bluuebunny/crossref_metadata_2025_split huggingface dataset:
Concentration Correlations, Velocity Correlations, and Transport Noise in Quasineutral Semiconductors
Authors: Sergiescu V. 
Published: July 2007

AbstractThe non‐local decomposition of the transport noise formerly introduced by the author is performed for a quasineutral semiconductor. The Hill‐van Vliet formula for the current noise is rederived, the Nyquist formula for the thermal noise is found to be approximately valid in the stationary regime, and the coupling noise is found to be negligible because of the statistical reversibility. The noise effects of the Coulomb and delta correlations are comparable, but opposite, in the most interesting cases.
Electron Energy Loss and F‐Centre Production in KCl and KBr
Authors: Choudhury A. , Goswami K. , Chaudhuri S. 
Published: July 2007

AbstractA rotating cylindrical crystal of KCl was bombarded by 19 keV electrons, and the F‐centre distribution observed as a function of the angle of rotation. Eight maxima were found corresponding to different angular positions of the crystal. The depth of coloration was measured along the <100> and <110> axes in KCl and KBr crystals. In both the crystals the magnitude of coloration was higher along <110> axes than along <100> axes, but the depth of coloration or the electron range had been found to be longer along the latter direction. The results are interpreted in terms of channeling effect.
On the Faraday and Voigt Effects in Anisotropic Materials
Authors: Saleh N. , Zukotynski S. 
Published: July 2007

AbstractThe Faraday rotation and ellipticity and the Voigt effect in degenerate semiconductors possessing ellipsoidal energy surfaces are analyzed. It is shown that if the experimental procedure is chosen properly, information on the effective mass and relaxation time tensors can be readily obtained.
Inductions and Echoes in Systems with Unequidistant Spectrum
Authors: Nagibarov V. R. , Solovarov N. K. 
Published: July 2007

AbstractA general method is developed of calculation of response signals of N‐particle systems with an unequidistant spectrum to pulse action of coherent physical fields resonant for any transition of the system. The case of a particle system where each particle has three energy levels E1 < E2 < E3 is analysed. It is shown that if such a system is subjected to pulse action of two generators exciting transitions E1 ⟷ E2 and E2 ⟷ E3 at initial time and at time τ to pulse action of a generator with frequency ω31 = h−1 (E3 — E1), the system generates induction and echo signals with power proportional to N2 at all possible transitions. Echo signals arise at times (1 + ϵ) τ, 2 τ, and (1 + 1/ϵ) τ after the first pulse, where ϵ = E2 — E1/E3 — E2. The observed responses may have a physical nature which is both identical with the excitation and different from it. Supplements are given by which the responses of particle systems may be calculated to a series of pulses different from those considered here. When ϵ →1 the results transform to the case of equidistant spectrum.
Scattering of Fast Charged Particles on Crystals
Authors: Ryabov V. A. 
Published: July 2007

AbstractThe angular distribution of fast charged particles scattered on a perfect crystal is studied. By introducing the many‐particle correlation functions the velocity distribution function convenient for numerical analysis is obtained. It is shown that this distribution depends essentially on correlations between the thermal atomic displacements of a lattice. A two‐particle model is considered as a particular case, which results are compared with experimental data. It is evident that even in this simplest case the axial symmetry of the scattering yield is disturbed. This is determined by the difference of the various correlation tensor's components as found.
The Defect Structure of Non‐Stoichiometric Germanium Telluride from Magnetic Susceptibility Measurements
Authors: Lewis J. E. 
Published: July 2007

AbstractThe room temperature magnetic susceptibility of non‐stoichiometric GeTe has been measured; by calculating the contributions of the free carriers and the ionic lattice using the appropriate formulae and the known parameters of the system, the contribution to the susceptibility of the lattice defects has been obtained as a function of composition. Analysis of this lattice defect susceptibility shows that vacancy and anti‐structure defects are predominant in the non‐stoichiometric lattice and that their density is extremely high.
A Simple Straight‐Forward Method to Calculate the Correlation Factor and Its Relation to the Isotope Effect for Impurity Diffusion
Authors: Bakker H. 
Published: July 2007

