bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phonon Shifts in GaP Due to Temperature and Pressure Rise Induced by a Laser Beam
Authors: Irmer G. , Monecke J. , Bairamov B. Kh. , Toporov V. V. 
Published: July 2007

AbstractRaman spectroscopic measurements of the TO‐ and LO‐phonon shifts of GaP in the temperature field induced by a laser beam are performed and compared with measurements in a uniformly heated sample. The temperature and the stress distribution in the sample volume irradiated by the laser beam are calculated and their influence onto the phonon frequencies is discussed with the result that thermoelastic effects besides the temperature rise due to the laser beam cannot be neglected, in general.
Evaluation of Electronic Dielectric Constant and Fractional Ionic Character of Mixed Alkali Halide Crystals
Authors: Shanker J. , Sharma S. C. 
Published: July 2007

AbstractThe electronic dielectric constant and fractional ionic character of the chemical bond are calculated for the mixed crystals NaClNaBr, KClKBr, KBrKI, CsClCsBr, CsClRbCl, and CsClKCl for the entire range of composition. The first four solid solutions are with common cations whereas the last two are formed of substances with common anions. For the electronic dielectric constant a comparison is given of the values calculated from the Clausius‐Mossotti relation and the Pantelides formulation. For evaluating the fractional ionic character application is made of Phillips' and Pauling's theories. The calculated values are found to depend sensitiviely on the composition parameter of mixed crystals.
Rotational Excitations of Methyl Groups in 2,3‐Dimethylnaphthalene
Authors: Kalus J. , Schleifer J. , Hbmpelmann R. , Richtee W. 
Published: July 2007

Abstract2,3‐dimethylnaphthalene (2,3‐DMN) crystallizes similar to naphthalene but with dipolar structural disorder of the acentric molecules. Quasielastic neutron scattering of the methyl groups between 12 and 270 K is studied for scattering vectors up to 17.7 nm−1. The experimental results are fitted to a rotational jump model. From a fixed window experiment a broad band of activation energies around 1350 K is deduced.
Influence of a Surface on Lifetime Spectra of Positrons
Authors: Belbnkii V. M. , Begzanov R. B. , Bolotov V. N. , Kuznichenko A. V. 
Published: July 2007

AbstractPositrons implanted into the solid are thermalized and can diffuse to the surface. The probability of trapping positrons by the solid surface and by the surface of defects is calculated. Obvious analytic expressions for W(t), F, and Iv(t) in terms of special functions are obtained, as well as an obvious criterion for the case of many defects. The obtained results show that the dynamics of a thermalized positron interaction with a surface affects the positron lifetime spectra.
Density Functional Approach to the Surface Tension of Liquid Metals
Authors: Lai S. K. 
Published: July 2007

AbstractThe local density functional formalism of Evans and Hasegawa, previously developed for the study of surface properties, is re‐examined by including nonlocality of pseudopotential in the theory. It is found that (i) when the pseudopotential is nonlocal, the fourth order density gradient correction of Ma and Sahni must be included in order that the density profiles obtained are physically meaningful and (ii) the first order perturbation is inadequate for understanding the surface tension of simple liquid metalsin accordance with conclusions made by other investigators.
The Spectral Behaviour of a General Damped Anharmonic Oscillator
Authors: Bose S. K. , Dubey U. B. , Tewari V. N. 
Published: July 2007

AbstractThe spectral behaviour is investigated of the radiation emitted by a charged particle executing the motion of a general anharmonic oscillator under the influence of damping forces. The presence of many maxima is noticed which are in general not symmetric, in the intensity distribution as a function of frequency due to the presence of anharmonic terms.
27Al Hyperfine and Quadrupole Interactions for the [A104]0 Center in Quartz
Authors: Bossoli R. B. , Halliburton L. E. 
Published: July 2007

AbstractAn electron‐nuclear double resonance (ENDOR) study at 20 K of the [AlO4]0 trapped‐hole center in α‐quartz gives the principal axes and principal values of the 27Al hyperfine and quadrupole matrices. These are in substantial agreement with previous ESR results obtained by Nuttall and Weil. A model involving both dipole‐dipole interactions and the admixing of unpaired spin into aluminum 3p‐type orbitals is used to explain the small anisotropic 27Al hyperfine matrix components. The “best fit” with this model results in 3.7% of an unpaired spin in aluminum 3p‐type orbitals and a 0.188 nm distance from the aluminum ion to the oxygen ion containing the trapped hole.
Quantum Oscillations of Thermogalvanomagnetic Coefficients in Two‐Dimensional Electron Systems
Authors: Havlová H. , Smrčka L. 
Published: July 2007

