bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electroabsorption near the n = 1 lines of the yellow and green series of Cu2O
Authors: Deiss J. L. , Daunois A. , Nikitine S. 
Published: July 2007

AbstractThe effect of an ac electric field on the n = 1 lines of the yellow and green series of Cu2O has been studied at 4.2°K using single crystals, polarized light, and a modulation technique. In the field, an “ignition” of the two lines λ = 6098 Å and λ = 5830 Å is observed. This ignition effect depends on the geometry of the experiment, and gives information on the nature of both transitions as well as on the bands involved in the formation of these IS excitons. The line λ corresponds to an orthoexcitonic electric quadrupole transition Γ, while the line λ is a mixed electric quadrupole Γ and magnetic dipole Γ transition, with a stronger magnetic dipole character.
Semiconductor–metal phase transformation of tetrahedrally coordinated semiconductors
Authors: van Vechten J. A. 
Published: July 2007

AbstractThe standard Drickamer high‐pressure resistance cell has recently been recalibrated. With this recalibration, it is shown that, within experimental uncertainty, the difference in internal energy between the diamond and the β‐tin forms of group IV elements is equal to the difference in energy between the corresponding Penn‐model semiconductor, corrected for d‐core dehybridization for Ge and Sn, and a free electron gas.
Electronic polaron formulation of the optical properties of U2 centres in various alkali halides
Authors: Hagston W. E. 
Published: July 2007

AbstractA semi‐empirical formulation of the optical properties of U2 centres is presented which incorporates a many‐body treatment of electronic properties in terms of the concept of the electronic polaron. The results of the analysis provide further confirmation for the model which attributes the optical absorption process of the U2 centre to the transfer of an electron from the surrounding halide ions onto the interstitial hydrogen atom.
A kinetic approach to fracture of solids. II. The time to the fracture of a specimen under constant load in the presence of propagating cracks
Authors: Orlov A. N. , Petrov V. A. , Vladimirov V. I. 
Published: July 2007

AbstractThe fracture of solids under creep conditions is considered as a process consisting of nucleation due to thermal fluctuations and subsequent coalescence of numerous interacting microcracks. The main crack causing the rupture of the specimen is produced by coalescence of several microcracks and propagates by joining other microcracks which nucleate in its neighbourhood due to local stress concentration. The time to the fracture τ of a homogeneous specimen under constant stress is calculated and is shown to be the sum of the time of generation τg and the time of propagation τp of the main crack. τg is governed by stochastic processes and displays a size effect (dependence on the volume of the specimen), whereas τp is determined by the stress concentration near the crack during the initial stages of its propagation. Both times are proportional to the time of nucleation τm of a microcrack.
On the use of zero‐range potentials in some energy band problems
Authors: Bhagwat K. V. , Subramanian R. 
Published: July 2007

AbstractThe method of zero‐range potentials is described and its applicability to the study of some qualitative features of electron energy bands in three‐dimensional crystals is discussed. It is shown that the Saxon‐Hutner conjecture on band gaps is true for the special case of a linear periodic chain of three‐dimensional zero‐range potentials.
Optical properties of the ion‐radical salts of tetracyanquinodimethane in the solid state
Authors: Vlasova R. M. , Gutman A. I. , Rozenshtein L. D. , Kartenko N. F. 
Published: July 2007

AbstractAbsorption spectra of TCNQ salts with different donors — metals, organic conjugated compounds, dyes in solid state‐are investigated. The study was carried out on thin films obtained by grinding of salt on quartz substrate. For the Cs(TCNQ) salt reflection and absorption spectra were investigated on single crystals. Salt spectra in the solid state differ greatly from the isolated anion‐radical spectrum. For simple salts there is a close resemblance between thin film spectra and the spectrum of the () dimer, which proves that in the solid state pair interaction of ion‐radicals predominates. Complex salt spectra are characterized by strongly smeared absorption bands, especially in the Qn+ (TCNQ) salt. The correlation between absorption spectra and electrical and magnetic properties of the salts is noted. For Cs(TCNQ) single crystals a stronganisotropy of reflection and absorption is found. Both intensity and character of the absorption spectra depend on the polarization direction. The obtained data are correlated with the strong intermolecular interaction along TCNQ molecule stacking directions and the translational symmetry of the crystal. Absorption spectrum changes during destruction of the crystalline structure are found. The absorption spectra of TCNQ derivatives of dyes in solution are the result of superposition of ion‐radical bands and the initial dye band. The character of the solid film spectrum is connected with the influence of the steric factor on the intermolecular interaction.
On the electrical resistivity by scattering on metallic grain boundaries
Authors: van der Voort E. , Guyot P. 
Published: July 2007

