bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature and concentration dependence of the electric field gradient in the cadmium‐magnesium alloy system
Authors: De U. , Hoph S. , Witthuhn W. 
Published: July 2007

AbstractThe quadrupole coupling constant, eQVzz/h, for 111Cd probe nuclei in CdxMg1−x, alloys (x = 0.0 to 1.0) is measured as a function of temperature and composition, using the time differential perturbed angular correlation technique. The observed temperature dependence of the electric field gradient (EFG), Vzz can be described by a T3/2‐relation for each of the compositions studied, except in the cases where phase transformations take place. From the measured concentration dependence of the EFG in the disordered h.c.p. phase of the alloy with lattice constants c and a, plots for the variation of a3(eQVzz/h) with c/a are made at different temperatures. These experimental results are discussed, using a theory of the EFG in metals, which predicts such a plot to belinear.
Planar channeling trajectories in diamond and silicon
Authors: Roosendaal H. E. , Schmiedeskamp B. , Hubbes H. H. , Lutz H. O. 
Published: July 2007

AbstractPlanar channeling backscattering spectra of 230 keV protons in silicon and diamond, and of 350keV He ions in silicon have been measured. The half wavelengths and the average stopping power of ions oscillating between the crystal planes with an amplitude of half the planar spacing are determined. For the half wavelengths agreement is obtained with theoretical calculations. The average stopping power of the ions considered turns out to be roughly 50% larger than the random stopping power.
Excitation mechanisms and excited states of the I1 bound exciton in CdS
Authors: Baumert R. , Gutowski J. 
Published: July 2007

AbstractFor the neutral‐acceptor‐bound exciton emission (I1) of CdS three new excitation lines with light E ⟂ c are found at 1.2, 2.5, and 3.7 meV on the high energy side of the I1 line. The nearest one is interpreted as due to the simultaneous excitation of the bound exciton and a transverse‐acoustic phonon. The other two are understood as the direct creation of the I1 bound exciton in excited states with one of the equal holes belonging to a higher configuration. With light E ‖ c the excitation mechanisms via the free exciton states AL and AF and the bound exciton states I1B and I1B are discussed. An excitation intensity dependent energy shift of the long wavelength tail of the band edge is reported for the first time.
Fonctions optiques d'une couche mince de sulfure de mercure
Authors: Debiais G. 
Published: July 2007

AbstractUne méthode de calcul des constantes optiques relative aux couches minces est analysée et appliquée à une couche de sulfure de mercure renfermant 50% de cinabre (α‐HgS) et 50% de méta cinabre (β‐HgS). Nous calculons les fonctions optiques et les frbquences des modes dans l'infrarouge entre 4000 et 250 cm−1 et observons l'influence respective des deux formes sur ces résultats.
The electronic theory of the alloy systems composed of alkali metal elements. I. Bulk properties of CsK, CsRb, and RbK solid solutions
Authors: Soma T. , Matsuo H. , Kohbu Y. 
Published: July 2007

AbstractA local Heine‐Abarenkov model potential of the pseudo alloy atom is proposed for the CsK, CsRb, and RbK alloy systems. Two parameters are determined by satisfying the zero pressure condition and Vegard's law for the pseudo ion core radius. The total binding energies and bulk modulus are calculated as a function of alloy compositions.
133Cs Quadrupole Perturbed NMR Study of Jahn‐Teller Phase Transitions in CsCuCl32)
Authors: Corti M. , Rigamonti A. , Magistris A. 
Published: July 2007

Abstract133Cs nuclear spin‐lattice relaxation measurements in CsCuCl3, in the temperature range 100 to 700 K, and an analysis of the first‐order static quadrupole effects on the NMR levels, are reported. Some data regarding the dc conductivity and the dielectric constant are mentioned and briefly discussed. Interesting insights in the static and dynamical properties of CsCuCI3, around the 418 K phase transition to the helical electric dipole structure driven by the cooperative Jahn‐Teller effect are obtained. The 133Cs spin‐lattice relaxation is driven by the fluctuations of the dipolar magnetic field from the Cu2+ ion and its temperature dependence is interpreted in the light of the properties of the electronic spin dynamics in presence of crystalline field effects.
The Influence of the Electric Field on the Electron Capture Coefficient of Screened Coulomb Centres
Authors: Olejníkoná B. 
Published: July 2007

