Том 123, № 1 (2017)

The problem of changes in the expressions for effective operators of physical quantities (including an effective Hamiltonian) of a nonrigid molecule upon a change in its equilibrium configurations, in the case in which different possible geometries of such configurations correspond to different point groups, is considered for the example of the nonrigid dimethylacetylene molecule CH₃C₂CH₃ in the ground electronic state.

An attempt has been made to detect a helium synthesis reaction resulting from a collision of deuterium nuclei diffusing on a surface of a platinum cathode under gas-discharge conditions. After 134 h of discharge in a flask with deuterium, helium spectral lines have not been detected with an accuracy of 10^–4 of the intensity of deuterium spectral lines.

The radiation-chemical decomposition of n-hexane in a Be–n-hexane system under the effect of γ-irradiation at room temperature is studied by infrared reflection–absorption spectroscopy. In the absorbed dose range 5 kGy ≤ Ф_γ ≤ 50 kGy, intermediate surface products of radiation-heterogeneous decomposition of n-hexane (beryllium alkyls, π-olefin complexes, and beryllium hydrides) are detected. It is shown that complete radiolysis occurs at Ф_γ = 30 kGy; below this dose, decomposition of n-hexane occurs only partially, while higher doses lead to steady-state saturation. The radiation-chemical yield of the final decomposition product—molecular hydrogen—is determined to be G_ads(H₂) = 24.8 molecules/100 eV. A possible mechanism of this process is discussed.

IR absorption spectra of solutions of halothane (C₂HBrClF₃) and acetone ((CD₃)₂CO) mixtures in liquefied noble gases (krypton and xenon) have been recorded and analyzed. Bands due to weak hydrogenbonded complexes are identified. The complex-formation enthalpy is estimated in a series of temperature experiments on the change in the total intensity of the bands due to monomers and complexes. Second-order bands are found, which are assigned to the first overtone of stretching vibration CH of halothane and the Raman band related to simultaneous excitation of stretching vibration CH of halothane and stretching vibration CO of acetone. The results of ab initio calculation performed within the МР2/6-311++G(d, p) approximation are used to analyze the spectroscopic data.

Halogen-substituted barium indate Ba₂In₂O₅ based brownmillerites Ba_1.95In₂O_4.9F_0.1 and Ba_1.95In₂O_4.9Cl_0.1 have been synthesized. It has been verified radiographically that the single-phase condition is satisfied. The effect of the substituent ion nature on parameters of the crystalline lattice and lengths of In–O bonds has been revealed. The propensity of the phases under study for hydration and formation of energetically unequal ОН^– groups in the structure has been proved. In both the cases of doping, the degree of hydration decreased as compared to barium indate Ba₂In₂O₅, which is caused by the participation of the halide ion in the tetrahedral site of indium.

The character of packing of double-stranded DNA molecules in particles of liquid-crystal dispersions formed as a result of the phase exclusion of DNA molecules from aqueous salt polyethylene glycol solutions has been estimated by comparing the circular dichroism (CD) spectra of these dispersions recorded at different osmotic pressures and temperatures. It is shown that the first cycle of heating of dispersion particles with hexagonally packed double-stranded DNA molecules leads to the occurrence of abnormal optical activity of these particles, which manifests itself in the form of a strong negative CD band, characteristic of DNA cholesterics. Moreover, subsequent cooling is accompanied by a further increase in the abnormal optical activity, which indicates the existence of the “hexagonal → cholesteric packing” phase transition, controlled by both the osmotic pressure of the solution and its temperature. The result obtained can be described in terms of “quasi-nematic” layers composed of orientationally ordered DNA molecules in the structure of dispersion particles. There are two possible ways of packing for these layers, which determine their hexagonal or cholesteric spatial structure. The second heating → cooling cycle confirms these results and is indicative of possible differences in the packing of double-stranded DNA molecules in the hexagonal phase, which depend on the osmotic pressure of the solution.

A new efficient binary optimization method based Teaching-Learning-Based Optimization (TLBO) algorithm is proposed to design an array of plasmonic nano-rods in order to achieve maximum scattering coefficient spectrum. In binary TLBO (BTLBO), a group of learner consists a matrix with binary entries; control the presence (“1”) or the absence (“0”) of nano-rods in the array. Simulation results show that scattering coefficient strongly depends on the localized position of nano-particles and non-periodic structures have more appropriate response in term of scattering coefficient. This approach can be useful in optical applications such as plasmonic nano-antenna.

Quantum efficiency is an important characteristic of quantum memory devices that are aimed at recording the quantum state of light signals and its storing and reading. In the case of memory based on an ensemble of cold atoms placed in an optical cavity, the efficiency is restricted, in particular, by relaxation processes in the system of active atomic levels. We show how the effect of the relaxation on the quantum efficiency can be determined in a regime of the memory usage in which the evolution of signals in time is not arbitrarily slow on the scale of the field lifetime in the cavity and when the frequently used approximation of the adiabatic elimination of the quantized cavity mode field cannot be applied. Taking into account the effect of the nonadiabaticity on the memory quality is of interest in view of the fact that, in order to increase the field–medium coupling parameter, a higher cavity quality factor is required, whereas storing and processing of sequences of many signals in the memory implies that their duration is reduced. We consider the applicability of the well-known efficiency estimates via the system cooperativity parameter and estimate a more general form. In connection with the theoretical description of the memory of the given type, we also discuss qualitative differences in the behavior of a random source introduced into the Heisenberg–Langevin equations for atomic variables in the cases of a large and a small number of atoms.

