Samuel Isaac Weissman obtained a PhD (1938) in physical chemistry from the University of Chicago. In 1941 he left Chicago to explore optical properties of rare earths with G. N. Lewis at the University of California, Berkeley. During WWII, Weissman moved to Los Alamos to join the Manhattan Project, the development of the first atomic bomb. Moonlighting, Weissman and colleague David Lipkin were the first to show that phosphorescence from an aromatic molecule was pure dipole radiation from a triplet state. In 1946 Weissman moved to the chemistry department of Washington University, St. Louis and in 1955 became a full professor. There Weissman's interest in EPR became his primary focus. In 1952 Weissman, Pake and Townsend reported the first EPR observation of hyperfine lines. In 1953 Weissman and colleagues Lipkin, Townsend and Paul investigated the chemistry of the anions of aromatic molecules with one unpaired electron and showed that the unpaired electron is distributed over the entire aromatic “free radical”. Three years later he and Harden McConnell independently published a quantum mechanical interpretation of the isotopic hyperfine constants of π-radicals, providing detailed information on molecular structure. Beginning in 1957 Weissman exploited spectral line broadening to measure electron and atom transfer exchange reaction rate constants between a free radical and its diamagnetic precursor.In another classical contribution to EPR in 1958, Weissman recognized the significance of the electron dipolar interaction for the observation of triplet EPR spectra. Around 1975, Weissman pioneered the development and application of transient nutation EPR where the time evolution of the transverse electron spin magnetization is detected in the presence of a weak microwave magnetic field. Beginning in 1995, Weissman and colleagues pioneered the development of pulsed zero-field/low-field EPR combined with fast-field switching to study photoexcited triplet states in molecular crystals. Although Weissman became an emeritus professor in 1980, he remained very active in science and was in the department on most days in discussions with colleagues and students. Collaborations with Professor T. Lin and Dr. David Sloop continued until his death in 2007. To more fully appreciate the man whose career was distinguished by his brilliance in understanding and explaining nature at a fundamental level, examples of his quick and irreverent humor will also be presented.

Samuel Isaac Weissman: Pioneer of chemical applications of EPR and the way he was

2019 Spring National Meeting

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