bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of the Fourier Method for Calculations of the Lattice Distortion Around a Vacancy in Copper and Silver. Pseudopotential Approach
Authors: Chevychelov A. D. 
Published: July 2007

AbstractOn the basis of the physical assumptions formulated in [1] the precise calculation of a lattice distortion around a vacancy in Cu and Ag is performed using the static Fourier method. The obtained result is compared with that of [1] and with the calculations of Bullough and Hardy [9].
Interpretation of the Widths of SEM Electron Channelling Lines
Authors: Schulson E. M. 
Published: July 2007

AbstractFrom a two beam approximation of the dynamical theory of the relative backscattered electron intensity as a function of direction of incidence, it is shown that the angular width of electron channelling lines on SEM images can be given by the expression: 2 ωg = 2/ξg|g|, where ξg and g are the extinction distance and the reciprocal lattice vector respectively of the strongly excited reflection. The expression is verified by comparing calculated line‐widths with measured widths from silicon as a function of incident beam energy and reflection excited. An appendix is given discussing quantitatively the degradation effects of beam divergence on electron channelling lines. It is suggested that line broadening might be a possible method for assessing lattice distortions.
Concentrational Phase Transition in Solid Solutions of Titanium and Chromium Sesquioxides (Cr2–xTixO3)
Authors: Geld P. V. , Zubkov V. G. , Matveenko I. I. 
Published: July 2007

AbstractOn the basis of the results of magnetic susceptibility, neutron scattering, and thermopower investigations it is shown that anomalies in the isotherms of μeff., μz, and in the thermoelectric coefficient of magnetic semiconductors may be explained assuming that a concentrational phase transition takes place. In solid solutions of the type Cr2–xTixO3 this phase transition is accompanied by the conversion of the collinear antiferromagnetic structure into a noncollinear antiferromagnetic one.
Recombination of Impact Ionized Excess Carriers in Tellurium
Authors: Bringer A. , Nimtz G. 
Published: July 2007

AbstractThe recombination time of p‐type tellurium was measured dependent on carrier mobility and carrier density at 77 K. Excess carriers were produced by impact ionization in strong electric fields to achieve large excess carrier concentrations. The recombination of the excess carriers was observed by the help of microwaves, the rise time of the experimental apparatus was less than 5 × 10−9 s. The experimental data can be interpreted as the superposition of a slow and a fast exponential decay. The results can be explained by an extended Shockley‐Read model. The energy level and the concentration of the trapping and recombination centers can be deduced from the experimental data.
Work‐Hardening and Surface Investigations on Copper Single Crystals Oriented for Multiple Glide
Authors: Vorbrugg W. , Goetting H. Ch. , Schwink Ch. 
Published: July 2007

AbstractFor copper single crystals with axis orientations [110], [111], and [100] work‐hardening curves and surface phenomena were studied at various temperatures. Analogous to single glide crystals we succeeded in dividing the curves into different stages and correlating them with characteristic slip line patterns. [110] crystals show the same work‐hardening behaviour as single glide crystals, contrary to [111] and [100] ones where multiple glide is fundamental. The result of a quantitative analysis of the slip line photographs is that apparently for all orientations the same work‐hardening mechanisms are operating. However, in [111] and [100] crystals cross‐slip seems to occur in a way different from that in single glide crystals.
Electron Magnetic Susceptibility, Paramagnetic Resonance, and the Band Structure of Silicon‐Rich n‐Type Silicon–Germanium Alloys
Authors: Geist D. 
Published: July 2007

AbstractThe lattice susceptibility appropriate to the silicon content has been subtracted from the total susceptibility. The remaining carrier contribution is dependent on the effective mass parameters and the g‐value. Using g ≈ 2, extrapolated from measured electron paramagnetic resonance (EPR) values and assuming six ellipsoidal energy surfaces with K = m∥︁/m⟂ = 4.68, the mass m⟂ is found to be about m⟂ = 0.27 m (m free electron mass), a value lying close to that for silicon. This result indicates that the band structure as a whole in the neighbourhood of the Δ1 minimum changes only slightly going from 100% silicon to the range between 80 and 65% silicon in silicon–germanium alloys.
Impurity Absorption in GaP Doped with Copper and Oxygen
Authors: Olsson R. 
Published: July 2007