AbstractA general formalism is developed by which it is possible to relate the correlation factor to the isotope effect and to calculate the correlation factor for impurity diffusion by monovacancies in systems having at least a twofold symmetry around the vacancy–solute jump direction. However, the formalism can be extended to more complicated systems. Some well known results are deduced easily from a general equation. The case of impurity diffusion in the two‐dimensional hexagonal lattice and in the three‐dimensional f.c.c. lattice is worked out completely.
Many‐Beam Diffraction Effects in Gold and Measurement of Absorption Parameters by Fitting Computer‐Graphs
Authors: Steeds J. W. 
Published: July 2007

AbstractA computer simulation of electron micrographs has been described previously (Spring and Steeds [1]). The method is here applied to the case of gold where many‐beam effects become important. Measurement of the absorption parameters are made at 600 and 100 keV for the hhh systematics and compared with predicted values. The comparison of computer simulated and experimental bend contours shows agreement only when the atomic scattering potential is also carefully chosen. A simple classification of bend contours is made using both cross‐hatching effects and also central channelling and realised theoretically through analytic four‐beam theory. The change of channelling properties with accelerating voltage is discussed.
EPR of Fe3+ Ions in Chrysoberyl
Authors: Barry W. R. , Troup G. J. 
Published: July 2007

AbstractA redetermination of the spin Hamiltonian parameters for Fe3+ ions substituting for Al3+ ions in mirror symmetry sites in the orthorhombic mineral chrysoberyl (Al2BeO4) has been made. EPR experiments at X‐ and Q‐band frequencies are described, and analysis of the measurements yields new values for the parameters, given by g = 2.003 ± 0.001, b = (8.572 ± 0.006) GHz, b = (–0.311 ± 0.003) GHz, b = = (0.014 ± 0.015) GHz, b = (1.461 ± 0.006) GHz. The zero‐field splittings between the ± 5/2 and ± 3/2, and the ± 3/2 and ± 1/2 Kramers' doublets are (32.78 ± 0.03) GHz and (19.6 ± 0.2) GHz, respectively.
Diffusion and Thermal Conversion of Crowdions
Authors: Seeger A. 
Published: July 2007

AbstractThompson and Buck have demonstrated by internal friction measurements that self‐interstitials in copper may exist in two configurations, a stable and a metastable one. The metastable configuration may be converted by thermal fluctuations into the stable configuration. The present paper develops a simple model for dislocation pinning by crowdions, taking into account thermal conversion. The results clearly indicate that the metastable interstitial in Cu migrates in one dimension, i.e., that it is a crowdion. The temperature dependence of the pinning rate is accounted for by a conversion energy barrier that is in agreement with other data.
Three‐Dimensional versus Crowdion Migration of Interstitials in Annealing Stage I of Irradiated Metals
Authors: Schilling W. , Schroeder K. , Wollenberger H. 
Published: July 2007

AbstractFormulas for the defect production rates are derived for the case that interstitials are highly mobile at the irradiation temperature thereby either recombining with vacancies or being trapped at impurities. Both the migration of interstitials in three dimensions and the linear migration of crowdions are considered. For the crowdion model the possibility of thermal conversion is included. Experimental observations of the defect production rates in f.c.c. metals at temperatures above stage I confirm qualitatively and quantitatively all the predictions of the model which assumes three‐dimensional interstitial migration. The predictions of the crowdion model are by orders of magnitude in disagreement with the experimental results. Especially the very specific dependence of the defect production rates on the impurity concentration and irradiation temperature predicted by the crowdion model is not observed. In the Appendix the interpretation of the dislocation pinning experiments in terms of the crowdion model is criticized.
New Evidence for F′‐Type and Ionized F‐Aggregate Centres
Authors: Nosenzo L. , Reguzzoni E. , Samoggia G. 
Published: July 2007

AbstractIf the ionization probability of an optically excited defect is varied periodically by means of an external electric field of frequency v, a corresponding modulation in the absorption coefficient in the bands associated either with the neutral centre or with the ionized and F'‐type centres can be achieved. In fact the results obtained on M‐ and R‐centres in KCl and KBr crystals at liquid nitrogen temperature give new evidence of the existence of absorption bands associated with M+‐, R+‐, M'‐, and R'‐centres. A new set of absorption bands has been observed associated with ionized R‐centres and ascribed to electronic transitions to different excited states. These bands are located at 0.94, 0.76, 0.54, and 0.49 μm in KCl and at 1.01 and 0.89 μm in KBr. Besides the bands due to ionized N1‐centres, an absorption band has been observed in the infrared, which has been tentatively attributed to N1‐centres.
The Electrical Properties of Chromium Tribromide
Authors: Kanazawa K. K. , Street G. B. 
Published: July 2007

