June 19, 2000

Berkeley Lab Science Beat

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Darleane Hoffman, a chemist with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has been awarded the Priestley Medal, the highest honor of the American Chemical Society. Hoffman became the second woman to receive the award in the 125-year history of the ACS. The award is named for Joseph Priestley, who reported the discovery of oxygen in 1774.

Hoffman holds joint appointments with Berkeley Lab's Nuclear Science Division and the Chemistry Department of the University of California at Berkeley. She is an internationally recognized expert in the study of transuranic elements -- chemical elements heavier than uranium that typically decay to lighter elements almost immediately -- and was a member of the team that discovered elements 118 and 116 this past summer. Hoffman called the discovery of these elements "one of the most exciting of my career" because their radioactive decay patterns provided strong support for the existence of the "island of stability" that theorists have long predicted for superheavy elements.

Hoffman was also a member of the Berkeley Lab team that confirmed the discovery of element 106, which was named seaborgium for Nobel laureate Glenn Seaborg, a long-time colleague of Hoffman's and also a Priestley Medal recipient. Like Seaborg, Hoffman has been honored with the National Medal of Science, the equivalent to the Nobel Prize in the United States. Hoffman received this honor in 1997 for, among other achievements, her discovery of macroscopic quantities of a new chemical element in nature, primordial plutonium-244, and her leadership in the discovery of a phenomenon called "symmetric mass division," a form of spontaneous fission that results in two "daughter" nuclei nearly equal in mass.

Hoffman is renowned not only for her discoveries of new elements but also for her research into their chemical properties. She led the development of a technique called "one-atom-at-a-time" chemistry in which researchers study the chemical properties of short-lived elements by measuring the rate of radioactive decay of individual atoms, combining the results, and comparing these properties to other known elements. This technique has proven to be extremely fruitful for studying the chemistry of short-lived elements.

Hoffman was born on November 8, 1926 in Terril, Iowa. She attended Iowa State University, where she received a B.S. in chemistry in 1948 and a Ph.D. in chemistry in 1951. Her first job as a chemist was at Oak Ridge National Laboratory. In 1953 she moved to Los Alamos National Laboratory, where she did her spontaneous fission work and where she remained until moving to Berkeley in 1984. At Berkeley, she became the group leader of the Heavy Element and Radiochemistry Group. She was also reunited with Seaborg, with whom she'd worked as a Guggenheim Fellow in 1978-79. From 1991 to 1996 she served as charter director of the Seaborg Institute for Transactinium Science, located at the Lawrence Livermore National Laboratory.

Hoffman also has served on many government advisory boards, including the National Academy of Science's Board on Radioactive Waste, the National Research Councilís Committee on Nuclear and Radiochemistry (which she chaired) and the National Research Councilís Board of Radioactive Waste Management.

Hoffman is the author of more than 200 research papers. She is a fellow of the American Institute of Chemists and the American Physical Society, and a member of the Norwegian Academy of Science and Letters. Among the many other honors she has received are the Nuclear Chemistry Award (1983) and the Francis P. Garvan-John M. Olin Medal (1990) both from ACS. In 1996 she received UC Berkeley's highest academic award, the Berkeley Citation.

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