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29 January 2002 Influence of aerosols on propagation of intensive pulses of a CO2-laser of microsecond duration in the near-surface atmosphere
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The results of the field experiments on propagation of intensive pulses of CO2- laser on the near surface atmospheric path have been discussed. The data are given on non-linear aerosol scattering, luminescence of aerosol particles and plasma in a light beam and their influence on the beam characteristics. The field experiments have shown that the optical breakdown and thermal luminescence of aerosol particles are possible under the effect of the CO2-laser pulses. The heating aerosol particle up to the temperature, when the developed evaporation is occurred, yet does not guarantee the appearance of the plasma initiation core, which is capable to evolve in the regime of light detonation. At the thermal mechanism of development of equilibrium plasma the luminescence intensity maxims in different ranges of the spectrum coincide in time and occur after a maximum of an effecting pulse. The intensity fluctuations in the beam at the beginning of the pulse do not result in the luminescence fluctuations, which arise only to the end of a pulse. It testifies to an essential role of energy of a line-transmitted spectrum of the luminescence core, i.e., not too high temperatures (T approximately 103 K) and the pressures achievable at absorption by particles of energy of the initiating pulse. The thermal blooming of luminescent particles are new radiation sources with dimensions, exceeding the size of aerosol particles by two orders that results in the 104 increase of the scattering radiation. The essential part of the laser energy scattered on these blooming, as well as on shock waves, will be concentrated in a narrow angle in a forward direction, as their dielectric constant is less, than it is for aerosol particles. The measured aerosol scattering coefficient is higher than the calculated linear coefficient by one order. It is shown, that the overcondensation at explosive destruction of a water aerosol by fragments can also result in the considerable increase of scattering for specific meteorological situations.
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Liliya K. Chistyakova "Influence of aerosols on propagation of intensive pulses of a CO2-laser of microsecond duration in the near-surface atmosphere", Proc. SPIE 4538, Optics in Atmospheric Propagation and Adaptive Systems IV, (29 January 2002);

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