bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Dependence of ESR Spectra of Doped Amorphous Germanium
Authors: Stutzmann M. , Stuke J.
Published: July 2007

The temperature dependence of g‐value, linewidth, spin density, and spin‐lattice relaxation time are investigated for the three different paramagnetic states in doped amorphous germanium prepared by the glow discharge technique. The dangling bond resonance shows no temperature dependence of g‐value and linewidth. For the resonance due to localized electrons in the conduction band tail the g‐value and particularly the linewidth increase with temperatures above 150 K in highly phosphorus‐doped samples. The increase in linewidth is attributed to the coupling of the spins to electrons in extended states resulting in short spin‐lifetimes. For the resonance of localized holes in the valence band tail, however, g‐value and linewidth decrease above 100 K. In this case the lifetime broadening is overcompensated by a decrease of the g‐spectrum linewidth. From the temperature dependence of the spin density Ns the effective correlation energy U of the three states is derived. In the case of the dangling bonds the value U = 0.1 eV obtained from the energy dependence of Ns is confirmed. The corresponding values for holes and electrons localized in the band tails are 20 to 30 and 5 to 10 meV, respectively. The spin‐lattice relaxation time shows for dangling bonds and localized holes a T−2 temperature dependence down to 5 K which is attributed to two level systems modulating the spin‐orbit coupling. For electrons in the conduction band tail below 15 K a T−7 dependence is observed.
The Relativistic Linear Muffin‐Tin Orbital Method Application to Au
Authors: Nemoshkalenko V. V. , Krasovskii A. E. , Antonov V. N. , Antonov Vl. N. , Fleck U. , Wonn H. , Ziesche P.
Published: July 2007

Starting with the Dirac equation the relativistic version of the linear muffin‐tin orbital method (RLMTO) is developed. It is considerably faster than the non‐linear RAPW method. Application to the band structure of Au shows, that the results (valence band energies) of both methods deviate in the average by only 0.004 Ryd from each other.
N‐Interface Problem Revisited
Authors: Davison S. G. , Sulston K. W.
Published: July 2007

The general Dyson equation is derived for an N‐interface system within the tight‐binding approximation. An iterative procedure is developed, by means of this equation, which enables closed, well‐defined expressions to be found for the interfacial Green functions at atomic sites on either side of any interface in an N‐interface system.
Studies on Quantum Percolation
Authors: Chaturvedi Meena , Srivastava Vipin
Published: July 2007

Studies on the localisation in binary alloys (commonly termed as ‘quantum percolation’ problem) are reviewed highlighting the special features that this simple model has and which are absent in other models — the most prominent among them being the existence of extended states at infinite disorder. Some new scaling arguments are also reported that enable to predict qualitatively the behaviour of the participation ratio as function of concentration of one of the constituents of the alloy. These are substantiated by numerical simulation results. After summarising all'important approaches and their results, one of the important conclusions drawn is that in two‐dimensional binary alloys not all states are localised at any disorder, contrary to a recent belief.
Study of Optical Relaxation and Inhomogeneous Distribution Function of Impurity Organic Molecules by Site‐Selective Laser Spectroscopy
Authors: Sapozhnikov M. N. , Alekseev V. I.
Published: July 2007

Site‐selective excitation of luminescence and hole burning in the absorption spectra are used for a study of the electronic and vibrational relaxations and inhomogeneous distribution function for coproporphyrin III molecules in solid ethanol and n‐octane matrices in the temperature range from 3.2 to 26 K. From the structural luminescence spectra obtained at the site‐selective excitation the vibrational frequencies of coproporphyrin in the ground and excited electronic states are measured. The temperature broadening of the homogeneous, purely electronic zero‐phonon line investigated by hole burning is mainly determined by the two‐phonon Raman scattering of low‐frequency phonons with the effective frequency 35 cm−1 while its residual width at 0 K results from the anharmonicity of the matrix vibrations. The pure dephasing time T obtained from the homogeneous, purely electronic zero‐phonon linewidths changes from 17.6 to 53.0 ps at T = 3.5 K to 2.8 ps at T = 25 K. The phase relaxation time T2 measured from the homogeneous linewidth of the vibronic level in the excited electronic state is equal to 2.4 ps at T = 3.5 K.
Te Formula for Strong‐Coupling Superconductivity in Random Narrow‐Band Alloys
Authors: Beckmann A. , Kolley E. , Kolley W.
Published: July 2007

