bluuebunny/crossref_metadata_2025_split huggingface dataset:
Excitonic emission in cadmium telluride
Authors: Taguchi T. , Shirafuji J. , Inuishi Y. 
Published: July 2007

AbstractThe photoluminescent properties of free and bound excitons in high‐purity p‐ and n‐type CdTe single crystals are investigated in detail in connection with the dependence on excitation intensity, temperature, impurity‐doping, and uniaxial stress. Intense free‐exciton emission is observed in the single crystals grown from solutions and vapor epitaxial methods. From the thermal dissociation processes and the analysis on the basis of the effective mass argument developed by Sharma and Rodriguez and by Hopfield, an assignment of exciton emission lines is tried.
Crystal dynamics of silver bromide at 80 and 295 K
Authors: Bührer W. 
Published: July 2007

AbstractThe dispersion relation for the normal modes of vibration in AgBr have been determined at 80 and 295 K along symmetry directions. The neutron inelastic scattering experiments have been performed on a triple axis spectrometer at the “Diorit” reactor. The phonon frequencies show a strong temperature dependence. The dispersion curves can be well fitted by an eleven‐parameter model with deformable electronic shells of the silver ions.
On the theory of optical absorption in narrow‐gap disordered semiconductors
Authors: Fedirko V. A. 
Published: July 2007

AbstractThe interband absorption coefficient in disordered semiconductors is calculated for the frequency range below the threshold value (“optical tail”). A model with three doubly degenerate bands is considered containing one conduction band and two valence bands with very different effective masses. Disorder is taken into account in terms of a random field present in the sample including both smooth and Coulomb fields. The energy gap is assumed to be comparable with the r.m.s. value of the random field, so the scheme of the interacting adjacent bands is used. Expressions for the absorption coefficient are obtained for various relations between the parameters of the system and the photon energy. Theoretical results are compared with some experimental data available.
Microwave‐optical double resonance and magnetic circular dichroism of photochromic centres in CaF2:Ce
Authors: Komarov A. V. , Ryabchenko S. M. , Terletsrii O. V. 
Published: July 2007

AbstractThe dispersion of magnetic circular dichroism (MCD) and Faraday rotation (FR) for Ce3+ photochromic centres in CaF2 is measured at T = 1.7 °K. The optical technique of EPR detection is used to separate the paramagnetic and diamagnetic contributions to the MCD. From the phenomenological analysis of the MCD paramagnetic and diamagnetic parts is found that the optical transition to the lowest excited state is split into at least three components. This splitting as well as the presence of the paramagnetic contribution into the MCD are assumed to be due to an exchange interaction of 4f electron of Ce3+ with the photochromic centre, other electrons involving spin‐orbital interaction.
Tunnel spectroscopy of thin bismuth films
Authors: Lutskii V. N. , Nikitin N. E. , Pinsker T. N. , Volkov V. A. , Elinson M. I. 
Published: July 2007

AbstractA quantitative study is made of the band structure in Bi by tunnel spectroscopy of size‐quantized films. The positions of quantum energy levels are determined for a wide range of film thickness (700 to 3200 Å). On the basis of the two‐band model the electron energy spectrum in size‐quantized bismuth films is calculated. From the comparison of the experimental results with the theory the energy gap and the effective mass at the extremum of the conduction band in bulk Bi are determined. The dispersion law of charge carriers is defined by these parameters.
Strain‐modulated electron spin resonance spectra of 3d5 ions in ZnSe
Authors: Henning J. C. M. , Boef J. H. Den 
Published: July 2007

AbstractFlexural‐strain‐modulated ESR spectra of Mn2+ and Fe3+ in ZnSe are reported. A study of the relative phases of the fine structure lines and of the angular dependence of the SMESR amplitudes reveals that first‐harmonic SMESR signals arise mainly through modulation of the off‐diagonal elements (g̃xz + g̃zx) of the tensor g̃. A slight amount of A‐modulation is present in ZnSe:Mn2+. Weak quadrature signals are observed in ZnSe:Fe3+; they are attributed to anelastic losses. A second‐harmonic SMESR signal is also present. It arises from second‐order line shifts. The angular dependence of the second‐harmonic signal reveals that, apart from (g̃xz + g̃zx), g̃zz‐modulation also plays some part in producing these signals. The component g̃xx normal to the bending plane, however, is not modulated.
The theory of Raman scattering by surface polaritons
Authors: Strizhevskii V. L. , Yashkir Yu. N. 
Published: July 2007