AbstractOptical absorption due to impurities was investigated in homogeneous GaP crystals at room temperature. The transmission of light through the crystal is influenced by a simultaneous additional illumination of light with different wavelength. This light changes the occupancy of an impurity level. A simple theory is presented, which relates this change in transmission of light to the absorption coefficient due to an impurity and also to the optical cross sections of the impurity level involved. The curves for the transmission change were compared with photocurrent quenching spectra measured on the same sample. The absorption coefficient was measured directly in the range 0.5 to 2.3 eV. The relative change in transmission was large in some samples (up to 10%), but had such a slow relaxation, that steady light had to be used. Absorption edges at 0.64, 0.70, 0.8, and 0.9 eV were found and their origins are discussed. The properties of some of the absorptions were found to be consistent with those expected from an acceptor impurity state with a dn electron configuration.
Interband Exchange and the Excitonic Instability
Authors: Kübler J. 
Published: July 2007

AbstractA calculation of the electronic dielectric function (DF) in semiconductors with small energy gaps is presented that takes into account the screened Coulomb and exchange interaction between electrons and holes. Depending on the sign of the exchange term, the DF is either given approximately by its well‐behaved background value or is strongly enhanced over the RPA result when the gap is decreased to zero. Consequences for the excitonic instability are elaborated.
ESR and ENDOR Investigation of Interstitial Hydrogen Atoms in Alkali Halides. II. Theoretical Interpretation
Authors: Spaeth J. M. , Seidel H. 
Published: July 2007

AbstractA theoretical interpretation of the superhyperfine interactions, the proton hyperfine interaction, and the g‐factor of H centres in KF, KC1, KBr, NaCl, and RbCl is presented. The anisotropic distribution of the hydrogen electron into the lattice is well explained by a wave function which was obtained by orthogonalization of the hydrogen Is function to an internally orthogonal set of crystal ion orbitals. A slight covalency to the nearest halogen neighbours is taken into account. The g‐factor can also be understood on the basis of this wave function, if the electronic as well as the charge transfer excited states are considered. In order to explain the proton hyperfine interaction the influence of van der Waals forces has to be included.
The Temperature, Pressure, and Concentration Coefficients of Resistivity of Metals and Their Relation to the Diffusion Thermopower
Authors: Barnard R. D. 
Published: July 2007

AbstractThe resistivity of metals has been considered in the light of modifications to the Fermi energy, Debye temperature, and band structure brought about by changes of pressure, temperature and impurity concentration. The changes of Fermi energy have been formulated in terms of the diffusion thermopower provided the electron scattering is quasi elastic. A new relation between the temperature coefficients of resistivity at constant pressure and constant volume is established and verified for the alkali metals. The implications of the resistivity corrections to the study of deviations from Matthiessen's rule are also discussed.
Theory of Vibronic Spectra in Molecular Crystals with Four Molecules in the Unit Cell: Perylene
Authors: Witkowski A. , Zgierski M. Z. 
Published: July 2007

AbstractA theory of vibronic coupling in molecular crystals which – like perylene – contain four molecules in the unit cell is presented. The vibronic Hamiltonian, selection rules, and expressions for the integral properties of an absorption spectrum are derived and discussed. The vibronic equation contains parameters which as shown can be obtained from the widths and location of the gravity centres of the vibronic absorption bands. The absorption spectra computed from the vibronic equation derived agree well in both frequency and intensity distribution with the observed crystal absorption bands of different polarization. All main features of the absorption bands in the perylene crystal result from vibronic coupling only and inclusion of charge transfer states is not necessary.
Theory of the Elastic and Inelastic Scattering of Light by Magnetic Crystals. I. First‐Order Processes
Authors: le Gall H. , Jamet J. P. 
Published: July 2007

AbstractA quantum description of the different magneto‐optical interaction is obtained using the second quantization notation in the spin‐dependent dielectric Hamiltonian of the crystal. It is shown that the Faraday, Kerr, Cotton‐Mouton, and spin Raman effects due to paraor ferromagnetic spins, which generally in the literature appear as distinct processes, may be described actually with a common spin–photon interaction Hamiltonian. From this Hamiltonian the magneto‐optical interactions may be separated into two groups corresponding to either an elastic or an inelastic spin‐photon scattering. The physical and analytical relations between these interactions, the general properties of susceptibilities, and polarization rules are deduced from the microscopic concept of the scattering of photons by magnetic crystals. It is shown that the Faraday effect, which is usually investigated from the circular birefringence of a macroscopic field, can be described as an elastic scattering of photons with a π/2 spatial rotation of their polarization vectors.
A New Relaxation Mechanism of the Exchange Bounded Paramagnetic Centres
Authors: Glinchuk M. D. , Deigen M. F. , Suslin L. A. 
Published: July 2007

