Vol 126, No 4 (2019)

A new approach to the theoretical evaluation of the local dielectric properties of media that contain an organic dye acting as a nanoprobe is proposed. The method is checked so as to evaluate the dielectric properties of the host molecule in a supramolecular inclusion complex from the experimentally measured shift of the optical absorption spectrum of the guest molecules (dye) after the complex formation. Using the Onsager–Liptay model, the dielectric properties of the cucurbit[7]uril cavity was theoretically estimated by analyzing the experimentally measured shift of the absorption spectrum of 1-(3-ammoniopropyl)-4-[(E)-2-(3,4-dimethoxyphenyl)-ethenyl]-pyridinium dication of the dye after it forms a complex with cucurbit[7]uril in an aqueous solution. To parameterize the Onsager–Liptay equation, the positions of the absorption spectral maxima of the dye under study were experimentally measured in the following solvents with known dielectric and optical properties: methanol, ethanol, 1-propanol, 1-butanol, and water. When calculating molecular structures, dipole moments of the ground and excited states, and polarizability, the TD-DFT quantum chemical method with the CAM-B3LYP functional in the 6-311G(d,p) basis set was used within the Gamess (United States) software package. The obtained theoretical value of the effective dielectric permittivity of the cavity (about 13) is in good agreement with the published value.

IR absorption spectra of mixtures (¹²CH₃)\(_{2}^{{13}}\)CO/HF and free (¹²CH₃)\(_{2}^{{13}}\)CO molecules are recorded in the region of 4000−800 cm⁻¹ with a Bruker IFS-125 HR vacuum Fourier spectrometer at room temperature with a resolution of 0.05 cm⁻¹. Absorption bands of the (¹²CH₃)\(_{2}^{{13}}\)CO…HF complex are obtained by subtracting the absorption bands of free HF and acetone molecules and absorption lines of atmospheric water from the experimental spectrum of mixtures. Spectral characteristics of the 2ν(¹³C=O) overtone band of free acetone were also recorded. Comparison of the spectral data obtained with the analogous data measured earlier for the (¹²CH₃)\(_{2}^{{12}}\)CO…HF complex shows changes in the absorption spectra of complexes caused by ¹²C → ¹³C isotopic substitution. The frequencies and intensities for absorption bands of both complexes are calculated using the perturbation theory and methods MP2/6-311++G(2d,2p) and MP2/6-311++G(3df,3pd) with allowance for the error of superposition of basis functions of the monomers. The calculated results are in good agreement with the experimental data and are used to interpret the observed spectra. The influence of anharmonic effects on the frequencies and intensities of the strongest ν(H–F) and ν(¹³C=O) bands is examined with the help of variational calculations. It is shown that, unlike the (¹²CH₃)\(_{2}^{{12}}\)CO…HF complex, the 2ν(¹³C=O)/ν(H–F) resonance is virtually absent in the (¹²CH₃)\(_{2}^{{13}}\)CO…HF complex.

Halogen-substituted perovskites Ba₄In₂Zr₂O_10.95F_0.1 and Ba₄In₂Zr₂O_10.95Cl_0.1 are synthesized, and their single-phase composition is verified by X-ray diffraction analysis. Their ability of the studied phases to hydrate and form energetically unequal OH^– groups is proved. It is found that introduction of halide ions leads to a decrease in the hydration degree with respect to the matrix composition, which is explained by a decrease in the crystal unit cell free volume Processes.

The results of nonempirical quantum chemical calculations of CaF₂, SrF₂, and BaF₂ crystals that were activated by In³⁺ and Ga³⁺ ions have been presented. The calculations were performed in the framework of density functional theory using the VASP software complex. The estimation of the width of the band gap of defect-free crystals have been carried out by different methods and the influence of impurity ions on the band gap width has been estimated as well as the possibility of getting rid of shallow traps by introducing an impurity of indium or gallium has been investigated.

Damage to paper (sulfate pulp, cotton half-stuff, and flax half-stuff) caused by the Aspergillus niger, A. sclerotiorum, and Penicillium chrysogenum fungi is investigated by Raman spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy. It is shown that the use of application infrared Fourier-transform absorption spectroscopy allows one to identify the initial stages of damage from a decrease in the degree of crystallinity of the cellulose contained in paper. The absorption band near 900 cm^–1 is used as an indicator of early stages of damage. An increase in the amide II peak at 1550 cm^–1 and spectral changes in the region of valence vibrations of the C–H bonds (2800–3000 cm^–1) are observed in the case of heavier damage. The obtained data indicate that the vibrational spectroscopy techniques are promising in the study of damage of archive documents.

