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 unique property combined with the typical range of electron temperature (from 0.2 to 4 eV) and electron number density (1015 - 1019 cm-3) make it a promising emission source for study of radiation from various objects in atmosphere (meteor wake, airglow) and in outer space. We aimed to register spectra of FeO and CaO bands in laser plasma as close as possible to the ones observed during the Benešov bolide event. This kind of laboratory modeling of molecular emission cannot be calculated theoretically and can help to investigate and characterize the particular conditions of the Benešov meteor wake. We obtained emission spectra of laser plasma under different pressures (from 0.16 Torr to atmospheric) and observation times while ablating samples of Fe3O4, CaCO3. In each case plasma conditions were characterized by determining electron temperature via construction of Boltzmann plot with 20 to 30 atomic lines. Electron number density was estimated by Stark broadening 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. We found that the ratios of molecular and atomic components differ greatly in spectra of Benešov and laboratory ones at the same pressure. Varying the pressure of laboratory experiment proves that Benešov wake was formed under 7-10 times higher pressure than the ambient one on the corresponding altitude. Also, 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 is 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. This work was supported by the Russian Science Foundation (grant 18-13-00269-П)