The effect of Criegee-intermediate scavengers on the OH yield from the reaction of ozone with 2-methylbut-2-ene

The yield of OH from the gas-phase reaction of ozone with 2-methylbut-2-ene has been measured in the presence of various molecules (H2O, SO2, butanone, and acetic acid) that can act as scavengers for the Criegee intermediates (CIs) formed in the reaction. No discernible difference is observed between experiments carried out in the presence and absence of these scavengers. The results indicate that the thermal decomposition of CIs that give OH radicals is fast compared with their bimolecular reaction with the scavengers under the conditions of the experiments. Combined with the results of a recent time-resolved study, upper limits (in units of cm(3) molecule(-1) s(-1)) were determined for the bimolecular reactions of the CI with H2O (1 x 10(-16)), SO2 (4 x 10(-15)), butanone (2 x 10(-14)), and acetic acid (1 x 10(-14)). The results imply that these reactions are too slow to inhibit OH formation in the ozonolysis of alkenes and that the currently recommended OH yields can be used in models of atmospheric chemistry.