bluuebunny/crossref_metadata_2025_split huggingface dataset:
Successive Phase Transitions in (NH4)3H(SO4)2 and (ND4)3D(SO4)2 Crystals Studied by EPR of the VO2+ Ion and SeO Radical
Authors: Minge J. , Waplak S. 
Published: July 2007

AbstractThe successive phase transitions of (NH4)3H(SO4)2 crystal and its deuterized analog are studied from 90 to 420 K using VO2+ ion and the SeO radical as EPR probes. On the basis of EPR experiments with ferroelastic domain switching in phase II, a new model of the VO2+ complex in the crystal is proposed, with VO2+ occupying an NH (I) vacancy and able, at high temperatures, to reorient very extensively coordinating in three ways with four of the nearest six oxygen atoms. Gradual hindering of NH reorientation with decreasing temperature enables reorientations in the sublattice of SO ions and is invoked as being the reason of all the transitions occurring below room temperature. Gesi's crystal model of two oppositely polarized NH sublattices in phase III, as well as the ferrielectric nature of the spontaneous polarisation of phases VI and VII, are confirmed. The VO2+ complex line splitting in phase VI of the deuterized crystal behaves similarly as the anomalous temperature dependence of spontaneous polarisation observed by Osaka et al.
Application of the Cluster Size Distribution in Binary Randomly Disordered Finite Chains. Exact Solution of the Random Walk Problem for a Finite Chain with an Arbitrary Concentration of Pure Absorbers
Authors: Onipko A. I. 
Published: July 2007

AbstractA closed form is obtained of the length distribution of open and closed clusters in binary randomly disordered finite chains and its first three moments are calculated. It allows to express configurational averages of interest in chains with randomly distributed broken bonds, with randomly distributed infinite masses and related finite disordered systems and to calculate them exactly. A particular case of random walks on a chain with chaotically distributed pure absorbers is considered without any restrictions on the chain length and the number of absorbers. The exact expressions of the averaged survival probability and averaged lifetime of a particle in the chain are obtained and discussed.
A First‐Principles Pseudopotential Model for the Strong Intrasite Interaction Applied to the 4f13 Configuration (Yb2O3)
Authors: Löpez‐Aguilar F. , Costa‐Quintana J. 
Published: July 2007

AbstractThe intrasite e—e interaction is included within the band structure model by means of a first principles pseudopotential method which is valid for integral and non integral configuration. The pseudopotential is applied to Yb2O3, appearing in the semiconducting phase when one takes into account the screened 4f—4f interaction. The conduction band after the metal—semiconductor transition corresponds to the fulfilled 4f shell and this seems clearly mixed with the p, d bands. Moreover, the mechanism is analyzed for the delocalization and spread of the 4f excited states.
Conduction Electron Scattering by a Short‐Range Ordered Metal Surface
Authors: Kogan E. M. , Gornostiriev Yu. N. , Ustinov V. V. 
Published: July 2007

AbstractThe interaction of conduction electrons with the impurity atom lattice on a metal surface is investigated. The lattice is suppossed to be short‐range ordered and long‐range disordered. It is proved that the electron reflection from the surface can be described in terms of the linear boundary conditions and the scattering probabilities employed in this condition are calculated. If the correlation length of the lattice is large enough, the surface scattering is analogous to multichannel specular reflection.
Defect States in Pb1−xSnxTe
Authors: Lischka K. , Durstberger R. , Lindemann G. , Staudinger H. 
Published: July 2007

AbstractNew experimental data of trap centres in Pb1−xSnxTe are presented. The chemical trend of the trap activation energy is determined for 0 ≦ x ≦ 0.11. The optical ionization energy of the defect level is obtained from the threshold wavelength of impurity photoconductivity and the results are compared with the thermal activation energy of the trap states. The cross sections of the defects for electron and hole capture, which were not measured in PbTe so far, are obtained from an analysis of photoconductivity transients. Our new data indicate a strong localization of the observed trap states in real space and bonding by the short range central‐cell defect potential.
Multipole Theory of the Polarization of Solids by Point Defects. II. The Point Charge Approximation
Authors: Kantorovich L. N. 
Published: July 2007

