The absorption of solar UV radiation by carbonyl oxide radicals (also known as Criegee intermediates) such as CH3CHOO may have a significant impact on the concentrations of O(1D), OH and other species in the atmosphere. The absorption of CH3CHOO at 308 nm and 352 nm was measured by laser depletion in a jet-cooled molecular beam. The absorption cross sections were determined with improved accuracy over previous work1 using two methods: by comparing the depletion of a reference molecule, CH3CHI2, and by characterizing the absolute laser fluence with a laser beam profiler. The cross section at 308 nm was found to be (1.10�0.05)�10-17 cm2 molecule-1, and at 352 nm was found to be (9.66�0.46)�10-18 cm2 molecule-1. The absorption spectrum of CH3CHOO was also measured by transient absorption in a flow cell, and the rate coefficient for its reaction with SO2 was determined. This work represents the most accurate direct measurements of CH3CHOO UV absorption to date. The results provide a spectral signature for identification of this elusive intermediate, and will improve estimates of Criegee intermediate photolysis and reaction rates in the atmosphere.J. Beames, F. Liu, L. Lu, M. Lester, J. Chem. Phys. 138  (2013), 244307

Kinetics and absolute UV absorption spectrum of a methyl substituted Criegee intermediate CH<sub>3</sub>CHOO

248th National Meeting (2014)

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Kinetics and absolute UV absorption spectrum of a methyl substituted Criegee intermediate CH3CHOO

Kinetics and absolute UV absorption spectrum of a methyl substituted Criegee intermediate CH₃CHOO