bluuebunny/crossref_metadata_2025 huggingface dataset:
The Range of g‐Factors and the Breakdown of Motional Narrowing in Conduction Electron Spin Resonance
Authors: Dupree R. , Holland B. W.
Published: July 2007

It is suggested that the recent measurements of electron spin resonance in aluminium [1] indicate that motional narrowing is absent at low temperatures and the linewidth is deter‐mined by the spread in g‐factors over the Fermi surface. Using first order perturbation theory an upper limit to the g‐shift as a function of position on the Fermi surface is derived, and its consistency with all the g‐shift observations on metals to date is demonstrated. An upper limit to the range of g‐factors over the Fermi surface of aluminium is estimated and is found to give strong support to the hypothesis that motional narrowing is absent at low temperatures. It is pointed out that the usual simple theories of motional narrowing are not applicable and some implications for other metals are discussed.
Shell Model Treatment of the Vibrations of Crystals Containing Substitutional Defects I. U‐Center Localized Modes
Authors: Page J. B. , Strauch D.
Published: July 2007

A shell model treatment of the harmonic vibrations of lattices containing substitutional defects is given and is applied to the problem of the infrared‐active localized modes of U‐centers in alkali halide crystals. Long‐range effects due to the shell motions and to altered core and shell charges are included, as are the effects of spherical deformations of the ions. For a U‐center polarizability of 1.9 Å3 and a shell charge of −e it is found that the fractional decreases in the defect's nearest neighbor shell‐shell and isotropic core‐shell spring constants are between 0.30 and 0.55 and greater than 0.75, respectively, for U‐centers in nine different alkali halides.
Transient Acousto‐Electric Phenomena in Semiconducting Piezo‐Electric Crystals
Authors: Autin B.
Published: July 2007

In a semiconducting piezo‐electric crystal the intensity of the current remains proportional to the applied voltage during an incubation time under acoustic gain conditions. The departure from Ohm's law is ascribed to two processes relevant to the build‐up of the acoustic flux: a strong acousto‐electric current and a negative differential conductivity. The onset times of these two processes are calculated by assuming that the electric field is uniform inside the crystal. It is shown that the incubation time is of σdiff < 0 type if the electron drift velocity is slightly higher than the sound velocity and changes into acousto‐electric current type for higher drift velocities.
Studies on the Nature of CdS Single Crystal Sensitization by Etching
Authors: Sheinkman M. K. , Tyagai V. A. , Snitko O. V. , Ermolovich I. B. , Belenky G. L. , Nbondakenko V.
Published: July 2007

The sensitizing of CdS single crystals by etching in a KOH (NaOH) solution is investigated by several photoelectric and luminescence methods. It is shown that the sensitizing is mainly due to the creation of slow sensitizing r‐centres of recombination with parameters identical to those of recombination centres in naturally photoconductive crystals. Two mechanisms are proposed to explain the sensitizing and these take into account the dif‐fusion of vacancy complexes and hydroxyle groups.
Application of the S.C.F. Method of Lattice Dynamics to the Coulomb Lattice
Authors: Pietrass B.
Published: July 2007

Anharmonic effects of the Coulomb‐lattice vibrations are investigated by the time‐deendent s.c.f.‐method. In contrast to the traditional treatment using the lattice theory of Born there are higher branches in the dispersion relation of the lattice vibrations which represent anharmonic elementary excitations. In the harmonic oscillator approximation for the low s.c.f.‐states, which is justified for sufficient lylow density, Kohn's sum rule is generalized to include the anharmonic branches. Taking into account anharmonic branches, the instability of the lattice state above a certain density is indicated by imaginary eigenfrequencies in the transverse vibration mode. The contribution of the anharmonic branches to the zero‐point energy is evaluated.
ESR Studies of Different Se Centres in Silver Halides
Authors: Höhne M. , Stasiw M.
Published: July 2007

The ESR spectrum of AgBr:Se crystals which have been irradiated at 120 °K with green light is changed by heating the crystals to 170 °K. The spectrum obtained after heating was recently investigated and attributed to a Se centre. In the present paper the spectrum observed before heating is analyzed with regard to g‐values, and superhyperfine and hyperfine structure. This spectrum is also found to be due to a Se centre of ortho‐ rhombic symmetry The two centres differ in their surroundings and a model of this situation is developed. The investigations are extended to AgCl:Se.
Forward Current Injection Modulation of Photocurrent in p‐n Heterojunctions
Authors: Tansley T. L.
Published: July 2007

The effect of applied forward bias upon the photocurrent observed in p‐n heterojunctions has been investigated in the systems GaAs‐Ga(AsP) and (GaIn)As‐GaAs. In all the heterodiodes measured the photocurrent was found to cut‐off sharply at a well defined bias and this cut‐off voltage proved extremely sensitive to temperature. The observation that the excess photocurrent is simply related to the dark‐current leads to a model in which photo electrons may rapidly thermalize in the conduction band notch if the equilibrium injected population is sufficiently large.
Elektronenmikroskopische Untersuchung von Fehlstellenagglomeraten in ionenbestrahlten Kupferfolien II. Entstehung der Agglomerate
Authors: Diepers H.
Published: July 2007

