Active nitrogen has been prepared by the hollow-cathode discharge through N₂ in a flowing af-terglow reactor. Strong emission spectra in the wavelength of 620～820 nm were detected when iodoethane (C₂H₅I) was added to a stream of active nitrogen, and the 35 spectral peaks have been assigned to the vibrational transitions of the NI(b¹Σ^＋→X³Σ^－) band system. The possible formation mechanism of the electronically excited NI(b¹Σ^＋) was proposed to be the reaction of N(²P) in active nitrogen with C₂H₅I based on some quenching ex-periments. This is the first experimental evidence about the excited NI(b¹Σ^＋) generation through chemical reaction in gas phase, and the highest vibrational level detected is v'＝6.

Key words: active nitrogen, flowing afterglow, emission spectra, NI radical