bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical Properties and Reorientation of M Centers in NaF
Authors: Collins W. C. , Schneider I. 
Published: July 2007

AbstractThe reorientation efficiency of M centers in NaF is found to be proportional to the M+ concentration, suggesting that M centers reorient via an M+ mechanism, as in KCl. In this mechanism light is first absorbed in the higher transitions of the M centers causing them to ionize, and then in the higher transitions of the M+ centers causing them to reorient. The higher transitions of both the M and the M+ center are identified. In addition, a new absorption band at 516 nm giving rise to emission at 680 nm, seen in lithium‐doped samples, is tentatively identified as due to the lithium MA center.
An Electron Microscope Investigation of the Structure of Some Amorphous Materials
Authors: Chaudhari P. , Graczyk J. F. , Herd S. R. 
Published: July 2007

AbstractThe structure of as deposited thin films of SiO2 and as deposited, as well as heated Si, Ge, and several Ge–Te alloys, has been investigated by transmission electron microscopy and electron diffraction. Using high resolution dark field microscopy it is shown that the structure of all the amorphous specimens investigated comprised of coherently scattering regions 10 to 20 Å in size. The coherently scattering regions are retained until crystallization in the Si, Ge, and GeTe films. In the case of tellurium‐rich Ge–Te alloys, the coherently scattering regions are found to disappear and reappear with temperature cycling. On the basis of the experimental evidence, it is suggested that the conventional microcrystalline model is not a valid description of amorphous materials.
Molecular Orbital Approximation Study of the Co2+ Impurity in ZnSe – Ligand Hyperfine Structure
Authors: Biernacki S. W. 
Published: July 2007

AbstractFor the complex of tetrahedral symmetry given by a Co2+ ion and its neighbours in a ZnSe crystal molecular orbitals are determined by a semiempirical method, The experimental data used were the cubic field splitting parameter 10 Dq and the spectroscopic splitting parameter g. The molecular orbitals are given as linear combinations of the Hartree‐Fock atomic orbitals with appropriate numerical coefficients. They are used for the calculation of the superhyperfine interaction. The results are compared with results of EPR measurements.
A Calculation of the Spin–Lattice Coefficients of Gd3+ in CaO, CaF2, Tho2, and CeO2
Authors: Schlottmann P. 
Published: July 2007

AbstractThe contributions of three mechanisms to second‐order spin‐lattice coefficients of Gd3+ in CaO, CaF2, Tho2, and CeO2, are calculated with a point‐charge approach for the orbit‐lattice parameters. It is seen that for Gd3+ the Blume and Orbach mechanism has not the importance as for the 3d5 ions, Mn2+ and Fe3+. With the Blume and Orbach mechanism, a relativistic second‐order and a mechanism of fourth order a sign agreement for both coefficients of Gd3+ in CaO and for the tetragonal coefficient in the other lattices is obtained, but not for the trigonal distortions.
Dislocations in Piezoelectric Semiconductors
Authors: Faivre G. , Saada G. 
Published: July 2007

AbstractPrevious results on dislocations in piezoelectric insulating crystals are extended and the possibility of trapping charges at the core of a given dislocation is discussed. The electrical potential associated with a dislocation is explicitly calculated for Te crystals. The case of screening by free carriers in a semiconductor is then treated and a general solution for the potential is given. Physical consequences are described.
Energy Spectrum of a Bound Polaron
Authors: Bajaj K. K. , Clark T. D. 
Published: July 2007

AbstractEnergies of the ground state and of a few low lying excited states of a conduction electron coupled simultaneously to an attractive Coulomb potential and to a longitudinal optical phonon field of the crystal lattice are obtained in analytic forms. The coupling describing the interaction between the electron and the phonon field is assumed to be weak and therefore second order perturbation theory as formulated by Dalgarno and Lewis is used. The values of 1s → 2p and 1s → ∞ transitions thus obtained are compared with those observed experimentally in the far infrared optical absorption in silver halides and semiconducting CdF2 and a good agreement is found. A comparison between the theoretical results, obtained and those of others is presented.
The Eigen‐Frequency of Extended Dislocations
Authors: Kronmüller H. 
Published: July 2007

AbstractExtended dislocations may be excited to internal periodic oscillations. The eigen‐frequencies are found to be proportional to the stacking fault energy and to be of the order of 1010 s−1 for common metals. The effect of several damping mechanisms on these vibrations is investigated quantitatively. Furthermore the possibility of an experimental demonstration of the eigen‐frequencies by means of acoustic resonance experiments is discussed.
Primary Photoemission Spectra of Gold and Their Relation to the Band Structure
Authors: Christensen N. E. 
Published: July 2007

