Journal of Contemporary Physics (Armenian Academy of Sciences)最新文献

The adequate depth of sensing the aquatic environment by a sensor based on a single-layer flat coil was studied. A radiofrequency sensor of the ~40–50 MHz range with a diameter of the sensitive element (a flat coil) of ~8 mm was used. Plastic cuvettes filled with distilled water placed in front of the sensor were used as the test medium, the number of which was sequentially increased. The frequency of the sensor was measured depending on the number of cuvettes placed in front of the sensor. The character of changes in the registered frequency of the sensor depending on the thickness of the aqueous layer selected as the medium was revealed.

For the process of non-degenerate parametric decay in an optical cavity, where a photon with energy ћω₃ decays into two photons with energies ћω₂ and ћω₁, where ћω₃ = ћω₂ + ћω₁, the possibility of formation of entangled field states in terms of photon number variables between interacting modes of the optical system is investigated. Strong entangled states are shown between the modes with frequencies ω₂ and ω₁ in the case of strong coupling between interacting modes. In the case of weak and very strong coupling between these modes, relatively weak entangled states are formed. In the case of weak coupling, these modes are localized in entangled vacuum states with low values of quantum entropy. For modes with frequencies ω₃ and ω₁etangled states are formed only in the case of strong coupling.

In this work, according to the data obtained from the induced circular dichroism spectra, the studied porphyrin binds to DNA by the intercalation method, and its Zn-containing analog by the externally ordered interaction was revealed. The absorption spectra of the studied complexes were obtained at different DNA concentrations, and the binding parameters (K_b, n) of porphyrins with DNA were computed from the data at two values of the ionic strength of the solution. It is shown that the places for binding porphyrins become less accessible at a higher ionic strength of the solution. An increase in the melting temperature of DNA in the presence of a metal-containing porphyrin is also observed, as well as a decrease in the stabilizing effect of porphyrins for an increase in the ionic strength of the solution.

The technology of vacuum co-deposition and sequential deposition of the mixed-halide perovskite films (CH₃NH₃PbI_3–xCl_x) has been optimized. The possibility of improving the thermal stability of films by adding cesium atoms to an inorganic precursor is demonstrated. The structural and optical properties of perovskite films on black silicon are synthesized and investigated. It is shown that films of high quality in structure and phase composition are formed, which are characterized by a low reflection coefficient in a wide range of radiation wavelengths. Vacuum-deposited perovskite films on black silicon have great potential for the development of high-efficiency tandem solar cells.

¹¹¹In is an important diagnostic medical radioisotope. We discuss the possibility of its production from ¹¹⁴Sn and ¹¹²Sn targets in proton-induced reactions. Analysis made on the base of TALYS-1.95 calculations. While the irradiation of ¹¹⁴Sn target leads to unfeasibly low yield of ¹¹¹In, ¹¹²Sn(p, x) production route is promising because of high yields of indirect production channels. According to simulation results, the yield of ¹¹¹In in ¹¹²Sn(p, x) reactions is higher than in the commercially used reaction ¹¹¹Cd(p, n)¹¹¹In and is comparable to yield in ¹¹²Cd(p, 2n)¹¹¹In reaction.

Atomic transitions of ³⁹K, D₂ line are studied in strong longitudinal magnetic fields, up to 1000 G, with a high spectral resolution. The saturated absorption (SA) method was used in a micro-cell filled with K vapors with a thickness of L= 30 µm. A double differentiation of the SA spectrum was carried out, which made it possible to obtain narrow (~50 MHz) atomic lines and study individual transition frequency and probabilistic behavior. Among alkali metals, the K atoms have the smallest hyperfine splitting of the ground levels. This allows one to observe the break of the coupling between the electronic total angular momentum J and nuclear I angular momentums at relatively low magnetic fields B > 300 G. In the case of using circularly polarized radiation (σ⁺ or σ^–), two groups (each consisting of four) equidistantly located total eight atomic transitions are recorded in strong magnetic fields. The experimental results are well described by a known theoretical model.

A systematic analysis of the spatial dynamics of the elliptically polarized light in a medium with the local inhomogeneity of the optical axis on the Poincare sphere has been carried out. A nematic liquid crystal with a twist orientation was considered such a medium. The existence of two special types of elliptically polarized waves is shown, which propagate in such a medium with a constant value of ellipticity, and the azimuth angle follow the rotation of the optical axis. The main features of the dependence on the sample thickness are revealed. For the analysis, we used the analytical solution of the system of coupled equations for the Cartesian components of the electric component of the light wave, obtained by passing to the rotating coordinate system.

A sensor for the detection of acetone vapors based on the nanocomposite multiwalled carbon nanotubes/tin oxide (MWCNT/SnO₂) material was manufactured by the hydrothermal synthesis method. The response of the MWCNT/SnO₂ sensor toward acetone vapors from room temperature to 300°C was investigated. The gas sensing characteristics of the MWCNT/SnO₂ sensor were investigated in the presence of different concentrations of acetone vapors (400 ppb–20 ppm) at an operating temperature of 250°C. At the same temperature, the impedance characteristics of the MWCNT/SnO₂ sensor were investigated both before and after exposure to acetone vapor. An equivalent electrical circuit for the MWCNT/SnO₂ sensor structure was proposed. The presented results indicate that the MWCNT/SnO₂ structure can detect very low acetone concentrations.

An estimate is given of the simulation with the Monte Carlo (MC) method using the signal to background ratios in invariant mass spectra of pion-kaon system for decays of D⁰ → K⁻π⁺ and (overline {{{D}^{0}}} ) → K⁺π⁻ originated from decays of D*⁺ → D⁰π⁺ and D*⁻ → (overline {{{D}^{0}}} )π⁻ at different momentum/angular bins of pions (when pion is coming to the ARICH acceptance) and kaons (kaon is in ARICH acceptance). The tabulated data for mentioned ratios will be used by Belle II collaboration to study the ARICH performance. Then the results of ARICH efficiencies and misidentification probability extracted based on tabulated ratios, will become important ingredient for future physics analysis.

The electronic states in a cylindrical quantum dot with a modified Pöschl–Teller confinement potential under the influence of high-frequency laser radiation are considered. Two types of laser radiation are considered: Gaussian and Bessel. Under the influence of high-frequency laser radiation, the confinement potential of the quantum dot is converted to a new, effective confinement potential. For example, in the case of a Bessel beam, instead of a Pöschl–Teller potential well, a double potential well is obtained in the axial direction. This leads to an interesting behavior of the energy states of the electron. In particular, the abovementioned leads to the formation of anti-crossing of the states, as well as to the merging of the neighboring pairs of energy levels.