bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of Exciton States in NaI I. The Intrinsic Photoluminescence
Authors: Fontana M. P. , Blume H. , van Sciver W. J.
Published: July 2007

The efficiency and the decay time of the intrinsic photoluminescence of NaI have been investigated as a function of temperature and uv excitation energy. Upon excitation in the band‐to‐band region, the efficiency and the decay time are constant at low temperatures and decrease above 77 and 60 °K, respectively. The decrease in the decay time is not correlated to radiationless transitions occurring within the luminescent center. Upon excitation in the exciton region, the luminescence efficiency reaches a maximum at 60 °K and decreases at both higher and lower temperatures. The high temperature behavior is similar to that produced by band‐to‐band excitation. At 5 °K the luminescence efficiency for exciton excitation is negligibly small. The low temperature behavior of the luminescence is explained in terms of localized exciton states and temperature activated transitions among them.
Elektrische Leitfähigkeit und Halleffekt von mangandotiertem Germanium und der Einfluß von Wärmebehandlungen auf den Einbauzustand des Mangans
Authors: Gläser H. J. , Geist D.
Published: July 2007

Durch verschiedene Wärmebehandlungen kann der Zustand des Mangans in Germanium‐Einkristallen geändert werden. Diese Änderung beeinflußt nicht nur die Trägerkonzentration, sondern auch die Beweglichkeit. Die Ergebnisse werden durch das Verhalten des Spektrums der paramagnetischen Elektronenresonanz des substitutionell eingebauten Mangans bestätigt.
Determination of the Electron Spin–Lattice Relaxation Time T1 in the Direct Process
Authors: Pfeuffer K.
Published: July 2007

In the standard investigation methods of the spin–lattice relaxation of paramagnetic ions in crystals the measured time constant of the relaxation process is the spin–bath relaxation time Teff. If a phonon bottleneck exists, the spin–lattice relaxation time T1 does no longer equal Teff. A method is proposed for determining T1, which is still valid if a phonon bottleneck exists.
Magnetic Properties of ZrFe2 and TiFe2 within Their Homogeneity Range
Authors: Brückner W. , Perthel R. , Kleinstück K. , Schulze G. E. R.
Published: July 2007

The magnetic properties of TiFe2 and ZrFe2 are investigated within their homogeneity range in dependence on the concentration. TiFe2 is antiferromagnetic at titanium excess and at stoichiometric composition and it is ferromagnetic at iron excess. ZrFe2 is ferromagnetic throughout the whole homogeneity range. The dependences of the Curie temperatures and of the saturation magnetizations on the concentration are determined. By the present studies the discrepancies of the magnetic data of ZrFe2 and TiFe2 existing in the literature can be attributed to the existence of a homogeneity range.
Transient Effects in the Room‐Temperature F‐Colouring of NaCl Irradiated with X‐ or γ‐Rays
Authors: Sánchez C. , Agulló‐López F.
Published: July 2007

In this paper a new transient effect in the room‐temperature F‐colouring of NaCl is presented which occurs whenever a X‐ or γ‐irradiation is resumed after an interruption time where in the crystal remains in the dark. A detailed study of the characteristics of the effect is made and a relatively simple theoretical model is proposed to account for them. Essentially, the model is based on the existence of a thermally activated process consisting of the removal of free anion vacancies. The data on transient colouring permit to investigate the kinetics of that vacancy process and determine its activation energy (0.39 eV).
Study of Agglomerated Defects in Irradiated Pure Nickel by Electron Microscopy
Authors: Bourret A. , Dautreppe D.
Published: July 2007

Pure nickel foils are neutron and electron irradiated. In both cases black dots are observed by electron microscopy. After neutron irradiation at 77 °K and subsequent annealing at room temperature the larger dots are found to be interstitial Frank dislocation loops. The smaller ones (<15 Å) are vacancy agglomerates in the form of tetrahedral voids. Investigation of dose dependence and further annealing is also presented. After electron irradiation at 10 °C only interstitial Frank dislocation loops are visible for doses larger than 4 × 1019 electrons/cm2 at 2 MeV. Discussion of nucleation and agglomeration of free interstitials is presented, showing that the elastic interaction between loops plays an important role.
Instabilities and Turbulence in Semiconductors
Authors: Handel P. H.
Published: July 2007

A stability calculation shows that a special type of pinch‐like instabilities appears at potential barriers in semiconductors, as well as in ionized gases. These “magnetic barrier instabilities” produce turbulence in the plasma of current carriers. The form and the frequency‐limits of the resulting turbulence or noise‐spectrum permit an explanation of flicker noise. Furthermore the result of a calculation yielding instabilities of the thermal conduction at potential barriers in semiconductors with free terminals is discussed. Like the instabilities of the electric conduction we mentioned, they result from the usual macroscopic‐phenomenological equations, but in contrast to the magnetic ones these “thermal barrier instabilities” appear only in special conditions.
Optical Absorption due to Intrinsic Defects in CdS Single Crystals
Authors: Boyn R.
Published: July 2007

Optical absorption spectra due to intrinsic defects in CdS were measured between 0.13 and 2.5 eV, at 80 °K. The results indicate that Cd interstitials (Cdi) and Cd vacancies (Vcd) are the dominant electronically active defects, which act as double donors and double acceptors, respectively. A detailed discussion of the properties of the observed absorption bands, in particular their shape, polarization, and the effects of Cd and S heat treatment, leads to assignments to optical transitions at isolated Cdi and Vcd and at nearest‐neighbour donor‐acceptor associates between these intrinsic defects and impurity ions.
On Coherent Phonon Fusion in Quartz Transducers
Authors: Luukkala M.
Published: July 2007

