, also increased the rate of anneal. These results were found to be consistent with a previously proposed model in which the charge state of the defect was found to be a major determinant of the activation energy of recovery.
Radiation-Induced Precipitation in Silicon During High-Voltage Electron Microscope Observation
Authors: Nes E. , Washburn J.
Published: February 2004

Two modes of electron-beam radiation-induced precipitation have been observed in high-purity Lopex (low-oxygen dislocation-free silicon). (i) At room temperature a whiskerlike precipitate structure developed along the dislocation lines. (ii) During hot stage observations long needle-shaped precipitates oriented in 〈110〉 directions were formed.
Electromagnetic Scattering from an Inhomogeneous, Collisionless Plasma Cylinder
Authors: Neuringer Joseph L. , Stekert James J.
Published: February 2004

An analytical investigation is presented of the coherent electromagnetic scattering at normal incidence from a quiescent, infinitely long, radially inhomogeneous, collisionless plasma cylinder. The inhomogeneity is characterized by an index of refraction n = [1 − (α/r)]½ such as would result from a line plasma source issuing plasma at a constant flow rate. Exact scattering solutions are obtained for both transverse electric and transverse magnetic polarizations of an incident plane wave. With k0 and a representing the free-space wavenumber and cylinder radius, respectively, the partial radial wavefunctions and the scattered field are shown to depend markedly on the two nondimensional parameters β and η, where β = k0a and η = k0α. Numerical calculations of the differential scattering cross section for the TM mode show that forward scattering increases sharply with either increasing β or η although the increase is most sensitive to variations in β. The total scattering cross section is also shown to increase monotonically in the same fashion. Finally, it is observed that the scattering efficiency factor asymptotically approaches 2 in the limit as β and η both approach infinity, which is the same as that obtained for the homogeneous cylinder in the limit as β approaches infinity.
Pair Distribution Function of a One-Dimensional Hard Rod Gas
Authors: Flicker Michael
Published: February 2004

The pair distribution function D2(x1, x2) for an infinite system of one-dimensional hard rods, each of length d, is derived directly from the expression for a finite system. In addition, for a finite system of N rods, it is shown that D2(x1, x2) is constant in the region of translational invariance if |x2 − x1| ≥ (N − 1)d. A relationship between D2(x1, x2) and D1(x) is also discussed.
Invariants and Scalars of Compact Inhomogeneous Unitary Algebras
Authors: Mirman Ronald
Published: February 2004

The independent invariants of the fundamental and adjoint inhomogeneous algebras are explicitly constructed. Some classification of inhomogeneous algebras is given and their scalars and invariants are discussed.
Number of Polynomial Invariants of Adjoint and Fundamental Compact Inhomogeneous Unitary Algebras
Authors: Mirman Ronald
Published: February 2004

The number of invariants for two types of inhomogeneous Lie algebras is computed.
n-Particle Kinematics
Authors: Roffman Eric H.
Published: February 2004

We suggest a very simple method for handling relativistic n-body kinematics. In fact the method works well for studying the n-fold Kronecker products of the representations of many groups, including all compact Lie groups as a simple case. The method is explicitly covariant, and treats all particles symmetrically.
Gauge Fields with Noninvariant Interactions
Authors: Fitzgerald R. , Schiminovich S.
Published: February 2004

Gauge fields interacting with source fields in a gauge-noninvariant way are examined in a purely classical framework. The existence of conserved currents for the solutions of such theories follows from the properties of the free gauge fields rather than from the usual requirement of global gauge covariance. One of the simplest gauge-noninvariant theories of electromagnetism is shown to be an extension of Dirac's theory of classical clouds of charge. In this extension the clouds exhibit some quantum features. Gauge-noninvariant interactions for Einstein's theory of gravitation are presented in which the properties of the sources are carried by the metric field. In the case of the Yang-Mills field, internal symmetries for a real scalar source field are a consequence of the properties of the gauge field.
Green's Functions for the One-Speed Transport Equation in Spherical Geometry
Authors: Erdmann R. C. , Siewert C. E.
Published: February 2004