AbstractBased on the one‐electron version of the Kubo formula and assuming only the elastic scattering of carriers on static impurities the quantum oscillations of the transport coefficients are evaluated of two‐dimensional electron systems in weak/intermediate magnetic fields. The changes in the oscillating pattern due to the variation of the magnetic field, the carrier density, and the temperature are investigated. Numerical examples give results in qualitative agreement with recent experimental data.
A Model for the Variations in the Field‐Dependent Behaviour of the Poole‐Frenkel Effect
Authors: Choi W. K. , Delima J. J. , Owen A. E. 
Published: July 2007

AbstractThe Poole‐Frenkel effect is often observed in the field‐dependent properties of amorphous materials. Experimentally, it is frequently found that the slopes of log σ versus E1/2 plots differ from that predicted by the Poole‐Frenkel equation and several theorems have been postulated to explain this discrepancy. Recently, Török used the concept of multiple ionisation to account for such discrepancies. In this paper some of the arguments presented by Török and others is examined in more detail, and the Poole‐Frenkel effect is discussed for two limiting cases. The situation when the free carrier density (n) in the case of an n‐type material containing both donor (Nd) and acceptor (Na) impurities, is of the same order of magnitude as Na where the two approximations are invalid, is more closely examined. It is shown that by assuming a field dependent value of n, a transition region situated between the two approximations is evident. It is also shown that by considering basic parameters such as temperature, and acceptor densities, a Poole‐Frenkel plot is obtained which is very sensitive to variations in temperature and acceptor density.
X‐Ray Electron Charge Density Distribution in Silicon
Authors: Pietsch U. , Tsirelson V. G. , Ozerov R. P. 
Published: July 2007

AbstractDuring the last two years new highly accurate X‐ray structure amplitudes for silicon are published. Also the scattering phases of some „forbidden”︁ reflections are determined using the X‐ray threebeam case. This allows the construction of most precise valence and difference electron density plots and the comparision with those calculated on the basis of the Aldret‐Hart X‐ray pendellösung data and by theory. The density plots are discussed in details of both, the bond and the atomic site. The contributions of various Fourier components and the influence of different temperature factors on the difference density are studied.
Fluctuation Unpinning of Dislocations
Authors: Zilberman L. A. 
Published: July 2007

AbstractThe dynamics of thermally activated unpinning of dislocations from point defects under the action of an applied stress is studied. It is shown that the Fokker‐Planck infinite‐dimensional equation describing the diffusion of a particle in the configurational space is reduced to a one‐dimensional one in the concentrated‐force approximation. Moreover it is shown that over a wide range of parameters dislocation unpinning from the point defect occurs in two stages: at the first stage the dependence of the unpinning probability on the initial configuration of a dislocation disappears and at the second stage the system, passes from one stationary state to another. Characteristic times of the problem are found, and their dependence on temperature and dislocation length are studied.
Bound Domain Wall Pairs in Wolffram's Red Salt
Authors: Ichinose S. 
Published: July 2007

AbstractThe relative ordering of the dimerized patterns of neighboring Wolffram's red salt chains is studied with a model where the coupling is due to the interchain Coulomb interaction. It is shown that this mechanism favors antiferromagnetic order between neighboring chains. It also leads to bound domain wall pairs on the same chain. The energy associated with a pair of domain walls increases asymptotically linear with its length.
The Perturbative Influence of Donors and Acceptors on the Value of the Kinetic Coefficient of Electron Transfer along a One‐Dimensional Molecular Chain Achieved by Davydov Solitons
Authors: Ivić (a) Z. , Satarić M. , Žakula R. 
Published: July 2007

AbstractA perturbation theory is developed for the kinetic coefficient of the electron transfer from donor molecules (Dm) to acceptor molecules (Al) along a one‐dimensional molecular chain to which Dm and Al are statistically joined. The influence of donors and acceptors to the soliton states is reflexed to the value of corresponding kinetic coefficient.
Absorption Edge of SnSe
Authors: Lukeš F. , Schmidt E. , Humlíček J. , Dub P. , Kosek F. 
Published: July 2007

