Nitrogen pentoxide photolysis

Irradiation of gaseous formaldehyde containing an excess of nitrogen dioxide over chlorine yielded ozone, carbon monoxide, nitrogen pentoxide, nitryl chloride, nitric and hydrochloric acids. Peroxynitric acid was the major photolysis product when chlorine concentration exceeded the nitrogen dioxide concentration (Hanst and Gay, 1977). Formaldehyde also reacts with NO3 in the atmosphere at a rate of 3.2 x 10 cmVmolecule-sec (Atkinson and Lloyd, 1984). 

Tuazon et al. (1984a) investigated the atmospheric reactions of TV-nitrosodimethylamine and dimethylnitramine in an environmental chamber utilizing in situ long-path Fourier transform infared spectroscopy. They irradiated an ozone-rich atmosphere containing A-nitrosodimethyl-amine. Photolysis products identified include dimethylnitramine, nitromethane, formaldehyde, carbon monoxide, nitrogen dioxide, nitrogen pentoxide, and nitric acid. The rate constants for the reaction of fV-nitrosodimethylamine with OH radicals and ozone relative to methyl ether were 3.0 X 10 and <1 x 10 ° cmVmolecule-sec, respectively. The estimated atmospheric half-life of A-nitrosodimethylamine in the troposphere is approximately 5 min. 

Figure 20. Effect of nitrogen pentoxide on photolysis of nitrogen dioxide in oxygen...

If some other reactant was introduced into the system to remove nitric oxide in competition with the ozone-nitric oxide reaction, it was predicted that the ozone would accumulate. Nitrogen pentoxide was found to produce the predicted effect photolysis of the nitrogen dioxide-nitrogen pentoxide-oxygen system yielded substantial quantities of ozone. 

At night, the concentration of NO decreases rapidly to low values, and photolysis also ceases. Under these conditions the main fate of NO3 is the association with NO2 to form nitrogen pentoxide... 

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