Marsha I. Lester

University of Pennsylvania

Election Year: 2016
Primary Section: 14, Chemistry
Membership Type: Member


Marsha I. Lester is a physical chemist known for her spectroscopic studies of open-shell complexes and reaction intermediates of environmental significance, which characterize previously uncharted regions of chemical reaction pathways. Lester was born in 1955 and raised in Pittsburgh and Allentown, Pennsylvania. She graduated from Douglass College, Rutgers University in 1976 and received her PhD in Chemistry from Columbia University in 1981. After postdoctoral research at AT&T Bell Laboratories, she joined the chemistry faculty at the University of Pennsylvania in 1982 and has remained there over her academic career. She was Chair of the Department of Chemistry from 2005-2009. She is currently the Edmund J. Kahn Distinguished Professor in the Department of Chemistry and Editor-in-Chief of The Journal of Chemical Physics. Throughout her career, she has been active in enhancing the role of women in science. She was elected to Fellowship in the American Academy of Arts and Sciences, and has received a number of awards, including the Garvan-Olin Medal of the American Chemical Society, the Bourke Lectureship of the Faraday Division of the Royal Society of Chemistry, and a John Simon Guggenheim Memorial Foundation Fellowship. She was elected as a member of the National Academy of Sciences in 2016.

Research Interests

Marsha Lester has developed innovative methods for generating and characterizing open-shell complexes between a free radical and inert or reactive partner, e.g. OH-Ar, OH-H2, OH-CO, and reactive intermediates, e.g. HOONO, HOOO, CH2OO, enabling her to map out important, yet previously uncharted, regions of chemical reaction pathways. She demonstrated that reactive partners could be trapped in a shallow entrance channel reaction well, employed novel laser-based techniques to activate their intra- and inter-molecular vibrations, and followed their dynamics. Of particular note, she observed the bending vibrations of OH-CO that probe the reaction path leading directly to the HOCO transition state. She discovered remarkable changes in their intermolecular potentials upon OH electronic excitation, and obtained dynamical signatures of both reactive and nonreactive electronic quenching outcomes. She characterized the structure and stability of HOONO, a critical intermediate for NOx atmospheric chemistry. Recently, Lester obtained the UV spectra of several long-sought Criegee intermediates, carbonyl oxides arising from alkene ozonolysis in the troposphere, revealing their rapid photochemical decay. Her studies of vibrationally activated Criegee intermediates have identified the rate and effective barrier for a critical hydrogen transfer step that leads to OH radicals, which is a substantial source of this key oxidant in the atmosphere.

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