AbstractThe electrical properties of vapor grown crystals of the hexagonal layer lattice material CrBr3 have been measured. From the temperature dependence of the Seebeck voltage and the resistivity it is concluded that the transport of the majority carriers, electrons, occurs by a hopping process. The activation energy for electron mobility is 0.56 eV for conduction along the c‐axis and 0.39 eV for conduction in the (0001) plane. The values of the effective drift mobilities in these two directions are 10−10 cm2/Vs and 10−7 cm2/Vs, respectively. Comparison of optical and photoconductivity data indicated that photoconductivity is associated with the crystal field optical transitions as well as the charge transfer bands.
Resistivity Change of Point Defects during Work Hardening of High‐Purity Copper
Authors: Thom F. 
Published: July 2007

AbstractThe electrical resistivity of high‐purity copper deformed by torsion is examined after deformation and after annealing out of the point defects. Deformation is carried out at 4.2, 20.4, and 90.2 °K, and the increase of resistivity is recorded at 20.4 and 90.2 °K for a number of samples. Measuring temperatures near 80 °K prove to be unreliable for the observation of lattice defects. In accordance with Saada's theory the point defect concentration is found to rise proportional to \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{*{20}c} {\gamma _2 } \\ \int \\ {\gamma _1 } \\ \end{array}\tau (\gamma) $\end{document} at temperatures ≦ 20.4 °K if the measurements, too, are made at such temperatures. If, however, similar measurements are made after deformation at 90.2 °K the data obtained differ markedly from the Saada relation.
On Mechanism of Electron Scattering in InP
Authors: Galavanov V. V. , Siukaev N. V. 
Published: July 2007

AbstractThe Hall mobility of electrons was studied in n‐InP single crystals in the temperature range from 77 to 1000°K at electron concentrations n = 2 × 1015 to 2 × 1017 cm−3 and mobilities μ = 3 × 103 to 4.3 × 104 cm2/Vs. The results agree well with calculations for the mixed mechanism of electron scattering on optical phonons, μ0 = (100/√T)(exp(500/T) −1), and acoustic phonons, μa = 6.53 × 107 T−3/2 cm2/Vs (the deformation potential is assumed to be equal to 21 eV). Scattering on ions and neutral impurity atoms is important in specimens with n > 5 × 1015 cm−3 at low temperatures. The concentration of neutral impurity atoms does not exceed 1014 cm−3 in pure specimens, while in specimens with n > 1016 cm−3 NN reaches the value of 1016 cm−3 and more. The results of the Hall coefficient dependence on the magnetic field strength (0.3 to 20 kOe) at 77 and 300 °K show that the Hall factor A (R = A/nec) approximates 1 in all the specimens with the exception of pure specimens where A ≈ 1.13 at 77 °K. These results agree well with the conclusions drawn from the analysis of temperature and concentration dependences of mobility.
Anomalous Transmission of X‐Rays for Divergent Incident Beam
Authors: Kovev E. K. , Korovin L. I. , Efimov O. N. 
Published: July 2007

AbstractIt is shown that the analytical form of some characteristics of the anomalous transmission of X‐rays for divergent incident beam is different from the corresponding expression derived for the case of parallel beam. In particular, the expressions for the reflection coefficient and half‐width are modified, while the integrated intensity preserves the same meaning. The new content of the reflection coefficient makes it possible to use it for obtaining the integral characteristics of anomalous transmission, connected with different parts of the structure factor. Consideration of the divergence of the incident beam leads to a good agreement of the experimental and theoretical data for the characteristics of anomalous transmission.
Adsorption and Nucleation of Silver on Tungsten
Authors: Sugata E. , Takeda K. 
Published: July 2007

AbstractAdsorption of silver on tungsten has been studied by field emission microscopy in the temperature range from 78 to 1000 °K varying the impinging flux 0,2 to 1.0 monolayer per min. Silver atoms are found to deposit without detectable surface migration at 78 °K substrate temperature on planes other than {110}. Activation energy for surface migration over {100}‐planes is 0.8 eV. The average work function slightly increases from the original value of 4.5 eV at depositions of a small amount of silver and decreases then to 4.0 to 4.2 eV with deposit thickness. The activation energy for desorption in the coverage interval θ = 0.4 to 0.1 and θ = 0.7 to 0.5 are found to be 2.8 and 2.0 eV, respectively. Critical adatom coverage for nucleation is also measured as a function of substrate temperature and impinging flux.
Isotope Inter‐Diffusion and Self‐Diffusion in Solid Lithium Metal
Authors: Lodding A. , Mundy J. N. , Ott A. 
Published: July 2007

