Quantum yields for the near U-V photolysis of alkyl nitrites - relevant to atmospheric chemistry
The main objective of this work was to determine the quantum yields for the production of alkoxy radicals via the near U-V photolysis of alkyl nitrites. Alkoxy radical reactions, including their isomerization, are important in both clear and polluted atmospheres. Alkyl nitrites were used as a photolytic source of alkoxy radicals (1). The extent of the of photolysis for the nitrites was determined by measuring the yield of either ketone or aldehyde product produced from the decomposition of the alkoxy radical, as a result of the dissociation of the nitrite concerned. Experiments were carried out at elevated temperatures (393K) in order to ensure that every alkoxy radical that was formed, dissociated via reaction (3), rather than recombine with nitric oxide to reform the nitrite (2). Care was taken to search for any other products via the primary step. RONO = (+ hv) RO &43 NO (1); RO + NO &61 RONO (2); RO = Products (Ketone or Aldehyde) (3) The experimental determination of azomethane, t-butyl, s-butyl, t-pentyl and 2-pentyl nitrite molecular electronic absorption spectrums were carried out using ultraviolet and near ultraviolet spectrophotometry (U.V.). Spectrophotometric measurements were made using certain nitrite pressure at 393 K with a 9.3 cm length cell. The average absorption at each nanometer of 5 runs were plotted against the absorption range (328 - 383 nm). The absorption cross section (σ) and the absorption rate (J_a) for the azomethane and the four nitrites were measured and calculated in the range 328 - 283 nm and at 393 K.