The generation of the second harmonic of ultrasound in quartz crystals is studied both experimentally and theoretically in the so‐called three‐phonon interaction picture. The dependence of the intensity on the pumping amplitude agrees with the quadratic dependence in the classical picture of ultrasound.
On a New Type of Stripe Domains
Authors: Sukiennicki A.
Published: July 2007

A theoretical explanation of the new type of stripe domains recently observed in thin films obliquely evaporated is given. Parameters of this structure and conditions for its existence are calculated and compared with experimental data.
On the Lattice Dynamics of Hexagonal Structure Metals
Authors: Czachor A.
Published: July 2007

The lattice dynamics of the hexagonal close‐packed structure (h.c.p.) metals Mg, Zn, and Be are investigated assuming various first principles interionic interaction potentials. It is found that, if the ions interact via a Thomas‐Fermi potential, the Huang condition for the vanishing of the anisotropic stresses is not fulfilled, but only when assuming a c/a ratio corresponding to the ideal h.c.p. structure. One can except the same for Coulomb and Bardeen potentials, too. None of the potentials used gives a satisfactory description of the phonon dispersion relations for the mentioned metals. The need for introducing a nonradially symmetric effective interaction potential is discussed. It is observed that, for the transverse phonon branches Δ5 and Δ6, the Coulomb interaction between the ions leads to better agreement with experiment, than any of the screened Coulomb interactions investigated. The numerical calculations of the lattice sums are carried out with the help of a convergence procedure based on elementary functions.
Effect of Weak Electric Fields on the Absorption Edge in Doped Germanium
Authors: Asnin V. M. , Eristavi G. L. , Rogachev A. A.
Published: July 2007

Results of the investigation of a new effect, the great change in the absorption spectra near the direct band edge of germanium in a relatively weak electric field, are presented. The effect is assumed to be due to the screening of the Coulomb interaction by the carriers which are freed by avalanche breakdown of shallow impurities.
An Infrared Spectrophotometric Study of Vitreous Selenium Doped with Selenium Dioxide
Authors: Burley R. A.
Published: July 2007

Infrared spectrophotometric studies have shown that selenium dioxide present in vitreous elemental selenium may exist in two distinct forms, depending upon the method of preparation and other factors. Form I exhibits a simple infrared spectrum consisting of two broad bands at 925 and 630 cm−1. This form has not been described previously in the literature. It is believed to consist of individual molecules of selenium dioxide isolated in the vitreous selenium matrix. Form I gradually changes with time to form II, which exhibits a more complex spectrum, similar to that of crystalline selenium dioxide, and which has been described. The results indicate that the structure of oxygen‐bearing impurities may be as important as the total oxygen content in determining the effect of oxygen on the physical and electrical properties of selenium. The complexity of the form of oxygen present in selenium also renders impractical the accurate determination of trace amounts of oxygen by means of infrared spectrophotometry.
Dislocation Mobility in the {1122} 〈1123〉 Slip System of Zinc Single Crystals
Authors: Lavrentev F. F. , Salita O. P. , Vladimirova V. L.
Published: July 2007

Results are presented of measurements of the stress dependence of screw dislocation velocities in the {1122} 〈1123〉 slip system (pyramidal slip) of zinc single crystals. The investigations have been carried out on zinc single crystals of 99.999% purity at room temperature. The dislocation mobility has been studied within a wide range of velocities and shear stresses below and above the critical resolved shear stress. When the shear stress τ changed from 20 to 4000 p/mm2 the dislocation velocity v varied from 10−3 to 104 cm/s. A strong dependence of v on τ is observed in the stress range 20 to 100 p/mm2, which can be described by an exponential and the dislocation mobility is determined by a thermally activated mechanism. A weak linear dependence of v on τ is observed at shear stresses greatly exceeding the critical shear stress (300 to 4000 p/mm2). These results are explained in terms of a phonon viscosity mechanism. The measured drag constant is of the same order of magnitude as that calculated for the mechanism of phonon viscosity.
The Valence Bond Approximation in Crystals — Application to an Analysis of the Ultraviolet Spectrum in Quartz
Authors: Ruffa A. R.
Published: July 2007

A simple band model analogous to the tight binding approximation is presented which is applicable to valence crystals. This model is applied to an analysis of the ultraviolet reflectivity data for quartz recently obtained by Loh and Philipp. It is demonstrated that the observed peaks can be understood in terms of the elementary processes of the breaking of Si‐O bonds, the promotion and demotion of atomic states, and the interaction with the crystal of electrons freed by these processes.
Surface Layers of Triglycine Sulfate Single Crystals
Authors: Chincholkar V. S. , Unruh H.‐G.
Published: July 2007

The dielectric constant ε of triglycine sulfate has been measured along the ferroelectric axis in the vicinity of the transition temperature Tc. The thickness dependence of the maximum ε‐values can be explained by assuming two different surface layers. The outermost layer is formed during the preparation of the electrodes, whereas the second one with a thickness of the order of 1 mm can be attributed to the dielectric inhomogeneity of the crystal at Tc.
Temperature Dependence of Laser Threshold Current Density and Emission Spectra in Electron‐Beam Pumped Gallium Arsenide Lasers
Authors: Bogdankevich O. V. , Borisov N. A. , Krukova I. V. , Lavrushin B. M.
Published: July 2007

