Simultaneous infrared detection of the ICH2OO radical and Criegee intermediate CH2OO: the pressure dependence of the yield of CH2OO in the reaction CH2I + O2.

Abstract

The simplest Criegee intermediate CH2OO, important in atmospheric reactions, has been recently produced from the reaction of CH2I + O2 and detected with various methods. In this reaction, the yield of CH2OO decreases with increasing pressure because of the stabilization of the adduct ICH2OO, but no definitive spectral identification of ICH2OO has been reported. We recorded the infrared spectrum of ICH2OO using the same reaction under high pressure; the spectrum agrees with that simulated according to theoretical predictions. With direct detection of both CH2OO and ICH2OO, we determined the pressure dependence of the yield of CH2OO. The yield of CH2OO near 1 atm is greater than previously reported values, which might have significant consequences in atmospheric chemistry.