bluuebunny/crossref_metadata_2025 huggingface dataset:
A theory of the heat of transport of ionic solids using a linear chain model
Authors: Boswarva I. M. , Tan P. L.
Published: July 2007

Both the transition state theory and the kinetic theory for thermal diffusion fail to explain simultaneously the magnitude and the temperature dependence of the heat of transport. The linear chain model, developed in this paper, removes the limitations of the other two theories and it is successful in explaining the experimental data for the silver halides.
Intrinsic localized surface states in GaAs
Authors: Ball G. , Morgan D. J.
Published: July 2007

Surface states at the cleavage plane of GaAs with energy in the band gap of the bulk band structure and with wave vector corresponding to the point γ at the centre of the [110] surface Brillouin zone are calculated using the empirical pseudopotential method, K · p theory, and the method of matching wavefunctions. The results differ markedly from those previously reported for GaAs in that, when the matching plane is situated midway between two atomic layers, not one but two localized surface states are found. When the matching plane is displaced from the central position, however, one of these localized states disappears from the band gap.
Conversion and equilibrium between F‐ and F2‐centers in X‐irradiated KCl. II. Dynamic equilibrium experiments
Authors: Seager C. H. , Welch D. O. , Royce B. S. H.
Published: July 2007

The temperature dependence of the dynamic equilibrium between F‐ and F2,‐centers has been studied in KCl during X‐irradiation. Three distinct regions have been identified, a high temperature region corresponding in its temperature dependence of the equilibrium constant to the corresponding temperature range in additively colored crystals and two low temperature regions in which the equilibrium constant increases with increasing temperature with an apparent activation energy of 0.25 and 0.85 eV. A kinetic model is developed to explain these observations which involves the random creation of point defects by the radiation together with an enhanced creation probability near existing F‐centers.
Localized electron states in a strong magnetic field
Authors: Suprapto B. B. , Das A. K.
Published: July 2007

A non‐variational method to study localized electron states in a strong magnetic field is presented. An example of detailed calculations is given for a specific type of potential.
The crystal field at Er3+ in copper doped zinc selenide
Authors: Lowther J. E.
Published: July 2007

An empirical LCAO‐MO calculation of the magnitude of the overlap contribution to the crystal field at Er3+ at an interstitial site in copper doped ZnSe is reported. The success of the point charge electrostatic model in calculating the magnitude of the crystal field at such sites is discussed.
Selbstdiffusion und isotopieeffekt in silbereinkristallen
Authors: Reimers P. , Bartdorff D.
Published: July 2007

Zwischen 673 und 954 °C wurde die gleichzeitige Diffusion von 105Ag und 110Ag in Silbereinkristallen gemessen. Die Diffusionskoeffizienten D110 sind in guter Übereinstimmung mit den kürzlich von Rothmanet el. Al. [5] mitgeteilten Werten. Der Isotopieeffekt E fällt von 0,72 bei 673 °C auf 0,58 bei 954 °C. Auch diese Daten sind mit den von Rothman et al. gemessenen Ergebnissen gut vereinbar. Die Temperaturabhängigkeit von D und E läßt sich nach Mehrer und Seeger [6] durch Diffusion über Einfach‐ und Doppelleerstellen deuten.
Radiative lifetimes of excited M and R centers in alkali halides
Authors: Bosi L. , Bussolati C. , Cova S.
Published: July 2007

New experimental results are given for the transition energies and for the radiative lifetimes of M and R centers in alkali halides. The experimental values of the absorption energies and of the radiative lifetime are then compared to theoretical values, calculated on the basis of a simple hydrogen‐like model.
A phenomenological theory of dielectric and mechanical properties of improper ferroelectric crystals
Authors: Kobayashi J. , Enomoto Y. , Sato Y.
Published: July 2007

