DETECTION OF THE N_2~+ FIRST NEGATIVE SYSTEM IN A BRIGHT LEONID FIREBALL

摘要

An ultraviolet-visible spectrum between 300 and 450 nm of a cometary meteoroid that originated from 55P/ Tempel-Tuttle was investigated, and its new molecules, induced by atmospheric interaction, were discovered. The spectroscopy was carried out using an intensified high-definition TV camera with a slitless reflection grating during the 2001 Leonid meteor shower over Japan. A best-fit calculation mixed with atoms and molecules confirmed the first discovery of N_2~+ B~2∑_u~+ → X~2Σ_g~+ bands in the UV meteor spectrum. The N_2~+ temperature was estimated to be 10,000 K with a low number density of 1.55 x 10~5 cm~(-3). Such unexpectedly strong ultraviolet emission, in particular for N_2~+ (1, 0) at 353.4 nm, is supposed to be formed through the wide dimensions of high-temperature regions caused by a large meteoroid. Spectroscopic observations of reentry capsules will provide us with good opportunities for confirming the discovered N_2~+.