Vol 126, No 2 (2019)

Probabilities of electric-dipole 3d⁹4p → 3d¹⁰, 3d⁹4s transitions in the spectra of nickel-like ions Cd XXI, In XXII, and Sn XXIII are calculated semiempirically in the intermediate coupling scheme. The radial integrals necessary for obtaining absolute values of the probabilities are calculated in the length form with Hartree–Fock functions.

The europium(III)–tris(dibenzoylmethane)–triphenylphosphine oxide complex was studied in the polycrystalline state and in toluene at 298 K using the luminescence excitation method with two-stage rectangular pulses with decreasing intensity of stages. Experimental nonmonotonic kinetic curves were numerically simulated within the framework of a four-level dynamic model describing reversible processes in the complex, associated with its structural rearrangement. The maximum correspondence between the experimental and simulated curves was obtained using an iterative approximation performed using the Nelder–Mead algorithm. Based on the obtained numerical values of the rate constants and parameters of the model, experimental kinetics were interpreted, and it was concluded that they are a consequence of the processes associated with changes in the ligand composition of the Eu³⁺ chelate.

The results of the fabrication of technological regimes of formation and the study of the optical properties of light emitting diodes (LED) micropyramids based on InGaN/GaN are presented. The structures were formed by the method of Metalorganic vapour-phase epitaxy. LED hetero structures based on single micropyramids demonstrate electroluminescence at a wavelength of 520–590 nm, which is shifted to the shortwave length region with increasing current pumping. These light-emission sources are of interest for the fabrication of high-intensity point light sources for biosensor applications.

Recording media for polarization holography have been created on the basis of 4-((2-bromo-4-nitrophenyl)diazenyl)phenyl methacrylate copolymers, and the properties during that they manifest during recording of holograms of a plane wavefront have been studied. It has been found that the hologram recording rate at room temperature is the same for the perpendicular and parallel polarization of recording rays and the hologram relaxation rate is higher in the case of perpendicular polarization orientation of recording rays. It has been shown that the diffraction efficiency of holograms does not exhibit a monotonic relation with the film softening temperature.

Concerning direct acceleration of charges by pulses of electromagnetic (laser) radiation with arbitrary shapes, we have found a relationship between the components of the mechanical momentum of a relativistic (but not ultrarelativistic) particle. In a wide range of conditions, the energy transferred by the radiation to a particle to be accelerated is determined by the electric area of the laser pulse, i.e., by the integral of the electric field strength over the pulse time. This indicates that it is promising to develop schemes for generation of quasi-unipolar radiation laser pulses, in which the strength of the dominant component of the electric field does not change its sign during the main pulse duration.

Structural and photoelectric properties of composite Ag:Si layers formed in the near-surface area of a single-crystal c-Si substrate by a high-dose implantation of Ag⁺ ions with subsequent pulsed laser annealing (PLA) have been studied. It has been established that, as a result of ion implantation, a maximal concentration of Ag impurity (N_Ag ~ 4 × 10²² at/cm³) is concentrated near the surface and drops to a level of ~10¹⁹ at/cm³ at a depth of ~60 nm. Meanwhile, Ag nanoparticles and silver oxide (Ag₂O) inclusions are contained in a formed thin layer of amorphized Si (a-Si). Melting of a near-surface area and diffusion redistribution of the implanted impurity have been achieved in conditions of PLA, which increases Ag concentration near the surface and at a depth of 60 nm. Dark current–voltage characteristics of a junction between a Ag:Si layer and a p-Si substrate showed formation of a diode structure as a result of PLA. Photoconductivity measurements on formed samples demonstrate the presence of a photoresponse (photo-EMF) in the range of wavelengths of 500–1200 nm, which intensity increased for samples that are subjected to PLA when increasing energy density in the pulse. The obtained results demonstrate the potential use of composite Ag:Si layers and the method of their formation in the technology of photodetectors.

Fluorescent silver nanoclusters immobilized on a plastic substrate are obtained by photoinduced template synthesis using polyacrylic acid chemically grafted to the substrate surface as a template. The electronic absorption and fluorescence spectra of nanoclusters are studied depending on the polyacrylic acid grafting density. It is found that the optical absorption and fluorescence intensities of nanoclusters monotonically increase with increasing grafting density. The position and shape of the absorption and emission spectra almost do not change. The higher the polymer template grafting density, the higher the fluorescence stability of samples during storage at room temperature.

We investigate the dispersion properties of the first waveguide modes in a dielectric film that is coated with graphene layers having different chemical potential values. The control over the phase and group velocities of the first waveguide mode is considered. Spectral intervals in which the phase velocity of the waveguide modes is small, while their group velocity is negative, are revealed. We show that the dispersion characteristics of the waveguide modes can be rearranged using an external electric field.

A two-stage probe atomizer for direct analysis of samples that strongly smoke when evaporating (oil, food suspensions, etc.) by Zeeman atomic absorption spectrometry with high-frequency modulation of the polarization of the transmission radiation has been proposed. The effective ventilation of the atomizer and independent heating of the tungsten probe in a strong magnetic field of the atomizer have been provided for sensitive detection of atomic absorption pulses without overlapping of the transmission beam by the probe. The performance of the atomizer has been illustrated on the MGA-915MD spectrometer by the behavior of the signals of the Ag and Al test elements depending on the heating modes, probe position, and diameter of the dosing hole of a graphite furnace. The range of concentrations to be determined has been extended by a factor of 50, while maintaining an error at a level that is acceptable for quantitative analysis.