Home – Home – Jornals – Atmospheric and Oceanic Optics 2016 number 10

Further development of the asymptotic line wing theory is presented where the long-wave approximation for the molecular centers of mass is violated. This provides long molecular trajectories going far beyond an elementary volume in the case of the nonresonance light absorption. The occurrence of long trajectories is evidence of a certain degree of ordering of molecular chaos. The latter can be described by means of a modified semiclassical representation method to establish correlation between displacement and velocity operators. An expression for the absorption coefficient is derived that allows an ambiguity concerning the estimation of the parameters of the potentials to be avoided and the temperature dependence of the absorption coefficient in line wings to be described. The calculations under consideration employ a diffusion model for H₂O absorption in the 3-5 mm window region and for CO₂ absorption in the 4.3 mm band wing to describe the temperature dependence of the absorption coefficient. It is shown that long molecular trajectories significant for the 8-12 and 3-5 mm H₂O window regions can hardly play a role in the 4.3 mm CO₂ band wing.

D₂О absorption spectrum were recorded between 10000 and 11400 cm^-1 by a Fourier transform spectrometer with a spectral resolution of 0.05 cm^-1. A multipass White’s-type cell was used for spectrum measurements, the optical path length was 40 m. A light emitting diode, which provides more brightness in comparison with other radiation sources, was used as a radiation source. Signal to noise ratios of 10⁴ was obtained. During the D₂О spectrum treatment, the experimental line list contained about 100 lines of the n₁ + 3n₃ band was created. Spectroscopic parameters (line positions, intensities, and half widths) were obtained by fitting experimental data to the Voigt line profiles with using least squares method. The analysis of the spectrum allowed us to derive new energy levels belonging to rovibrational state (103).

The absorption spectra of water vapor perturbed by Ar pressure have been investigated in the wavenumber range 6700-7650 cm^-1. Room temperature spectra of water vapor have been measured by the Bruker IFS 125HR Fourier transform spectrometer with a high signal-to-noise ratio in a wide range of pressure of argon with a spectral resolution of 0.01 cm^-1. The fittings with Voigt and speed-dependent Voigt profiles were performed to retrieve the H₂O spectral lines parameters. It was shown that the use of the speed-dependent Voigt profile gives the best agreement with experimental data.

Theoretical broadening coefficients of rotation vibration water vapor lines induced by hydrogen pressure are given. The averaged frequency method has been used to calculate line widths. Calculations have been performed for a wide interval of rotational quantum numbers in the spectral region from 500 to 10 000 cm^-1. Line widths have been computed by the averaged frequency method for rotation quantum number J from 0 to 20, data have been obtained by interpolation of J- dependence for J from 20 to 50. Temperature exponents for line widths have been defined.

Absorption spectrum of carbon oxide confined in nanopores of hybrid SiO₂/Al₂O₃ xerogel has been recorded for the first time. Half-width values of spectral lines was obtained, their dependence on quantum numbers was considered and compared with the data available in literature.

Article belongs to the series of works aimed at improving the performance of radiation codes that implement the statistical Monte Carlo method. A brief description of the main blocks of the two programs for calculating the intensity of solar radiation in a vertically inhomogeneous medium, basis, in FORTRAN, and its optimized version, in the C language, is presented. The results of tests aimed at assessing the performance of each of the code under different conditions of numerical experiment are presented. In the cases examined, the performance indicators of optimized C code were higher as compared with the basis one. It is shown that differences in execution time of the codes are reduced by increasing the optical density of the atmosphere, and using more efficient computers. Developed C program can serve as a basis for creating a high-performance radiation code.

The atmospheric transparency window of 8-12 mm is one of the main spectral intervals forming thermal balance of the atmosphere; at that, the contribution of continual absorption to the radiative balance is the most significant. The results of simulation of upward and downward fluxes for different meteorological situations (cloudy and cloudless) are presented; and role of H₂O continuum is estimated with use of different models of continual absorption.

The paper presents the results of quality assessment of images made using a copper bromide vapor laser monitor. Two different imaging techniques were used for the study: laser illumination and amplification using laser active medium (so called laser monitor). The images were numerically evaluated using the following informative parameters: standard error, Shannon entropy (H), and zero mean normalized cross-correlation (ZNCC). It is shown that use of an active medium introduces into images small distortions, which depend on the stability of amplification properties of the active medium. In the scheme of laser illumination, the influence of instability is less pronounced. The imaging in single-frame mode can decrease the distortions introduced by the active medium.

In laboratory conditions at low pressures of air, corresponding to heights of tens of kilometers above sea level, the apokamp was formed. Apokamp is a plasma jet extending from the spark discharge channel formed by two electrodes, one of which is high voltage and has a positive polarity, and the other is under floating potential. It is established that underpressure apokamp has spectral and morphological features associated with blue jets and starters that observed in the upper layers of the atmosphere.

The influence of gas pressure measurement errors in the chamber of a photoacoustic detector on accuracy of restoration of fast VT-relaxation time of molecules is investigated with the use of numerical simulation of a shape of photoacoustic signal. Using the relaxation of water vapor molecules from the lower excited vibrational state as an example, it is found that for values of the radius of the Gaussian laser beam ω₀ ~ 1 mm, typical in experiments with MK-301 microphone, the relaxation time τ⁰_VT ~ 10^-6 s x mbar can be restored from the dependencies of duration of photoacoustic compression pulse on gas pressure with a relative errors δτ⁰_VT ≤ 10%, if systematic measurement error of pressure does not exceed 0.03 mbar. An error of restoration is directly proportional to the propagation time of sound through the illuminated area.

The content of CO₂ and H₂O in vacuum-extracted tree-ring wood of stem and root discs of certain conifer species was measured. Annual distributions of these gas components were found to exhibit cyclic behavior. Moreover, distinct cyclicity was also revealed in interannual variations of the total pressure of the vacuum-extracted tree-ring gas samples. It may be safely suggested that diffusion of stem CO₂ into the atmosphere will show the same periodic variability. Two hypotheses about the origin of the cyclicity in the tree-ring CO₂ distributions are examined.

Asymptotic solutions of the problem of reconstructing the distribution of the structural characteristics of the refractive index fluctuations from the measurement data of the backscatter enhancement effect are derived. Solutions are expressed through fractional derivatives of the backscattering gain in the case of small aperture receiver, or through the ordinary derivatives in the case of receivers with a large aperture. The properties of the integral equation kernel are studied in detail, from which the asymptotic formulas follow. Attention is drawn to the fact that the kernel is oscillating in general. Kernel oscillations little impact the value of the backscattering enhancement, but their impact can be significant on the derivatives of this factor.

Systematization of information resources in quantitative spectroscopy is demonstrated using the methanol molecule as an example and applying the facilities of the W@DIS information system. The choice of quantum numbers for methanol state is explained and brief descriptions of about 40 publications containing spectral characteristics of methanol are given. The main information objects (data and information source) are defined. The interfaces used for the analysis of wavenumber consistency in all data sources and the interface of application for forming measured line list are described.

The spectrum formation of difference frequency generation between CO₂ and CO lasers radiation is theoretically and experimentally studied in an AgGaSe₂ crystal at I type phase matching. The study shows a promise of this crystal for developing selective laser sources tunable in the wavelength range 12-16.6 microns. Phase-matching angles for difference frequency generation between CO and CO₂ lasers radiation were measured and compared with those calculated by various dispersion equations. The combination of dispersion equations, which describes the difference frequency generation in the wavelength range 12-16.6 μm the most correctly, was chosen.