The basic temperature characteristics of electron‐beam pumped GaAs lasers are investigated for differently doped materials. Some new effects are observed, such as the presence of a gap in the temperature dependence of the photon energy at the threshold and a decrease in the threshold current density with increasing temperature in a certain range in the case of intermediate doping materials, and so on. It is shown that these effects may be related to changes in the mechanism of the laser transitions: for example, for n‐type samples at low temperatures the donor states, and at high temperatures states in the conduction band take part in the transitions. It should be noted also that the laser mechanism depends on doping.
The Low‐Temperature Thermoelectric Power and Thermal Conductivity of GeTe and of Some GeTe‐MnTe Alloys
Authors: Lewis J. E. , Rodot H. , Haen P.
Published: July 2007

A method of preparation has been developed which allows the growth of large homogeneous single phase ingots of such alloy systems as GeTe‐MnTe, GeTe‐SnTe, etc. … We have measured the thermoelectric power and the thermal conductivity of both GeTe and two alloys of the system Ge1−xMnxTe, in the temperature interval 2.5 to 110 °K, the thermoelectric measurements being extended to 350 °K. Using conventional transport theory both the lattice and the electronic contributions to these effects have been obtained. The temperature dependence of these properties was found to be of similar shape for the GeTe‐MnTe samples as for the pure GeTe, even below the known magnetic transition temperature of these samples. To explain the behaviour of the diffusion term of the thermoelectric power, however, the influence of the incomplete Mn d‐band on the electronic properties of the system must be invoked. The lattice thermoelectric power has the same temperature dependence as the phonon‐drag term in metals. From the analysis of both this component and the lattice thermal conductivity, some informations on the predominant phonon scattering mechanisms have been obtained.
Effect of Heat Treatments on GaAs Luminescence
Authors: Tuck B.
Published: July 2007

The low photon‐energy luminescence from GaAs, occurring at 1.2 eV at 77 °K has been studied under conditions of photoluminescence and cathodoluminescence. The spectral line was observed from a variety of crystals, doped both n‐ and p‐type. It was found that the emission could be induced by annealing an n‐type crystal at 1000 °C for a few minutes. Its efficiency was shown to be sensitive to Fermi level position. Evidence is also presented that the centre giving rise to the 1.2 eV line may be associated with a gallium vacancy.
On the Nature of the Colour Centres of Ruby
Authors: Arkhangelskii G. E. , Morgenshtern Z. L. , Neustrev V. B.
Published: July 2007

An investigation is made of the spectral dependence of the luminescence quantum yield ratio (η/η0) of coloured and non‐coloured ruby and of the yield (ηadd) calculated for additional absorption. It is shown that in the additional absorption (Δk) are bands of different nature. Those with ηadd = 0 are called “active”, the others, with ηadd = 0, are called “inactive”. The active absorption connected with an electron transition to the conduction band and a following recombination with R‐line radiation, is attributed to Cr2+ ions, the inactive to Cr4+ ions. Experiments of monochromatic light action on coloured ruby have confirmed this conclusion; light absorbed in the region of active bands bleaches the crystal, whereas bleaching does not occur in the region of inactive bands. The results obtained allow to suggest a level scheme of corundum with a Cr2+ centre.
Antiferromagnetic Ordering Effect on the Light Absorption Spectrum by Crystalline Oxygen
Authors: Litvinenko Yu. G. , Eremenko V. V. , Garber T. I.
Published: July 2007

The optical “double” transition spectrum of crystalline oxygen is studied in the frequency range of 15000 to 31000 cm−1 at different temperatures (5 to 27 °K) and nitrogen concentrations (0 to 40%). A sharp integral intensity decrease of the absorption bands, their shift, and broadening are found in the temperature range investigated. With the insertion of nitrogen into oxygen new absorption bands with spectral positions close to the pure oxygen band frequencies appeared in the oxygen spectrum. The results show that the “double” transitions in oxygen are considerably induced by exchange interaction. It is also shown that the O−0 band intensity of the 23 Σ → 21Δg and 23Σ → 21 Σ transition is determined by the interaction not with acoustic phonons, as it was considered before, but with magnons corresponding to the Brillouin zone boundary and having an energy equal to the exchange one gμBHE. The O−0 band of the 23Σ → 1Δg + 1Σ transition is interpreted as a pure electronic band. A consistent scheme, based on considering the exchange splitting of the 3Σ ground state of the oxygen molecules and the magnon excitation at light absorption is suggested to explain the “double” transition structures and their band behaviours at magnetic ordering.
The Temperature Dependence of Absorption of Sodium Nitrite in the Far Infrared
Authors: Vogt H. , Happ H.
Published: July 2007

The paper deals with the infrared absorption of ferroelectric NaNO2 in the wavelength range between 350 and 1100 μm. The observed temperature dependence of absorption is attributed to one‐ and multiphonon processes. Below 400 °K most of the measured isochromates can be approximately described by the relation x = A T + B T2 known from multiphonon absorption in alkali halides. In the temperature range above 400 °K one expects additional defect‐induced one‐phonon absorption, because the onset of orientational disorder disturbes the translational symmetry of the crystal lattice. It is tried to explain the anomalies occurring in some isochromates about 450 °K by opposite temperature behaviour of one‐ and multiphonon absorption. In the paraelectric phase isotherms deduced from the isochromates show selective absorption, which appears most distinctly in the ferroelectric b‐direction.
Activation Energies for Zener Relaxation in α‐AgCd
Authors: Turner T. J. , Dozier C. M. , Williams G. P.
Published: July 2007

