Darleane Hoffman

Darleane Hoffman

Darleane Hoffman with the instruments she uses to track down heavy elements. Photo courtesy Ernest Orlando Lawrence Berkeley National Laboratory.

Over the course of her career Darleane Hoffman (b. 1926) has chased some of the most elusive forms of matter—the heavy elements. These elements, which include plutonium, are hard to produce and exist for very short periods of time, yet Hoffman has succeeded in capturing and analyzing them. In studying these fugitive elements, she has made important discoveries about the nature of fission, the atomic process at the heart of nuclear power.

Hoffman grew up in Iowa. Her father was a school principal who sometimes taught math and coached girls’ basketball as well. After high school she entered Iowa State College (now Iowa State University), where she first majored in applied art but later changed to chemistry. She was inspired to pursue science by her chemistry professor, Nellie Naylor, but had some qualms because many women who went into science in those days had to choose between having a career and having a family—as Naylor had done—and Hoffman knew she wanted both. The story of Marie Curie, a Nobel Prize–winning scientist who also raised two daughters, convinced Hoffman to go ahead with her plans.

Darleane Hoffman in the early days of her career. Photo courtesy Los Alamos National Laboratory.

Darleane Hoffman in the early days of her career. Photo courtesy Los Alamos National Laboratory.

After graduation Hoffman stayed at Iowa State to earn her Ph.D. There she met and married Marvin Hoffman, also a doctoral student. Darleane graduated first and in 1952 went to work at Oak Ridge National Laboratory in Tennessee, while Marvin remained in Iowa to finish his Ph.D. The Hoffmans were soon reunited in Oak Ridge, and then together went to work at Los Alamos National Laboratory in New Mexico, where they researched nuclear chemistry.

Hoffman became known for a number of important achievements. For years, scientists believed that transuranium elements did not occur in nature, but in 1971 Hoffman published her discovery of small amounts of a plutonium isotope (plutonium-244) in a rock formation that was several billion years old. Hoffman also carried out a rare study of the chemistry of the element hahnium, also called dubnium. The study was rare because transuranium elements are so radioactive that they quickly decay before they can be studied. Using an isotope called hahnium-262, which has a half-life of only 35 seconds, she was able to study how the element behaved both in aqueous solution and in the gas phase. She studied the same properties of lawrencium-103, which has a half-life of three minutes.

Along the way, Hoffman made a significant discovery about nuclear fission. Scientists had known since the late 1930s that the nuclei of certain elements split when bombarded with neutrons, but in the early 1970s Hoffman discovered that the atoms of one element, fermium, could split spontaneously.

Hoffman worked at Los Alamos from 1953 to 1984, when she left to become a professor at the University of California, Berkeley, and researcher at the affiliated Lawrence Berkeley National Laboratory; and so becoming one of Glenn Seaborg’s most celebrated colleagues. There she was involved with the discovery of new superheavy elements, including the elements 114 and 116.

Hoffman has helped investigate nuclear weapons test sites for dangerous leakage of radioactive materials into the environment and is interested in the safety issues surrounding the solid radioactive waste produced by nuclear power. She received the National Medal of Science in 1997, the Priestley Medal in 2000 from the American Chemical Society, and numerous other honors. In addition to having a long, productive career, she has also managed to have a full family life, with two grown children and several grandchildren.

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