AbstractThe energy distributions (EDC's) of photoelectrons have been calculated from a relativistic band model for photon energies ranging from 3.7 to 13 eV. The structure elements in the EDC's are related to the band structure, and the regions in k‐space contributing to each peak have been traced out. An EDC‐peak does not in general correspond to a critical point, but has contributions from extended regions in the k‐space.
Mechanisms Effecting the Optical Spectra of 4f13 Ions
Authors: Lowther J. E. 
Published: July 2007

AbstractThe splitting of cubic levels by crystal field components of lower symmetry is evaluated with particular reference to the Γ8 quadruplet. Defects and the ion‐lattice interaction are two distorting mechanisms which are investigated. An explanation of the linewidth of Tm2+ :CaF2 is given, and certain features of the Yb3+ :CdS spectrum are discussed.
Dependence of the Symmetry Labelling of Electron and Phonon States in Crystals on Orientation
Authors: Cornwell J. F. 
Published: July 2007

AbstractThe general theory is given of the orientation dependence of the labelling of electron and phonon states in crystals. All types of space group are considered. There is no effect for the space groups with point groups Oh, D6h, D4h, D2h, C2h, and Ci, and for the space groups D and D. The space groups T3 and T5 are studied as examples.
Measurement of Microwave Faraday Effect in n‐Type Silicon
Authors: Srivastava G. P. , Mathur P. C. , Kumar A. 
Published: July 2007

AbstractMeasurements of the Faraday rotation in n‐type silicon have been performed at room and at low (93 °K) temperatures. A crossed‐waveguide technique (18.0 to 26.5 GHz), similar in principle (but in a simplified form) to the technique of Bouwknegt and Volger [4], has been used for the measurements. The rotation has been studied as a function of de magnetic field up to 10 kOe. The effect of multiple reflections has also been studied at low temperatures. The theory of the Faraday effect in anisotropic n‐silicon, previously developed by the authors [3], is modified taking into account the contribution of mixed scattering of lattice and impurities. The modified theory is compared with the experiment, and an estimation is made of the relative importance of the impurity over the lattice scattering. It is shown that impurity scattering gives an appreciable contribution to the rotation.
Hyperfine Magnetic Field at 41K Recoil Implanted in Nickel
Authors: Devare H. G. , De Waard H. 
Published: July 2007

AbstractThe time differential perturbed angular correlation technique was used to measure the hyperfine magnetic field acting on 41K nuclei recoil implanted in nickel by the 41K(p, p′) 41K reaction. From the modulation of the time spectrum of the gamma transition from the 7/2− statc at 1293 kcV, H (K Ni) = (− 19.9 ± 1.2) kG is found. From the unperturbed p2 − 1293 keV gamma ray angular correlation, studied with a silver backing for the 41KBr target, values A2 = 0.246 ± 0.064 and A4 = −0.042 ± 0.103 of the angular correlation coefficients were obtained. The amplitude of modulation of the time spectrum amounts to about 60% of that derived from the unperturbed angular correlation coefficients.
Soft X‐Ray Absorption in CuNi Alloys
Authors: Gudat W. , Kunz C. 
Published: July 2007

AbstractCuNi alloy films have been investigated in the vicinity of the onset of 3p electron absorption in the photon energy range 50 to 90 eV. The spectra obtained can be described as a stoichiometric superposition of the individual Cu and Ni metal spectra. Any rearrangement of the states due to an alloy interaction is of no great influence. This result is in general agreement with results on soft X‐ray emission, uv and X‐ray photoelectric emission. It is in contradiction to the rigid band model and supports more recent alloy theories such as the coherent‐potential approximation. This result, moreover, supports the interpretation of the wide structures in the transition metal spectra as a predominantly atomic effect.
Low‐Temperature Recovery of Magnetic After‐Effect and Electrical Resistivity of Electron‐Irradiated Nickel
Authors: Lampert G. , Schaefer H. E. 
Published: July 2007

AbstractThe recovery of high‐purity nickel electron irradiated at 27 K has been observed by simultaneous measurement of the electrical resistivity and the magnetic after‐effect (MAE). A strong MAE observed at about 55 K anneals out in the substages ID and IE simultaneously with the electrical resistivity. In both stages ID and IE the same value of the activation energy of recovery EM = (0.155 ± 0.02) cV was found from both types of measurement. Models describing the recovery in stages ID and IE in nickel by the annealing of a single type of defect configuration are strongly supported.
Stark Effect of Impurity Centres by the Method of Average Moments
Authors: Gardavský J. 
Published: July 2007