Der Entstehungsmechanismus der in Cu‐Folien durch Beschuß mit Ar‐Ionen erzeugten Zwischengitteratomagglomerate wird untersucht [1]. hierzu wird einerseits die Abhängigkeit der Tiefenverteilung der Agglomerate von der Orientierung der Folie und der Energie der Ionen, andererseits die Abhängigkeit der Agglomeratdichte von der Ionendosis (Dosis‐kurven) bei verschiedenen Folientemperaturen gemessen. Es ergab sich, daß die Agglomerate aus Eigenzwischengitteratomen des Cu aufgebaut sind, die durch gerichtete Stoßprozesse in Form dynamischer Crowdionen ins Gitter eindringen. Der Mechanismus der Agglomeration wird an Hand der Dosiskurven, der Tiefenverteilungskurven und weiterer Experimente zur Bestimmung der Agglomeratgröße in Abhängigkeit von der Dosis, der Temperatur und der Tiefenlage diskutiert.
Experimentelle Ergebnisse zur Temperaturabkängigkeit der Sekundärelektronen‐Emission an polykristallinem Nickel im Intervall 100 ≦ T ≦ 600 °C
Authors: Hölzl J. , Heimann B.
Published: July 2007

An einer 99,9% reinen, polykristallinen Ni‐Zielplatte wird im UHV die Sekundärelektronen‐Emission im Energiebereich der Primärelektronen 50 ≦ Vp ≦ 1000 eV gemessen. Im einzelnen werden folgende Untersuchungen durchgeführt: 1. Bei konstanter Primär‐energie wird die Temperaturabhängigkeit der Koeffizienten der Sekundärelektronen‐Emis‐sion σ, δ und η im Temperaturintervall 100 ≦ T ≦ 600 °C gemessen. Der Widerspruch in bisherigen Ergebnissen älterer Arbeiten bezüglich einer Temperaturabhängigkeit von σ konnte dahingehend entschieden werden, daß σ und δ, nicht hingegen η am ferromagnetischen Curie‐Punkt eine reproduzierbare Anomalie zeigen. 2. Die Energieverteilung von Sekundärelektronen wird einerseits im ferromagnetischen, andererseits im paramagnetischen Zustand der Probe gemessen. Es ergeben sich bei konstanter Primärenergie für beide Probenzustände unterschiedliche Energieverteilungskurven. — Ein Vergleich der unter 1. und 2. mitgeteilten Ergebnisse mit denen einer Modellrechnung, die den Einfluß oberflächlicher magnetischer Streufelder auf niederenergetische Sekundärelektronen abschätzt, zeigt, daß die Anomalie in σ resp. δ nicht ausschließlich als Folge eines oberflächlichen Streufeldeffektes zu interpretieren ist.
Electrical Properties of n‐Type CdSe
Authors: Btirmeister R. A. , Stevenson D. A.
Published: July 2007

The electrical properties of n‐type CdSe were studied over the temperature range of 4.2 to 300 °K. Measurements were made in both as‐grown crystals and crystals annealed under controlled Cd pressures. Hall effect measurements on low resistivity specimens indicate the presence of a donor level 0.014 eV below the conduction band, with concentrations typically ≈︁ 1016 cm‐3. Analysis of the Hall mobility data indicates that the predominant scattering mechanism at room temperature and above is polar optical mode scattering. The magnetoresistance effects observed are consistent with the energy structure determined by previous optical studies. The transport properties exhibited typical characteristics of impurity band conduction at low temperatures (< 77 °K), including negative magnetoresistance.
Magnetoresistivity of Metals I. General Theory
Authors: Seeger A. , Mann E. , Clauseckek K.
Published: July 2007

A general theory is given for the low‐temperature magnetoresistivity of metals. This is valid for arbitrary shapes of the Fermi surface, for arbitrary elastic scattering mechanisms, and for all magnetic field strengths with the exception of the so‐called quantum limit. The derivation of the Boltzmann equation and the necessary conditions on the scattering probabilities and potentials are carefully treated. It is shown that the electrical conductivity in a magnetic field (including the Shubnikov‐de Haas effect) can be calculated exactly if the scattering of the electrons is formulated in terms of Wannier functions. The simplifications of the general case due to symmetries are discussed.
Distortion Correction in Anomalous Absorption Coefficients
Authors: Kubiyama M.
Published: July 2007

Based on a recent theory of X‐ray diffraction by a distorted crystal completed by the present author, the temperature and distortion corrections in anomalous absorption coefficients have been studied in the case of a single symmetric Bragg reflection in transmission (symmetrical Laue case). If the distribution of atomic displacements is given, then the anomalous absorption coefficient has a distortion correction of the same form as the Debye‐Waller factor in terms of the second moment of the distribution. If the displacement of atoms in a distorted crystal is replaced by a proper time‐average value of the thermal motion of atoms, then the temperature correction in the absorption coefficient is given by the Debye‐Waller factor multiplied by the structure factor.
On the adiabatic potential of a complex system
Authors: Ledovskaya E. M.
Published: July 2007

The energy of an electronic state of a complex system, consisting of a number of interacting subsystems, is considered. The interaction of these subsystems is taken as a perturbation and the calculation of the adiabatic potential uses the iterative method of perturbation theory for nonorthogonal functions. The second order correction to the energy is determined.
Thermal and infrared quenching of photoconductivity in n‐InSe single crystals
Authors: Abdullaev G. B. , Kh. Alieva M. , Mamedova A. Z.
Published: July 2007

Thermal and infrared quenching of photoconductivity is studied in sensitive n‐InSe single crystals. It is found that thermal quenching occurs from 143 to 223 °K and that infrared quenching takes place below 165°K. Infrared quenching bands are found at 0.75 eV and 0.9 eV. The thermal quenching indicates a level which is 0.2 eV from the upper limit of the v‐zone and gives the electron and hole capture cross‐section ratio Sp/Sn as 2 × 102 for the sensitizing centres and their concentration ratio N2/N1 as 2. On the basis of the thermally stimulated current the binding energy of the attachment level is 0.16 eV.
On the four‐axis hexagonal reciprocal lattice and its use in the indexing of transmission electron diffraction patterns
Authors: Okamoto P. R. , Thomas G.
Published: July 2007