Several problems in one-speed neutron transport theory for spherically symmetrical systems are discussed. The singular eigenfunction expansion technique is used to construct a solution for a specific finite-slab Green's function. This slab solution is then used to construct the finite-medium spherical Green's function by extending the point-to-plane transformation concept. For the general case, the expansion coefficients are shown to obey a Fredholm equation, and first-order solutions are obtained; however, in the infinite-medium limit the solution is represented in closed form. In addition, the solution for the angular density in an infinite-medium due to an isotropic point source is developed directly from the set of normal modes of the transport equation. A proof that the result so obtained obeys the proper source condition at the origin is given.
TCP Invariance and the Dimensionality of Space-Time
Authors: Rosen S. P.
Published: February 2004

The original proofs of the TCP theorem suggest that it may breakdown in an odd-dimensional space-time. An explicit example of this breakdown is given and a comment is made about the current × current interaction.
Null and Pseudonull Data for Scalar Fields
Authors: Grgin Emile
Published: February 2004

In this paper, a projective geometric formalism for the description of the conformal compactification of Minkowski space and of its invariance groups is developed. It is then modified to include the description of Minkowskian vectors, in particular, the momentum space. The d'Alembert equation is solved by constructing its solutions from global null data, completely arbitrary numbers assigned to the null cone at infinity. The Klein-Gordon equation, solved by the same method, leads to the concept of pseudonull data. Pseudonull data are also arbitrary numbers, but they are assigned to hyperboloids at a suitably defined infinity outside the conformal compactification of the Minkowski space.
Unitary Irreducible Representations of SU(2, 2). II
Authors: Yao Tsu
Published: February 2004

Paper II of this series [Paper I in J. Math. Phys. 8, 1931 (1967)] is concerned with a general study of the degenerate representations. The explicit expressions for the ``raising'' and ``lowering'' functions ai2(p,q,λ), and bi2(p,q,λ), i = 1, 2, 3, 4 are found. The three Casimir operators C2, C3, and C4 depend on only two complex parameters A and B, a fact reflecting the degenerate nature of the representations under study here. The finite representations are studied first, and thus provide a proof for the degenerate part of Theorem 2, Paper I. The unitary representations are studied next, and we find that there are fourteen classes of degenerate unitary irreducible representations. There are two continuous series, ten discrete series, and two series which depend on one discrete and one continuous parameter. The degenerate part of the D± series is studied, and thus provides an explicit demonstration of Harish-Chandra's theorem.
Multiplicity Problem for Compact Subgroups of Noncompact Groups
Authors: Klink William H.
Published: February 2004

A method is shown for calculating the multiplicities occurring in the reduction of a reducible representation of a compact group. The reducible representation is obtained by constructing induced irreducible representations of a noncompact group and then restricting the elements of this representation to elements of the compact subgroup.
Stationary Electromagnetic Fields in General Relativity
Authors: Datta B. K. , Raychaudhuri A. K.
Published: February 2004

The paper presents some solutions of the Einstein-Maxwell equations corresponding to a superposed electric and magnetic field at right angles to each other. The solutions are stationary and include the case of null field also. There are, however, some singularities in the metric tensor.
Principle of Compensation of Dangerous Diagrams for Boson Systems. I. Maximum Overlap
Authors: Kobe Donald H.
Published: February 2004

The principle of compensation of dangerous diagrams (PCDD), used by Bogoliubov to determine the coefficients in the canonical transformation to quasiparticles in boson systems, is obtained by maximizing the overlap between the true ground-state vector and the quasiparticle vacuum state. The zero-momentum state is treated exactly, which implies that the sum of all diagrams leading from the vacuum to a one-quasiparticle state must be zero, in addition to the diagrams leading from the vacuum to the two quasiparticle state. Other criteria, such as the diagonalization of the quasiparticle reaction operator up to terms cubic in the operators, and the absence of one and two quasiparticle contributions to the true ground-state wavefunction, are also shown to lead to the PCDD. A generalization of the Hartree procedure of minimizing the ground-state energy is obtained by replacing the bare quasiparticle interaction with the quasiparticle reaction operator, and is shown to be equivalent to the PCDD. Finally, a perturbation expansion of the PCDD is obtained, and the reducibility of diagrams is discussed.
Invariants in the Motion of a Charged Particle in a Spatially Modulated Magnetic Field
Authors: Dunnett D. A. , Laing E. W. , Taylor J. B.
Published: February 2004

