bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charge Compensation by O2− Vacancies in Cr3+‐Doped SrTiO3
Authors: Meierling H. D. 
Published: July 2007

AbstractESR measurements of Cr3+ ions in SrTiO3 at orthorhombic lattice sites in the cubic phase of the crystal are described. The orthorhombic distortion is caused by an oxygen vacancy in the neighbourhood of the Cr3+ ion. A model of the displacement of the neighbouring oxygen ions is proposed. The values of the constants of the spin‐Hamiltonian are given.
The F Center in KCl Crystals Part II: Optical Properties and Analogy with the H Molecule
Authors: Aegerter M. A. , Lüty F. 
Published: July 2007

AbstractF centers in KCl crystals were so far identified by one absorption band at 1.4 μm. Several new absorption bands found in the visible and near UV are studied at LHeT with an almost perfectly aligned system. Energy positions, dichroic behavior and oscillator strengths of these transitions are found in close agreement to the calculated states of the H molecule corrected with a single dielectric constant. Excitation of the lowest excited 2pσu state at 1.4 μm leads with a temperature independent quantum efficiency to the IR emission at 1.67 μm. The experimental band shapes of these IR transitions with their associated zero phonon line were analyzed using a simple model for the electron coupling. Low temperature excitation of all higher absorption states (2pπu, etc.) produces a 600 nm luminescence. At higher temperature a thermally activated process transfers the excitation energy to the lowest excited state (2pσu) quenching the 600 nm luminescence and producing the IR emission.
Energy Bands of Potassium Halides (Green's Function Method)
Authors: Overhof H. 
Published: July 2007

AbstractThe energy bands of KCl, KBr, and KI have been calculated using the relativistic Green's function (KKR) method. Besides the results of calculations with atomic potentials for KCl, KBr, and KI results for KI from ionic potentials with Kohn‐Sham and Slater exchange potentials are also compared. Special care is taken to interpret the excitonic structure of KI in terms of band separations. For this purpose extreme ultraviolet data are used to confirm the interpretation.
Optical Absorption Intensities of Ho3+ in YPO4
Authors: Becker P.‐J. 
Published: July 2007

AbstractThe intensities of the electric dipole transitions within the 4f10 configuration of Ho3+ in YPO4 have been measured. They can be described with the Judd‐Ofelt theory. The fitted parameters show that the configuration 4f10 interacts stronger with the configurations nd94f11 (n = 3, 4) than with the configurations 4f9nd (n ≥ 5). The total interactions with g‐electrons and with d‐electrons are of the same order.
Electron Microscope Image Contrast from Dislocation Loops
Authors: Bullough R. , Maher D. M. , Perrin R. C. 
Published: July 2007

AbstractExperimental electron microscope images of dislocation loops in molybdenum have been compared to theoretical loop images displayed in the form of computer simulated micrographs. The exact displacement field around a circular edge dislocation loop has been calculated using isotropic elasticity theory; this displacement field together with the two‐beam dynamical theory of electron diffraction contrast have been used to compute image intensities. Specific results are given for loops of radius ≈ 250 Å and ≈ 25 Å. Their contrast has been studied over a narrow range of the numerous variables which are known to influence image features. It has been found that the general topographical character of certain prominent experimental images is qualitatively accounted for by the simple “elastic” defect model with the two‐beam theory of electron diffraction.
The Structure of the Indirect Absorption Edge of CdO
Authors: Kocka J. , Konak C. 
Published: July 2007

AbstractThe optical absorption in CdO single crystals is reported for photon energies just below the absorption edge (≈ 2.4 eV) at several temperatures between 80 and 300 °K. The investigation of the shape of the intrinsic absorption indicates the existence of an indirect gap. The influence of the higher concentration of conduction electrons on the indirect absorption edge of CdO has been studied. Extrapolation for n = 0 leads to the value Eig = (1.09 ± 0.04) eV.
Observation of dislocation arrays in low angle tilt boundaries in gold
Authors: Schober T. , Balluffi R. W. 
Published: July 2007