A four‐axis hexagonal reference basis can be constructed in the reciprocal space of hexagonal crystals in such a way that the resulting lattice contains as a subset all the points of the conventional reciprocal lattice. All other points not belonging to this subset have no physical significance since they have non‐integral indices and hence cannot represent real crystal planes. Since these points cannot register as spots in an actual diffraction pattern, the four‐axis hexagonal lattice and the conventional reciprocal lattice are physically indistinguishable. _ The interpretation of diffraction patterns of hexagonal crystals is easier when indexing is referred to the four‐axis basis. The necessary crystallographic relationships can be obtained directly in terms of Miller‐Bravais indices using elementary vector analysis and when applied to Kikuchi electron diffraction maps, the problem of determining the foil orientation becomes especially simple.
Thermo‐ und Elektrotransport in β‐titan und β‐zirkonium
Authors: Dübler H. , Wever H.
Published: July 2007

In β‐Titan und β‐Zirkonium mit einem Reinheitsgrad von nahezu 99,9% erfolgt der Thermotransport zum heißen Probenende, der Elektrotransport zur Anode. Das Verhältnis von Transportwärme Q* (in kcal) und effektiver Ladung z* beträgt für β‐Ti 43, für β‐Zr55. Die Aktivierungsenergie des Thermotransports hat für β‐Ti einen Wert von etwa 27 kcal, für β‐Zr von 16 kcal. Sie weicht damit für β‐Zr deutlich von dem für die Selbstdiffusion bekannten Wert ab. Die Messungen schließen die Möglichkeit aus, das anomale Diffusionsverhalten der untersuchten Metalle durch einen Zenerschen Ringmechanismus zu erklären. Eine widerspruchsfreie Deutung aller Versuchsergebnisse ist dagegen durch die Annahme eines Versetzungsmechanismus möglich, bei dem der Bereich um den Versetzungskern, in dem die Diffusion beschleunigt ist, für β‐Ti größer als für β‐Zr ist.
Deformation of molybdenum single crystals at slow rates of strain
Authors: Guiu F.
Published: July 2007

Molybdenum single crystals were deformed in tension, and the relationship between stress, strain, and strain rate was studied in the pre‐yield region. The high work‐hardening rate of the pre‐yield deformation is explained in terms of the exhaustion of mobile edge dislocation segments. The rate of exhaustion, ∂ log ϱ/∂ϵ, is of the order of 103 to 104. The temperature and strain rate dependence of the stress required to deform the crystals at strain rates < 10−7 s−1 was investigated at strains > 0.01. The activation energy and activation volume have values between 2 and 4 eV, and between 50 and 100 b3 respectively. This result suggests that the mechanism of overcoming the Peierls friction is not rate controlling at the slow rates of strain. Alternative interpretations are discussed.
Optical absorption of the impurity ag and models for the E‐Band in an alkali halide
Authors: Arora H. L. , Kim S. , Wang S.
Published: July 2007

A method used in more recent work is applied to the calculation of optical absorption of a neutral silver atom (AgI) in KCl. The predicted results show that the E‐band in KCl: Ag is not due to the impurity AgI located at a substitutional site of the host crystal. From present theoretical results we then propose two speculative models for the origin of the E‐band: 1. The E‐band is due to the impurity AgI located at an interstitial site tetrahedrally surrounded by four alkali ions as well as by four halide ions. 2. The E‐band is due to the interstitial impurity AgI perturbed by some complex whose perturbation is very small.
Electron microscope observations of twinning and phase transformations in indium sulfide crystals
Authors: Fitzgerald A. G. , Thomas G.
Published: July 2007

Thin crystals of indium sulfide with the crystal structures corresponding to the compositions InS and In6S7 have been grown by means of a chemical transport reaction. Phase transitions have been induced by beam heating in the electron microscope and have been identified by electron diffraction. Crystals of InS occasionally contain twins when examined in the electron microscope. The twins presumably originate during the growth process. On subjecting these crystals to high intensity electron irradiation in the electron microscope large numbers of twins are nucleated. On continued electron irradiation structural transformations occur in these crystals. Crystals with the orthorhombic InS structure transform to the monoclinic In6S7 structure and on further electron irradiation a further transformation to the tetragonal In2S3 structure occurs. When crystals with the monoclinic In6S7 structure are subjected to high electron beam intensities in the electron microscope, a structural transformation also occurs and the crystals transform to the tetragonal In2S3 structure.
Computer calculations for vacancies in alkali halides with NaCl structure
Authors: Scholz A. H.
Published: July 2007

In calculations of the energies of point defects in ionic crystals one conventionally divides the crystal into two regions. Region I contains the defect and a number of its neighbours and all relaxations in region I are handled explicitly. Region II is the rest of the crystal and assumed analytical solutions are used here. All previous calculations have used a rather small region I. A computer method presented in a previous article [12] has been significantly improved and permits the treatment of a large region I containing 256 ions around the vacancy. In particular the polarization energy UPol was handled much more accurately than before, the electric fields EP and EDip in region I due to monopoles and dipoles of the ions being the relevant quantities. Since the lattice around the vacancy has full cubic point symmetry we expand EP and EDip in power series of the displacements σ and dipoles m, and the associated coefficients of such series were evaluated numerically. The Coulomb energy UCoul was treated in a similar way. Hence we obtained suitable and very fast computer programmes for the lattice energy of region I. The evaluated 4733 constant coefficients are included in these programmes. Following Boswarva and Lidiard the effect of region II had to be taken into account; also the interaction of ions in region I with those in region II was estimated. Several numerical results for the vacancy calculations are described.
Piezoelectricity in iii‐v compounds with a phenomenological analysis of the piezoelectric effect
Authors: Arlt G. , Quadflieg P.
Published: July 2007

