Ov. Rattigan et al., UV ABSORPTION CROSS-SECTIONS AND ATMOSPHERIC PHOTOLYSIS LIFETIMES OF HALOGENATED ALDEHYDES, Journal of photochemistry and photobiology. A, Chemistry, 112(1), 1998, pp. 1-7
UV absorption cross-sections for CCl3CHO, CCl2FCHO and CCIF2CHO have b
een determined over the wavelength range 200-370 nm and at temperature
s in the range 298-243 K using a dual beam diode array spectrometer. T
he spectra show characteristic absorption due to the n --> pi transit
ion of the C=O group with absorption maxima around 300 nm. On substitu
tion of Cl by F in the CX3 group the absorption maxima showed a shift
to longer wavelengths and a corresponding increase in the intensity of
the absorption in the region of atmospheric photolysis. With decreasi
ng temperature, all three aldehydes showed a small non-negligible decr
ease in the cross-section in the long wavelength tail of the absorptio
n band, and an increase in the cross-section around the absorption max
ima. A two-dimensional photochemical model has been used to calculate
atmospheric lifetimes due to photodissociation and OH radical loss. (C
) 1998 Elsevier Science S.A.