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In this work, the analysis of the recorded spectrum of the ¹⁵N¹⁸O molecule in the region 5100-5500 cm^-1 was performed. As a result of the analysis, 187 positions of rotational lines in the vibrational band 3-0 of the main transitions between the electronic states ²Π_1/2 and ²Π_3/2 with the maximal rotational quantum number J = 32.5 were found. For the first time, Λ-splitting was observed in this band. The positions and relative intensities of both the resolved component of the Λ-doublets and unresolved doublets are determined. A joint weighted processing of all known vibrational-rotational frequencies of the transitions in the microwave and infrared spectral regions was carried out. As a result of the processing, “Dunham-type" constants for ¹⁵N¹⁸O isotopologue in the ground electronic state were determined. Using the found “Dunham-type" constants, predictive calculations of the rotational line positions of all bands corresponding to vibrational transitions between states with v ≤ 3 and J ≤ 37.5 were carried out.

Chloroform is one of dangerous pollutants in the atmosphere. To control it in the atmosphere by absorption spectroscopy, it is necessary to know the position of its spectral lines. In this work, the absorption spectra of CH³⁷Cl₃ isotopologue of gaseous chloroform are measured using a high-resolution nonstationary spectrometer in the frequency range 118-175 GHz, where spectroscopic data for this compound are absent. The identification of the chloroform lines presented in the literature and assigned to the vibrational state v₂ for CH³⁵Cl₃ is refined and their belonging to CH³⁷Cl₃ isotopologue is shown. The experimental results are compared with our theoretical estimates of absorption lines centers of the rotational spectrum of this molecule in the same spectral range. Absorption lines of CH³⁷Cl₃ isotopologue in the ground state were detected and identified in the spectral subranges near 131.4, 137.6, 150.1, and 156.4 GHz. Based on the experimental spectra, we have estimated the molecular constants B = 3129.56 MHz, D_J = 1.34 kHz, and D_JK = -2.25 kHz with RMSE = 7.84 ´ 10^-2 MHz, which determine transition frequencies in absorption spectra parts near 150,1 GHz and 156.4 GHz more accurately than molecular constants given in the literature ( B = 3129.61 MHz, D_J = 1.37 kHz, and D_JK = -2.28 kHz with RMSE = 11.55 × 10^-2 MHz). The results can be used for controlling the content of chloroform in the atmosphere.

Most measurements of aerosol attenuation of the atmosphere are carried out in the visible and near-infrared regions of the spectrum. However, many atmospheric optics tasks require data on the spectral course of aerosol attenuation coefficients in the visible and IR regions, including the atmospheric “transparency window” 8-12 mm. In this regard, models that make it possible to calculate attenuation in the IR region based on measurements in the visible region are of great interest. A one-parameter model of the spectral course of the aerosol attenuation coefficient for the surface layer of the atmosphere is proposed. The input parameter of the model is the aerosol attenuation coefficient at a wavelength of 0.55 mm or the meteorological range of visibility S _m. The model enables one to calculate aerosol attenuation coefficient in the spectral range 0.44-12 mm at meteorological visibility range S _m > 8 km. The model can be used to evaluate the efficiency of different optical systems and to separate aerosol attenuation into submicron and coarse components.

To perform accurate atmospheric correction (elimination of the distorting influence of the atmosphere) of satellite images, it is crucial to consider various factors that influence the received signal, including the non-Lambertian surface reflectance (the difference between surface reflection and Lambert's law, according which radiation is equally reflected in all directions and depends only on the irradiance of the surface and the reflectance). High-quality satellite information is important for solving a wide range of problems in monitoring the ground surface, such as forest condition, agricultural productivity, and others. In some algorithms, non-Lambertian reflection is taken into account after solving the problem in the Lambertian reflection approximation. In this case, the assumption is used that the adjacency effect (received radiation reflected from areas of the ground surface adjacent to the observed one and scattered in the atmosphere) is formed only by surfaces with Lambertian reflection. The calculations performed show that at S _M ≥ 6 km, neglect of non-Lambertian reflection produces an error in determining the reflectance of no higher than 20.3%, neglect of non-Lambertian reflection in the formation of adjacency effect and additional illumination results in an error of no more than 12%, and neglect of non-Lambertian reflection in additional illumination, of no more than 1.4%. For more clear situations ( S _M ≥ 6 km), the maximal error for similar models does not exceed 92, 14, and 1.2%, respectively. For solar zenith angles θ_sun ≤ 60° and angles of the optical axis of the receiving system θ_sun ≤ 60°, the errors do not exceed 30, 7.5, and 1%, respectively. The results prove the possibility of considering non-Lambertian reflection after taking into account adjacency effect and additional illumination of the ground surface in the Lambertian reflection approximation.