In this paper we study the effect of a spatial modulation in the magnetic field on invariants such as the magnetic moment μ=V⊥2/B. In particular, we investigate whether an invariant still exists when the wavelength of the modulation is comparable to the gyro radius of the particle. In an axially symmetric magnetic field, with a square-wave modulation, the orbit equations reduce to algebraic relations convenient for numerical study. We find from such studies that orbits are of two types: (a) regular orbits which generate an invariant; (b) orbits which are quasi-ergodic. We have also calculated an invariant by perturbation theory with the depth of modulation of the field as a small parameter. For this we developed a modified form of perturbation theory which overcomes the difficulty of infinities arising at resonance between the perturbation and the cyclotron period. This difficulty in fact corresponds to a change in topology of the invariant curves. The invariant calculated from this theory shows very good agreement with the numerically computed orbits of type (a). The transition to quasi-ergodic behavior cannot be predicted analytically, but some indication of it may exist in the complex topology of the invariant curves in the ergodic regions.
Local Field Theory and Isospin Invariance. II. Free Field Theory of Arbitrary Spin Particles
Authors: Carruthers P.
Published: February 2004

The properties of free field theories of arbitrary spin and isospin particles are investigated. Self-conjugate isofermion (I = ½, 32, 52, ⋯) field theories of arbitrary spin S are shown to be nonlocal, with commutators (or anticommutators) failing to vanish outside the light cone. Special attention is given to discrete transformations ℭ, ℑ, and 𝔖. For self-conjugate multiplets the parity, charge conjugation, and time-reversal phase factors ηC, ηP, ηT are not arbitrary but obey ηP2=(−1)2S, ηC2=(−1)2Iηα2, ηT2=(ηα*)2, where the phase ηα = ξ(−1)I+α (|ξ| = 1, α = −I, ⋯, +I) arises when the complex-conjugate representations of SU(2) are transformed to the standard basis. Composite products of ℭ, ℑ, and 𝔖 are discussed, with general phases and attention to the dependence on order of the operators. The six possible ℭℑ𝔖 operations Θi are analyzed. For pair-conjugate multiplets, the operator Θi2 is, in general, a gauge transformation, with phase (ωi*)2 depending on the ℭ, ℑ, 𝔖 phases and the order in which ℭ, ℑ, and 𝔖 enter into Θi. By postulating that Θi2ψΘi−2 be independent of the order of ℭ, ℑ, and 𝔖, we derive the Yang-Tiomno parity factors (±1, ±i) for pair-conjugate fermions. For self-conjugate multiplets, however, the phase restrictions previously stated lead to a unique order-independent result Θ2ψΘ−2=(−1)2I+2Sψ. The usual local field theory result lacks the factor (−1)2I. The latter differs from unity only for the case 2I = odd integer, in which case we are in fact dealing with a nonlocal field theory. The technical details of the theory involve construction of local fields from helicity wavefunctions and helicity particle operators. Fields of spin greater than one are described by the Rarita-Schwinger formalism. An appendix treats in detail the form and properties of the high-spin wavefunctions in the helicity basis.
Diffusion Length and Criticality Problems in Two- and Three-Dimensional, One-Speed Neutron Transport Theory. I. Rectangular Coordinates
Authors: Williams M. M. R.
Published: February 2004

Several problems in linear transport theory have been solved involving more than one dimension. We have considered the diffusion-length problem in a slab system and have studied how the flux in the transverse direction varies as a function of distance from the source. The solution is found to consist of an asymptotic term, composed of a finite number of harmonics, plus a transient which is nonseparable in the x and z coordinates. When the slab is sufficiently thin only the transient term survives and the concept of a diffusion length loses its value. A method for overcoming this difficulty is presented. In another problem, the thickness of the slab is allowed to become semi-infinite and the effect of decay in the z direction on the emergent angular distribution and surface flux are assessed. By approximating the flux in the y and z directions by a function of the form exp {iByy + iBzz} and solving the resulting one-dimensional problem in the x direction exactly, it has been possible to obtain a statement of the critical conditions in a bare rectangular parallelepiped system. The application of this method to the diffusion length problem in a system with a rectangular cross section is discussed. Finally, by comparison with the exact solution for the slab, we estimate the accuracy of a reduced Boltzmann equation deduced by the author in a previous publication.
Derivation of Nonrelativistic Sum Rules from the Causality Condition of Wigner and Van Kampen
Authors: Chadan K. , Montes A.
Published: February 2004