AbstractThe fluctuation–dissipation theory of spontaneous Raman scattering (RS) by surface polaritons (SP) is carried out. The appearance of scattering emission is treated as the result of mixing of the pump emission and the fluctuating surface electromagnetic field. A calculation is made of the surface electromagnetic fluctuations near the interface between the two dissipative media and in the absorbing layer surrounded by transparent dielectrics. Expressions are found and analysed describing the frequency–angular distribution of the scattering emission intensity in the layer, taking into account the interference of SP localized near different surfaces (and near the interface of two absorbing media). The RS intensities are expressed by the phenomenological parameters of the media. It is also shown that the RS intensity decreases essentially with increasing scattering angle θ (when the scattering frequency approaches the frequency of the surface phonon) due to the increasing localization of SP. Various essential physical features of the phenomenon are analysed in detail: scattering line shape and its angular dependence; the Fermi resonance of SP and its display in the RS; mixing of SP of different media and RS by appearing mixed modes; RS by SP connected genetically with the linear medium which borders with the transparent nonlinear medium; evolution of RS in a layer by decreasing its thickness, and others.
Calculation of the spin‐disorder resistivity in disordered magnetic alloys
Authors: Goedsche F. , Richter R. , Richter A. 
Published: July 2007

AbstractThe CPA‐conductivity theory is applied to the s–d exchange model to calculate the spin contribution to the electrical resistivity of disordered binary alloys containing two kinds of localized spins. The second‐order resistivity is expressed in terms of alloy magnetization, spin‐pair correlation functions, atomic spin difference, and mean spin value. Striking deviations from a Nordheim‐like behaviour of the spin‐disorder residual resistivity are obtained, if the magnitude of the atomic spins depends on alloy composition and local environment.
The probability of bi‐exciton formation in crystals
Authors: Borbrysheva A. I. , Vybornov V. I. 
Published: July 2007

AbstractIn first order of perturbation theory the probability of binding of two excitons into a bi‐exciton accompanied by light emission and caused by exciton–exciton collisions is calculated. Firstly the case is considered where two excitons of 1s‐type and n‐p‐type form a bi‐exciton in the ground state consisting of two excitons of 1s‐type. The binding is accompanied by light emission. The luminescence begins with a threshold and the luminescence band has the form of a sharp asymmetrical peak. The exciton–exciton collisions lead to the binding of two excitons of 1s‐type with no internal excitation. Numerical estimations of the processes under consideration are made for a set of crystals.
Stress absorption spectra of V3+ in α‐Al2O3: Jahn‐Teller effect in the 3T2 state
Authors: Champagnon B. , Duval E. , Louat R. 
Published: July 2007

AbstractStudy under stress of 3T2 state of the V3+ ion in corundum (α‐Al2O3) was performed at 77 K. Absorption spectra are made on 3A2(3T1)→3T2 zero‐phonon lines and on the 3A2(3T1) → → 1A1 sharp line. Under uniaxial stress, the degeneracy of vibronic levels is removed: curves show the shifts and splittings of 3A2 → 3T1 and 3A2 → 1A1 transitions as a function of the applied pressure. The strain interaction with 3T2 state only is deduced. The stress spectra cannot be quantitatively explained without taking into account a large S15* local elastic compliance. The local deformation around the V3+ ion is similar to this one around the Cr3+ or Co3+ ion. Studying the 3A2 → 3T2 band by the method of moments a coupling between the V3+ ion and a breathing mode A1 is found. Results of measurements cannot be interpreted by a Jahn‐Teller effect with only the pure tetragonal modes.
Third‐order contribution to the energy and the elastic constants of simple metals
Authors: Benckert S. 
Published: July 2007

AbstractThe energy of a metal is usually calculated by second‐order perturbation theory in the pseudopotential. It is, however, also possible to calculate the third‐order contribution. This contribution is calculated to the energy and the elastic constants of Al and Na using two different types of local model potentials in order to see how the choice of the potential will influence the magnitude of the third‐order contributions.
Order parameters of the phase transition in bismuth titanate
Authors: Holakovský J. 
Published: July 2007

AbstractIt is shown that the phase transition in bismuth titanate (at 675 °C) cannot be caused by the onset of parameters belonging to an irreducible representation. The parameters of the transition are divided into two sets; one leading to the symmetry B2cb, the other being responsible for the onset of the polarisation Pc. The former set of parameters is found and is shown to belong to a reducible representation.
Cyclotron resonance in plastically deformed germanium
Authors: Rusiniak L. 
Published: July 2007

