Abstract. Raman spectra of water within the temperature range 20 to 3 C were investigated. Best of all, the complex shape of the obtained spectra was approximated by four (or five) Gaussian-shaped peaks with their positions 3070, 3230, 3440, 3600 (and 3650) cm -1. The most intensive constituents were 3230 and 3440 cm -1 lines, their total contribution to the Raman spectrum of water is higher than 90%. These lines are the most sensitive to the temperature, too. When the temperature decreases from 20 down to 3 C, the positions of these peaks were shifted from 3232 to 3224 cm -1 and from 3441 to 3434 cm -1 , respectively; and the intensity of 3230 cm -1 line was increased approximately by 14% in its magnitude.

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Simultaneous multi-wave probing by using the differential absorption method could help to unveil fast chemical processes (for example -photo-stimulated) in atmosphere. The scheme of multi-wave finely tuned laser source, suitable for simultaneous probing a few atmosphere constituents and/or chemicals with the above mentioned method, is suggested and tested.

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Compact-sized monopulse excimer laser with foot-print equal to only 250x80 mm 2 , total height 250 mm and beam axis height 50 mm was designed. Output energy at wavelength 308 nm (XeCI* mixture) is 5 mJ, maximal repetition rate -1-2 pulses per second, beam divergence -8 miliradians. Such small foot-print, small axis height of beam in combination with low weight of laser (5 kg) allow them to be used in various optical schemes, where traditional, typical bulky ecximer lasers are unapplicable. Moreover, small dimensions, low weight in combination with low energy consumption (a few Wts)allow them to be used in clear "field" conditions. Beside abovementioned designed laser differs from traditional ones by two sides preionization: "spark" near "hot" massive electrode and so called "capacitive" or "barrier" under ground grid one. Such a two sides preionization provides both igniting and sustaining of wider discharge thus allowing to reach beam with higher simmetry -its cross-section is 15x20 mm 2 .