A phenomenological theory has been developed for explaining the anomalous dielectric and electro‐mechanical properties of some improper ferroelectrics. An ordering parameter 8, which plays the role of a trigger for the onset of the spontaneous polarization P is introduced into the thermodynamical potential function. The peculiar dielectric properties of (NH4)2SO4‐ and Gd2(MoO4)3‐group crystals and the anomalous behaviour of the lattice strains of Fe‐I‐boracite can be well explained on the basis of this theory. A graphical investigation in a proper θ–P plane shows how the strength of the coupling between 8 and P characterizes the transition mechanisms of the improper ferroelectrics. As a result, it has become clear that the common origin of the peculiar physical properties of both crystal groups lies in the extreme weakness of the couplings. Experimental methods to disclose improper ferroelectric mechanisms are discussed.
Wavelength modulation of the photoresponse near the indirect edges of Si, Ge, and GaP
Authors: Nishino T. , Hamakawa Y.
Published: July 2007

The wavelength modulation spectra for photovoltage und photoconductivity have been measured near the indirect edges of Si, Ge, and Gap. These measurements show that the structures associated with phonons can be easily resolved by a simple method. The structures corresponding to indirect transitions with emission or absorption of phonons have been observed, and the energies of some types of phonons have been estimated.
Low temperature specific heat of Fe65(Ni1 − xMnx)35 alloys
Authors: Kawarazaki S. , Shiga M. , Nakamura Y.
Published: July 2007

Low temperature specific heat measurements were carried out for f.c.c. Fe65(Ni1 − xMnx)35 ternary alloys which cover the electron concentration range from 7.65 to 8.70. The electronic specific heat coefficient γ has a large peak against the mean electron concentration e/a around 8.5 and its peak value is 6.5 × 10−3 cal/mol deg2. On the basis of the itinerant electron ferromagnetism this large γ‐value can be explained as purely electronic origin taking the change of exchange splitting of spin up and spin down bands into consideration, and the increase in γ in the Invar region has been shown to play an important role in the sharp deviation of the average magnetic moment from the Slater‐Pauling curve. An enhancement of the γ values similar to that found by Gupta et al. in f.c.c. Fe‐Ni and Fe‐Mn alloys was observed in these ternary alloys.
Magnetic form factor of molecular oxygen
Authors: Alikhanov R. A. , Ilyina I. L. , Smirnov L. S.
Published: July 2007

Using neutron diffraction the magnetic form factor f of oxygen is investigated in the solid monoclinic α‐phase (T < 23.88 °K). The antiferromagnetic reflections of α‐O2 (001) and (100), containing the purely spin magnetic scattering on π‐electrons, may give the values of f for sin θ/γ equaling to 0.1047 and 0.1242, respectively. The data of magnetic diffraction on KO, are also considered: in the magnetic structure proposed the antiferromagnetic reflections (001) and (110) (sin θ/γ is equal to 0.0735 and 0.1260, respectively) are again due to the orientation of the π‐orbital spin moments (orbital moment is frozen). The whole set of obtained values f for O2 and O2 are in reasonable agreement with the calculated dependences of f.
The transverse spin‐lattice relaxation time of conduction electrons at high magnetic fields
Authors: Kalashnikov V. P. , Bikkin H. M.
Published: July 2007

The spin‐lattice relaxation time for the transverse components of the conduction electron spin magnetization is calculated in high magnetic fields, taking into account various spin‐lattice interactions.
On the kinetics of systems with discrete energy levels
Authors: Aminov L. K.
Published: July 2007

The nonlinear generalization of the Konstantinov and Perel diagram method is used for a derivation of the quantum kinetic equation. Under definite conditions this equation may be rewritten as a differential equation analogous to that known from the theory of paramagnetism as the Wangsness‐Bloch equation, but the relaxation term of which is not limited by the second order in a corresponding interaction. This fact allows to investigate the contribution of multiphonon relaxation processes to the rate equations for populations of the energy levels of systems with discrete energy levels. It is made clear that the relaxation parameters of the rate equations in general do not coincide with the total probabilities of transitions between levels calculated by the perturbation theory. It is shown how the procedure of the calculation of two‐phonon (Raman) transitions is modified when an intermediate level occurs inside a frequency spectrum of the lattice vibrations.
EPR investigations on Ti3+‐associated centres in hexagonal CdS single crystals
Authors: Böttcher R. , Dziesiaty J.
Published: July 2007

