bluuebunny/crossref_metadata_2025_split huggingface dataset:
Size Effect and Temperature Dependence of the Electrical Resistance in Bismuth Single Crystals of High Perfection
Authors: Kraak W. , Kuhl R. , Thom F. , Haefner H. , Schmidt P. 
Published: July 2007

AbstractBi single crystals of high perfection (having extremely high resistance ratios r4.2 = ϱ290 K/ϱ4.2 K) are grown by the mould growing method. In these crystals, the thickness dependence of the resistance ratio r4.2 and the temperature dependence of the electrical resistance are investigated in a temperature range between 2 and 77 K. In the range of the diffusion size effect, a markedly different behaviour is found to occur in the thickness dependence of the two crystal orientations investigated (j ‖ C3; j ‖ C2). An anisotropy of the slope of the T2‐terms is detected in the temperature dependences of the electrical resistance in the temperature interval from 2 to 16 K.
Role of Free Electrons and Holes in the Exciton Condensation Process in Semiconductors
Authors: Ashkinadze B. M. 
Published: July 2007

AbstractAn experimental study of hysteresis in the luminescence of electron—hole drops in Ge upon the action of a magnetic field is presented. In the magnetic field the free electron and hole flows onto a drop decrease. This results in an increase of the nucleation rate of the drops and also the decrease of the drop radius. The principal experimental results are: 1) The threshold phase diagram obtained in the presence of magnetic field is different from that for H = 0; 2) the new hysteresis loop is found on varying the magnetic field; 3) the contribution from free carrier current in the stationary drop radius is determined and it follows that the value of the cross‐section for the exciton formation process is of the order of 2 × 10−11 cm2.
Non‐Linear Optical Properties of the Degenerate Band Charge Carrier Gas
Authors: Klymin S. N. , Pokatilov E. P. 
Published: July 2007

AbstractA theory of non‐linear optical properties of a band charge carrier gas of arbitrary degeneracy due to the influence of a strong electromagnetic radiation on the probability of the carrier scattering by phonons or ionized impurities leading to intraband transitions is developed. A general expression for the polarization created by the carrier response in a laser field in the presence of other electromagnetic fields is obtained at arbitrary temperature and concentration of carriers. The explicit expressions for a generalized dielectric susceptibility tensor and a generalized generation tensor are obtained for all principal scattering mechanisms and arbitrary laser field intensity. The non‐linearity of the absorption coefficient of laser radiation and the dependence of the absorption coefficient of the weak probe wave on the intensity of the laser field are studied.
The Fundamental Absorption Edge of MgSiP2
Authors: Ambrazevičius G. , Babonas G. , Rud Yu. V. , Šileika A. 
Published: July 2007

AbstractThe absorption and wavelength‐modulated absorption spectra of MgSiP2 single crystals are investigated in the region of the fundamental absorption edge at 4.2, 77, and 300 K and under hydrostatic pressures up to 770 MPa. MgSiP2 is determined to be a pseudodirect bandgap compound with a forbidden energy gap of 2.409, 2.404, and 2.33 eV at 4.2, 77, and 300 K, respectively. The pressure coefficient of the absorption edge is −2 × 10−5 eV MPa−1. The spin‐orbit splitting at the top of the valence band of MgSiP2 is close to that for phosphides of the AIIBIVCV2 type. The crystal‐field splitting of the higher valence band is proposed to be negative.
Acceptor Bound Exciton States in High‐Purity CuCl
Authors: Sauder T. , Stébé B. , Certier M. 
Published: July 2007

AbstractThe magneto‐optical properties of high‐purity CuCl at 4.2 K show that the two lines ν½ (25665.2 cm−1) and ν (25697.6 cm−1) are due to transitions to (or from) excitons bound to the same neutral acceptor, the two holes arising from the lowest Γ8 valence band. They are attributed, respectively, to the J = 5/5 and J = 1/2 states of the (A0, X) complex. These results are explained by the importance of the electron—hole exchange interaction and by a dominant occurrence of the Γ8 rather than the Γ7 neutral acceptors. As a consequence, free holes should chiefly arise from the Γ7 valence band. This is due to the particularly low value of the valence band spin—orbit splitting (ΔSO ≈ 600 cm−1), compared to the free‐exciton binding energy (EX ≈ 1523 cm−1) or to the estimated Γ7 acceptor ionization energy (EX ≈ 17000 cm−1). These conclusions support the previous assignment of line ν2 (25654 cm−1) to a transition between a free Γ7 hole and a Γ6 charged exciton X.
Diffusion of Interstitial Solute in a Potential Well Characteristic of a Moving Dislocation
Authors: Fuentes‐Samaniego R. , Hirth J. P. 
Published: July 2007

