bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nondipole radiation of electrons at planar channeling
Authors: Baier V. N. , Katkov V. M. , Strakhovenko V. M. 
Published: July 2007

AbstractThe nondipole radiation of electrons is considered for any shape of the interplane potential. A concrete analysis and comparison with the radiation of positrons are carried out for a potential of the „inverse parabola”︁ type. It is shown that for the description of the radiation of particles with energy e ε ⪅ 10 GeV in the region of the maximum of the spectral distribution it is possible to take into account the few first harmonics of the motion only. This substantially simplifies the calculation, especially for the potentials with complex shape. The diagrams which illustrate the radiation spectrum as a function of the angular width and of the direction of beam incidence in a thin crystal, are depicted. A detailed comparison of the results with available experimental data is made.
Stopping power of atoms near metal surfaces at grazing incidence condition
Authors: Kato M. , Ohtsuki Y. H. 
Published: July 2007

AbstractThe energy loss of slow atoms is studied from the viewpoint of the indirect excitation of low‐energy electron–hole pairs, i.e., the excitations of electron–hole pairs through the electron exchange process from the metal to the projectile's atomic states, and vice versa. For the slow atom, v ≪ vF (v and vF are the velocity of the projectile and the Fermi velocity, respectively), electrons have enough velocity for response, thus the atomic states are not well defined due to the screening effect and the electron exchange processes. By constructing the model Hamiltonian which describes such effects from first principles the stopping power at grazing incidence condition, especially for the Cs surface, is calculated.
Static polarizability and dipolar surface plasmon of small metal particles. II. Including the lattice structure
Authors: Bao Tran Thoai Duy 
Published: July 2007

AbstractThe frequency of the dipolar surface of small particles is calculated using the sum rule techniques due to Lushnikov et al. The effect of surface diffuseness of electron density is included. The screening of the electrons is described within the Thomas‐Fermi approximation. The lattice structure and the lattice relaxation through the introduction of pseudopotentials are taken into account. The ground state charge density is obtained from a variational estimate of the total energy of the clusters based on the local density functional formalism. The surface plasmon frequency is red‐shifted from its classical value.
Luminescence et transition non radiative 3T1u → 3A1u dans le luminophore BaS:Bi3+
Authors: Asano Par S. , Nakao Y. , Yamashita N. , Matsuyama I. 
Published: July 2007

AbstractEmission and excitation spectra of BaS:Bi3+ phosphors are measured at 300, 80, and 6 K. I n the excitation spectra the A and C excitation bands are observed. In the emission spectra only one band is observed which is assigned to the transition 3A1u → 1A1g on the basis of the measurement of the time‐resolved emission spectra and the decay constant of the phosphorescence. The diffused reflection spectra and the magnetic effect on the phonon structure of the emission band are also measured at 80 and 4.2 K, respectively. The former is compared with the excitation spectra. The reason why the emission band 3T1u → 1A1g cannot be observed at low temperatures is explained by the fact that the probability of the tunnel effect 3T1u → 3A1u is larger than that of the luminescent transition 3T1u → 1A1g.
The realization of the generalized transfer equation in a medium with fractal geometry
Authors: Nigmatullin R. R. 
Published: July 2007

AbstractIt is shown that in a medium representing an example of “Koch's tree”‐type fractional structure the diffusion process is described by a generalized transfer equation in partial derivations. Such a structure can serve as a model of a porous medium where the diffusion process takes place. The geometry of an inhomogeneous medium can serve as the dicisive factor in the explanation of the “universal response” phenomenon. A range of frequencies is found where such “superslow” diffusion process can be observed.
Dynamical model for the vibrations of the hydrogen halide crystals
Authors: Higgs J. F. , Zeng W. Y. , Anderson A. 
Published: July 2007

AbstractA force constant model is developed and applied to the vibrations of the hydrogen halide crystals, HBr, HCl, and HF, in their ordered phases. Fundamental frequencies are calculated and compared to those observed by infrared and Raman spectroscopy. It is found that two bending forces, representing electrostatic interactions, are necessary, one of which partially cancels elastic forces for certain modes. Variations of force constants with interatomic distances and comparisons of their values for the three crystals are briefly discussed.
Thermodynamic analysis of the Anderson‐Grüneisen parameters
Authors: Dhoble Aruna , Verma M. P. 
Published: July 2007

