Vol 25, No 4 (2017)

The results of comparative analysis of laser desorption/ionization, matrix-assisted laser desorption/ ionization, and new laser-induced electron transfer desorption/ionization methods, used to detect chlorophyll A; mercury complex with thiuram; platinum complex with mercaptoquinoline; and lutetium complex with phthalocyanine, modified by crown ether, are presented. The new method is found to have a better ionization efficiency for complex compounds than the conventional laser desorption/ionization methods.

The Tamm minibands in planar superlattices composed of graphenes with different Fermi velocities and energy gaps have been investigated. It is shown that Tamm minibands arise only in the case of intersection of the dispersion curves of charge carriers in different superlattice regions.

A theory of generation of anti-Stokes radiation on the eigenvibrations in a suspension of cylindrical nanoparticles in the field of two copropagating electromagnetic pump waves has been developed. Surface ponderomotive forces are shown to induce acoustic vibrations and dipolemoments of nanoparticles at the anti-Stokes frequency. Under these conditions, the scattering efficiency depends on the dielectric characteristics of the solution and the acoustic parameters of the liquid and solid fractions of the suspension. Experiments on stimulated low-frequency Raman scattering of laser radiation in aqueous suspensions of tobacco mosaic virus in a buffer solution have been performed. A coherent signal of the Stokes component with a frequency shift of ≈60GHz is detected; this value is in good agreement with the estimated frequency shift for stimulated excitation of eigenvibrations of cylindrical nanoparticles in a liquid: ≈50 GHz.

A technique of probe photoluminescence and Raman spectroscopy has been developed. This technique makes it possible to detect small (10⁻⁶ to 10⁻⁸ g) amounts of uranyl compounds at short exposure times (1−10 s). The photoluminescence spectra of Na[UO₂CH₃(COO)₃] polycrystals recorded upon excitation by short-wavelength radiation of LEDs and lasers are found to contain equidistant bands with a shift of 854 cm⁻¹, which corresponds to the frequency of totally symmetric uranyl vibration also manifesting itself in Raman spectra.

Pulse generation (pulse duration 370 to 34 ns) is obtained for the semiconductor disk laser optically pumped by the Cr:LiCAF laser beam. Dynamics of its lasing spectrum during the pump pulse is investigated. Generation pulse variations under the mismatch of the pump spot and the region of the main disk lasing mode are studied.

A fiber-optic delay line based on the successive transmission of a modulated optical signal through all seven cores of an optical fiber has been fabricated. The total loss of the signal after the transmission through all cores is less than 12 dB. The group delay in the range of modulation frequencies of 6 to 12GHz is found to be 5.62 μs for a fiber as short as 160 m.

The results of natural studies of the methods for simultaneous measurements of the speed of sound in water and water temperature, as well as the depth, true bearing, and orientation of vector-scalar antenna in three-dimensional space, are reported. The tests were performed in the towing mode using a portable multifunctional complex, including hydrophysical, orientation, and direction finding units. The complex is recommended to be included in the composition of stationary or towed scalar or vector-scalar antennas.

Development of Benjamin−Feir instability is investigated under laboratory conditions and by analytical modeling. Nonlinear properties of the wave train with discrete spectrum are also investigated. The mechanically generated waves are composed of several discrete waves, while the newly generated harmonics are still combined into discrete spectra with the same frequency step. The technique proposed in this study allows us to study accurately the nonlinear variations in main properties of each harmonic with fixed frequency, such as amplitude, phase speed, and wavenumber along the wave tank together with velocities of wave packet crests, especially for the large transient waves. The phase speeds of short waves increase near large transient waves, and the velocities of longer waves are close to the values determined by the linear theory of waves. The relative long wave accompanied by short waves can dramatically change the local kurtosis and skewness of the wave field. They may play an important role for the generation of large transient wave and provide an opportunity for triggering of the freak waves.