Atmospheric Chemistry Program Seminar
Peroxy radicals are getting curiouser and curiouser
Prof Neil Donahue,
Carnegie Mellon University
"Organic peroxy radicals sit at the center of tropospheric chemistry. Essentially all oxidation processes produce peroxy radicals immediately after an oxidant attacks a stable organic molecule. They have gas-phase lifetimes ranging from 1-1000 seconds. They also have choices; peroxy radical branching defines tropospheric chemistry. In the textbook case, they can react either with hydroperoxy radicals or with nitric oxide, either terminating as hydroperoxides or propagating to dark places that only Paul Ziemann understands while producing nitrogen dioxide and ultimately ozone. However, we have recently found that organoperoxy radicals with additional oxygenated functional groups can undergo progressive “autoxidation” (oxidation in the presence of molecular oxygen only) via internal hydrogen atom transfer and subsequent oxygen addition. These oxygenated organoperoxy radicals also appear to react with each other very rapidly (though this is uncertain) and to produce covalently bound organoperoxides (though this should be spin forbidden). Some of these products can have exceptionally low vapor pressures, and when formed in the gas phase can thus drive new-particle formation. It is possible that this is a major new-particle formation process in the pristine atmosphere, and that it was the dominant particle formation process in the pre-industrial atmosphere. In this talk I will explore recent experimental findings from the CLOUD experiment at CERN as well as modeling frameworks we have been developing to represent this chemistry and to translate chemical behavior observed in chambers to real-world conditions."
Please contact Anne.Handschy@colorado.edu