The possibility of diagnosing the linear and nonlinear electrodynamic susceptibilities of media by examining the time profiles of extremely short terahertz radiation pulses (using pulsed terahertz spectroscopy methods) that are incident on a thin layer of a medium under study, are reflected from the layer, and are transmitted through it is shown theoretically. In the general case, the linear and nonlinear susceptibilities of different orders can be found by solving linear integral equations. Diagnostics is considerably simplified in the case of an isolated resonance of a medium with homogeneous spectral broadening, which is modeled by the response of an anharmonic oscillator.

Propagation of two- and three-dimensional ultimately short optical pulses (light bullets) in a medium exhibiting modulated refractive index and containing carbon nanotubes with a metallic type of conductivity is investigated theoretically. The dynamics of such pulses is demonstrated as a function of Bragg medium parameters. It is confirmed that the pulses are influenced by the state of the medium.

The effect of electromagnetically induced transparency (EIT) has been experimentally implemented for the first time for the (4S_1/2–4P_1/2–4S_1/2) Λ-system of potassium atom levels in a nanocell with a 770-nm-thick column of atomic vapor. It is shown that, at such a small thickness of the vapor column, the EIT resonance can be observed only when the coupling-laser frequency is in exact resonance with the frequency of the corresponding atomic transition. The EIT resonance disappears even if the coupling-laser frequency differs slightly (by ~50 MHz) from that of the corresponding atomic transition, which is due to the high thermal velocity of K atoms. The EIT resonance and related velocity selective optical pumping resonances caused by optical pumping (formed by the coupling) can be simultaneously recorded because of the small (~462 MHz) hyperfine splitting of the lower 4S_1/2 level.

We show that, for terahertz (THz) radiation, the effective focal length of a lens differs significantly from its geometrical-optics (nominal) focal length. As a pulse of THz radiation with a bell-shaped (Gaussian) transverse profile is incident on a lens, the field-amplitude distribution in the nominally focal plane of the lens may radically change, up to the formation of dips in the paraxial region. These changes in the spatiotemporal shape of the beam (pulse) may considerably distort the results of pulsed THz spectroscopy. These distortions can be minimized by using media with anomalous dispersion, including metamaterials.

The optical properties of metal monodisperse nanoparticles (nickel (Ni) and titanium (Ti)) with radii of 50–100 nm and of bilayer nanoparticles that consist of a metal core and a spherical shell made of oxide of the same metal have been studied theoretically in the spectral interval 250–2500 nm, and the results of the study have been analyzed. The influence of the parameters of nanoparticles (radius, nanoparticle shell thickness, etc.) and of the surrounding liquid (water) on the optical-absorption, scattering, and radiation-extinction cross sections of nanoparticles has been investigated. It has been found that, for certain values of the particle radius, Ti + TiO₂ and Ni + NiO nanoparticles are good radiation absorbers, especially in the ultraviolet, visible, and near infrared spectral ranges, and they can be used for purposes of solar-thermal energetics.

Measurement and calculation results are presented that confirm that design four-mirror compensators can be designed for the spectral range of 200–2000 nm that is widely used in modern spectral ellipsometers. Measurements and calculations according to standard ellipsometric programs have been carried out on a broadband LED spectral ellipsometer with switching of orthogonal polarization states. Mirrors with the structure of glass substrate/Al₂O₃ layer (20–30 nm thick)/Al layer (150 nm thick)/upper Al₂O₃ layer (with specified thickness d) have been prepared by vacuum-evaporation method. It is shown that the phase-shift spectra of a four-mirror compensator, two mirrors of which have a native oxide 5.5 nm thick and the two others of which have an oxide layer 36 nm thick, measured on the ellipsometer, are flattened in comparison with similar spectra of a compensator, all four mirrors of which have a native oxide, especially in the short-wavelength spectral region. The results of calculating the phase-shift spectra of the four-mirror compensator with six variable parameters (angles of incidence of radiation on the mirrors and thicknesses of oxide layers on four mirrors) are presented. High-quality achromatization in a wide spectral range can be achieved for certain sets of parameters.

Results of studying the optical properties of In_xTl_1–хI solid solutions in the concentration domain of 0.4 ≤ х ≤ 0.9 are presented. The dependence of relative linear expansion of In_xTl_1–хI crystals (Т = 300–520 K) has been obtained. In_xTl_1–хI crystals (Т = 300–520 K). Based on this, the temperature dependence of thermal-expansion coefficient α has been found. Dependence of birefringence Δn_i on temperature and concentration of the TlI component in the solid solution has been studied.