Activation energies for Zener relaxation have been measured from 15.0 to 39.6 at% Cd in Ag with a torsion pendulum, and compared with recent diffusion data over the same range of concentrations. Over most of the range the relaxation energies are approximately 1.5 kcal/mol less than the energy of the faster diffuser; as the solubility limit is approached, however, this energy difference increases. As in earlier work, the relaxation times are approximately equal to the extrapolated mean times of stay of the faster diffuser, indicating that Zener relaxation measures the diffusion of the more mobile component of the solid solution.
The Antiferromagnetic Ordering in Uranium Monoarsenide and Monoantimonide
Authors: Leciejewicz J. , Murasik A. , Troć R.
Published: July 2007

By neutron diffraction it was found that the magnetic structure of UAs at 78°K is of the first kind (A−1) with a saturation moment of (1.93 ± 0.05) Bohr magnetons. Between 78 and 4°K there exists a point of a magnetic phase transition. At 4°K the magnetic unit cell is doubled in one direction with the moments aligned along the tetragonal unique axis. The sequence of ferromagnetic sheets which are perpendicular to the tetragonal axis, is in the order + − − +. The magnetic moment at 4°K is (2.20 ± 0.05) BM. The magnetic structure of USb both at 4 and 78°K is of the first kind. The values of the saturation magnetic moments at 4 and 78°K are (2.16 ± 0.05) and (2.08 ± 0.05) BM, respectively.
Faraday Rotation of the U2 Centre in KCl, KBr, and KI
Authors: Ingels J. , Jacobs G.
Published: July 2007

Optical density and Faraday rotation measurements for the U2 band in KCl, KBr, and KI are presented. The Faraday rotation measurements were performed at 43.1 and 48.8 kG. The results were analysed by the method of moments, for determining the spinorbit splitting of the first excited state. The computed values are Δ = − 0.234 eV for KCl, Δ = −0.179 eV for KBr, and Δ = −0.644 eV for KI. The pattern for the magnetic circular dichroism Δf(E), as computed from the Faraday rotation, is also given.
Degradation of Low‐Energy Electrons in Alkali Halides
Authors: Itoh N.
Published: July 2007

The degradation of low‐energy electrons in alkali halides is calculated using Gryzinski's cross‐section and the Monte Carlo method. The stopping power, the extrapolated range, and the degradation spectrum are obtained in the energy range of 100 to 15000 eV and compared with the results of other theoretical and experimental studies. The yield of double ionization produced by the Auger process and by the direct process is also obtained, and it is shown that the former increases as the energy of the incident electron increases, and the latter decreases as the energy increases above a certain value which is about three times the direct double ionization energy.
Quadratischer elektrooptischer Effekt (Kerr‐Effekt) in Alkalihalogeniden vom NaCl‐Typ
Authors: Haussühl S. , Hesse H.
Published: July 2007

Der quadratische elektrooptische Effekt wurde an 15 Alkalihalogeniden mit Hilfe eines dynamischen Verfahrens gemessen, mit welchem Gangunterschiede bis zu 5 × 10−8 Wellenlängen nachgewiesen werden können. Die beobachtete Anisotropie bestätigt den Tensorcharakter des Effekts. Die Konstanten liegen in der Größenordnung von 10−18 cm2/V2. Sie zeigen einen typischen Verlauf innerhalb der isotypen Reihe und eine enge Korrelation zu den piezooptischen Konstanten.
Mössbauer Study of SnCl2 and Dy(ClO4)3 in Ice
Authors: Dézsi I. , Eissa N. A. , Keszthelyi L. , Molnár B. , Nagy D. L.
Published: July 2007

Solidified solutions of SnCl2 and Dy(ClO4)3 have been investigated by means of the Mössbauer effect. In both solutions the Mössbauer pattern was observed to disappear above −90 °C. This was preceded by an appreciable broadening of the lines in the case of SnCl2.
The Effect of Dislocations on the Intensity Jumps at the Interferential Transmission of X‐Rays near the K‐Edge of Absorption in Ge
Authors: Datsenko L. I. , Skorokhod M. Ya. , Vasilkovskii A. S.
Published: July 2007

An investigation was made of the effect of dislocations on the intensity jumps i2/i1 near the K‐edge of the absorption of atoms by interference transmission of X‐rays in Ge. The intensities i2 and i1 were measured using a single‐crystal spectrometer in the case of Laue diffraction from the planes (111), (110), and (100), respectively, in the long‐ and short‐wave regions near the K‐edge of Ge. An increase of i2 and a decrease of i1 with increasing dislocation density Nd is observed in the crystal. A linear dependence is found for the logarithm of the intensity jump versus crystal thickness t. It is shown that the slope of the straight line In (i2/i1) = f(t) rises with the increase of Nd for 220 and 400 reflections. For the 111 reflection such an effect of dislocations was not observed up to Nd = 7 × 104 cm−2.
Force on Dislocations in Anisotropic Bicrystals and Half‐Spaces
Authors: Gemperlová J.
Published: July 2007

The forces acting on dislocations situated near a free, welded, and slipping boundary are examined as a function of elastic anisotropy and misorientation across the boundary. The anisotropic theory of elasticity is used. The dislocations are attracted to a free surface by a force equivalent to that due to a dislocation of opposite sign at the image point. The same force acts on dislocations near a slipping boundary for the particular case where the Burgers vector is parallel to the slipping boundary. For a welded boundary the force on a screw dislocation depends only on the crystallographic direction of the dislocation and on the direction in the second grain parallel to this. For an edge or mixed dislocation near a welded boundary as well as for a dislocation near a slipping boundary with a component of the Burgers vector normal to the boundary the complete orientation of both grains must be specified. Numerical results for several b.c.c. materials are given.
Xenon‐Vacancy Defect Clusters in Copper
Authors: Anderman A. , Gehman W. G.
Published: July 2007