AbstractTechniques were developed for studying the structure of low angle tilt boundaries by transmission electron microscopy. Boundaries were observed: 1) at normal incidence in bicrystals prepared by welding single crystal films together face‐to‐face at predetermined misorientations, 2) edge‐on in polycrystals obtained by the annealing of welded thin‐film bicrystals initially containing only twist boundaries. Symmetric (100) boundaries with [001] tilt axes consisted of either: a) arrays of uniformly spaced single edge dislocations running parallel to [001] with Burgers vectors b = a [100]; or b) arrays of uniformly spaced close pairs of dislocations running parallel to [001] with the dislocations in each pair having b = a/2 [110] and b = a/2 [110]. A choice between possibilities a) and b) could not be made on the basis of either the experimental observations or simple energy considerations. Symmetric (110) boundaries with [001] tilt axes consisted, as expected, of arrays of single edge dislocations parallel to [001] with b = a/2 [110]. Dislocation structures in (100) and (110) boundaries which possessed particularly small tilt angles and tilt axes lying along directions other than [001] in the boundary plane were also studied. In many cases, when the tilt axes were in certain favorable ranges of orientation, the dislocations broke up into segments in the boundary planes along directions which allowed them to dissociate on {111} planes into partial dislocations and stacking fault ribbons.
Influence of hydrostatic pressure on the electrical conductivity of tellurium single crystals
Authors: Becker W. , Fuhs W. , Stuke J. 
Published: July 2007

AbstractThe influence of hydrostatic pressure up to 5000 kp/cm2 on the electrical conductivity of differently doped tellurium single crystals is investigated in the temperature range from 165 to 430 °K. For extrinsic and intrinsic tellurium the conductivity increases exponentially with pressure. The pressure coefficient π = d (In σ)/dp is independent of temperature in the extrinsic region, rises appreciably then and finally decreases proportional to 1/T in the intrinsic range. The decrease of the energy gap with pressure at a rate of dEg/dp = −1.3 × 10−5 eV cm2/kp is the major effect in the intrinsic region. Possible mechanisms for the pressure dependence in extrinsic tellurium are discussed. It is shown that a decrease of the effective mass with pressure cannot account for the experimental results and that probably an enhancement of the dielectric constant by pressure leads to the observed increase of the mobility.
Optical properties of transition metal impurities in CdSe. I. Crystal‐field spectra
Authors: Langer J. M. , Baranowski J. M. 
Published: July 2007

AbstractThe absorption spectra of Ti (d2), V (d3), Cr (d4), Fe (d6), Co (d7), Ni (d8), and Cu (d9) in CdSe crystals are presented. The main features of the spectra are successfully interpreted using crystal‐field theory for the states of 3dn configuration in a potential of predominantly Td symmetry. It is found that the oscillator strengths of the observed absorption bands are in the range 10−2to 10−5 due to transitions within the 3dn shell. The crystal‐field parameters, Δ, and the Racah parameters, B and C, are determined where possible, and discussed.
Mössbauer effect studies of 9.3 keV transition in solid krypton
Authors: Mahesh K. , Sharma N. D. 
Published: July 2007

AbstractCubic structure calculations for the temperature dependence study of the recoilless fraction and the Mössbauer energy shift of Kr83m−9,3 keV transition are made using the quasiharmonic rigid‐atom model of the Kr‐lattice vibrations which includes the fourth nearest neighbour central force interactions. The results are compared with the experiment and the Debye model of the phonon spectra. The possibility of the low frequency Kr‐spectra not being Debye‐like is considered and the effect of the lattice anharmonicity is negligible. The characteristic temperature θM (0 °K) of the solid Kr is found to be 25 °K which is in agreement with the experiments.
The temperature dependence of the optical nonlinear susceptibility of sodium nitrite
Authors: Vogt H. , Happ H. 
Published: July 2007

AbstractInformation about the order‐disorder transition of NaNO2 is obtained from the temperature dependence of the optical nonlinear susceptibility χ(2). The decrease of χ(2)(T) in the ferroelectric phase can be related to increasing rotational motion of the NO‐ions. While χ(2) indicates the degree of order within the NO‐sublattice, the spontaneous polarization Ps may be regarded as an order parameter of the Na+‐sublattice. The difference between Ps(T) and χ(2)(T) is explained by a different order‐disorder behaviour of the Na+‐and the NO‐ions.
Optical and transport properties of the magnetic semiconductor α‐RuCl3
Authors: Binotto L. , Pollini I. , Spinolo G. 
Published: July 2007

