Vol 29, No 2 (2016)

The paper presents an overview of experimental and theoretical results, which were obtained from the study of the dependence of Zeeman splitting of the vibrational-rotational lines of the 0–1 band of the nitric oxide molecule absorption spectra on the magnetic field magnitude. The experiments were performed at the Laboratory of Gas Lasers of P.N. Lebedev Physical Institute, Russian Academy of Sciences (FIAN). The method of laser magnetic resonance (LMR) with the use of a continuous-wave frequency-tunable CO laser were used to record the spectra. The theoretical analysis of LMR spectrograms was carried out at the Laboratory of Theoretical Spectroscopy of V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (IAO SB RAS), where the numerical model was developed based on construction of the total effective Hamiltonian of the molecule accounting the interaction with an external magnetic field. The model allows calculation of LMR spectra under given conditions and description of the nonlinear dependence of splitting of rovibrational energy levels on the magnetic field magnitude. The comparison of calculated and experimental LMR spectrograms has shown that the numerical model adequately reproduces the positions of absorption peaks measured in a damped oscillating magnetic field.

Results of observation of the generation of aerosol particles and droplets in mixtures of saturated water vapor with air and molecular gases are described. The kinetics of generation of aerosol and droplets was studied in the absence of a monokinetic electron beam and under its influence on a gas mixed with supersaturated water vapor formed in the process of a controllable pressure discharge from a spherical chamber of 1.4 m diameter with the gas mixture into a vacuum reservoir ~40 m³ in volume. The generation kinetics was recorded by the low-angle laser beam scattering method (for droplets) and with an aerosol spectrometer (for particles). Experimental results show a significant dependence of droplet and particle generation on the ionizing radiation effect. The 3D computer simulation of the process of super-saturated water vapor condensation on ions by the lattice Boltzmann method (LBM) and molecular dynamics (MD) describes qualitatively the experimental results.

Results of an experimental study of spatial parameters of the region of multiple filamentation of gigaand terawatt pulses of a Ti:Sapphire laser in glass and water are described. The pulse-power dependencies of the coordinates of the filamentation region, the number of filaments, their distribution along the laser beam axis, and the mean length of the filaments are presented. It is shown that the spatial parameters of the filamentation region are qualitatively similar in water and glass. It is found that the number of filaments along the region of multiple filamentation is a unimodal distribution. When increasing the radiation power, the length of individual filaments in the region of multiple filamentation is reduced, and their diameters are quasi-constant at all power values implemented in the experiment. When attaining a certain power of laser pulses with a Gaussian energy-density distribution, the filamentation region takes the shape of a hollow cone with the apex directed to the radiation source.

Altitude profiles of temperature of the middle atmosphere (30–60 km) are determined from data of lidar sensing at wavelengths of 355 and 532 nm using a modified Rayleigh method. Temperature disturbances are discriminated against the background of average profiles, using a smoothing spline. The altitude profiles of the potential energy density of gravity waves are calculated directly according to temperature fluctuations. A continuous wavelet analysis is used to determine the spectral characteristics of wave disturbances, including local power spectra of temperature fluctuations and potential energy, as well as vertical phase velocity and period for extracted wavelengths. The developed software tools make it possible to determine the characteristics of the wave disturbances localized in time and identified with respect to wavelengths of wave disturbances (wave packets). Lidar measurements in Obninsk are described.

The problem of allowance for polarization in statistical simulation of satellite imaging of the surface of the Earth in the optical wavelength range is considered. It is shown that the neglect of polarizing properties of radiation can lead to significant errors when retrieving the reflection coefficients of low-reflectivity surfaces.

The detailed information on the “in situ” vertical distribution of optical characteristics of atmospheric aerosol is frequently absent because of the complexity and high cost of environmental monitoring from aircraft. This paper presents estimates of the atmospheric optical characteristic stratification effects on downward scattered radiation measured by a sun photometer at the Earth’s surface for two basic viewing geometries: in the solar almucantar and in the solar principal plane. We obtained estimates on the basis of numerical experiments, key parameters of which imitate both background (areas with low anthropogenic load) and extreme atmospheric situations (urban smog, dust haze over land, and dust outflow over water surface). In the visible spectral region, outside the oxygen, ozone, water vapor, and nitrogen dioxide absorption bands, the stratification of the atmospheric optical characteristics is shown to have no significant effect on the sky radiance in solar almucantar, however becoming important in the solar principal plane. The main factor is the vertical behavior of the aerosol extinction coefficient. The radiance calculation errors can be substantially reduced by using the simplest vertical profiles and, in particular, the exponential distribution of the extinction coefficient over height.

We present the results of applying the MTP-5PE meteorological temperature profiler for determining the spatial zones of possible aircraft icing in Tomsk airport on March 17, 2013. The spatial zones were determined using the RAP-algorithm, the Godske formula, as well as the AMIS-RF data for retrieving the humidity profile. The RAP algorithm and the Godske formula are shown to predict similar locations of spatial zones of possible aircraft icing. However, the RAP results are closer to the actual icing reports available from aircraft crews.

The problem of the second harmonic generation (SHG) of monochromatic spatially coherent paraxial radiation in homogeneous uniaxial quadratically nonlinear crystals upon focusing of a beam into a crystal by two crossed cylindrical lenses with different focal lengths is considered theoretically. The aim of the investigations was to determine optimum focusing parameters as functions of the main radiation power. The first part of this paper presents a mathematical apparatus necessary for carrying out the planned investigations. A variant of transforming a system of nonlinear wave equations to a form more convenient for further use is proposed. Some important particular cases admitting simpler solutions are considered. An asymptotically exact analytical solution of the SHG problem is presented.

The influence of subthreshold pulsed infrared illumination on the recognition reaction time was investigated when recognizing geometric figures on a monitor screen.