A computer investigation of the stability of clusters of substitutional xenon atoms in copper shows that xenon clusters are energetically unstable in the absence of adjacent vacancies in the surrounding copper lattice. The stability of various clusters increases as the ratio of vacancies to xenon atoms increases. The efficiency of the stabilization due to the vacancies is markedly affected by the geometrical distribution of the vacancies in the xenon‐vacancy clusters.
Charge‐Transfer Excitons and Delayed Fluorescence of Anthracene
Authors: Frankevich E. L. , Rumyantsev B. M.
Published: July 2007

The paper deals with decay kinetics and the steady state intensity LSO of the delayed fluorescence of anthracene in a magnetic field (H = 3000 G); LSO being proportional to the incident light intensity I. The triplet exciton annihilation rate constant γ, which is proportional to the square of the slope of the kinetic curve γ = dL/dt, is found to decrease as the incident light intensity I increases. Under these conditions a change is observed in the fluorescence decay kinetics from the usual hyperbolic law, characteristic of triplet bimolecular annihilation, to an exponential one with a time constant t′ = 1.6 ms. A conclusion is made about the formation of an intermediate excited state (charge‐transfer (CT) excitons) after triplet‐triplet annihilation but before the delayed singlet exciton M generation. This conclusion is confirmed by the influence of a magnetic field on the delayed fluorescence steady state intensity LSO (ΔSO/LSO = −10%) and on the slope of the decay curve γeff0.5. An investigation of the CT exciton lifetime, which is determined from the delayed fluorescence exponential decay, as a function of crystal temperature and the incident light intensity seems to show that the CT exciton level in anthracene is situated between the wide and narrow conduction bands.
The Radiationless Transfer of Energy of Electronic Excitation between Impurity Molecules in Crystals
Authors: Davydov A. S.
Published: July 2007

The theory of transfer of electronic excitation energy between impurity molecules is developed without employing perturbation theory. The role of the lattice vibrations in the transfer process of the electronic excitation energy is taken into account. It is shown that the transfer time of electronic dipole excitation is proportional to the distance between molecules raised to the third power rather than to the sixth as it follows from the first‐order perturbation theory. A connection of parameters determining the transfer process of electronic excitation with the spectra of impurity absorption and luminescence is found.
Faraday Rotation and Magnetic Dichroism in RbNi(Co)F3
Authors: Pisarev R. V. , Siny I. G. , Nesterova N. N. , Smolensky G. A. , Syrnikov P. P.
Published: July 2007

The optical and magneto‐optical properties of hexagonal ferrimagnetic RbNi(Co)F3 (Co2+ content ≈ 23%, Tc = 109°K) have been studied in the region 0.28 to 12 μm. It is confirmed that this crystal may be regarded as an “easy axis” ferrimagnet. Absorption lines have been interpreted as arising from electronic transitions between crystal field levels of 3 d‐configuration of Ni2+ and Co2+. Below Tc a strong anomalous dispersion of Faraday rotation and magnetic circular dichroism was found in the absorption line regions. The origin of these effects is assumed to be associated with exchange splitting of electronic states of Ni2+ and Co2+ below Tc and with unequivalency of 4f and 2a magnetic sublattices in the hexagonal structure.
Lifetimes of Current Carriers in InP
Authors: Kovalevskaya G. G. , Slobodchikov S. V.
Published: July 2007

The lifetimes of electrons and holes in p‐ and n‐type InP are measured in the temperature range 78 to 300°K. Possible mechanisms for the capture and recombination with participation of several trapping centres: E = 0.17 eV, E = 0.04 to 0.06 eV, E = 0.10 eV, are suggested. The considerable effect of trapping at low temperatures is noted. It is found that for low‐resistivity p‐type samples the recombination centres d2 and the trapping centres f1, and for high‐resistivity samples the centres d2 and f2 play the dominant role. As result of effective trapping in n‐type as well as in p‐type InP the lifetimes of electrons and holes differ much at low temperatures.
Polariton Dispersion in Biaxial and Uniaxial Crystals
Authors: Merten L.
Published: July 2007

Complete dispersion relations of polaritons are given for biaxial and uniaxial crystals. In the limiting cases k → 0 and k → ∞ (k wave vector) very general conclusions can be drawn concerning their frequencies and directions of polarization. For uniaxial crystals the polaritons are subdivided in ordinary and extraordinary ones with orientation independent or orientation dependent frequencies, respectively. The ordinary polaritons are of transverse type whereas extraordinary are of mixed transverse‐longitudinal type for a general orientation.
Effect of Neutron Irradiation on the Martensitic Transformation in β1‐Copper‐Zinc
Authors: Hummel R. E. , Koger J. W.
Published: July 2007

Resistivity measurements were used to determine the characteristic properties of the martensitic transformation in β1‐brass (39.4 wt% Zn) before and after neutron irradiation. The doses (Φ t) varied between 5 × 1016 and 5 × 1018 neutrons/cm2 (E > 1 MeV). Neutron irradiation decreased the martensitic‐start temperature (Ms) up to 8 °C and increased the maximum rate of trasformation. Ms was further decreased when β1‐brass was annealed at 150 °C after irradiation. A small decrease in Ms was observed when unirradiated, quenched β1‐brass was annealed at 150 °C. Possible mechanisms which give rise to the inhibition of the martensitic transformation, such as dislocation pinning, are discussed.
Atomistische Berechnung der Core‐Struktur, Core‐Energie und Peierls‐Spannung einer Stufenversetzung in NaCl
Authors: Granzer F. , Wagner G. , Eisenblätter J.
Published: July 2007

