The German chemist Otto Hahn (1879-1968) was a joint discoverer of nuclear fission and a Nobel Prize winner for chemistry.

Otto Hahn was born in Frankfurt am Main on March 8, 1879. He was the youngest son of the owner of a prosperous glazing business. After leaving school in Frankfurt, he went to Marburg University with the intention of entering the chemical industry. Research on bromine derivatives of isoeugenol led to a doctorate in 1901, and after a year's military service he returned to Marburg to continue his research.

The turning point in Hahn's career came in 1904. He had in mind an industrial post for which knowledge of a foreign language was desirable, so he worked under Sir William Ramsay at University College, London. His task was to separate radium from a sample of impure barium chloride. Within a few months he showed that another radioactive substance was present and named it radiothorium. Urged by Ramsay to continue academic research in radioactivity, Hahn moved to Montreal, Canada, in 1905 to work with Ernest Rutherford. Here again success came quickly, and within a year he had recognized two other radioactive species, which he called thorium-C and radioactinium.

In 1906 Hahn returned to Germany, obtaining a place in Emil Fischer's Chemical Institute at Berlin University. Beginning work in a converted woodshop in the basement, he was soon joined by Lise Meitner, with whom he was to collaborate for 30 years. Here he discovered the radioelement mesothorium, studied beta emissions, and recognized the phenomenon known as radioactive recoil.

In 1913 Hahn was appointed head of radioactivity research in the new Kaiser Wilhelm Institute for Chemistry. Despite the interruptions of war service, Hahn made many major discoveries in the next 25 years. In an investigation of the radioactivity of rubidium he established a method for determining the geological ages of minerals that was in many cases more reliable than the traditional one using the radioactivity of uranium. A study of the radioactive precursors of actinium led to the discovery of the element protoactinium.

Following the discovery of artificial radioactivity by the Joliot-Curies in 1934, Meitner and Hahn repeated Enrico Fermi's experiment of bombarding uranium atoms with neutrons and agreed with his conclusion that new (transuranic) elements had been produced. Among the products isolated appeared to be new isotopes of radium; the suggestion that the "radium" was in fact barium by Hahn and Fritz Strassmann in January 1939 was the first indication that the atomic nucleus had been split. This discovery of nuclear fission became, of course, the basis for the production of nuclear weapons, a development which Hahn always deplored.

Hahn was a prisoner of war in England for a few months in 1945, and the next year he received the Nobel Prize for chemistry, which he had been awarded for 1944. Twenty years later Germany's first nuclear vessel was appropriately named Otto Hahn.

Further Reading

• A primary source is Hahn's A Scientific Autobiography (1962; trans. 1966). A detailed biographical profile of Hahn is in the Royal Society, Biographical Memoirs of Fellows of the Royal Society (vol. 16, 1970). See also Otto Robert Frisch, ed., Trends in Atomic Physics: Essays Dedicated to Lise Meitner, Otto Hahn, Max von Laue on the Occasion of Their 80th Birthday (1959), and Eduard Farber, Nobel Prize Winners in Chemistry, 1901-1961 (1953; rev. ed. 1963).