Vol 59, No 1 (2016)

Spectral, luminescent, and lasing characteristics of chromene dyes and their julolidine analogs emitting in the red spectral range are investigated experimentally and theoretically. It is shown that the cause for a low lasing efficiency of oxochromene compared with iminochromene is a high intersystem crossing to the T₁ state and the presence of the induced T₁→T_n absorption in the region of the luminescence band.

Nonlinear optical properties of peptide nanobelts and peptide nanospheres, the two types of self-assembled triphenylalanine-based peptide nanostructures, are studied. Nanobelts nonlinear susceptibility tensor components are evaluated, and nanobelts crystal structure and crystallographic orientation are defined on the basis of nonlinear optical mapping and polarization dependences of the second harmonic signal. The results obtained suggest that it is possible to use these materials as biologically compatible nonlinear optical converters.

A study of the existence of “wormholes” and pathways of their formation, which is a problem of current interest, is continued. Of especial interest is the possible existence of traversable “wormholes,” in particular those in which gravitational forces do not act on test particles. It is shown that in the presence of a vortex gravitational field interacting with self-gravitating physical fields, such conditions can be met.

A solution of the Dirac equation for an electron in the field of a point nucleus (Ze), expressed in terms of an eigenfunction of the operator of the spin projection onto the third axis and the corresponding solution of the Schrödinger equation is derived. This solution is suitable for practical calculations. On the basis of this solution, using ordinary methods of QED and field theory, general principles for the emission of photons, axions, and neutrinos \( {(Ze)}^{*}\to (Ze)+\gamma, a,\kern0.5em v\overline{v} \) by a hydrogen-like atom are formulated which take into account the spin state of the electron and, in the case of photons, their polarization. This range of questions pertaining to a comparative characteristic of processes of emission of massless or almost massless particles has, to this day, not been discussed from this point of view in the literature. Selection rules for \( \gamma, a,v\overline{v} \) emission processes are also obtained, where for axions and neutrinos they coincide with the existing selection rules in the literature ∆m = 0,±1; with ∆l = ±1 pertaining to photons, but for photon emission a few of them do in fact differ from them with the hypothesis of odd values of ∆l, not established by us and additional to the usual values ∆l = ±1 of variation of the azimuthal quantum number l due to the appearance of “new” integrals over the spherical angle \( \theta \) for ∆m = ±1, where for ∆m = 0, as before, ∆l = ±1. Moreover, the dependence of the amplitude of the photon emission process on the quantum numbers is in principle different than in the previously adopted approach to the problem although the lifetime in the excited state for small values of the quantum numbers coincides in order of magnitude with the accepted value ~10^–9 s.

The orthogonal fast Lyapunov indicator (OFLI) and the modification of the mean exponential growth factor of nearby orbits (MEGNO) proposed recently and called the orthogonal MEGNO indicator (OMEGNO) are compared theoretically and numerically. It is shown that these indicators are expressed in terms of the same base function. Moreover, the OMEGNO, as well as the OFLI, is expressed analytically through the base function. A numerical comparison is performed on examples of studying the dynamics in the planar circular restricted three-body problem. These examples help one to understand the special features in the performance of both indicators.

The effect of the initial phase composition of a Ti–Al–V–Mo alloy (VT16 according to Russian classification) on the evolution of its structural-phase state during the formation of ultrafine-grained structure and subsequent annealing is investigated by methods of optical and transmission electron microscopy and x-ray diffraction analysis. The structure is produced by cyclic pressing with a change of the deformation axis in each cycle combined with a gradual decrease of the pressing temperature from 1073 to 723 K. As this takes place, α″ → α + β and β → α phase transitions are found to develop in the test alloy. The phase state of the ultrafinegrained material thus produced depends for the most part on its elemental composition and severe plastic deformation regime. Annealing below the recrystallization temperature is shown to give rise to a β→α phase transition and alloying element redistribution. The foregoing processes allow for retaining a high level of the strength properties of the alloy.

