The density of energy states and number of states in the zones in the case of a spectrum symmetric relative to electrons and holes are computed in a two-zone model generalized by taking into account the influence of remote zones. Numerical estimates of the density of states in the case of energies at a distance from the zone edges of approximately the width of the forbidden zone are presented, and may markedly differ from the results of Cain model; the difference in the electron concentration is less substantial.
Show AbstractThe process of multiple generation of particles in nucleus-nucleus collisions is considered within the framework of a model of independent collisions. Formulas are obtained which express the mean multiplicity of particles generated in nuclear collision in terms of the mean multiplicity of pA interactions.
Show AbstractThe state of a wave beam in an unbounded plasma which appears at the stage of wave capture and particle phase mixing is analyzed. The mean state is described by means of nonlinear kinetic, self-consistent equations, and the plasma remains a linear, dispersing medium. Equations are obtained which describe the nonlinear state of a wave beam, by means of which it is possible to obtain detailed information about the characteristics of the particular system.
Show AbstractIn the present article, isolated electromagnetic waves of appreciable amplitude excited by intense electron beams in decelerating systems are investigated. The characteristics of the wave beam are estimated by means of a self-consistent kinetic analysis of the final equilibrium state which appears as a result of nonlinear interaction of the wave beam. It is shown that the particle field is concentrated practically within the cluster. Beam reorganization as a result of the effect of longitudinal autofocusing is considered.
Show AbstractA generalization of the Nozieres-de Dominicis theory of finite temperature for x-ray spectra at the absorption edge in metals is considered. The formalism of Green's time functions in the case of finite temperatures under the assumption that heat energy is small, is used. It is found that the temperature effect leads to broadening of the spectra lines in the shape of the Gaussian function.
Show AbstractIn the present article, the imaginary part of the optical potential is studied, in light of contributions from an inelastic channel along with excitation of cooperative levels. The computation of Im Vopt is carried out under the assumptions of the Tamm-Dankov and random phase approximations. It is shown that the contribution of the lower cooperative levels (which yield the basic contribution to Im Vopt)is much greater in the random phase approximation than is the Tamm-Dankov approximation. Particular computations are performed for ${16}^$O and ${40}^Ca nuclei.
Show AbstractThe angular distribution for the strongest gamma quanta from the reaction ${209}^$Bi (n, n'y) relative to a beam of fast reactor neutrons are measured. The size of mixtures of multiples in the gamma transitions between the ${209}^$Bi levels are determined.
Show AbstractA convenient method of computing the minimal measurement errors of quantum magnitudes is considered. An example using this, method is presented.
Show AbstractIn the present article a method is proposed for computing the motion of electrons in a three-electrode gun used in a cyclotron-resonance maser. The region of motion is divided into four stages, in each of which the expressions for the strengths of the electrical and magnetic fields are different. Based on a solution of the kinetic equation, the g-factor (ratios of the electron's rotational energy to its translational energy) are computed for different voltages at the electrodes and different strengths of the magnetic field in the interaction region. The results obtained give us a basis for selecting an optimal mode of operation of a particular cyclotron-resonance maser model.
Show AbstractResults are presented from an experimental study of the propagation of acoustic waves in a medium with gas bubbles. It is noted that the dispersive properties of the medium predominate over the nonlinear properties. Autofocussing of an acoustic beam is observed, in which the frequency of the acoustic wave is much greater than the bubble frequency.
Show AbstractWaveguide propagation of underwater sound under the conditions of distance- variable sea depth is accompanied by horizontal refraction of normal waves and quasi modes. Upon their entry into the nonwaveguide zone, vertical refraction leading to emission of sound waves into the subjacent half-space occurs. This phenomenon is studied in the article.
Show AbstractThe sf and sd exchange constants as well as the effective mass of carriers for Gd$_{x}$Y$_{1-x}$Fe$_{3}$ types of compounds are determined on the basis of the theory of indirect exchange and experimental values of hyperfine fields, the Curie temperature, and the resistivity. It is shown that agreement with experiment may be improved if it is supposed that exchange reactions in these complexes are realized not only by means of conductivity electrons, but also by means of d-type collective electrons.
Show AbstractMeasurements of the magnetocaloric effect and degree of magnetization are performed using samples of the system of rare-earth terbium-hadolinium alloys in fields up to 15 kOe in strength in the temperature range 77-350°K. The Curie temperatures of the alloys are determined. In the alloy Tb$_{0,94}$ Gd$_{0,06}$ antiferromagnetic order domains are found. A spin reorientation type of phase transition is observed in a magnetic field applied along the hard magnetization axis in the Curie temperature domain. The experimental results lead us to suppose that the polar diagram of anisotropy energy at low temperatures has additional extrema in alloys containing considerable amounts of gadolinium.
