Reactions involving fast nitrogen atoms are of importance both in the upper atmosphere and in defining the near-field environment around orbiting spacecraft. We present the first quantitative study of the distribution of vibrationally excited ground state NO produced in the reaction of 8 km/s N atoms with O2. A pulsed beam of energetic nitrogen atoms was interacted with thermal oxygen molecules under single-collision conditions in a crossed beam configuration. The fundamental and first overtone band emissions of the reaction product NO (X2&Pgr;) were measured using both band-pass-filtered radiometers and a circular variable filter. The spectrally resolved emissions were analyzed to determine the nascent NO vibrational distribution and the vibrational state-specific reaction cross sections. The present results are compared with earlier measurements performed at thermal energies and contrasted with theoretical predictions. ¿ 2000 American Geophysical Union