Der Einfluß verschiedener elastischer Randbedingungen und Potentialansätze auf 1. das Verschiebungsfeld im Core‐Gebiet, 2. den Core‐Radius und die Core‐Energie, 3. die Peierls‐Spannung einer geraden (110), 1/2 [110]‐Stufenversetzung in NaCl wurde mit Hilfe eines Variationsverfahrens systematisch untersucht.
Electron‐Optic Investigation of the Magnetic Stray Field above Bloch Walls in Cylindric Nickel Crystals
Authors: Schwink Ch. , Schärpf O.
Published: July 2007

An electrostatic electron microscope of high magnification is developed for measuring low magnetic fields of small spatial extension. The method is applied to the investigation of the stray fields above the “convex” 71° Bloch walls of cylindric 〈110〉 Ni crystals causing the well‐known intense colloid lines. We find that these fields have dipole character and are closely related to the domain structure. The distance between the maxima of the both magnetic poles of the dipole stripe lying at the position of each convex Bloch wall varies from 4 to 10 μm. The normal field above the maxima amounts to about 25 Oe at the crystal surface. Generally, it is supposed that colloid patterns ‐ with the exception of very weak lines ‐ are due to dipole fields of the sort described.
Mechanical Interactions of Point Defects
Authors: Siems R.
Published: July 2007

The interaction of point defects, which are described by force multipoles, is treated using elasticity theory. Explicit expressions for the interaction energy are derived for elastically isotropic materials. For defects with cubic symmetry in f.c.c. metals, the lattice theory values derived for a special isotropic model (v = ∞) by Hardy and Bullough are 25% higher than the elastic theory values, both showing, however, the same orientation dependence and the same decrease with r−5. By finding not only the first (elastic) but also the second term of an asymptotic expansion of the lattice Green's function, the 25% difference is shown to be a true lattice theory effect.
On the Dynamical Behaviour of Excitons in CdS Single Crystals. I. Correlation between Intrinsic Excitonic Absorption and Emission
Authors: Voigt J. , Spiegelberg F.
Published: July 2007

The excitonic absorption and emission are investigated on the same, extremely thin (d ≈ 3 × 10−5 cm) CdS single crystals in the range 77°K to room temperature. It is found that the zero‐phonon emission line is strongly influenced by reabsorption. After a reabsorption correction of the emission data the conclusions from the absorption and emission investigations agree with respect to the exciton‐phonon interaction. There is a contribution to the halfwidths and energetic positions of the exciton lines which is proportional to a Bose factor of LO phonons with ħω1 = 38 meV. No evidence is found for polariton effects from the reabsorption correction of the emission data. It is concluded, from the temperature dependence of the total emission intensity, that a quasi‐equilibrium exists between excitons and electron‐hole pairs. The exciton ionization energy is determined to be 31.5 meV. The dependence of the total emission intensity from the excitation intensity shows the occurrence of non‐radiative recombination processes. Band shapes and intensity rations of the one‐and two‐phonon satellites in the emission are also investigated and discussed.
Mössbauer Effect in Simple Cubic Lattice with Line Defect
Authors: Celý J.
Published: July 2007

A theoretical study is made of the Mössbauer effect in simple cubic lattices with a line defect for both the atoms inside and outside the perturbed region. Numerical calculations are made of the changes in the Debye‐Waller factor for a special type of defect (with variation of the mass and force constants along a single atomic row in [001] direction) in the classical approximation together with quantum corrections. Two methods, the high‐temperature expansion and another one which is valid for arbitrary temperatures, are used. A possibility of using graphs for some estimations, especially for the dependence of the quantum correction on the distance of the absorbing atom from the line defect, is suggested.
Dechannelling Cylinder of Dislocations
Authors: Quéré Y.
Published: July 2007

A particle channelled in a crystal may be dechannelled when passing near a dislocation. This effect is simulated by an opaque cylinder dechannelling any particle hitting it. This cylinder is coaxial to the dislocation and has a diameter

E is the energy of the particle (charge Z1 e), b the Burgers vector, d the interatomic distance along the considered channel in the crystal Z2, a the screening radius, and α a number equal to 12.5 and 4.5 for screw or edge dislocations, respectively.
On the Thermodynamics and Paramagnetic Properties of Dispersed Metals
Authors: Czerwonko J.
Published: July 2007

The statistical thermodynamics of the electron gas in dispersed metals are developed. The assumptions are as follows: the one‐particle levels have the random character described by one of three possible Dyson ensembles with the homogeneous average level spacing δ. This value is of the order of the Fermi energy divided by the total number of electrons with possible surface corrections. The thermodynamical functions are explicitely calculated in two limiting cases: for kT much greater than δ and for kT much smaller than δ. In such a way we obtain the extension of Kubo's and Gorkov‐Eliashberg's results. The applicability of the present theory to transition metals is also discussed.
Röntgenographische Untersuchung des Übergangs vom Bereich I zum Bereich II der Verfestigungskurve kubisch‐flächenzentrierter Kupfer‐Gallium‐Einkristalle
Authors: Gassenmeier P. , Wilkens M.
Published: July 2007

Mittelorientierte Kupfer‐Gallium‐Einkristalle mit 2,5 bzw. 5 At% Gallium wurden im Zugversuch bei 78°K verformt. Aus den verformten Einkristallen wurden parallel zu verschiedenen kristallographischen Ebenen Oberflächen herauspräpariert und mit einem Röntgenrückstrahlverfahren abgebildet. Es wird gefunden, daß mit Beginn des Übergangs Bereich I/Bereich II Versetzungsschichten parallel zur Hauptgleitebene verstärkt auftreten. Aus Richtung und Vorzeichen der in den Versetzungsschichten enthaltenen Drehachsen wird geschlossen, daß die zum Aufbau der Schichten erforderliche Sekundärgleitung jeweils in der von äußeren Schubspannung begünstigten Richtung erfolgt und damit wohl nicht durch Versetzungsaufstauungen im Primärgleitsystem induziert wird.
Use of the Perturbation Theory in the Calculation of Adiabatic Potential
Authors: Ledovskaya E. M.
Published: July 2007

