Том 26, № 4 (2018)

The contactless transfer of an angular momentum to a liquid layer using a scanning laser beam has been experimentally investigated. This effect is observed for a glassy carbon target placed in water and irradiated by a pulsed laser beam, scanning the target along a closed trajectory. The target rotates in the same direction as the laser beam if the water layer is thin and in the opposite direction in the case of thick water layer. The possibility of transferring an angular momentum to liquid in the absence of target is demonstrated. The effect observed is interpreted as the result of joint action of convective flows and thermocapillary convection, which are induced in the liquid by laser heating.

A continuum description of the explosive boiling of a thin water film on a heated gold substrate is proposed based on previous molecular dynamics calculations. It is shown that the continuum model in use provides under certain conditions agreement (with an error of about 10%) with the molecular dynamics results on the heating rate of a film contacting a substrate and the dynamics of film removal after explosive boiling.

The optical transmission (OT) spectra of Yb:LaSc₃(BO₃)₄ and Yb:LuYSiO₅ laser crystals have been analyzed before and after irradiation from a ⁶⁰Co source with doses up to 45 Mrad. The OT spectra of the Yb:LuYSiO₅ crystal are found to be the same (within the measurement error) before and after irradiation. The irradiation of the 10 at.%Yb:LaSc₃(BO₃)₄ crystal significantly changes its OT spectra in a wide spectral range (330 to 700 nm). A 975-nm laser based on a previously irradiated 4 at.%Yb:LuYSiO₅ crystal has exhibited a differential efficiency of 23% under diode pumping. The up-conversion luminescence spectra in the visible range of the crystals under study have been explained.

The stimulated low-frequency Raman scattering at acoustic vibrations of elastic inclusions in a liquid heterogeneous medium placed in an external open optical cavity has been investigated. The amplitudes of stationary field oscillations in the cavity at the frequencies of the excitation and the first Stokes component are found within a two-dimensional model. The specific features of the oscillation in dependence of the parameters of the cavity and Raman-active medium have been studied based on the simulation results.

The excitation of an aqueous solution of uranyl chloride by a 410-nm semiconductor LED and 266- and 448-nm lasers is found to induce intense photoluminescence: several bands in the blue-green spectral range (494 to 565 nm). Upon excitation of uranyl chloride aqueous solution by a 468-nm LED, the photoluminescence spectrum is a relatively narrow strong band peaking at 508 nm, which was interpreted as the transition from spontaneous photoluminescence to superluminescence. A lasing scheme (similar to that for dye lasers) has been proposed.

We numerically solve the coupled-nonlinear two-dimensional Dirac equations that describe a virtual spin-1/2 system with cubic nonlinearity.We find that this set of equations supports only oscillatory solutions in the non-relativistic limit and families of discrete localized solutions in the relativistic limit. Each family of the localized solutions is characterized by a constant central amplitude value. Each solution within a family is characterized by a number of nodes and a discrete energy eigenvalue, which is bounded by the rest mass of the particle. We study the effect of different parameters on the localized solutions.

Consideration is given to the research status and prospects for development of plasma relativistic microwave electronics as a basis for plasma masers. Possible applications are determined for plasma masers as high-power sources of microwave pulses. Design features of masers and their radiation characteristics are considered with a view to the type of device: self-oscillator, external signal amplifier, or noise amplifier.

The propagation of microwaves in the frequency range from 8.5 to 12GHz and acoustic radiation in the frequency range from 8.5 to 14 kHz in the same 2D periodic crystal formed by cylindrical spiral coils has been investigated. The frequency ranges in which the effective refractive index n_ef of the crystal is close to zero are found. In these ranges, microwaves are collimated and concentrated in a narrow lobe with an FWHM of about 9◦. Focusing of divergent microwave and acoustic beams by a flat periodic structure has been observed in the frequency range where the effective refractive index of this structure is negative.

Hydrodynamic properties of hot dense plasma bunch have been studied in terms of their application to the problem of inertial confinement fusion. The two-temperature hydrodynamic equations taking into account the electron heat conduction and kinetics of the charge composition are presented. The following model problems are considered: expansion of a plasma bunch in a vacuum, compression of the plasma by shock waves, interaction of the plasma bunch with a laser radiation and a beam of heavy ions. The some problems arising in the problem of inertial confinement fusion are analyzed on the basis of the developed numerical methods.

Limiting dependences determining the attenuation regularities (related to an increase in distance) of sound pressure and orthogonal components of vibration velocity vector in the regions of interference maxima of signals formed in a Pekeris waveguide by multipoles of different orders, have been obtained and numerically analyzed.

In the current communication, the problem of plane wave diffraction by a conductible plate of finite length in the presence of cold plasma is investigated. The boundary-value problem corresponding to this model is formulated by Fourier transform which then leads to the Wiener−Hopf equation. The resulting equation has been solved by the Wiener−Hopf procedure in a standard way. The separated field (diffracted field) is analyzed in an anisotropic medium using asymptotic expansion and modified stationary phase method. The problem can be made simple by assuming ε₂→0, where ε₂ is the element of permittivity tensor. This happens, if the operating frequency is assumed to be very large as compared to ω_c (cyclotron frequency) while it is of same order of ω_p (the plasma frequency). The case ε₁ =1, ε₂→0 leads to the results for soft plate of finite length in an isotropic medium. Graphical study is performed to investigate the behavior of separated field for various physical parameters for isotropic and anisotropic media.