The transition temperature Tc of strong‐coupling superconducting alloys AcB1‐c is determined with emphasis to tight‐binding. Local random Eliashberg‐type equations are configuration averaged by means of an effective mass operator on the basis of the CPA. Contrary to the McMillan form the resulting Tc formula involves two different phonon‐mediated coupling parameters. The electron‐phonon mass enhancement is originated from a complex renormalization factor.
Einbau und Diffusion von Cu(I)‐Ionen in CsI anhand von NMR‐Messungen
Authors: Budde K. , Richtering H.
Published: July 2007

Es werden die Ergebnisse von Kernresonanz‐Untersuchungen zur Diffusion in reinem und CuI dotiertem CsI vorgestellt. Ein Einfluß der Dotierung auf die Linienverschmälerung der beiden Kerne 127I und 133Cs wird nicht beobachtet. Aus dem Verlauf der Linienverschmälerung folgt, daß zwischen 200 und 360 °C die mittleren Sprungfrequenzen beider Wirtsteilchen von gleicher Größenordnung sind. Die mittlere Sprungfrequenz der Cu+‐Ionen kann aus der Lebensdauer‐Verbreiterung der 127I Kernresonanz‐Absorptionslinie ermittelt werden. Sie ist nur unwesentlich größer als die der Wirtskationen und zeigt eine ähnliche Temperaturabhängigkeit wie diese. Aus den Resultaten der Kernresonanz‐Messungen wird der Schluß gezogen, daß Cu+‐Ionen in CsI substitutionell eingebaut werden und dem gleichen Diffusionsmechanismus wie die Cs+‐Teilchen folgen.
On the Influence of the Magnetic Ordering on Thermodynamic and Electrical Properties in the Hubbard Model
Authors: Schumacher W.
Published: July 2007

The specific heat and the electrical conductivity are calculated in the Hubbard model in Hartree‐Fock approximation (HFA) for an antiferromagnetic ordering and for arbitrary band filling using the antiferromagnetic solutions which are found in HFA and which are established with respect to the existence of double solutions of the Néel temperature in the framework of a theory taking into account fluctuations of the spin.
Multiphonon Structure of Optical Transitions to Impurity Resonance States. The Influence of Anharmonicity
Authors: Suisky D.
Published: July 2007

Expressions are derived for the absorption coefficient of substitutional impurities taking into account resonant impurity states and anharmonicity of lattice vibrations. In both the cases the lineshape of the absorption band is modified due to broadening effects. It can be shown that the contribution due to anharmonicity is not only remarkable, but dominates under certain conditions, for example, in the case of strong electron‐phonon interaction.
Calculation of the Exoelectron Energy Spectrum for NaCl
Authors: Gerasimov A. B. , Merkin M. M. , Tsertsvadze A. A.
Published: July 2007

A quantum‐mechanical calculation of the probability of an elementary exoelectron emission (EEE) act from a NaCl crystal is made. The mechanism previously suggested by the authors is used, according to which the emission takes place at the expense of the energy released at exoenergetic reactions between defects. The calculations are made for the particular case of annihilation of the F‐centre with a negative halide atom. There is good agreement between theory and experimental results.
Thermodynamics of Superconducting Alloys with Localized States in the Energy Gap
Authors: Schossmann M. , Schachinger E.
Published: July 2007

A general formula for the energy difference between superconducting and normal states of an alloy with paramagnetic impurities is developed on the basis of the Shiba‐Rusinov theory. The result is used to calculate the thermodynamics of the alloys In‐Mn, In‐Cr, and Pb‐Mn. It is shown that the deviation function is particularly sensitive on the position and number of localized states for all possible impurity concentrations. Finally, a comparison of theoretically calculated specific heat values for In‐Mn with experimental results demonstrates a satisfactory agreement.
Resonances and Averaged Forces in Bounded Semiconductor Plasmas
Authors: Nikolov N. A. , Malinov P. N.
Published: July 2007