AbstractThe inter‐diffusion of Li isotopes in separated 7Li and 6Li metals has been measured in the temperature range 35 to 178° C. The results can be expressed as
equation image
where 7D6 denotes the diffusion of 6Li tracer in pure 7Li metal, and vice versa. The 7D6‐values exceed 6D7 by about 23% at the melting point and by about 37% at 0.7 Tm (°K). There are indications that the striking isotope effect may be due to tunneling. Tunneling considerations founded on a square barrier approximation suggest a dumbbell interstitial mechanism as a likely self‐diffusion model for lithium. According to the calculation for the dumbbell, the contribution from the tunneling process to the effective energy of self‐diffusion is of the same order as, or smaller than, than, the potential barrier to activated motion. Without favoring any particular diffusion model, the following expressions can be computed for uncorrelated self‐diffusion in isotopically pure lithium metals:
equation image
(diffusion coefficients in cm2/S, energies in kcal/mol).
The γ‐Ray‐Induced Electric Conductivity of Fused Silica as Dependent on Field Strength, Temperature, and Irradiation Time
Authors: Onnasch D. 
Published: July 2007

AbstractThe γ‐ray‐induced electric conductivity in fused silica is studied theoretically and experimentally as a function of temperature, electric field strength, sample thickness, and irradiation time. Synthetic glasses containing water show the highest induced conductivity. Caused by an increase of positive centres capturing the excited electrons, the conductivity decreases as t−α with the irradiation time t, where α < 1 is a constant depending on temperature. Within the range from 8 to 300 °K, induced currents are measured with voltages up to 2500 V and dose rates between 10 and 200 mrad/s in synthetic samples, 0.2 to 4 mm thick. The gradual transition from constant conductivity at high temperatures and low field strengths F to an increase of conductivity proportional to F cr F3/2 at low temperatures and high field strengths is explained by the deformation of the Coulomb potential of 2 × 1012 to 5 × 1014 cm−3 singly ionized, electron‐capturing centres under the action of the applied field. The comparison of the theoretical dependence of the electron lifetime on field strength and temperature with the measurements allows to conclude that the mobility is independent of temperature. This implies the elastic scattering of the electrons at about 3 × 1019 cm−3 neutral impurities. Furthermore, the mean free path of the electrons for loss of a phonon at 8 °K is determined to be 106 Å.
Current Saturation in Irradiated Synthetic Fused Silica
Authors: Onnasch D. 
Published: July 2007

AbstractThe γ‐ray‐induced current in synthetic fused silica (containing water) is saturated at field strengths ⪆ 1.4 × 104 V/cm caused by two effects. Besides the schubweg saturation known from photoconductors with blocking contacts, the saturation of the drift velocity of the electrons at the level of the velocity of sound is demonstrated. In some samples, especially at lower temperatures, the effect is accompanied by instabilities of the induced current explained by charge redistributions.
Étude de la molécule trichromique d'acétate complexe Cr3(CH3COO)6OCl · 5 H2O
Authors: Munschy G. 
Published: July 2007

AbstractA partir des fonctions d'onde du quadruplet de spin fondamental de l'ion chromique, on construit des fonctions pour la molécule à trois ions paramagnétiques en interaction d'échange. Pour l'essentiel, le spectre des niveaux d'énergie, donné par un hamiltonien de spin I0 (s1 s2 + s2 s3 + s3 s1) de trois spins 3/2 en interaction, dépend d'un nombre quantique de spin, S. Le fait nouveau réside dans l'intervention des variables orbitales pour le calcul de la structure fine des niveaux S. Pour la première fois, on obtient ainsi un accord satisfaisant avec la courbe expérimentale de la chaleur spécifique aux températures de l'hélium liquide.
Fermi Surface of Tellurium
Authors: Guthmann C. , Thuillier J. M. 
Published: July 2007

AbstractA study of the Shubnikov‐de Haas effect allowed us to determine the Fermi surface of tellurium. At low impurity concentration, the Fermi surfaces are ellipsoidal. When the impurity concentration increases, the ellipsoids coalesce and form a dumb‐bell surface. For p ≈ 1.5 × 1017 cm−3, the ellipsoids are just joining together. From the experimental results obtained in this concentration range, we have been able to calculate some parameters of the valence band, which are in good agreement with the theoretical model.
Anregungswahrscheinlichkeit von Oberflächenplasmonen bei schrägem Elektroneneinfall unter Berücksichtigung der Retardierung
Authors: Dobberstein P. 
Published: July 2007

