Student Hosted Colloquia: Professor Marsha Lester, University of Pennsylvania
Student Hosted Colloquia: Professor Marsha Lester, University of Pennsylvania (Host: Kallie Hilsabeck and Jana Meiser)
About the Seminar
"Spectroscopic and dynamical probes of atmospheric reaction pathways"
Alkene ozonolysis is a primary oxidation pathway for alkenes, the most abundant organic compounds in the Earth’s troposphere after methane, and also an important source of atmospheric hydroxyl radicals (OH). Alkene ozonolysis takes place through a complicated reaction pathway with multiple intermediates and barriers on the way to OH products. A carbonyl oxide species, known as the Criegee intermediate (RR¢COO), represents a critical branching point on the pathway that controls the products formed in this important class of reactions. In this laboratory, the simplest Criegee intermediate CH2OO and methyl-, dimethyl-, ethyl-, and vinyl-substituted Criegee intermediates are generated by alternative synthetic schemes. Recent studies have focused on characterizing the Criegee intermediates utilizing infrared and ultraviolet spectroscopic methods, and examining their unimolecular and bimolecular reactions under laboratory and atmospheric conditions. Infrared ‘fingerprint’ and electronic spectra reflecting p-conjugation of the Criegee intermediates are obtained, along with time-resolved studies of their unimolecular decay to OH radical products. Remarkably, the conformation and nature of the substituents (R, R¢) of the Criegee intermediates are found to have a profound effect on their reaction dynamics and subsequent chemistry in the atmosphere.
About the Speaker
Marsha I. Lester has risen through the academic ranks at the University of Pennsylvania, where she is currently the Edmund J. Kahn Distinguished Professor in the Department of Chemistry of the School of Arts & Sciences. She completed a four-year term as Chair of the Department of Chemistry in 2009. Lester has received many honors including election to the National Academy of Sciences and the American Academy of Arts & Sciences. In addition, she has been awarded the Herbert P. Broida Prize of the American Physical Society, the Philadelphia American Chemical Society Section Award, the Garvan-Olin Medal of the American Chemical Society, the Bourke Lectureship of the Faraday Division of the Royal Society of Chemistry, a John Simon Guggenheim Memorial Foundation Fellowship, an Alfred P. Sloan Research Fellowship, and the Dreyfus Teacher-Scholar Award. She is a fellow of the American Physical Society, the American Association for the Advancement of Science, and the American Chemical Society.
Lester was Editor-in-Chief of The Journal of Chemical Physics, the preeminent journal in her field, from 2009-2018. During her ten years at the helm of the Journal, she reinvigorated the Journal with numerous initiatives to attract more of the best papers in the broadly defined field of chemical physics. Lester has consistently devoted a substantial amount of her time to scientific service activities. She has served on the NRC Commission on Physical Sciences, Mathematics, and Applications as well as its Board on Chemical Sciences and Technology. She has been engaged in activities of the American Chemical Society, the American Physical Society, the National Science Foundation, and the Department of Energy. She is also a founding member and past Chair of the Penn Forum for Women Faculty.
Lester’s research group has developed innovative methods for stabilizing ‘entrance channel complexes’ and reaction intermediates of environmental significance. Her group has employed novel spectroscopic methods to rigorously characterize these important, yet previously uncharted, regions of chemical reaction pathways.