The density distributions of the current carriers and their velocities in a bounded semiconductor plasma are found on the basis of the two‐component MHD. The semiconductor plasma is placed between two metal electrodes. The averaged forces of Miller's type, which act on the current carriers, are found. The resonance frequencies are found at which the averaged forces increase and the densities have a modulation maximum. The possibility of experimental observation of “hole sound”‐type resonances is discussed.
FIR Studies of OCN−, SCN−, and SeCN− Centre Gap Modes in KI Single Crystals
Authors: Otto J. , Fischer F.
Published: July 2007

Several sharp absorption lines within the frequency range of the phonon gap of KI are shown to be due to the chalcogenocyanate centres. A resonance mode occuring near the low‐frequency gap boundary is also ascribed to the SeCN− centre. The experimental data are compared with a three‐dimensional model calculation for a monoatomic isotopic impurity centre and with a simple model for the centre of a linear molecular ion. A characterization of the gap and resonance modes is given.
FMR Linewidth in Bulk Metals in Parallel Configuration
Authors: Fraitová D. , Půst L.
Published: July 2007

A formula for the ferromagnetic resonance (FMR) linewidth is presented for the case of isotropic bulk ferromagnetic metals in the parallel configuration, free surface magnetization motion being assumed. The numerical evaluation of the formula agrees with the relative accuracy −0.5 × 10−2 to +1.5 × 10−2 with exact results based on macroscopic FMR theory. The influence of surface magnetization pinning on the linewidth value is also discussed.
Field Ionization of Phosphorus Atoms in Silicon
Authors: Žurauskas S. , Dargys A.
Published: July 2007

Electron tunneling from phosphorus atoms into the silicon conduction band is investigated at cryogenic temperatures in metal—insulator—semiconductor (MIS) structures. To observe field ionization and, at the same time, to exclude other competing processes, such as the impact ionization and the electric‐field‐assisted thermal ionization, the experiments are performed with electrical pulses of several ns duration. Field ionization dynamics after the application of a voltage step, when the tunneling time is comparable to the electron transit time through the structure, is analysed theoretically and compared with the experiment. Since the tunneling time is very sensitive to the parameters associated with the impurity it is argued that field ionization experiments may appear valuable in the investigations of shallow impurity states in semiconductors.
The FH‐Centre Energy Structure in KCl and KBr
Authors: Salomatov V. N. , Parfianovich I. A.
Published: July 2007

The energy parameters of the FH(Br−)‐, FH(O−) — centres in KCl and FH(O−) — centres in KBr are calculated within the framework of perturbation theory. From the comparison of calculated and experimental data the following conclusions are drawn: (1) the long‐wave shift of the F‐centre absorption band in KCl with increasing Br− concentration may be due to the formation of FH(Br−)‐centres whose components are a \documentclass{article}\pagestyle{empty}\begin{document}$ a\sqrt 2 $\end{document} apart (a is the shortest interionic distance); (2) the decay of impurity excitons in KCl‐Br leads to the creation (or the manifestation in the stimulation spectrum) of the FH(Br−)‐centres with components being 2a rather than a \documentclass{article}\pagestyle{empty}\begin{document}$ a\sqrt 2 $\end{document} apart; (3) the change in the optical characteristics of the FH(O−)‐centre as compared to those of the F‐centre in KBr is consistent with the experiment assuming that an O− off‐centre position in the lattice site exists. The possibility of F‐centre RES life‐time lowering is mentioned.
Dielectric Properties of Ice in the Presence of Space Charge
Authors: Petrenko V. F. , Ryzhkin I. A.
Published: July 2007

