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The filamentation dynamics of 15 GW femtosecond laser pulses at 800 and 400 nm wavelengths upon their tight focusing in air is studied experimentally. The spatial position and extent of plasma channel formed within the filamentation zone as a function of laser pulse power are investigated. The processing of the experimental data according to the Marburger formula by J. H. Marburger [Prog. Quantum. Electron. 4, 35 (1975)] and the dispersion relations for air cubic nonlinearity has allowed to estimate the effective value of the Kerr-driven air refractive index on 400 nm as 5.36 × 10−19 cm2/W with a 5% error.

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The influence of the energy of femtosecond laser pulses on the intensity of Fe I (371.99 nm) emission line and the continuous spectrum of the plasma generated on the surface of Fe 3+ water solution by a Ti: sapphire laser radiation with pulse duration <45 fs and energies up to 7 mJ is determined. A calibration curve was obtained for Fe 3+ concentration range from 0.5 g/L to the limit of detection in water solution, and its saturation was detected for concentrations above 0.25 g/L, which is ascribed to self-absorption. The 3σ-limit of detection obtained for Fe in water solution is 2.6 mg/L in the case of 7 mJ laser pulse energy. It is found that an increase of laser pulse energy insignificantly affects on LOD in the time-resolved LIBS and leads to a slight improvement of the limit of detection.

Expansion regimes of plasma (fast ionization wave, laser supported radiation wave, and laser supported detonation wave) produced by laser–induced breakdown in air have been studied. To determine a pattern of plasma expansion a numerical investigation of propagation velocity dependence on laser radiation intensity was used. Calculation results agree with the experimental data and show that the most expected high-speed mechanism is fast ionization wave.

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Abstract. We presented the results of expedition measurements of the set of physical-chemical characteristics of atmospheric aerosol in areas of the Arctic and Far East seas, performed onboard RV Akademik Fedorov (17 August-22 September 2013) and RV Professor Khljustin (24 July-7 September 2013). The specific features of spatial distribution and time variations of aerosol optical depth (AOD) of the atmosphere in the wavelength range of 0.34-2.14 µm and boundary layer height, aerosol and black carbon mass concentrations, and disperse and chemical composition of aerosol are discussed. Over the Arctic Ocean (on the route of RV Akademik Fedorov) there is a decrease in aerosol and black carbon concentrations in a northeastern direction: higher values were observed in the region of Spitsbergen and near the Kola Peninsula; and minimum values were observed at northern margins of the Laptev Sea. Average AOD (0.5 µm) values in this remote region were 0.03; the aerosol and black carbon mass concentrations were 875 and 22 ng m −3 , respectively. The spatial distributions of most aerosol characteristics over Far East seas show their latitudinal decrease in the northern direction. On transit of RV Professor Khljustin from the Japan Sea to the Chukchi Sea, the aerosol number concentration decreased on average from 23.7 to 2.5 cm −3 , the black carbon mass concentration decreased from 150 to 50 ng m −3 , and AOD decreased from 0.19 to 0.03. We analyzed the variations in the boundary layer height, measured by ship-based lidar: the average value was 520 m, and the maximal value was 1200 m. In latitudinal distribution of the boundary layer height, there is a characteristic minimum at a latitude of ∼ 55 • N. For water basins of eight seas, we present the chemical compositions of the water-soluble aerosol fraction (ions, elements) and small gasphase species, as well as estimates of their vertical fluxes. It is shown that substances are mainly (75-89 %) supplied from the atmosphere to the sea surface together with gas-phase species. The deposited ions account for from 11 to 24.5 %, and trace elements account for 0.2-0.4 % of the total sum of water-soluble components. The average vertical fluxes of aerosol substance are a factor of 4-7 larger in the Japan Sea than in the water basins of Arctic seas.