Volume 52, Nº 4 (2017)

The isomeric ratios of some nuclear products of (p, n), (d, 2n), (α, p3n) reactions were analyzed. A comparison of calculation data obtained by using TALYS 1.4 software package with experimental ones shows that the observed significant discrepancies for definite nuclei may be accounted for by the influence of high-spin states on the values of isomeric ratios.

Computations for the Fano resonance in a 3D system of identical prolate metallic nanospheroids located at the vertices of a regular tetrahedron are presented. The long axis of one of the spheroids is oriented along the symmetry axis of the third order of the tetrahedron (Z-axis), and the long axes of the remaining three spheroids lie in the orthogonal plane forming angles 2π/3 with each other. The polarization vector of the incident light wave oscillates along the Z-axis and directly excites plasmon oscillations in only one spheroid. The results of computations are given, which show the strong nonuniformity of energy distribution between spheroids for various orientations of spheroids perpendicular to the Z-axis.

The results of theoretical research and numerical simulation of the difference frequency radiation (DFR) pulse generation in 5–25 μm wavelength range in the field of the pumping femtosecond laser pulse are presented. The pulse has the following characteristics: the central wavelength is 2 μm, duration is 34 fs and electric field amplitude is 70.71 MV/m. The pulse propagates in the ZnTe/air periodic structure with the number of periods along the normal to the (110) plane of the ZnTe crystal equal to 13; and the efficiency of the DFR generation is 1.11 × 10^–4. It is shown that the use of the liquid crystal phase transparent, placed in the focal plane of the frequencyspatial shaping system, allows one to realize the DFR pulse compression at which the maximum intensity is increased by a factor of six.

The problem of arising of regular convection in the horizontal layer of nanofluid being in the gravity field upon the spatially periodic distribution of volume heat sources is considered. It is shown that other conditions being equal the system response has maximum, when the period of sources is approximately equal to the doubled layer thickness.

For measuring laser beam profiles, a vibrating wire monitor (VWM) has been introduced. The measurements were carried out at different speeds of scan. Preliminary estimates were made for the calculation of the VWM response times with respect to the thermal losses along the wire, and radiative and convective losses. These estimates, however, do not determine the difference between the beam profile and the frequency response of the VWM for a given scan rate. To evaluate the reliability of the frequency response of the VWM, comparisons between forward and reverse beam scans at different speeds have been used. The results of these scans are used to correct the thermal inertia in the frequency response of the VWM.

The method of optical determination of temperature based on cooperative luminescence in the LiNbO₃ crystals doped with rare earth ions is proposed. As a temperature-dependent measurable characteristic, the quantum yield of luminescence is considered taking into account the processes of nonradiative redistribution of the electron excitation energy in the impurity subsystem. It is shown that the LiNbO₃–Yb³⁺ crystals can be used as a material for optical temperature sensors in the temperature range of 200–500 K with the average sensitivity of 0.12%K^–1.

The diffraction of hard X-rays in quartz single crystals is considered in the Laue geometry in the presence of temperature gradient. Spectral and angular characteristics of the reflected beam were experimentally studied versus the magnitude of temperature gradient. It is shown that as the temperature gradient applied perpendicular to reflecting (10ī1) atomic planes of quartz single crystal increases, the focus of reflected beam approaches the crystal, the angular and spectral widths increase, and intensity increases by orders of magnitude.