Show AbstractThe effect of an electrostatic field on internal friction and the defect in Young's modulus in the kilohertz range of frequencies is studied by means of two- and three-component resonance oscillators. It is estab- lished that in the range of amplitudes 10$^{-6}$ - 10$^{-4}$, the electrostatic field affects internal friction and the defect of Young's modulus. The height of the internal friction maxima observed in this range of deformation amplitudes increases under the influence of the electrostatic field, the maxima shift into the region of lower deformation amplitudes, and other maxima appear which are not present in the absence of the electrostatic field. The effect of the electrostatic field on the defect in Young's modulus manifests Itself in an increase in the absolute size of the defect as well as in a variation in the course of the dependence of the defect of Young's modulus on time and deformation amplitude. From an analysis of the internal friction and defect results, it is concluded that an electrostatic field leads to a growth in the amplitude of the oscillations of the dislocation segments and an increase in the number of active dislocations contributing to internal friction.
Show AbstractTwo recombination channels are found on a real Si surface, yielding comparable contributions to the rate of surface recombination. These channels are associated with two types of recombination centers, the first of which corresponds with the discrete level located near the middle of the forbidden Si zone, and the second of which with levels continuously distributed throughout the forbidden zone. The first type of recombination center appears upon localization of water molecules near definite defects at the Si-oxide interface, and the second type of center, upon the removal of the SiOF$_{2}$ group oxide in the process of different thermal and chemical treatments. It is shown that the first type of recombination center is twice as effective in recombination than the first type.
Show AbstractThe magnetic anisotropy of five monocrystals in the yttrium iron-garnet system Y$3_x$Sm$_x$Fe$_5$E$_12$, where x = 0.0, 0.01%, 0.1%, 0.2%, and 0.5% is studied by means of ferromagnetic resonance. At temperatures from 10 to 90°C, the experimental values of К vary with temperature as 1/T$^{3}$. It is proposed that in this temperature region, the crystalline field acting on the Sm$^{3+}$ ions is basically cubic in structure. For a compound with x = 0.2%, the strength of the exchange field of approximately 47.6°K is found at a temperature of approximately 15°K acting from the Fe$^{3+}$ ions to the Sm$^{3+}$ ions. In a single-ion approximation at 0°K, the first and second theoretical anisotropy constants are computed, and are found to be in satisfactory agreement with experimentally found values of K1 and K2. It is concluded that anisotropy of dilute samarium garnets is basically single-ion in nature.
Show AbstractA method is described for measuring the velocity field in separated flow based on the use of a movable-electrode electron tube [mechanotron] as the velocity transducer. The profiles of the horizontal components of the mean velocity measured by means of a DIZA hot-wire anemometer adopted as standard device and by means of an anemometer with sensing element in the form of a mechanotron are compared under the conditions of nonseparated flow. It is shown that the hot-wire anemometer technique is inappropriate for measuring velocity fields in separated flow.
Show AbstractIn the present paper, the relation between irreversible magnetic properties of natural magnetite polycrystals and the frequency of a magnetic field in the range of frequencies 50-10$^{5}$ Hz is studied. An amplification of the degree of magnetization with an increase in the frequency of the magnetizing field, beginning with frequencies on the order of several hundred hertz, is observed for all the types of remanent magnetization studied (normal, Ideal, and natural). The resulting effect is attributed to the influence of a magnetic-diffusion type barrier on the magnetic structure of the samples.
Show AbstractA description of a technique and the physical characteristics of a spectrometer for recording electrons with energies Ee in the range 0.04-3.0 MeV and protons with Ep in the range 0.5-3.0 MeV over several energy intervals in the earth's magnetosphere using satellite-borne apparatus is presented. Electrons and protons are recorded by means of an improved telescope specially adapted for magnetosphere measurements consisting of four semiconductor detectors as well as gas-discharge counters.
Show AbstractThe present article is devoted to an experimental study of centimetric wind waves generated in currents. A dependence between the characteristics of the distribution functions of the wave amplitudes and the wind and current speed is shown. A hydrodynamic contrast coefficient which describes the variation of the mean wave heights and wavelengths with the variable current speed is introduced, and it is shown that this coefficient is independent of wind speed. New dimensionless magnitudes of the phase velocity of the waves and their frequency are proposed.
Show AbstractThe influence of bivalent impurities on microhardness and yield strength is studied using highly purified samples of NaCl. An attempt is made to divide the hardness contributions due to electrical interactions of dislocations and individual vacancies and elastic interaction with dipole impurities.
Show AbstractIt is experimentally established that a sinusoidal wave in a medium with third-order nonlinearity is transformed into a wave with secondorder nonlinearity. Results are presented from a computation of the variation in the wave spectrum before and after the formation of a discontinuity.
Show AbstractThe use of the Wilson-Fisher renorm-group method shows that there exists a phase transition in the nonlinear fermion model.
Show AbstractAn expression is obtained for the radiant intensity of a collisionfree cold plasma. This radiation is attributed to the action of external and collective fields. The radiant intensity of a stationary relativistic electronic beam propagating parallel to a uniform magnetic field is found.
Show AbstractThe К$_{π^{0}}$ distribution in interactions between nucleons with mean energies of about 5 TeV and nuclei of atomic carbon is obtained by means of controlled nuclear photoemulsions. The result is compared to highenergy accelerator data.
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