The effect of the space charge at the contacts on the low‐frequency dispersion of the electrical properties of ice is theoretically investigated. It is shown that in general case there are four characteristic frequencies related to four Maxwell relaxation times of four partial conductances of defects. The real part of the dielectric permittivity has dispersion “steps” at characteristic frequencies. An analysis of the step heights and their position in the dielectric spectrum gives valuable information on concentrations and mobilities of charge carriers in ice.
Evaluation of Photoelastic Constants and Strain Derivatives of the Static Dielectric Constant of Silver and Thallium Halides
Authors: Verma T. S. , Kumar V. , Shanker J.
Published: July 2007

A method for calculating the photoelastic constants and strain derivatives of static dielectric constant for silver and thallium halide crystals, which crystallize in NaCl and CsCl structures, respectively, is developed. The shell model formulation, which takes into account the polarizability of positive as well as negative ions and considers also the effect of Lundqvist's three‐body interaction, is used in the present calculation. The short‐range overlap repulsive interactions between first and second neighbours as well as the van der Waals dipole—dipole interactions are also considered in evaluating the short‐range force parameters which are used for the calculation of the photoelastic constants and the strain derivatives of the dielectric constant. The results are found to compare well with available experimental data.
The Contribution of Zero‐Point Vibration toward the Static and Thermodynamical Properties of Potassium Halides
Authors: Singh R. P. , Rana J. P. S. , Varshney G. B.
Published: July 2007

The cohesive energy, molecular force constant, reststrahlen frequency, third‐order elastic (TOE) constants, van der Waal's coefficients, bulk modulus, and its pressure dependence are evaluated for potassium halides using a generalised‐shell model (GSM) in which the zero‐point energy is estimated from a relation used by Narayan and Ramaseshan, and van der Waal's (vdW) coefficients are evaluated by the Slater‐Kirkwood‐variational (SKV) method. The Hafemeister‐Flygare (HF) type short‐range overlap repulsive potential, effective up to second neighbours, is used. The results obtained are in excellent agreement with the experimental data.
On the Dielectric Function of Three‐Level Systems under High Excitation I. Theoretical Approach
Authors: Bigot J. Y. , Hönerlage B.
Published: July 2007

Using the density matrix formalism for a three‐level system, the dielectric function is derived in the presence of two exciting light fields. Different limiting situations are discussed, the approximations involved and their respective validity.
Longitudinal Nernst‐Ettingshausen Effect in Heavily Doped EuO
Authors: Auslender M. I. , Karyagin V. V. , Zolotovitskii A. B. , Kalashnikov V. P. , Gizhevskii B. A.
Published: July 2007

Temperature and magnetic field dependences of the Nernst‐Ettingshausen effect in heavily doped ferromagnetic semiconductors over a wide temperature interval embracing the Curie point are calculated numerically for the material parameters of Eu0.99Gd0.01O. It is assumed that usual Born scattering of current carriers by spin fluctuations dominates. The results obtained agree semiquantitatively with the experimental data.
Warm Electron Coefficient of Two‐Dimensional Electron Gas in Silicon Inversion Layer at Low Temperatures
Authors: Basu P. K. , Roy J. B.
Published: July 2007

Warm electron coefficient of a two‐dimensional electron gas in Si‐MOSFET's is calculated at low temperatures by assuming that the distribution function is characterised by an electron temperature. Bulk acoustic phonon, Rayleigh wave, impurity, and surface roughness scattering mechanisms are considered and the phonon numbers are taken exactly. The present values of β are of the same order as those obtained by other workers, but differ widely from the experimental data. Both positive and negative values of β are obtained in the present calculation, while earlier workers obtained only positive values. Possible reasons for the discrepancies are discussed.
Pinning of a Curved Flux Line by Macroscopic Inclusions in a Type II Superconductor
Authors: Shehata L. N. , Saif A. G.
Published: July 2007

The pinning force is calculated as a function of the distance between a curved (or straight) flux line and the centre of a macroscopic superconducting (or normal) ellipsoidal inclusion. When the ellipsoidal tends to a spherical inclusion the results agree with those previously obtained.
A New Technique for the Evaluation of Densities of States in ab initio Calculations of Periodic Systems
Authors: Angonoa Giuliana , Dovesi R. , Pisani C. , Roetti Carla
Published: July 2007