AbstractMeasurements are made on samples of n‐type germanium with resistivities of about 30 Ωcm subjected to plastic deformation about the [100] axis in the microwave X‐band in the temperature range from 1.7 to 4.2 °K. Results are given of the dependence of relaxation time and carrier lifetime on temperature and dislocation density. The effective mass of carriers was found to be affected also by dislocations. The experimental results are interpreted assuming deformation and Coulomb potentials and taking into account Morrison's theory.
Lineshape of the biexciton luminescence in CuCl
Authors: Ostertag E. , Levy R. , Grun J. B. 
Published: July 2007

AbstractA comparison has been made between the experimentally observed spectral lineshape of the luminescence due to the recombination of excitonic molecules in CuCl at 4.2 K and a theoretical calculation involving transitions from the biexciton ground state to the longitudinal and transverse excitonic states. A new value of the binding energy of the excitonic molecule in its ground state is deduced and compared with theoretical evaluations.
Optical Absorption Spectra of Co2+ Ion in KCl and NaCl Crystals
Authors: Nasu T. 
Published: July 2007

AbstractOptical absorption spectra of Co2+ ion in KCl and NaCl crystals were measured in the region of energies from 4000 to 60000 cm−1. Temperature dependences of the spectra were also measured from 80 to 810 K for KClCo and from 80 to 650 K for NaClCo. The assignment of transitions concerned with absorption bands and the crystal field acting on the Co2+ ion in these crystals were discussed on the basis of the analysis of the intensity of absorption bands and the temperature dependence of the spectra.
Multiphonon Processes of the 4T1g(I) Absorption in RbMnF3
Authors: Heumüller R. , Gebhardt W. , Von Der Osten W. 
Published: July 2007

AbstractThe one‐phonon spectrum K1(ω) is calculated from the 4T1g(I) absorption in RbMnF3, using the method of generating function. In the temperature range of T ≦ 35K the coupling strength S(T) obtained with K1(ω) is in good agreement with directly measured values. S (T) is then used to derive the contribution of hot band processes to the intensity of exciton—magnon transitions at temperatures T > 35 K. We conclude from the temperature variation of the line width of the magnetic dipole transitions that exciton—magnon processes dominate when the exciton decays.
Resonant Raman Scattering in Amorphous As2S3
Authors: Razzetti C. , Fontana M. P. 
Published: July 2007

AbstractResonant Raman spectra are presented taken over the whole absorption edge of amorphous As2S3. Results indicate that 1. the electron vibration coupling is the same over all the electron states sampled; 2. band resonance effects are absent, and, rather, resonance is manifested by a monotonic increase of the scattered intensity with increasing exciting energy.
Two‐Phonon Infrared Absorption in CdSexTe1−x Mixed Crystals
Authors: Górska M. , Grad J. , Nazarewicz W. 
Published: July 2007

AbstractThe transmission spectra of CdSexTe1−x(0 ≦ x ≦ 1) mixed crystals have been measured in the spectral range 250 to 400 cm−1 at room temperature. Eleven absorption bands are observed and ascribed to particular two‐phonon combinations. The composition dependence of short‐wavelength optical phonon frequencies (from the edge of the Brillouin zone) is determined.
Optical Charge Transfer Spectra and EPR Spectra of Cr2+(d4) and Cr1+ (d5) in CdTe
Authors: Cieplak M. Z. , Godlewski M. , Baranowski J. M. 
Published: July 2007

AbstractBy EPR experiments is shown that two charge states of chromium impurity are present in CdTe:Cr. The Cr2+(d4) state has an acceptor character and can accept an additional electron into the d‐shell. The energy required to change the charge state of Cr2+(d4) into Cr1+(d5) by transferring one electron from the valence band is about 1.2 to 1.3 eV. The photosensitive EPR spectrum due to Cr1+(d5) shows that the observed intense exponential absorption tail is due to this charge transfer process. The shape of the exponential tail is also investigated. It is suggested that the exponential character of the absorption tail is due to the presence of a Jahn‐Teller effect in the ground state of Cr2+(d4).
The Grüneisen Constant and the Thermal Expansion Coefficient of Crystals with Defects
Authors: Litzman O. 
Published: July 2007

