Nitrogen dioxide photolysis quantum yield

Titanium dioxide suspended in an aqueous solution and irradiated with UV light X = 365 nm) converted benzene to carbon dioxide at a significant rate (Matthews, 1986). Irradiation of benzene in an aqueous solution yields mucondialdehyde. Photolysis of benzene vapor at 1849-2000 A yields ethylene, hydrogen, methane, ethane, toluene, and a polymer resembling cuprene. Other photolysis products reported under different conditions include fulvene, acetylene, substituted trienes (Howard, 1990), phenol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitro-phenol, nitrobenzene, formic acid, and peroxyacetyl nitrate (Calvert and Pitts, 1966). Under atmospheric conditions, the gas-phase reaction with OH radicals and nitrogen oxides resulted in the formation of phenol and nitrobenzene (Atkinson, 1990). Schwarz and Wasik (1976) reported a fluorescence quantum yield of 5.3 x 10" for benzene in water. 

The photochemical processes of triatomic molecules have been extensively studied in recent years, particularly those of water, carbon dioxide, nitrous oxide, nitrogen dioxide, ozone, and sulfur dioxide, as they are important minor constituents of the earth s atmosphere. (Probably more than 200 papers on ozone photolysis alone have been published in the last decade.) Carbon dioxide is the major component of the Mars and Venus atmospheres. The primary photofragments produced and their subsequent reactions are well understood for the above-mentioned six triatomic molecules as the photodissociation involves only two bonds to be ruptured and two fragments formed in various electronic states. The photochemical processes of these six molecules are discussed in detail in the following sections. They illustrate how the knowledge of primary products and their subsequent reactions have aided in interpreting the results obtained by the traditional end product analysis and quantum yield measurements. 

Such information can be found in the work of Jaffe and Klein on the photolysis of NO2 in the presence of SO2. They measured the quantum yield of nitrogen dioxide decomposition by in situ NO2 absorptiometry. In the absence of SOj the quantum yield is 2, since each atom of oxygen formed in the primary photolytic process can react with another molecule of NO2... 

Chu, L. and C. Anastasio (2003) Quantum yields of hydroxyl radical and nitrogen dioxide from the photolysis of nitrate on ice. Journal of Physical Chemistry A, 107, 9594-9602 Chyba, C. and C. Sagan (1992) Endogenous production, exogenous delivery and impact-shock synthesis of organic molecules An inventory for the origins of life. Nature 355, 125-132 doi 10.1038/355125a0... 

The formation of oxygen atom 0( P) in the photolysis of nitrogen dioxide (NO2) is the fundamental reaction that causes direct production of O3 in the troposphere. In this section, absorption spectrum and 0( P) production quantum yields relevant to the tropospheric photochemistry are described. 

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