Interest in understanding the influence of forest ecosystems on the formation of climate parameters continues to grow. This paper examines two approaches to the study of interaction between Siberian forests and the atmosphere. Based on the results of the analysis, it was suggested that the formation of a 4-year cycle in precipitation over forest areas may occur with the participation of tree transpiration. This finding will help us to understand the emergence of similar cyclical patterns in meteorological data from other regions with extensive forest ecosystems. The results may be useful for specialists dealing with problems of biosphere-atmospheric interaction.

A dielectric mirror with high reflectance at a wavelength of 266 nm has been designed for use in ultraviolet lidar systems for ozone concentration monitoring. A multilayer interference coating based on HfO₂ and SiO₂ was manufactured and optimized using experimentally obtained dispersion data. The effect of thermal annealing on the optical properties of the coating was investigated, and a temperature limit was identified, excess of which leads to structural degradation. The results can be used in the design of highly efficient optical elements for ultraviolet differential absorption lidars, as well as other laser systems which require UV dielectric mirrors.

It is known that the formation of vortex structures in a fire negatively impacts the consequences: swirling high-temperature flows of combustion products cause greater destruction than a normal fire. Identifying such vortices is a pressing issue. For this purpose, in the big aerosol chamber of the Institute of Atmospheric Optics SB RAS, two isopropanol flame plumes were simultaneously studied by the thermal imaging method. One of them was a vortex flame obtained by blowing around a stationary container installed on the axis of an ascending swirling air flow, and the other was in a container without blowing. Using the fast Fourier transform (FFT) of the time pulsations of the thermal imaging signal, the power spectra of the pulsation frequencies were calculated. In the calculated spectra, a frequency interval was determined where a significant difference between the mentioned flames was observed. The influence of distance and the averaging effect of the size of the initial region of thermal imaging signal reception on the difference in flame spectra was analyzed.

The article presents the results of a study of the problem of propagation regimes of narrow (millimeter) laser beams in a Kerr-nonlinear turbulent medium, which is a model of evolution of the light inhomogeneities generated at multiple filamentation of high-power laser pulses in the corresponding media. We used methods of diffraction beam tubes and diffraction beams in the theoretical study. It was found that there are three propagation regimes for laser beams with certain parameters in a turbulent medium: self-focusing with generation of a nonlinear focus (beam collapse), self-channeling over a limited distance, and turbulent propagation. An analytical relationship for the square of the beam's effective radius was derived, which is of interest for practical applications in nonlinear atmospheric optics.

This work is devoted to the development and experimental verification of effective methods for compensating for the dynamic atmospheric distortions of a laser beam propagating through a turbulent medium. The paper presents the results of a laboratory experiment on the correction of wavefront distortions of laser radiation propagating along a turbulent path in a pavilion. Turbulence was simulated using a fan heater supplying warm air perpendicular to the beam propagation. Distortion compensation was performed using an adaptive optics system, including a wavefront tilt corrector and a bimorph deformable mirror. The system efficiency was assessed by analyzing the far-field intensity distribution. It is shown that the generated turbulent distortions are spectrally similar to Kolmogorov turbulence with a bandwidth of about 30 Hz. It is found that for effective compensation of wavefront aberrations, the operating frequency of the adaptive optics system should be 20-30 times higher than the turbulence bandwidth. At a system operating frequency of 1 kHz, the beam divergence was reduced to 1.4 of the diffraction limit, and by increasing the frequency to 2 kHz, a beam stabilization accuracy of 5 mrad can be achieved using an FPGA. The results of this work can be used to design high-performance systems related to the propagation of laser radiation in a turbulent medium.

This article presents an improved internet-accessible expert system, SLON, for analyzing high-resolution molecular spectra. It was developed in the Laboratory of Molecular Spectroscopy at Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. The SLON expert system is based on a neural network model capable of making independent decisions when analyzing combination differences formed by groups of molecular transitions from different rotational sublevels of the ground state to the same excited vibrational-rotational state. The set of features by which the neural network distinguishes the correct variant of a combination difference from random realizations has been improved. Restrictions on the size of the analyzed spectrum have been removed. The format of the databases used is now universal and enables expanding the class of molecules under study. A modern multi-platform user interface allows this program to be compiled for Windows and Linux systems. The operating principles, operational experience, and prospects for the development of the created expert system are described.