EPR measurements on titanium doped CdS single crystals at T = 27 K reveal the existence of six magnetic complexes with orthorhombic structure and S = 1/2. They are attributed to defects of Ti3+ on normal Cd sites associated with an hitherto unknown acceptor like impurity replacing Cd on one of the six nearest possible Cd sites.
Black‐white contrast figures from small dislocation loops II. Application of the first order solution to small loops in ion‐irradiated tungsten foils
Authors: Häussermann F. , Rühle M. , Wilkens M.
Published: July 2007

In a recent paper it was shown that small dislocation loops in b.c.c. metals (in this case in tungsten, irradiated with 60 keV gold ions) show under certain diffraction conditions very special contrast figures. Theoretical contrast calculations using the analytical solution of the diffraction contrast differential equations, described in part I, are applied to the interpretation of the defect images. It is shown that the contour diagrams calculated for a variety of defect configurations and diffraction conditions agree even for fine contrast details very well with the observed contrast figures of the defects. This comparison of the theoretical and observed images allows to identify Burgers vectors and habit planes of the small dislocation loops (diameters ⪅ 50 Å).
Influence of a uniform electric field on the intraband Faraday effect
Authors: Kolesov V. V.
Published: July 2007

The quantum theory of the complex dielectric tensor εij(ω, q), which has been developed in [6], is extended to the case of crossed electric and magnetic fields. The quasi‐classical approximation is considered and the results are compared with earlier papers [6 to 9]. The expression for the complex conductivity tensor δij(ω, q) is used for studying the influence of the external uniform electric field on the intraband Faraday effect in semiconductors with simple band structure in two cases: the classical magnetic field and quantum limit. A brief discussion of the results is given.
Die Elektronendichteverteilung in Alkalihalogeniden und Silberhalogeniden in der Löwdinschen Näherung
Authors: Bauer R.
Published: July 2007

Für LiF, NaF, KF und NaCl wird die Elektronendichteverteilung für Raumtemperatur in der Löwdinschen Näherung berechnet und rnit Messungen an LiF und NaCl verglichen. Die Löwdinsche Näherung wird qualitativ auf die Silberhalogenide angewendet; das Ergebnis für die Dichteverteilung und die Bindung wird mit experimentellen Ergebnissen verglichen. Die Löwdinsche Methode ist für Alkalihalogenide eine gute Näherung; zur Beschreibung der Silberhalogenide ist sie jedoch unzureichend.
Coupled plasmon‐LO phonon modes in tellurium
Authors: Selders M. , Grosse P.
Published: July 2007

In tellurium a coupling of the plasmons with the longitudinal polar optical phonons due to the macroscopic polarisation field is expected. The eigenfrequencies are calculated, for coupled modes propagating parallel and perpendicular to the c‐axis of the uniaxial crystal. From reflectivity measurements on heavily Sb‐doped tellurium crystals the eigenfrequencies of these modes are determined on samples with plasma frequencies nearly equal to the frequency of the polar LO‐modes.
The optical absorption of MgF2, MgCl2, and MgBr2 in the vicinity of the Mg L‐shell transitions
Authors: Rabe P. , Sonntag B. , Sagawa T. , Haensel R.
Published: July 2007

The Mg++ LII, III ‐absorption spectra of evaporated thin films of MgF2, MgCl2, and MgBr, have been measured in the energy range from 50 to 150 eV. Sharp absorption bands due to excitons were found at the onset of transitions from the 2p‐shell of Mg++ around 52 eV. At higher energies transitions from the 3d‐level of Br‐ and from the 2s‐level of Mg++ show up as absorption maxima. The spectra are compared with those of metallic Mg, and the corresponding alkali halides. The measurements were performed by using the synchrotron radiation of the electron synchrotron DESY.
Absorption investigations on alkaline earth fluoride mixed crystals
Authors: Görlich P. , Ullmann P.
Published: July 2007