AbstractThe method of Abakumov et al. who dealt with the evaluation of the lifetime of carriers in the field of Coulomb attractive centres in a strong electric field is applied here for a calculation of the field‐induced change of the capture coefficient of screened Coulomb centres. The use of a computer enables to study the field dependence in a broad interval of electric fields without restriction to weak or strong ones. The calculated values are compared with results of previous paper obtained by the method of Dussel and Boer. Results given by these two different approaches differ considerably in both the magnitude and the shape of functional dependence.
The Pseudopotential Method and Thermodynamics of Eutectic Systems
Authors: Landa A. I. , Panin V. E. , Zhorovkov M. F. 
Published: July 2007

AbstractThe pseudopotential method and the thermodynamic perturbation theory are applied to construct the phase diagram of the eutectic system Cd‐Zn. The Einstein model approximation in the solid phase and the hard sphere approximation in the liquid phase are chosen as reference systems. Satisfactory agreement of the calculated phase separation curves with experimental data is observed. A correlation between the position of the phase separation curves and the thermodynamic characteristics of the components is found. An analysis of the contributions to the mixing energy is made, and the correlation between the mixing energy and the mixing volume is established.
Infrared and Raman Spectra of Germanium Dichaleogenides(II). GeSe2
Authors: Popoviá Z. V. , Stolz H. J. 
Published: July 2007

AbstractPolarised Raman spectra at 300 and 4.2 K as well as IR reflectivity and transmission spectra of single crystal GeSe2 are obtained and analysed with the help of a factor group analysis. The IR reflectivity data are analysed with a Kramers‐Kronig analysis and by means of an oscillator fitting procedure. The results obtained are discussed in terms of the analogy between the vibrational spectra of GeS2 (Part I) and GeSe2.
Luminescence et résonance paramagnétique de l'ion Mn2+ dans le luminophore MgS
Authors: Asano S. , Yamashita N. , Nakao Y. , Matsushima Y. 
Published: July 2007

AbstractESR spectra and emission and excitation spectra of the MgS:Mn2+ phosphor are measured at 6, 80, and 300 K. From ESR spectra the values of the parameters g and A are obtained: g = 2.0019 and A = −74.8 × 10−4 cm−1 at 300 K. Furthermore, the analysis of the excitation spectra leads to the values B = 631 cm−1, C = 3345 cm−1, and Dq = 817 cm−1 with covalency parameter ϵ = 0.044. The value of the cubic field parameter a estimated from the shape of ESR spectra is much smaller than that theoretically deduced from the observed value of the parameter Dq.
Investigation of the XPS Valence Band Structure from Sn Chalcogenides
Authors: Berg U. , Chassé T. , Brümmer O. 
Published: July 2007

AbstractXPS valence band spectra reflect the electronic density of states weighted with cross‐sections. The spectra will give additional information about the symmetry of the electron wave function, if they are measured in dependence on the electron emission angles. Valence band spectra of SnS, SnSe, SnTe, and SnS2 are measured partly in dependence on the polar angle θ. These measurements allow an identification of the symmetry of valence orbitals from intensity variations of the valence band maxima.
Shift in the Binding Energy of the Inner Electrons Due to Chemical Combination
Authors: Srivastava K. S. , Husain M. , Gupta P. , Srivastava A. K. , Sinha K. , Singh S. , Kumar V. 
Published: July 2007

AbstractThe numerical order of the chemical shift of an X‐ray absorption edge of a metal when it undergoes a chemical combination and forms a compound is calculated by calculating the binding energy shift of the core electrons. It is found that the shift in the binding energy corresponds well with the chemical shift.
Theory of the Auger Spectra of Narrow‐Band Metals with Impurities
Authors: Drchal V. , Kudrnovský J. 
Published: July 2007

AbstractThe intraatomic CVV Auger spectrum for a single impurity in a perfect crystal with an initially filled band is investigated. The impurity is characterized by its atomic level Δ and the contact pair interaction U of electrons (Wolff‐Clogston model). The exact solution of the problem is found. The spectrum may consist of three parts: (i) band of the two‐hole extended states, (ii) isolated localized two‐hole states, and (iii) band of mixed two‐hole states, in which one hole is localized, and the other one is in an extended state. The band of extended states is present in all cases, the localized and mixed states appear simultaneously for a certain value of |Δ|. The condition for the existence of bound states is derived, and the theory is numerically illustrated for a simple bandstructure model.
EPR Observation of an Au–Fe Complex in Silicon. II. Electronic Structure
Authors: Sieverts E. G. , Muller S. H. , Ammerlaan C. A. J. , Kleinhenz R. L. , Corbett J. W. 
Published: July 2007