AbstractThe absorption of SnSe single crystal is studied near the absorption edge at 95 and 295 K in polarized light for ϵ |a and ϵ | b, where a and b are crystallographic axes within the cleavage plane. Two indirect transitions (0.907 and 1.01 eV at 295 K) are identified for both orientations and a first direct transition for ϵ | b with E0d = 1.051 eV and for ϵ | a with E1d = 1.236 eV as well, all at 295 K. The temperature coefficients of all transitions are determined also within the range of 95 to 295 K. Also is suggested the interpretation of these results considering the band structure of SnSe given in the literature.
Metallic Systems Containing Crystal‐Field‐Split Impurities. Thermodynamic Properties in the Presence of Magnetic Field
Authors: Kumar S. , Ahluwalia P. K. , Sharma K. C. 
Published: July 2007

AbstractIn the presence of magnetic field H, an investigation is made in second order of the possiblity of an anomalous behaviour in various thermodynamic properties viz. heat capacity, susceptibility etc. existing in dilute magnetic alloy systems. Basically, the anomaly is attributed to the CEF splitting of the impurity level; the H dependence in the heat capacity is linear. Electronic susceptibility also exhibits an anomaly of the type 1n T. These results are found to be consistent with earlier work.
Co Contribution to Anisotropy of R–Co Type Pseudobinaries
Authors: Kąkol Z. , Figiel H. 
Published: July 2007

AbstractThe magnetocrystalline anisotropy of the Y2Co17 compound is caused by Co atoms. The anisotropy is calculated within the point charge model in the crystal field approach. The shielding effects of band electrons are taken into account. The calculations are extended to Y2(Co1−xMnx)17 and Gd2(Co1−xMnx)17 with 0 ≦ x ≦ 0.3. The results of the calculations fit the experimental anisotropy data, describe well the changes of the anisotropy versus temperature and Mn concentration, and are consistent with conclusions concerning the local Co anisotropy drawn from NMR data.
Luminescence Properties of Rb2ZnCl4 and K2ZnCl4 Single Crystals
Authors: Martin A. , López F. J. , Diéguez E. , Agulló‐López F. , Arend H. 
Published: July 2007

AbstractFirst data the on X‐ray‐induced luminescence (RL) and thermoluminescence (TL) spectra in the range 10 to 300 K of K2ZnCl4 and Rb2ZnCl4 are reported. For both the materials, two main emission bands peaking at 280 and 545 nm are observed in the RL spectra. They are proposed to be associated to intrinsic electron–hole recombination processes. The TL spectra show the most intense glow peaks near 205 K for both, K2ZnCl4 and Rb2ZnCl4. The wavelength spectrum of the TL peaks essentially consists of the same bands appearing in the RL spectrum measured at the same temperature. Therefore, the glow peaks should also have their origin in the same electron–hole recombinations.
IR Transmission Investigations of (Bi1−xSbx)2Te3Single Crystals
Authors: Stölzer M. , Stordeur M. , Sobotta H. , Riede V. 
Published: July 2007

AbstractIR transmission spectra are measured at (Bi1−xSbx)2Te3single crystals withx= 0.5, 0.7, 0.9 near the absorption edge at 84 and 300 K. For the determination of the optical constants also the reflectivity of polarized infrared light is recorded in the plasma range at 300 K. The dependence of the free carrier part of the dielectric function on the wave number ϵ(v̄) indicates that acoustic phonon scattering is the dominant mechanism. The interband contribution ϵ(v̄) is interpreted by indirect allowed band transitions. The energy gap and the phonon energies are calculated andlie in a physically reasonable range.
Temperature Dependences of 6A1g → 4A1g, 4Eg(4G) and 6A1g → 4Eg(4D) Absorption Bands in RbMnF3 in Paramagnetic State
Authors: Malakhovskii A. V. , Vasilev G. G. , Morozova T. P. 
Published: July 2007

AbstractThe temperature behaviour of RbMnF3 absorption spectra at T > TN in the region of the transitions 6A1g → 4A1g, 4Eg(4G), and 6A1g → 4Eg(4D) is investigated. Pair–vibronic absorption bands are identified and it is shown that 1. the structure of the spectra in the region of both transitions is caused by the transitions to the 4Eg states, 2. the replicas of the basic lines are caused by excitation of an even number of quanta of odd vibrations, and 3. the theoretical temperature dependence of the intensity of the pair–vibronic absorption describes the experimental results sufficiently well.
An Electron Spin Resonance Study of Cubic Fe3+ in Alkali Chloride Crystals
Authors: Nistor S. V. , Velter‐Stefănescu M. 
Published: July 2007