AbstractThermodynamic equations connecting the Grüneisen and the Anderson‐Grüneisen parameters r, q, δT, and δS with experimentally determinable quantities are used to determine the values of these parameters at room temperature 295 K. The results so obtained are discussed in the light of the currently accepted theoretical and experimental values of these quantities.
On the defecton statistics in quantum crystals
Authors: Pushkarov D. I. 
Published: July 2007

AbstractThe defecton statistics in quantum crystals is treated, and a new method for determining commutation relations is proposed. Defectons related to defects of a different kind (vacancies, impurities, interstitials) are considered in crystals both of the Bose‐type (4He) and Fermi‐type (3He). The kinematic interaction is discussed.
Quantum theory of free‐carrier absorption in quasi‐two‐dimensional semiconducting structures
Authors: Giner C. Tballeeo , Antón M. 
Published: July 2007

AbstractThe quantum theory of free carrier absorption in quasi‐two‐dimensional structures like thin films, layered heterojunctions, and inversion layers is generalized to the cases when the carriers are scattered by polar optical phonons, piezoelectric phonons, and nonpolar optical phonons. The obtained results are compared with those of the quantum theory of free‐carrier absorption in a bulk semiconductor and it is found that the absorption coefficient increases when the width of the layer or thin film decreases in all the cases.
Effect of thin space‐charge layers on exciton reflectance
Authors: Kiselev V. A. , Novikov B. V. , Cherednichenko A. E. , Ubushiev E. A. 
Published: July 2007

AbstractResonance reflectance in semiconductors in the frequency region of exciton transitions depends strongly on characteristics of the near‐surface space‐charge layers. It is shown by numerical computation that the majority of the exciton reflection lineshapes observed on CdS earlier may be explained by the presence of a thin (10 to 100 nm) space‐charge layer with a relatively high (104 to 105 V/cm) surface electric field. Various treatments of surfaces alter charges on and below them thus modifying the electric field distribution. The latter causes changes in the exciton reflectance. Transformations of the exciton lineshapes under the action of illumination and electron bombardment are discussed in detail for the case of CdS. The lineshapes show drastic variations with expositions of both influences. In a single experiment one may observe all of the anomalies typical for the thin space‐charge layers.
Charge transfer satellites in X‐ray photoelectron spectra of La2CuO4
Authors: Viswanathan B. , Madhavan S. , Swamy C. S. 
Published: July 2007

AbstractThe displacements and intensity of charge transfer (oxygen to lanthanum) satellites of lanthanum 3d, 4d, and 4p levels are found to be different for La2O3 and La2CuO4, while they are the same for other ABO3 perovskites and La2O3. This difference is caused by the increased possibility of „mixed configuration”︁ for lanthanum ions in La2CuO4 due to d2z2 level of half of copper ions intersecting the Fermi level. The effect of the changes in the geometry of the environment of the cations is also reflected in the asymmetric nature of the O(ls) peak in La2CuO4 which is known to contain different types of MO bonds.
Calculated low energy electron total current spectra for the A1(111) surface
Authors: Smith A. E. , Lynch D. F. 
Published: July 2007

AbstractResults of low energy electron diffraction calculations using the scattering matrix method are presented for the incident energy range 0.5 to 40 eV for the (111) A1 face and a comparison is made with reported measured total current spectroscopy results. It is concluded that the structure of the experimental spectra is determined by elastic diffraction effects and that the TCS technique provides information on the mean inner and absorption potentials in the very low incident energy region.
Hot nuclear fluorescence in the LiI crystal
Authors: Haas M. A. 
Published: July 2007

AbstractResonance scattering of γ‐radiation by Li nuclei is considered in a LiI crystal. In this crystal hot nuclear fluorescence is the main scattering process a t energies of ≈ 477 keV, whereas at a fixed scattering angle the spectral distribution of the scattered quanta depends essentially on the direction of the incident beam. Calculations are made for the orientational effects expected in the case of backward‐scattered quanta registered by a resonant detector. It is shown that the signal of such a detector as a function of mutual orientation of the crystal and the incident beam has sharp (of ≈6° width) maxima of a reasonable intensity in the [100] and [111] directions. The connection between the obtained angular characteristics, the details of the relaxation process in the crystal lattice, and the specific form of the interatomic potential are discussed.
Variances in molecular magnetic susceptibilities of monoclinic crystals
Authors: Aly A. A. , Ibrahim I. H. , Abdeen A. M. , Abdel‐Gawad M. M. 
Published: July 2007

