bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carrier drift mobilities in some organic solids. A search for organic photovoltaic materials. I. Charge transport calculations in 2–2′ bipyridine and pyridazino [4,5‐d] pridazine
Authors: Kumar B. 
Published: July 2007

AbstractExcess hole and excess electron mobilities are studied in 2–2′ bipyridine and pyridazino [4,5‐d] pridazine using tight binding approximation. With suitable molecular orbitals for band structure and using a potential given by Silbey et al. the energy bands are calculated. The applicability of band model and the suitability of these materials for organic photovoltaic devices are discussed in the light of existing theories.
Temperature dependence of structural and transport properties of less‐simple liquid metals
Authors: Rahman S. M. M. , Sarker D. K. 
Published: July 2007

AbstractShear viscosity and self‐diffusion coefficients are calculated for certain less‐simple liquid metals at various temperatures. The basic assumption undertaken is that these properties of a liquid metal resemble those of an appropriate hard sphere fluid. The temperature dependence of the basic ingredients, i.e. the hard sphere diameter and packing fraction is considered via a full thermodynamic perturbation formalism. The essential features inherited by these metals are included in the relevant electron‐ion interactions. A variational procedure leading to a minimization of the free energy is employed to determine the optimum values of the hard sphere diameters and packing fractions. These optimal and self‐consistent ingredients are employed in computing the shear viscosity and self‐diffusion coefficients of Ag, Hg, Ga, and Sn. The calculated results are found to be in agreement with the experimental and the available theoretical results for most of these metals.
Non‐linear optical susceptibilities of molecular crystals in the region of vibronie excitations. III. Non‐totally symmetric vibrations
Authors: Stoychev K. T. 
Published: July 2007

AbstractThe quadratic optical susceptibility of molecular crystals is calculated in the frequency region of vibronic excitations consisting of an electronic exciton and a non‐totally symmetric vibration. An one‐dimensional model with nearest‐neighbour interactions is used. Intermolecular and intramolecular exciton phonon interactions are considered and the former is shown to play a dominant role in nonlinear optical spectra. The sign of the exciton effective mass is shown to affect the spectrum inside the two‐particle exciton‐phonon band but not the bound state resonance.
Linearised screened pseudopotential and superconducting state parameters of a number of metals
Authors: Sharma R. , Sharma K. S. , Dass L. 
Published: July 2007

AbstractA linearised form for the screened form factors of electron‐ion interaction is proposed and applied for the prediction of superconducting state parameters viz. electron‐phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature Tc, isotope effect exponent α, and the interaction strength N0V. Good agreement between the computed results, experimental data, and the results of Allen and Cohen based on the HA potential, supports the proposition.
Symmetry analysis of the low‐temperature domain structure in ferroelastic LiKSO4
Authors: Balagurov A. M. , Popa N. C. , Savenko B. N. 
Published: July 2007

AbstractThe domain structure appearing in ferroelastic LiKSO4 at T < 190 K is analysed starting from the principle of macroscopic symmetry conservation. The transitions from, the point groups 6mm or 6 into mm2, 2, or 1 are considered in detail. It is shown that by the measurement of the split of reciprocal lattice node it is possible to determine the point group of the para‐ and ferroelastic phase in LiKSO4.
Effect of forced vibrations on the scattering of X‐rays and mössbauer radiation by a crystal. II. Dynamical effects
Authors: Dzyublik A. Ya. 
Published: July 2007

AbstractA dynamical theory for Raman scattering of γ‐quanta in crystals under forced vibrations is given. The pendellösung‐effect, the anomalous transmission of γ‐quanta through a crystal as well as suppression of inelastic scattering and reactions are shown to exist in the two‐wave case. A general theory of γ‐acoustic resonance for arbitrary geometry of Laue diffraction is developed. An anomalous transmission of Mössbauer radiation through a vibrating crystal far from the Bragg condition is predicted due to arising of electromagnetic wave packets in the crystal, which do not interact with nuclei.
Photon‐phonon interaction influence on the external vibration spectra of molecular crystals
Authors: Botvich A. N. , Shabanov V. F. , Vtyurin A. N. , Pozdnyakova T. A. 
Published: July 2007