AbstractFor a description of the Au–Fe complex which is discussed in Part I of this article, a model by Ludwig and Woodbury is adopted. This model does not allow for an analysis of the observed hyperfine interactions in a simple LCAO description. Instead a model of exchange coupled spins is proposed. The calculated actual hyperfine interactions are compared with data of atomic wave functions for Au and Fe. Due to covalency and/or hybridization effects the quantities 〈r−3〉d which characterize the d‐orbitals on the Fe and Au atoms are considerably reduced in silicon with respect to the free atoms. As a result, the s‐core polarization effects which determine the isotropic hyperfine interactions are found to be weaker in a silicon matrix than in most other materials.
Change in Electron Mass and Collision Frequency Due to Acoustic Wave Propagation in Piezoelectric Semiconductors
Authors: Palanichamy P. , Singh S. P. 
Published: July 2007

AbstractA phenomenological theory is developed to study the relative change in electron mass and collision frequency when an acoustic wave propagates through piezoelectric semiconductors. The results show that the change in collision frequency is more than that in electron mass for all acoustic wave frequencies in n‐CdS, and is more appreciable at lower temperatures.
Inverse Problem in Mössbauer Spectroscopy in Case of Low‐Frequency Modulation
Authors: Nadjaryan G. N. , Gabrielyan R. G. , Nkrtchyan A. R. , Khanamiryan R. M. 
Published: July 2007

AbstractInvestigations are made to determine the type (time dependence) and parameters of external low frequency excitations on the basis of Mössbauer absorption spectra (inverse problem). On the basis of the performed analysis the paper suggests a numerical method for solving this problem. The type of velocity and extreme values of oscillations of two types are determined by this method.
A Refined Equation of State for Monovalent Metals
Authors: Goel S. C. , Nanda V. S. 
Published: July 2007

AbstractA refined equation of state for monovalent metals based on a quantum mechanical version of the cell model is given. Here not only the contribution of free electrons to the equation of state is taken into account but also to a first approximation the effect of anharmonicity of the cell potential is included. The latter refinement results in a considerably improved agreement between theory and experiment.
Model Hamiltonian Wannier Functions
Authors: Craig B. I. , Smith P. V. 
Published: July 2007

AbstractMany theoretical approaches to the problem of defects and impurities in an otherwise perfect lattice require the existence of well localized basis functions on each lattice site, the so‐called Wannier functions. The construction of such Wannier functions from a model Hamiltonian representation of the host metal bandstructure is discussed and the dependence of the degree of localization of these functions on both the choice of phase factors and the constraints of orthogonality examined. The value of such functions in providing an adequate set of basis functions is also critically examined for several systems of physical interest.
On a New Photogalvanic Effect Due to Free‐Carrier Absorption
Authors: Henneberger F. , Averkiev N. S. , Rasulov R. J. 
Published: July 2007

AbstractA new photocurrent induced by optical orientation of free carriers under intraband absorption is theoretically investigated. Using a one‐band model it is shown that this current originates from interferences between harmonic and anharmonic processes of the electron–phonon interaction. A general expression for the current is derived for both, linear and circular polarized light. As an example the temperature dependence of the current is calculated for tellurium.
Electronic Properties of the TI–AgTITe2 System in the Liquid State
Authors: Uemura O. , Itoh M. , Satow T. 
Published: July 2007

AbstractThe electrical conductivity, the magnetic susceptibility, and the thermoelectric power of the liquid TI–AgTITe2 system are measured as a function of temperature and composition. The temperature coefficient of electrical conductivity and magnetic susceptibility in the concentration range from pure AgTITe2 to 66.7 mol% TI decreases gradually with increasing TI concentration. The alloys in the vicinity of 66.7 mol% TI have a weak temperature‐dependent conductivity and diamagnetism at low temperature but above 700°C both quantities of these alloys vary strongly with temperature. The electrical conductivity indicates a deep minimum and the diamagnetic susceptibility gives a sharp maximum at 66.7 mol% TI, while the thermoelectric power changes its sign around this composition. These results suggest that the state density of electrons has a minimum at the composition corresponding to AgTI3Te2 (66.7 mol% TI) and a metal–semiconductor transition as found for the liquid TI‐Te system also occurs in this system. The electronic properties obtained are discussed in terms of the current diffusive transport model for liquid semiconductors.
Infrared Absorption Spectra of Eu‐Rich EuO. Excitations of the Bound Magnetic Polaron
Authors: Lascaray J. P. , Diouri J. , Nadai J. P. , Ferre J. 
Published: July 2007

