bluuebunny/crossref_metadata_2025_split huggingface dataset:
Feldelektronenmikroskopische Untersuchungen der Quecksilberkeimbildung
Authors: Paunov M. 
Published: July 2007

AbstractDie Quecksilberkeimbildung aus der Dampfphase wird mit dem Feldelektronenmikroskop untersucht. Die zur Bildung des ersten Keimes not wendigen Zeiten werden bei verschiedenen Temperaturen der Feldemissionsspitze und bei Atomflüssen verschiedener Intensität gemessen. Bei niedrigen Temperaturen der Unterlage, wenn die mittlere Verweilzeit genügend groß ist, nimmt die Übersättigung in der Adschicht stetig zu. Die Keimbildungszeit bestimmt daher die Adatomkonzentration. Für Quecksilber auf Wolfram beträgt letztere etwa 3.2 Monoschichten. Bei genügend hohen Temperaturen der Unterlage ist die mittlere Verweilzeit viel kleiner als die Keimbildungszeit. In diesem Falle ist die Beziehung zwischen Keimbildungsgeschwindigkeit I und Keimbildungszeit τ1 sehr einfach, nämlich I = 1/τ1. Die Versuchsdaten werden in diesem Gebiet qualitativ durch die Volmersche Gleichung beschrieben. Die Aktivierungsenergie für Desorption von einer Mehrschichtbedeckung beträgt 0.6 eV.
Faraday Effect and Spin‐Orbit Interaction of the Lowest Exciton States in Molecular Crystals
Authors: Majerníková E. 
Published: July 2007

AbstractThe spin‐orbit interaction of the lowest excition states of a benzene crystal is calculated with the configuration interaction included. It is shown that the mixing of singlet and triplet exciton states due to the spin‐orbit interaction is negligibly small. The Faraday effect in molecular crystals is investigated taking into account Davydov splitting with application to the lowest singlet exciton states in a benzene crystal. No account is taken here of the interaction involving lattice vibrations and the internal vibrations or of rotations of the molecule as a whole.
Electroreflectance of CdS and CdSe Single Crystals at the Fundamental Absorption Edge
Authors: Gutsche E. , Lange H. 
Published: July 2007

AbstractMeasurements are presented of the electroreflectance spectra of CdS and CdSe single crystals. Comparison with the photon energies of the interband edges and exciton peaks demonstrates that the low‐energy peak of the spectra is dominated by exciton quenching. At higher energies field‐influenced interband transitions are also important at room temperature.
Kinetics of the Thermal Mutual Conversion of F and Z2 Color Centers in KCl:Sr Crystals
Authors: Wolfram G. , Witt V. 
Published: July 2007

AbstractThe thermal equilibrium between F and Z2 color centers in KCl:Sr crystals is studied as a function of the Sr++ concentration c, and the activation energies for the conversion of the centers are determined. For Sr++ molar concentrations between 0.4 × 10−4 and 9 × 10−4 the equilibrium equation is [F]/[Z2] = (2.6/c) exp (− 0.28 eV/kT). The activation energies for the conversions F → Z2 and Z2 → F are qf = 0.76 eV and qr = 1.07 eV, respectively. The results given support the Seitz, model for the Z2 center.
Some Model Problems on the Dynamics of Two‐Component Crystals
Authors: Iosilevskii Ya. A. 
Published: July 2007

AbstractA study is made of the dynamic problem of superstructures such as ABr−1, with r atoms per a unit cell built up on the basis of the nearest neighbour, central, and non‐central model of a simple rhombic, tetragonal, and cubic Bravais lattice.
Magnetoacoustic Resonance Effects in Metals in Inclined Magnetic Fields
Authors: Kaner E. A. , Falko V. L. 
Published: July 2007

AbstractA theoretical study is made of the features of magnetoacoustic resonance at high magnetic fields in metals with convex Fermi surfaces. For inclined fields the resonant ultrasonic attenuation lines are due to the drift movement of electrons near the boundary section or elliptical limiting points of the Fermi surface. The shape, width, and angular dependence of the amplitudes of the resonance lines are investigated.
EPR Evidence of Exchange‐Coupled Ion Pairs and of Isolated Ions in Some Chlorosubstituted Cupric Acetates
Authors: Dall'olio A. , Dascola G. , Varacca V. 
Published: July 2007

