The effect of the energy, the interval between the pulses, and the number of double laser pulses on the formation of the component and charge composition of laser plasma by laser spark spectrometry (LSS-1 spectrometer) was studied. The processes leading to the formation of mixed nanopowders of copper and aluminum oxides, precursors for the production of nanoceramics and films of CuAlO 2 copper aluminates by the action of double laser pulses on a hybrid target consisting of cemented aluminum and copper plates, from AD1 and M2 alloys were investigated. It was shown that precursors for the manufacture of nanoceramics and nanofilms of CuAlO 2 copper aluminates can be obtained by the successive action of a series of double laser pulses with energy of 53 mJ and an interval of 10 μs on a hybrid target. A closed glass weighing bottle containing the target was used for the products formed during interaction of the aluminum and copper ions with atmospheric oxygen. The size of the initial particles, determined by means of a high-resolution electron microscope, amounted to 30–45 nm. The particles were assembled into agglomerates and had a crystalline structure and spherical form. On account of the purely diffusion transfer mechanism of the fractals the size and amount of the fractal aggregates settling on the support situated at the bottom of the cuvette were several times greater than the amount of the products that settle on the side support. The main contribution to change in the intensity of the spectral lines for the Al and Cu atoms and ions and the AlO molecular bands comes from interaction of the second pulse with the condensation products formed in the channel after the action of the first pulse. With increase in the number of long-lived fractal aggregates in the air the intensity of molecular bands and lines decreases by ~1.5 times for Al III and by ~2 times for copper, which is due to active interaction of the long-lived large fractals that accumulate in the air with the incident radiation.

This article presents the electrical circuit, a description of the design, and results of measurements of the radiative watt–ampere and time characteristics of compact inexpensive emitters based on commercial laser diodes with wavelengths from 405 to 850 nm, which operate in the picosecond (70–180 ps) and nanosecond (0.69–1.2 ns) modes. The optical emitter includes a master crystal oscillator based on a microcontroller (frequencies of 76 Hz–20/80 MHz), a synchronization circuit, a low-voltage (9–12 V) subnanosecond electric pulse shaper that operates according to the method of double differentiation, a pump circuit with an adjustable direct current source, and a laser diode. The average light power at a frequency of 80 MHz varies in pico mode from 0.6 to 1.6 mW and in nano mode from 6 to 18 mW. The lasers are powered by a 220 V/12 V, 0.25 A serial power supply, with a power consumption of 3 W and a weight of 0.2 kg.

The effect of the interpulse interval and the number of doubled laser pulses on the targeted formation ofthe component and charge composition of the laser plasma under the influence of doubled laser pulses on a target made of AD1 aluminum alloy (LSS-1 spectrometer) was studied. It is shown that when using he interpulse interval of 7-16 ps, the concentration of Al ions and the products of their interaction with oxygen and nitrogen in the air increases by several orders in comparison with the zero interval. The highest intensity of the bands of AlO suboxide and AlN molecules is observed at 40-50 sequential double pulses in a series. With an increase in the number of pulses in a series the intensity of the bands decreases that is connected with worsening of the interaction of Al atoms and ions with air molecules and atoms at the output from the micro nozzle with a change in the depth and shape of the microchannel. The temperature in the region of the plasma with the maximum content of Al III of ~ 22000-30000 K was estimated. To determine the temperature in the region of AlO formation, the ratio of the intensities of the AlO bands at 486.9/484.12 nm was used. An expression is obtained for determining the temperature of the region corresponding to the maxima of AlO formation. The established temperature range of4700-7000 K is slightly higher than the optimal dissociation temperature for AlO (4400 K). To obtain Al aerosols and products formed during the interaction of aluminum ions with oxygen and nitrogen in the air, a closed glass cell was used, where an aluminum target was placed. The size of the primary particles of aluminum oxide Al 2 O 3 obtained at pulse energy of 53 mJ, estimated using high-resolution electron microscopy, is mainly 30-40 nm. The particles are assembled in agglomerates. The possibility of practical obtaining of activated Al 2 O 3 nanopowders by irradiating the target with successive series of 50 double pulses per point for 10 min in a closed bottle is considered. Using Raman spectroscopy, the possibility of obtaining active forms of aluminum oxides and their interaction products with oxygen and nitrogen of air in a laser plasma, deposited on a glass surface in a closed cell is shown.

We studied the effect of the pulse interval and the number of double laser pulses on the formation of the component and charge composition of laser plasma under the influence of these pulses on the AD1 alumi- num alloy target (LSS-1 spectrometer). It is shown that when using the inter-pulse interval in the range 7—16 s, the concentration of Al ions and their interaction products with oxygen and nitrogen in the air in- creases by several orders of magnitude compared to the zero interval. The dependence of the process of Al ions formation on the pulse energy is investigated for the case of the 10  s inter-pulse interval. For the 53 mJ pulse energy, the largest intensity of the Al III ion lines is observed for small (about 15) number of consecutive double pulses in the series. When the number of pulses in the series increases above a certain level (10—20), the intensity of the Al III ion lines decreases by about 5 times, which is due to their active in- teraction with air molecules and atoms at the exit of the micro-nozzle when the channel shape is changed. The temperature in the plasma region with the maximum Al III content gave values equal to approximately 22000—30000 K. Al nanopowders coated with a layer of aluminum oxide obtained by irradiating an alumi- num target with a series of 15 double pulses per point mainly have a size of 50—60 nm.

