ИСТИНА

The column density as well as the temperature of the metal oxides of astrophysical interest (CaO, FeO and etc.) are crucial important for the quantitative insight of radiation transfer and chemical evolution processes during meteor events in Earth’s atmosphere. To determine both concentration and temperature by means of electronic spectra the energetic and radiative properties of the excited states are indispensably required. In contrast to the other metal oxides the quantitative simulation of the iron oxide (FeO) emission is not feasible due to extremely condensed and strongly perturbed structure of the excited rovibronic states. To extract the FeO fraction from orange bands of meteor spectra, the laboratory FeO spectra (West and Broida) were implemented by Berezhnoy et al.. However, these chemiluminescence spectra were produced at low temperature (700 K) while the temperature of molecules in impact-produced clouds is estimated to be 3000~4000. Such high temperatures can be readily achieved in the framework of laser ablation experiments. In the present work we studied a timeevolution of the laser-induced breakdown spectra (LIBS) of pure metals. The measurements at reduced pressure were also performed. We used Q-switched Nd:YAG laser for plasma ignition on the target and Czerny-Turner spectrometer with ICCD camera. We used atomic lines for temperature calculation by Boltzmann plot technique as well as experimental spectra fitting, and electron density calculation by Stark broadened lines. We prove the adequacy of temperature evaluation by comparison of experimental and synthetic spectra for a wellstudied AlO molecule. We also tried to assign the orange system of FeO, and we assumed that the long wavelength part (620-640 nm) can be associated with FeO2 molecule. The laboratory orange bands spectra corresponding to the translation temperature of 3000-3500 K are found to be most close to their astronomical counterparts while the very weak LIBS emission still observed at lower temperature becomes more similar to the chemiluminescence Fe+O2 spectra produced by West & Broida.