Absolute Chemiluminescent Reaction Rates for Emission of the 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 + He 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 $A^3{\Sigma }_u^{+}$ state of O₂ is quenched by ground‐state O₂, and the Herzberg bands are stronger in mixtures of O₂ with He or Ar than in pure O₂. 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 ${\mathrm{O}}_2{\mathrm{(A}}^3{\Sigma }_u^{+})$ in the O₂–inert‐gas mixtures than in pure O₂.