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Otto Hahn (; 8 March 1879 – 28 July 1968) was a German chemist, and a pioneer in the fields of radioactivity and radiochemistry. Hahn is referred to as the father of nuclear chemistry. Hahn and Lise Meitner discovered radioactive isotopes of radium, thorium, protactinium and uranium. He also discovered the phenomena of radioactive recoil and nuclear isomerism, and pioneered rubidium–strontium dating. In 1938, Hahn, Lise Meitner and Fritz Strassmann discovered nuclear fission, for which Hahn received the 1944 Nobel Prize for Chemistry. Nuclear fission was the basis for nuclear reactors and nuclear weapons.