AbstractThe contribution to the residual electrical resistivity of high angle grain boundaries due to the scattering of conduction electrons by voids into the boundaries is calculated for Au, Cu, and Al. Two types of geometries are considered: array of cylindrical voids for symmetrical tilt boundaries and point voids for boundaries with lower symmetry. In both cases a self‐consistent potential, solution of a linearized Thomas‐Fermi equation, is used. This contribution, of about a few 10−13 Ωcm2, accounts for at maximum 25% of the experimental specific grain boundary resistivity, which seems to indicate that bulk effects predominate.
On glow curves obtained by ionizing and non‐ionizing radiation
Authors: Kristianpoller N. , Israeli M. 
Published: July 2007

AbstractTwo distinct groups of glow peaks have recently been observed in nominally pure, uv excited alkali halides. These glow peaks are investigated in comparison with those obtained by X‐irradiation. Different processes are assumed to be responsible for the excitation of the thermoluminescence (TL) emitted at the various peaks. One process, which is connected with the creation of Frenkel pairs, causes the excitation of TL by uv light in the region of the first exciton band. This process appears also to be dominant in the excitation of “virgin”, pure samples by X‐rays. Another process is involved in the excitation of TL by ionizing uv light. This excitation, which is restricted in this case to a thin surface layer, is attributed to the presence of oxygen impurities and the generation of VK centres.
Electronic structure and optical properties of amorphous germanium and silicon
Authors: Kramer B. 
Published: July 2007

AbstractThe complex band structures, the imaginary parts of the dielectric constant, and the densities of states of electrons in amorphous Ge and Si are calculated using a generalized pseudopotential formalism based on the Green's function techniques. The short range order is assumed to be the same as in the cubic crystalline systems. The long‐range order is relaxed by using a two particle correlation function, consisting of Gaussian functions centered at the lattice points. The half widths of the Gaussian functions increases with increasing lengths of the lattice vectors. It turns out, that the band edges near axis Γ‐L are less influenced by disorder than for other k‐points in the Brillouin zone. This is confirmed by comparing the calculated imaginary part of the dielectric constant with the experimental one.
Polaron scattering of free carriers in tellurium
Authors: Selders M. , Gspan P. , Grosse P. 
Published: July 2007

AbstractBecause the polaron coupling constant in tellurium is relatively large, polar optical scattering should be important in the charge transport by free carriers. Reflection and transmission measurements on heavily doped samples in the far infrared yield the amount and the frequency dependence of the free carrier scattering in the spectral region of the reststrahlen bands. From the amount of the increase in scattering at the eigenfrequency of the LO phonons the contribution of polaron scattering can be determined.
The effect of intersite correlation on the metal–insulator transition
Authors: Schneider J. , Heiner E. , Haubenreisser W. 
Published: July 2007

AbstractThe effect of intersite correlation on the metal–insulator transition is investigated considering an extended Hubbard model. It is shown that it is impossible to describe consistently the transition by a variation of the lattice parameter a within the one‐electron picture, using an one‐particle Green function.
Exciton–exciton annihilation in pyrene crystals
Authors: Vol E. D. , Goloyadov V. A. , Kukushkin L. S. , Naboykin Yu. V. , Silaeva N. B. 
Published: July 2007

AbstractSpecific features of the exciton–exciton annihilation process for slow diffusion systems are considered in terms of excimer luminescence in pyrene crystals. In this case luminescence decay curves allow a direct determination of the diffusion coefficient and the mean free path of the excitation during its lifetime. Analogy between excimer excitations and the well‐known slow excitons is discussed. The importance of the experimental separation of excimer and monomer excitons whose kinetic parameters are greatly different is emphasized.
Quantum theory of localized defect migration in solids
Authors: Yakhot V. S. 
Published: July 2007

