ABSOLUTE CHEMILUMINESCENT REACTION RATES FOR EMISSION OF O2 HERZBERG BANDS IN OXYGEN AND OXYGEN-INERT-GAS AFTERGLOWS

Chemiluminescent reaction rates for emission of the O2 Herzberg bands in the O2 and O2+ or Ar afterglows have been measured in a discharge-flow system. Absolute intensities were measured between 260.0 and 420.0 nm at 0.5-nm resolution with a scanning spectrometer, and oxygen-atom densities were determined by NO2 titration. Intensities were obtained as a function of atom density, O2 pressure, and partial pressures of added nonreactive gases. The integrated intensity of the Herzberg band system is proportional to [O]2 and independent of O2 pressure between 1 and 10 torr. The A 3∑u+ state of O2 is quenched by groundstate O2, and the Herzberg bands are stronger in mixtures of O2 with He or Ar than in pure O 2. The chemiluminescent reaction rate coefficient is 2.5×10-21 cm3/sec in O2 and is larger by about a factor of 10 in He or Ar. The vibrational population distribution is shifted to lower vibrational levels of O2(A 3∑u +) in the O2-inert-gas mixtures than in pure O 2.