AbstractCubic Fe3+ is formed by X‐irradiating LiCl:Fe crystals grown in a reactive atmosphere. The spin Hamiltonian parameters are consistent with the Fecub3+ center, earlier observed in AgCl and NaCl, consisting of an interstitial Fe3+ forming a tetrahedral (FeCl4)− complex, the four nearest‐neighbour cation sites being vacant. The superhyperfine structure analysis in samples containing 57Fe enriched iron gives the hyperfine splitting 57A = (9.4 ± 0.5) × 10−4 cm−1. No such center is found in KCl:Fe and RbCl:Fe crystals.
Electrical Resistivity and Thermoelectric Power of Intercalation Compounds MxTiS2 (M = Mn, Fe, Co, and Ni)
Authors: Koyano M. , Negishi H. , Ueda Y. , Sasaki M. , Inoue M. 
Published: July 2007

AbstractThe temperature dependence of electrical resistivity and thermoelectric power of the intercalation compounds of MxTiS2 (M = Mn, Fe, Co, and Ni; 0 ≦ x ≦ 1/3) with layered structures are measured over the temperature range 1.5 to 300 K. These experimental results can be explained by a simple model, which takes into account a temperature‐independent residual term and intra‐ and intervalley scattering by acoustic phonons. It is also shown that a phonon drag effect is effective for the thermopower. The effect of intercalation of 3d metals into TiS2 layers on the electronic properties is discussed.
Cohesion of Solids under Very High Electronic Excitation Conditions
Authors: Wautelet M. 
Published: July 2007

AbstractWhen a solid is subject to an intense electronic excitation, it is expected that its cohesive properties differ from the non‐excited state. The variation of crystal instability temperature, Tc, with the concentration of excited electron–hole pairs is examined theoretically. Using a phenomenological model of electron–phonon–defect interactions, it is shown that Tc decreases quasi‐linearly with increasing electron–hole pair density. The consequences of this on diffraction broadening, threshold energy for transformation, premelting, and optical properties are discussed.
Spin‐Wave Damping in Uniaxial Ferromagnets at the Orientational Phase Transition
Authors: Bulgakov E. N. , Sadreev A. F. 
Published: July 2007

AbstractA damping of spin waves is considered near the orientational phase transition (OPT) in the easy plane ferromagnet in an external magnetic field using the diagram technique for the Hubbard operators. It is shown that in the normal phase where uniaxial symmetry is not broken the damping takes place for nonzero temperature and increases with approaching the OPT point. In the broken symmetry phase the damping of spin waves takes place even at T = 0 and increases with going away from the OPT point.
Electronic Structure of the Ce Systems. II. Results
Authors: López‐Aguilar F. , Costa‐Quintana J. 
Published: July 2007

AbstractSeveral electronic structures are determined of some Ce systems, the effects of the Coulomb correlation analyzed together with the spd/f hybridization by means of the pseudopotential model described in the paper I of this series. Firstly, the electronic structure is determined of the γ‐α‐transition of CeAl2. The features of this isostructural transition are: an increase of the 4f coupling with other bandstates; a widening of the 4f band and a light decrease of the 4f population. All these features are quantitatively determined and it is concluded that the pressure effect is the cause of the loss of the magnetic order and this leads to the increase of the spd/f hybridization, the 4f band broadening, and the decrease of the f‐count. In addition, the electronic structure of CeOs2 is determined whose band structure presents certain similarity with that of the α‐phase of CeAl2 and moreover this compound presents a clear heavy fermion behaviour, including a superconducting transition.
A Quantum Field Theoretical View on the Surface Plasmon
Authors: Kleinert P. 
Published: July 2007

AbstractFrom a quantum‐field theoretical point of view the surface plasmon on a plane is treated as an extended object with an oscillating surface singularity created by the boson condensation of supplementary fields. Due to topological singularities the macroscopic equations describing free electromagnetic fields become inhomogeneous. The surface plasmon dispersion relation results from the steadiness of the surface impedance.
Pressure Effects of Superfluidity in Liquid 3He
Authors: Singh R. A. , Kachhava C. M. 
Published: July 2007