AbstractThe method for calculating the polarization energy of crystals by point defects presented and developed in the first part of the paper is applied to concrete single defects (vacancies, Vk centres) in alkali halides. (The point‐charge approximation is used.) The continuous approximation involved is examined in detail for a vacancy as an example, the results obtained are compared with the exact calculations of polarization energy and dipole moments. The formation energies of vacancies in six alkali halides are estimated. The semiempirical INDO cluster calculation of the Vk centre being accompanied with an additional polarization calculation is used to obtain the equilibrium distance within the Cl quasimolecule in KCl.
Thermodynamics of Stress‐Induced First‐Order Phase Transformations in Solids
Authors: Kato Masahar , Pak H‐R. 
Published: July 2007

AbstractThermodynamics of deformable solids is first discussed to derive fundamental equations by taking into account the clear difference between elastic and plastic deformation. The theory is applied to discuss the thermodynamics of stress‐induced first‐order solid—solid phase transformations and the general form of the Clausius‐Clapeyron equation is derived.
The Lattice Dynamics of Solid HCl and HBr in Their Low‐Temperature Phase
Authors: Chang Chia‐Nan 
Published: July 2007

AbstractA model of the lattice dynamics of solid HCl and HBr is proposed. It is found that a model, using seven interatomic force constants in the harmonic approximation, is capable of giving good agreement between the observed and calculated zero‐wavevector frequencies. The calculated result shows that the forces between atoms in different chains and different planes are much weaker than those between nearest neighbours in the same linear chain. The values of the calculated optimized force constant β also indicate the strength of the hydrogen bond in these crystals.
The Infrared, Raman, Resonance Raman Spectra, and the Valence Force Field of the HfS3 Layer‐Type Compound
Authors: Gwet S. P. , Mathey Y. , Sourisseau C. 
Published: July 2007

AbstractThe infrared and Raman spectra (600 to 10 cm−1) of polycrystalline samples and of single crystals of HfS3 are investigated. A complete assignment is proposed and the frequencies of normal modes in HfS3, ZrS3, and TiS3 are compared. Resonance Raman spectra of HfS3 are recorded using a variety of Kr+, Ar+, and stilbene‐3 dye‐laser lines (647.1 to 431.2 nm) within the contour of the lowest allowed excitonic transitions. In agreement with previous studies on ZrS3, the unresolved excitation profiles are well accounted for by a Franck‐Condon scattering mechanism in which several modes and several interfering electronically excited states are involved. Finally, a valence force field with intrachain, interchain, and interlayer contributions is proposed: the potential energy distributions and mean square vibrational amplitudes are computed and the force‐constant values are compared in HfS3 and ZrS3 compounds. It is concluded that the lattice dynamics are governed by the two‐dimensional or layer‐type character of these MS3 systems.
Superconducting Properties of Rare‐Earth Amorphous Alloys
Authors: Borchi E. , De Gennaro S. 
Published: July 2007

AbstractThe superconducting transition temperatures are examined of dilute amorphous La80−xNdxAu20 and La80−xPrxAu20 compounds for which careful experimental data are available. For La80−xPrxAu20 compounds the calculation lends support to the belief that the Pr ions lie in a singlet ground state and that the local structure is very near an easy‐plane symmetry. In particular it is suggested that small changes in the local structure can explain the behaviour of La80−xPrxAu20 compounds; however also the possibility is considered that exchange interactions between Pr ions can produce relevant effects. For Kramers Nd ions, on the other hand, the analysis is not able to state precisely the short‐range amorphous structure.
Carrier Heating in Lead Chalcogenides
Authors: Giese B. , Mocker M. 
Published: July 2007

AbstractSeveral carrier heating mechanisms in lead chalcogenide semiconductors are discussed on the basis of a drifted Fermi distribution. Taking into account scattering processes on renormalized optical phonons, acoustic phonons, and impurities, numerical results are presented for the drift velocity in an electric field and compared with experiment. The increase in carrier temperature is given in the case of optical excitation and carrier injection. All calculations are performed within the Kane‐band structure model.
Optical and Magnetic Circular Dichroism Study of the 2D Antiferromagnet Rb2MnCl4
Authors: Vervoitte A. , Canit J. C. , Briat B. , Kambli U. 
Published: July 2007

AbstractA previous optical work on the 4T2(D) state of Rb2MnCl4 is extended to all other states in the visible‐near UV region and completed by magnetic circular dichroism (MCD) measurements. Magnetic dipole origins are located for the 4E(G), 4T2(D), and 4T1(P) states. Magnon sidebands are observed at 80 cm−1 for all states but 4T2(G), in good agreement with the known zone‐edge magnon frequency. Exciton‐magnon interaction is found to be negligible. The dominant orbital character of each exciton is characterized by means of either the associated MCD or the polarization of magnon sidebands. The effects of the tetragonal distortion and spin‐orbit coupling on the various orbital triplets is discussed.
Energy Transfer Processes in (Zn, Mn)S Mixed Crystals
Authors: Goede O. , Thong Dang Dinh 
Published: July 2007