AbstractThe time of the spin‐lattice relaxation of exchange bound paramagnetic ions due to the modulation of their electric fields by lattice oscillations is calculated. The contribution of the mechanism suggested to the relaxation is essential in crystals where the constants of the electron‐spin coupling are large. As an example the relaxation time of paramagnetic centres in crystals with Td symmetry is evaluated.
Thermal Broadening and Shift of the Zero‐Phonon Lines in Optical Spectra of Impurity Organic Crystals
Authors: Sapozhnikov M. N. 
Published: July 2007

AbstractA theoretical interpretation is made of all the data on the temperature broadening and shift of the zero‐phonon lines in spectra of impurity normal paraffin crystals. It is shown that the broadening of most lines investigated may be well described in the Debye approximation using the theoretical dependence, obtained on the basis of the Krivoglaz‐McCumber model in which adiabatic, Condon and harmonic approximations were utilized, and a small change of the elastic constants of the lattice vibrations and a displacement of the equilibrium positions of nuclei induced by the electron transition in the impurity centre were taken into account. The line shifts could not be described by the theoretical formula obtained in the same approximation. The possible reasons of this discrepancy are discussed.
Neutron Diffraction and Susceptibility Measurements on ErPO4 and ErVO4
Authors: Will G. , Lugscheider W. , Zinn W. , Patscheke E. 
Published: July 2007

AbstractPowder neutron diffraction measurements were performed on ErPO4 and ErVO4 at temperatures as low as 2 K and in external magnetic fields up to 30 kOe. No magnetic ordering could be detected. The ensueing susceptibility measurements and an estimate of the magnetic dipole interactions lead to an transition temperature of about 0.8 K, with the interaction being probably purely dipolar with negligible exchange interaction.
Dielectric Properties of the Rubidium Halide Crystals in the Extreme Ultraviolet up to 30 eV
Authors: Peimann C. J. , Skibowski M. 
Published: July 2007

AbstractThe reflectivity of freshly cleaved single crystals of RbCl, RbBr, and RbI and of an evaporated RbF film was measured at room temperature for photon energies between 10 and 30 eV using synchrotron radiation. With a resolution of 2 Å over the whole spectral range considerable new spectral features were observed in the region where high energy valence band transitions occur and electrons from the first core level, the Rb+ 4p level, are excited. For all Rb halides excitation of the Rb+ 4p level starts at about 16 eV with an exciton multiplet which can be explained as being due to spin‐orbit splitting of the core level and to critical points at Γ and X in the conduction band. The energies of the multiplet are compared to transition energies of the 4p electrons of the free Rb+ ion. The complex dielectric constant, the absorption coefficient, and the energy loss function are derived from the reflectivity by means of a dispersion analysis. The results are compared with absorption and electron energy loss experiments on evaporated polycrystalline films.
Crystal Dynamics of Cesium Iodide
Authors: Bühner W. , Hälg W. 
Published: July 2007

AbstractFrequencies of the normal modes of vibration of cesium iodide at room temperature propagating in certain symmetry directions were determined by means of slow‐neutron inelastic scattering using a triple axis spectrometer. The data are in reasonable agreement with thermal diffuse X‐ray scattering investigations of Eldridge [1]. The shell model was fitted to the frequencies with good results. This 14‐parameter model was used to compute a frequency distribution and related thermodynamic data.
Low temperature specific heats and related thermodynamical functions of neodymium dihydride NdH2.00. crystal field effects
Authors: Biegański Z. 
Published: July 2007

AbstractThe heat capacity of neodymium dihydride NdH2.00 was measured over the low‐temperature range by adiabatic calorimetry. At 298.15 K the measured heat capacity at constant pressure (Cp), the entropy (S0), the enthalpy function (H0–H), and the Gibbs function–[(F0–H)/T] are: 10.29 cal mol−1 deg−1, 14.08 cal mol−1 deg−1, 1882 cal mol−1, and 7.76 cal mol−1 deg−1, respectively. The influence of the crystal field of cubic symmetry on the splitting of the ground level 4I9/2 of the Nd3+ ion was analysed, and the conclusion was drawn that the quartet Γ is the lowest‐lying level. This supports the idea of the anion‐like character (hydridic model) of hydrogen in this hydride.
Paramagnetic resonance of Yb3+ and Nd3+ in YPO4
Authors: Hillmer W. 
Published: July 2007

