Rate Constant Ratios During Nitrogen Dioxide Photolysis

Abstract

Nitrogen dioxide is the light absorber in the hydrocarbon system leading to production of photochemical air pollution. Studies of the reactions involved are based on the kinetics of nitrogen dioxide photolysis and the values of the rate constants derived therefrom. The photolysis of nitrogen dioxide was investigated in the 2-20 ppm concentration range. The value of the bimolecular rate constant of the reaction between oxygen atoms and nitrogen dioxide was calculated to be 5.26 × 10⁹1 mole^–1 sec^–1, and thetermolecular rate constant of the reaction between oxygen atoms and nitrogen dioxide in presence of a third body is 4.24 × 10^–10 1²mole^–2 sec^–1. The rate constant for the reaction between oxygen atoms and nitric oxide in the presence of a third body was calculated to be 2.31 × 10¹⁰ 1²mole^–2 sec^–1. Nitrogen was used as the third body. In terms of order of magnitude these calculated rate constants are similar to previously reported values. However, in certain cases their use leads to an oxygen atom concentration which is 100% greater than previously calculated.