AbstractA theory of solid state diffusion of localized defects, i.e. defects whose formation is accompanied by large deformation of the crystal lattice, based on the theory of multi‐phonon processes, is presented. An expression for the jumping probability is given. The independence of the diffusion coefficient on temperature at low temperatures and an Arrhenius law with temperature dependent pre‐exponent at high temperatures were established.
Self‐diffusion of Zn and Se in ZnSe
Authors: Hexkicberg M. M. , Stevexsok A. 
Published: July 2007

AbstractThe high‐temperature defect equilibria of ZnSe have been studied by self‐diffusion measurements on single crystals as a function of temperature, component partial pressure, and added impurity content. The self‐diffusion of Zn was found to be independent of component partial pressure and is expressed as Dzn = 9.8 exp (3.0 eV/kT) cm2 s−1, for the temperature range 760 to 1150 °C. Doping with Cu or A1 enhanced the self‐diffusion of Zn under Zn saturation at lower temperatures. The self‐diffusion of Se was found to be Dse = 0.13 × exp (2.6 eV/kT) cm2 s−1, for Se‐saturated crystals in the temperature range of 860 to 1020 °C, and decreased with decreasing pressure of Se2. Doubly‐ionized Frenkel defects are proposed as the dominant mobile defect on the Zn sublattice and a combination of neutral Se interstitials and doubly‐ionized Se vacancies on the Se sublattice. A tentative defect equilibrium isotherm for ZnSe is given.
Raman scattering intensity of polaritons for general wave vectors I. Theory
Authors: Unger B. , Schaack G. 
Published: July 2007

AbstractRelations for the Raman scattering efficiency of polaritons in uniaxial piezoelectric crystals have been formulated for general directions of the wave vector. These relations are well suited for evaluating experimental data on the various mechanisms of the electron‐lattice interaction. For this purpose a phenomenological description of the dispersion of polaritons has also been given, starting from Huang's equations of motion of long wavelength polar lattice vibrations. The case of large wave vectors (k ≫ ωph./c, angular dispersion of phonons) is included in the theory.
On the theory of piezothermopower anisotropy in n‐type si in the region of phonon drag
Authors: Lutsyak V. S. , Wrrsowcir V. M. 
Published: July 2007

AbstractThe effect of phonon drag on the thermoelectric properties of n‐type Si is studied. Basing on the theory of anisotropic scattering, the influence of elastic deformations on the ther‐niopower at low temperatures is considered. The role of different scattering mechanisms for elcctrons and phonons is discussed. The theoretical results are compared with the experimental data of papers [3] and 191.
Temperature dependence of the creep strain jump in lead and indium at the transition to superconductivity
Authors: Soldatov V. P. , Startsev V. I. , Vainblat T. I. 
Published: July 2007

AbstractThe temperature dependence of the creep strain jump was invcstigated on Pb and In single and polycrystals of 99.999% purity in the region of the N → S transition. To achieve the strain jump the creeping sample was switched from the normal to superconducting state by taking off the magnetic field, H > He, of the solenoid that contained the sample. A tcmperaturc run was followed in the range 1.65 to 4.2 °K for lead and 1.65 to 3.4 °K for indium. The magnitudes Δε(T) of the step in creep strain at various temperatures were reduced to the value at T= 0 7deg;K and the curve Δε(T)/Δ ε(0)= f(T/Tc) as fit to Δε(T)/Δε(0) = α(T/Tc)2 in the interval 0.2≦ T/Tc ≦ 1. Possible mechanisms are discussed that might be responsible for the jump of the creep strain at N → S.
Magnetic phase transitions in the UAs‐use system
Authors: Leciejewicz J. , Troć R. , Murasik A. , Palewski T. 
Published: July 2007

AbstractThe transition between antiferromagnetic UAs and ferromagnetic USe has been studied by neutron‐diffraction. The addition of Se to UAs produces a rapid disappearance of the high‐temperature magnetic phase of UAs (type I) and a stabilization of the low‐temperature magnetic modification (type I A). When the amount of Se further increases four transient magnetic structures appear gradually. All are cosinusoidally modulated along the c‐axis with periodicity c/2. Their magnetic unit‐cells are N‐multiples of the f.c.c. chemical unit cells along one direction: N = 5, 7, 9, and 11. The stability ranges of all magnetic phases present in the solid‐solution UAs‐Use and their corresponding Néel points have been determined.
Mobility of electrons in CdxHg1xTe under high hydrostatic pressure
Authors: Stankiewicz J. , Giriat W. 
Published: July 2007