Some results are given of absorption investigations of alkaline earth fluoride crystals doped with impurity alkaline earth cations – CaF2:Sr, CaF2:Ba, SrF2:Ca, SrF2:Ba, and BaF2:Sr. These crystals were exposed to X‐rays at room temperature and at 84 °K. The absorption spectra recorded at these two temperatures differ considerably. The room temperature spectrum is similar to the spectrum of Li+‐, Na+‐, and K+‐doped CaF2 and SrF2 crystals, which were subtractively coloured at room temperature. The low‐temperature spectrum corresponds to a modified spectrum of the pure alkaline earth fluoride crystals after subtractive coloration. A new model of centres, the FAE centre, is suggested. In this centre one of the lattice cations, tetrahedrally surrounding the F‐centre electron, is replaced by an impurity alkaline earth cation.
Nuclear magnetic resonance in single‐crystal lead
Authors: Lüders K. , Hechtfischer D.
Published: July 2007

NMR‐signals from an oriented lead single crystal were obtained at 4.2 K for the [001] and [110] direction parallel to the magnetic field. A spectrometer with a superconducting magnet and digital data acquisition was used. The orientation dependence of the second moments of the line was employed to determine the value of the pseudodipolar coupling constant B(rij) for the first two shells of nearest neighbours.
The transition region from paramagnetism to ferromagnetism of the transition metals and their alloys
Authors: Vogt E.
Published: July 2007

The terms “nearly” or “weakly” ferromagnetic mean in the collective electron theory of Stoner: the quantity αXo in the “enhancement factor” D = X/Xo = (1 – αX0)−1 is in the first case only a little smaller, in the second case only a little greater than one (X0 spin susceptibility without interaction, α molecular field coefficient). A theory developed for such cases by Wohlfarth and Edwards yields some simple expressions for the temperature or field dependence of the magnetization. The theory can be applied only on condition that the constituants of the alloy form a common d‐band (for example RhNi). But often that is not so. In such cases (e.g. RhCo), the transition from paramagnetism to ferromagnetism obviously occurs by augmentation of localized d‐states with or without magnetic moment. Some examples are described. In the system CuNi, the transition is prepared by the formation of superparamagnetic clusters at ≈32 atyo Ni; interaction of the clusters produces ferromagnetism at ≈44 atyo Ni (Kouvel and Comly).
Inelastic incoherent neutron scattering from impurities in crystals
Authors: Cohen S. S.
Published: July 2007

We present an extremely simple formulation of inelastic incoherent neutron scattering from impure crystals. The formulation treats both mass and central‐force‐constant changes at the defect site in a closed form which is immediately amenable to an experimental analysis.
Quantitative investigation of the n = 1 exciton line of the green series of Cu2O by a wavelength modulation technique
Authors: Daunois A. , Merle J. C. , Deiss J. L. , Nikitine S.
Published: July 2007

The n = 1 line of the green series of Cu2O has been investigated recently using a differential electroabsorption method. The oscillator strength of this line has also been evaluated theoretically and compared to a rough experimental measurement. In this paper, a method is developed to deduce the oscillator strength from the differential wavelength modulated spectrum and a more accurate value is obtained for the n = 1 green line. It is confirmed furthermore that this line is not polarized which implies a predominant magnetic dipole character.
Temperature dependence of the hyperfine field at iron atoms around the nonmagnetic impurities Al and Ga
Authors: Vincze I. , Cser L.
Published: July 2007

The temperature dependence of the hyperfine field at Fe atoms in iron‐based alloys containing Al and Ga impurities was measured by Mossbauer method between liquid nitrogen temperature and the Curie point. No difference was found in the values of the relative hyperfine fields at Fe atoms near and far from the impurity. This result is inconsistent with the prediction of a simple Heisenberg model, but is in good agreement with that of a band model.
Jahn‐Teller Effect on Transition Metal Ions in Silver Halides II. Cr2+(3d4)
Authors: Koswig H. D. , Retter U. , Ulrici W.
Published: July 2007

The temperature dependence of the two near infrared absorption bands of AgCl:C2+ and AgBr:Cr2+ has been measured. The low‐energy band having a temperature independent oscillator strength is assigned to the transition between the splitting levels of the 5Eg ground state. This splitting of about 6000 cm−1 is interpreted as due to a dynamic Jahn‐Teller effect. The high‐energy band is assigned to the → 5T2g transition.
Electronic States of Dislocations in Germanium
Authors: Güthm W.
Published: July 2007