AbstractExpressions are obtained for the variances of the molecular magnetic susceptibilities and anisotropies in the case of monoclinic crystals. The molecular magnetic susceptibilities, anisotropies, and their variances for some organic compounds (monoclinic crystals) are calculated refered to the molecular orientations and their inclinations on the crystallographic axes. These molecular magnetic susceptibilities are compared with those obtained using the molecular inclination determined by X‐ray analysis.
Self‐consistent theory of the electronic structure of inversion layers. II. Quantum effects and the electronic properties of MIS structures
Authors: Übensee H. , Paasch G. , Zöllner J.‐P. 
Published: July 2007

AbstractIn part I a new method was described for the self‐consistent calculation of electron and hole densities, band bending, and subband energies in inversion layers of MIS structures. This method is of the numerical simplicity of the classical calculation but the results obtained with this method deviate only slightly from those ones obtained from explicit solutions of the Schrödinger equation. Here the new method is used to investigate the influence of quantum effects in the inversion layer on electronic properties of MIS structures. Since the latter usually are calculated classically the method is compared even with the classical one. The classical method yields in special cases good results for the calculation of MIS structures. The deeper reasons for them are shown and where the classical method is no longer applicable.
Determination of the orientation distribution function from pole figures in arbitrarily defined cells
Authors: Pawlik K. 
Published: July 2007

AbstractPractical problems of the reproduction of the orientation distribution function (ODF) from pole figures (PFs) using discrete methods (with special attention paid to Imhof's method,) are analysed. A new variant of the iteration method for the determination of the ODF in arbitrarily defined size of cells in the orientation space, is suggested. The special case, in which the centro‐symmetrical equivalency of the PFs is induced by the elements of proper rotations in crystal symmetry, is considered.
Quantum‐mechanical calculations for hydrogen in niobium and tantalum. II. Diffusion coefficients
Authors: Klamt A. , Teichler H. 
Published: July 2007

AbstractResults of quantitative theoretical investigations are presented concerning the diffusion coefficients of H and D in Nban Ta. They are based on the quantum theory of the diffusion of light interstitials and take into account the lattice‐configuration dependence of the hydrogen tunneling integrals and the effects of adiabatic saturation of the transition rate. Thecalculations make use of a semiempirical hydrogen‐host‐lattice interaction potential which is adapted to experimental data from outside the diffusion phenomena. The resulting theoretical values for the diffusion coefficients agree well with the experimental observations.
Defect reactions in electron‐irradiated α‐Fe111 studied by means of PAC measurements
Authors: Golczewski J. , Maiee K. , Frank W. 
Published: July 2007

AbstractDefect reactions in electron‐irradiated α‐Fe111In were studied by means of the perturbed‐angular‐correlation (PAC) technique. There is no indication of a mutual annihilation of freely migrating Stage‐IE defects and Stage‐III defects trapped at 111 In probes. This is as expected from the two‐interstitial model and provides strong evidence against the one‐interstitial model for α‐Fe.
The curie temperature of an anisotropic heisenberg ferromagnet with mixed spins
Authors: Iwashita T. , Uryû N. 
Published: July 2007

AbstractFor the anisotropic Heisenberg ferromagnet with mixed spins of S = 1/2 and S = 3/2 and of S = 1/2 and S = 2, the Curie temperature TC is calculated with the use of pair model approximation. Assuming an anisotropic bilinear exchange interaction J between nearest neighbors of different spins and a uniaxial single‐ionic anisotropy D‐term for the spins of S = 3/2 and S = 2, the behavior of Tc as a function of these parameters J and D is investigated for some types of the spin system with various values of the anisotropy parameter α of the exchange interaction.
On participation of medium oscillations in wannier exciton motion
Authors: Myasnikov E. N. , Druzhinin A. E. , Popov A. P. 
Published: July 2007

AbstractThe effect of quantum polarizable‐medium motion on relative and translational motion of the Wannier nonlocalized exciton (NLE) is investigated. It is shown that the polarization admixed to the internal motion of electron‐hole pair does (since each of the two particles is involved in both types of motion) participate in the external exciton motion which may bear the quantum character. It is pointed out that in the vicinity of k = m1/m2≪ 1, where m1(2) is the effective electron (hole) mass, the polarizing NLE for αh 3⪅ (αh being the coupling constant between the hole and LO‐phonons) is energetically more favourable than the self‐trapped exciton (STE).
Electron Gas heating under spin‐flip Raman scattering conditions in n‐InSb
Authors: Studenikin S. A. , Skok E. M. 
Published: July 2007