AbstractTwo typical absorption bands of Eu‐rich EuO, located around 0.56 and 0.67 eV are studied in the temperature range 20 to 270 K. The results and previous data cannot be explained satisfactorily by the two models reported in the literature: i) excitations of electrons localized into F+ centers, ii) optical transition involving a spin‐flip process of the electron of the bound magnetic polaron. An improved, more refined description of the previous interpretation is proposed for which absorption bands are due to optical transitions inside the 5d (t2g) levels split by the spin–orbit coupling and the exchange interaction.
Random Site Ising Model in Self‐Avoiding Walk Approximation
Authors: Medvedev M. V. , Sadovskii M. V. 
Published: July 2007

AbstractThe free energy of random site Ising model with competing exchange interactions of nearest neighbours is studied with the use of high‐temperature expansions in the self‐avoiding walk approximation. Conditions for the instability of the paramagnetic state are determined by the convergence criterion of the random high‐temperature series. The possibility of a concentration interval with the absence of the long‐range magnetic order is studied for different 2d and 3d lattices.
Lattice Constant Fluctuations in Anharmonic Crystals
Authors: Wojtczak L. , Siklós T. , Mrygon B. , Mielnicki J. 
Published: July 2007

AbstractA model of lattice constant fluctuations in crystals is discussed in self‐consistent phonon theory. The influence of fluctuations on the mean square displacement of atoms from their equilibrium position is considered. The fluctuation effects connected with correlations are also included.
Photoemission Study of Oxygen Adsorbed on Sputtered a‐Si(H) and a‐Si
Authors: Cháb V. , Zemek J. , Koc S. , Mikušík P. 
Published: July 2007

AbstractThe electronic structure of natural oxide layers and of oxygen adsorbed on the surface of sputtered a‐Si and a‐Si(H) thin films are investigated by combining ultraviolet photoemission spectroscopy and X‐ray photoemission spectroscopy. The emission structure in the valence band region which is derived from the oxygen and silicon orbitals, is found to represent the nondissociative adsorption of oxygen on a‐Si(H) surface independently of hydrogen content. XPS study of Si2s and Si2p core levels shows a minimally 0.3 eV smaller value of the chemical shift in the case of naturally oxidized a‐Si(H) and a‐Si films than the value measured on c‐Si oxidized under the same conditions. The ion‐beam effect on oxide layers is briefly discussed.
The Heat Capacity of Nb3SnHxin Dependence on the Hydrogen Content
Authors: Shamrai V. , Bohmhammel K. , Wolf G. 
Published: July 2007

AbstractInvestigations of the heat capacity on Nb3SnHxsamples (0 ≦x≦ 1.0) in the temperature range from 2 to 30 K are communicated. A strong decrease ofTcand γ is observed experimentally with risingxvalue. The change of the density of states near the Fermi level and the electron‐phonon interaction parameter in dependence onxare determined. The discussion of the change in the properties considers the possibility of the formation of H–Nb bonding states and the position of the H‐atoms near to the crossing point of the Nb‐chains in the A15‐structure.
Spin–Orbit Interaction in Superexchange with Orbital Degeneracy II. Effective Tensor Hamiltonian
Authors: Blaszak M. 
Published: July 2007

AbstractMethods of irreducible tensor algebra for a chain SU2 → O* are applied to determine the effective tensor Hamiltonian of superexchange with orbital degeneracy with the spin–orbit interaction on magnetic ions assumed. The parameters of each Hamiltonian are calculated in quasi‐diagonal approximation.
Dynamics of Two‐Spin Cluster in Spin Glass II. The Magnetization Process at T = 0
Authors: Nara S. , Heber G. 
Published: July 2007

AbstractBased on the simple two‐spin cluster model of spin glass, the magnetization process at T = 0 is investigated. An ensemble of clusters is considered consisting of two Heisenberg spins in the external field and two kinds of molecular field which are called “homogeneous molecular field” and “inhomogeneous molecular field” created by inter‐cluster interactions. The spin quantum number is taken as S1 = S2 = 1/2 for conveniency. It is shown that this model qualitatively can well describe the S‐shape like magnetization process and hysteresis loops of several substances which are measured at very low temperature (T ⩽ Tf). Also special cases are found of unstable magnetization changes which in reality will be smeared out.
Photoconductivity of Lead(II)‐ and Cadmium (II)‐Doped Silver Bromide
Authors: Deri R. J. , Haynam Ch. , Spoonhower J. P. 
Published: July 2007

