LASER-INDUCED FLUORESCENCE DECAY LIFETIMES OF SHOCK-HEATED NO (A2-SIGMA+)

Radiative emission in the NO gamma-band system occurs when air at a few Torr initial pressure is shock-heated at sufficiently high temperatures of 3500-7000 K. Emission spectra of this system in shocks indicate that collisional quenching of the emitting A2-SIGMA+ state is a critical quantity controlling the intensity. Quenching of excited NO by NO itself has been measured using direct time decay of laser-induced fluorescence in the shock tube at 3500 K. The cross section (2 - sigma-error) is 59 +/- 20 angstrom 2, compared to the room temperature value 37 +/- 8 angstrom 2. At 3500 K, N2 also quenches NO with a cross section approximately 2 angstrom 2, much larger than the value at 300 K. PACS: 34.50Gb