AbstractA sophisticated formulation for the pressure dependence of superfluidity in liquid 3He is established on the basis of the generalized BCS‐theory due to Leggett. The pairinteraction for individual partial waves is obtained by Ostgaard's t‐matrix theory in which derived parameters of Fermi momentum, energy density of states, and effective mass are used. The variable parameter, the cut‐off energy ϵc, is computed by coupling it to reproduce the experimental Tc at zero, melting, and intermediate pressures. The agreement between theoretical and experimental Tc is, in general, quite satisfactory, but depends on the choice of ϵc.
Electron Paramagnetic Resonance (EPR) and Related Magneto‐Microwave Birefringence (MMB) Powder Spectra of Copper Nitrate Cu(NO3)2 · 2.5 H2O
Authors: Gharbage S. , Bissey J.‐C. , Servant Y. 
Published: July 2007

AbstractEPR and related MMB powder spectra of Cu(NO3)2 · 2.5 H2O are recorded at X‐band and room temperature. A good agreement is found with computer simulated spectra. An automatic fitting procedure gives accurate principal values of the g‐factors and linewidths.
Derivation of the Ginzburg‐Landau Equation in the Triplet Local‐Electron‐Pair System
Authors: Li Yan‐Min , Zhang Li‐Yuam 
Published: July 2007

AbstractThe Ginzburg‐Landau equation is derived in the triplet local‐electron‐pair system with the broken‐symmetry mean‐field approximation. Ginzburg‐Landau parameters αGL and βGL are obtained, which have similar forms with those derived by Gorkov in the framework of the BCS theory. It is found that the coherence length ξ(0) is of the order of the pair‐site distance and the penetration depth λ(0) is quite large. The upper critical field Hc2 is also discussed.
Stationary and Resonance States at the Core of a Screw Dislocation and Their Contributions to Electrical Resistivity
Authors: Föckel H.‐J. 
Published: July 2007

AbstractWithin the framework of the pseudo‐potential concept and the field of validity of the Ziman‐formula the contribution to the residual electrical resistivity of a 1/2<111>‐screw dislocation is calculated in a b.c.c. metal (potassium). The perturbation potential is specified for a dislocation model, in which the core is described discretely, on the contrary the surrounding matrix as a non‐linearly elastic continuum. The potential of the dislocation core contains resonance states below the Fermi energy. The contributions to the resistivity caused by these states prove to be in the same order of magnitude as experimental data.
Lattice Dynamics of Tin Tetrabromide
Authors: Zeng W. Y. , Higgs J. F. , Anderson A. 
Published: July 2007

AbstractA simple force constant model is developed and applied to the vibrations of solid tin tetrabromide. Three intra‐ and four intermolecular force constants are adjusted to obtain the best fit to the crystal field splittings and lattice mode frequencies observed by Raman and infrared spectroscopy. Isotopic and molecular distortion effects are also investigated. The dependence of the BrBr interaction on separation is found to be similar for SnBr4 and Br2.
Surface Phonons in Molecular Crystals
Authors: Podoprigora V. G. , Remizov I. A. , Shabanov V. F. , Botvich A. N. 
Published: July 2007

AbstractThe lattice dynamics of the surface layers of anthracene and β‐paradichlorobenzene crystals as well as of the adsorbed monolayer of paradibromobenzene on β‐paradichlorobenzene is investigated using the method of atom—atom potentials in slab dynamical calculations. The dynamic, structural, and electro‐optical parameters of the surface crystal layers are compared with those for the bulk.
The Impurity States in Bismuth
Authors: Bodiul P. P. , Garabazhiu V. F. , Gitsu D. V. 
Published: July 2007

AbstractThe influence of a lattice deformation and the degree of valency states filling of the impurity atom on the impurity subsystem behaviour is investigated. The states are found in which the electron is localized in the region of the impurity centre and their energies are evaluated. The size of this region is of an order of 1 to 2 cell size. A mechanism of mixing these states, forbidden in a free atom, and which allows to treat these states as nonstationary, is discovered.
Pressure Dependence of Electrical Resistivity in Intercalation Compounds MxTiS2 (M = 3d Transition Metal)
Authors: Inoue M. , Koyano M. , Fukushima K. , Negishi H. , Sasaki M. 
Published: July 2007

AbstractElectrical resistivities of intercalation compounds of MxTiS2 (M = Mn, Fe, Co, and Ni; x = 0.05) with the 1T‐CdI2‐type layered structure are measured under hydrostatic pressure up to 15 × 108 Pa over the temperature range 1.7 to 300 K. The resistivity change with pressure at room temperature and the temperature dependence at constant pressure are strongly dependent on the guest 3d metals. These experimental results can be explained by taking account of the pressure dependences of the residual resistivity, as well as the temperature‐dependent intra‐ and intervalley scatterings by acoustic phonons.