AbstractThe Green's function method to evaluate the frequency sums Σ f(λi) of crystals with defects is generalized to the calculation of the sums Σ f(λi) (δλi/δα). The deduced formulae are used for the calculation of the Grüneisen constant and the heat expansion coefficient of the linear chain with isolated defects.
The Spatial Dispersion Effects in CdS Crystals and Their Temperature Dependence
Authors: Brodin M. S. , Davydova N. A. , Strashnikova M. I. 
Published: July 2007

AbstractThe dispersion of the refractive index of a CdS crystal in the region of its main exciton bands is experimentally investigated at temperatures ranging from 4 to 80 °K. From the change of the birefringence pattern in the region of the lowest state, three specific temperature intervals are revealed. The data obtained show good agreement with the predicted temperature change of the normal wave parameters for media with the spatial dispersion; 1) in the low‐temperature region (T < 15 °K) in different regions of the absorption band either one or the second normal wave is dominating: 2) in the region of intermediate temperatures including the “critical” temperature T0 predicted by the theory (25 to 55 °K), both waves being comparable in intensity within the absorption band halfwidth; 3) in the high‐temperature region (T > 55 °K) one wave dominates all along with the dispersion of the classical character.
Calcul de la largeur des bandes d'absorption optique du rubis excité
Authors: Brunstein S. H. , Tsukerblat B. S. 
Published: July 2007

AbstractLa méthode des moments se généralise pour des bandes optiques provenant de transitions vers des niveaux électroniques quasi‐dégénérés. L'interaction Jahn‐Teller est supposée forte et l'on ne peut pas décomposer la bande optique en sous‐bandes élémentaires. On utilise cette théorie pour analyser les bandes multiphonons d'absorption optique du rubis. On montre que l'effet Jahn‐Teller donne une contribution essentielle à l'élargissement des bandes optiques; on fait une estimation numbérique des demi‐largeur, laquelle est en bon accord avec l'expérience.
Optical Absorption of MnI2
Authors: Van Erk W. , Haas C. 
Published: July 2007

AbstractThe absorption spectra of single crystals of MnI2 in the region 10000 to 30000 cm−1 are reported. At low temperature, 5 K, several of the observed absorption bands show well‐resolved vibronic fine structure. The absorption bands are assigned to electronic transitions of the d electrons of the manganese ion. From the spectra the values of the ligand field splitting 10Dq = 6400 cm−1 and the Racah parameters B = 640 cm−1, C = 3136 cm−1 are calculated. The results are compared with data for MnCl2 and MnBr2, and are discussed in terms of the covalency in the manganese halides.
Electrons in a Well Potential: Density of States, Surface Energy, and Phase Rule for Wave Functions
Authors: Paasch G. , Wonn H. 
Published: July 2007

AbstractFor the problem of electrons in a well potential as a model of a metal with surfaces, exact expressions are derived for the density of states, the surface energy, and for the sum rule for the phases of the wave functions. Incorrect derivations and errors of previous publications are pointed out. The connection between the phase rule and the surface energy is discussed.
Magnetic Properties of Iron and Cobalt in a Combined Model of Itinerant Electrons and Localized Spins
Authors: Sakoh M. , Edwards D. M. 
Published: July 2007

AbstractThe temperature variations of the spontaneous magnetization and spin paramagnetic susceptibility are calculated numerically, using molecular field theory, for the combined model of localized spins and itinerant electrons proposed by Edwards for some 3d transition metals. A simple parabolic band is assumed for the itinerant electrons and results are given for those values of the effective mass and exchange parameters which give the best fit to the observed properties of iron and cobalt. A reasonable description of the magnetic properties of b.c.c. iron is obtained and the calculated curves have none of the instability against small changes in values of parameters which is characteristic of pure Stoner theory applied to iron and cobalt. Agreement with the observed temperature dependence of the susceptibility of cobalt could not be obtained and a more sophisticated theory may be required.
Far UV Photoemission Density of States of CuNi Alloys
Authors: Shevchik N. J. , Penchina C. M. 
Published: July 2007

AbstractThe photoemission density of states of CuNi alloys deposited by cosputtering have been measured for hv = 40.8 eV. In contrast to previously reported measurements, the new results of superior resolution (0.3eV) are free of structure due to emission of the photoelectron into the unfilled states and are in even better agreement with the CPA calculations.
Effect of an External Electric Field on Phase Transitions of Order‐Disorder Crystals
Authors: Merten L. , Andrade P. Da R. , Borstel G. 
Published: July 2007

