Otto Hahn was a German chemist who received the 1944 Nobel Prize in Chemistry for discovering nuclear fission. He is considered a pioneer of radioactivity and radiochemistry, and was also called the "founder of the atomic age" by his contemporaries and, officially, by the senate and the members of the Max Planck Society.

In 1897, after taking his Abitur at the Klinger Oberrealschule in Frankfurt, Hahn began to study chemistry and mineralogy at the University of Marburg. His subsidiary subjects were physics and philosophy. Hahn joined the Students' Association of Natural Sciences and Medicine, a student fraternity and a forerunner of today's Nibelungia Fraternity. He spent his third and fourth semester studying under Adolf von Baeyer at the University of Munich. In 1901, Hahn received his doctorate in Marburg for a dissertation entitled On Bromine Derivates of Isoeugenol, a topic in classical organic chemistry.

Hahn obtained a post as assistant in the Chemical Institute at Marburg, staying there two years, after which he worked under Sir William Ramsay at University College, London, from the autumn of 1904 to the following summer. His work here was rewarded by the discovery of a new radioactive substance, radiothorium, while working on the preparation of pure radium salts.

From the autumn of 1905 to the summer of the following year Hahn was at the Physical Institute of McGill University, Montreal (Canada) working under Professor Ernest Rutherford. Here he discovered radioactinium and conducted investigations with Rutherford on alpha-rays of radiothorium and radioactinium.

At the end of 1907, Dr. Lise Meitner came to Berlin from Vienna and then began more than thirty years' collaboration. Their joint work embraced: investigations on beta-rays, their absorbability, magnetic spectra, etc.; use of the radioactive recoil, discovered shortly before by Hahn, to obtain new radioactive transformation products.

Jointly with Lise Meitner and his pupil and assistant Fritz Strassmann (1902-1980), Otto Hahn furthered the research begun by Enrico Fermi and his team in 1934 when they bombarded uranium with neutrons. Until 1938, it was believed that the elements with atomic numbers greater than 92 (known as transuranium elements) arise when uranium atoms are bombarded with neutrons.

On 13 July 1938, with the help and support of Hahn, Lise Meitner, who was at great risk as she was of Jewish ancestry and had lost her Austrian citizenship after the Anschluss, emigrated to Stockholm, Sweden by crossing the German-Dutch border illegally.

Hahn continued to work with Strassmann on elucidating the outcome of bombardment of uranium with thermal neutrons. In December 1938, when Hahn and Strassmann looked for transuranium elements in a uranium sample that had been bombarded with neutrons, they found traces of barium.

On the evidence of the decisive experiment on 17 December 1938 (the celebrated "radium-barium-mesothorium-fractionation"), Otto Hahn concluded that the uranium nucleus had "burst" into atomic nuclei of medium weight. This was the discovery of nuclear fission.

On 22 December 1938, Hahn and Fritz Strassmann sent a manuscript to Naturwissenschaften reporting their radiochemical results, which were the irrefutable proof that the uranium had been split into fragments consisting of lighter elements; simultaneously, they communicated these results to Lise Meitner  in Sweden.  Meitner, and her nephew, the young physicist Otto Robert Frisch, correctly interpreted these results as being nuclear fission, a term coined by Frisch, which subsequently became internationally known. Frisch confirmed this experimentally on 13 January 1939.

On 15 November 1945 the Royal Swedish Academy of Sciences announced that Hahn had been awarded the 1944 Nobel Prize in Chemistry "for his discovery of the fission of heavy atomic nuclei."

Hahn published the chemical evidence for fission without listing Meitner as a co-author.  Some argue that he did so to protect her given the situation in Nazi Germany. Others argue that Hahn deliberately omitted Meitner's contribution, particularly after the war when he repeatedly maintained that his chemical experiments verifying fission had never been inspired or guided by Meitner. Some historians who have documented the history of the discovery of nuclear fission believe Meitner should have been awarded the Nobel Prize with Hahn.

Hahn, Meitner, and Strassmann were not engaged in nuclear weapons research during World War II. At the end of the war Hahn was astonished to hear that he had won the Nobel Prize and that nuclear bombs had been developed from his basic discovery. Later, as director of the Max-Planck-Gesellschaft (the postwar successor to the Kaiser Wilhelm Gesellschaft), he spoke vigorously against the misuse of atomic energy. Meitner—who many thought should have received the Nobel Prize with Hahn—continued to do nuclear research in Sweden and then England. Strassmann nurtured the study of nuclear chemistry in Mainz, Germany.

Hahn received many governmental honors and academic awards from all over the world. He was elected member or honorary member in 45 Academies and scientific societies (among them the Royal Society in London and the Academies in Allahabad (India), Bangalore (India), Boston (USA), Bucharest, Copenhagen, Helsinki, Lisbon, Madrid, Rome, Stockholm, Vienna) and received 37 of the highest national and international orders and medals (among them the Golden Paracelsus Medal from the Swiss Chemical Society and the Faraday Medal from the British Chemical Society). In 1959 President Charles de Gaulle of France made him an Officer of the Légion d'Honneur, he was made a knight of the Peace Class of the Order Pour le Mérite, received the Distinguished Service Order and the Grand Cross of the Federal Republic of Germany. In 1961 Pope John XXIII awarded him the Gold Medal of the Papal Academy. (In 1957 Hahn was elected an honorary citizen of the city of Magdeburg, German Democratic Republic, and in 1958 an honorary member of the Soviet Academy of Science in Moscow. He declined both honors).

In 1966, President Lyndon B. Johnson of the USA, and the USA Atomic Energy Commission awarded Hahn (together with Lise Meitner and Fritz Strassmann) the Enrico Fermi Prize. This was the only time the Fermi Prize has been awarded to non-Americans.

Sources

• Chemical Heritage Foundation, Otto Hahn, Lise Meitner and Fritz Strassmann, Accessed 30 October 2008.
• The Nobel Foundation, Otto Hahn, Nobel Lectures, Chemistry 1942-1962, Elsevier Publishing Company, Amsterdam, 1964.
• Wikipedia Contributors, Otto Hahn, Wikipedia the Free Encyclopedia, Accessed 30 October 2008.