AbstractAn investigation is made of the influence of high pressures on the electron mobility in CdxHg1−xTe. It is shown, that the established energy band structure for this material is in full agreement with the experimental results obtained. Scattering on ionized impurities and on optical phonons was considered in the calculation of μ = f(x) at 77 K. The calculation of μ = f(x) is qualitatively consistent with the measured data.
Determination of exciton diffusion length from photoconductivity low‐temperature spectra
Authors: Novikov B. V. , Ilinskii A. V. , Lieder K. F. , Sokolov N. S. 
Published: July 2007

AbstractThe spectral distribution of the photoconductivity of CdS and CdSe single crystals has been investigated at 77 °K in a wide spectral range. The values of the exciton diffusion lengths in these compounds have been obtained from the photocurrent spectra using the absorption coefficient data. The exciton diffusion lengths were found to be within the range of 2000 to 10000 Å for CdS and 2000 to 4000 Å for CdSe. The proposed model involves the diffusion of the excitons to the surface, where they dissociate into free carriers interacting with the near‐to‐surface centres. The role of the space charge layer in these phenomena is discussed.
Influence of pressure on the mobility in heavily doped n‐type indium antimonide
Authors: Litwin‐Staszewska E. , Porowski S. , Filipchenko A. A. 
Published: July 2007

AbstractThe resistivity ϱ of n‐type InSb doped with Te, Se, and S was measured as a function of the hydrostatic pressure up to 12 kbar, at 77 and 300 °K. We observed that samples doped with different impurities have different ϱ(P) dependences. The experimental results were compared with theoretical calculations based on the papers of Korenblit and Shestobitov [2] and Zawadzki and Szymańska [3]. The agreement between theory and experiment is good for Te‐doped samples and is highly unsatisfactory for S‐ and Se‐doped samples. It is suggested that the discrepancies of the latter are caused by the existence of short‐range potential centres in S‐ and Se‐doped samples.
Scattering on short‐range potentials in InSb
Authors: Litwin‐Staszewska E. , Porowski S. , Filipohenko A. A. 
Published: July 2007

AbstractFormulae are given for the relaxation time of scattering on short‐range potential centres associated with ionized and neutral defects in n‐type InSb. The effect of pressure on the partial resistivity associated with this mechanism of scattering and, also for this mechanism, the scattering parameter r' which is used in describing thermomagnetic effects are calculated. The results obtained confirm the suggestions of a previous paper [1] concerning the contribution of short‐range potentials to the scattering in heavily doped n‐type TnSb.
Transformation of tellurium valence band induced by hydrostatic pressure
Authors: Anzin V. B. , Bresler M. S. , Farbstein I. I. , Itskevich E. S. , Kosichkin Yu. V. , Sukhoparov V. A. , Teleynev A. S. , Veselago V. G. 
Published: July 2007

AbstractThe investigation of the Shubnikov‐de Haas effect in tellurium under hydrostatic pressure up to 12 kbar revealed a significant distortion in the shape of the Fermi surface of the holes indicating a disappearance of a saddle point in the valence band energy spectrum. A simple linear model of the energy spectrum transformation is proposed which describes quantitatively the whole set of the experimental data.
Optical properties and energy band structure correlation of sphalerite (A3B5) and chalcopyrite (A2B4C52) Crystals
Authors: Donetskich V. I. , Poplavnoi A. S. , Sobolev V. V. 
Published: July 2007

AbstractThe reflectivity spectra of Galls, ZnGeAs2, InAs, and CdSnA2 have been investigated in the range 1.5 to 5 cV at 77 and 293 °K by improved methods and in the range 5 to 12.5 cV at 293 °K by means of a spectrometer VMR‐2. A more complex structure of the spectra than earlier known have been established. Group‐theoretical analysis of the zero slopes and selection rules for chalcopyrite interband transitions have been performed and a correlation model of the interband transitions of GaAs and ZnGeAs2 type crystals have been proposed. Good agreement of experimental and theoretical energy transitions have been obtained.
Uniaxial stress effects of the UV‐absorption bands of In+ and T1+ doped alkali halide crystals in a molecular treatment
Authors: Dultz W. 
Published: July 2007

