Photolysis of Nitrogen Dioxide at 3660 and 4047 Å at 25°C

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Nitrogen dioxide was irradiated at 3660 and 4047 Å at various pressures of NO2, with and without CO2, NO, and N2 as added gases. The data indicate a primary dissociation at 3660 Å and shorter wavelengths corresponding to energies greater than the ON–O bond energy. At 4047 Å, the data are explained by an excited-molecule mechanism. Isotopic oxygen scrambling experiments at 4047 Å indicate the probability of reactions to produce oxygen atoms at that wavelength, but photolysis of NO2 at trace concentrations and high inert-gas pressures indicates that these atoms are not derived from the unimolecular decomposition of the photoactivated molecule. The inhibition of the quantum yield by NO addition was pressure-dependent, lending further support to the premise that oxygen atoms are important in the mechanism at 4047 Å. It is postulated that the reaction NO2*+NO2→N2O3+O is the source of atomic oxygen.