We developed and manufactured a laser atomic emission multichannel spectrometer (LAEMS) with an achromatic optical scheme for research and educational purposes. The new spectrometer fits all the requirements for equipment for laser-induced breakdown spectroscopy and also has a number of advantages due to the design and technical characteristics of its components. As an excitation source, the spectrometer includes two Nd:YAG lasers pumped by semiconductor laser diode arrays, with adjustable energy (from 0 to 100 mJ) and pulse interval (from 1 to 100 μs); the average pulse duration 15 ns. LAEMS permits to carry out studies using both single-pulse and double-pulse laser ablation and excitation of emission spectra. Using double pulse laser ablation on LAEMS, a significant (up to 10 times) increase in the analytical signal was recorded, with a slight (1.5–2 times) increase in the surface destruction.

We have experimentally obtained support for the feasibility of detecting cereal grains of different grinds from the diffuse reflectance spectrum. As the features describing the diffuse reflectance spectra of wheat and oats of different grinds and moisture contents in the near IR range, we used combinations of optical densities and their second derivatives for the wavelengths 1200, 1422, 1778, 1916, and 2114 nm. Using logistic regression as an example, we constructed 20 classification models based on the two features: 10 models for the optical density and 10 models for the second derivative of the optical density, corresponding to the selected wavelengths. The best classification results were obtained with an algorithm using the values of the second derivative of the optical density at λ = 1778 nm and 2114 nm as the features.

Rapid measurement of the moisture content of dehydrated residues is a critical problem, the solution of which will increase the efficiency of treatment facilities and optimize the process of applying flocculants. The ability to determine the moisture content of dehydrated residues using a meter operating on the IR reflectance principle was confirmed experimentally. The most suitable interference filters were selected based on an analysis of the obtained diffuse reflectance spectrum of the dehydrated residue in the range 1.0–2.7 μm. Calibration curves were constructed and compared for each filter set. A measuring filter with a transmittance maximum at 1.19 μm and a reference filter with a maximum at 1.3 μm gave the best agreement with the laboratory measurements.

The effect of nitrogen defects in monocrystals of natural and synthesized diamond on the position and width of the fundamental Raman band has been investigated. The samples containing main types of the nitrogen defects in diamond lattice at the impurity content of 1-1500 ppm have been taken for the study. Based on the analysis of parameters of the Stokes and anti-Stokes components in Raman spectra of the crystals that are placed in a cell with distilled water to minimize the influence of heating by exciting laser radiation, the effect of the nitrogen impurity presence in the crystalline lattice of diamond has been exhibited. It is shown that an increase of the nitrogen impurity content in the crystals within the studied concentration range results in the Raman band broadening from 1.61 to 2.85 cm - 1 and the maximum shifting to the low-frequency region from 1332.65 to 1332.3 cm - 1 . The observed effect value is directly proportional to the concentration of impurity atoms and depends on the form of the impurity ingress into the diamond lattice. It has been found that the change in the position and half-width of the fundamental Raman band for diamond is consistent with the magnitude of the distortions of the crystalline lattice parameter due to the presence of impurity defects and obeys the Gruneisen law.

The spectral properties of a novel thioflavin T derivative, trans-2-[4-(dimethylamino)styryl]-3-ethyl-1,3-benzothiazolium perchlorate (DMASEBT), were studied in aqueous solutions in the presence of sodium polystyrene sulfonate (SPS). It was shown that SPS either could interact with dye monomers or initiate the formation of non-fluorescent dye dimers depending on the concentration ratio of dye and polyelectrolyte. DMASEBT dimer formation in the presence of SPS produced a hypsochromic shift by 40 nm in the absorption spectrum and quenched fluorescence. A bathochromic shift of the absorption spectrum and an increase of the fluorescence intensity by an order of magnitude were observed if DMASEBT monomers interacted with SPS. Quantum-chemical analysis found that sandwich dimers (H-aggregates) were most stable. A comparison of DMASEBT spectra in the presence of SPS and amyloid fibrils showed that DMASEBT molecules were incorporated into amyloid fibrils as monomers. The spectral changes associated with this incorporation could not be explained by the formation of dye aggregates.

The results obtained in studies of laser-induced fluorescence of the normal and carries-affected dental tissues are presented. The possibility of detection of considerable depth caries with use of the specially designed spectrometric system with excitation by a semiconductor laser source with a wavelength of 684 nm for fluorescence is shown.