AbstractThe optical and transport properties in the paramagnetic phase of α‐RuCl3 are studied here for the first time. Values are reported for the dc conductivity of single crystals over the temperature range 110 to 500 °K in the two crystallographic directions, along and perpendicular to the optic c‐axis: at 300 °K, ϱ∥c = 8 × 106 Ωcm and ϱ⟂c = 1.7 × 103 Ωcm. The activation energy for both directions is ≈ 0.1 eV below 300 °K and ≈ 0.5 eV for temperatures above 400 °K. Detailed absorption spectra in the energy range 0.1 to 4 eV, and in the temperature interval 80 to 300 °K, reveal three weak bands (α ≈ 103 cm−1) at ≈ 0.28, 0.53, and 0.75 eV, two stronger peaks (α ≈ 104 to 105 cm−1) at ≈ 1.18, 2.08 and a step at 3.10 eV (values at 80 °K). Reflectivity measurements in the energy range 1 to 9 eV show maxima which, at 300°K, are centred at ≈ 1.1, 1.9, and 3.10 eV and a marked reflection peak, at ≈ 5.10 eV, probably related to p(Cl) → s(Ru) band‐to‐band transitions. Ac photoconductivity spectra in the 0.6 to 2.8 eV region show structures closely related to the absorption bands in the same energy range. The different temperature dependence of the absorption and photocurrent spectra over the 80 to 300 °K interval is discussed. After an analysis of the transport data, the absorption spectrum up to 3 eV is discussed in terms of the Tanabe and Sugano diagram for a d5 configuration.
On the deformation potential constant of the conduction band in InSb
Authors: Tsidilkovskii I. M. , Demchuk K. M. 
Published: July 2007

AbstractAn analysis of experimental data for InSb is made and the deformation potential constant ϵ1 of the conduction band is determined. It is shown that the correctly calculated value of |ϵ1| is about 30 eV. In the calculations of the carrier mobility for heavily doped semiconductors it is essential to take into account the effect of the band nonparabolicity on the transition probabilities and the screening of the scattering potentials by conduction electrons, and additionally at high temperatures it is necessary to consider the influence of electronphonon interaction on the effective mass and energy gap. The small values of |ϵ1| reported by some authors, who studied transport phenomena at low temperatures, are obtained under the condition ħ/τ > kBT (τ is the time between successive collisions), i.e. when the theory used is invalid.
Dichroïsme circulaire magnétique de l'ion Eu2+ dans CaF2 et KCl (bandes larges)
Authors: Ferré J. , Billardon M. , Briat B. 
Published: July 2007

AbstractNous avons mesuré le dichroïsme circulaire magnétique de Eu2+ dans KCl et CaF2, à travers les bandes larges, dans le domaine spectral visible et proche ultra‐violet. Ces expériences ont permis de résoudre les deux bandes principales en leurs composantes spinorbite. Pour chaque bande, le niveau J = 5/2 a l'énergie la plus faible. Ce résultat est en accord avec certains travaux antérieurs.
The convergence of the orthogonalized plane wave method
Authors: Reser B. I. , Dyakin V. V. , Shirokovskii V. P. 
Published: July 2007

AbstractThe convergence of the OPW method is investigated systematically. An analytical estimate is given which shows that the convergence of the OPW method is rather weak. Numerical calculations of the energy band structure of diamond are done using a great number of OPW's (up to 900). The results show that even in this case a stabilization of the energy eigenvalues does not occur.
Temperature‐modulated reflectance of GaSe at the ground state exciton line
Authors: Balzarotti A. , Grandolfo M. , Somma F. , Vecchia P. 
Published: July 2007

AbstractThermoreflectance spectra in the exciton region were obtained on the layer compound GaSe. The experimental results can be explained by assuming that the only temperature effect is a shift of the whole structure. At liquid nitrogen temperature the values Eo = 2.093 eV and T = 41.0 meV are found for the first energy level and the broadening parameter, respectively. Measurements at three different temperatures gave the value dE0/dT = −5.49 × 10−4 eV/deg for the temperature coefficient.
Investigations of central crystal field effects on Ce3+ spectroscopic properties
Authors: Briffaut J. P. 
Published: July 2007

AbstractThe parametric central field has been applied to interpret successfully the changes of the 4f–5d energy gap of the Ce3+ ion in vacuum and in a ligand field. In addition, this model accounts for the stability of related 4f integrals with variations in the 4f–5d energy gap.
Fine structure of the extreme ultraviolet spectra of the potassium halide crystals at 10 °K
Authors: Blechschmidt D. , Haensel R. , Koch E. E. , Nielsen U. , Skibowski M. 
Published: July 2007

AbstractThe reflection spectra of KCl, KBr, and KI single crystals and of a KF film have been measured below 10 °K for photon energies between 10 and 30 eV using synchrotron radiation. The numerous new spectral features at low temperature are discussed in terms of electronic transitions from the valence band and from the K+3p level. Due to spin‐orbit interaction of the K+3p level the Γ‐K+3p core exciton at about 20 eV is split into two lines with an energy separation of about 0.2 eV for all halides. The observed fine structure and a comparison with a calculated conduction band density of states in the case of KI support the excitonic nature of the Γ‐X K+3p doublet.
Overlap and covalent contributions to the crystal field splittings in CaF2:Tm2+
Authors: Anisimov F. , Dagys R. 
Published: July 2007

