Phys. Chem. Chem. Phys.

Primary product channels in the reaction of the hydroxyl radical (OH) with acetaldehyde (CH3CHO) were quantified using the method of pulsed laser photolysis combined with direct detection of acetyl (CH3CO) and methyl (CH3) radicals by transient absorption spectroscopy, and H-atoms by resonance uorescence. Upper limits of 0.03 for a reaction pathway leading to formation of CH3 + HCOOH at 298 K, and 0.02 for a pathway to H + CH3C(O)OH (220-298 K) were determined. The major reaction pathway is formation of CH3CO + H2O, with a yield of (0.93 +/- 0.18). In the course of this study absorption cross-sections of CH3 and CH3CO radical were also determined as sigma(CH3) = (3.7 +/- 0.3) x 10(-17) cm(-2) at 216.4 nm (0.75 nm resolution) and sigma(CH3CO) = (1.4 +/- 0.2) x 10(17) cm(2) at 220 nm