AbstractThe photoresponse of AgBr binderless powder precipitates doped with Pb2+ and Cd2+ ions is studied near liquid‐nitrogen temperature by using microwave cavity techniques. Pb2+‐ and Cd2+‐doped samples have much longer photoelectron lifetimes and higher peak photoelectron signals than undoped samples. The decay kinetics of the doped samples appears to consist of the superposition of two first‐order processes. The temperature dependence of the kinetics is established to follow the Arrhenius model, and activation energies are deduced. The data are interpreted in terms of “impurity conductivity” caused by photoelectrons trapped by the Pb2+/Cd2+ dopants and the migration of silver‐ion interstitials.
Thermal Noise, Diffusion, and the Mobility of Hot Holes in Silicon
Authors: Bosman G. , Zijlstra R. J. J. 
Published: July 2007

AbstractThe longitudinal diffusion coefficient and the mobility of holes in silicon are calculated as a function of electric field strength from noise and conduction measurements on p+ πp+ planar silicon devices at T = 100, 145, and 210 K. The electric field is oriented along the 〈100〉 direction. The results obtained for the longitudinal diffusion coefficient at T = 100 and 145 K show that both light and heavy holes contribute to charge transport. The values found for the mobility agree very well with those which Ottaviani et al. obtained using the time‐of‐flight technique.
On the Phonon Contribution to the Electrical Resistivity of Intermediate Valence Systems
Authors: Christoph V. 
Published: July 2007

AbstractThe electrical resistivity of an electron–phonon system with two hybridized tight‐binding electron bands is calculated. The electron–electron interaction is taken into account in the Hartree‐Fock approximation leading to an occupation dependent narrowing of the bands. The influence of the effective band width on the resistivity is discussed.
Mössbauer Isomer Shifts of 40K+ in KF, KCl, and KBr Lattices
Authors: Bansal C. , Shrivastava K. N. 
Published: July 2007

AbstractCharge densities at 40K+ in KF, KCl, and KBr lattices are calculated from Hartree‐Fock wavefunctions including the effect of overlap of core orbitals with the neighboring atoms. From the calculation of KF and KCl and the experimental measurements of Mössbauer centre of gravity shifts we estimate the relative change in nuclear charge radius upon emission of 29.4 keV γ‐radiation to be in the limits of −6 × 10−4 ≦δ<r2>/<r2> ≦ 31 × 10−4.
Magnetic States of a Quenched Random Site Heisenberg Magnet with Competitive Exchange Interactions. I. High‐Temperature Magnetic States in Simple and Body‐Centered Cubic Lattices
Authors: Medvedev M. V. , Zaborov A. V. 
Published: July 2007

AbstractFor a quenched random site Heisenberg system with competitive nearest‐neighbour exchange interactions (IAA > 0, IAB ≶0, and IBB < 0) the molecular field distribution functions of various random magnetic structures are derived in the approximation of large nearest‐neighbour number z (z >> 1). The obtained distribution functions are utilized to discuss magnets with simple (s.c.) and body‐centered cubic (b.c.c.) lattices. It is shown that at high temperatures random collinear ferromagnetic and antiferromagnetic states (and a canted structure as well) can occur at the transition from the paramagnetic state. The occurrence of a spin‐glass state in s.c. and b.c.c. lattices at high temperatures is scarcely probable even in the framework of the molecular field approximation (MFA).
Investigation of the Charge Carrier Scattering in Bi under High Hydrostatic Pressure
Authors: Kraak W. , Herrmann R. , Haupt H. 
Published: July 2007

AbstractA detailed and precise measurement is given of the temperature dependence of the electrical resistivity of bismuth in the temperature range 2 K < T < 77 K. Under high hydrostatic pressure the Fermi energy is varied over a wide range. From the obtained temperature dependence of the electrical resistivity – a linear dependence for temperatures > 20 K and a T2 dependence at lower temperatures – as well as the characteristic dependence of the strength of the linear and quadratic terms from the electron Fermi energy, it is suggested that at temperatures > 20 K the resistivity is dominated by electron–phonon scattering, however, at lower temperatures a contribution due to carrier–carrier scattering may be significant.
Long‐Wave Secondary Radiation in Polar Semiconductors as a Function of Temperature
Authors: Giner C. Trallero 
Published: July 2007

AbstractThe long‐wave secondary radiation in direct‐band polar semiconductors is investigated. The secondary radiation cross‐section is calculated as a function of the incident, ω1, and emitted, ωs, light frequencies and the temperature T. It is shown that for arbitrary temperature values the cross‐section is of a step‐like shape and new thresholds appear relative to T = 0 K.