Electromagnetic absorption of acoustic-wave packets in metals

Damping of quasimonochromatic sound-wave packets in metals caused by the electromagnetic interaction of lattice vibrations with resonant current carriers is studied. It is assumed that the acoustic wavelength λ is much shorter than the electron mean free path length l but much longer than the characteristic damping depth σ of an electromagnetic wave in metals under anomalous-skin-effect conditions. It is also assumed that the transit time of a resonant particle through the region of field nonuniformity (∼λ) is shorter than the electronic relaxation time , where is the characteristic velocity of the resonant electrons). The distribution of the potential of the eddy electromagnetic field accompanying an acoustic radiopulse with a prescribed shape is found by solving the kinetic equation and Maxwell’s equations. The force exerted on the lattice by the resonant electrons is investigated, and the equation from the theory of elasticity that describes the evolution of a sound wave is solved. It is shown that a weak damping (of the order of the small parameter a) at the extrema of the deformation on the pulse edges as well as the appearance of high-frequency precursors near the pulse boundaries are characterisic for the evolution of a powerful transverse radiopulse. Such precursors were observed earlier by Fil’ et al., as components of a noise burst arising on the leading edge of a powerful transverse radiopulse propagating in ultrapure gallium. Fiz. Tverd. Tela (St. Petersburg) 40, 966–973 (June 1998)     

On the stability of acoustic waves propagating in a nonstationary moving medium

We analyze the stability of acoustic waves in a medium moving with a time-variable velocity. An instability criterion for these waves is obtained and analyzed for the weak modulation of medium velocity. The harmonics that emerge during the propagation under parametric resonance are shown to have an additional frequency shift.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 9, pp. 1087–1090, September, 1996.This work was supported by the Russian Foundation for Fundamental Research under Projects 95-02-05001 (G. I. Grigor'ev and V. V. Tamoikin) and 96-05-64277 (O. N. Savina).     

Theorie der optimalen Fokussierung für die direkte Erzeugung höherer optischer Harmonischer

Theory of Optimum Focusing for Direct Higher Optical Harmonics Generation Optimum focusing conditions for Gaussian beams for direct higher harmonics generation are derived neglecting the pump-wave depletion. The conditions for optimum focusing are obtained numerically and in the limits of weak and strong focusing analytically. The results show that at optimum conditions strong focusing is favourable. The power of the m-th harmonics for m > 3 is proportional to focusing parameter, L medium length, b confocal parameter of the pump wave). Numerical results are given for odd and even (up to the seventh) harmonics.     

Generation of high-frequency oscillations by electromagnetic shock wave on transmission lines on the basis of multilayer heterostructures

The possibility of the direct effective transformation of a videopulse into a radiopulse with high filling frequency (of the order of 100÷300 GHz) because of evolution of an electromagnetic shock wave structure on dispersive transmission lines with nonlinear components on the basis of multilayer heterostuctures (MLHS) with hysteretic (asymmetric MLHS) and single-valued functional (symmetric MLHS) capacitance — voltage characteristics has been investigated. The requirements on the MLHS and dispersion characteristics for effective generation of the train of oscillations are discussed.     

Longitudinal Wave Propagation in Dielectric Waveguide Array

Based on the established rigorous theory for two-dimensionally periodic (2DP) medium, Longitudinal propagation in Dielectric Waveguide Array (DWA) was analyzed in detail. Firstly, given longitudinal wave vector (k _z), Brillouin dispersion relations between transversal wave vectors were analyzed. Interactions between space harmonics were also studied. Secondly, on condition that transversal wave vector k _x equaled k _y, dispersion relations between longitudinal and transversal wave vectors were analyzed in detail. Because of interactions between space harmonics increasingly getting stronger with k _z or modulation coefficients increasing, stop-bands could be distinctly displayed and thus longitudinal propagation in DWA could be comprehensively analyzed. The applications about longitudinal propagation in DWA were also discussed.     

Half-Integer Harmonics Generation in Laser-Produced Plasma

Half integer (3/2ω₀, 1/2ω₀) harmonics generation under oblique incidence of the pump-wave on the spatially inhomogeneous plasma is theoretically investigated. Harmonics generation is connected with the two-plasmon convective instability excitation near the quarter-critical density. Harmonics spectra and intensities depend essentially on the pump wave polarization. In particular, significant harmonics spectra broadening arises under the p-polarized pump wave.     

