Vol 31, No 4 (2018)

The vibrational-rotational absorption spectrum of water vapor was recorded and analyzed in the visible spectral region from 19480 to 20500 cm⁻¹. The measurements were carried out using an IFS-125M Fourier spectrometer with a resolution of 0.05 cm⁻¹ at a pressure of 26.3 mbar, a temperature of (24 ± 1)°C, and optical path 24 m. We used a multipass White cell with a base length of 60 cm. A light-emitting diode was used as a radiation source. The signal-to-noise ratio was about 20000. The list of more than 420 lines has been compiled as a result of the analysis the spectrum, which includes line centers, intensities, and quantum vibrational-rotational numbers. More than 220 vibrational-rotational energy levels of 21 upper vibrational states have been determined from the experimental data.

The experimental study of the laser induced alignment of linear atmospheric molecules naturally present into the air using an ultra-short (femtosecond temporal range) and ultra-intense (TW · cm^–2 fluence range) linearly polarised laser pulse is described. The measurements are conducted under a two-color pump-probe configuration using an IR pump beam and a blue probe pulse (red-blue configuration), which interacts with the molecules after they have been exposed to the IR alignment pulse. The optical birefringence and dichroism polarimetric signals have been both strictly measured into the same experimental conditions into this two-color configuration. A balanced detection permits the heterodyne signal to be got directly. Under the short and intense laser pulse exposure, the molecules present into the atmospheric air (under standard room temperature conditions) aligne, and periodic transient revivals are observed (field free alignment approach into non-adiabatic conditions). The results obtained are in accordance with those obtained in the red-red configuration and confirm the approach proposed as relevant for atmospheric sensing.

General regularities of lidar returns in the sensing of the water column containing pelagic fish schools are investigated by the Monte Carlo method. Based on results of statistical simulation of depth profiles of lidar return power and depolarization, we propose a method of polarization laser sensing of marine fish schools based on a comparison of numerical values of the lidar return power and depolarization with their threshold levels determined by the sea water extinction index in the fishery region.

The results of WRF-CHEM model simulation of dispersal of anthropogenic emissions from the Norilsk industrial zone are verified against data of aircraft sensing performed in August 2004. It is shown that the WRF-CHEM v3.5.1 model configuration selected adequately reproduces the meteorological parameters obtained during the 2004 measurement campaign. The model-derived distributions of the concentrations of sulfur anhydride and ozone and mass concentration of aerosol qualitatively reproduce those retrieved from data of aircraft sensing. Quantitative estimates showed that the standard errors for sulfur dioxide, PM_2.5 mass concentration, and ozone, calculated for three flights, had been 23 ppb, 2.6 μg/m³, and 9.8 ppb, respectively. These discrepancies may be due to incorrect specification of the initial and boundary conditions, inaccurate specification of anthropogenic emissions, and limitations in the aerosol and chemical descriptions.

Interactions between iron oxide nanoparticles, produced in acoustoplasma discharge with cavitation, and blood plasma fibrinogen is studied in a model solution by dynamic light scattering. Depending on the storage time of the nanoparticles, their interaction with the protein shows different dynamics of the size distribution. However, the biological action of the nanoparticles is the same regardless of the storage time, i.e., they act as inhibitors of the reaction of fibrin gel formation.

Optical characteristics of water in stratified lakes of the White Sea are of particular interest in connection with the observation of thin colored layers resulting from massive development of anoxygenic phototrophic bacteria around the chemocline. While optical properties of chlorophyll are widely used in remote sensing, spectral characteristics of bacteriochlorophylls (BChl) for natural microbial communities have been little studied. In this work, spectral study of green sulfur bacteria of four water bodies of the Kandalaksha Gulf of the White Sea was carried out. Absorption and fluorescence spectra were measured for water samples taken in March 2017 from different depths and compared with spectra of monocultures isolated from the same water bodies earlier. It has been shown that the BChl fluorescence in the living cells of green sulfur bacteria has two overlapping emission bands: in the region of 740–770 nm (BChl d and e) and at 815 nm (BChl a). The wavelength of the maximum of the first band depends on the ratio of the concentrations of green- and brown-colored forms of bacteria containing different types of BChl. A new method for separating the contributions of two types of bacteria is proposed, based on the deconvolution of the BChl fluorescence spectrum into three bands whose parameters are determined from the spectra of monocultures. The BChl content at various water depths has been estimated and the percentage ratio of different types of phototrophic bacteria has been determined.

The discharge glow dynamics during a nanosecond breakdown of air and nitrogen initiated by runaway electrons in a point–plane gap is studied with an ICCD camera. The formation of plasma bunches forming a structure analogous to a bead lightning is observed. It is shown that the number of bright plasma bunches in the gap (individual beads) increases with pressure. Up to four individual beads of equal size have been recorded in nitrogen at a pressure of 0.4 MPa.

The spectral characteristics of spontaneous and stimulated luminescence of heavily silicon-doped Al_xGa_{1 – x}N structures with the concentration n_Si > 1020 cm^–3 are studied with pulsed optical pumping at λ = 266 nm. The resulting dominant broadband radiation with a full width at half maximum of ~150 nm covers the whole visible spectral region. The radiation spectrum from the end of the structure is split into narrow components determined by the mode structure of the planar waveguide formed. The results indicate the stimulated character of the radiation. The optical gain for different structures fall in the range 20–70 cm^–1.

The creation of a compact emitter for an inductive nitrogen laser (λ = 337.1 nm) with the active medium pumped by a pulsed inductive longitudinal discharge of the transformer type is reported for the first time. In the inductive laser head created, the lasing energy attains 0.35 mJ and the lasing pulse length is (25 ± 5) ns (FWHM) depending on the cavity Q-factor. The use of a semiconfocal cavity provides for a near-Gaussian beam profile.

Electrophysical processes in the discharge circuit of a pulsed metal vapor laser are analyzed. The greatest attention is paid to the initial period of the discharge development and conditions for the inversion formation. It is shown that the limitation of the frequency-energy characteristics (FEC) of lasing is due to the process of populating the metastable levels of metal atoms on the excitation pulse front and redistribution of the rates of population of the laser levels in favor of metastable ones with an increase in the prepulse electron density. Which of the processes plays a decisive role in limitation of the lasing FEC depends on the electrophysical process in the discharge circuit of the laser, the development of which is significantly influenced by the arrangement of electrodes in the gas-discharge tube (GDT). The arrangement of electrodes in the GDT also determines the conditions for the inversion formation and the choice of the optimal pumping parameters. Technical solutions are discussed under which the pumping efficiency of a copper-vapor laser attains ~10%.