Detection of the [FORMULA][F][RM]N[/RM][SUP]+[/SUP][INF]2[/INF][/F][/FORMULA] First Negative System in a Bright Leonid Fireball

Abstract

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 N2+ B 2Σ u+ → X 2Σg+ bands in the UV meteor spectrum. The N2+ temperature was estimated to be 10,000 K with a low number density of 1.55 × 10 5 cm-3. Such unexpectedly strong ultraviolet emission, in particular for N2+ (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 N2+.