A. A. Lisenko

A windowless VUV excilamp

An open windowless excilamp capable of operating on argon (λ ∼ 126 nm), krypton (∼146 nm), and xenon (∼172 nm) dimers is described. The lamp has a total radiating surface area of 23 × 23 = 529 cm2. At a total power of ∼0.8 W radiated through this area, the average output power density at λ ∼ 126 nm is ∼1.6 mW/cm2 at a distance of 2 cm from the emitting surface. A pulsed discharge between insulator-coated anode and thin wire cathode ensures a high efficiency of the proposed radiation source operating in the vacuum ultraviolet spectral range.

First results of an integrated experiment on sounding the middle atmosphere in optical and millimeter wavelength ranges (over Tomsk)

Results of joint ground-based microwave and lidar measurements of ozone and temperature vertical profiles are presented. The importance of such observations for the study of the influence of different disturbances on the ozone layer is discussed. The results are compared with the MLS/AURA satellite data and model profiles.

Reabsorption of laser-induced fluorescence in a plant canopy: Stochastic model

This paper continues the series of publications on the statistical simulation of transspectral processes. A system of interrelated radiative transfer equations is proposed. This system gives a formal basis for a numerical analysis of a wider range of spectroscopic effects that accompanies the propagation of laser radiation in the environment, such as the reabsorption of fluorescence in dense disperse media containing two and more fluorophores. As applied to the problem of lidar monitoring of the state of a plant canopy, an optical model is developed in which a leaf is not treated as an individual scattering element, but rather as a local volume of a multiphase medium with a complex polydisperse structure. The Monte Carlo algorithms have been modified so that they have achieved the simulation of fluorescence and reabsorption processes. Test calculations have demonstrated the adequacy of the proposed approach.

Microwave and optical observations of ozone and temperature of the middle atmosphere during stratospheric warming in Western Siberia

We present the results of combined ground-based measurements of vertical ozone and temperature profiles with the use of microwave and lidar instrumentation during stratospheric warming. Marked variations in ozone concentration and temperature in the middle atmosphere are recorded during wintertime warming (December, 2012–January, 2013). The ozone concentration at altitude levels from 25 to 60 km increased by a factor of 1.5–2, with the amplitude of ozone variations substantially increased. The peak of the positive deviation of temperature from the monthly average value reached 70 K at a height of 30 km. The daily variations in ozone at a height of 60 km, associated with sunset and sunrise, were about 30%.

Radiative characteristics of plant leaf

Existing leaf radiation models are reviewed. A new concept of the optical model of the leaf as a multiphase system containing three aggregate ensembles of particles significantly different in microphysical and optical characteristics is proposed. The proposed model is based on the reconstruction of the particle size distribution function from the experimental leaf absorption spectrum. Based on the obtained microphysical model of the plant leaf, the spectra of optical radiation reflection and transmission in the range of 400–800 nm are calculated for various relative concentrations of light-absorbing pigments (chlorophyll a, b and carotenes) and various leaf thicknesses. Optical radiation propagation was simulated using the stochastic Monte Carlo method. The simulation results are in good agreement with relevant experimental spectra.

Numerical simulation of polarization characteristics of an echo signal in the process of ground-based cloud sensing in the terahertz range

Results of numerical statistical simulation of an experiment on ground-based sensing of the cloud layer by linearly polarized terahertz range radiation at several wavelengths from the transmission windows of the atmosphere are presented. The models of the scattering layer involve liquid droplet size distribution functions pooled by results of long-term field experiments in middle latitudes of the Earth, as well as distribution functions obtained in flight measurements near the coast of Great Britain. The models of the scattering medium take into account the vertical stratification of water vapor in the atmosphere and the difference in the microstructure of the cloud layer near its top and bottom.

Experimental study of the interaction between terahertz radiation from the Novosibirsk free-electron laser and water aerosol

Interactions of high-power terahertz radiation from the Novosibirsk free-electron laser at a wave-length of 130 µm in an atmospheric window with a model aerosol cloud with a known droplet size distribution function has been studied experimentally for the first time. The experimental data are compared with theoretical calculation results obtained from solution of the lidar equation for conditions of the experiment.

Lidar equation for a broadband optical range

We have numerically studied the use of a genetic algorithm for reconstructing vertical concentration profiles of trace atmospheric gases from the data of pulsed broadband lidar sounding in a frequency range covering the regions of selective optical absorption of these gases. A generalized form of the lidar equation is proposed that takes into account finite spectral intervals of backscattered radiation. The possibility of using pulsed excilamps of the new generation as sources of radiation for the optical sounding of the atmosphere is demonstrated for the first time. The validity of the proposed approach is illustrated by quantitative examples.

Optical location equation for a super-Gaussian fan ladar

A new modification of the optical location equation is proposed that takes into account the specific features of super-Gaussian fan rays with high homogeneity and, correspondingly, the higher efficiency in problems of remote sensing. A computer program is implemented that simulates the operation of a monostatic ladar in the scheme of transport monitoring.

Carbon monoxide emission in VUV spectral region upon excitation of natural gas by a capacitive discharge

Upon excitation of natural gas by a capacitive electrodeless discharge, an intense excitation of the (4+) band system of CO in the region of 150-200 nm was observed. Excited CO molecules are accumulated as a result of plasmochemical reactions in the gas-discharge plasma. At a pressure of 15 Torr, a pulse repletion frequency of 100 kHz, and a specific excitation power of ~300 mW/cm3, the power density of radiation of the (4+) band system of CO from the external surface of a radiator was ~5 mW/cm2 at an efficiency of up to ~2%.