15min:
POSSIBLE OBSERVATION OF THE 3A' - 1A' ELECTRONIC TRANSITION OF THE METHYLENE PEROXY CRIEGEE INTERMEDIATE.

NEAL D. KLINE AND TERRY A. MILLER, Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210; MARC COONS AND JOHN HERBERT, Department of Chemistry, The Ohio State University, Columbus, Ohio 43210.

It is possible that we have observed for the first time the transition from the ground 1A' state to the low lying 3A' state of the methylene peroxy Criegee intermediate, CH2O2, which is otherwise known as carbonyl or formaldehyde oxide. Criegee intermediates are reactive intermediates that are formed in the ozonolysis of olefins in both liquid and gaseous phases with the methylene peroxy intermediate being formed specifically from the ozonolysis of ethene. In the atmosphere Criegee intermediates are formed in reactions that lead to secondary organic aerosols and participate in reactions with SO2 and NO2. A peroxy-like spectrum was observed in the near-IR using cavity ringdown spectroscopy after photolysis of a diiodomethane precursor at 248 nm followed by a reaction with O2. Possible assignment of the spectrum to CH2O2 is based on a strong analogy between the electronic structure of methylene peroxy and ozone. However experiments and electronic structure calculations are continuing to positively attribute the spectrum to either CH2O2 or CH2IO2 which could also be formed by this chemistry.