AbstractThe equation governing the flux of interstitial solute near a moving dislocation is found. Such an equation is non‐linear, a feature which allows for the realistic situation that the solute concentration is bounded by the concentration of interstitial sites. However, in order to find analytical solutions, the alternative of a two‐dimensional, symmetric potential well characteristic of the dislocation is considered. Analytical determination of the properties of such a potential well as either a trap or a carrier of interstitial solute is made. The solute drag force‐velocity curves for the steady‐state motion of a potential well are obtained.
Thermal Conductivity of a Crystal with Impurities of Internal Degrees of Freedom
Authors: Segal A. 
Published: July 2007

AbstractThe thermal conductivity of a crystal with impurities with internal degrees of freedom is theoretically investigated using the double‐time Green's function methods and the Kubo formalism, considering non‐diagonal terms in the heat‐current operator as proposed by Hardy. Mass changes as well as impurity‐phonon interaction are taken into account explicitly. It is shown that the total conductivity can be written as a sum of two contributions: one diagonal and the other nondiagonal. An expression for the inverse relaxation time is obtained and compared with that deduced from the Callaway theory.
Non‐Linear Fluorescence Quenching in Molecular Crystals. III. Recombination of Static Excitations
Authors: Benderskii V. A. , Brikenshtein V. Kh. , Filippov P. G. , Shamovskii I. A. 
Published: July 2007

AbstractNon‐linear quenching of the excimer fluorescence of pyrene crystals is investigated. The transition between diffusing (T > 150 K) and static excitation (T < 70 K) affects the relationship between the quantum yield of fluorescence Φ and pumping I (from Φ ∞ I−1/2 to Φ ∞ I−2/3 at high I, respectively), and the shape of its initial decreasing portion L (from L ∞ t−1 to L ∞ t−1/2 for a δ‐pulse of pumping). The rate constant of bimolecular excimer recombination γ is (5 × × 1.5) × 10−11 cm3 s−1 at 300 K and decreases exponentially with temperature in correspondence with the decreasing diffusion. The Förster radius R0 corresponding to the measured value of γ is 30 Å and agrees well with the value calculated from the spectral overlap. It is shown that the low‐temperature non‐linear quenching is described quantitatively by the static dipole—dipole excitation recombination model with approximate allowance for the three‐particle correlations. Allowance for higher order correlations is found to be insignificant up to the maximum experimentally attainable excitation density n corresponding to (4π/3) Rn ≈ 8.
Influence of Ni Impurity on the Absorption Spectrum of Layered GaSe Crystals
Authors: Gnatenko Yu. P. , Kovalyuk Z. D. , Skubenko P. A. 
Published: July 2007

AbstractAbsorption spectra of the layer crystal GaSe doped with Ni of different concentrations (0.5, 0.1, 0.05, and 0.01%) are investigated in the temperature range 4.2 to 300 K. In the region 1.5 to 2.0 eV an impurity absorption due to intra‐centre transitions between the 3F and 3P states of the ion Ni is revealed. The energies of phonons participating in the absorption and an intermediate type of electron‐phonon interaction in GaSe are determined. The observed doublet structure can be attributed to the Jahn‐Teller effect for the excited state.
A New Method to Determine the Coupled Mode Parameters of a Plasmon‐Multiphonon System
Authors: Gelten M. J. , Bosch L. A. 
Published: July 2007

AbstractA new (numerical) method is described to determine all coupled mode parameters of a complex plasmon‐phonon system in a semiconductor. First a general theoretical description is given of the complex dielectric function describing such a system. Some paractically important relations are deduced. Starting from an experimentally determined reflectivity spectrum, the dielectric function is determined at a number of discreate frequencies by means of Kramers‐Kronig analysis. A complete background is given for a numerical method to determine all relevant mode parameters, especially the coordinates of poles and zeros in the complex frequency plane, from this spectrum. Finally the new method is applied to a test spectrum. The results are discussed and compared with those of other methods.
Thermodynamic Properties of Liquid Metals and Alloys
Authors: Khanna K. N. , Khandelwal D. P. 
Published: July 2007