AbstractA method is developed to determine the parameters of electromagnetic and elastic excitations in molecular crystals including the polariton resonance region. The dependence of eigenvectors and eigenfrequencies on the wavevector of elementary excitations is calculated numerically for m‐chloronitrobenzene crystals. The conditions are found when the photon‐phonon resonance effect becomes observable in the Raman scattering (RS) spectra of this crystal.
Surface states – an effect of overlap integrals
Authors: Stankiewicz Barbara 
Published: July 2007

AbstractThe effect of overlap integrals on the electronic structure of a simple cubic crystal is analysed using the LCAO method. Interaction between first, second, and third neighbours are taken into account. Surface and volume bands are determined. The width of energy bands as well as the number of surface states depend strongly on the value of overlap and resonance integrals. As a result, the location of the surface band with respect to the volume band is very sensitive to values of overlap integrals between nearest neighbours.
Magnetic Moments and Initial Susceptibilities of f‐Electron States Experiencing a Crystal Field of Cubic Symmetry
Authors: Fischer G. , Herr A. 
Published: July 2007

AbstractThe effect of perturbation to the second order caused by a magnetic field H on the energy levels of an f‐electron situated in a crystal field of cubic symmetry is calculated. This development is of particular interest in the understanding of magnetic properties of f‐electrons: the term in H gives the individual magnetic moment of the considered sub‐level and the term in H2 the corresponding Van Vleck susceptibility. The cases of H parallel respectively to the three principal crystallog‐ raphic directions are considered. The three terms of the energy development are tabulated for all J from 2 to 8 in the cases of purely fourth and sixth order crystal field.
Three‐Phonon Interactions in Bismuth Germanium Oxide
Authors: Krzesinska M. 
Published: July 2007

AbstractThe anharmonic interactions of hypersonic waves with thermal phonons in bismuth germanium oxide (BGO) will be discussed. The effect of elastic anisotropy, temperature, and chromium impurity on the allowed three‐phonon processes is treated in detail. Allowed processes where hypersonic waves interact with thermal phonons on the same acoustic branch of the phonon spectrum as themselves are predicted to exist. Measurements of velocity at low temperatures in BGO are used for calculations.
Magnetic Properties of Rb2MnxCr1−xCl4 Mixed Crystals
Authors: Grieb Th. , Wacker K. , Naumann E. , Treutmann W. , Heger G. , Geick R. 
Published: July 2007

AbstractThe mixed crystal system Rb2Cr1−xMnxCl4 is studied by magnetization measurements at liquid helium temperatures and for orientations of the external magnetic field H parallel and perpendicular to the crystallographic c‐axis. The concentration x of the samples is in the range 0≦x≦≦0.3 on the Cr‐rich side and 0.9≦x≦1.0 on the Mn‐rich side. The experimental results are analysed and discussed by means of an average model calculation for the magnetic x‐H phase diagram at low temperatures (T = 4.2 K). The experimental data confirm the predictions of the model with respect to the influence of the single‐ion anisotropy of the Cr2+ ions on the spin‐flop field in the region of high Mn concentration and of the antiferromagnetic exchange coupling between Mn2+ and Cr2+ ions on the magnetization for high Cr concentration. In addition, the experimental results are in agreement with those from magnetic resonance measurements.
Induced Magnetic Form Factors for 3d Transition Metals and 3d‐3d Alloys III. Diamagnetie Form Factors
Authors: Pabst J. , Röll H. 
Published: July 2007

AbstractDiamagnetie scattering is discussed for transition metals and transition metal alloys. The same concept as applied for the description of induced spin scattering is used. It is shown that diamagnetic susceptibility and form, factors obtained from band structure calculations greatly differ from those calculated from Hartree‐Fock‐Slater densities for the free atom. Differences induced by a charge transfer between the alloy atoms arise also between the quantities of pure metals and those of alloys; however, the differences between pure metals and alloys are less than those with induced spin scattering. Calculated diamagnetic form factors are indicated by their Fourier coefficients.
Non‐Monotonous Behaviour of the Nernst‐Ettingshausen Effect in Conductive Films in a Strong Magnetic Field
Authors: Askerov B. M. , Kuliev B. I. , Figarova S. R. , Eminov R. F. 
Published: July 2007

