Spectral characteristics of luminescent emission of negatively charged nitrogen-vacancy (NV–) centers in synthetic diamonds while filling of lower spin sublevels by microwave radiation were studied. On recorded spectra secondary side spin resonances induced by the hyperfine interaction between the NV– center electronic spin and the 13C nuclear spin were found out on the frequencies of 2.8136 GHz and 2.9408 GHz.
The study of exciton cathodoluminescence in diamond is not only scientific but also practical importance. Ultraviolet radiation at a wavelength of 235 nm can be used for disinfection, activation of surface reactions, photochemistry, and more. Thus, diamond is a promising material for creating a cathodoluminescent source of ultraviolet radiation. We have investigated the temperature dependences of the exciton cathodoluminescence spectra of single-crystal diamond in the temperature range from 80 to 400 K. The temperature dependences showed a characteristic increase in the intensity of exciton cathodoluminescence in the range 230-240 nm with increasing temperatures from 80 K to 150- 180 K. Further increase in temperature to room temperature (297 K) leads to a twofold decrease in the radiation intensity. With a further increase in temperature to 400 K, no change in the cathodoluminescence intensity was observed within the error
The paper presents the results of studies of the effect of single presowing treatment of wheat seeds with XeCl excilamp radiation at 308 nm with various surface irradiation doses on the yield and seed quality of spring wheat of the Iren variety, obtained in 2018 in the Tomsk.
The study of optical absorption of CVD diamond near the fundamental absorption edge was performed in the temperature range of 87-296 K. At temperatures lower than 195 K the absorption was practically constant. At higher temperatures the sharp increase of absorption took place. This sharp increase was attributed to the sharp enrichment of the phonon spectrum. Same phonon modes have different contributions to the negative and the positive branches of freeexciton absorption. For the negative branch (phonon absorption) the TA-mode dominated. For the positive branch (phonon emission) the TO-mode dominated. The possibility of diamond-based cathodoluminescent UV-sources at 235 nm was demonstrated.
The paper presents experimental results of the investigation of microstructure of copper surface layer after treatment by runaway preionized diffuse discharge in a stream of atmospheric nitrogen. It is shown that after 100,000 processing pulses on the surface of copper specimens, a disoriented surface layer with a depth of up to 200 nm is formed. Moreover, the results of X-ray phase analysis did not reveal changes in the phase composition of the surface. However, as a result of surface treatment by plasma of a diffuse discharge, the lattice becomes larger and the microstress increases.
The paper studies the dynamics of a nanosecond diffuse discharge with no additional preionization at a voltage rise time of less than 1 ns and its effect on drinking and distilled water. It is shown that the diffuse discharge is formed due to avalanche charge multiplication initiated by fast electrons and is sustained by secondary breakdown waves through ionized gas channels. Fourier transform infrared spectroscopy reveals that repeated exposure to the discharge changes the absorption spectra of drinking and distilled water such that the stretching vibration band of OH groups broadens and lacks clearly defined peaks. The water conductivity after irradiation increases. Probably, this is due to cluster rearrangement of water molecules.
The paper presents the results of examination of copper samples exposed to a diffuse discharge initiated by a runaway electron beam in air under normal pressure. The changes in the chemical composition of the surface layers of copper caused by the action of the discharge were investigated. It has been found that the oxygen and carbon concentrations in the surface layers depend on the number of discharge pulses. The study was aimed at finding possible ways of using this type of discharge in research and industry.
The paper presents the results of an examination of aluminum samples exposed to runaway electron preionized diffuse discharges in air, nitrogen, and argon at atmospheric pressure. The changes in the chemical composition, structure, and hardness of the aluminum surface layers caused by the action of the discharge were investigated. It has been found that the oxygen and carbon concentrations in the surface layers depend on the number of discharge pulses and on the chemical composition of the working gas. The goal of the study was to find possible uses of runaway electron preionized diffuse discharges in research and industry.
The purpose of this paper was investigating the effect of volume nanosecond discharge in air at atmospheric pressure on the electro-physical properties of the HgCdTe (MCT) epitaxial films grown by molecular beam epitaxy. Hall measurements of electro-physical parameters of MCT samples after irradiation have shown that there is a layer of epitaxial films exhibiting n-type conductivity that is formed in the near-surface area. After more than 600 pulses of influence parameters and thickness of the resulting n-layer is such that the measured field dependence of Hall coefficient corresponds to the material of n-type conductivity. Also it is shown that the impact of the discharge leads to significant changes in electro-physical characteristics of MIS structures. This fact is demonstrated by increase in density of positive fixed charge, change in the hysteresis type of the capacitance-voltage characteristic, an increase in density of surface states. The preliminary results show that it is possible to use such actions in the development of technologies of the controlled change in the properties of MCT.