AbstractThe stress‐induced dichroism of the UV‐absorption bands of KCl:In+ and KI:Tl+ is investigated. The splitting ratio of the A‐and C‐band under stress is not consistent with predictions of a crystal field model of the defect. This discrepancy is explained by introducing a stress‐dependent axial term of the spin‐orbit coupling which depends on the covalent character of the bond between the defect and its neighbour ions. The strong temperature dependence of the stress effects is a consequence of the anharmonicity of the local elastic constants near the defect.
Single phonon x‐ray scattering from alkali halides I. The influence of eigenvectors
Authors: Reid J. S. 
Published: July 2007

AbstractVariations in the eigenvectors given by a number of force models for the alkali halides are examined for wave vectors lying along the: [1,0,0], [1,1,0], and [1,1,1] directions. Among the models considered are least‐squares‐fitted shell models for NaF, NaCl, NaBr, NaI, KCl, and KBr. Substantial differences in the eigenvectors given by different models for one material are found, even when the models fit phonon frequencies well. In addition it is found that the fractional variation of the eigenvectors with temperature is similar to the fractional variation of the square of the phonon frequencies. The method of determining the ratio of the eigenvectors of the two ions from the one‐phonon X‐ray scattering is discussed, and the sensitivity of this method is numerically examined. Although this sensitivity varies widely in reciprocal space it is possible to choose values of the scattering vector where this ratio can be determined to about ± 0.03 for a 20% accuracy in the one‐phonon scattering. The effect of the eigenvectors on the Debye‐Waller factors is also considered and shown to produce an uncertainty in the Bkvalues of the order of 1% at 300 ° K. It is concluded that measurements of the X‐ray intensity scattered by a transverse mode could distinguish between the eigenvector ratios given by fitted shell models and models determined by macroscopic data. Measurements to an accuracy of 1% could further distinguish different good shell models.
Migration and incorporation of tellurium in CdS
Authors: Nebauer E. , Lautenbach J. 
Published: July 2007

AbstractThe diffusion (D) and solubility (S) properties of tellurium in CdS are investigated by means of the vapour pressure method. The concentration profiles measured by special microtome and by tracer techniques consist of two parts in most cases: the first is attributed to bulk diffusion and the second is assumed to be caused by dislocations. The first region of profiles shows usual erfc‐behaviour only under sulfur pressure annealings, and only for this case the pressure dependences of D and S have been determined simultaneously and quantitatively. The van Gool exponents found experimentally are compared with values estimated on the basis of a simple dissociative diffusion model and good agreement is obtained.
A model of the temperature dependent part of stage I work‐hardening due to jog‐dragging (II)
Authors: Messerschmidt U. 
Published: July 2007

AbstractThe system of differential equations, established in Part I, of the density of nonconservatively moving mono‐jogs and of the concentration of excess point defects during plastic deformation has been solved asymptotically as well as numerically. The jog density is a linear function of strain, resulting in a temperature dependent contribution to work‐hardening. The excess point defect concentration reaches a steady state value in a constant strain rate experiment and should be caused by interstitials. The results are discussed in terms of the plastic properties in stage I deformation of alkali halides.
Nuclear relaxation and NMR saturation in a crystal with a magnetic impurity
Authors: Buishvili L. L. , Khutsishvili G. R. , Zviadadze M. D. 
Published: July 2007

AbstractA theoretical treatment of nuclear relaxation in non‐metallic diamagnetic crystals with a magnetic impurity is carried out for the case when the dipole—dipole reservoir of magnetic ions plays an important role. The theoretical results are compared with the data of the Leiden group on relaxation of protons in lanthanum magnesium nitrate with neodymium impurities. An elementary theory of NMR saturation is given taking into account saturation transfer from the nuclear Zeeman reservoir to the dipole‐dipole reservoir of magnetic ions. A special analysis is made of the possible role in nuclear relaxation of an inhomogeneous broadening of the EPR line, of a phonon bottleneck in the spin‐lattice relaxation of magnetic ions, and of exchange pairs.