AbstractThe average moments and their changes are calculated independently of the perturbation theory. New electron optical transitions are due to the mixing of degenerate electron states from different energy levels by the Hamiltonian of an externally applied electric field. The average shift of the optical absorption bands is expressed in terms of the linear Stark effect energy changes. The even parity equivalent electrc field, employed in the calculation of the chage of the average second moment may lead to a linear Stark effect of electron states with definite parity.
Partial Structure Factors and Atomic Distributions in Liquid HgIn and HgTl Alloys
Authors: Waseda Y. , Kuroha M. , Suzuki K. , Ohtani M. 
Published: July 2007

AbstractThree partial structure factors, Sij(Q), have been evaluated from the scattered X‐ray intensities of liquid HgTl alloys measured by Halder et al. [7] and of liquid HgIn alloys measured by Halder and Wagner [8] assuming that the Sij(Q) are independent on the relative abundance of the respective elements in the alloys. The functions Sij(Q) are independent on the relative abundance of the respective elements in the alloys. The functions Sij(Q) and Sij(Q) and their reduced radial distribution functions Gii(r) and Gjj(r) obtained are very similar to those observed in their respective pure liquid metals. In both cases the partial Sij(Q) and Gij(r) have maxima which lie in between those of the pure elementes. From these results, liquid HgIn and HgTl alloys seem to be interpreted as random mixing fluids. Besides, the electrical resistivity was calculated using Faber‐Ziman's theory [14] and the pseudopotential of Evans [15] and compared with experimental data.
Eine interpretierbare Formulierung der adiabatischen Näherung
Authors: Zybell E. 
Published: July 2007

AbstractDie allgemeine Theorie der Gitterschwingungen, die von der adiabatischen Näherung ausgeht, wird mit Hilfe einer unitäreb Transformation in eine neue Form gebracht. So ergibt sich ein mathematischer Formalismus, der der physikalischen Interpretation unmittelbar zugänglich ist. Insbesondere läßt sich explizit zeigen, daß die Gitterteichen den Charakter von angezogenen Kernen besitzen. Zugleich gewinnt man eine Vorstellung davon, wie sich diese angezogenen Kerne von den nackten Kernen unterscheiden. Zur Illustration wird schließlich der Grenzfall betrachtet, in dem sich Elektronenverteilungen starr mit den schwingenden Kernen mitbewegen.
Anisotroy Contribution of the Mn3+ Ion and Related Directional Orders in Some Li‐Mn Ferrites
Authors: Marais A. , Merceron T. , Maxim Gh. , Porte M. 
Published: July 2007

AbstractThe magnetic after‐effect, the induced uniaxial anisotropy, and the squareness ratio‐three phenomena due to the directional order‐have been investigated in the ferrite system Li0.45Mnx Fe2. 55−x04+y. The important role played by Mn3+ ions in the directional order formation has been show, resulting from a contribution to the magnetocrystalline anisotropy of Mn3+ ions. The elementary coupling energy of the Mn3+ ion to the lattice has been calculated.
Lattice Dynamics of Cesium Fluoride
Authors: Rolandson Stig 
Published: July 2007

AbstractThe phonon dispersion relations in cesium fluoride have been measured by inelastic neutron scattering in the symmetry directions Δ Σ, and A. The measurements were performed at 80 and 300 K using a three‐axis spectrometer. The experimental results are compared with theoretical calculations based on various models of the interionic interactions in alkali halides. A satisfactory fit was obtained by a seven‐parameter model with only the cesium ion polarizable, and the fit was only slightly improved by using more complicated models with a larger number of adjustable parameters. The frequency distribution has been calculated using an eleven‐parameter shell model with both ions polarizable, and compared with similar calculations based on data from macroscopic measurements.
Thermodynamics of Ferroelectric Solid Solutions (II)
Authors: Yurkevich V. E. , Rolov B. N. 
Published: July 2007

AbstractThe analytical expressions of a number of physical characteristics are obtained for the first‐order phase transition: the phase transition temperature as a function of concentration, polarization, dielectric permeability, and heat capacity. A theoretical estimate of the half‐width of dielectric permeability curve of solid solutions is made and good agreement with the experiment is found.
On Cross‐Relaxation in a Spectrally Inhomogeneous System
Authors: Godenko L. P. , Mashkevich V. S. , Shadchin E. A. 
Published: July 2007

