The paper deals with the use of the light detection and ranging (Lidar) system KA-14 for fluorescence spectra of crude oil spillage on the Caspian Sea and the Absheron Peninsula soil surfaces. The oil spillage occurs after its loss from Azerbaijan companies amounting to eight Azneft companies and four joint companies. The fluorescence spectra of crude oil are induced by the third harmonic generation of a 355-nm Nd:YAG laser at 20 Hz frequency, 60 mJ energy, and 7 ns pulse time. The analysis of these fluorescence spectra of crude oil from Azerbaijan deposits shows their shape, peak positions, fine structures (spectrum shoulders) at blue and red edges, and band intensity. The obtained results can be used to create the database of the fluorescence spectra of crude oil extracted from the Caspian Sea and the Absheron Peninsula.

The problem of electrical breakdown of exterior coating of aircraft was discussed and it is shown that the formation of a breakdown channel in a dielectric film is associated with the rupture of polymer macromolecules in stretched zones. On the example of polyether urethane film, it was experimentally revealed that with an increase in tensile loads, the breakdown voltage (dielectric strength) decreases exponentially.

We consider the problem of electric breakdown of external varnish-and-paint coatings of aircrafts. It is shown that the formation of the breakdown channel in the dielectric field is associated with rupture of polymer macromolecules in stretched regions. It is revealed in experiments with polyester urethane film that the breakdown voltage (dielectric strength) decreases exponentially with increasing tensile stresses.

AbstractThe results of measuring the electrical conductivity of layered crystals (GaSe, GaTe, and their solid solutions) and cubic crystals (Ga_2Se_3) in strong electric fields (up to 5 × 10^5 V/cm) in the temperature range of 77–300 K are presented. These results are compared with predictions of the phenomenological theory of concentration instability in semiconductors. This theory considers the role of the Frenkel effect, which is related to the thermionic ionization of traps causing instability in semiconductors with an S -shaped current–voltage ( I – V ) characteristic. Based on the results of measuring the electrical conductivity of layered and cubic crystals exhibiting the Frenkel effect and described by the theory of current instability in semiconductors, the free-carrier concentration in the aforementioned types of chalcogenide semiconductors is estimated to be n = (3 × 10^13–4 × 10^15) cm^–3.

The results of investigation of electrical conductivity of a large group of chalcogenide semiconductors having the layered, cubic, and orthorhombic structures in strong electric fields up to 105 V/cm are presented. The revealed increase in electrical conductivity σ in strong electric fields has been explained by the Frenkel thermionic ionization. This has made it possible, along with other parameters (for example, activation energy and trap concentration, charge-carrier mean free path, permittivity), to evaluate the concentration and mobility of charge carriers in semiconductors under study. It has been shown that in strong electric fields in semiconductors, when the thermionic ionization of the traps occurs, their permittivity ɛ, which is caused by the electron polarization, is determined by the simple formula ɛ = n 2, where n is the refractive index of light.

The photoluminescence and photoluminescence excitation spectra and luminescence decay kinetics of CaGa2S4:Eu2+ bulk crystals and powders ranging in particle size from 100 to 600 nm have been studied in the temperature range 77–300 K. The results indicate that the full width at half maximum of the photoluminescence band of the CaGa2S4:Eu2+ nanopowders is about twice that of the bulk crystals. Analysis of the photoluminescence spectra shows that the energy position of the emission band is almost independent of the particle size, temperature, and excitation intensity in the ranges 77–300 K and 10−3 to 106 W/cm2, respectively. The shape of the photoluminescence band is well represented by a Gaussian. The excited state lifetime of the Eu2+ ion is ∼1000 ns as evaluated from the exponential portion of the luminescence decay curve.

Cathodoluminescence spectra of the semiconductors (Ba,Ca)Ga-2(S,Se)(4):(Eu,Ce,Er,Yb) were studied and compared with their photoluminescence spectra. It was found that electron energy was converted most efficiently into light energy by Ba thio- and selenogallate co-doped with Eu and Ce and also by Ca thio- and selenogallate doped only with Eu.

