Explanation of anomalous ratio of atomic and molecular features in spectra of Benešov meteor by laboratory modeling in laser-induced plasmaтезисы доклада
Дата последнего поиска статьи во внешних источниках: 8 апреля 2022 г.
Аннотация:One of the actual problems of cosmochemistry is the study of combustion processes of objects entering the upper layers of Earth’s atmosphere. During these processes, plasma is formed resulting in complicated spectra containing both atomic and molecular emission. In order to understand how the composition of a meteor changes when entering the Earth's atmosphere, it is necessary to study the atomic and molecular emission spectra of burning meteors. Such spectra were obtained for the Benešov meteor at various heights1. However, direct observations of meteor spectra it is extremely difficult and inconvenient, so development of laboratory modeling seems to be a promising field of study. Due to the wide ranges of available temperature (from 0.2 to 4 eV) and electron number density (10^15 - 10^19 cm-3) it can be used as a laboratory object for studying radiation from various sources in outer space. Thus, the purpose of this work is to study the atomic and molecular emission spectra of laser-induced plasma to explain the atomic and molecular features in the spectrum of the Benešov meteor.Since the atomic lines of calcium and iron, as well as CaO and FeO bands are distinctly observed in the meteor spectra, CaCO3 and Fe3O4 were used as solid targets for the formation of laser-induced plasma. We obtained spectra of molecular bands at a set of pressures corresponding to different heights of observation of the Benešov meteor. However, the intensity ratios in laboratory spectra did not correspond to the intensity ratios in the Benešov spectra. This allowed us to assume that the pressure in the gas-plasma cloud does not correspond to the atmospheric pressure at the heights of the meteor observation, which is most likely associated with the formation of a shock wave in front of the meteor. To obtain laboratory spectra that would correspond to the meteor ones, the pressure was varied in the range from 0.16 to 32 Torr. In each case plasma temperature was calculated by construction of Boltzmann plot with 20 to 30 atomic lines. Also, we estimated electron number density by Saha-Boltzmann plot where possible. For some cases, we managed to find the conditions under which the laboratory spectra have the highest similarity to the Benešov ones. Furthermore, study of the relative intensities of molecular bands at different pressures allows us to claim that the intensity of the FeO band is almost independent of pressure, while the intensity of the CaO band have strong dependency.
