Shock-Tube Study of the Radiative Combination of Oxygen Atoms by Inverse Predissociation

Absolute emission-intensity measurements of the radiative combination of oxygen atoms O(3P) in the temperature range between 2500° and 3800°K are presented. The emission intensity was recorded simultaneously in six spectral intervals in the wavelength range between 2300 and 4511 Å. The absolute emission intensity was found to be proportional to the square of the oxygen atom concentration and to be characterized by an activation energy of 28.9 ± 2.2 kcal mole− 1. These results are interpreted in terms of an inverse predissociation mechanism in which the oxygen atoms combine along a repulsive potential energy surface with a transition to the B 3Σu− state of molecular oxygen and a subsequent radiative transition to the ground electronic state of oxygen. The rate constant for the over-all radiative combination of oxygen atoms was found to be 4.3 × 106exp(− 28 900 ± 2200 / RT) cm3mole− 1·sec− 1 for the wavelength range 2300–5000 Å.