AbstractSome chlorosubstituted cupric acetates are studied by EPR (X‐band) in order to examine the effect of different environments on the exchange interactions between the cupric ions. In hydrated and anhydrous tri‐ and dichlorosubstituted cupric acetates only isolated ions are present, while hydrated cupric acetate and monochloroacetate show only exchange‐coupled ion pairs. However, in anhydrous cupric acetate and monochloroacetate both these situations are found to occur. Some possible interpretations of these results are given.
Theory of the Hall Effect in Disordered Systems: Impurity Band Conduction (II)
Authors: Aldea A. 
Published: July 2007

AbstractA one‐electron quantum‐mechanical formula for the low‐field Hall effect is derived for an ac electric and dc magnetic field. A comparison is made between the adiabatic and stationary approach to this problem. With some simplifying assumptions the formula is applied to two simple density‐of‐states models and the results indicate that the sign of the Hall effect depends on the degree of filling of the bands.
Spontaneous Solid—Vapour Transformation of Negative Crystals in Diphenyl
Authors: Georgieva A. , Nenow D. 
Published: July 2007

AbstractObservations show a spontaneous transformation at constant temperature of the form of the negative crystals (inclusions) of own vapours within diphenyl crystals. A study is made of the kinetics of this process. The process leads to the creation of inclusions with equilibrium form. The spontaneous transformation of the negative crystals is a very convenient method for studying the growth rates of the crystal surfaces for very small super‐saturations under very pure conditions. It is established at several different temperatures that the normal rate of growth depends linearly on the curvature of the inclusion (i.e. the supersaturation). The activation energy of the transformation process is calculated from the experimental data.
Cyclotron Resonance in Zinc
Authors: Henningsen J. O. 
Published: July 2007

AbstractResults are given for cyclotron resonance in zinc with the magnetic field in the (1010) and the (0001) planes. Four distinct resonance series are observed and interpreted in terms of the Fermi surface model due to Gibbons and Falicov. The mass values are in agreement with earlier cyclotron resonance measurements by Shaw, Sampath, and Eck, but there is some disagreement over the angular range of observability of one of the resonances. Weak traces of an additional resonance series, not reported earlier, are seen and an h‐resonance, reported by Shaw, Sampath, and Eck, is identified as probably arising from tip effects. Finally, tip effects are investigated systematically for two central resonances and one limiting point resonance, and the results are to some extent interpreted in terms of the theoretical treatment given by Smith.
Mössbauer Study of the FeMn Carbides (Fe1−xMnx)3C and (Fe1.1Mn3.9)C2
Authors: Huffman G. P. , Errington P. R. , Fisher R. M. 
Published: July 2007

AbstractWe have performed Mössbauer experiments on FeMn carbides having the cementite structure (Fe1−xMnx)3C, where x ranges from 0 to 0.6, and on a Hägg carbide with the Pd5B2 structure, (Fe1.1Mn3.9)C2, over the temperature range from 12 to 500 °K. Above the Curie temperature, the spectra exhibit a quadrupole interaction ranging from about 0.20 to 0.28 mm/s and the contributions from Fe atoms in the two types of cementite lattice sites can be identified. It is found that Mn atoms have a slight preference for “general” over “special” lattice sites in cementite. The specimens containing 0 to 20% Mn all become ferromagnetic at low enough temperatures, and the effective field decreases with Mn concentration very rapidly, extrapolating to 0 at about 34% Mn. Below Tc, the quadrupole splitting decreases drastically to less than 0.05 mm/s. Most of the results seem to be consistent with a donor theory in which C donates both of its 2p electrons to the metal d‐band, giving the Fe in cementite an average electron configuration of approximately 3d7.66 4 s1.
Role of γ‐Radiation Intensity on the First Stage of the Room‐Temperature F‐Colouring in NaCl
Authors: Agulló‐López F. 
Published: July 2007

AbstractAn investigation is made of the effect of γ‐ray intensity (within the range 500 to 30000 R/min) on the first stage of room‐temperature F‐colouring in NaCl. In accordance with recent work, the first stage is found to consist of two different components (fast and slow), both of which are observed to be approximately exponential. The saturation value for the fast component seems to be independent of intensity whereas that for the slow component increases with intensity in the same way as the total saturation level. The observed growth rates are not monotonic over the entire intensity range. However, for intensities ≧ 1000 R/min the growth‐rate for both the fast and the slow processes appears to be a decreasing function of γ‐radiation intensity. A brief qualitative discussion of these results in terms of a simple model is presented.
Energy Band Structure of Germanium
Authors: Morgan D. J. , Galloway J. A. 
Published: July 2007