AbstractThe Nernst‐Ettingshausen effect is studied in thin conductive films in a strong transverse magnetic field. The expression is obtained for the NE coefficient Q for arbitrary charge carrier statistics and film thickness, assuming dimensional quantization and piezo‐acoustic phonon scattering. It is shown that in the case of films with degenerate electron gas the NE coefficient oscillates with the variation of the thickness of the film d. The oscillation period is determined as a function of the concentration of the conduction electrons. Taking account of the surface scattering a detailed analysis of the NE coefficient dependence on the film thickness is given including films of thickness comparable to the mean free path of the charge carriers. Computer calculations show that under these conditions the function Q(d) is non‐monotonous as well.
Quantum Oscillations of Magnetoresistance and Thermomagnetic Power and the Fermi Surface of As‐Sb Alloys
Authors: Muntyanu F. M. 
Published: July 2007

AbstractQuantum oscillations of magnetoresistance and thermomagnetic power of AsxSb1−x (0 ≦ x ≦ 1) alloys in stationary magnetic fields up to 15 T at low temperatures (1.9 ≦ T ≦ 17 K) are investigated. In the alloys, with x ≦ 0.3, the quantum oscillations of thermomagnetic power with a “giant” amplitude are observed. The peculiarities of the energy spectrum reconstruction are determined and the composition range in which a break of the hole necks occurs is defined. It is established that AsSb alloys are semimetals in which overlapping of the hole and electron terms in the first approximation increases linearly with increasing x.
Time‐Resolved Investigation of the Ne Luminescence
Authors: Seitfudem G. 
Published: July 2007

AbstractSolid Ne condensed at a temperature of 7 K is excited with a pulsed electron beam. The resulting emission spectra are recorded during the excitation pulse and in the time range from 0 to 2.3 ms after excitation. Relative contributions from the different vibrational levels are fitted to the Ne emissions, measured at various times after the excitation. A nearly constant contribution from the 0th vibrational level is found which can be explained by complete relaxation of the 0u− excimer state. The degree of relaxation and the decay time of the luminescence contributions from the higher vibrational levels change within the 2.3 ms. It is proposed that the lu state of Ne emits from lattice sites at one vacancy, two vacancies, and from regular lattice sites.
On the Transformation of Collective Modes in a Viscoelastic Medium
Authors: Olemskoi A. I. , Panin V. E. , Petrunin V. A. 
Published: July 2007

AbstractThe transition between „strongly”︁ and „weakly”︁ excited states of the condensed matter is considered. The collective mode, which is connected with the shear components of stress and strain, changes the dispersion law from imaginary to real. This transformation takes place for a boundary wave vector, which is determined by the viscosity of the medium. The reactive and relaxation components of strain perform roles of „breaking and restoring symmetry”︁ variables, consequently. On the base of phenomenological and microscopic approaches a synergetic model of kinetic transformation between strongly and weakly excited states is considered.
Fractal and Percolative Features of Aggregation Processes in NaCl:Eu2+ System Detected by Time‐Resolved Spectroscopy
Authors: Cassi D. , Fava R. , Manfredi M. , Opyrchal H. , Suszyńska M. 
Published: July 2007

AbstractTime resolved spectroscopy of Eu2+ aggregates in the NaCl system — at different stages of the aggregation process — shows a non‐exponential behaviour of time decay signals that is interpreted in terms of excitation migration and up‐conversion processes in a fractal geometry. Following this model, the spectral dimension of such aggregates is obtained from the time decay profiles. The analysis of experimental results suggests a model (fluctuation‐percolation triggered aggregation, FPTA) for the aggregation process.
Dc electrical conductivity of ultrathin AgSiO superlattices
Authors: Abu El‐Haija A. J. , Madjid A. H. 
Published: July 2007

AbstractUltrathin multilayer structures of successive silver and silicon monoxide layer pairs are prepared using evaporation techniques. Small angle X‐ray diffraction and multiple reflection interferometric techniques are used to establish the identity periods of samples. A review of the electrical properties is presented. Both applied voltage and thermally induced resistance switching are observed. These phenomena are described from an empirical vantage.
Image force and stopping power of a fast moving ion near a metal surface
Authors: Bao Tran Thoai Duy 
Published: July 2007

AbstractThe image force on an external ion moving parallel to a metal surface is studied within the hydrodynamic model. Expressions for its longitudinal and transversal components are derived. Retardation effects, spatial dispersion, and diffuseness of the electron density at the surface are included. Results of the longitudinal component of the image force and of the corresponding stopping power are reported numerically for different electron densities. They show a pronounced dependence on the velocity of the moving ion.
Stochastic quantization approach to disordered fermions
Authors: Kolley E. , Kolley W. 
Published: July 2007