A numerical method is proposed for solving the Thomson problem – finding stable positions for a system of N point charges distributed on a sphere that minimize the potential energy of the system. The behavior of this system is essentially nonlinear, and the number of metastable structures grows exponentially with N. This makes the problem of finding all stable configurations extremely difficult. The results of testing of the developed algorithm and of numerical study of the properties of the local potential energy minima for a system of point charges are presented.

This paper examines the dependence of memory effects of induced magnetic anisotropy (IMA) on pressure. The authors suggest an empirical formula for this dependence and analyze the possibility of using IMA properties in aviation industry, particularly in wear control of gas turbine engines.

A self-consistent mathematical model of a plasma of scalar charged particles is formulated for a conformally invariant scalar field on the basis of relativistic kinetic theory. It is shown that the cosmological model based on a conformally-invariant phantom scalar field is scale-invariant in the ultra-relativistic limit.

It is shown that the resonance effect of a magnetohydrodynamic hypersonic shear flow on an elastic plate placed in it causes the development of wind instability. Plate bending oscillations propagating along the flow are stabilized in the hypersonic flow regime, whereas waves running at an angle to the flow remain unstable. Expression derived for the instability increment allows conclusions about the effect of the magnetic field on the interaction of waves with the flow to be drawn as well as about the feasibility of its suppression in an unstable flow regime.

A technique is presented, by which the magnetic susceptibility χ_|^G of the ion core of an anisotropic semiconductor Bi₂Te₃–Sb₂Te₃ crystal is determined from experimental data on the magnetic susceptibility χ_∥ and χ_⊥ obtained with allowance for the orientation of the magnetic field vector H with respect to the trigonal C₃ axis of the crystal in accordance with the expression χ_∥/χ_⊥ = (χ_∥^eh + χ^G)/(χ_⊥^eh + χ^G).In this expression, the value of the magnetic susceptibility of free charge carriers χ_∥^eh and χ_⊥^eh depending on their effective masses m_∥^* and m_⊥^* known from the experiment is calculated within the framework of the Pauli and Landau- Peierls approaches. The found value of χ_|^Gfor Bi₂Te₃–Sb₂Te₃ crystals is in good agreement with experimental data, as well as with the estimates obtained in the framework of the Larmor approach explaining, in particular, a linear dependence of the molar magnetic susceptibility on the number of electrons in the molecule observed for a large number of compounds. The proposed technique can be extended to other anisotropic semiconductors.

The data on the influence of irradiation of (Ti, Cr)N_1–x coatings by helium and argon ions on their surface structure are presented. The (Ti, Cr)N_1–x coatings 50–300 nm in thickness were formed on carbon steel substrates by vacuum-arc deposition. Irradiation of the coated specimens was performed in a DC-60 heavy-ion accelerator by low-energy ₄He⁺¹, ₄He⁺² and ₄₀Ar⁵⁺ ions and high-energy ₄₀Ar⁵⁺ ions up to the fluence 1.0·10¹⁷ ion/cm² at the irradiation temperature not higher than 150°С. It is shown that irradiation of the (Ti, Cr)N_1–x coating surface by ₄He⁺¹, ₄He⁺² and ₄₀Ar⁵⁺ ions with the energy 20 keV/charge does not give rise to any noticeable structural changes nor any surface blistering, while its irradiation by ₄₀Ar⁵⁺ ions with the energy 1.50 MeV/amu causes blistering.

The Ruderman–Kittel–Kasuya–Yosida exchange interaction (RKKY) is semi-empirically studied for the first time in compounds of binary REM – Al systems (REM – rare-earth metals: Gd, Dy, Ho, Er) using experimental values of paramagnetic Curie point (θ_р) of these compounds. Prediction of the RKKY theory was confirmed, i.e. there is a direct proportional dependence of θ_р value on de Gennes factor for equiatomic compounds of heavy REM with aluminum, just as in the case of pure REM. Values of the indirect exchange interaction parameter were semi-empirically estimated for the studied compounds. In general, it was established that RKKY-type exchange interaction is typical for REM compounds with aluminum, just as for pure REM.