Hahn, Otto (1879–1968)

German physical chemist who was awarded the Nobel Prize for Chemistry in 1944 for his discovery of nuclear fission (see nuclear energy). In 1938 with Fritz Strassmann (1902–1980), he discovered that uranium nuclei split when bombarded with neutrons. Hahn did not participate in the resultant development of the atom bomb.

In 1918, Hahn and Lise Meitner discovered the longest-lived isotope of a new element which they called protactinium, and in 1921 they discovered nuclear isomers – radioisotopes with nuclei containing the same subatomic particles but differing in energy content and half-life.

Hahn was born in Frankfurt-am-Main and studied at Marburg. From 1904 to 1906 he worked in London under William Ramsay, who introduced Hahn to radiochemistry, and at McGill University in Montréal, Canada, with Ernest Rutherford. Returning to Germany, Hahn was joined at Berlin in 1907 by Meitner, beginning a long collaboration. Hahn was director of the Kaiser Wilhelm Institute for Chemistry in Berlin 1928–44, and then president of the Max Planck Institute in Göttingen.