Refractive indices of biaxial crystals evaluated from the refractive indices ellipsoid equation

The expressions of the refractive indices corresponding wave vector k(θ,) are given by using coordinate transformations for the refractive indices ellipsoid equation of biaxial crystals. The refractive index expression of the wave, whose velocity is slower, is given by

and that of the wave, whose velocity is faster, is given by

     

Effect of the nonuniformity of the radio-frequency field of the sensor of an NQR detector of explosives on the signal intensity and the possibility of its compensation

The intensities of ¹⁴ N NQR signals have been calculated in relation to the amplitude of the initiating radiofrequency (RF) field of the radiopulse, the pulse duration, and the detuning. It is discussed whether it is possible to compensate the decrease in intensity of signals from some regions of an explosive which is in a nonuniform RF field by varying the detuning and the duration of the initiating pulse.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 105–107, October, 2004.     

Theory of wiggler superradiance from an extended electron bunch under the group synchronism condition

Superradiance (SR) from an electron bunch moving in a waveguide and oscillating in the field of helical wiggler is analysed for the specific group synchronism regime which occurs when the electron translational velocity coincides with the wave group velocity. In the comoving reference frame such a regime corresponds to emission at a quasi cutoff frequency. Both linear and nonlinear analysis demonstrate the advantages of the group synchronism regime for wiggler SR. Detuning from this regime leads to a fast drop in both the gain of the instability and peak power of the SR pulse.     

非线性柱形涂层复合介质有效的直流-交流电响应

利用摄动展开方法, 研究了由圆柱形带涂层杂质随机嵌入基质所形成的非线性复合介质在外加 的带有不同频率和振幅的混合电场E₀ + E₁ sinωt+E₃ sin3ωt作用下有效的直流-交流电响应, 分别推导了复合介质在杂质核、涂层及基质区域的电势分布, 并在低杂质浓度下给出了复合介质有效的非线性响应及它们之间的关系. 关键词： 非线性柱形涂层复合介质 有效的非线性响应 外加交直流电场     

Soliton solutions and interactions of the Zakharov-Kuznetsov equation in the electron-positron-ion plasmas

Analytically investigated in this paper is the Zakharov-Kuznetsov equation which describes the propagation of the electrostatic excitations in the electron-positron-ion plasmas. By means of the Hirota method and symbolic computation, the bilinear form for the Zakharov-Kuznetsov equation is derived, and then the N-soliton solution is constructed. Parametric analysis is carried out in order to illustrate that the soliton amplitude and width are affected by the phase velocity, ion-to-electron density ratio, rotation frequency and cyclotron frequency. Propagation characteristics and interaction behaviors of the solitons are also discussed through the graphical analysis. The effects of the nonlinearity A, dispersion B and disturbed wave velocity C on the amplitude and velocity of the solitons are derived. First, the amplitude is proportional to the nonlinearity A and inversely proportional to dispersion B. Second, the velocity increases as the dispersion B increases. Third, the velocity increases as the disturbed wave velocity C (4B > C) increases; the velocity decreases as the disturbed wave velocity C (4B < C) increases.     

高功率微波在等离子体填充波导中的谐波产生

采用等离子体流体理论，研究了高功率微波在等离子体填充波导中的谐波产生，导出了非线性波动方程. 对二次谐波产生进行了数值计算与分析. 理论分析和数值计算表明，高功率微波将在等离子体填充波导中激发起谐波，TE_0n模式与TM_0n模式的基波都将激发起TM类型的谐波. 关键词： 高功率微波 谐波产生 等离子体填充波导     

Nonlinear non-spherical oscillations of gas bubble under a periodic variation of ambient liquid pressure

A mathematical model is constructed for the bubble dynamics, in which the interphase surface variation is presented in the form of a series in spherical harmonics, and the equations are written with the accuracy up to the squared amplitude of the distortion of the spherical shape of the bubble. In the oscillation regimes close to periodic sonoluminescence of a single bubble in a standing acoustic wave, the character of air bubble oscillations in water was studied depending on the bubble initial radius and the amplitude of the liquid pressure variation. It was found that non-spherical oscillations of bounded amplitude can take place outside the region of linearly stable spherical oscillations. Both the oscillations with a period equal to one or several periods of the liquid pressure variation and aperiodic oscillations are observed. It is shown that neglecting the distortions in the form of spherical harmonics with large numbers (i > 3) may lead to a change of oscillation regimes. The influence of distortions on the bubble surface shape for the harmonics with i > 8 is insignificant.     

A note on Lorentz transformations and simultaneity in classical physics and special relativity

Since early models of wave propagation in both stationary and moving media during the nineteenth century, the Lorentz transformation (LT) has played a key role in describing characteristic wave phenomena, e.g., the Doppler shift effect. In these models LT connects two different events generated by wave propagations, as observed in two reference systems and the synchronism is absolute. In relativistic physics LT implements the relativity principle. As a consequence, it connects two space-time event coordinates that both correspond to the same physical event and “absolute synchronization” is not allowed. The relativistic interpretation started from Einstein’s early criticism of the notion of “simultaneity” and Minkowski’s invariance of the space-time interval. In this paper, the two different roles of LT, i.e., in classical wave propagation theories and in relativistic physics, are discussed. Einstein’s early criticism is also re-examined with respect to LT in view of its significance for the notion of simultaneity. Indeed, that early criticism is found to be defective. Our analysis is also useful for general readers in view of its impact on modern speculations about the existence of a preferred system of reference Σ, where light propagation is isotropic, and related implications.