Abstract(Zn, Mn)S mixed crystals with Mn concentrations up to 32 mol% and electron‐beam evaporated (Zn, Mn)S thin films are studied by photoluminescence emission, excitation, and decay measurements in the temperature range2 to 300 K. Besides the usual yellow an additional red emission band is observed with the same excitation spectrum. The measured characteristic temperature and Mn‐concentration dependence of the intensities and decay times of both bands are quantitatively discussed on the basis of an effective‐lifetime model assuming a radiationless resonance energy transfer from the primarily excited Mn2+ ions via several other Mn2+ ions finally to red emission and nonradiative centres, respectively. This model is further supported by the measured time dependence of the pulse‐excited red emission intensity reaching its maximum only after a Mn‐concentration dependent delay time. Characteristic parameters of the energy transfer between the Mn2+ ions are determined. The nature of the red emission centres is discussed, especially in connection with the occurrence of octahedrally coordinated Mn2+ ions at high Mn concentrations.
Correlation Effects in the Rotationally Invariant Asymmetric Anderson Model
Authors: Martínez G. , Ramírez R. 
Published: July 2007

AbstractThe asymmetric single orbital Anderson model is examined in the contextof formation of localized magnetic moments. Full rotational invariance is preserved in a treatment which completely includes d—d correlations and is perturbative in the hybridization parameter V. Finite values for the host bandwidth B are considered. Physical quantities such as the average occupation number of local electrons, spectral density functions, and the mean square value of the magnetization are evaluated for the single‐occupied ground state of this system at zero temperature and for general asymmetry. These quantities are found to be continuous functions ofthe model parameters. It is argued the strongly asymmetric case, relevant for mixed valence situations, is hard to reach. Numerical results are given in the weak coupling asymmetric regime and compared to other variational approaches.
Absorption Edge Anomalies in Polar Semiconductors and Dielectrics at Phase Transitions
Authors: Zametin V. I. 
Published: July 2007

AbstractThe anomalous behaviour of the exponential absorption edge in polar materials in the vicinity of phase transition is treated phenomenologically. It is shown, that changing of electron—phonon interaction at phase transition results in an essential change of the absorption edge shape. The theoretical results are illustrated on a wide range of objects and types of phase transitions.
Splitting of Core‐Level XPS Lines of Transition‐Metal Ions in Compounds and Moment of the Lines
Authors: Okusawa M. 
Published: July 2007

AbstractXPS spectra of the 3s, 2p, and 3p levels of the transition‐metalions in the chlorides and the bromides of 3d transition metals as well as an oxide and a sulfide are studied. The second and third moments of the 2p and 3p spectra in the chlorides and the bromides are compared with the values calculated by Satoko and Sugano. The avilability of the moments of the spectra in the analysis of core‐level lines is indicated.
Energy Levels of Sm2+ in BaClF and SrClF Crystals under Magnetic Field II. Results
Authors: Kibler M. , Gǎcon J. C. , Grenet G. , Jacquier B. , Brunel L. C. 
Published: July 2007

AbstractThe theoretical models and their accompanying procedures described in the first paper of this series are applied to the interpretation of the fluorescence spectrum under magnetic field of Sm2+ in BaClF and SrClF. The good agreement between theory and experiment testifies to the quality of the parameters involved in the zero‐field Hamiltonian.
Dynamics of the Optical Excitation—Deexcitation Cycle of O2− Centers in KCl
Authors: Schwan L. O. , Florian R. , Schmid D. , Betz E. , Schrof W. , Walker B. , Port H. 
Published: July 2007

AbstractThe time dependence of the fluorescence of O−2 centers following picosecond‐pulse excitation is studied. The risetime of the spontaneous fluorescence yields an upper bound for the relaxation time in the excited state: τ*R < 20 ps. The fluorescence decay time decreases from 92 ns at 4.2 K to 50 ns at 300 K. By comparing the results to superfluorescence experiments a lower bound for the relaxation time in the ground state is obtained: τR ⪆ 50 ps.
Model Calculations for Bound Excitons and Bound Excitonic Molecules in GaAs1−xPx:N
Authors: Müller H.‐J. , Wünsche H.‐J. 
Published: July 2007

