ИСТИНА

Laser-induced plasma is widely used as an emission source for laboratory simulations of different objects. The properties of laser plasma vary significantly depending on the pressure and composition of the environment, as well as during the evolution of the plasma plume. This property combined with the typical range of electron temperature (from 0.2 to 4eV) and electron number density (10^15 - 10^19 cm−3) make it a promising object for study of radiation from various plasma sources in atmosphere (combustion of meteors, airglow) and in outer space. The aim of the present work was to study structure and evolution of CaO and FeO bands in laser plasma under low pressure (0.16 to 32 Torr) that corresponds to the known spectra of Benesˇov bolide. We obtained emission spectra of laser plasma under different pressures and observation times while ablating samples of F e3O4, CaCO3 and chondrite. In each case plasma temperature was calculated by Boltzmann plot method using 20 to 30 atomic lines. We also estimated electron number density by Saha-Boltzmann equation where possible. Study of spatial distribution of emitting atoms and molecules in plasma with precise plasma diagnostics allows to make conclusions about existence or absence of the local thermodynamic equilibrium. The obtained data show that the formation of FeO in plasma occurs with involvement of oxygen from the ablated material, but not from the surrounding atmosphere. On the contrary, CaO if formed primarily using oxygen from atmosphere. Therefore, abundance and of FeO and intensity of its emission in space objects may not depend on the pressure of the surrounding media, while CaO should have a strong dependency.