A recently introduced expansion technique for calculating densities of states (DOS) of crystalline systems is applied for the first time in conjunction with ab initio HF calculations. Graphite, lithium, and beryllium are chosen as test systems; Legendre polynomials are used as the orthogonal expansion set. The quality of the results depends both on the density of the sampling net used for the evaluation of the expansion coefficients, and on the number of terms used in the expansion; the influence of these two parameters is discussed. It is shown that the new technique provides a substantially accurate description of the DOS and related quantities (Fermi energy, density matrix), although it is not able to reveal the fine structure of the spectrum. The computing time is about ten times less than required by conventional techniques of comparable accuracy.
Effects of Excitation Intensity on Photoluminescence of Pure CdTe
Authors: Kim Q. , Langer D. W.
Published: July 2007

The photoluminescence of high purity n‐type CdTe single crystals (n ≈ 2.9 × 1014 cm−3) at liquid helium temperature is studied at different excitation intensities. Emissions due to the recombination of free excitons and excitons bound to neutral donors, ionized donors, and neutral acceptors are discussed as well as the transitions of free carriers to various impurities. Other impurity related spectral features are observed within the range of 120 meV from the band edge and their origin is described in analogy to the present knowledge of the spectra of III‐V and other II‐VI compounds.
On the Optic Vibrational Modes in Amorphous Arsenic
Authors: Lottici P. P.
Published: July 2007

The Raman, infrared, and inelastic neutron spectra on bulk amorphous arsenic are reviewed and compared. The main peak in the polarized Raman spectra does not correspond to a maximum in the neutron density of states and some kind of vibrational selection rules is observed. This behaviour is interpreted in terms of a simple continuous random network model for the a‐As structure in which symmetric stretch (SS) motions, highly correlated through the network, exhibit high Raman activity.
Metallic Quenching of Exciton Luminescence in Anthracene
Authors: Ya. Glushko E.
Published: July 2007

The peculiarities of the molecular crystal luminescence spectrum shape are considered within the framework of the polariton theory; in particular the anthracene luminescence spectrum shape caused by external phonon modes of the crystal is described. Exciton‐phonon interaction including the anisotropy of the anthracene crystal, exciton energy, and phonon modes are taken into account in the microscopic model. Determination of the radiation transmission coefficient of the crystal bordering on metallic films of various widths is performed within the framework of classical crystal optics. The results of computations of the luminescence spectra dependence on temperature, metallic film width, and crystal orientation allow to define the limits of applicability of the anthracene luminescence isotropic model. Qualitative agreement of calculated spectra with experimental data known in literature is received.
EHP Luminescence of GaP:N under Resonant Free‐Exciton Excitation
Authors: Schwabe R. , Staehli J. L. , Streit I. , Thuselt F.
Published: July 2007

The electron‐hole plasma (EHP) luminescence of thin nitrogen doped GaP layers is investigated using a resonant free‐exciton excitation which ensures an absolute homogeneous excitation of the crystals. Spatially resolved measurements of the EHP luminescence give hints that the impurities in a certain doping range induce a phase separation into two degenerated plasma‐like phases whose densities are close together. The results are compared with theoretical phase diagram calculations for an acceptor doped material. An increase in doping level as well as in pump power favours an EHP expansion. Moreover first results of highly nitrogen‐doped GaP (nN = 3.1 × × 1019 cm−3) are presented using the same experimental procedure.
Electron Scattering Interaction and Elementary Excitations in Lead Chalcogenides
Authors: Giese B.
Published: July 2007

Dielectric properties and elementary excitations are discussed in lead chalcogenide semiconductors on the base of the RPA‐dielectric function using a Kane‐band model. Numerical and analytical results are presented for the dielectric function and the elementary excitation spectrum and compared with results for a parabolic model. A sum rule for the spectral function of the phonon propagator is given to calculate the phonon strength of elementary excitations.
Jahn‐Teller Effect in EPR and Optical Absorption Spectra of Cu2+ in LiNbO3 Single Crystals
Authors: Petrosyan A. K. , Khachatryan R. M. , Sharoyan E. G.
Published: July 2007