The excitation and photoluminescence spectra of YbGa2Se4 and YbGa2Se4:Nd3+ single crystals recorded at different temperatures and neodymium concentrations have been investigated. The photoluminescence spectrum exhibits intracenter luminescence lines of the Nd3+ ion in wavelength ranges of 0.804–0.84, 0.88–0.92, 0.96–0.996, and 1.06–1.12 μm against a broadband emission background. These ranges are related, respectively, to the 4 F 5/2-4 I 9/2, 4 F 3/2-4 I 9/2, 4 F 5/2-4 I 11/2, and 4 F 3/2-4 I 11/2 transitions.

We have ground bulk samples to obtain nanoparticles of (Ga 2 S 3 ) 1– x (Eu 2 O 3 ) x solid solutions, the sizes of which were determined using an atomic force microscope. The photoluminescence spectra of the nanoparticles were studied in the temperature interval 77–300 K. We have established the mechanisms for emission and transfer of energy from the matrix to the rare-earth ion, and we determined the Stokes shift (ΔS = 0.7 eV), the Huang–Rhys parameter ( S = 16), and the optical phonon energy (ħ−ω = 23 meV).

This paper examines the formation of arrays of interlayer nanostructures in layered crystals grown by directional solidification and the Bridgman method. Sb2Te3 and Bi2Te3 layers are shown to contain steplayered structures with nanostructured islands on them. Atomic force microscope images of interlayer nanostructures in such crystals are analyzed in terms of the physics of fractals and self-organization processes.

The photoluminescence of barium thiogallates doped with Eu 2+ , Ce 3+ , and Eu 2+ + Ce 3+ ions is studied over a wide range of excitation levels (10 –3 –10 6 W/cm 2 ). Introduction of 3 at.% Eu and 3 at.% Ce instead of 5 at.% Eu into a BaGa 2 S 4 matrix doubles the luminescence quantum yield of the phosphor. Doped BaGa 2 S 4 exhibits a high linearity in its luminescence intensity as a function of excitation level (a constant efficiency) up to 2·10 4 W/cm 2 for excitation pulse durations of 8 ns, which corresponds to cw pumping at a power density of about 5·10 2 W/cm 2 in terms of the concentration of excited ions. It is shown that using BaGa 2 S 4 :Eu,Ce along with the “yellow” phosphor of a Nichia NS6L083 LED may increase its color rendering index from 0.64 to 0.80 with no reduction in its luminous efficiency.

We have ground bulk samples to obtain nanoparticles of (Ga2S3)(1-x)(Eu2O3)(x) solid solutions, the sizes of which were determined using an atomic force microscope. The photoluminescence spectra of the nanoparticles were studied in the temperature interval 77-300 K. We have established the mechanisms for emission and transfer of energy from the matrix to the rare-earth ion, and we determined the Stokes shift (Delta S = 0.7 eV), the Huang-Rhys parameter (S = 16), and the optical phonon energy (h omega = 23 meV).

An acoustophotovoltaic effect in TlIn 0.98 Gd 0.02 Se 2 single crystals has been detected and investigated.

The possibility of using the peculiarities of acoustic-optical effect for time-dividing channeling is considered; structure-electric scheme of acoustic-optical time-dividing channeling system is suggested; recommendations on choosing its parameters are elaborated.

Рассмотрена возможность использования особенностей акустооптического эффекта для временного уплотнения каналов, предложена структурно-электрическая схема акустооптической системы временного уплотнения каналов, выработаны рекомендации по выбору ее параметров.

Обсужден принцип действия универсального акустооптического преобразователя временного масштаба видеосигналов, который может работать как в режиме временной компрессии, так и в режиме временного экспондирования.

In this paper we discuss an operation of the acousto-optic videosignal temporal scale converter, which can operate in temporal compression mode and also in temporal expansion.