Dynamics of acoustoelectromagnetic solitons as a manifestation of higher nonlinearity

The acoustoelectromagnetic interaction is examined in a regime where three mechanisms must be taken into account simultaneously: photoelasticity, quadratic photoelasticity, and elastic nonlinearity. It is shown that beyond the critical conditions, acoustic solitary waves are formed at harmonic and subharmonic frequencies in a crystal. Including damping and nonideal reflection at the boundaries does not lead to the establishment of any sort of stationary state: a soliton spatial-temporal dynamic develops. Fiz. Tverd. Tela (St. Petersburg) 39, 1101–1104 (June 1997)     

Energetics of an adiabatically-loaded excited anharmonic oscillator

The dependence of the energy characteristics on an adiabatically slowly increasing external force is determined analytically for an anharmonic oscillator. The analytical results are confirmed by a numerical calculation. The nature of the force dependences of the energy characteristics are determined and discussed. Fiz. Tverd. Tela (St. Petersburg) 39, 153–157 (January 1997)     

Existence regions of regimes with anomalously high rates of plasma generation in grid plasma switch elements

Results are presented from a systematic investigation of the conditions under which anomalously high rates of plasma generation are observed in the anode region of a low-voltage Knudsen arc in grid plasma switch elements. The phenomenon develops over a wide range of currents and switched voltages under conditions for which the plasma density in the cathode-grid region is noticeably higher than the density in the anode region. and its onset is characterized by a pronounced pressure threshold of ∼2×10⁻² Torr. The results are analyzed from the standpoint of the possible mechanisms for anomalous plasma generation — collisional nonresonance diffusion of electrons in velocity space, leading to enrichment of the distribution function in fast particles, and the collapse of Langmuir waves in the gap at the high energies of the beam produced when the wires of the grid are bridged by the quenching pulse and and the current is blocked. Zh. Tekh. Fiz. 67, 15–21 (June 1997)     

Characteristics of nonlinear reflection of radiation associated with waverfront reversal by a surface

The dependence of the nonlinear reflection coefficient R of a mirror with a wavefront reversing surface on the intensity I of the reference wave is analyzed in terms of a phenomenological model of a medium having a nonlinear Fresnel reflection amplitude coefficient φ. Substantial differences are revealed for media having different signs of the nonlinearity coefficient β=(dφ/dI). It is shown that R is related to the magnitude D of the dynamic range of the wavefront reversing mirror by the expression RD=Q_s' where Q_s is a parameter which defines the “quality” of the nonlinear medium. Far-Eastern State Academy of Communications. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 68–70, August, 1997.     

Propagation of magnetostatic waves in unsaturated ferrite films with a strip domain structure

The propagation of surface and volume magnetostatic waves in unsaturated films of yttrium iron garnet is studied experimentally for the case when the wavelength greatly exceeds the domain width, while the domain width is comparable to the film thickness. The characteristics of these waves are examined for symmetric linear, asymmetric linear, and symmetric zigzag strip domain structures in the films. These characteristics cannot be explained by a theory based on averaging the magnetization over all the domains. Zh. éksp. Teor. Fiz. 111, 1016–1031 (March 1997)     

Electron-stimulated desorption of potassium and cesium atoms from an oxidized molybdenum surface

The yield and energy distributions of potassium and cesium atoms emitted in electron-stimulated desorption (ESD) from a molybdenum surface, oxidized to different extent and maintained at 300 K, have been measured by the time-of-flight technique with a surface ionization detector. The ESD threshold for potassium and cesium atoms lies around 25 eV, irrespective of molybdenum oxidation state. In the case of molybdenum coated by an oxygen monolayer, secondary thresholds at ∼40 and ∼70 eV have been observed, as well as atomic energy distribution tailing down to very low energies. The most probable kinetic energies of the atoms are a few tenths of one eV. The results are explained within a model involving Auger neutralization of the adsorbed alkali metal ions after the filling of the 2s O, 4s Mo, and 4p Mo core holes. The possibility of ESD of a neutral species as a result of oxide-cation core-level ionization has been demonstrated for the first time. Fiz. Tverd. Tela (St. Petersburg) 39, 758–761 (April 1997)     

Colossal magnetoresistance of the Sm1−x SrxMnO3 system

The results of investigating the temperature dependence of the resistivity, the differential magnetic susceptibility, and the magnetoresistance of a partially substituted perovskite Sm_1−x Sr_xMnO₃ (x=0.16–0.4) are presented. Colossal intrinsic magnetoresistance, reaching 90% in an external magnetic field of 30 kOe, is discovered in the compound with x=0.30 at 77 K. Fiz. Tverd. Tela (St. Petersburg) 39, 1831–1832 (October 1997)     

Structure studies on porous titanium nickelide made by high-temperature self-propagating synthesis

Structure studies are reported on martensite transformations in porous TiNi alloy made by high-temperatures self-propagating synthesis. The transformations occur over a large temperature range and are incomplete. The structure data are used in reconstructing the heat release during the transition, where it is shown that it is determined by the superposition of martensite transformations occurring locally at various temperatures. Tomsk State Architectural and Building Academy. Kuznetsov Siberian Technical Physics Institute, Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 20–24, January, 1997.     

Fast electrons generation by RF and random fields near the antenna I. One dimensional model and regular fields

Test particle motion and acceleration has been explored in strong radio frequency (RF) fields, for which quasilinear ponderomotive force approximation is not valid. By nonlinear acceleration in spatially varying wave amplitude of RF travelling wave, electrons may be accelerated to time averaged velocities significantly larger than the RF wave phase velocity, and than the boundary plasma thermal velocity, in RF fields of several Volts per centimeter at wave frequency of 7 MHz. It is also demonstrated that even weak spatial gradients, much weaker than those expected in experiments, of the RF wave field amplitude, have significant consequences for the particle motion. Estimates are presented of the total energy transferred from the near antenna RF field to the plasma due to the nonlinear electron acceleration effects.