The piezoelectric stress constants e14 of InSb, InAs, GaSb, GaAs, and AlSb have been measured at room temperature and found to be 0.071; 0.045; 0.13; 0.16, and 0.068 C/m2 respectively. If the III‐V compound crystals are expanded in the  direction, the A‐faces (metal atoms) become negatively charged, in contrast to II‐VI compounds, in which the equivalent faces become positively charged. Using a model of a layered lattice, we show that three different mechanisms may contribute to the piezoelectric effect. These mechanisms are 1. the internal displacement of the ionic charge, 2. the internal displacement of the electronic charge. 3. the change in ionicity due to strain.
On the mathematical description of electrical processes in semiconductors. i. phase space analysis in subspaces of dimension lower than three
Authors: Oberländer S. , Sikorski S.
Published: July 2007

A theoretical study is made of the transport of non‐equilibrium carriers in semiconductors in the stationary case which includes arbitrary deviations from thermodynamic equilibrium. Classes of systems of solutions with various qualitative properties are given without approximation for the system of differential equations. The equations are the continuity equations with a recombination law based upon the law of mass action, and the common current equations and Poisson's equation. The systems of solutions are applicable to various problems in homogeneous semiconductors and inhomogeneous semiconductor devices. They offer possibilities of testing numerical methods and obtaining new approximate methods. Finally they lead to some remarks on the neutrality approximation.
Vacancies, divacancies, and self‐diffusion in platinum
Authors: Schumacher D. , Seeger A. , Härlin O.
Published: July 2007

Thin wires of high‐purity platinum are quenched from high temperatures by means of the helium‐II technique. After quenching from about 1000 °C the electrical resistivity is found to recover between 380 and 520 °C with an activation energy of (1.33±0.05) eV. After quenching from near the melting point the recovery occures between 200 and 460°C and can be decomposed into two second‐order processes with activation energies of 1.0 and 1.34 eV, respectively. The self‐diffusion data are re‐analysed allowing for the contribution of both mono‐ and divacancies. This analysis is compared critically with the results of the present quenching experiments and with previous work. A consistent set of vacany parameters is proposed for Pt.
Untersuchung der Fermifläche des Molybdän durch Zyklotronresonanzmessungen
Authors: Herrmann R.
Published: July 2007

Zyklotronresonanzmessungen im Mikrowellenbereich bei einer Frequenz von 9,7 GHz gestatteten die effektiven Massen von Molybdän und ihr Anisotropieverhalten in den kristallographischen Ebenen (110) und (121) bei einer Temperatur der Meßproben von 1,6 °K zu bestimmen. Bei beliebiger Orientierung des Magnetfeldes wurden in beiden Ebenen stets mehrere Zyklotronresonanzserien beobachtet, was auf die Kompliziertheit der Fermifläche des Molybdän hinweist. Ein Teil der beobachteten effektiven Massen konnte dem Modell der Fermifläche zugeordnet werden. Es wurde die Geschwindigkeit der Elektronen auf dem zentralen Teil der Hauptelektronenfläche, dem Elektronenjack, zu vc = 0,56 ×× 108 cm/s abgeschätzt.
X‐Ray production and thermal annealing of frenkel pairs in KCl
Authors: Giuliani G. , Reguzzoni E.
Published: July 2007

The X‐ray production and thermal annealing α‐centres (isolated negative ion vacancies) are studied in KCl as a function of purity and the temperature of irradiation. At any temperature the α‐centre production results from competition between the formation process and thermally activated destruction of negative ion vacancies. Since the latter process is strongly temperature and structure dependent, the α‐centre production is structure sensitive or insensitive depending on the temperature of irradiation. From the point of view of thermal stability the α‐centres produced by X‐rays can be divided into two groups. The first group includes α‐centres which decay below 77 °K and whose thermal stability does not depend on the purity of the sample. The second group includes α‐centres which decay in the 100 to 250 °K temperature range and whose thermal stability is strongly structure sensitive. Finally, some results on the influence of electron traps on α‐centre formation are reported.
On the specific heat of dilute magnetic alloys
Authors: Sólyom J. , Zawadowski A.
Published: July 2007

It is shown that for the Kondo model of dilute magnetic alloys a mass renormalization due to an energy dependent self‐energy causes no enhancement of the specific heat. It is proved that in the homogeneously polarized state the mass renormalization is caused by ∑ (ω) ≈︁ ‐ α ω and therefore the observed excess specific heat in dilute magnetic alloys comes from the inhomogeneity of the polarization. In external magnetic fields a contribution to the specific heat appears, which, in high field, is inversely proportional to H.
Preparation and some properties of CuP2 single crystals
Authors: Goryunova N. A. , Orlov V. M. , Sokolova V. I. , Shpenkov G. P. , Tsvetkova E. V.
Published: July 2007

CuP2 monocrystals of about 1 cm2 area are grown by crystallization from the solution in tin. The habit and the monocrystalline structure of the compound is investigated by chemical, X‐ray, and microstructure methods. Following semiconductor parameters are determined (at room temperature): Eg ≈︁ 1,4 eV, n = 7.5× 1017 to 8 × 1017 cm−3, α = + 800 μV/deg, and σ = 10 Ω−1 cm−1.
Lifetime of excited Cu+ in alkali halides
Authors: Baldini G. , Jean A. , Spinolo G.
Published: July 2007

