Q&As with Marsha I. Lester
Evidence of Earth’s changing environment is abundant, from diminished polar ice caps to increased frequency of catastrophic storms. However, the chemical reactions in our atmosphere that can contribute to a changing climate are less well known. A physical chemist at the University of Pennsylvania who studies the troposphere, Marsha I. Lester combines experiment, theory, and modeling to investigate the chemistry at the edge of our planet. Her group examines the oxidation of man-made and biogenic volatile organic compounds, such as alkenes. The reactions proceed through transitory species known as Criegee intermediates, which were first predicted in the 1950s but only recently observed. Lester’s group generated these intermediates, characterized them using spectroscopy, and measured the rates of their decay to hydroxyl radicals, which are key oxidants in the troposphere. The research has enriched our understanding of atmospheric chemistry and might reveal how the atmosphere can repair itself. PNAS recently spoke to Lester, who was elected to the National Academy of Sciences (NAS) in May 2016, about her current research.



Marsha I. Lester. Image courtesy of Felice Macera (University of Pennsylvania, Philadelphia).



> PNAS:Your work with Criegee intermediates reveals how oxidants in the troposphere can “cleanse” the atmosphere. How does this occur, and what …