The results of the modification of stainless steel, niobium and titanium by volume discharge induced by a beam of runaway electrons in air under normal pressure are presented. Changes in the chemical composition of the surface layers of metal by the action of the discharge, structural changes and changes of hardness were studied. It has been found that the concentration of oxygen and carbon in the surface layers of the samples depend on the number of discharge pulses. The aim of this work is to find possible application of this type of discharge in science and industrial production.
In the present report we studied the distribution of surface potential of the HgCdTe epitaxial films grown by molecular beam epitaxy after the impact of picosecond electron beam and volume discharge in atmospheric-pressure air. The surface potential distribution was studied by the Kelvin Force Probe Microscopy. The experimental data obtained for the variation of the contact potential difference (ΔCPD) between the V-defect and the main matrix of the epitaxial film. The investigation of the origin epitaxial films show that variation of the spatial distribution of surface potential in the V-defect region can be related to the variation of the material composition. The experimental data obtained for the irradiated samples show that the mean value of ΔCPD for the original surface differs from the one for the irradiated surface for 55 eV. At the same time the mean value of ΔCPD changes its sign indicating that the original surface of the epitaxial HgCdTe film predominantly contains the grains with increased cadmium content while after the irradiation the grains possess an increased content of mercury. Therefore, during the irradiation process a decrease of the mercury content in the near-surface region of the semiconductor takes place resulting in the alteration of the electrophysical properties in the films near-surface region.
Formation of stable micro-protrusions and microstructures ("microtowers") on surface of liquid metals during
multipulse irradiation by UV and IR lasers in different ambient gases was discovered. The rates of the structure
formation have been measured which can reach 5 - 20 μm/pulse depending on the metal and ambient gas sort. Single
micro-protrusions 1-2 mm in length were formed with diameter approximately two times greater than the focal spot
size. The possibility to control the microstructure shape is shown and their potential applications are demonstrated.
Experimental and theoretical studies on laser ablation of polymers (PMMA, polyimide) have been performed in a wide
range of CO2-laser fluences. Evolution of polymer laser plume in air has been investigated with simultaneous
registration of radiation spectra of the ablation products, spatial dynamics of plasma flare, and temporal behavior of
plasma emission on separate spectral lines. It has been found that spectral lines have intensity peak after laser pulse
termination while plasma emission spectra are similar to those of organic material combusting. The results confirm that
combustion of the laser-vaporized polymers occurs in the plasma plume. A thermo-chemical model of heating and
ablation of organic polymers by CO2 laser pulses has been developed which takes into account attenuation of radiation in
laser plasmas and chemical processes leading to heating the plume of the ablation products. Temperature evolution in the
irradiated sample, ablation dynamics, and laser beam attenuation are analyzed. The modeling results are compared with
the experimental data on high-speed imaging of the plasma plume. The effect of the formation of a "plasma pipe" is
revealed under polymer ablation in air under normal conditions.
We report a new phenomenon, formation of microstructures, observed at multipulsed nanosecond laser ablation of liquid
metals (Ga, In, Sn-Pb alloy, Wood's metal). Laser irradiation of liquid metal targets was carried out in a gas chamber
equipped with a heater. In contrast to vacuum conditions or an inert atmosphere when a crater is formed which is healed
after termination of irradiation, ablation in a reactive ambient gas (air, nitrogen, sulfur hexafluoride, nitrogen trifluoride)
leads to a horn-like structure growing on the irradiated surface with the rate of 3-20 μm per pulse depending on laser
fluence and the types of metal and ambient gas. The interplay between different processes in a heat-affected zone of the
irradiated samples is analyzed, including ablation, thermal expansion, temperature variations of viscosity, surface
tension, thermal stresses, capillary and plasma effects, and surface chemistry. A clear picture of microstructure origin has
been established and a qualitative modeling representation is given to explain the growth process of microstructures. The
optimal conditions of microstructure growth have been determined and perspective applications of the discovered effect
are discussed.
The results of experimental investigations of a volume avalanche discharge initiated by an e-beam (VADIEB) and
surface layer of Cu and AlBe foils modifications at the plasma action of VADIEB are given. The volume discharge in
the air of atmosphere pressure formed in the gap with the cathode having small curvature radius and with high voltage
pulses of nanosecond duration and positive and negative polarity. A supershort avalanche electron beam (SAEB) with
formation conditions in gases under atmospheric pressure have been investigated. It is proved that the surface layer is
cleared of carbon at foil treatment, and atoms of oxygen penetrate into a foil. It is show that the cleaning depth depends
on polarity of voltage pulses. At positive polarity of a copper foil electrode the cleaning is observed at the depth over 50
nm, and atoms of oxygen penetrate at the depth up to 25 nm. Plasma of the superpower volume discharge of
nanosecond duration with a specific excitation power of hundreds of MW/cm3, and SAEB, and the discharge plasma
radiation of various spectral ranges (including UV, VUV and X-ray) has the influence on the anode. The supershort
avalanche electronic beam is generated only at negative polarity of a voltage pulse on an electrode with a small radius
of curvature. SAEB influence on modifications of the copper foil surface is registered. VADIEB is easily realized in
various gases and at various pressures, and, at gas pressure decrease the density of the beam current in helium can
achieve 2 kA/cm2. It allows predicting an opportunity of VADIEB application for metal surface modifications in
various technological processes, and for surface dielectric modifications at the certain design of the anode.
