Interaction of electromagnetic waves with nonlinear substance layer under conditions of electron paramagnetic resonance in millimeter waves

Trancated equations have been obtained by the Green's functions method for a slowly varying amplitude of a transverse magnetic field component in a paramagnetic layer under conditions of the electron paramagnetic resonance (EPR). A magnetic susceptibiliti of the substence has been found from the Bloch equation for a homogeneously line breadth of the EPR. In a stationary case a solution of a nonlinear boundary-value problem is redused to a solution of two boundary problems for amplitude and phase equations. It is shown that unstable regimes of the electrodynamic system under inves tigation are possible.Electrodynamic characteristics of a nonlinear resonator of the Fabry-Pero type filled with a saturated paramagnetic medium have been analyzed numerically in a non-stationery case.     

On the linear and nonlinear characteristics of electrostatic solitary waves propagating in magnetized electron-positron-ion plasmas

Both linear and nonlinear propagation of electrostatic solitary waves (ESWs) in magnetized electron-positron-ion (e-p-i) plasmas are analyzed. The electrons and positrons are assumed to be dynamic, whereas positively charged ions are considered stationary. Using the reductive perturbation method, a Zakharov-Kuznetsov (ZK) equation is derived and exact soliton solutions are presented. It is found that both compressive and rarefactive ESWs can propagate. The conditions of transitions from compressive to rarefactive ESWs are specified. The nature of these electrostatic solitary waves structures which depends on the magnetic field, the obliqueness, the ion-to-electron number density ratio, and the positron-to-electron temperature ratio, are discussed.     

Bunching mechanism and kinetic analysis of the relativistic electron beam in centrifugal electrostatic focusing system

This paper proposes an azimuthal bunching-mechanism of a relativistic electron beam with circular orbits in the centrifugal electrostatic focusing system (CEFS). A kinetic theory is given which is in principal agreement with the proposed bunching-mechanism. A new proposal is presented that the electron beam is obliquely injected into CEFS.     

级联χ(2)过程产生高量值高阶非线性相移

基于位相失配三倍频(Δk≠0)转换,构建了产生高阶非线性相移的χ(2)级联非线性过程.此过程不涉及三阶等其他非线性效应,仅表现为纯的五阶非线性,所感应的非线性相移正比于I2.进一步的数值计算研究表明χ(2)级联五阶非线性相移不仅符号可控,而且具有丰富的饱和特性,其量值远高于χ(2)级联三阶非线性相移.     

The nonlinear theory of slow-wave electron cyclotron masers with inclusion of the beam velocity spread

The nonlinear theory of slow-wave electron cyclotron masers (ECM) with an initially straight electron beam is developed. The evolution equation of the nonlinear beam electron energy is derived. The numerical studies of the slow-wave ECM efficiency with inclusion of Gaussian beam velocity spread are presented. It is shown that the velocity spread reduces the interaction efficiency.     

Modulational instability of electron-acoustic waves in a plasma with a q-nonextensive electron velocity distribution

The amplitude modulation of electron-acoustic waves (EAWs) propagating in space plasmas whose constituents are inertial cold electrons, hot nonextensive q-distributed electrons, and stationary ions is presented theoretically. The nonlinear Schrödinger equation (NLSE) which governs the modulational instability of the EAWs is obtained using reductive perturbation method (RPM). The presence of the hot nonextensive q-distributed electrons is shown to influence the modulational instability of the waves. Further, the nondimensional parameter α=ne0/nc0, which is the equilibrium density ratio of the hot to cold electron component, is shown to play a vital role in the formation of both bright and dark solitons.     

Laser-based linear and nonlinear guided elastic waves at surfaces (2D) and wedges (1D)

The characteristic features and applications of linear and nonlinear guided elastic waves propagating along surfaces (2D) and wedges (1D) are discussed. Laser-based excitation, detection, or contact-free analysis of these guided waves with pump–probe methods are reviewed. Determination of material parameters by broadband surface acoustic waves (SAWs) and other applications in nondestructive evaluation (NDE) are considered. The realization of nonlinear SAWs in the form of solitary waves and as shock waves, used for the determination of the fracture strength, is described. The unique properties of dispersion-free wedge waves (WWs) propagating along homogeneous wedges and of dispersive wedge waves observed in the presence of wedge modifications such as tip truncation or coatings are outlined. Theoretical and experimental results on nonlinear wedge waves in isotropic and anisotropic solids are presented.     

Asymmetric interaction of blast waves and shock waves with a body flying at supersonic velocity

The problems of asymmetric interaction of a blunt wedge traveling at supersonic velocity with a cylindrical blast wave from a point explosion and with a plane shock wave are investigated by numerical simulation. The evolution of the interaction flow is analyzed, and data are obtained on how the structure of the shock layer changes. Zh. Tekh. Fiz. 69, 15–19 (May 1999)     

Adsorption of CO on W(001) by high resolution electron spectroscopy

The vibrational modes induced by CO on W(001) at temperatures ? 350 K are detected by means of electron energy loss spectroscopy with resolution in the 6–7 meV range. Two β adsorption regimes are identified depending on coverage. Heating at various increasing temperatures reveals coverage dependant irreversible surface structure modifications. The β spectra after adsorption or desorption are discussed in terms of the usual questions of multiple β states, dissociation, and reconstruction. The α₁ and α₂ states are detected both by their WC and CO frequencies. A small signal is assigned to a new a-state, named α₃, which may explain some thermal desorption results.     