Experiments show that the optical absorption of electronic states in germanium dislocations has a pronounced polarization vector in the direction of the Burgers vector. It is concluded that electronic states split off from the energy bands arise due to the effect of stress near the dislocation lines. The calculated polarization vector of the optical transition coincides with the direction found in the experiment.
Effective Hamiltonian Method in the Theory of Activated Crystals
Authors: Nikiforov A. E. , Mitrofanov V. Ya. , Men A. N.
Published: July 2007

A generalization of the effective Hamiltonian method (EFH) proposed in [1, 2] is developed for all SR groups and for the case of “strongly interacting levels”. Such an approach makes it possible to calculate the relative transition components in the framework of a semi‐empirical method. The proposed EFH method is based on the use of eigenfunctions the zeroth‐order Hamiltonian. This yields the possibility to evaluate the EFH parameters any order of the perturbation theory. The second part of the paper is devoted to the development of the EFH method for the calculation of the energy spectrum of a pair of coupled impurity ions in crystals.
Weak Magnetic Field Dependence of the Thermoelectric Effect in Heavily Doped Semiconductors at Low Temperatures
Authors: van Cong H. , Mesnard G.
Published: July 2007

The field dependence of the thermoelectric effect is studied, using a simplified model of heavily doped semiconductors, by Green's function methods and the Feynman‐path integral formulation applied to disordered systems, already developed in five previous papers. Two important cases are discussed. In the first, an ordinary n‐type semiconductor is considered, assuming that the carrier concentration is equal to the donor one; in the second, the carrier concentration is rised as the third root of the total concentration of impurities.
High Pressure ENDOR Search for the K′‐Center
Authors: Wolbarst A. B.
Published: July 2007

An ENDOR study of additively colored KBr was made at 10 and 11 kbar. No deviations from normal F‐center spectra were noted, indicating that the same ground state serves both F‐ and K′‐centers. A model involving stress‐distorted excited states is proposed.
Investigation of Hyperfine Field Distributions in FeSn Alloys by the Mössbauer Effect
Authors: Cser L. , Gorobchenko V. , Lukashevich I.
Published: July 2007

Hyperfine field distributions around tin impurities were investigated for both iron and tin sites. It is shown that spin density perturbations detected by the Mössbauer effect on both the iron and tin nuclei are similar. The conduction electron polarization contribution to the hyperfine field on the iron is equal to (−162 ± 18) kOe.
Coherent Magnetoelastic Effects in Ferromagnets with Impurities
Authors: Los V. F.
Published: July 2007

The spectrum of elementary excitations in a ferromagnet with weakly bonded impurity spins is considered in the region where the phonon frequency ωkj coincides with or is close to the excitation energy of the impurity atom spins |ω0|. It is shown that when the magnetic impurity concentration is high enough the coherent resonance magnetoelastic interaction occurs of the phonons with the low‐lying quasi‐local spin excitations which appear near the weakly bonded impurity spins. The result is that in a general case (2 S + 1) branches of the bonded collective impurity magnetoelastic excitations are formed in the resonance region ωkj ≈ |ωw0|(S is the spin of the impurity atom).
X‐Ray Spectra of Disordered Alloys (I)
Authors: Sokolov O. B. , Babanov Yu. A.
Published: July 2007

The intensity of X‐ray emission and absorption spectra of disordered substitutional alloys is calculated by the Green's function method. The results of the calculations help to explain qualitatively a series of experimental data.
Charge‐Transfer Spectra of Transition Metal Ions in Silver Halides
Authors: Ulrici W.
Published: July 2007

On AgBr and AgCl crystals containing substitutional Ti3+, V3+, or Cr3+ ions absorption bands are measured in the near UV having oscillator strengths of 10−2 to 10−1. In an MO energy level scheme of the MeX cluster these absorption bands are interpreted as due to ligand‐metal charge transfer transitions. The electron is transferred from the t2 u(π) level to the t2 g(π*) level (Me = Ti, V) and to the eg(σ*) level (Me = Cr), respectively.
Electric Field Effects on Excitons in Cuprous Oxide
Authors: Brahms S.
Published: July 2007