The experimental results of the studies on process of radiation interaction of the pulsed CO2 - laser with polytetrafluoroethylene (PTFE) are presented. A dependence of PTFE transmission factor at λ = 10.6 μm versus temperature in the range -90 - 300°C has been obtained.
Investigation of the modes of thin metal and ceramic films (0,3-1 μm) removal from the glass and stainless steel substrate by IR and UV laser radiation has been performed. It is presented that the efficient film destruction and removal occurs due to laser induced thermal strength under laser fluxes of ~0.5 J/cm2 not sufficient for phase transformation.
Formation of microscopic size colored dots on titanium foil surface by pulsed IR-laser irradiation was studied. It was found that the dot on titanium surface changes its color from yellow to blue as the exposure is increased. According to our numerical calculation, the colored dot formation is accompanying with titanium surface melting and partial evaporation. At pulse-periodical irradiation mode it can result in foil break-through.
The interaction of pulsed periodical CO2-(λ~10.6 µm), and Xe-(λ~1.73 μm) lasers radiation with surfaces of polymers has been studied. Correlation between parameters of surface erosion (area of crater and amount of evaporated material versus laser focus position and number of pulses) was investigated using teflon (polytetrafluoroethylene-PTFE) and vinypros (plasticized semi-transparent polyvinylchloride) sample. Monitoring of erosion track on surfaces was performed through optical microscopy. It has been shown that at pulsed periodical CO2-radiation interaction with teflon and vinypros the sputtering of polymers with formation of submicron-size particles occurs. Dependencies of particle sizes, form and sputtering velocity on laser pulse duration and target temperature have been obtained.
The interaction of Xe- (λ~1.73 µm) and XeCl- (0.308 μm) lasers radiation with surfaces of metal and TiN-ceramic coatings on glass and steel substrates has been studied. Correlation between parameters of surface erosion (area of crater and amount of evaporated material versus laser focus position and number of pulses) was investigated. Monitoring of laser induced erosion on smooth polished surfaces was performed using optical microscopy. The correlation has been revealed between characteristic zones of thin coatings damaged by irradiation and energy distribution over laser beam cross section allowing evaluation of defects and adhesion of coatings.
Presently, from the world data available on interaction of laser radiation with metal and dielectric surfaces and development of experimental diagnostic techniques by itself it is possible to raise a reverse question, namely, restoration of laser radiation energy spatial distribution through surface imprint. With this in mind, we have made the detailed morphology of imprint of a pulse HF-laser interaction with carbon steel surface through atomic force microscope. Interaction of the radiation of a relatively short pulse of ArXe-laser ((tau) ½equals400 ns, (lambda) equals1,73 micrometers , Q ~ 20 J/cm+2)) with carbon steel surface of 40X (4140 (USA)) type besides the surface layer hardening leaded to decrease of steel hardness at below original value on depth of about 10 - 12 micrometers . This effect can be related to occurrence of deformation and thermal residual stresses in the subsurface layer. At multiple-pulse interaction (~500 pulses) of UV-laser focused radiation ((lambda) equals0,222 or 0,308 micrometers , (tau) ½equals 12 or 20 ns) with the steel 40X (4140 (USA)) surface a distinct interference imprint of laser beam is formed after diffraction at outer diaphragm being determined by its form.
The complex of experimental installations for studying of laser radiation interaction with surface of metals has been established. At titanium surface irradiating depending on the accumulated laser radiation energy, the surface color might be changed from bright yellow to red and deep-blue colors. The presented results testify to the possibility to use the change of titanium surface color at heating by laser irradiation in the open air to obtain dot raster images. Presently, form the world data available on interaction of laser radiation with metal and dielectric surfaces and development of experimental diagnostics techniques by itself it is allowed to raise a reverse question, i.e., restoration of laser radiation energy spatial distribution through surface imprint. Using imprints, it is also possible to make an express diagnostics of multi-layer surface coatings. With this in mind, we have made the detailed morphology of imprint of the pulsed HF-laser interaction with carbon steel surface through atomic force microscope.
An idea of nonlinear optical cryptography is suggested. The simulations of the authors demonstrate a possibility of use of a nonlinear ring interferometer with heredity as device of hidden information transmission.
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