AbstractDie differentielle Anregungswahrscheinlichkeit für Oberflächenwellen bei Anregung durch schräg auf eine Metalloberfläche treffende schnelle Elektronen wird im Rahmen der dielektrischen Theorie unter Berücksichtigung der Retardierung berechnet. Numerische Werte für Silber werden diskutiert.
Diagram Expansion at Finite Temperatures in the Real Time and Frequency Domains
Authors: Sandström R. 
Published: July 2007

AbstractA method is given for obtaining diagram expansions at finite temperatures in domains for real times and frequencies. As an example the diagram expansions for electrons (in the ordinary electron gas approximation) and phonons are discussed. Network rules are established to obtain all kinds of self energies and propagators in a systematic and simple way. These specify the way in which the different types of propagators G, G≷, Gr. a for, e.g., electrons should be linked together. Generalized Dyson equations for the different electron and phonon propagators are given. As the results are significant both for non‐equilibrium and equilibrium phenomena the corresponding diagram expansions are discussed in terms of the space in which they are most easily handled namely ordinary space and Fourier space, respectively. A diagram dictionary including the network rules is also presented. Finally, the evaluation of screened diagrams is given as an example.
Stray‐Field‐Free and Related Domain Wall Configurations in Thin Magnetic Films (II)
Authors: Hubert A. 
Published: July 2007

AbstractIn Part I [2] it was shown that Bloch walls in thin magnetic films should have a vortex‐like asymmetric and largely stray‐field‐free structure. A rigorous proof of the existence of an analogous asymmetric model for the Néel wall has not yet been given. Therefore, the earlier calculations have been extended in two directions: (i) Bloch walls are calculated also for applied fields. These walls lose the remaining (y) symmetry found in the 180° Bloch walls. The calculations show that their energy increases with increasing applied field. (ii) Néel walls are constructed for the entire interesting range of film thicknesses and applied field values, thus forming a continuous transition from the symmetrical Néel wall at small thicknesses and high fields to the walls with an asymmetric core at large thicknesses and small fields. In fields larger than 0.3 (2 K/Is) only Néel walls are stable for all thicknesses; they may be symmetrical or asymmetric, depending on film thickness and the magnitude of the field. For all walls wall widths are calculated for the purpose of comparison with electron microscope observations.
Notes on the Influence of Spin on the Electrical Conductivity in Strong Magnetic Fields
Authors: Keiter H. , Hajdu J. 
Published: July 2007

AbstractThe longitudinal and transverse electrical conductivity for a system of free electrons interacting with short‐range impurities is calculated. Since in the lowest order Born approximation the transverse conductivity diverges, and the longitudinal conductivity shows unphysical zeroes for certain values of the magnetic field, higher order t‐matrix treatment is required. We obtain spin splitting of the Shubnikov‐de Haas oscillations for spin independent and spin dependent scattering. Compared with the transverse case, the first (0+) maximum is absent in the longitudinal case, provided that no spin flip occurs. Spin flip in the scattering process, however, gives rise to a 0+ maximum. Apart from this fact, the spin flip causes no remarkable change in the oscillatory behaviour of the conductivity.
The Establishment of Long‐Range Order in Ni2Cr Using Electron Microscopy
Authors: Klein H. J. , Brooks C. R. , Stansbury E. E. 
Published: July 2007

AbstractUsing selected area diffraction in transmission electron microscopy, long‐range order in Ni2Cr has been clearly detected. Specimens showing order had been aged for 630 h at 500 °C or for four months at 479 °C. The domain size for the specimen aged at 500 °C was about 100 Å, but the domains for the specimen aged at 479 °C were too small to be resolved.
Spatial Dispersion Effects in the Optics of Metals
Authors: Silin V. P. , Fetisov E. P. 
Published: July 2007

AbstractThe oblique incidence of a light wave on a plane boundary is considered using the method of kinetic equation. The main attention is payed to the study of the influence of longitudinal plasma wave excitation in metals on surface energy losses of light waves and on volume losses in the case of P‐polarization. The significance of Fermi‐liquid effects is considered in detail. An asymptotic behaviour of the field inside the metal is observed for long distances from the boundary.