High resolution transmission electron microscopy (HRTEM) and image analysis of uPVC thin films

The current model for the fine scale microstructure of unplasticized PVC (uPVC) has been built up using various quantitative techniques, such aa wide and small angle X-ray diffraction. The use of transmission electron microscopy (TEM) as a more qualitative technique has been previously attempted (Meyer et al., 1978), revealing only amorphous detail on the scale of the expected crystallinity. For this study, a combination of high resolution TEM (HRTEM) and digital image processing techniques was utilized in order to verify the ‘micro-domain’ model proposed by Summers (1981). The techniques utilized here are particularly applicable in examining the fine-scale texture of oriented polymers.     

Experimental determination of energy resolution and transmission characteristics of an electrostatic toroidal spectrometer adapted to a standard scanning electron microscope

The main characteristics of sectorial toroidal energy analyzer for a new electrostatic electron spectrometer adapted to a standard scanning electron microscope are defined and determined experimentally. These transfer characteristics, i.e. intensity-energy response and transmission functions, energy resolution and coupling constant, are needed for spectrometer calibration, registration and energy correction of measured backscattered electron spectra and microtomographic analysis of multilayered structures. The spectrometer response to a monoenergetic primary electron beam and to a continuous energy distribution is discussed. Detector response functions for energy independent and linear energy dependent detectors are considered. For aperture slits of the spectrometer which allow reasonable electron intensities at the detector an energy resolution of about 2.5% is obtained.     

Identification of surface vibrations on clean and oxygen covered Pt(111) surfaces with high resolution electron energy loss spectroscopy (EELS)

Clean and oxygen covered {111} recrystallized Pt surfaces were studied by EELS after surface preparation at 150≤T≤165OK. The clean surface shows Stokes as well as anti-Stokes lines of surface phonons at ±195^?1. Adsorption of small amounts of (<10^?2 monolayers) of O₂ or H₂ leads to substrate-derived phonon losses at ±380cm^?1. Oxygen exposure at different pressures, times and temperatures leads to atomic and/or molecular adsorption as well as oxide-related features which have been identified by EELS.     

Kadomstev-Petviashvili (KP) equation in warm dusty plasma with variable dust charge,two-temperature ion and nonthermal electron

In this work, the propagation of nonlinear waves in warm dusty plasmas with variable dust charge, two-temperature ion and nonthermal electron is studied. By using the reductive perturbation theory, the Kadomstev-Petviashvili (KP) equation is derived. The energy of the soliton and the linear dispersion relation are obtained. The effects of variable dust charge on the energy of soliton and the angular frequency of linear wave are also discussed.     

Coupled waves of linear velocity,angular velocity,and temperature in a liquid with internal rotation

Equations of motion for a locally nonequilibrium liquid with internal rotation are derived, and the thermospin effect is considered. It is demonstrated that high-frequency transverse coupled waves of linear velocity, angular velocity of internal rotation, and temperature may propagate a liquid with internal rotation. A dispersion relation and a frequency dependence of the damping ratio are deduced. Comparison between theoretical and experimental values of the transverse sound velocity dispersion shows their satisfactory agreement. Low-frequency transverse waves do not penetrate into the liquid: they decay over a distance on the order of the wavelength. It is shown that frequencies and their corresponding wavenumbers exist in a liquid with internal rotation at which either waves do not decay or a phase shift in the skin layer is absent. It is found that the excitation spectrum may contain a cutoff frequency or an energy gap due to interaction between the linear and angular velocity fields. The dispersion and damping ratio for the coupled waves near synchronism points, where uncoupled waves resonantly interact with each other, are determined.     

Linear and nonlinear vibrations and waves in optical or acoustic superlattices (photonic or phonon crystals)

A model of a dielectric or an elastic superlattice is proposed which describes quite simply the frequency spectrum of electromagnetic or acoustic waves. The frequency band spectrum of a one-dimensional lattice consists of minibands, which narrow down with increasing frequency (so that the forbidden bands in the spectrum broaden with increasing frequency). An elementary analysis of the spectrum of a one-dimensional lattice reveals the presence of many forbidden frequency bands in this case as well. It is shown that dynamic equations for superlattices can be generalized to the nonlinear case, leading to equations of the type of the nonlinear Schrödinger equation for the lattice. Soliton excitations are described and the particle-like dynamics of solitons is demonstrated. Local vibrations near point defects of different complexity in superlattices are studied and graphically illustrated. The existence of Bloch oscillations of a wave packet in a superlattice in a homogeneous external field is discussed.     

Effect of the group velocity mismatch and dispersion of nonlinear susceptibility on the modulation instability of electromagnetic waves in a medium with quadratic nonlinearity

Modulation instability of continuous plane waves of the pump beams and the second harmonic that are described by the set of equations for the process of second-harmonic generation with allowance made for the dispersion of nonlinear susceptibility is considered. The case of type I phase matching is analyzed. In the regions of anomalous and normal group velocity dispersion, the instability increments are determined as functions of the frequency and the wave numbers of perturbations. It was found that the difference in the group velocities of the interacting waves exerts the most substantial effect on the evolution of the modulation instability.