Nonrelativistic sum rules previously obtained for each phase shift in the framework of elastic scattering by a local central potential of finite radius are shown to follow from the causality principle of Wigner and Van Kampen, under the assumptions that the phase shift satisfies the Levinson theorem and that, at high energies, the integrability condition holds. In fact, it is shown that under these assumptions, any interaction of finite radius which is causal in the sense of Wigner and Van Kampen is equivalent to a local potential of the same radius. First we recall the sum rules and mention some of their applications. We give a brief survey of their proof in potential scattering, which is based essentially on the analytic and asymptotic properties of the Jost function (or the S matrix). Then we show that, under the assumptions mentioned above on the phase shifts, the properties of the R matrix derived by Wigner and Van Kampen from causality lead to the same analytic and asymptotic properties of the Jost function (defined now directly from the S matrix) as in potential scattering, providing, therefore, sufficient information for the direct derivation of the sum rules. Finally, using the Gel'fand-Levitan and Marchenko integral equations of the inverse-scattering problem, we show that, in fact, this information is sufficient to entail that the causal interaction of Wigner and Van Kampen is equivalent to a local potential of the same radius.
Asymptotic Behavior of Certain Nonlinear Boundary-Value Problems
Authors: Canosa José , Cole Julian
Published: February 2004

The asymptotic properties of a class of nonlinear boundary-value problems are studied. For large values of a parameter, the differential equation is of the singular-perturbation type, and its solution is constructed by means of matched asymptotic expansions. In two special cases, very simple approximate analytic solutions are obtained, and their accuracy is illustrated by showing their good agreement with the exact numerical solution of the problem.
Approach to the Three-Body Scattering Problem
Authors: Jasperse J. R.
Published: February 2004

We derive some new equations for the wavefunction for the three-body scattering problem using the ``partial-wavefunction approach.'' All scattering processes are solutions of inhomogeneous coupled integral equations for the scattered parts of the total wavefunction. We show how the Pauli principle is incorporated when some or all of the particles are identical. This leads to a reduction in the number of independent scattered partial wavefunctions when some of the particles are identical. The kernels in the integral equations contain no δ functions but each scattered partial wavefunction does have a self-coupling term. We apply the method to the scattering of three identical bosons interacting through zero-range pair potentials. The method gives the same equation for this problem as obtained by the Faddeev T-matrix approach.
Representation Functions for the Degenerate Baryon Series in U(6)⊗U(6)
Authors: Delbourgo R.
Published: February 2004

The most degenerate class of representation functions dW,W′NB(θ) pertaining to U(6)⊗U(6) have been calculated for arbitrary quark number N with the baryon number B, and W, W′ weights of the U(6)W subgroup assuming the following values: B = 0, ⅓, ⅔, 1; [W], [W′] = 1, 6, 21, 56. These functions are the matrix elements of the rotation operator exp (−iΘJ2) between basis vectors of the degenerate U(6)⊗U(6) Feynman series (characterized entirely by BNW labels), and are essential to the generalized Reggeization program.
Cell Model of a Fluid. II. Thermodynamic Properties of the System
Authors: Tross Ralph G. , Lund Louis H.
Published: February 2004

In Paper I of this series (preceding paper) the model was formulated mathematically and the solution derived in the form of an infinite series. The convergence and analyticity of the solution were investigated. It was then applied to one-, two-, and three-dimensional systems with nearest-neighbor interactions, and low-temperature series for these systems were obtained. In the present article the thermodynamics of the model are investigated. The series solution of the partition function derived in Paper I is applied to systems with interaction potentials of increasing complexity. The validity of the model is established by showing that in the appropriate limits it leads correctly to the ideal gas and the Tonks equation of state. It is shown that the model is capable of portraying phase transitions and gives realistic results thermodynamically. Finally various finite one-, two-, and three-dimensional systems are analyzed numerically by high-speed computer and their thermodynamic properties and pair-correlation functions are examined. Interesting conclusions emerge concerning the range of order in such systems and the probable critical temperatures.