     

Suppression of the radiation limit through autoresonant acceleration of charged particles by an electrostatic field

We consider the autoresonant motion of a charged particle in the field of a transverse electromagnetic wave propagating with the speed of light along a stationary homogeneous magnetic field with allowance for radiative friction. It is shown that the loss of wave-particle synchronism due to radiative friction can be suppressed by an external electrostatic field that is parallel to the magnetic field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 4, pp. 458–463, April, 1996.     

Effective response in nonlinear spherical coated composites under external AC and DC electric field

By using the perturbation method, effective nonlinear direct current (DC) and alternating current (AC) responses of nonlinear composites with spherical coated inclusions randomly embedded in a host medium are studied under the action of external electric field E_a =E₀ +E₁ sin ωt+E₃ sin 3ωt with different amplitudes and frequencies. The local potentials of composites at all harmonics are given in the inclusion particles and the host regions. All effective nonlinear responses to composites and the relationship between the effective nonlinear responses at all harmonics are also deduced for the spherical coated inclusions in a dilute limit.     

Theory of group synchronism in free-electron waveguide lasers fed a sequence of short electron pulses

A theory of free-electron lasers fed a sequence of short electron pulses is developed. It is assumed that the group velocity of the electromagnetic pulse that develops in the cavity is the same as the translational velocity of the particles, and the repetition period of the electron pulses equals the transit time of the electromagnetic radiation in the cavity. Under these conditions of group synchronism, the principal factors governing the feasibility of establishing a stationary pulsed lasing regime are found to be the dispersive spread of the electromagnetic pulse and the channeling properties of an electron bunch. The conditions for self-excitation are found, and the characteristics of the stationary lasing regimes are determined assuming that the cavity has a high Q and using a parabolic equation for the evolution of the electromagnetic pulse shape. Zh. Tekh. Fiz. 69, 78–83 (February 1999)     

Generating magnetic field pulses in the development of an explosive Alfvén wave instability in a flow-plasma system

The excitation of Alfvén radiation is studied when an explosive instability is developed in a heated gyrotropic plasma penetrated by a monovelocity flow of ionized gas. It is shown that magnetic field pulses are generated in the plasma under certain conditions. The amplitudes of the Alfvén wave harmonics are found and the conditions for stabilization of the explosion due to the nonlinear absorption associated with weakly damped Alfvén wave harmonics are specified.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 8, pp. 1001–1006, August, 1996.This work was supported in part by the Russian Foundation for Fundamental Research under Grant No. 95-02-05255.     

FTIR Spectroelectrochemical Investigation of the trans-[Ru(NO)(dimethylglyoximate)2Cl] Complex: Vibrational Characterization of the NO+/0 and RuIII/II Redox Couples

Abstract

This paper deals with the spectroelectrochemical characterization of the Ru^III/II and N0^+/0 oxidation states of the trans-[Ru(NO)(dmgH)₂Cl] complex (dmgH = dimethylglyoximate ion). The cyclic voltammograms of the complex in acetonitrile solution exhibited a reversible wave at -0.09 V versus SHE, and two less intense waves at 1.19 and 1.41 V. Visible-UV spectra were recorded at -0.4 and 1.5 V, however, the absorption bands collapsed into a single tail, providing little information on the redox states involved. In contrast, in the FTIR measurements at -0.4 V, the v(NO) peak shifted from 1878 to 1855cm^?1, without changing the vibrational peaks of the dmgH ligand, indicating an electrochemical process involving the NO^+/0 redox couple. At 1.5 V, the changes in the vibrational peaks of the NO and dig lagans indicated a redox process associated with the Ru^III/II redox'couple. The existence of an open and a cyclic hydrogen bridged configuration was proposed, in order to explain the occurrence of two electrochemical waves at positive potentials.     

Formation of a chaotic layer of nonlinear resonance by a two-frequency perturbation

A new effect [V. V. Vecheslavov, Zh. éksp. Teor. Fiz. 109, 2208 (1996) (JETP 82, 1190 (1996)]—the appearance of low-frequency secondary harmonics in the separatrix mapping of a system—is discussed in detail for the example of a pendulum with a two-frequency perturbation. It is shown that there exist regions of values of the perturbation parameters where these harmonics make the main contribution to the formation of the chaotic layer of the fundamental resonance. The results of analytical and numerical determinations of the amplitudes of the secondary harmonics are compared. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 12, 989–994 (25 June 1996)