Optical and EPR spectra of LiNbO3 single crystal doped with copper ions are measured in the range of 200 to 6000 nm and in the X‐band, respectively. In the temperature range 60 to 200 K a transition is observed from the low‐temperature EPR spectra with Cs symmetry (g𝒵 = 2.403, gy = 2.121, gx = 2.095 and = 51°) to the high‐temperature spectrum with C3v symmetry (g′∥ = 2.22, g⟂ = 2.17 and 𝒵 ∥ C3) whose parameters are given by the average of the corresponding parameters of the low‐temperature spectra. EPR spectra of LiNbO3:Cu2+ are interpreted taking account of the static Jahn‐Teller effect in trigonal field and formation of non‐equivalent minima on the adiabatic potential surface. In case of the static Jahn‐Teller effect in trigonal field formulas for the g‐factors of d9 ions are derived theoretically. A new model of Cu2+ substitution in LiNbO3, i.e. formation of a Cu  VLi complex, is suggested. In optical spectra an absorption band at 5000 cm−1 is detected due to Jahn‐Teller splitting of the 2Etr ground state. The Jahn‐Teller stabilization energy EJT = 1250 cm−5 and crystal field parameters 10Dq = 8200 cm−1, ν = −1200 cm−1, and ν− = 600 cm−1 are determined.
Analysis of the Hyperfine Interactions of the Vacancy‐Iodine Complex in ZnSe
Authors: Schrittenlacher W.
Published: July 2007

The ESR line multiplicity of iodine containing ZnSe single crystals obtained after optical excitation is analysed by means of a spin Hamiltonian. A good fit is obtained considering Zeeman energy, hyperfine energy, quadrupole energy, and (pseudo)‐nuclear Zeeman energy with S = ½ and I = 5/2. The fact that iodine consists to 100% of the isotope 127I with I = and that the spectra are described by I = is proof that iodine is an integral part of the complex centre. This is the first time that a ligand hyperfine structure of A‐centres in ZnSe is observed and numerically analysed. Therefore, also the orientations of the different tensors in the spin Hamiltonian are determined with respect to the orientation of the complex centre. Besides the 127I ligand hyperfine structure the 77Se hyperfine and the 77Se ligand hyperfine structure are observed. From the different hyperfine parameters the distribution of the hole wave function is derived and yields ≈ 90% localisation in the sp3‐hybrid lone pair orbitals directed to the zinc vacancy.
Electron Paramagnetic Resonance of Tetravalent Praseodymium in Zircon
Authors: Harris E. A. , Mellor J. H. , Parke S.
Published: July 2007

The electron paramagnetic resonance of Pr4+ in the tetragonal crystal field of ZrSiO4 is measured at 9.9 GHz at temperatures near to 15 K. Hyperfine constants and g‐values are reported which, unlike most other rare‐earth ions in this material, show only weak anisotropy. The spectra are interpreted in terms of a 2F5/2Γ ground state with evidence of mixing to 2F7/2 states.
The Magnetic Field Distribution in Deformed FLL in Type II Superconductors
Authors: Przełożny Z. , Kozłowski G.
Published: July 2007

The elastic properties of the flux line lattice (FLL) in type II superconductor are calculated from the Ginzburg Landau theory for large induction Hc1 ≪ H ⪅ Hc2. It is obtained that the elastic response of FLL to the localized perturbation field is non‐local generally. The change of magnetic field caused by the deformation of FLL is expressed by the integral with kernel vanishing in the distance . It leads to the effective interaction between flux‐lines with range and amplitude proportional to −2. The influence of the surface of the superconductor on FLL deformation caused by the normal inclusions is obtained.
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

The 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

A 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

The 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

The 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

New 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

The 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

Thermodynamics 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

A 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

The 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

The 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

Several 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

A 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

(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

The 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

The 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

XPS 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

The 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

The 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

A 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

It 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

The 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

The 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

An 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

The 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

The 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

Uniaxial 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

The 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

The 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.