AbstractThe crystal field splittings in CaF2:Tm2+ were calculated within the framework of the complex (TmF8)6−. By separating the overlap from covalent contributions, the overlap effects were found to dominate. It is shown that ligand‐ligand overlap effects are important. On the contrary, the role of 5s2 5p6 ligand overlap is fairly small. Satisfactory agreement between the values of the splittings calculated and the observed ones is obtained.
Multi‐photon interband optical transitions in crystals
Authors: Kovabskii V. A. , Perlin E. Yu. 
Published: July 2007

AbstractA method is developed to derive expressions for n‐photon interband transition rates with arbitrary n, in which the real crystal energy spectrum, is taken into account. For particular cases the results of the theory under consideration coincide both with the perturbation theory and semiclassical treatment [13 to 16]. The effect of the radiation coherent properties on the multi‐photon processes is discussed. Contrary to previous calculations it is possible to give a qualitative explanation of the experimental data [4, 6].
Singlet exciton annihilation in anthracene crystals
Authors: Babenko S. D. , Benderskii V. A. , Goldanskii V. I. , Lavrushko A. G. , Tychinskii V. P. 
Published: July 2007

AbstractThe fluorescence quenching under high excitation intensities has been studied in anthracene crystals. The singlet–singlet annihilation constant of (1 ± 0.5) × 10−8 cm3 s−1 is calculated from the quenching of fluorescence induced by a nitrogen 16 ns pulse laser (λ = 3371 Å). The main process of quenching under longer illumination (2 × 10−5s) is the interection between singlet and triplet excitons with a rate constant of (7 ± 4) × 10−9 cm3s−1.
Hole mobility in trigonal SexTe1−x single crystals
Authors: Mell H. , Stuke J. 
Published: July 2007

AbstractThe weak‐field magnetoconductivity components σ1111, σ1122, and σ1133 of trigonal Se‐Te mixed crystals have been measured in the temperature range 80 to 300 K. An analysis of these data yields the hole mobility in the alloys. The temperature dependence of the mobility and the comparison with theoretical mobility values indicate that alloy disorder scattering plays an important role in the SeTe system. From the strength of alloy scattering an approximate value of 0.2 eV is obtained for the difference between the valence band energies of Se and Te.
Conduction band of IVa and Va subgroup transition metal monocarbides (II)
Authors: Borukhovich A. S. , Geld P. V. , Tskhai V. A. , Dubrovskaya L. B. , Matveenko I. I. 
Published: July 2007

AbstractResults are presented of a study of the Hall effect (in the low‐temperature range 20 to 300 °K) and of the thermopower of the monocarbides VCx, NbCx, and TaCx within the limits of their homogeneity regions. Basing on the experimental results obtained and on earlier data on magnetic susceptibility and electric resistivity, the electronic spectrum of non‐stoichiometric monocarbides is discussed on the basis of presentations suggested in a previous paper [1].
Mössbauer study of the valence state of 57Fe after 57Co decay in CoFe2O4
Authors: Cruset A. , Friedt J. M. 
Published: July 2007

AbstractThe Mössbauer emission spectrum of 57Co in CoFe2O4 is reported. Electron capture leads to the formation of 57Fe3+ substituting 57Co2+. The stabilization of the aliovalent charge state is consistent with an electrostatic model.
Electron paramagnetic resonance study of Al2+ in BeO
Authors: Du Varney R. C. , Garrison A. K. , Harem S. B. 
Published: July 2007

AbstractWhen single crystal BeO is X‐irradiated at room temperature, paramagnetic centers are formed. These centers are identified by EPR as electrons trapped at Al3+ impurities substitutional for beryllium ions. The g‐tensor is cylindrically symmetric with values g∥ = 2.003 and g⊥ = 2.004 with the axis of symmetry along an Al–O bond direction. The hyperfine tensor has the principal values Ax′x′ = 207.6 G, Ay′y′ = 175.7 G, and Az′z′ = 176.6 G. The x′‐ and z′‐directions lie in a plane which contains the polar or c‐axis and the Al–O bond direction. The z′‐axis makes an angle of 14° with the c‐axis. Also, an absorption spectrum in γ‐irradiated Thermalox 995, a commercial form of sintered BeO ceramic used in thermally stimulated exoelectron emission radiation dosimeters, is analyzed and shown to be the powder pattern of this aluminum impurity center.
X‐ray dilatometric study on ferroelectric phase transition of KH2PO4 I. The order of transition
Authors: Kobayashi J. , Uesu Y. , Enomoto Y. 
Published: July 2007