AbstractThe method of the stochastic quantization is applied to an electron system described by the random Hubbard model. Two different stochastic calculi are performed corresponding to Euclidean and non‐Euclidean versions of the quantum field theory in terms of Grassmann variables. In averaging over the quenched disorder a nontrivial normalization denominator can be avoided. An averaged, effective two‐time action is given as basis for treating localization.
Investigation of Quantum States of Fast Electrons under Planar Channeling in Silicon Crystals
Authors: Gridnev V. I. , Kaplin V. V. , Khlabutin V. G. , Rozum E. I. , Vorobiev S. A. 
Published: July 2007

AbstractThe angular distributions of (1.87 to 5.7) MeV electrons channeled in 2 μm Si crystals along (100), (110), and (111) atomic planes are measured. The half‐width of measured angular distributions is defined by a critical Lindhard angle. A relation is obtained connecting those energies of electrons at which their angular distributions are similar for various atomic planes. The effect of a “critical energy” under planar channeling of electrons is found and investigated.
Determination of the Distribution Widths of the Spin Hamiltonian Parameters of V4+ Ions from Oxide Glasses
Authors: Nicula Al. , Culea E. 
Published: July 2007

AbstractA method is proposed to determine the distribution widths of the spin Hamiltonian parameters g| and A| of V4+ ions from oxide glasses. The basic assumption is that the structural disorder characteristic for such materials determine a distribution of the molecular bonding parameters and of the orbital excitation energies, which lead finally to a distribution of the spin‐Hamiltonian parameters. Estimates of the distribution widths of g| and A| are made for two glasses, As2O3–V2O5 and B2O3–V2O5 with 5% molar V2P5, using EPR and optical data.
The Environment of Muonium in Solids. An Empirical Approach
Authors: Souiri M. , Goltzene A. , Schwab C. 
Published: July 2007

AbstractHaving justified an empirical approach by the study of the correlations between the hyperfine constant value of the Mn2+ ion and bonding parameters in different host matrices, it is applied to muonium. Thus its preference for a cation environment in tetrahedral structures is revealed, which could be partially screened in other ones.
The Nonlinear Theory of the Snoek Relaxation Effect under the Strong and Homogeneous Bias Stress System
Authors: O˘gurtani T. Ö. 
Published: July 2007

AbstractThe nonlinear theory of energy dissipation associated with the mobile paraelastic octahedral interstitial atoms in inhomogeneous interaction fields is applied to the specific problem of the ordinary Snoek relaxation under the influence of the uniform static stress system (an external bias field). In the case of a uniaxial static bias stress system, an extremely accurate and simple analytical expression is deduced for the logarithmic decrement which indicates strong dependence on the magnitude, sign, and direction of the externally applied bias stress with respect to the direction of the excitation field in body centered cubic lattices. It is also demonstrated that by the internal friction measurements in single crystals, utilizing the large on‐line (parallel) and/or off‐line (orthogonal) static bias fields, the direct information about the symmetry, shape and strength of the elastic dipole tensor associated with the equilibrium‐point configurations (intrinsic) can be obtained.
Muon Spin Rotation Spectroscopy in Metallic Spin Glass Systems
Authors: Pinkvos H. , Schwink Ch. 
Published: July 2007

AbstractAn introduction is given into the application of muon spin rotation spectroscopy to spin glass problems. The principles of the μSR method are discussed in connection with basic properties of spin glasses. Important information provided by μSR on the dynamical behaviour of the impurity spins, the spatial structure of the freezing process, and the form of the autocorrelation function for the local fields are reviewed in chosen examples.
Light Absorption and Hyper‐Raman Scattering by Many‐Electron Complexes in Quantum Well Structures
Authors: Bobrysheva A. I. , Russu S. S. , Zaloi V. A. 
Published: July 2007

AbstractIt is shown that in GaAs/AlxGa1‐xAs multiple‐quantum well structures bihole formation is possible. Also the main features of biexciton hyper‐Raman scattering are established.
Infrared Absorption and Anharmonicity of Crystalline Nitrogen
Authors: Fugol I. Ya. , Ratner A. M. , Khashchina L. V. , Pritula I. M. 
Published: July 2007