AbstractAn analysis of thermodynamical properties, such as excess entropy, softness of the constituent pseudoatoms, and specific heat, is presented for liquid metals and alloys in the hard sphere reference system. The formalism, based on the concentration and excess volume dependent hard‐sphere behaviour, provides a basis for microscopic understanding of the thermodynamics of alloys.
Resonant photon–photon scattering and approximate spherical symmetry in CuCl
Authors: Van Hieu Nguyen 
Published: July 2007

AbstractIt is shown that if the contribution of the holes in the lower valence bands Γ8 in CuCl is neglected, the state vectors of the stationary states of the excitons and hiexcitons in this semiconductor belong to irreducible representations of the rotation group, and their interaction is spherically symmetric. Due to this approximate symmetry, the partial wave expansion may be applied to the photon‐photon scattering amplitude and the angular dependence of the cross‐section of the resonant scattering via a definite biexciton state may be predicted.
Helium desorption from a tungsten single crystal
Authors: Mhaskar S. P. , Naik P. K. 
Published: July 2007

AbstractEntrapment of helium in molybdenum and tungsten has been investigated both theoretically and experimentally in detail in the past. In general, peaks observed in the thermal desorption spectra of helium are related to the detrapping reactions of helium from HenV (n = 1 to 4) complexes. A computer programme is developed to simulate the activation energies of these detrapping reactions in the bulk of the solid and in the vicinity of the crystal surface. Experimental values of the activation energies of these reactions reported earlier by Kornelsen show good agreement with the values calculated for the same reactions occurring in the bulk. Values calculated for these reactions near the surface are much lower than the experimental values. It is further shown that an agreement between the experimental and the calculated values of activation energies for the surface reactions is possible only if the entrapment is made to occur near the surface.
Damping of acoustic modes in one‐dimensional systems
Authors: Rowlands G. 
Published: July 2007

AbstractThe propagation of long‐wavelength disturbances in a 1D lattice with N atoms per unit cell is considered. The appropriate value of the sound velocity is obtained. It is shown that for N sufficiently large such disturbances will be damped, and an expression for the damping rate is given. The analysis is made applicable to disordered systems by considering the limit N = ∞).
Local susceptibility calculation for intermediate‐valence solids
Authors: Schlottmann P. , Falicov L. M. 
Published: July 2007

AbstractA calculation of the local susceptibility of an intermediate‐valence solid is presented. The mode which resembles some thulium salts, consists of an ionic doublet (with n electrons) or an ionilc triplet (with (n + 1) electrons) and a variable number of electrons in a “conduction” band. Hybridization is fully taken into account locally. The calculation is performed in the micro‐grand‐canonical ensemble. Both a Curie‐ and a Van‐Vleck‐type susceptibilities are found. The contributions from doublet, triplet, and itinerant electrons and their interferences are analyzed. Under some conditions it is found that the hybridized intermediate‐valence compound has a lower effective magnetic moment than both the doublet and the triplet.
Die Bestimmung der Valenzladungsdichte von Elementhalbleitern und III–V‐Verbindungen mit Röntgenbeugungsmethoden. I. Grundlagen
Authors: Brühl H. G. 
Published: July 2007

AbstractEinige Methoden zur Berechnung der Valenzelektronendichte an Elementhalbleitern und III‐V‐ Verbindungen werden vorgestellt. Eine kurze Diskussion der Voraussetzungen für die Anwendbarkeit der Modelle und der erreichbaren Aussagen erfolgt. Die angeführten Methoden sind nicht gleichermaßen für die Diamant‐ und Zinkblendestruktur geeignet. Eine ausführliche Beschreibung des Tetraeder‐Deformations‐Modells (TDM) schließt sich an. Der Strukturfaktor |F| wird in erster Näherung für die Zinkblendestruktur abgeleitet. Die Valenzelektronendichte kann für einen beliebigen Punkt der Elementarzelle berechnet werden. Die Vor‐und Nachteile des TDM‐ Modells werden diskutiert.
On the equivalence of different approximations in linear electron transport theory
Authors: Van Royen J. , Beleznay F. , Devreese J. T. 
Published: July 2007

AbstractA critical comparison is made of different methods to obtain the mobility in linear electron transport theory. An approximation to the Kubo formula is studied, a calculation based on the displaced Maxwellian distribution function, and a method introduced in path integral calculations. It is shown that the three methods are equivalent: they lead to the same resistance in the weak scattering limit, for small electric fields. Special attention is given to the weak coupling Frohlich polaron mobility.
On self‐deconvolutions in Auger spectroscopy
Authors: Bartoš I. , Máca F. 
Published: July 2007