AbstractParamagnetic resonance of trivalent ytterbium and neodymium in single crystals of yttrium phosophate has been investigate at K‐band frequencies and temperatures of 1.7 and 4.2 K. Spin‐Hamiltonian parameters including the hyperfine constants for Yb171 and Yb173 and the ground state eigenfunctions were determined.
Optical properties of boron carbide and comparison with β‐rhombohedral boron
Authors: Werheit H. , Binnenbruck H. , Hausen A. 
Published: July 2007

AbstractThe optical absorption spectrum of B12C3 exhibits an indirect interband transition with onset at h ω = (0.48±0.03) eV. In the subsequent region of lower absorption (α ∼ 400 cm−1) traps of great density are essentially effective for the optical properties. The lattice vibration spectrum starting at 4 μm has oscillations at 6.55, 9.25, 10.5, 11.9, 14.4, 17.3, and 25.4 μm. A monotonic increase of the reflectivity occurring at wavelengths λ > 30 μm can be assigned to the strongly damped plasma resonance of free holes. The comparison with the properties of β‐rhombohedral boron indicates distinct similarities.
On the temperature factors of tetragonal and Cubic BaTiO3
Authors: Aberdam D. 
Published: July 2007

AbstractA calculation is made of the temperature factors of tetragonal and cubic BaTiO3 at room temperature and in the range between 395 and 925°K. This calculation is based on the recently available data on the phonon dispersion spectrum of BaTiO3. The deviation from the Debye model for the acoustical modes contribution, high‐frequency optical modes contribution, and the dispersion anisotropy of the low‐frequency transverse optical modes are taken into account. Our results are in reasonable agreement with the data obtained from neutron structure analysis for the titanium and the barium ions, and support Hüller's model of the dispersion anisotropy of the soft modes.
Analysis of point defect states in copper. IV. Interstitial cluster formation at 93 K
Authors: Becker D. E. , Dworschak F. , Wollenberger H. 
Published: July 2007

AbstractDamage rate measurements have been performed by irradiating copper samples of different purity with electrons at 93 K up to defect concentrations of about 10−4. The results are interpreted in terms of interstitial cluster formation. The clusters are nucleated at impurities.
A theoretical calculation of the orbital g‐factor of the excited state of F‐centres in alkali halides
Authors: Thuau M. , Margerie J. 
Published: July 2007

AbstractUsing a model similar to that of Smith [4] the orbital g‐factor gorb. of the excited state of F‐centres in LiF, LiCl, NaF, NaCl, KF, and KCl was calculated. The results are quite sensitive to the particular envelope wavefunction chosen for the F‐centre. Gourary and Adrian type II wavefunctions lead to results which are in good agreement with the available experimental values.
Comments on the theory of photoionization of transition metal impurities in semiconductors
Authors: Langer J. M. 
Published: July 2007

AbstractThe shape of photoionization spectrum connected with removal of an electron from the 3dn shell of a transition metal impurity into the conduction band has been calculated. The influence of configurational mixing between 4pn and 3dn states on the shape of the spectrum is discussed. The absorption coefficient for uniaxial crystals (α for E ‖ c and E ⊥ c, c crystal axis) is given.
Pressure effects on zero‐field resonance. II. Gd3+ in various zircon structure compounds
Authors: Nowicki P. , Hillmer W. , Urban W. 
Published: July 2007

AbstractA systematic investigation of the influence of hydrostatic pressure on the zero‐field resonance of trivalent gadolinium has been made in a set of nine isomorphic crystals. The pressure coefficients of the rotational symmetric crystal field parameters (which are reliably determined by our experiment) do not only vary markedly in the absolute value with the compounds but also change sign.
Generalized phase shifts for a cluster of muffin‐tin potentials
Authors: John W. , Ziesche P. 
Published: July 2007

AbstractStarting with the partial wave method generalized to non‐spherically symmetric potentials by Demkov and Rudakov a purely algebraic scheme is proposed how to calculate the generalized phase shifts for a cluster of non‐overlapping muffin‐tin potentials. These cluster phase shifts and the corresponding partial wave amplitudes are determined by a system of homogeneous linear equations, into which the phase shifts of each muffin‐tin potential and the structure enter separately, completely similar to the KKR method for the band structure of a crystal. By the proposed scheme bound states can also be calculated, the number of which is limited by the properties of cluster phase shifts. As a mathematical remedy an addition theorem about the spherical Neumann functions is derived.
Effect of Ni2+ on the EPR of Mn2+ Ions doped in single crystals of nickel salts
Authors: Janakiraman R. , Upreti G. C. 
Published: July 2007