An experimental study is made of the time decay of excited Cu+ ions diluted in potassium halides in order to determine the role of the host crystal in the impurity absorption and emission processes. The Cu+ ions are responsible for a few ultraviolet absorption bands which, after optical stimulation, give rise to emission at ≈︁ 4000 Å. The lifetime, τR, of the lowest excited state, presumably 3d94s, is measured and found to be ≈︁ 50 μs in KCl:Cu, ≈︁ 100 μs in KBr:Cu and ≈︁ 5 μs in KI:Cu). The thermal de‐excitation energies, ΔEd, are also measured and found to be ≈︁ 0,73 eV (KCl:Cu), ≈︁ 0,76 eV (KBr:Cu), ≈︁ 0,61 eV (KI:Cu). These results together with measurements of other workers may suggest that the transition 3d10 ≈︁ 3d94s, forbidden in the free ion, becomes partially allowed due to the crystal field. The implications of an off‐centre position of the Cu+ ion inthe K+ vacancy are also discussed and found to be consistent with the experimental data.
Atomic 3H center in neutron‐irradiated LiF
Authors: Kazumata Y.
Published: July 2007

LiF crystals irradiated with neutrons at 80 °K are investigated by electron spin resonance measurements. A paramagnetic centre which is due to atomic tritium is observed. The centre decays at 350 °C.
Investigation of grain boundary energetics in Er2O3 thin foils by transmission electron microscopy
Authors: Murr L. E.
Published: July 2007

The oxidation of erbium thin films directly within the electron microscope, and the subsequent grain growth and equilibration of the Er2O3 foils have allowed the true dihedral angles at grain boundary triple junctions to be calculated. It is observed that a mean dihedral angle of 120° obtains for these oxide‐ceramic films; and the comparison of the three‐dimensionally computed dihedral angles with the two‐dimensional angles measured directly from electron microscope images of grain boundary triple junctions in Er2O3 exhibited a uniqueness which questions the necessity of three‐dimensional corrections for this particular property. The distribution of relative grain boundary free energy ratios in Er2O3 foils is also calculated; and the spread of this data is interpreted to represent the effects of the relative grain orientations composing a triple junction. The mean boundary inclination is observed to be 71.1°, which suggests an influence on grain boundary equilibration in thin foils of surface image forces. The results generally indicate that the application of techniques previously utilized in the study of metallic grain boundary energetics is equally valid in certain oxide‐ceramic thin films.
Diffusion in Inert‐Gas bombarded KCl, KBr, and KI
Authors: Kelly R. , Jech Č. , Matzke H. J.
Published: July 2007

A study of inert‐gas diffusion, mainly involving Kr and Xe, in ion‐bombarded KCl, KBr, and KI has been made using bombardment energies up to 85 keV and doses up to 50 μA min/cm2. Two types of release behavior were observed, both of which were shown to be compatible with diffusion kinetics, at least to first approximation. Low doses led to release with a fairly well‐defined ΔH of 33.5, 30.5, and 28.5 kcal/mol for KCl, KBr, and KI respectively, while high doses led to release with a somewhat variable ΔH having mean values of 44, 39, and 33.5 kcal/mol for KCl, KBr, and KI respectively. It is proposed that the low‐dose release involves gas motion without an implied gas—gas or gas—damage interaction, the gas perhaps occupying the small, stable vacancy clusters recently discussed by one of the authors (Hj. M.). The high‐dose release seems, by contrast, to be affected by transient gas—gas or gas—damage interactions, and is probably identical with the process found in homogeneous‐labelling work between about 250 °C and the “knee” temperature. A third type of release, found in homogeneous‐labelling work above the “knee”; temperature, has no parallel in ion‐bombardment work. It is here tentatively attributed to the motion of small, gas‐filled bubbles, and its ΔH of 7 to 14 kcal/mol is proposed to be related to that for surface diffusion of the host crystal.
Electron microscopic investigation of lamellar mixtures of two close‐packed phases
Authors: Delaey L.
Published: July 2007

Martensitic and massive phases containing fine lamellae of two different close‐packed structures have been studied by transmission electron microscopy. The stacking sequences involved in the lamellar mixtures are ABCBCACAB and ABC, or AB and ABC, or ABC and CBA. The fine lamellae produce fringe patterns which are similar to fringe patterns due to single stacking faults. However, by tilting the foil images can be obtained that are incompatible with single stacking faults.
Approximate symmetry relations for double group k · p expansions
Authors: Broerman J. G.
Published: July 2007

A recent calculation [9] of the energies of the Δ7 (“extra”) representations of the double group of the wave vector Δ in germanium is examined. This calculation employs a double group formalism in which matrix elements of the momentum connecting Γ7+ and Γ8+ with other states are independent. It is here shown that there exist symmetry relations between these matrix elements which are only weakly broken by interband spin‐orbit interaction, and that it is thus not physically meaningful to regard the elements as independent.
Neutron Diffraction Studies of α‐FeOOH
Authors: Szytuła A. , Burewicz A. , Dimitrijević Ž. , Kraśnicki S. , Rżany H. , Todorović J. , Wanic A. , Wolski W.
Published: July 2007

Neutron spectrometric investigations are made of goethite (α‐FeOOH) of mineralogical and synthetic origin (α‐FeOOH of natural isotopic composition) and also of α‐FeOOD using a monochromatic neutron beam of λ = 1.12 Å. Some powder diffraction patterns in the temperature range from −190 to +120°C are measured. The obtained coordinates for all atoms (including those for hydrogen) in the unit cell are given. The existence of antiferromagnetic spin ordering at temperatures below +80°C is observed. A model is proposed in which the spins are aligned parallel to the b‐axis.
Thermal Capacity of Solid Nitrogen
Authors: Bagatskii M. I. , Kucheryavy V. A. , Manzhelii V. G. , Popov V. A.
Published: July 2007

