The present paper aims at ab initio and laboratory evaluation of the N 2 collision-induced absorption band intensity arising from interactions between N 2 and H 2 O molecules at wavelengths of around 4 mm. Quantum chemical calculations were performed in the space of five intermolecular coordinates and varying N−N bond length using Møller-Plesset perturbation and CCSD(T) methods with extrapolation of the electronic energy to the complete basis set. This made it possible to construct the intermolecular potential energy surface and to define the surface of the N−N dipole derivative with respect to internal coordinate. The intensity of the nitrogen fundamental was then calculated as a function of temperature using classical integration. Experimental spectra were recorded with a BOMEM DA3-002 FTIR spectrometer and 2 m base-length multipass White cell. Measurements were conducted at temperatures of 326, 339, 352 and 363 K. The retrieved water-nitrogen continuum significantly deviates from the MT_CKD model because the relatively strong nitrogen absorption induced by H 2 O was not included in this model. Substantial uncertainties in the measurements of the H 2 O−N 2 continuum meant that quantification of any temperature dependence was not possible. The comparison of the integrated N 2 fundamental band intensity with our theoretical estimates shows reasonably good agreement. Theory indicates that the intensity as a function of temperature has a minimum at approximately 500 K.

Three main spectral components ∼ 3210, 3450, and 3650 cm-1 separated by deep gaps in the Raman OH band of liquid water have been detected by a new treatment procedure of experimental data. The applied treatment is based on the statistics of the fractional moments. This approach includes the consideration of the total set of the moments (the fractional and even complex ones) and the generalized mean value functions (GMV) as a specific noise ``label''. The possibility of the extraction and quantitative description of the fine structure of the averaging experimental spectra is demonstrated. In the frame of the novel approach the reliable separation between Raman spectra of the distilled and Milli-Q water is obtained.

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A new generation lidar (LIght Detection And Ranging) based on a diode laser with eye-safe energy density (~10 nJ cm−2) and a single photon avalanche photodiode was used for the first time, to our knowledge, to detect clouds along the Garabashi glacier near the Elbrus mountain summit. We have observed single- and multilayered clouds near the Elbrus volcano summit from the Garbashi camp located at a 4 km distance. A high signal-to-noise ratio demonstrated the potential of the remote sensing of aerosols from distances of up to 10 km.

We carried out a remote study of ship wakes by optical methods. Both Mie and Raman scattering signals and their evolution were simultaneously recorded by gated detector (intensified CCD). The Mie scattering signal was detectable within 1 min after water disturbance by a high-speed boat. According to an approximation of experimental data, Raman signal fluctuations can be detected for a much longer time under the same conditions. We have demonstrated that Raman spectroscopy is substantially more sensitive to water perturbation compared to conventional acoustic (sonar) technique and can be used for ship wake detection and monitoring.