Abstract:
The chemistry defining the composition of complex environments, such as Earth’s atmosphere, is often treated as a “black box” - where stable starting and product species may be known, but the intermediate sequence of steps connecting the two are ill-defined. The ambiguity of the chemical processes involving short-lived reactive intermediate species that connect starting and product species leads to significant uncertainty in models and inhibits the development of predictive capabilities for broader applicability. Direct laboratory studies of these reactive intermediate species open up the “black box” to provide critical fundamental insights into reactions that may play critical roles in not-yet-understood phenomena, such as particulate matter formation from gas-phase starting species. I will discuss some recent work I led concerning the chemistry of Criegee intermediates – zwitterionic, reactive intermediates formed from the reaction of ozone with alkenes. Through broad collaboration, direct laboratory measurements, state-of-the-art theoretical work, in-situ environmental measurements and chemical models were brought together to investigate the role of a single sequence of chemical reactions in the formation of particulate matter in the Amazon region. 

Bio:
Rebecca Caravan is an Assistant Chemist in the Chemical Sciences and Engineering division. After reading chemistry at the University of Bristol, she obtained her PhD at the University of Leeds specializing in gas-phase reaction kinetics. From 2015-2019, she was a postdoctoral researcher at Sandia National Laboratories, undertaking fundamental chemical kinetics and mechanistic studies at the Advanced Light Source, Lawrence Berkeley National Laboratory. In 2020, she took up a fellowship at the NASA Jet Propulsion Laboratory, where she investigated chemistry pertinent to Earth’s troposphere. She joined Argonne this month and is developing capabilities to study reaction kinetics and mechanisms of reactive intermediate species.