AbstractThe energy bands of Δ7‐type symmetry in the (100) direction in the first Brillouin zone are calculated for germanium by diagonalizing a k · p Hamiltonian matrix referred to basis functions at k = 0 which transform according to the extra irreducible representation Δ7 of the double group of the wave vector k (1, 0, 0). Effective masses at k = 0 are used to calculate the magnitudes of the relevant parameters. It is found that the relative signs of the matrix elements of momentum between the basis functions at k = 0 have a marked effect on the computed energy band structure.
Single Crystal Growth of Calcium Pyroniobate
Authors: Graves P. W. 
Published: July 2007

AbstractSingle crystals of calcium pyroniobate, Ca2Nb2O7, have been grown from the melt by the Czochralski method. Crystal growth along a 〈OVW〉 direction is easy, being characterized by the formation of large area mirror facets, which under certain conditions leads to the growth of thin ribbon crystals. Growth along [100] is difficult and rates of less than 0.4 cm/h have to be used to obtain crack free crystals. Growth defects such as inclusions and cavities were found to be absent in the crystals, and no evidence was found for the presence of impurity striations.
Neutron‐Diffraction Study of Antiferromagnetism in USb2 and UBi2
Authors: Leciejewicz J. , Troć R. , Murasik A. , Zygmunt A. 
Published: July 2007

AbstractThe magnetic ordering in polycrystalline USb2 and UBi2 is studied by means of neutron diffraction. It is found, that the magnetic unit cell of USb2 is twice the size of the chemical cell along the c‐axis, with alternating ferromagnetic sheets in the sequence + − − + …︁. In the case of UBi2 the magnetic and chemical unit cells are identical. The sequence of ferromagnetic sheets is + − + − …︁ in the direction of the c‐axis. In both cases magnetic moments are parallel to the c‐axis and their magnitudes are (0.94 ± 0.03) BM for USb2 and (2.1 ± 0.1) BM for UBi2.
Epitaxial Growth of Vacuum‐Evaporated Co on NaCl. II. Analysis of Diffraction Patterns
Authors: Otsuka K. , Wayman C. M. 
Published: July 2007

AbstractThe existence of long streaks in 〈111〉 directions must be taken into consideration in order to consistently explain diffraction patterns from f.c.c. films in (001), (110), (111), and (211) orientations. In orientations other than (110) the apparent streaks correspond to the projection of 〈111〉 reciprocal lattice vectors onto the plane normal to the electron beam, and these are ascribed to buckling. The (110), (111), and (211) orientations are not thought to be truly epitaxial and appear to be associated with substrate irregularities. The epitaxially grown films are substantially f.c.c. containing many microtwins rather than f.c.c. films with h.c.p. regions which have transformed on {111} planes, indicating a suppression of the f.c.c. → h.c.p. martensitic transformation in thin films.
An Interpretation of the Dislocation Velocity‐Stress Exponent
Authors: Evans K. R. , Bailey D. J. , Flanagan W. F. 
Published: July 2007

AbstractA thermal‐activation model of deformation has been used to analyze the dislocation velocity‐stress exponent, m*, from the relationship v ∝ τ* m* where τ* is the effective stress acting on a mobile dislocation. It is shown that m* is directly related to the retarding‐force profile of the rate‐controlling obstacles to dislocation motion and may be quantitatively evaluated from temperature and strain‐rate sensitivity measurements. Values of the dislocation velocity‐stress exponent reported in the literature, which are based on the applied stress, are shown to be structure sensitive and are not uniquely characteristic of the material.
Epitaxial Growth of Gold on Cadmium Iodide
Authors: Persson B. , Norden H. 
Published: July 2007

AbstractThe epitaxial growth of gold on (0001) surfaces of cadmium iodide is studied by transmission electron microscopy. A method for the preparation of suitable substrates is given. Dark field studies of different stages of film growth show that the deposit nucleates with a particular orientation, and during further growth this orientation changes by 30°. The diffraction pattern contains many extra twin and double diffraction spots which arise from twins and double position boundaries introduced during island coalescence.
Magnetic After‐Effect in Deformed Cobalt Single Crystals
Authors: Gerward L. 
Published: July 2007

