A kinetic study of the CHOO Criegee intermediate reaction with SO, (HO), CHI and I atoms using OH laser induced fluorescence.

The OH laser induced fluorescence method was used to study the kinetics of CHOO reacting with SO, (HO), CHI and I atoms. Decay of CHOO is not strictly first-order since its self-reaction is rapid. With this consideration, we derived the rate coefficient of CHOO + SO/(HO)/CHI/I taking into account the contribution of the CHOO self-reaction. For the CHOO + SO reaction, the rate coefficient is measured to be (3.88 ± 0.13) × 10 cm molecule s at 10 Torr, which agrees very well with a previously reported value obtained by directly monitoring CHOO using the UV absorption method with the CHOO self-reaction considered. We did not observe obvious evidence for SO catalysed CHOO isomerization or the intersystem crossing effect in this reaction. CHOO + (HO) is supposed to account for the major sink of CHOO in the atmosphere, but previous rate coefficient measurements were not in good agreement. We have revisited this reaction including the self-reaction of CHOO and obtained the rate coefficient to be (7.53 ± 0.38) × 10 cm molecule s at 60 Torr and 300 K. The rate coefficients of CHOO + CHI and CHOO + I were measured to be (5.2 ± 2.6) × 10 and (2.2 ± 1.1) × 10 cm molecule s respectively.