The thermal capacity of solid nitrogen in the temperature range 2.6 to 15°K is investigated using an adiabatic calorimeter of original construction. The analysis of the results of this paper and the literature data on the thermal capacity allow information about the character of the rotational motion of the molecules in crystalline nitrogen to be obtained. The so‐called orientation defects give a considerable contribution to the thermal capacity near the temperature (35.6°K) of the phase transformation. In the high‐temperature β‐phase of solid nitrogen the practically free rotation of the molecule occurs.
X‐Ray Dynamical Contrast of a Planar Defect
Authors: Authier A. , Milne A. D. , Sauvage M.
Published: July 2007

The presence of a non‐diffracting lamella in an otherwise perfect crystal results in particular interference fringes on X‐ray topographs. The form and contrast of these fringes as found on section topographs have been calculated using the basic assumptions of the dynamical theory. Two different types of fringes can be distinguished: those independent of the gap thickness which are similar to stacking fault fringes, and those characteristic of a gap, whose shape depends sharply on the gap thickness. It is shown that among these interference systems some fringes of high contrast exist even in absorbing crystals. The experimental results obtained with various geometric arrangements are in good agreement with the theoretical predictions.
Slip Line Pattern and Active Slip Systems of Tungsten and Molybdenum Single Crystals Weakly Deformed in Tension at Room Temperature
Authors: Kaun L. , Luft A. , Richter J. , Schulze D.
Published: July 2007

Electron zone‐refined tungsten and molybdenum single crystals are deformed in tension at room temperature. The slip systems on the cylinder‐shaped tensile specimens are determined using the light as well as the electron microscope. The slip line pattern depends sensitively on the orientation of the stress axis. Single slip on the crystals investigated is not observed. The slip occurs preferentially on planed of type {110}, but usually further slip planes of the 〈111〉 zone are also active. The slip band structure is discussed in terms of elementary slip processes.
The Fine Structure of Spots in Electron Diffraction Resulting from the Presence of Planar Interfaces and Dislocations. III. Domain Boundaries
Authors: Gevers R. , van Landuyt J. , Amelinckx S.
Published: July 2007

The fine structure of electron diffraction spots caused by the presence of domain boundaries (δ‐boundaries) is derived theoretically. The same method is used as in part I, namely the Fourier transforms of the transmitted and scattered intensities are calculated and discussed. The predicted fine structure consists in a fourfold splitting of the scattered as well as of the transmitted beams in a direction perpendicular to the interface. It is shown that the relative intensities and the spacing of the spots in this quadruplet are strongly influenced by the anomalous absorption and by parameters such as e.g. Δs and s. The effect of domain boundaries on the multiplicity and nature of the splitting is discussed. Finally the relation between the constituent beams and the fringe pattern visible in transmission electron microscopy at domain boundaries is analysed. Excellent agreement is found with the pattern characteristics previously derived from the analytical discussion of the transmitted and scattered intensities.
Optical Absorption Edge of AIN Single Crystals
Authors: Pastrňák J. , Roskovcová L.
Published: July 2007

From measurements of the absorption coefficient of AIN single crystals the direct band gap values EG = (5.88 ± 0.05) eV and EG = (5.74 ± 0.05) eV for E ⟂ c and E ∥ c, respectively, are determined. The slow increase in the absorption coefficient at the low‐energy side of the direct gap is related to indirect transitions. The exact determination of the indirect gap is hindered by oxygen absorption bands at (4.53 ± 0.08) and (4.80 ± 0.08) eV.
Relation between Relaxation Time and Jump Frequencies for Zener Relaxation in Disordered F.C.C. Alloys
Authors: Haven Y.
Published: July 2007

The dissociation of pairs has been taken into account, in addition to a mere reorientation of pairs, to derive expressions for the relaxation times of Zener relaxation in disordered f.c.c. alloys. The results are 1/τ1 = (12 k1 + 12.74 k2) fR, 1/τ2 = (8k1 + 12.78 k2) fR for the Eg and T2g mode of relaxation, respectively. Here k1 and k2 are jump rates for non‐dissociating and dissociating atoms, respectively, and fR is a correlation factor.
Zur Theorie der kooperativen Absorption (Emission) von Licht in Kristallen
Authors: Tulub A. V. , Patzer K.
Published: July 2007

Es wird die Wahrscheinlichkeit für die Anregung von zwei Atomen durch ein Photon untersucht. Weiterhin wird die Wahrscheinlichkeit für die Energieübertragung von zwei Donatoren auf einen Akzeptor betrachtet, wobei sich die Anregungsenergien der Donatoren addieren. Durch Vergleich dieser Wahrscheinlichkeiten wird gezeigt, warum bisher die kooperative Emission experimentell nur in Anwesenheit eines Akzeptors beobachtet wurde. Der Einfluß der Kristallsymmetrie auf diese Prozesse wird berücksichtigt.
Die Magnetisierungsverteilung an der Stirnfläche zylindrischer Ferromagnetika mit Anwendungen auf die Keimbildung
Authors: Holz A.
Published: July 2007