AbstractRecently a model theory was given by the authors for the coupling of long optical phonons and polaritons with a Debye‐Mason relaxation in order‐disorder crystals. This theory is extended to the case of applying an external electric field to the crystal. It is shown that the effective field entering into the dielectric function can be determined by an iteration method. As the relation between the effective field and the external field is known, the (complex) frequencies of polaritons, phonons, and relaxations can be calculated as functions of the external field. Numerical evaluations shall be given elsewhere.
Positronenannihilation in Ionenkristallen. II. Nachweis eines Positronium‐ähnlichen Zustandes in KCl
Authors: Brümmer O. , Brauer G. , Andrejtscheff V. , Käbler L. 
Published: July 2007

AbstractDie Benutzung eines Ge(Li)‐Detektors bei Positronenlebensdauermessungen an KCl‐Einkristallen gestattet es, zusätzlich die Dopplerverbreiterung der 2γ‐Annihilationsstrah‐lung zu messen. Es wird gezeigt, daß die Dopplerverbreiterung der Annihilationslinie von der Lebensdauer des Positrons abhängig ist. Die vorgelegten Messungen stützen die Hypothese der Bildung eines Positronium‐ähnlichen Zustandes in ungefärbten Alkalihalogeniden.
Shubnikov‐de Haas Effect and Energy Relaxation of Hot Carriers in p‐Type Tellurium at 4.2 K
Authors: Kahlert H. 
Published: July 2007

AbstractThe influence of electric fields on the amplitude of the Shubnikov‐de Haas (SdH) oscillations of p‐type tellurium has been studied for the configuration j ⊥ B and the trigonal c‐axis oriented perpendicular to the magnetic field B and to the current direction. From a comparison of the temperature dependence of the amplitudes of the ohmic SdH data and the electric‐field dependence of the amplitudes at 4.2 K the relation between applied electric field and resulting hole temperature is deduced. The measured energy loss rate of the holes to the lattice is compared with calculated values assuming scattering by acoustic and polar optical phonons. Piezoelectric interaction is responsible for the energy transfer below 6 K. An estimation of the contribution of deformation‐potential scattering allows to derive an approximate value for the valence‐band deformation potential constant EV ≈︁ 1.2 eV. Above 6 K emission of polar optical phonons becomes the dominant energy dissipation mechanism.
Electroreflectance Spectra of Heavily Doped Semiconductors. Field Inhomogeneity in the Low‐Field Limit
Authors: Humlíček J. , Lukeš F. 
Published: July 2007

AbstractThe influence of the electric field inhomogeneity on the electrorefleetance (ER) spectra has been included into the theory in the low‐field limit by means of the corrected Seraphin coefficients. One typical example of the ER spectra of heavily doped Ge (n‐type samples with donor concentration ND = 9 × 1017 cm−8) in the range of E1 and E1 + Δ1 transitions proves that the lineshape of the ER spectra may well be expressed by the microscopic model verified earlier for pure Ge with additional inclusion of the field inhomogeneity.
An Explanation for the Plateau in the Thermal Conductivity of Non‐Crystalline Solids
Authors: Zaitlin M. P. , Anderson A. C. 
Published: July 2007

AbstractThe tunnelling‐states model is applied to the thermal conductivity of non‐crystalline materials. It is shown that the presence of a quadratic term in the energy dependence of the density of tunneling states, as implied by specific heat and ultrasonic measurements, can give rise near 10 K to the plateau in the thermal conductivity which is characteristic of amorphous solids.
A Hydrodynamic Model of the Optical Generation of Bulk Plasma Waves
Authors: Boakdman A. D. , Parker M. R. 
Published: July 2007

AbstractThe possibility of using a hydrodynamic model of plasma wave generation in solids is investigated. The simplicity of the approach is in sharp contrast to earlier theoretical investigations based on an elaborate kinetic theory. The basic equations presented here apply to metals or semiconductors and an extension which includes the means of studying the influence of a magnetic field is provided. A thorough discussion of the boundary conditions at a dielectric–conductor/semiconductor interface is given and some numerical comparisons with published experimental data are included.
On the Theory of Conductivity of an Electronic Gas with Anisotropic Effective Mass in Quantizing Magnetic Fields
Authors: Bakanskii P. I. , Demidenko L. S. , Korolyuk S. L. , Samoilovich A. G. 
Published: July 2007

AbstractThe anisotropic impurity scattering of current carriers has been studied in quantizing magnetic fields for n‐Ge type semiconductors. General expressions for the conductivity for the cases of nondegenerate and degenerate electronic gas were obtained. The formulae for the mobility in the quantum limit for these two cases were analysed and a physical interpretation of the obtained results is given.