ИСТИНА

Diatomic molecules are observed in emission spectra of meteorites, bolides due to their interaction with Earth’s atmosphere [1]. These spectra are usually the sources for calculating of meteor content. However, several molecules (such as FeO) have a complex structure of electronic states that is significantly complicated modeling of spectra at various conditions. The main goal of this work is observation of FeO emission spectra in laser-induced plasma and accurate determination of plasma temperature for these spectra. The evolution of the orange system of FeO bands in the range of 540–650 nm with laser-induced iron ablation is studied. The plasma temperature was calculated by Bolzmann plot for Fe I lines in 510-530 nm. Since late stages of plasma expansion are of our interest we have used a set of 35 Fe I lines, which have relatively low excitation potential. It was demonstrated that the structure of the emission spectra of iron monoxide changes greatly when plasma temperature decreases by a factor of ~2 - from 6400 K at 10 µs to 3100 K at 50 µs. Note that atomic iron lines in the spectra are observed for delays of 10-25 µs. Molecular FeO bands explain well the nature of continuous intense background radiation during laser ablation of steels at late observation times in the range of 530-540 nm. Unfortunately, there is still no detailed assignment of all observed bands, except for bands at 591, 611 nm. Comparison of the obtained spectra with the literature data [2] showed a significant difference between them. It is assumed that the spectra of a laser plasma at temperatures above 2000 K will better describe the burning of meteorites observed in the atmosphere. 1. Borovička J., Berezhnoy A.A. Radiation of molecules in Benešov bolide spectra // Icarus, 278 (2016) P.248-265. 2. West J.B., Broida H.P. Chemiluminescence and photoluminescence of diatomic iron oxide // J. Chem. Phys., 62 (1975) P.2566-2574