In einer vorangehenden Arbeit [1] wurde dargelegt, daß der Ummagnetisierungsprozeß eines ferromagnetischen Zylinders an einer seiner Stirnflächen beginnt. Zur Berechnung der Magnetisierungsverteilung in der Umgebung der Stirnfläche wird ein für die numerische Rechnung geeignetes Verfahren entwickelt, das auf einer Diskretisierung des ferromagnetischen Kontinuums in geeignet gewählte Volumenelemente beruht. Für Fe werden für den Fall eines starken äußeren Magnetfeldes numerische Rechnungen durchgeführt. Sie ergeben große Radialauslenkungen der Magnetisierung für Probenradien größer als 1 μm sowie einen Vorzeichenwechsel der Radialauslenkung längs der Zylinderachse, welcher eine Erklärung für die in der Umgebung der Stirnfläche beobachteten Querbereiche sein könnte.
Optical Properties of α‐ and β‐TiCl3
Authors: Baldini G. , Pollini I. , Spinolo G.
Published: July 2007

In this paper the absorption spectra of α‐TiCl3 single crystals and α‐ and β‐TiCl3 vacuum deposited films are reported. The absorption of β‐TiCl3 films is measured from 1 up to 10 eV in the temperature range 55 to 400°K. The optical thickness of the growing film is continuously measured with interference methods. The refractive index at 7000 Å is found to be 1.85 ± 0.10. A tentative attribution of the various absorption peaks to corresponding optical transitions is made in terms of the excited states of the Ti3+ ion and of charge transfer from the Cl− ion to the Ti3+ ion.
Mössbauer Study of Hyperfine Fields in MnZn Ferritess
Authors: Cser L. , Dézsi I. , Gladkih I. , Keszthelyi L. , Kulgawczuk D. , Eissa N. A. , Sterk E.
Published: July 2007

The hyperfine field in Mn1−xZnx Fe2O4 ferrites is studied in dependence on x and temperature. A six‐nearest‐neighbours model used in evaluating the Mössbauer spectra leads to convex magnetization functions if the number of Zn nearest neighbours is > 3.
Hopping Recombination in Trigonal Selenium Single Crystals
Authors: Fuhs W. , Stuke J.
Published: July 2007

The decay of the photocurrent in trigonal selenium single crystals is investigated as a function of temperature, applied voltage, and simultaneous illumination with quenching light. At 90°K the photocurrent decays logarithmically with time. This behaviour is explained by the assumption that the recombination process is due to transitions of minority carriers, i. e. electrons, from traps to recombination centres. The decay rate is considerably enhanced when trapped minority carriers are raised to the conduction band: at higher temperature by thermal activation or at low temperature both by optical activation and by a strong electric field. Two kinds of electron traps are found, the optical activation energies of which exceed by far the thermal ones.
Stacking Faults in a Cu‐15 at% Al Alloy. I. The Short Range Order and Temperature Dependence of the Stacking Fault Energy
Authors: Tisone T. C. , Brittain J. O. , Meshii M.
Published: July 2007

An experimental study was made of the short range order (SRO) and temperature dependence of the stacking fault energy (SFE) for a Cu‐15 at% Al alloy using (110) single crystal foils. The SFE was determined using measurements form threefold nodes, intrinsicextrinsic fault pairs, and Frank triangles. Good quantitative agreement was obtained for the SFE determined form these three defects. A SRO dependence of the SFE was found by measuring the SFE form foils quenched from different annealing temperatures which are known to vary the degree of SRO [4]. A reversible temperature dependence of the SFE was found where the SFE increased with increasing temperature for both intrinsic and extrinsic faulting. The ratio of extrinsic to intrinsic fault energy was found to be 1.14 ± 0.08.
Direct Evidence for Dechanneling of 40 kV Gold Ions at Planar Defects in Silver and Gold
Authors: Schober T. , Balluffi R. W.
Published: July 2007

Thin single crystal sandwiches consisting of silver‐gold‐silver layers were prepared by epitaxial vapor deposition on (100) cleaved rocksalt. These specimens contained numerous (111) planar faults (coherent twins and stacking faults) extending through them at an angle of 54.7° with the surface. After bombardment along [100] with 40 ke V gold ions the middle gold layer was removed and examined by transmission electron microscopy. Zones free of radiation damage were found directly adjacent to the planar faults. These zones were a result of a shadowing effect caused by the defocusing of the incoming ions by the extensions of the planar defects into the upper silver layer (which were present during the bombardment). Evidence was also found for the production of excess defects directly at the planar defect surfaces in the gold layer due to dechanneling. The geometry of the blocking of [100] channels in a f.c.c. lattice by (111) planar faults is described.
Low‐Field Magnetoresistance and Magnetoconductivity in n‐Type Ge with Dislocations
Authors: van Weeren J. H. P. , Struikmans R. , Koopmans G. , Blok J.
Published: July 2007

Expression are derived for specified magnetoresistance and magneto‐conductivity coefficients for n‐type Ge with an array of parallel dislocations. The obtained equations are compared with measurements at 77°K on plastically bent n‐type Ge. From the results we conclude that the electron mobility is not reduced by the dislocations for Ndisl. < 2 × 107 cm−2. The observed anisotropies in the conductivity can be attributed to the inhomogeneous distribution of the dislocations.
Generation‐Recombination Statistics in Semiconductors‐A Model with Two Centres
Authors: Friedrich H. , Jungk G.
Published: July 2007

Equations of recombination statistics for a model with two recombination centres are studied using various approximations. Variation of the non‐equilibrium concentration caused by additional irradiation with light from the extrinsic absorption region can be explained by this model.
Phonons, Torsons, and Rotational Diffusion in Adamantane
Authors: Stockmeyer R. , Stiller H.
Published: July 2007

