German chemist, one of the discoverers of nuclear fission, for which he was awarded the 1944 Nobel Prize for Chemistry.
The son of a successful merchant, Hahn had to overcome considerable family opposition before he was allowed to pursue a scientific career. He was educated at the University of Marburg, where he received his doctorate in 1901. After some years abroad working with William Ramsay (1852–1916) in London and Ernest Rutherford in Canada, Hahn returned to Germany in 1907 to join the chemistry department of Berlin University. Although he became professor of chemistry in 1910, Hahn left in 1912 for the Kaiser Wilhelm Institute of Chemistry where he spent the rest of his career.
Although he had intended to become an industrial chemist, Hahn was so engrossed in radioactivity that he turned instead to academic chemistry. For some thirty years, in collaboration with the physicist Lise Meitner, he explored the chemistry of the newly discovered radioactive elements. Together they discovered (1917) the new element protactinium. Their most important work, in collaboration with Fritz Strassmann (1902–80), was carried out in the 1930s on uranium. When uranium was bombarded with slow neutrons they repeatedly found barium in the decay products. It was left to Meitner, and her nephew Otto Frisch, to interpret the reaction as nuclear fission.
Hahn himself contributed little to the German war effort and would have nothing to do with nuclear weapons. In 1957, with seventeen other leading German atomic scientists, he signed a declaration stating that he would never work on the production or testing of atomic weapons.
Subjects: Science and Mathematics.