The energy of an electronic state of a complex system, consisting of a number of interacting sub‐systems is considered by perturbation theory, the interaction of sub‐systems being taken as a perturbation. The energy of a system is calculated up to the second order and the wave function up to the first order. The application of perturbation theory is justified when in the expansions in terms of nonorthogonal functions of an overcomplete set the coefficients possess the minimum property.
The Effect of Impurities on the Thermoelectric Properties of Bi, Te, and Se at Phase Transitions
Authors: Dutchak Ya. I. , Klyus I. P. , Prokhorenko V. Ya.
Published: July 2007

The thermo e.m.f. of Zn, Ga, In, Sn, and Bi doped (1 and 1.5 wt%) Bi, Te, and Se is investigated over a large temperature range using solid as well as liquid samples (for Se the amorphous state is also included). The dopants Zn, Ga, In, and Sn strongly affect the thermo e.m.f. of solid but not of liquid Bi. Liquid Te and Se are found to show semiconductor properties determined strongly by impurities, especially for Se. The change in the sign of the thermo e.m.f. of liquid Se is explained by the existence of oxygen atoms acting as acceptors.
An Account of Configuration Interactions in Group‐Theoretical Classification of Electronic States in Crystals Composed of Complexes of Bound Impurity Ions
Authors: Vonsovskii S. V. , Men A. N. , Cherepanov V. I. , Karpenko B. V. , Farberov D. S. , Nikolaev A. P. , Mitrofanov V. I. , Chufarov G. I.
Published: July 2007

A group‐theoretical classification of the states of paramagnetic impurity ions is made taking into account charge transfer. The cases of an impurity ion in a spinel crystal and the first order pair of equivalent Cr3+ ions in corundum are studied as examples. A group‐theoretical classification of the states of complexes of N impurity ions (N = 2 to 4) is given. KMg(Co)F3 is discussed as an example.
Effective Mass Approximation for Acceptor States in Silicon
Authors: Mendelson K. S. , Schultz D. R.
Published: July 2007

The effective mass equations for acceptors in silicon have been solved approximately for a large number of excited states. The variational approach used by Schechter was followed, but with more general trial functions that allow the treatment of a larger number of excited states. More recently measured valence band parameters were also used. Energies and wave functions were calculated for all of the lower excited states. Several energy levels were found between the levels treated by Schechter. The energy values obtained from the new valence band parameters do not agree as well with experiment as those obtained with the older parameters. However, the new distribution of levels does yield a better agreement between the theoretical and experimental symmetries of the excited state wave functions.
Properties of Exciton States in NaI. II. Excitonic Energy Transfer to Q and Tl Centers
Authors: Blume H. , Fontana M. P. , van Sciver W. J.
Published: July 2007

As reported in Part I, upon excitation in the region of the first excition absorption band the efficiency of the intrinsic luminescence of NaI decreases with decreasing temperature below 60 °K. This part of our article yields information about the fate of the excition generated at low temperatures: 1. Only a very small fraction of the excitons contribute to thermoluminescence. 2. The exciton state is not the excited state of an emission with a small Stokes shift ΔE ≧ 0.1 eV. 3. However, an excitonic energy transfer to Q and Tl centers takes place. The lifetime of the exciton state in a crystal doped with 1 ppm of each Q and Tl centers is τ < 5 ns at LHeT.
Phononenstruktur im Emissionsspektrum dotierter Naphthalinkristalle
Authors: Ostertag R. , Wolf H. C.
Published: July 2007

Im Emissionsspektrum dotierter Naphthalinkristalle beobachtet man bei tiefen Temperaturen charakteristische breite Mehrphononenbanden als Begleiter der scharfen Null‐Phonon‐Linien, die zu elektronisch‐vibronsichen Übergängen in den Gastmolekülen gehören. Die Phononen‐Zustandsdichte des Wirtkristalls verwendet wurden.
Magnetic Susceptibility Measurements of Mixed Transition Metal Germanides
Authors: Airoldi G. , Asdente M. , Drosi M.
Published: July 2007

Magnetic susceptibility measurements on (Fe1−xYx)1.67Ge with B82 structure, where Y is another 3d transition element, are performed in the range between room temperature and 1000°C. For all of them the magnetic susceptibility follows a Curie‐Weiss law at high temperature. The results are examined in comparison with the ones found transition metal alloys.
Ferromagnetic Behavior of Iron Alloys Containing Molybdenum, Manganese, and Tantalum
Authors: Arajs S.
Published: July 2007

The mass magnetization of iron‐rich binary iron solid solutions, containing molybdenum, manganese, and tantalum, have been studied as a function of the internal magnetic field at 298 °K. The mass spontaneous magnetizations have been determined from these data using the Belov‐Arrott‐Kouvel method. Our values of the spontaneous magnetization as a function of molybdenum or manganese concentration are in fair agreement with previous investigations of the saturation magnetization by Aldered and Sadron, respectively. The spontaneous magnetizations for iron‐tantalum alloys have been measured for the first time. These investigations indicate that, from the viewpoint of the bulk magnetization, molybdenum, manganese, and tantalum very approximately produce a simple dilution effect.
Electrical Conductance of Rubidium Nitrate
Authors: Salhotra P. P. , Subbarao E. C. , Venkateswarlu P.
Published: July 2007