AbstractThe relaxation equations are obtained from the microscopic equations describing the elementary processes of the excitation transfer. The case of a spectrally inhomogeneous system and the resonance excitation transfer is considered. The kinetic equations for average excitation numbers of the centres are derived. The equation of the relaxation type for the spectral excitation density is obtained on their basis. The relaxation term has not the simplest form in which it is proportional to the deflection of the excitation spectral density from the quasi‐equilibrium value.
Mössbauer Dispersion in Paramagnetic Crystals
Authors: Mitin A. V. 
Published: July 2007

AbstractThe Mössbauer γ‐ray dispersion in paramagnetic crystals is discussed in the presence of the electronic relaxation. In particular the case of the nuclear Faraday effect (NFE) is considered. It is shown that the rotation angle of the polarization plane of the γ‐wave is proportional to the population difference of the electron levels and the dispersion spectrum strongly depends on the relaxation time and the electronic population difference. It is also noticed that the axially symmetric quadrupole interaction leads to an asymmetry of the spectrum. The polarization scheme for the NFE observation is analysed.
Luminescence Sideband and Raman Spectra of Oxygen in Solid Argon
Authors: Bruno R. , Jodl H. J. 
Published: July 2007

AbstractThe Raman and luminescence spectra of O2 have been studied in the O2Ar system. A simple model is used for associating the unexplained 417.6 cm−1 Raman spectrum peak for 2% O2 in solid Ar at 77 K, with O2O2 pair vibrations. For the luminescence spectrum of 0.01% O2 in Ar at 4.2 K a Greens function approach is used to describe the position and extent of the experimentally observed side band. In the one defect approach it was found that the F1 u projections have a band edge resonance for an O2 in solid Ar. However the consideration of the same projections due to an O2O2 first nearest neighbour pair in solid Ar gives typical inband contributions.
The Applicability of Diffusion Theory to the Study of Luminescent Emission from a Doped Organic Crystal
Authors: Selsby R. G. 
Published: July 2007

AbstractThe Frisch‐Collins diffusion theory, developed to handle the case of a plurality of competing traps in the diffusion field, is used to calculate the time dependence of the fluorescence both from host crystal and impurity trap in a doped organic solid. Satisfactory agreement is found between experiment and theory indicating that a theory of exciton diffusion can account for the excitation energy transfer in an organic crystal.
Hot Carrier Injection into Molecular Crystals and Its Relevance to the Field Dependence of Photocurrents
Authors: Baessler H. , Killesreiter H. 
Published: July 2007

AbstractExtrinsic photocurrents in anthracene and p‐chloranil crystals resulting from either electron photoemission from a metal contact or sensitized electron injection from excited adsorbed tetracene molecules are investigated. At field strengths, where space charge effects are unimportant, i.e. where currents usually are assumed to be saturated, their field and temperature behaviour can be quantitatively described assuming that both generation processes initially yield hot electrons bound to the positive countercharge by Coulombic attraction. Direct escape, determined by scattering in the Coulombic potential well, is a temperature independent process giving rise to an exponentially field dependent photocurrent component. The scattering mean free path in anthracene is found to be (11 ± 2) Å. Thermalized carriers can either undergo geminate recombination or can overcome the Coulombic potential barrier by thermally activated diffusion.
Comments on Field Emission in Solids: Multiple Particle Tunneling and Singularities
Authors: Ngai K. L. 
Published: July 2007

AbstractIn recent field‐emission experiments a high energy tail in the field‐emitted electron distribution has been observed. It has been described as the products of a cascade process initiated by the injection of hot holes into the conduction band. Another process that can possibly contribute to the tail current is multiple particle tunneling. In the present development we consider the features of this tunneling process. We observe from the data that an infrared divergence‐like behavior occurs in the tail current at the Fermi energy. We argue that one reason for the occurrence of such a divergence is the singular transient response of the Fermi sea to the sudden establishment of a hole potential when an electron near the Fermi energy tunnels.
Indirect Exchange Parameters of Two‐Sublattice Antiferromagnets
Authors: Shimada Y. , Hacker H. 
Published: July 2007

AbstractA technique is described for evaluating the indirect exchange parameter |J(0)| for two‐sublattice antiferromagnets. The method relates the RKKY model, incorporating the freeelectron approximation, to the nearest and next‐nearest neighbor interaction constants of the molecular field model. Application of the technique to DyIn3 yielded values of |J(0)| equal to 0.17 and 0.03 eV for kF/k equal to 0.98 and 0.86, respectively.
Influence du zirconium sur l'interaction quadrupolaire du 181Ta dans l'hafnium métallique
Authors: Baudry A. , Boyer P. 
Published: July 2007