AbstractA calculation of several properties of excitons and excitonic moleculesbound to the isolated nitrogen impurity in GaAs1−xPx is presented. For the first time the short‐range nature of the impurity potential, the multivalley‐structure of the conduction band as well as the mutual particle—particle interactions are taken into account. A specific formulation of the density‐functionalformalism which is briefly outlined is used for calculating binding energies and spatial structure of these complexes. Influence of disorder is neglected but will be studied in a forthcoming paper. The results support the tentative interpretation of the NΓ‐x−line as originating from excitonic molecule recombination bound to N isoelectronic trap.
Investigation of the Weak‐Field Charge Transport in Semiconducting V2−VI3 Compounds with Trigonal Symmetry II. Interpretation of the Weak‐Field Charge Transport in Sb2Te3 Single Crystals
Authors: Stordeur M. , Simon G. 
Published: July 2007

AbstractIt is succeeded for the first time to interpret the thermoelectric and galvanomagnetic effects, in terms of a nonparabolic six‐valley one‐valence band model and anisotropic mixed scattering on acoustical phonons and ionized impurities and also the magnitude of thermomagnetic effects and the Lorenz numbers for Sb2Te3 single crystals in dependence on temperature between 100 to 300 K using physical relevant microscopic transport data. By a numerical analysis the effective main axis masses mHii, the tilt angle of Fermi ellipsoid ϑ, the masses m ⟂ c, m ‖ c, the density of state effective mass md, the mobilities u ⟂ c, u ‖ c, and the carrier density ptot are calculated. Also the Fermi level EF, the relaxation time factor τac0, the mixture parameters BHi and theparameter of nonparabolicity β are given. The calculated values are ingood agreement with the corresponding data found by using optical effects at 80 K and 300 K.
Raman Study of Mono‐, Di‐, and Trimethyl Ammonium Hexachlorostannates
Authors: Ghozlen M. H. Ben , Mlik Y. , Daoud A. 
Published: July 2007

AbstractThe low‐frequency Raman spectra (0 to 350 cm−1) of (CH3NH3)2SnCl6: 1 MHS, [(CH3)2 NH2]2 · SnCl6: 2 MHS and [(CH3)3NH]2SnCl6: 3 MHS are recorded on single crystals at room temperature. The spectra are assigned on the basis of group theory analysis of vibrations and in view of the previously reported structural data of these hexachlorostannate compounds. The effect of site symmetry on the internal vibrations of the SnCl octahedra are discussed; the distortions of the SnCl octahedra are taken into account in the expressions of the Raman tensors relative to their internal modes.
Effect of Hydrostatic and Uniaxial Pressure on Structural Properties and Raman Active Lattice Vibrations in Bi2Te3
Authors: Kullmann W. , Geurts J. , Richter W. , Lehner N. , Rauh H. , Steigenberger U. , Eichhorn G. , Geick R. 
Published: July 2007

AbstractThe lattice parameters of the hexagonal unit cell, the atomic parameters, and the shift of the Raman active vibrations are measured of p‐Bi2Te3 under uniaxial and hydrostatic pressure. The structural investigations are performed by neutron diffraction, and the lattice vibrations are studied by Raman scattering. The results of the diffraction experiments constitute a direct experimental confirmation of the weak bonding between the sandwiches in this narrow gap semiconductor with sandwich structure. As a consequence, some Raman active phonon modes show a rather strong dependence upon uniaxial pressure up to Δṽ/Δp = 1.9 × 10−8cm−1/Pa.
Excess Solute Atmosphere Carried by a Potential Well Characteristic of a Moving Dislocation Core
Authors: Fuentes‐Samaniego R. , Hirth J. P. 
Published: July 2007

AbstractAn expression is obtained for the excess solute atmosphere carried by a potential well characteristic of a dislocation core and moving at constant velocity in a solid solution. The results agree with the predictions of the dissipation theorem at limiting low values of the velocity. Results for all velocities are presented which can be interrelated with the drag force exerted by the excess solute on the well through the Einstein mobility relation.
The Recoil Effect on the Electronic Stopping Power of Solids for Slowly Moving Atoms
Authors: Shindo S. 
Published: July 2007

