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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 CuAlO2 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 CuAlO2 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. [ABSTRACT FROM AUTHOR]

The formation and heating of laser plasma when silicon is irradiated in ambient air by pulsed laser radiation with wavelengths of 355 and 532 nm at radiation power density up to 5 GW/cm2 has been experimentally investigated. An increased efficiency of the formation and heating of ablation plasma is observed when nanosecond pulses with a wavelength of 355 nm are leading in the bichromatic irradiation of silicon. [ABSTRACT FROM AUTHOR]

The effects of the interpulse interval and the number of double laser pulses on the component and charge composition of the laser plasma formed intentionally by these pulses acting on an AD1 aluminum alloy target (LSS-1 spectrometer) were studied. It was shown that the concentration of Al ions and the products of their interaction with atmospheric oxygen and nitrogen increased by several orders of magnitude if an interpulse interval of 7–16 μs rather than a zero interval was used. The AlO suboxide and AlN molecule band intensities were highest for 40–50 sequential double pulses in a series and decreased if the number of pulses in a series increased because of poorer interaction of Al atoms and ions with air molecules and atoms at the outlet from the micronozzle as the microchannel depth and shape changed. The temperature in the region of plasma with the maximum content of Al III was estimated at ~22,000–30,000 K. The intensity ratio of AlO bands at 486.9/484.12 nm was used to determine the temperature in the AlO formation region. An expression was obtained for determining the temperature of the region corresponding to the maxima of AlO formation. The established temperature range of 4700–7000 K was slightly higher than the optimal AlO dissociation temperature (4400 K). A closed glass cell containing an Al target was used to obtain Al aerosols and products formed during interaction of Al ions with atmospheric oxygen and nitrogen. The size of Al2O3 primary particles obtained at a pulse energy of 53 mJ was estimated as 30–40 nm using high-resolution electron microscopy. The particles were assembled into agglomerates. The possibility of practical production of activated Al2O3 nanopowders by irradiating a target with successive series of 50 double pulses per point for 10 min in a closed bottle was considered. Raman spectroscopy was used to show that active forms of aluminum oxides and their interaction products with atmospheric oxygen and nitrogen in a laser plasma could be deposited on a glass surface in a closed cell. [ABSTRACT FROM AUTHOR]

The effects of the interval between pulses and the number of double laser pulses on the component and charge composition of the laser plasma formed by these pulses acting on an AD1 aluminum alloy target (LSS-1 spectrometer) are studied. It is shown that the concentration of Al ions and the products of their interaction with atmospheric O2 and N2 increase by several orders of magnitude if an interval between pulses of 7–16 μs rather than a zero interval is used. Formation of Al ions is studied as a function of pulse energy with an interval between pulses of 10 μs. The strongest lines for Al III ions are observed for a small number (~15) consecutive double pulses in series and a pulse energy of 53 mJ. The intensity of the lines for Al III ions decreases by about five times if the number of pulses in the series increases above a certain level (10–20) because of their active interaction with atmospheric molecules and atoms at the exit of the micronozzle when the channel shape is changed. Al nanopowders coated with a layer of aluminum oxide produced by irradiating an Al target with a series of 15 double laser pulses per point have sizes of mainly 50–60 μm. [ABSTRACT FROM AUTHOR]

Spectra and structures of near-surface plasma torches were studied experimentally by measuring the specific mass loss and plume luminosity caused by dual-pulse laser radiation at wavelengths 1064 and 532 nm on titanium in air as functions of the time between laser pulses and their sequence. Dependences of the laser-plasma temperature and concentration of charged particles on the paired laser pulse parameters were established at laser radiation power densities q1064 ≤ 3.1·109 and q532 ≤ 2.7·109 W/cm2 for λ = 1064 and 532 nm. The optimal conditions for recording erosion plasma spectra had the initial effect from second-harmonic radiation with a time interval between pulses of 4–5 μs; for specific mass loss, 3–6 μs. The results were important for enhancing the efficiency of laser emission spectral analysis and laser-plasma processing of materials. [ABSTRACT FROM AUTHOR]

A spectral-kinetic recorder operating in a special time-gating mode was developed for time-shifted measurement of time-resolved spectra and emission-line intensity kinetics in atomic emission analysis. The luminescence intensity kinetics of Cu, Zn, Sn, and Pb were recorded for two-pulse laser ablation of pure metals and multicomponent alloys. The spectral-line intensity kinetics of pure metals could be approximated with high accuracy by exponential functions. The analytical signal for ablation of multicomponent samples decayed exponentially only for interpulse laser intervals <3 μs. [ABSTRACT FROM AUTHOR]

