bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractIn 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

AbstractPure 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

AbstractA 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

AbstractOptical 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

AbstractThe 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 the Lattice Dynamics of Hexagonal Structure Metals
Authors: Czachor A. 
Published: July 2007

AbstractThe 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

AbstractResults 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

AbstractInfrared 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

AbstractResults 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractAn 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

AbstractThe 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

AbstractThe 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

AbstractActivation 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

AbstractBy 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

AbstractOptical 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

AbstractThe 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

AbstractDer 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

AbstractSolidified 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

AbstractAn 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractThe 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.