AbstractX‐ray dilatometric measurements have been made on lattice strains along the A‐ and B‐axes of KH2PO4 as a function of temperature and biasing electric field near the Curie point. It has been clearly observed that the forced ferroelectric transitions take place in a very small but definite temperature range of 0.65 deg. A phenomenological treatment has been developed, and the coefficients of the elastic Gibbs function of KH2PO4 have been successfully determined to γ = −1.19 × 10−10 e.s.u. and Δ = 1.10 × 10−18 e.s.u., where γ stands for the coefficient of the P4 term and Δ for that the of P6 term. γ is negative. These values explain well the reported spontaneous polarization and dielectric stiffness when strong tendency to coexistence of two phases at the transition is duly allowed for. From the observations it is concluded that the ferroelectric phase transition of KH2PO4 is unequivocally of first order.
A model calculation for the energy bands in the Hg1−xCdxTe mixed crystal system
Authors: Overhof H. 
Published: July 2007

AbstractA KKR model is used to calculate energy bands in the Hg1−xCdxTe mixed crystal system near the fundamental band gap. The results are presented in terms of k · p bands according to Kane and compared to experimental k · p parameters for the conduction band. For the heavy hole bands constant energy contours are given in the (100), (110), and (111) planes.
Electroreflectance Spectra and Energy Band Structure of CdSnP2
Authors: Kavaliauskas J. , Karavaev G. F. , Leonov E. I. , Orlov V. M. , Chaldyshev V. A. , Šileika A. 
Published: July 2007

AbstractThe electroreflectance spectra of CdSnP2 chalcopyrite single crystals have been investigated in the spectral region 1.0 to 4.7 eV at room temperature using polarized light. The electroreflectance structure in the region of the fundamental absorption edge and its polarization dependence are found to be in good agreement with the relative location of the valence bands earlier predicted theoretically. A great number of electroreflectance peaks has been observed in the spectral region 2.4 to 4.7 eV and interpreted by optical transitions at the T, T, and N points of the Brillouin zone of the chalcopyrite lattice. The only transitions used were direct ones and responsible for the main structure in the optical spectra of sphalerite crystals. In addition, the fine structure of these optical transitions due to crystal field splitting has been included.
Berechnung der chemischen Verschiebung der Kernresonanz in AIII–BV‐Halbleitern
Authors: Hübner K. 
Published: July 2007

AbstractDie Ramseysche Theorie der chemischen Verschiebung der Kernresonanz wird auf den Fall, daß Energiebänder vorliegen, ausgedehnt und unter Benutzung des Kaneschen Bandstrukturmodells und der Kenntnisse über die chemische Bindung auf die Berechnung der Resonanzverschiebung in AIII–BV‐Halbleitern angewendet. Eine Erklärung der aus der Literatur bekannten experimentellen Verschiebungen wird erst durch Berücksichtigung von d‐Elektronen möglich. Die auftretenden Einzentrumintegrale werden mit Hilfe modifizierter Slater‐Funktionen, die Zweizentrenintegrale mit normalen Slater‐Funktionen berechnet.
A Spin‐Flip Effect in FeSn
Authors: Ligenza S. 
Published: July 2007

AbstractA combined investigation is made of Müssbauer effect and neutron diffraction on powdered samples of FeSn in the temperature range between 4.2 and 400 °K. A spin‐flip effect is found at about 70 °K. Two non‐collinear models of spin ordering are proposed, one above and one below the transition temperature. The magnetic unit cell with a × 2 a ×× 2 c is found at both sides of this transition. It is concluded that the main spin direction at T < 70 °K is along [100] and at 70 °K ≪ T < TN along [210]. The atomic magnetic moment of Fe is obtained to (1.78 ± 0.06) μB at liquid helium temperature.
Local Excitons and Exciton Band Structure in Naphthalene
Authors: Ostapenko N. I. , Sugakov V. I. , Shpak M. T. 
Published: July 2007

AbstractPositions of the electron levels of the local exciton energy in a naphthalene crystal doped with thionaphthene, indole, and benzofurane are calculated. The guest molecule is assumed to change the excitation energy of one host molecule nearest to the impurity. Also it is considered that the main contribution to the exciton dispersion law comes from the matrix elements of resonance interaction between nearest naphthalene molecules which are in inequivalent positions in the ab plane of the crystal. Good agreement between the theoretical and experimental values favours the validity of the chosen local centre model and exciton dispersion law employed.