AbstractLa mesure du facteur d'atténuation G2(t) de la corrélation angulaire γ‐γ différentielle sur la cascade 133—482 keV du 181Ta dans un échantillon polycristallin d'hafnium très pur et dans un alliage de ce měme matériau avec du zirconium, permet de mettre en évidence l'influence de celui‐ci sur les écarts souvent observés entre la valeur expérimentale du paramètre d'asymétrie de l'interaction quadrupolaire (η ≈ 0,30) et la valeur η = 0 attendue pour un réseau hexagonal compact.
Optische Anregung des Tochteratoms Sc durch vorhergehenden ß‐Zerfall von 45Ca in festem Xe
Authors: Gerth G. , Luchner K. , Micklitz H. 
Published: July 2007

AbstractRadioaktives 45Ca wurde in eine Xe‐Matrix bei 50 und 4,2 °K eingebaut (Dotierung ca. 1:200). Das hieraus emittierte Licht wurde mit Interferenzfiltern und in Koinzidenz zum Kernzerfall untersucht. Die Photonenausbeute betrug maximal 0,22 ± 0,03 pro β‐Zerfall. Die Lebensdauer der optischen Niveaus wurde mit Hilfe verzögerter β‐Koinzidenz gemessen. Im gesamten untersuchten Spektralbereich (1,1 bis 0,19 μm) wurden drei Banden im nahen UV gefunden; in einer da von zeigen die Flanken verschiedene Lebensdauern. Deutung: Durch die plötzliche Kernladungsänderung beim β‐Zerfall von 45Ca entsteht in ∼ 20% aller Zerfälle das Tochterion Sc+ im angeregten 4s5s 1S0‐Zustand (ΔZ‐Anregung oder ”︁shake up„ Prozeß). Bevor eine optische Emission stattfindet, rekombiniert das angeregte Sc+ durch Ladungsaustausch mit den Xe‐Liganden zu Sc; dabei werden bevorzugt die 3d4s4p 2P (bzw. 2F)‐Zustände (Tiu‐Zustand in der Xe‐Matrix) besetzt (Lebensdauer (9,0 ± 0,5) bzw. (4,6 ± 0,9) ns). Dipolübergange in den aufgespaltenen 3d4s2 2D‐Grundzustand (T2g und Eg Zustand in der Xe‐Matrix) führen zu der Emission der beobachteten Banden. Durch den Einfluß der Xe‐Matrix wird der 3d4s4p 2P → 3d4s2 2D Übergang um (3300 ± 250) cm−1 zu kürzeren Wellenlängen verschoben. Die Aufspaltung des Grundzustandes im Feld der Xe‐Liganden ergibt sich zu (2200 ± 300) cm−1 = 10 Dq.
Valence Band Structure of Tellurium from Shubnikov‐de Haas Experiments
Authors: Braun E. , Neuringer L. J. , Landwehr G. 
Published: July 2007

AbstractMeasurements of Shubnikov‐de Haas (SdH) oscillations in tellurium were carried out on doped, single crystals with hole concentrations of 5.9 × 1016 ≦p0 ≦ 5 × 1018 cm−3. Experiments were performed using static magnetic fields up to 15 T at several temperatures in the liquid helium range. The observed angular dependence of the periods were analysed by a method due to Mueller which yields the shape of the constant energy surfaces independent of assumptions as to the specific analytical form of the E(k)‐function. The dumb‐bell shape of the constant energy surfaces, and the small trigonal warping about the kz‐axis at the highest concentrations which were found are in agreement with the predictions of existing theories about the upper valence band of tellurium. Values are given for terms of higher order than k2 in the E(k)‐function of the upper valence band. Using the temperature and field dependence of the oscillation amplitudes the cyclotron masses and Dingle broadening temperature were determined at various carrier concentrations.
Etude de la structure électronique de de l'antimoniure d'indium de type n par une méthode de battement hyperfréquence
Authors: Ferre D. , Castelain M. , Dubois H. 
Published: July 2007

AbstractDans cet article, nous montrons que, moyennant un choix convenable de la puissance de deux hyperfréquences irradiant un cristal d' InSb n, on peut utiliser le battement qui prend naissance pur étudier la distribution électronique du cristal lorsque la température de celle‐là s'écarte pas trop de celle du réseau cristallin et en conclure à l'existence d'une bande d'impureté complètement séparée de la bande de conduction pour des concentrations inférieures à 1014 cm−3 en champ magnétiquenul. Cette interprétation est confirmée par les études réalisées en fonction du champ magnétique et de la concentration en impuretés.