AbstractThe magnetic after‐effect of deformed cobalt single crystals is investigated in the temperature region −120 to + 95 °C. Over the entire temperature region a weakly temperature‐dependent relaxation is found which obeys a logarithmic time law. Above room temperature another after‐effect is superimposed. This is interpreted as a diffusion aftereffect due to point defects. The annealing of the defects takes place at the same temperature, and obeys a first‐order rate equation. Methods of measurement are developed which take the annealing into account.
Magnetic Susceptibility of Face‐Centered Cubic Iron‐Rhenium Alloys
Authors: Arajs S. 
Published: July 2007

AbstractMass magnetic susceptibility of iron‐rhenium alloys containing 0.6, 1.6, 3,2, and 7.2 at% rhenium have been studied in the f.c.c. phase up to 1500 °K. Their magnetic behavior cannot be described by the Curie‐Weiss law. The 1/(χT) vs. 1/T plots, where χ is the magnetic susceptibility and T the absolute temperature, reveal indirectly that the antiferromagnetic character of f.c.c. iron is not altered by alloying with rhenium.
On the Classical Theory of the Optical Properties of Free Carriers in Semiconductors
Authors: Kosinskaya A. I. , Uritsky S. I. 
Published: July 2007

AbstractMagneto‐optical effects are studied in the infrared and microwave region for carriers in a doubly degenerate band (heavy and light holes in Ge). The treatment is based on the classical kinetic equation. The dependences of the magneto‐optical effects on frequency and magnetic field are found for the low and high frequency regions and for the classical regions of low and high magnetic fields. Some of these effects may be due to the light holes under certain conditions. It is shown that under these conditions, plane‐polarized light may become circularly polarized when it passes through the crystal.
Conduction Band Structure of HgTe from Thermomagnetic Measurements
Authors: Szymańska W. 
Published: July 2007

AbstractThe electron effective mass in n‐type HgTe is found for concentrations between 5 × 1017 and 6 × 1018 cm−3 by measurements of the thermoelectric power in a magnetic field. The effective mass is strongly dependent on the electron concentration. This dependence can be explained by using Kane's model with the parameters mn/m0 = 0.018, ε0 = 0.21 eV. In the investigated samples the dominant electron scattering is due to ionized impurities.
Electroluminescence of AgCl Crystals Excited by Short Field Pulses
Authors: Vacek K. 
Published: July 2007

AbstractAn investigation is made of the electroluminescence excited by short electric field pulses in pure and doped (0.01 mol% TlCl or 0.01 mol% MnCl2) AgCl crystals. The majority of the results obtained (dependence of electroluminescence on voltage and pulse duration; threshold exciting voltage) are similar to electroluminescence phenomena in ZnS. Illumination of the electroluminescence cell by red light, and by UV light, respectively decreases and increases the electroluminescence brightness. Attempts to interpret the data in terms of a bipolar field emission model prove satisfactory under the assumption that the luminescence centres are cation vacancies.
ESR on UV Irradiated Lead Halides at 80° K
Authors: Arends J. , Verwey J. F. 
Published: July 2007

AbstractResults are presented of electron spin resonance measurements on uv irradiated single crystals of PbCl2, PbBr2, and PbI2 at liquid nitrogen temperature. Both pure single crystals and PbBr2 crystals doped with Tl+, Ag+, Cu+, and Bi+++ ions are studied. The ESR spectra indicate that Pb+ ions occur as an initial step in the photochemical decomposition. These ions are probably present in clusters of two or three and coagulate to metallic lead particles. The ESR signals due to the conduction electrons of these small lead particles are studied. Some hole centres which are formed during the irradiation are also described. The experiments show that the ambient conditions of the crystals are much more important in the photolysis process than the presence of foreign ions.
Point Defects in Neutron‐Damaged Silica Glass
Authors: Lungu S. 
Published: July 2007

AbstractA point defect structure for neutron‐damaged silica glass is postulated. Pease's formula as tested by Monte Carlo calculations using a special closed model of a silica glass lattice is applied to the experimental volume compaction data, by considering SiO2 point defects. Some new experimental data, which are presented here, are used to compute the threshold energies.
The Orientation of Crystallites in ZnTe Thin Films
Authors: Spinulescu‐Carnaru I. 
Published: July 2007

AbstractThe orientation and size of the crystals in ZnTe thin films are studied as a function of the stoichiometric and growth conditions using electron diffraction and X‐ray techniques. The conditions governing the growth of relatively large crystals in the texturised ZnTe thin films are established.
Magnetic Susceptibilities of Sodium Neodymium Tungstate and Sodium Terbium Tungstate
Authors: Wang F. F. Y. , Kestigian M. 
Published: July 2007

