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

A “hard” LLL interferometer made of dislocation-free silicon single crystal has been investigated; it differs significantly from previously known types of X-ray interferometers. Such an interferometer is highly sensitive to both initially present and introduced defects in the crystal. Several dislocations were generated in the modified part of the interferometer’s mirror block, as confirmed by X-ray topograms. Interferometric images of dislocations generated in the mirror block were obtained. The numerical simulation of single edge dislocation imaging is carried out according to the considered scheme.

Using laser radiation with a wavelength of 852 nm, which is in resonance with Cs atoms, the bright laser-induced fluorescence (LIF) on the blue lines of 456 and 459 nm (transitions 6S_1/2 → 7P_3/2 and 6S_1/2 → 7 P_1/2) was studied by the transition 6S_1/2 → 6P_3/2. A 1 cm long T-shaped sapphire cell containing Cs atomic vapors was used. The LIF power was investigated as a function of the cell temperature. A linear dependence of the LIF power on the pump radiation was observed. The LIF reached a maximum at 100°C. It is shown that the Cs cell can serve as an effective optical up-converter filter of radiation with a wavelength of 852 nm to radiation with a wavelength of 456 nm.

The exciton absorption and photoluminescence processes in a uniform electrostatic field perpendicular to the quantization direction in a CdSe nanoplatelet (NPL) are considered. Within the framework of the Takagahara model, the effects of charge carrier polarization in the axial direction are considered. The dependence on incident photon energy is analyzed for exciton absorption, and luminescence coefficients are calculated within the same model. The effects of the NPL’s geometric parameters and the strength of the external field on the absorption and luminescence coefficients are also examined. The results show that when the external field increases, the heights of both the absorption and luminescence peaks decrease. Simultaneously, the corresponding peaks broaden with increasing field strength.

Thin films of polycrystalline cadmium sulfide (CdS) were deposited on polyimide substrates using the chemical bath deposition method at a fixed solution temperature of (62 ± 1)°C. The influence of deposition time on the structural and optical properties of the resulting thin films was studied in detail. X-ray diffraction (XRD) revealed that the films predominantly consist of the hexagonal phase of CdS, with a crystallite size of approximately 10 nm, which slightly decreases with increasing deposition time. The surface roughness of the films was measured using atomic force microscopy. Scanning electron microscopy showed a uniform, compact, and smooth film surface. Raman measurements revealed three main peaks corresponding to the 1LO, 2LO, and 3LO modes in CdS. Optical measurements showed a high transmittance coefficient (~85%) and a low reflectance coefficient (4–7%) in the spectral range of 520–1000 nm. Due to changes in the stoichiometry of the CdS films, the optical band gap varied within the range of 2.30–2.37 eV with increasing deposition time. Room temperature photoluminescence spectra of the films exhibited two emission peaks located at 500 nm (2.49 eV) and 708 nm (1.75 eV), which can be attributed to free carrier recombination and excitonic or radiative transitions involving donor and acceptor levels, respectively. The obtained results demonstrate that by controlling only the deposition time, it is possible to deposit CdS thin films on polymer substrates at a relatively low chemical bath temperature. These films, without any post-growth treatment, possess sufficiently good physical properties, making them suitable for use in various flexible optoelectronic devices.

X-ray diffraction and optical microscopy investigations of the structural and morphological properties of polycrystalline perovskite CsPbBr₃ thin films deposited by vacuum thermal evaporation were conducted. The effect of the thermal annealing regime of the deposited films on their phase composition, microstructure, morphology and degree of crystallographic texturing was studied. The character of the correlation between the average sizes of grains and crystallites (subgrains) and the degree of crystallites` texturing with change of the annealing regime of films was analyzed.

We study semiclassical scattering in Liouville theory, in SL(2,R)/U(1) WZW theory and in SL(3,R) Toda theory, using the relations between the in and out fields defined by the chiral currents of these theories. By these relations we investigate the generating functional F that corresponds to the semiclassical S-matrix. In particular, we construct the Legendre transform of F in a closed form. The construction scheme is similar for these three theories and the obtained functionals have a compact form. This provides a basis for the functional integral representation of the S-matrix in these theories, which earlier was known only for Liouville theory.

For the first time, the possibility of transforming sodium (Na) atoms into magnesium (Mg) during electrolysis was experimentally investigated. The experiments were carried out in an electrolyzer with aluminum electrodes using an aqueous solution of sodium chloride as the electrolyte. The electrolyzer was powered by electrical pulses with steep fronts. The chemical composition of the cathode surface was analyzed before and after exposure of the electrolyzer to short electrical pulses using a scanning electron microscope. As a result of the exposure, a significant accumulation of the chemical element magnesium was observed on certain areas of the aluminum cathode surface. The physical mechanism behind the appearance of the new element (Mg) is discussed.

This paper discusses the optical properties of multicenter GSAG:Ce crystals grown by vertically directed crystallization and polycrystalline samples prepared by solid-state reactions. The absorption and luminescence bands of Ce³⁺ ions in the GSAG:Ce crystal are formed by seven different activator centers. Almost half of the activator ions occupy dodecahedral sites surrounded by six octahedra occupied by Sc³⁺ ions. The second part of Ce³⁺ ions is surrounded by octahedra with various combinations of Sc³⁺ ions and Al³⁺ ions, as well as only Al³⁺ ions. The shape of the luminescence band (∼18 700 cm^–1) of Ce³⁺ ions of GSAG:Ce crystals containing from 0.5 to 2.5 at % of the activator is stably preserved, and the emission intensity increases with increasing concentration of Ce³⁺.

Second harmonic generation of q-Gaussian laser beam in thermal quantum plasma is investigated in present communication. There is production of transverse gradients of intensity in relativistic plasma due to self-focusing of main beam. These intensity gradients cause electron plasma wave excitation at frequency of main beam. The interaction of excited electron plasma wave with main beam generates 2nd harmonics. Nonlinear differential equation denoting behavior of beam waist of main beam and 2nd harmonics efficiency are derived by using paraxial theory. These equations are numerically solved for investigating impact of usual parameters of laser, plasma along with quantum contribution on beam waist and efficiency of 2nd harmonics. Comparison of current study is also done with cold quantum plasma and classical relativistic plasma cases.

The calculated and measured angular divergences and profiles of the electron beam of the LUE-75 linear electron accelerator, operating at the A.I. Alikhanyan National Science Laboratory, are presented. The results were obtained at various energies and target distances at the exit of the vacuum chamber. The installation of a remotely controlled scanner and network cameras enables visual computer monitoring and precise positioning of the irradiated sample.