We have experimentally studied the spectra and structure of a near-surface plasma and measured the recoil impulses when brass and graphite targets are exposed in air to dual laser pulses at the wavelengths 0.532 μm and 1.065 μm, as a function of the time interval between the laser pulses and the pulse sequence. We have established the dependences of the temperature of the laser plasma and the concentration of charged particles and also the recoil impulse on the parameters of the dual laser pulses for laser power density 4·109 W/cm. We show that the optimal conditions for recording the spectra of the ablation plasma occur when the second-harmonic radiation arrives first with time interval between laser pulses of 1.5-6 μs, and the optimal conditions for generating the recoil impulse involve an interval of 1.5-2 μs, which is important for improving the performance of emission laser spectral analysis and laser plasma micromotors for aerospace applications. [ABSTRACT FROM AUTHOR]

High-speed spectroscopy with spatial and temporal resolution is used to determine the basic plasma parameters and to examine the shift from an air plasma to an erosion plasma during multipulse laser irradiation of various metals at repetition rates ranging from 5 to 50 kHz with irradiances q > 2∙10 W/cm. The formation of a distinctive surface plasma structure is observed which (a) facilitates the expulsion of the shielding layer of "air" plasma produced during the first of a series of laser pulses by vapor from the target and (b) inhibits the propagation of a metal vapor plasma front into the air during the subsequent pulses. [ABSTRACT FROM AUTHOR]

We have developed laser spectral analysis (LSA) methods for quality control of starch products in the raw material stage and after thermomechanical processing (extrusion). We show that it is possible to plot a common calibration curve for analyte elements in different types of analyte samples, i.e., we have established that there is no matrix effect on the analysis results. [ABSTRACT FROM AUTHOR]

Spectroscopic studies are made of the laser plasma formed near the surface of a porous body containing nanoquantities of uranium compounds which is irradiated by two successive laser pulses. The feasibility of using laser chemical methods for obtaining nanoclusters of uranium oxide particles in the volume of a porous body and the simultaneous possibility of determining the uranium content with good sensitivity are demonstrated. The thermochemical and spectral characteristics of the analogs of their compounds with chlorine are determined and studied. The possibility of producing uranium dioxides under ordinary conditions and their analysis in the reaction products is demonstrated. [ABSTRACT FROM AUTHOR]

The possibilities of using dual-pulse laser atomic-emission spectroscopy for both the estimation of elemental concentrations in bronzes and layer-by-layer analysis of a bronze coating on steel bead wire have been examined. Two methods have been proposed to lower the radiation flux density q in studies of thin metallic layers. These were based respectively on using optical filters and defocusing the radiation with respect to a sample surface. It has been found that the decrease of q results in reducing the influence of tin on copper evaporation under dual-pulse laser irradiation. [ABSTRACT FROM AUTHOR]

In different regimes of exposure of metals to pulsed laser radiation, we show the role played by the liquid‐drop phase formed from the target material in a laser‐induced erosion plume due to bulk vaporization, in the dynamics of this plume. For some metals, the ranges of power densities of the acting laser radiation, at which the condensed‐phase particles influence the passage of laser radiation to the target surface, have been determined experimentally. The mechanism of realization of a low‐threshold breakdown has been revealed. [ABSTRACT FROM AUTHOR]

The efficiency of using the substance analyzed for spectral analysis of copper‐zinc alloys exposed to single and double laser pulses has been estimated. It is shown that the efficiency of using the substance depends strongly on the conditions of laser ablation and that it is higher in the case of two‐pulse laser action as compared to a single‐pulse one. [ABSTRACT FROM AUTHOR]

Comparative studies of the possibilities of using pulsed nitrogen and Nd:YAG lasers for emission spectrochemical analysis of copper‐zinc alloys have been made. The nitrogen laser developed on the basis of the commercial excimer laser provided an energy of radiation pulses of 5 mJ with an error of less than 0.8% at a repetition frequency of 100 Hz. The high stability and the high pulse repetition frequency of the nitrogen laser were attained due to the additional high‐speed fan inside the laser chamber, which provided agitation and circulation of the gas mixture. It has been shown by experiment that the spectral emission of the plasma formed by means of the nitrogen laser is characterized by intensity fluctuations with a root‐mean‐square deviation of 1.4%, whereas in the case of using an Nd:YAG laser it was 14.3%. The advantages of the nitrogen laser that are due to the increased signal‐to‐background ratio and the suppression of the selective evaporation effect have been revealed. [ABSTRACT FROM AUTHOR]

