AGS-PRF: The Mechanism and Atmospheric Impact of the Peroxy Radicals (RO2) Self-Reaction

In this Postdoctoral Research Fellowship project, the PI will study the fate of organic peroxy radicals in the troposphere as the rates and products of many important peroxy radical reactions remain uncertain for the wide range of hydrocarbons present in the atmosphere. In particular, while the mechanism of the peroxy radical self-reaction has been speculated to proceed via a tetroxide intermediate for decades, this intermediate and the energetics of its formation and decomposition have never been directly observed. The work will yield the first conclusive detection of this intermediate and the first direct measurement of its decomposition. The PI will engage in existing outreach programs, such as the yearly public science fair “Explore Your Universe,” and other outreach to local elementary schools (including demonstrations and science fairs). In addition to these outreach activities, the PI will mentor both graduate and undergraduate students. In this work, the PI will seek to answer the following research questions: (1) Does the organic peroxy radical self-reaction proceed via a tetroxide intermediate? (2) Can theoretical calculations accurately capture the energetics and kinetics of the self-reaction for a prototypical peroxy radical? (3) How does peroxy radical structure change the degree of fragmentation, termination, and dimerization in the organic peroxy radical self-reaction? Three research tasks will be used to address these questions, including: (1) Using IR action spectroscopy to detect the tetroxide intermediate formed in the i-propylperoxy radical system; (2) Using IR action spectroscopy to measure microcanonical rate constants of the tetroxide decomposition to alkoxy radicals and use these results to improve theoretical and computational methods; and (3) Augmentation of the detailed mechanistic understanding from the previous two tasks with a broader understanding of product distribution as a function of peroxy radical structure via chamber experiments. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.