AbstractFIR spectra of α‐nitrogen are discussed taking into account optical and mechanical anharmonicities. It is shown that the lattice absorption spectrum is mainly formed due to the optical anharmonicity. The two‐phonon decay rates of IR‐active modes are estimated from measured line halfwidths.
Quantum‐Statistical Approach to Elastic Constants in Metals Influenced by Magnetization
Authors: Cinal M. , Olszewski S. 
Published: July 2007

AbstractMagnetic contributions to metal compressibility, lattice Grüneisen parameter, and their pressure dependence are calculated with the aid of the Thomas‐Fermi‐Dirac ab initio theory. The magnetic volume obtained on the basis of the same theory makes possible to estimate the volume dependence of the Stoner parameter and the magnetic Grüneisen parameter.
Magnetic Dipole Absorption of Colloidal Ag in Single Crystals of KCl
Authors: Pützler M. , Fischer F. 
Published: July 2007

AbstractExperimental evidence for magnetic dipole absorption of Ag particles, produced by solid state reaction in a KCl single crystal, is given for the first time. Absorption in the FIR better follows a ω4 than ω2 law. A maximum absorption at 65 cm−1 is up to five times as high as the absorption plateau in the MIR. Therefore the low temperature scattering rate of electrons is clearly lower than for electric dipole absorption. A quantitative comparison shows absorption still 10 to 50 times higher than predicted by current quantum mechanical theories.
Optical and Electrical Bistability Induced by Exciton Ionization Processes
Authors: Ashkinadze B. M. , Belkov V. V. , Subashiev A. V. 
Published: July 2007

AbstractNonlinear optical effects in the luminescence and the microwave absorption which are induced by heating of electrons in a microwave electric field are revealed in silicon: (1) Hysteresis in the exciton condensation process at T = 2 K which results in the bistability of the recombination radiation, with a hysteresis lifetime of 3 × 10−2s. (2) Self‐oscillations in the electron density during impact ionization of excitons, the frequency of the self‐oscillations varies over the range 0.5 to 5 MHz while changing the light excitation or microwave power. (3) Thermal exciton breakdown which is accompanied by jumps and hysteresis of the sample temperature as the excitation is varied.
Nonlinear Absorption in Quantum‐Size Heterostructures
Authors: Kononenko V. K. 
Published: July 2007

AbstractA theory is developed of absorption saturation on filling the subbands appearing in quantum wells. It is shown that the bleaching spectrum of quantum‐size heterostructures has a resonant, sawtooth shape. The transformation of nonlinear absorption spectra is analyzed depending on the layer thickness, temperature, excitation power, and the character of optical transitions between the electronic states in the quantum wells.
Fast and Strong Nonlinearity of Thin‐Film Semiconductor Interferometers Due to Intrinsic Photo‐ and Electrooptical Effects of the Semiconductor Interlayer
Authors: Karpushko F. V. 
Published: July 2007

AbstractThe electron nature mechanism of optical nonlinearity in thin‐film semiconductor interference systems is considered. It is shown that due to the boundary barrier photo‐ and electrooptic effects in thin‐film system there is the fast and low‐energy photoinduced charges of refractive index. The estimates of switching energy and operation rates of the OB devices based on this nonlinear mechanism are close to the fundamental limits.
Optical Nonlinearity Due to the Excitonic System in CuCl
Authors: Nagasawa N. 
Published: July 2007

AbstractThe optical nonlinearity associated with the giant two‐photon absorption, GTA, of excitonic molecules in CuCl is discussed. The metamorphoses of the four‐wave mixing spectra due to the generation of the exciton grating are demonstrated by the observation of their polarization characteristics. The propagation characteristics of the excitation around the GTA resonance are observed by micro‐Raman spectroscopy. The two‐photon Raman scattering light is used as a probe to monitor the spatial character of the excitation. The propagation characteristics show a drastic change in the very narrow spectral range around the GTA resonance energy.
Complex Centres in Additively Coloured RbCl: Li+
Authors: de Matteis F. , Scacco A. , Somma F. , Baldacchini G. , Giovenale E. , Grassano U. M. 
Published: July 2007

AbstractComplex colour centres in RbCl and RbCl:Li+ are extensively studied. (F2)A centres, never observed so far in this system, are formed and their optical absorption and emission determined. The kinetics of the equilibria among aggregate and associate defects are investigated in order to obtain the highest concentration of (F2)A centres.