AbstractThe magnetic susceptibilities of sodium neodymium tungstate Na0.5 Nd0.5 WO4 and sodium terbium tungstate Na0.5 Tb0.5 WO4 were measured from 10 to 800 °K. They were found to become antiferromagnetic at 20 and 39 °K, respectively. Their magnetic behaviors suggest the existence of clustering of magnetic ions.
On the Isotope Effect in Interstitial Diffusion III. Quantum Corrections
Authors: Pegel B. , Lepski D. 
Published: July 2007

AbstractA one‐dimensional Prigogine‐Bak model of interstitial diffusion which has been discussed classically in two earlier papers, is treated quantum mechanically. By means of S‐matrix theory an energy transport equation is established for the diffusing particle. By solving this equation with the appropriate Prigogine‐Bak boundary condition, the quantum corrections for the frequency factor of the diffusion constant are obtained. It is found that the classical isotope effect is generally reduced by these corrections which are important for small interstitial masses and/or low temperatures.
Recoil Effects in the Polaron Problem
Authors: Porsch M. , Röseler J. 
Published: July 2007

AbstractA general formalism for diagonalizing quadratic forms of boson operators [7], is used to obtain a translationally invariant variational ansatz which is suitable for calculating the polaron self‐energy, effective mass, and energy momentum relation in both coupling limits. The self‐energy and effective mass are calculated in the weak‐coupling limit. The strong coupling limit shows the wellknown α2‐dependence of the self‐energy. Diagonalizing the quadratic part of the recoil term gives rise to an additional self‐energy contribution to the cutoff.
Optical Absorption of an Interstitial Alkali‐Earth Cation in an Alkali‐Halide Crystal
Authors: Wang S. 
Published: July 2007

AbstractUsing both the concepts of the polaron model of the electron‐excess color center and the valence‐electron model of atoms introduced in this paper, we have formulated a method to compute the optical absorption energy of an interstitial alkali‐earth cation contained in an alkali‐halide crystal. The numerical results are given for the interstitial ion Ca+ in KCl and KBr. The possibility of Kojima's model for the Z2 and Z3 bands is also discussed in this work.
Electronic States of the MA‐Centers in KCl
Authors: Wang S. 
Published: July 2007

AbstractThe electronic states of the MA‐center in a potassium‐chloride crystal containing sodium are theoretically investigated on the basis of the Schneider model. The method is formulated by using both the polaron model and the quasi‐continuum model of electron‐excess centers. The impurity potential is treated by the valence‐electron model of atoms introduced in the preceding paper. We have used our theoretical results to discuss the origin of the MA bands reported by Schneider.
Atomie Arrangement in the Homogeneity Range of the Laves Phases ZrFe2 and TiFe2
Authors: Brückner W. , Kleinstück K. , Schulze G. E. R. 
Published: July 2007

AbstractThe Laves phases ZrFe2 (MgCu2 type) and TiFe2 (MgZn2 type) have a homogeneity range of several atomic percent (mainly on the side rich in iron). An investigation is made of the modifications to this type of AB2 lattice which result from an excess of B‐atoms. X‐ray and neutron diffraction measurements show that for both ZrFe2 and TiFe2 the excess B‐atoms are associated with the sites of A‐atoms. The concentration variation of the lattice constants confirms these results.
The Influence of Vacancies and Impurities on the Damage Production in Platinum Electron‐Irradiated at 90 °K
Authors: Duesing G. , Hemmerich H. , Meissner D. , Schilling W. 
Published: July 2007

AbstractIn platinum foils of 99.999 and 99.9% purity different vacancy concentrations are frozen in by quenching. The foils are then irradiated with 3 MeV electrons at 90 °K. The difference between the radiation damage build‐up in these foils and the damage built‐up in annealed foils which are irradiated simultaneously is investigated up to electron doses corresponding to induced resistivities of 3 × 10−7 Ωcm. It is found that 1. pre‐quenching can reduce the initial damage rate by a factor of more than 20; 2. the initial damage rate of the annealed samples is independent of their purity; 3. with further irradiation, the rate of decrease of the damage rate for the annealed samples increases with the purity of the samples; 4. for large damages the dose dependence of the damage lies between Δϱ ∼ φ and Δϱ ∼ φ1/2;. The results can easily be explained by interstitials which migrate freely at 90 °K and are either annihilated by vacancies or converted into another interstitial configuration at impurities. The direct production of immobile interstitials at 90 °K can be excluded.