Absorption cross section determination of biogenic C5-aldehydes in the actinic region

Abstract

UV absorption cross sections ( σ λ ) for 3-methylbutanal, trans-2-methyl-2-butenal, and 3-methyl-2-butenal have been determined between 255 and 390 nm and as a function of temperature (273–305 K). A D 2 lamp and a 0.5 m spectrograph coupled to a charged-couple device were employed in these measurements. σ λ values were found to be independent of temperature in the range studied. The cross section data reported in this Letter were used to provide estimates of the photolysis rate coefficients ( J i ) for these compounds as a function of altitude in the troposphere. Photolysis and OH reaction both appear to be important in determining the atmospheric fate of these compounds.