The results of neutron spectroscopic measurements on solid adamantane (C10H16) are compared to calculated frequency distributions for phonons, torsons and mixed modes in the adamantane lattice. The comparison suggests that rotational diffusion jumps are superimposed on librational motions (torsons) and vibrations of the molecular centres of masses (phonons).
The Theory of Low‐Field Oscillations of the Surface Impedance in Metals
Authors: Fischbeck H. J. , Mertsching J.
Published: July 2007

Magnetic surface states on cylindrical parts of the Fermi surface and their relation to volume Landau states are discussed. The scattering of the surface states by a rough surface is calculated quantum mechanically, giving the classical scattering rate in a certain limiting case. Transitions between surface states give rise to small oscillations of the surface impedance, which are calculated for arbitrary orientations of the cylinder and the magnetic field, starting with the electric field distribution in the case of anomalous skin effect. The results are compared with experimental data in indium. More elaborate numerical calculations of the transition matrix elements and the surface scattering rate are required to determine the parameters of surface scattering unambiguously.
The Micromagnetic Equations of a Superconductor
Authors: Seeger A. , Kronmüller H.
Published: July 2007

A general theory is developed for deformable superconductors containing both spontaneous strains due to the superconductivity and internal strains due to crystal defects. An intersection technique, involving five distinct states K, x′, x″, k′, and k, is employed to derive the micromagnetic equations of a superconductor (generalizations of the Ginsburg‐Landau equations) on the basis of finite strain theory.
Mechanism of Electrical Conduction in β‐FeSi2
Authors: Birkholz U. , Schelm J.
Published: July 2007

Electrical conductivity, thermoelectric power and Hall coefficient of β‐FeSi2 doped with cobalt (n‐type) or aluminium (p‐type) are measured between 100 and 1200 °K. The conductivity of n‐FeSi2 follows an exponential dependence on temperature. The temperature dependence of the thermoelectric power cannot be interpreted on the basis of conduction in a band. With the assumption that conduction in n‐FeSi2 is caused by small polarons, the mobility at room temperature is found to be μn = 0.26 cm2/Vs. The activation energy of the mobility is 0.06 eV, the density of states N = 1.2 × 1022 cm−3. The electrical properties of p‐FeSi2 can be interpreted using the band model with a hole mobility μp ≈ 2 cm2/Vs, which varies as T−1/2 in the region of extrinsic conduction. From intrinsic conduction a band gap of 0.9 to 1.0 eV is deduced. The disappearance of the thermoelectric power at high temperature is related to the semiconductor‐to‐metal transition at 1200 °K.
Effect of Electron‐Lattice Interactions on the Spin‐Paramagnetism of Metals
Authors: Saxena V. K. , Bhattacharya D. L.
Published: July 2007

The effect of electron‐static‐lattice and electron‐phonon interactions on the spin‐paramagnetism of metals is studied with a Hellmantype pseudopotential as the electron‐ion interaction potential. Numerical calculations show that the electron–static‐lattice interaction produces an enhancement of about 10% in the spin‐susceptibility of sodium. Further it is found that the electron‐phonon contribution to the spin‐susceptibility is of the order of . This confirms the result of Migdal, and Quinn and Ferrell that the spin‐susceptibility of an electron gas in a metal is unaffected by the electron‐phonon interactions to order , by means of a straightforward calculation.
Diffusion of Free Excitons in Molecular Crystals
Authors: Agranovich V. M. , Konobeev Yu. V.
Published: July 2007

A theoretical analysis of the temperature dependence of the free exciton diffusion coefficient is given. The methods of calculating the capture probability of an exciton by impurity traps are discussed in terms of the exciton mean free path, capture radius of an impurity molecule, and average separation of two impurity molecules. A comparison of the theory with the experiment is made.
Depth Distribution Measurements Using Bombardment‐Enhanced Solubility
Authors: Jech Č.
Published: July 2007

A method is described which enables thin, uniform layers to be sectioned off from the surfaces of insulators and semiconductors. It is based on the formation of bombardment‐induced disorder in a layer of definite thickness by low‐energy ion bombardment and subsequent dissolving the disordered layer in a suitable solvent. The thickness of the layer thus removed after various times and conditions of ion bombardment is determined for silicon and mica using neutron activation analysis. The method is applied for determining the depth distribution of radon decay products injected by recoil from a planar radon source into mica.
Kinematic and Dynamic Interaction Between Elementary Excitations in Ferromagnetics with Spin S = 1/2
Authors: Tošić B. S. , Žakula R. B.
Published: July 2007

The magnon creation and annihilation operators satisfying the Pauli commutation relations in a ferromagnetic with spin S = 1/2 are expressed in terms of two various types of Fermi operators. The dispersion laws for fermions are obtained by twofold diagonalization of the Hamiltonian. Furthermore, these dispersion laws are used to calculate numerically the magnetization and specific heat of the magnon system. The present results are compared with those obtained by other methods as well as with experimental results.
Fine Structure Measurements in the Energy Angular Distribution of Secondary Electrons from a (110) Face of Copper
Authors: Appelt G.
Published: July 2007

The energy angular distribution of secondary electrons from a (110) face of copper in the (010) azimuth is measured by means of a dynamical method. The plots exhibit numerous fine structure maxima. It can be shown that the maxima corresponding to all theoretically possible directions of reciprocal lattice vectors up to the 46th order may be found in every measurement; taking the whole results, maxima corresponding to directions of reciprocal lattice vectors up to the 148th order may be detected continuously. The correlation of the maxima to the crystal structure yields experimental values of the refractive index which depends on the energy of the secondary but is independent of the energy of the primary electrons. By means of this refractive index it is possible to determine the energy band of excited states above the vacuum level in the (010) direction of the wave vector, except an integration constant.