The Lester group is an experimental physical chemistry group, performing research on reactive intermediates that are important in the earth’s atmosphere.

Research in the Lester group is currently focused on the chemistry of Criegee intermediates.  Alkene ozonolysis is an important oxidation pathway for alkenes, which are emitted into the troposphere by both biogenic and anthropogenic sources.  Alkene ozonolysis proceeds through Criegee intermediates, R₁R₂COO, which until very recently had eluded detection.

In the lab, a variety of alkyl-substituted Criegee intermediates, including CH₂OO, CH₃CHOO, (CH₃)₂COO have now been generated by an alternative synthetic route. A diiodo precursor, R₁R₂CI₂ is photolyzed using UV light to produce a monoiodo radical.  This radical is then reacted with molecular oxygen to generate the Criegee intermediate.

The Criegee intermediates are cooled in a supersonic expansion, and interrogated using a variety of spectroscopic techniques.  Most recently, the Lester group has developed a novel synthetic route for the methyl vinyl ketone oxide (MVK-oxide) Criegee intermediate, (CH₃)(CH₂CH)COO.  MVK-oxide is predicted to be the predominant four-carbon Criegee intermediate formed during the ozonolysis of isoprene, the most abundant non-methane volatile organic compound in the earth’s atmosphere.

Our group uses a variety of experimental techniques to study Criegee intermediates, their IR and UV spectra, and their photoinduced chemistry

VUV Photoionization and TOF Mass Spectrometry

Velocity Map Imaging

IR Action Spectroscopy and Unimolecular Decay Dynamics