We have constructed a spheroidal model to solve the problem of light scattering by nonspherical particles. The semiaxes of the model spheroid are determined based on the requirement that the volumes of initial and model particles are equal, as well as the ratios of their longitudinal and transverse dimensions. This ensures the closeness of the optical properties of initial and model particles. This approach has been applied to prolate and oblate parallelepipeds, cylinders, and cones with the ratios between their larger and smaller dimensions equal to 2 or 10. The direction of propagation of the incident TE or TM plane wave was either parallel or perpendicular to the symmetry axis of particles and model spheroid. The particle size has been determined by dimensionless parameter \({{x}_{{v}}}\) = \(2\pi {{r}_{{v}}}\)/λ, which depends on the particle volume, since \({{r}_{{v}}}\) is the radius of the equivolume sphere. In calculations, this parameter has been varied from small values to fairly large ones, \({{x}_{{v}}}\) = 10. The applicability range of the model has been determined by comparing the results of numerical calculations performed by the rigorous separation of variables method for spheroids and the method of discrete dipoles for other nonspherical particles. It has been shown that the applicability range of the model for parallelepipeds, cylinders, and cones is wide enough for different parameters of the problem, in particular, if the parameter \({{x}_{{v}}}\) ≤ 6, then the relative error of the model does not exceed 10–15%. To a large extent, this is related to the fact that the first maximum of the dependence of scattering factor Q_sca on \({{x}_{{v}}}\) is similar for particles of different shapes approximated by one and the same model spheroid.

It is proposed to use the phase properties of a reflective interferometer upon oblique incidence for spectral selection in lasers. The effect is achieved due to the difference in phases of waves having different polarization and reflected from the reflective interferometer. A simple version in which the wave is incident at the Brewster angle on the reflective interferometer in the form of a plate with a single totally reflecting face is considered for several materials of the plate. It is shown that one such element can replace several plates of Lyot-type filters. A cavity with two reflective interferometers has been calculated; in this cavity, one can multiply increase the selectivity. A version of a cavity with a reflective interferometer in the form of a thin-layer coating is considered; for this cavity, a mechanism for a twofold increase in the free dispersion region due to inclusion of a metal layer into the coating is proposed. Results of calculating a specific device for a wavelength of 0.6 μm are presented.

The possibility of using a “pulsed fiber laser–photothyristor” optocoupler as a switch in the excitation schemes of copper vapor lasers (CVLs) has been investigated. It has been shown that such a switch has a nanosecond performance and is able to form monopolar and alternating current pulses through CVLs with a power of up to 10 MW and a repetition rate of tens of kilohertz when an electrical efficiency of the excitation circuit is more than 95%. A simple but very accurate model of a photothyristor is proposed, which can be used in full-scale CVL modeling programs.

The problem of the propagation dynamics of three-dimensional ultimately short optical pulses in an optical cavity in a periodically inhomogeneous medium of oriented carbon nanotubes is considered. It is shown numerically that such pulses demonstrate stable and sustainable propagation. In addition, it is shown that one can control for the pulse propagation rate and modify the pulse shape by varying parameters of the inhomogeneous medium.

Mechanisms of plasmon and polariton attenuation of solar radiation are successively activated in crystal nanoparticles of reduced (doped with oxygen vacancies) tungsten trioxide and titanium dioxide doped with metals with a valence of 5 or 6 upon electrochemical injection of electrons followed by injection of positively charged ions. Application of mesoporous electrodes fabricated from such nanoparticles in electrochromic glass makes possible separate dynamic regulation of transmission of visible light and near-infrared radiation, which enables gradual change of the glass state from light warm to light cold and further to dark cold. Results of studies of electrochromic glasses with separate regulation of transmission of visible light and near-infrared radiation are analyzed. Information on the influence of structural characteristics of the mesoporous electrode and the type of the electrolyte on optical spectral properties, duration of transient processes, and cyclic stability of the device are summarized. It is established that electrochromic glasses with nanostructured one-component electrodes fabricated from reduced tungsten trioxide and doped titanium dioxide exhibit optimal optical, exploitation, and technological properties.

The operating principle of the optical grating waveguide sensors is considered. The waveguide sensitivity and detection limit of sensors with waveguides of oxide and chalcogenide glasses are compared. The advantages of the grating waveguide sensors with waveguides with a high contrast of refraction indices are shown. The conditions of obtaining a maximum waveguide sensitivity of the grating waveguide sensors are formulated.

In spectroscopy, hollow cathode lamps are subject to increased requirements for radiation parameters. To check spectrometric equipment, it is necessary to create a highly stable source of spectral lines, the intensity of which on the given spectral lines will remain unchanged (≤1%) for a long time. A solution to this problem is proposed, and a scheme of an experimental test bench for a hollow cathode lamp with an optical-electronic negative feedback loop is presented. The feedback signal controls the current source, which is a functional unit of a specialized power supply unit and generates an electric current flowing through the lamp. The results of an experimental study with an appropriate metrological analysis are presented. The proposed technical solution to build a stable source of spectral lines allowed us to obtain a high level of stability of spectral lines in both the short and long term.