AbstractThe velocity dependence of the electronic stopping power of solids for low velocity atoms is discussed. It is shown that the stopping power contains not only the velocity‐proportional term (friction term) but also the velocity anti‐proportional term (recoil term). Calculations of the stopping power using the Born approximation, phase shift, and the Anderson model are presented.
Polariton Effect in Non‐Linear Acousto‐Optical Phenomena
Authors: van Hieu Nguyen , Tan Ha Vinh 
Published: July 2007

AbstractThe role of polariton intermediate states in non‐linear acousto‐optical phenomena is studied. The matrix elements of the interaction processes acoustic phonon + photon → photon + acoustic phonon, photon → photon + 2 acoustic phonons are derived. The contribution of the effective photon–exciton transition is taken into account in any order. Then the exciton intermediate states are replaced by those of the corresponding polaritons. The damping is not neglected.
The No‐Phonon Luminescence at 0.793 eV from Si:Au. Uniaxial Stress and Zeeman Spectroscopy Experiments
Authors: Thébault D. , Barrau J. , Armelles G. , Lauret N. , Noguier J. P. 
Published: July 2007

AbstractUniaxial stress and Zeeman spectroscopy experiments on the no‐phonon luminescence at 0.793 eV from Si:Au confirm the hypothesis of a transition from shallow “hydrogen‐like” levels towards the deep donor level. The initial states are the split valley–orbit 1s: (2T2 + 2E). The experimental results suggest a D2d symmetry group or one of its subgroups.
Two‐Photon Luminescence Excitation Spectra of Eu3+ in Yttrium Aluminium Garnet
Authors: Kholodenkov L. E. , Makhanek A. G. 
Published: July 2007

AbstractThe results are reported of the first study of the 5D2 manifold of Eu3+ in the noninversion and inversion centres of YAG using the method of two‐photon luminescence excitation. Based on the number of Stark components and the two‐photon polarization dependences it is shown that the set of Stark components of 5D multiplet corresponds to tetragonal local symmetry. The components of 5D2 manifold are identified and the crystal field parameters are found for the non‐inversion centre. The europium ion distribution over the centres is determined showing that at least 60% of the ions are in the inversion centre.
Thermopower and Thermomagnetic Effects of Hot Carriers under Conditions of Mutual Electron–Phonon Prag
Authors: Babaev M. M. , Gasymov T. M. , Katanov A. A. 
Published: July 2007

AbstractThe thermopower and the thermomagnetic effects of hot carriers in non‐degenerate semiconductors are studied taking into account both, a mutual drag and heating of the electrons and phonons. The cases when a thermal reservoir for the long‐wavelength phonons is or is not present are considered. It is shown that the mutual drag leads to a strong increase of the thermopower V = Ve + Vp and of the electron part of the Nernst‐Ettingshausen (NE) voltage Ue. Moreover the drag produces a very strong dependence of these effects on an external heating electric field E. For instance if a thermal reservoir is present Ve ≈ E4/3 and Vp ≈ E10/3 under the conditions of electron and phonon strong mutual drag. Presence or absence of the thermal reservoir influences the phonon part of the NE voltage Up essentially. For example in presence of the thermal reservoir Up = 0, while in its absence Up is non‐zero and grows rapidly on raising E: Up ≈ E26/9.
Annihilation of Frenkel Pairs in B.C.C. Metals (α‐Iron). I. The Case of the Unstressed Lattice (General Consideration)
Authors: Ratishvili I. G. 
Published: July 2007

AbstractA model describing the Frenkel pair annihilation process is presented. There are postulated two factors governing the annihilation rate: the distribution function X(r), giving the initial relative spacing of components of a Frenkel pair, and the distribution function F(r), describing the field of potential barriers in the vicinity of a vacancy–interstitial pair. The analytical form of X(r) and F(r) functions is formulated and general expressions of the Frenkel pair annihilation rate and separation rate are obtained.
The Distribution of the Exchange Magnetic Fields in Spin Glasses. The Account of Local State Probabilities
Authors: Vladimir M. I. , Moskalenko V. A. , Skafaru V. V. 
Published: July 2007

AbstractThe distribution of the internal magnetic fields in spin glasses at non‐zero temperatures is obtained. The fact, that the spin glass phase has a huge number of local minima and that each minimum participates in the configurational averaging of the physical quantities with its own statistical weight, is taken into account. It is shown, that the probability distribution of the exchange fields in all sites does not factorize upon the sites because of the interferentional terms belonging to different sites. Detailed calculations are carried out for the homogeneous (white) averaging and for the averaging with the canonical weight multiplier exp {s/kβ}.