The dependence of the Stark width of the spectral line of He II Pα 468.6 nm on the electron concentration in the laser plasma of helium for the range of electron densities Ne = (1–10)·1023 m-3 and electron temperatures of the order of 60 kK has been measured. The results obtained correspond well to Griem's theoretical data. An empirical relation is suggested which makes it possible to reliably determine the electron concentration from measured halfwidths in the investigated range of Ne. [ABSTRACT FROM AUTHOR]

The brightness‐spectrum and energy parameters in the VUV range of the spectrum (hν ∼ 9–70 eV) of the surface laser plasma of polymeric targets in vacuum are determined experimentally. Using the experimental technology of double open and closed ionization chambers (as radiation detectors) requiring no absolute energy calibration in a wide range of regulation parameters of the effect of standard laser frequencies, we obtained new data on multifactor radiative gasdynamic processes of effect which are needed to determine emission and mass‐output characteristics of the targets irradiated under vacuum. [ABSTRACT FROM AUTHOR]

The laser plasma produced by irradiation of a graphite target simultaneously by the first and second harmonics of two Nd3+:YAG lasers has been studied by emission spectroscopy methods. The delay between radiation pulses (τ) varied from 0 to 700 μsec. It is established that in the absence of a delay between pulses (τ = 0) the increase in the intensity of plasma emission at the wavelengths corresponding to the radiative transitions of the C2 and C3 molecules is of nonradiative character. The plasma produced by laser radiation at the wavelength λ = 1064 nm exerts its influence on the radiation spectrum of the plasma produced by laser radiation at the wavelength λ = 532 nm, if the magnitude of the delay between laser pulses τ does not exceed 30 μsec. The most probable reason for this character of influence of the prepulse on the laser plasma radiation spectrum is sublimation of soot particles caused by laser radiation at λ = 532 nm. [ABSTRACT FROM AUTHOR]

We compare radiation of plasma flares produced on exposure of metals to laser radiation in a monopulse generation mode in the case of single and double pulses with change in air pressure. For double pulses, we established an increase in the duration and intensity of the radiation of spectral lines and also an analogy between the change in their intensities and those of single pulses obtained at a reduced air pressure. [ABSTRACT FROM AUTHOR]

Using the methods of laser-induced fluorescence and emissive spectroscopy, we carried out investigations of the formation of TiO molecules in a laser plasma produced by focusing the radiation of an AYG:Nd3+ laser on the surface of a titanium target in air. The radiation flux density varied within the range 108–1010 W/cm2. We investigated the distribution of molecules over internal states and the space-time distributions of Ti atoms in the ground, metastable, and excited states, as well as of TiO molecules in the ground and excited states. We found that gas-phase reactions with participation of Ti atoms in the ground state provide the most probable channel for the formation of TiO molecules; the role of reagents in ionized, excited, and metastable states is of secondary importance. [ABSTRACT FROM AUTHOR]

From the analysis of the contours of the spectral lines of target-material atoms, the electron and atomic concentrations and their variation with time are determined in the laser plasma of a combined Cu–Al–Cu target. The time dependences for the concentrations of electrons and atoms in the ground and excited states are explained within the framework of a model that allows for plasma decay being determined by processes of three-particle recombination and ionization as well as by the variation in the particle concentration in plasma expansion. [ABSTRACT FROM AUTHOR]

Diagnostics of a near-surface laser plasma, the plasma of a strong-current pulse gaseous discharge in inert gases, nitrogen, and carbon dioxide under conditions of intense evaporation of the wall of the discharge chamber, the plasma of a discharge with a hollow cathode, and the active medium of an excimer laser was conducted by methods of intracavity laser spectroscopy and laser-induced fluorescence. The dynamic fields and absolute concentrations of atoms, ions, molecules and electrons, the plasma temperature, and the velocities of flows of particles were measured. The quantitative determination of the density of particles in the erosion laser flame prior to breakdown and the phenomena associated with the formation of molecules in the laser plasma received primary consideration. [ABSTRACT FROM AUTHOR]