AbstractElectron paramagnetic resonance of Mn2+ has been studied in single crystals of magnesium sulfate heptahydrate (MgSO4 · 7 H2O) at 300°K. Mn2+ was found to substitute for Mg2+ and exhibit four inequivalent magnetic complexes corresponding to the tetramolecular unit cell of MgSO4 · 7 H2O. The results are compared with those for Mn2+ in isostructural NiSO4 · 7 H2O. The observed differences in the EPR of Mn2+ in crystals of the two salts are attributed to the magnetic interaction of Ni2+ and Mn2+.
Cyelotron absorption in germanium and silicon in crossed fields
Authors: Akopyan R. M. 
Published: July 2007

AbstractThis paper deals with the observability of the cyclotron resonance spectrum changes in Ge and Si in crossed magnetic and weak electric fields. It is shown that the displacement of the fundamental line in the electric field is of the same order of magnitude as the estimates made in [9] and the observability of the second harmonics is within the limits of experimental possibilities.
Energy band structure of vanadium, zirconium, and niobium monocarbides
Authors: Potorocha V. I. , Tskhai V. A. , Geld E. V. 
Published: July 2007

AbstractThe results of calculations of the electron energy spectrum and the contribution of atomic states to the formation of band structure of vanadium, niobium, and zirconium monocarbides based on the tight‐binding method arc reported. The calculations were performed in two‐centre approximation, taking into account the ns and (n – 1) d‐orbitals of metal atoms and 2s, 2p carbon atoms. The secular equation was solved in 214 points, 1/48th of the Brillouin zone. A discussion of results and their comparison with experimental data are presented.
Transient photocurrents induced by time‐dependent diffusion of excitons to the surface of anthracene and p‐chloranil single crystals
Authors: Killesreiter H. , Braun R. 
Published: July 2007

AbstractTransient photocurrents produced by a light flash were used as a probe for the time‐dependent diffusion of excitons in anthracene and p‐chloranil single crystals. An analytical solution for the time‐dependent diffusion equation for excitons near a quenching phase boundary is presented. Inserting experimental data allows evaluation of the lifetime, τ = 4×10−6s, the diffusion coefficient, D = 5×10−6 cm2/s, and hence the diffusion length, L = 5×10−6 cm, for n‐π* triplet excitons diffusing perpendicular to (ab) planes in p‐chloranil. For triplet excitons in anthracene, the diffusion coefficient normal to (ab) plane, D ≈ 5 × 10−5 cm2/s, is estimated. The method allows to distinguish between different sorts of excitons diffusing in a crystal with different velocities. This is of importance for anthracene, where both singlet and triplet excitons are produced by strongly absorbed light.
Study of lH in paraelectric and ferroelectric K4Fe(CN)6 · 3 H2O by pulsed NMR
Authors: Avogadro A. , Cavelius E. , Müller D. , Petersson J. 
Published: July 2007

AbstractThe nuclear spin lattice relaxation time T1 of 1H in a K4Fe(CN)6 · 3 H2O single crystal was measured between room temperature and 70 °C by a 90°‐t‐90° sequence. At 15 and 8.48 MHz T1 is influenced by a translational diffusion of the water molecules and by a flip motion around the bisectrix of the water molecules. T1 has a discontinuity at the Curie point. In addition a dependence of T1 on the orientation of the crystal is observed and the absorption line shape is investigated. The results arc interpreted assuming that the intramolecular interactions of the protons of the water molecules give the main contribution to the spin lattice relaxation.
Excitation‐diffusion‐limited energy transfer in solids I. Theory of the dynamics
Authors: Heber J. 
Published: July 2007

AbstractThe dynamics of emcrgy transfer processes in solids are treated theoratically under the following assumptions: 1. All microscopic processes involved are incoherent. 2. The corresponding interactions are short. ranged. 3. The diffusion of the excited states in the system of the donors is the process limiting the energy transfer. The fluorescence decays of the donors and acceptors after a δ‐shaped excitation arc given, and discussed as a function of the two parameters of the theoretical model.