AbstractTwo self‐deconvolution procedures are discussed in the context of CVV Auger processes and their stabilities with respect to signal distortions from self‐convoluted forms are tested. In the sequential method the results are highly sensitive to random fluctuations in general, and especially at the edge of spectra; the reverse run starting at the low‐energy end is often useful in handling the data. The Fourier transformation method, being a global one, is far less sensitive to the above‐mentioned distortions; the resulting increased bandwidths can be suppressed by proper corrections.
Electron transfer within F center pairs in KCl from optical emission and absorption
Authors: Mezger A. C. , Jaccard C. 
Published: July 2007

AbstractTransient F luminescence and F′ population after F band excitation and the effect of a static magnetic field (0.5 T) are measured in KCl at 10 K for F center concentrations between 5 × 1016 and 1 × 1018 cm−3. The results are explained by an F center pair model involving a radiative decay (time τr), direct and inverse non‐radiative electron transfers within the pair depending exponentially on the separation: τ = τ0 exp (r/λ), and a Poisson spatial distribution of the individual centers, with the following parameters: τr = (890 ± 5) ns; τ0 = (0.4 ± 0.2) ns, λ = (0.8 ± 0.1) nm (direct); τ0i = (2 ± 1) ms, λ′ = (0.8 ± 0.1) nm (inverse).
Force constant change of Mössbauer 119Sn impurity in copper host
Authors: Puri R. K. , Gupta L. R. 
Published: July 2007

AbstractThe temperature dependence of Mössbauer recoil‐free fraction of 119Sn atom, present as a dilute impurity in copper host, has been measured. The experimental data are analysed in terms of the moments, ω(−2), of the phonon frequency distribution of the 119Sn impurity atoms in the copper lattice to obtain the weighted mean frequency and characteristic temperature. The ratio of impurity‐host to host‐host force constant is found reduced to (0.61 ± 0.01) as calculated on the basis of the nearest‐neighbour central force model using Debye phonon frequency spectra.
A comparative study of the pseudopotentials for Cu, Ag, and Au
Authors: Idrees M. , Khwaja Farid A. , Razmi M. S. K. 
Published: July 2007

AbstractAn analysis of the pseudopotentials proposed for copper, silver, and gold is presented. Three tests based on the calculation of band gaps, liquid (molten) metal resistivities, and thermoelectric power are carried out. Numerical results obtained are compared with the corresponding experimental values. It is concluded that the pseudopotential of Borchi and De Gennaro is the only one giving some overall agreement with experiment. It is pointed out that the s‐d hybridization contribution in the Borchi‐De Gennaro pseudopotential needs to be suitably modified if closer agreement with experiment is to be achieved.
A Renormalization Group Approach for Randomly Distributed Conductance
Authors: Kazakov V. A. , Satanin A. M. 
Published: July 2007

AbstractThe recursion equation for the probability scaling behaviour of conductance for a randomly inhomogeneous resistive medium is obtained. The equation enables one to calculate percolation thresholds and a complete set of critical indices in the continuous percolation problem for which in a d‐dimensional space the following formulae are derived: t=v(d − 1), q = v, s = (d − 1)/d, m = (dv)−1. For the cubic lattice t = 1.23 in a two‐dimensional and t = 1.74 in a three‐dimensional space are obtained. The scaling behaviour of dispersion and of the mean value of the normal distribution near a homogeneous fixed point is found.
A New Interpretation of EXAFS Spectra in Real Space: II. A Comparison of the Regularization Technique with the Fourier Transformation Method
Authors: Ershov N. V. , Ageev A. L. , Vasin V. V. , Babanov Yu. A. 
Published: July 2007

AbstractThe errors in the initial EXAFS data are simulated numerically. The comparative sensitivity of the regular methods and of the Fourier transformation method to these errors is analyzed. The theoretically calculated normalized oscillating part of the absorption coefficient χ(k) for polycrystalline copper at T = 77.4 K is compared with the experimental spectrum obtained with the use of a synchrotron facility. The spectrum involved is processed using regular methods. A substantial improvement of the result in comparison with the Fourier method is shown.
Near‐Infrared d–d Transitions of NiI2, CdI2:Ni2+, and CoI2
Authors: Kuindersma S. R. , Boudewijn P. R. , Haas C. 
Published: July 2007

