Vol 122, No 5 (2017)

A particle swarm optimization algorithm is applied for mathematical treatment of Fourier-transform IR spectra of branched copolymers of methyl methacrylate. The efficiency of reconstruction of the spectra using the particle swarm optimization algorithm as compared with the least squares method is illustrated by the example of decomposition of a six-component experimental spectrum.

The oscillator strengths for Rydberg states of a NaHe molecule are calculated using a semianalytic procedure with the l-coupling effect taken into account (due to the dipole potential of a core). This effect gives rise to nonzero oscillator strengths for transitions forbidden in the atomic model of molecular Rydberg states. The difference between calculations in terms of the atomic model and calculations with consideration of the dipole moment of a core is shown for allowed transitions.

Methods of synthesis of cyclometalated azobenzene palladium(II) complexes of [Pd(N^N)Azb]ClO₄ and [Pd(N^O)Azb]ClO₄ types (where Azb^– is the deprotonated form of azobenzene; N^N is 2NH₃, ethylenediamine, or 2,2′-bipyridine; and (N^O)^– is the deprotonated form of amino acid (glycine, α-alanine, β-alanine, tyrosine, or tryptophan)) are developed. The electronic absorption and the electrochemical properties of these complexes are studied.

A functionalization of the surface of detonation nanodiamonds by photochromic spirocompounds from the classes of spiropyrans and spirooxazines has been carried out for the first time. A comparative study of the interaction of nanodiamonds with positive and negative potential is performed by the spectral–kinetic method, which shows the possibility of surface modification by only functionalized molecules of spirocompounds with the formation of surface proton complexes. This is confirmed by the hypsochromic shift of the absorption bands of the photoinduced merocyanine forms of adsorbed molecules of spirocompounds and by the decrease of the speed of their dark relaxation to the initial state in the presence of nanodiamonds with a negative potential.

The results of measuring the spectra of polystyrene samples in the IR range (4000–400 cm^–1) obtained by transmission, specular reflection, frustrated total internal reflection, and diffuse reflection have been compared. Polystyrene samples in the form of a thin film, a bulk sample, and foamed polystyrene have been investigated. The frequencies of the strongest bands in the spectra obtained by the methods under comparison are shown to depend on the anomalous dispersion in the vicinity of these bands and the specific features of structural chemical composition of the polystyrene–air interfaces. The presence of these interfaces is most pronounced in the reflection methods.

The optical sensory properties of polymethylmethacrylate films doped with 2,2-difluoro-4-methylnaphtho-[2,1-e]-1,3,2-dioxaborine (1) for water vapor are found. A mechanism of the optical response is proposed: water molecules contribute through hydrogen bonds to the dissociation of aggregates of 1 having intense excimer luminescence of J-aggregates. A sharp quenching of luminescence is observed. The spectrum of the films after exposure to water vapor corresponds to the monomer luminescence of 1.

Specific properties of the radiation emitted by a spatially modulated resonance medium excited by an ultrashort light pulse propagating through the medium at a variable superluminal velocity are analyzed. In so doing, frequencies different from that of the resonance transition of the medium may appear in the emission spectrum. It is demonstrated that, in contrast to an earlier studied case of medium excitation at constant velocity, variation of the excitation velocity leads to generation of a spectral continuum, the boundaries of which are determined by the range of variation of the medium-excitation velocity.

The quantum dynamics of the mean number of photons and quantum entropy of interacting modes, as well as the Wigner function of the stationary state of the fundamental mode and the third subharmonic mode has been investigated for the intracavity third-subharmonic generation. It is shown that the quantum dynamics of the system depends strongly on the nonlinear coupling coefficient between the modes. It is also demonstrated that, in the steady-state limit, depending on the intermodal coupling coefficient, the fundamental mode can be either in a pure coherent state, or in a squeezed state, or in a pure vacuum state. The third subharmonic mode in the subthreshold regime of generation of this mode is in the vacuum state. The Wigner function is squeezed over three sides of an equilateral triangle (squeezed vacuum). The quantum entropy of this state is nonzero. It is also shown that the third subharmonic mode, depending on the nonlinear coupling coefficient in the steady-state limit, can be localized in the three-component state with the same probability of detecting a field in each coherent component of the state and with the presence of quantummechanical interference between the state components. The mean number of photons in this state is smaller than unity. Depending on the nonlinear coupling coefficient, the third subharmonic mode can also be localized in the three-component state, which is a statistical mixture of three squeezed states.

Light absorption by a single spherical crystalline silicon (c-Si) particle and by monolayers of submicron c-Si particles arranged in triangular lattice is examined within the wavelength range from 0.28 to 1.12 μm. Data for spectral and integrated (over the terrestrial solar spectral irradiance “Global tilt” ASTM G173-03) absorption coefficients of monolayer demonstrating the possibility to enhance light absorption by a particulate active layer of crystalline silicon are presented. They are calculated in the quasicrystalline approximation of the theory of multiple scattering of waves. It is shown that in the narrow wavelength intervals (up to 10 nm) the spectral absorption coefficient of monolayer can be more than 100 times larger than the one of the plane-parallel plate of equal volume of material. Some results on the transmittance and reflectance of partially ordered monolayer are presented as well. The potentialities of light absorption enhancement in a single monolayer and three-monolayer system are considered.

The specific features of light transmission in a cholesteric liquid crystal (LC) cell with a director rotated by 90° have been investigated. In this structure, where a light wave is incident at a large angle with respect to the LC surface, the light is reflected (refracted) in the LC layer near the opposite boundary. It is shown that the application of an electric field changes the character of extraordinary wave refraction, as a result of which light starts passing through a cell. The transmission threshold voltage is determined, and its dependence on the angle of incidence of light is obtained. The dependence of the transmitted-light intensity on the voltage across the cell is obtained as well. The same dependences are also derived by numerical calculations with allowance for the turning points and extinction.

A method for calculating the spontaneous-emission probability for arbitrary layered structures in the waveguide mode has been developed based on the scattering matrix formalism. The results of calculating the mode Purcell factor for the TE and TM modes of a planar waveguide are shown. Analytical estimates for the mode Purcell factor are obtained, and the conditions for achieving maximum amplification of spontaneous emission in a waveguide are determined.

We have developed a mathematical model of thermomechanical and thermooptical processes that proceed in the output window of a continuous gas laser of a multikilowatt power. Optimal parameters have been determined at which the output window not only successfully withstands an extreme radiation load, but also ensures the radiation coupling with a minimum possible divergence. We have used numerical modeling to analyze the properties of the most promising materials used in high-power СО₂, СО, and oxygen–iodine lasers.