AbstractSpin‐flip resonance induced magnetoresistance is studied of n‐type InSb in quantising magnetic fields. The sample is held at 2 K in magnetic fields up to 1.3 T. Double‐differentiation techniques are used to detect weak signals. It is shown that magnetoresistance changes because of electron gas heating, additionally the heating of phonons must be taken into account as well. Simultaneous measurements of the spin‐flip Raman gain and photoconductive response make it possible to determine the energy relaxation time τε ≈ 0.9 × 10−6 s which remains approximately constant in the magnetic fields.
Lattice dynamics of F.C.C. metals
Authors: Thakur V. K. , Singh T. N. 
Published: July 2007

AbstractA theoretical model of the lattice dynamics of face centered cubic crystals is developed. The potential energy of a face centered cubic metallic crystal is considered due to (i) ion‐ion and (ii) ion‐electron interactions. The contribution to ion‐ion interaction is evaluated applying the valence force field. The contribution to the potential energy from ion‐electron interaction is considered through the screened Coulomb potential. The theoretical model developed is employed to compute the phonon dispersion curves for copper, silver, and gold. Computed phonon frequencies at 48 non‐equivalent points are usedto interpret specific heat and Debye characteristic temperature. The agreement between the calculated and experimental results is fairly good.
Specific heat of Nb‐Doped RuO2 single crystals
Authors: Mertig M. , Pompe G. , Hegenbarth E. 
Published: July 2007

AbstractThe low temperature specific heat of RuO2 single crystals is investigated up to a Nb content of x = 4.5 at% by means of the microcalorimetric ac method. The electronic part of the specific heat gives information about the alteration of the density of states at the Fermi energy D(εF) in dependence on the Nb content. The density of states at the Fermi energy of the undoped sample is D(εF) = 30.0 (cell spin Ryd)−1. The observed increase of D(εF) up to a Nb content of 4.5 at% is smaller than 6%. It is checked, whether a rigid band model explains the observed results. Characteristic changes in the phonon contribution of the specific heat will be discussed, too.
Semiempirical calculation of oxygen vacancy in vitreous silica
Authors: Sokolov V. O. , Sulimov V. B. 
Published: July 2007

AbstractElectronic properties of an oxygen vacancy in solid silicon dioxide are investigated by a semiempirical LCAO/MO method (MINDO/3) in a molecular cluster approximation. The importance is demonstrated of taking into account the relaxation of the nearest atomic environment of the oxygen vacancy. One‐electron energies and wave functions, conformation parameters, and ESR electronic g‐factors are calculated for a number of charge states of the oxygen vacancy.
Absorption and uniaxial stress experiments in the B, C, and d' Bands of Pb2+ centres in KBr, RbBr, KI, and RbI
Authors: Schmitt K. 
Published: July 2007

AbstractThe optical absorption and the stress‐induced dichroism of the Pb2+ centre in KBr, RbBr, KI, and RbI are studied in the spectral range of the B, C, and d' bands. The splitting of the degenerate electronic states and the stress‐induced configuration interaction are analysed. In addition the assignments of the absorption bands in KI and Rbl, proposed by Tsuboi are confirmed.
Tunnelling in k‐space application to degenerate valence bands
Authors: Dargys A. , Rudolph A. F. 
Published: July 2007

AbstractHole tunnelling between light and heavy mass bands in a homogeneous semiconductor due to strong electric fields is analyzed in the framework of the spherical and degenerate at k = 0 bands with spin‐orbit interaction neglected. It is found that in k‐space intense transitions between bands occur in a ring‐shaped volume, whose symmetry axis is parallel to the electric field. At high fields, of the order of 30 kV/cm, the average diameter of the ring, where hole tunnelling is most intense, becomes smaller than the diameter of the optical phonon sphere. As a result, before the collision with an optical phonon, the ballistically moving hole experiences velocity modulation. Some possible experimental situations which would allow to discriminate the hole tunnelling in the degenerate bands from the collision dominated processes, are discussed briefly.
Theoretical study of the gradual chemical transition at the Si‐SiO2 interface
Authors: Hübner K. , Klinkenberg E.‐D. , Stern A. 
Published: July 2007