AbstractThe absorption spectra of NiI2, CdI2:Ni2+, and CoI2 in the wave‐number region 4000 to 16000 cm−1 are reported. The spectra are interpreted in terms of d‐d transitions of Ni2+ and Co2+ ions. Parameters of the electron repulsion, cubic crystal field, and spin‐orbit coupling are estimated. From the latter the transferred spin densities are deduced and compared with Mössbauer data. Birefringence experiments as a function of the temperature show the presence of two phase transitions in niI2.
Relativistic Effect on a Deformed Semi‐Infinite Crystalline Surface
Authors: Yuyi Shen 
Published: July 2007

AbstractThe deformed surface described by some parameters has been studied by Volkenstein [1] in 1947 and by Steslicka [2] in 1974 in the non‐relativistic case. In this paper, the study is extended to the relativistic case. When the parameters take certain values, the relativistic equations of the deformed surface correspond to the relaxation, segregation, or relaxation‐segregation case, respectively. When c → ∞, i.e. for the non‐relativistic limit, the equations will approach the results obtained by Steslicka.
Electron–Hole Plasma Expansion in Direct‐Gap GaAs1−xPx
Authors: Modesti S. , Frova A. , Staehli J. L. , Guzzi M. , Capizzi M. 
Published: July 2007

AbstractThe e‐h plasma in the ternary alloy GaAs1−xP2 below direct‐indirect crossover is studied at 2 K by means of very high excitation photoluminescence measurements. The most interesting feature observed is an extremely efficient expansion of the excited region when the particle density reaches the value n* needed to minimize the free energy. This behaviour and the corresponding spectral evolution with power density are accounted for by a model where pressure‐induced flow of particles away from the pumped region becomes competitive with recombination mechanisms.
Electronic State Calculations of Dislocations in Cadmium Telluride
Authors: Öberg S. 
Published: July 2007

AbstractUsing a tight binding method the localized electronic states in CdTe connected with the core of 30° and 90° glide partials are calculated. Periodic arrays of large unit cells each containing two 30° or 90° partials with Burgers vectors of opposite sign are considered. Several models of the core structure of each partial are analyzed. The electronic states of dissociated screw and 60° glide dislocations are discussed.
X‐Ray L1 Spectra and XPS Investigation of the Electronic Structure of Indium Compounds
Authors: Gusatinskii A. N. , Blokhin M. A. , Shumichen P. , Bunin M. A. , Mikhailova S. S. 
Published: July 2007

AbstractMetallic indium and some of its compounds with various types of chemical bonds are investigated by means of X‐ray and X‐ray photoelectron spectroscopy (XPS). In the first part of this work emission InLγ2,3‐lines (transition L1‐N2,3) and InN2,3 XPS are obtained. The splitting of the Lγ2,3‐ lines is detected for In and the spin‐doublet N2,3‐level parameters are measured. Furthermore the L1‐emission bands and L1‐absorption spectra are (apparently for the first time) used to obtain information on the band structure of some semiconductor compounds.
Changes of EPR Spectra by Inhomogeneous Plane Stress Distributions in a Two‐Layer System
Authors: Gehlhoff W. , Segsa K. H. 
Published: July 2007

AbstractThe influence of plane stress distributions on lineshapes and line positions of EPR transitions in a two‐layer system (film‐substrat) is investigated. Basing on previous calculations explicit expressions for the lineshape of EPR transitions are derived also for the case of an inhomogeneous stress distribution. The effects of homogeneous and inhomogeneous stress distributions on the EPR spectra of paramagnetic systems with S = 1 are represented. The possibility to confuse stressinduced changes of the lineshape with hyperfine and superhyperfine structures is demonstrated.
Small Wave Vector q and Frequency ω Dependent Longitudinal Dielectric Funtion for a Model Semiconductor
Authors: Sharma A. C. , Auluck S. 
Published: July 2007

AbstractA modified calculation of the small wave vector q and frequency ω dependent longitudinal di‐electric function for Milchev's model semiconductor is presented. To evaluate the matrix elements, two‐band wave functions are used instead of plane waves (as used by Milchev). The energy difference between the valence and conduction bands is taken to be the same as Milchev's. It is found that the general behaviour of the real and imaginary parts of the dielectric function ϵ1(q, ω) and ϵ2(q, ω) are similar to that found by Milchev and by Walter and Cohen using a realistic band structure. The static dielectric function ϵ1(q, 0) agrees well with the exact calculation of Walter and Cohen. ϵ(0,ω) accounts properly for the Kramers‐Kronig relation and up to a reasonable extent for the f‐sum rule. It is also in good agreement with optical data. For small q the plasmon dispersion is given by Ep(q) = Ep(0) + Aq2 where A is an analytical function of Δ = Eg/4EF where Eg is the energy gap parameter and EF the Fermi energy.