Informative wavelengths for trace atmospheric gas sounding with an OPO-lidar in the 3–4 μm spectral region

In this work, a search for information-bearing mid-IR wavelengths for HCl and HBr sounding with a differential absorption lidar based on an optical parametric oscillator has been carried out. Lidar echo signals have been calculated at the wavelengths chosen during sounding of gas components along vertical paths 0–5 km long. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Reconstruction of N2O and CH4 content by dial measurements at wavelengths of overtone CO laser

The paper presents the results of laboratory experiments on measurement of absorption and extinction of radiation of the overtone СО laser at wavelengths used for sensing of methane and N2O in the mid-IR spectral range with the differential absorption (DIAL) method, as well as the concentrations of the studied gases reconstructed from the analysis of experimentally obtained absorption coefficients

Lidar measurements of ozone in the upper troposphere - lower stratosphere at Siberian lidar station in Tomsk

The paper presents the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station. Sensing is performed according to the method of differential absorption and scattering at wavelength pair of 299/341 nm, which are, respectively, the first and second Stokes components of SRS conversion of 4th harmonic of Nd:YAG laser (266 nm) in hydrogen. Lidar with receiving mirror 0.5 m in diameter is used to implement sensing of vertical ozone distribution in altitude range of 6-16 km. The temperature correction of zone absorption coefficients is introduced in the software to reduce the retrieval errors

OPO-laser system for atmospheric sounding in the MID-IR range

A laser system is designed that provides for tunable generation of nanosecond radiation pulses in the 3–4 μm range. Optical block-diagram and specifications of the system are presented. The laser system as a part of a differential absorption lidar designed can be used for remote control of pollutant concentrations along surface atmospheric path

Measurement of ozone concentration in the lower stratosphere - upper troposphere

We describe an ozone lidar and consider an algorithm for retrieving the ozone concentration, taking into consideration the aerosol correction. Results of lidar measurements at wavelengths 299 and 341 nm well agree with model estimates, indicating that ozone is sensed with acceptable accuracies in the altitude range of about 6-18 km. It should be noted that the retrieved profiles of altitude distribution of ozone concentration more closely resemble those from satellite data than according to Krueger model. A lidar is developed and put into operation at Siberian Lidar Station (SLS) to measure the vertical ozone distribution (VOD) in the upper troposphere-lower stratosphere. Sensing is performed according to the method of differential absorption and scattering at wavelength pair 299/341 nm, which are respectively the first and second Stokes components of stimulated Raman scattering (SRS) conversion of the fourth harmonic of Nd:YAG laser (266 nm) in hydrogen

Spatial Pattern Formation in External Noise: Theory and Simulation

Spatial pattern formation in excitable fluctuating media was researched analytically from the point of view of the order parameters concept. The reaction-diffusion system in external noise is considered as a model of such medium. Stochastic equations for the unstable mode amplitudes (order parameters), dispersion equations for the unstable mode averaged amplitudes, and the Fokker-Planck equation for the order parameters have been obtained. The developed theory makes it possible to analyze different noise-induced effects, including the variation of boundaries of ordering and disordering phase transitions depending on the parameters of external noiseComment: 22 pages, 10 figure

DIAL measurements of the vertical ozone distribution at the Siberian lidar station

The paper presents the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station. Sensing is performed according to the method of differential absorption and scattering at wavelength pair of 299/341 nm, which are, respectively, the first and second Stokes components of SRS conversion of 4th harmonic of Nd:YAG laser (266 nm) in hydrogen. Lidar with receiving mirror 0.5 m in diameter is used to implement sensing of vertical ozone distribution in altitude range of 6-16 km. The temperature correction of zone absorption coefficients is introduced in the software to reduce the retrieval errors

Electron correlation effects in electron-hole recombination in organic light-emitting diodes

We develop a general theory of electron--hole recombination in organic light emitting diodes that leads to formation of emissive singlet excitons and nonemissive triplet excitons. We briefly review other existing theories and show how our approach is substantively different from these theories. Using an exact time-dependent approach to the interchain/intermolecular charge-transfer within a long-range interacting model we find that, (i) the relative yield of the singlet exciton in polymers is considerably larger than the 25% predicted from statistical considerations, (ii) the singlet exciton yield increases with chain length in oligomers, and, (iii) in small molecules containing nitrogen heteroatoms, the relative yield of the singlet exciton is considerably smaller and may be even close to 25%. The above results are independent of whether or not the bond-charge repulsion, X_perp, is included in the interchain part of the Hamiltonian for the two-chain system. The larger (smaller) yield of the singlet (triplet) exciton in carbon-based long-chain polymers is a consequence of both its ionic (covalent) nature and smaller (larger) binding energy. In nitrogen containing monomers, wavefunctions are closer to the noninteracting limit, and this decreases (increases) the relative yield of the singlet (triplet) exciton. Our results are in qualitative agreement with electroluminescence experiments involving both molecular and polymeric light emitters. The time-dependent approach developed here for describing intermolecular charge-transfer processes is completely general and may be applied to many other such processes.Comment: 19 pages, 11 figure