AbstractBall‐and‐sticks cluster models for the Si(111)–SiO2 and the Si(100)–SiO2 interregion are built. Oxygen constituents are represented by model elements realized with the help of cardan links, which permit a variable oxygen bridging angle already during the building procedure. The atomic positions are refined by means of a modified Keating potential. The numerical analysis indicates that the width of the chemical transition between Si and SiO3 has a value of approximately 1 nm and also depends on the substrate orientation. The resulting oxygen profile reveals an asymmetric form. The calculated distribution of the elastic energy has a maximum at a distance of 0.6 nm from the Si surface and is mainly caused by rings with less than six members. The resulting structure of the transition region supports the random‐bonding model for the statistical distribution of its tetrahedral Si‐SiyO4–y constituents (y = 0,…, 4). Theoretical scattering data permit to compare the model structures with corresponding results of X‐ray scattering experiments.
Raman and infrared studies of tetramethylammonium tetrachlorozincate
Authors: Tang S. H. , Looi E. C. , Radhakrishna S. 
Published: July 2007

AbstractRaman and IR studies for the ferroelectric crystal (N(CH3)4)2ZnCl4, is reported. From these studies the Raman lines observed are assigned and the local site symmetry of ZnCl4, is determined.
EPR spectra of single crystal bis(glycine) calcium (II) dichloride tetrahydrate with copper(II) ion
Authors: Subramanian P. , Hariharan N. 
Published: July 2007

AbstractSingle crystals of bis(glycine) calcium(II) dichloride tetrahydrate (GCaCl) are grown with Cu2+ dopant. The observed spectra in all three planes show the fact that the paramagnetic ions enter substitutional position. The Cu2+ ion entering the site of calcium ion has coordination of eight oxygen atoms in a distorted dodecahedral arrangement. The ion experiences an orthorhombic crystalline field. Molecular orbital coefficients are determined for this complex and a comparison is made with dodecahedral metal complexes. The unpaired electron resides in the dxy orbital. The metal‐ ligand σ‐bond is stronger and hence shows the strong covalent nature of metal‐oxygen.Bis(Glyzin)‐Kalzium(II) dichloridtetrahydrat (GCaCl)‐Einkristalle werden mit Cu2+‐Dotierung gezüchtet. Die beobachteten Spektren in allen drei Ebenen zeigen die Tatsache, daß die paramagnetischen Ionen Substitutionsplätze einnehmen. Das Cu2+‐Ion, das den Kalziumplatz besetzt, hat eine Koordination von acht Sauerstoffatomen in einer gestörten Dodekaederanordnung. Das Ion ist einem rhombischen Kristallfeld ausgesetzt. Molekülbahnkoeffizienten für diesen Komplex werden berechnet und ein Vergleich mit Dodekaedermetallkomplexen durchgeführt. Das ungepaarte Elektron besetzt das dxy‐Orbital. Die Metall‐ ligand σ‐Bindung ist stärker und zeigt so die starke kovalente Natur der Metall‐Sauerstoff‐Bindung.
X‐Ray K‐Absorption Study of Copper in Malachite Mineral
Authors: Hemachandran K. , Chetal A. R. 
Published: July 2007

AbstractThe shape and chemical shift of the Cu K‐absorption edge in malachite mineral are studied by using a Cauchois type bent crystal X‐ray spectrograph. The oxidation state of copper is established as two in the mineral. The peaks A, B, and C observed in the absorption edge are explained on the basis of molecular orbital theory (MOT).
Optical Properties of Multi‐Layer Structures. I. Polaritons
Authors: Fomin V. M. , Pokatilov E. P. 
Published: July 2007

AbstractA theory of polaritons is developed for multi‐layer structures with an arbitrary number of layers. On the basis of the solutions of Maxwell equations with the boundary conditions taken into account the dispersion relations of s‐ and p‐polarized polaritons are obtained for multi‐layer structures and, in particular, for periodic structures. The classification of polaritons is made by the character of a spatial distribution of the electric and magnetic fields as well as by the change of the fields in a period of the structure (spatially decreasing and extended). A new type of polaritons is found in multi‐layer structures, viz. spatially decreasing polaritons. The decrease coefficients and decrements of the localized polaritons are calculated for superlattices GaAs/Ga1−xAlxAs.