Effects of Wavelength and Temperature on Primary Processes in the Photolysis of Nitrogen Dioxide and a Spectroscopic—Photochemical Determination of the Dissociation Energy

The quantum yields of oxygen production in the photolysis of nitrogen dioxide have been determined at a series of wavelengths at room temperature and as a function of temperature at 3660, 4047, and 4358 Å. These values were satisfactorily correlated with the extent of dissociation into NO and O atoms by means of 18–18O2 tracer techniques. On the basis of the above correlation and inert gas experiments, a general mechanism is proposed for the photolysis of NO2 from 3130 to 4047 Å. Temperature effects are discussed in terms of a theoretical calculation based on the population of the rotational energy levels of NO2. This leads to a spectroscopic—photochemical determination of the dissociation energy of NO2 in good agreement with that calculated from thermodynamic data.