The electric field induced changes of the 1S and 2S exciton states created at the E and E ± Δ0 transitions in cuprous oxide have been investigated. The ground exciton states exhibit polarization effects which have been attributed to the action of the applied field on electronic wave functions. A removal of the degeneracy of the Γ conduction band is suggested.
Interaction of Adsorbed Molecular Oxygen with Thin Superconducting Aluminum Films
Authors: Ostertag U.
Published: July 2007

Using tunnel diodes of the structure aluminum–oxide‐aluminum‐oxygen, a characteristic change in the density of states of thin superconducting films after covering with oxygen was found. The best fit of calculated curves to the measured characteristics was obtained for a theoretical model which assumes a pairbreaking mechanism varying locally in strength according to the local film thickness. From this fit, a maximum pairbreaking parameter and, by calculation, a maximum theoretical shift of the transition temperature is obtained. There is good agreement with the observed depression of the transition temperature.
Multiple Scattering of Thermal Neutrons by a Perfect Crystal III. Calculation of the Neutron Wave Field
Authors: Solbrig H.
Published: July 2007

Explicite solutions for the neutron wave function are calculated for the following situations: the quasioptical case (where the wavelength is large compared with the lattice constants) and both the symmetrical Bragg‐ and Laue‐cases. The calculation is based on the results of two foregoing papers. The discussions are concentrated especially on the following two points: firstly on the quasioptical case where the crystal behaves like a homogeneous medium with a refractive index containing an effective scattering amplitude f/(1 + i k f) being real for non‐absorbing nuclei, secondly on the modifications of the standing wave fields in both the symmetrical Bragg‐ and Laue‐cases if the Bragg‐conditions are not exactly fulfilled. The theory remains applicable for strong resonance absorption by the nuclei too.
A New Model for Covalent Semiconductors with Topological Disorder
Authors: Hulin M. , Pottier N.
Published: July 2007

A simple model is proposed, as an alternative of the LCAO formalism, to study disordered materials where the atoms are supposed to keep the same coordination number. It is shown that the possible energies can be calculated easily after the eigenvalues of the “connectivity matrix”, and that forbidden energy bands still appear, as already shown to be true within the LCAO formalism.
Isotropic Limiting Behaviour of the Six‐Dimensional Formalism of Anisotropic Dislocation Theory and Anisotropic Green's Function Theory. I. Sum Rules and Their Applications
Authors: Nishioka K. , Lothe J.
Published: July 2007

The isotropic limiting behaviour of the six‐dimensional anisotropic dislocation theory of Stroh [1] is studied. By means of certain sum rules, it is possible to go to the limit of isotropy without a detailed study of the degeneracies arising for the eigenvalues and the eigenvector system. The sum rules combined with the perturbation expressions of Malkn and Lothe [2] also readily give expansions for dislocation energy factors and Green's functions to the first order in the deviation from isotropy.
Crystal Field Theory of Hexagonal Fluorides of the Type ABF3
Authors: Jäger E.
Published: July 2007

On the basis of the point charge model the crystal field potential of hexagonal fluoroperovskite ABF3, is calculated. Explicit expressions of the distances and angles of those ions forming the ten nearest environments of a B‐ion are given. As an example the crystal field potential acting on the Ni2+ ions in RbNiF3, is Calculated. Comparison with optical spectra shows that the calculated and measured crystal field splittings 10 Dq differ by a factor 4 to 5.
Optical Properties and Reorientation of M Centers in NaF
Authors: Collins W. C. , Schneider I.
Published: July 2007

The 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

The 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

For 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

The 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

Previous 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

Energies 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

Extended 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

The 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

The 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

The 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

Measurements 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

The 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

Cu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

The 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

The 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

Three 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

Die 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

The 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

The 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

The 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

The 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

The 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

The 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

The 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

Extrinsic 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

In 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

A 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

La 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

Radioaktives 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.