Discontinuities in the plot of the logarithm of the conductance versus reciprocal absolute temperature are observed at all the four phase transformations of cooled melts of RbNO3. This behaviour is explained in terms of the crystal structure of RbNO3.
“Fanning”‐Magnetization Reversal and Exchange Stiffness
Authors: Andrä W. , Brodkorb W.
Published: July 2007

Starting from the method of Methfessel, Middelhoek, and Thomas [1] for the determination of the exchange stiffness, theoretical considerations are performed about the magnetization reversal in a ferromagnetic thin film with the easy magnetization direction in the plane of the film. The dependence of the magnetization directions on the parameters of the film on an inhomogeneous magnetic field to produce the “fanning”‐magnetization, and on an arbitrary homogenous magnetic field for the magnetization reversal is discussed. The knowledge of the deviation of the surface magnetization from the easy magnetization direction permits to determine the exchange stiffness.
The Excitation of Polarization Waves in Bound Electronic States
Authors: Hartley B. M.
Published: July 2007

The appearance of broad peaks in the electron energy loss spectra of elements in the first, second, and third long periods of the periodic table is discussed. It is shown that these peaks are similar to peaks which can be calculated by assuming absorption processes appropriate to ionization of bound states in these metals. By comparison with the calculated peaks and with the known optical constants of graphite a mode of excitation in the form of a collective polarization wave in these bound states is proposed. The possibility of deriving the optical constants of materials from their electron energy loss spectra is discussed.
Current Oscillations in GaAs under Acoustic Amplification Conditions. I. Experimental Study
Authors: Hugon P. Leroux
Published: July 2007

Current oscillations, accompanied by the propagation of a high‐field domain, have been observed in piezoelectric semiconducting GaAs. The occurrence of oscillations has been found to depend on such parameters as crystalline orientation, length of the sample, temperature, concentration, and mobility of carriers. The characteristics of the high‐field propagating domain depend to a lesser extent on these parameters.
On Majority Carrier Sweep‐Out by Trapped Space Charge in Gold‐Doped Silicon
Authors: Lemke H. , Müller G. O.
Published: July 2007

After pulsed majority carrier injection into gold‐doped p‐type Si, a decrease in conductivity occurs, which is caused by sweep‐out of free thermal carriers in the electric field of the trapped injected space charge. The step‐like recovery of conductivity (carrier concentration) is observed after a time comparable with the thermal release time of the traps. The dependence of depletion time on injection voltage or injected space charge was determined at various temperatures. The temperature dependence of injection voltages for zero depletion time reveals two regions in which different mechanisms of recovery are dominant. The results are in good agreement with a simple theory and values for the donor level of Au in Si ED = 0.315 eV and the cross section for holes \documentclass{article}\pagestyle{empty}\begin{document}$ S_{\rm p} = \frac{1}{g}2.5 \times 10^{ - 14} \,{\rm cm}^2 $\end{document} can be derived.
Space‐Charge‐Limited Currents in Vitreous Antimony Trisulfide Films
Authors: Budinas T. , Mačkus P. , Smilga A. , Viščakas J.
Published: July 2007

For vitreous antimony trisulfide films (thickness 6.4 to 16.1 μm) the steady‐state current‐voltage characteristics were measured. The current proportional to U2 d−3 are interpreted in terms of space‐charge‐limited currents (SCLC) with a single trap level. It is proved that a steep current increase at the end of the square‐law region is caused by trap filling. The values of the parameters of this trapping level calculated using two independent methods – from the temperature dependence of the reduction factor θ and from the trap‐filled limit (TFL) voltage – are in close agreement. The polarization the conduction mechanism of vitreous Sb2S3 films at lower temperatures are discussed.
Negative Magnetoresistance Anisotropy in Thin Magnetic Films
Authors: Kouritsyna E. F. , Vasilyev Yu. V.
Published: July 2007

The resistivity change of thin films of nickel and iron is investigated in planar magnetic fields above 4 kOe. After being saturated, the films exhibit negative slopes of different magnitude in the transverse and longitudinal resistivities. The observations at room temperature indicate essential thickness dependences of the Δϱ‐effect as well as of the slopes. A correlation method is used to prove it. In an attempt to give an explanation of the negative magnetoresistance anisotropy the d‐electrons have to be viewed as localized and itinerant at the same time.
Dispersion of the Refractive Indices and Birefringence of CdSxSe1−x Single Crystals
Authors: Lisitsa M. P. , Gudymenko L. F. , Malinko V. N. , Terekhova S. F.
Published: July 2007

The spectral dependence of the refractive indices and birefringence of CdSxSe1−x (including CdS and CdSe) single crystals has been investigated from the fundamental absorption edge up to the lattice vibration spectrum in the temperature interval 100 to 600 °K. In the region of v > 5000 cm−1 the measurements are carried out by the method of prism (with an absolute error for n of 5 × 10−4), for v < 5000 cm−1 by the modified interference method (with an absolute error for n of 5 × 10−3, and for Δn = ne − no of (2 to 4) × 10−5). The results are discussed.
Magnetic Anisotropy of FeNiCo Ferrites
Authors: Bryukhatov N. L. , Pakhomova N. L. , Kozlov V. A. , Potakova V. A.
Published: July 2007

This paper deals with the anisotropy induced by thermomagnetic treatment in mono crystals of Ni0.620 Co0.100 Fe Fe □0.004 O. The induced magnetic anisotropy has been studied and an explanation of this effect is proposed. For (100) and (110) planes the experimental data agree with the calculations.