Otto Hahn (8 March 1879 – 28 July 1968) 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. Glenn T. Seaborg deemed Hahn "the father of nuclear chemistry". Hahn 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. After completing his one year military service, the young chemist returned to the University of Marburg, where for two years he worked as assistant to his doctoral supervisor, Geheimrat Professor Theodor Zincke.
In the summer of 1906 Hahn returned to Germany, where he collaborated with Emil Fischer at the University of Berlin. Fischer placed at his disposal a former woodworking shop ("Holzwerkstatt") in the Chemical Institute to use as his own laboratory. There, in the space of a few months, using extremely primitive apparatus, Hahn discovered mesothorium I, mesothorium II and - independently from Boltwood - the mother substance of radium, ionium. In subsequent years, mesothorium I (radium 228) assumed great importance because, like radium 226 (discovered by Pierre and Marie Curie), it was ideally suited for use in medical radiation treatment, while costing only half as much to manufacture. (In 1914, for the discovery of mesothorium I, Otto Hahn was first nominated for the Nobel Prize in Chemistry by Adolf von Baeyer). In June 1907, by means of the traditional habilitation thesis, Hahn qualified to teach at the University of Berlin. On 28 September 1907 - something of a historic date in the history of atomic research - he made the acquaintance of the young Austrian physicist Lise Meitner, who had transferred from Vienna to Berlin. So began the thirty-year collaboration and lifelong close friendship between the two scientists.
After the physicist Harriet Brooks had observed a radioactive recoil in 1904, but interpreted it wrongly, Otto Hahn succeeded, in the winter of 1908/09, in demonstrating the radioactive recoil incident to alpha particle emission and interpreting it correctly. "...a profoundly significant discovery in physics with far-reaching consequences", as the physicist Walther Gerlach put it.
In 1910 Hahn was appointed professor, and in 1912 he became head of the Radioactivity Department of the newly founded Kaiser Wilhelm Institute for Chemistry in Berlin-Dahlem (since 1956 "Otto Hahn Building of the Free University", Berlin, Thielallee 63). Succeeding Alfred Stock, Hahn was director of the institute from 1928 to 1946. As early as 1924, Hahn was elected to full membership of the Prussian Academy of Sciences in Berlin (proposed by Einstein, Planck, Fritz Haber, Schlenk and von Laue).
In June 1911, while attending a conference in Stettin (today: Szczecin, Poland) Otto Hahn met Edith Junghans (1887-1968), an art student. On 22 March 1913 the couple married in Edith's native city of Stettin, where her father, Paul Ferdinand Junghans, was a high-ranking law officer and President of the City Parliament until his 1915 death. Their only child, Hanno, born in 1922, became a distinguished art historian and architectural researcher (at the Hertziana in Rome). In 1960, while on a study trip in France, Dr Hanno Hahn was involved in a fatal car accident, together with his wife and assistant Ilse Hahn, née Pletz. They left a fourteen-year-old son, Dietrich. In 1990, the "Hanno and Ilse Hahn Prize for Outstanding Contributions to Italian Art History" was established to support talented young art historians and in memory of Hanno and Ilse Hahn. It is awarded biennally by the Bibliotheca Hertziana, Max Planck Institute for Art History, in Rome.
During the First World War, Hahn was conscripted into the army, where he was assigned, together with James Franck and Gustav Hertz, to the special unit for chemical warfare under the direction of Fritz Haber. The unit developed, tested and produced poison gas for military purposes, and was sent to both the western and eastern front lines. In December 1916, Hahn was transferred to the "Headquarters of His Majesty" in Berlin, and was able to resume his radiochemical research in his institute. In 1917/18 Hahn and Lise Meitner isolated a long-lived activity, which they named "proto-actinium". Already in 1913, Fajans and Göhring had isolated a short-lived activity from uranium X2 (later known as 234mPa) and called the substance "brevium". The two activities were different isotopes of the same undiscovered element no. 91. Finally in 1949, the International Union of Pure and Applied Chemistry (IUPAC) named this new element protactinium and confirmed Hahn and Meitner as discoverers.
In February 1921, Otto Hahn published the first report on his discovery of uranium Z (later known as 234Pa), the first example of nuclear isomerism. "...a discovery that was not understood at the time but later became highly significant for nuclear physics", as Walther Gerlach remarked. And, indeed, it was not until 1936 that the young physicist Carl Friedrich von Weizsäcker succeeded in providing a theoretical explanation of the phenomenon of nuclear isomerism. For this discovery, whose full significance was recognized by very few, Hahn was again proposed, in 1923, for the Nobel Prize in Chemistry, this time by Max Planck, among others.
In the early 1920s, Otto Hahn created a new field of work. Using the "emanation method", which he had recently developed, and the "emanation ability", he founded what became known as "Applied Radiochemistry" for the researching of general chemical and physical-chemical questions. In 1933 he published a book in English (and later in Russian) entitled "Applied Radiochemistry". It contains the lectures given by Hahn when he was a visiting professor at Cornell University in Ithaca, New York in 1933. In 1966, Glenn T. Seaborg, President of the United States Atomic Energy Commission, wrote about this book as follows:
But no physicist or chemist really took Noddack's speculation seriously or tested them, not even Ida Noddack. The idea that heavy atomic nuclei could break down into lighter elements was regarded as a totally inadmissible theory and impossible to test experimentally.
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. The barium was detected by the use of an organic barium salt constructed by Wilhelm Traube, a Jewish chemist who was later arrested and murdered despite Hahn's efforts to save him.
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, who had escaped out of Germany earlier that year and was then 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.
In a later appreciation, Meitner wrote:
In an interview on German television (ARD, 8 March 1959), Meitner said:
Fritz Strassmann responded with this clarification:
(Citation sources: Lise Meitner - Recollections of Otto Hahn. Stuttgart 2005).
In their second publication on nuclear fission (Die Naturwissenschaften, 10 February 1939) Otto Hahn and Fritz Strassmann predicted the existence and liberation of additional neutrons during the fission process, which was proofed as chain reaction by Frédéric Joliot and his team in March 1939.
During the war, Otto Hahn - together with his assistants Hans-Joachim Born, Siegfried Flügge, Hans Götte, Walter Seelmann-Eggebert and Fritz Strassmann - worked on uranium fission reactions. By 1945 he had drawn up a list of 25 elements and about 100 isotopes whose existence he had demonstrated.
Thanks to his determined intervention, Hahn, who had always been an opponent of the Nazi dictatorship, was able to support numerous members of his institute whose lives were in danger or were suffering persecution, and prevent them from being sent to the front line or deported. In this, he was assisted by his courageous wife Edith, who had for years collected food for Jews hiding in Berlin. As early as 1934, Hahn resigned from the University of Berlin to protest the dismissal of Jewish colleagues, notably Lise Meitner, Fritz Haber, and James Franck.
At the end of World War II in 1945 Hahn was suspected of working on the German nuclear energy project to develop an atomic reactor or an atomic bomb. But his only connection was the discovery of fission, he did not work on the program. Hahn and nine German physicists (including Max von Laue, Werner Heisenberg and Carl Friedrich von Weizsäcker) were interned at Farm Hall, Godmanchester, near Cambridge, England. While they were there, the German scientists learned of the dropping of the American atom bombs on Hiroshima and Nagasaki on 6 August and 9 August. Hahn was on the brink of despair, as he felt that because he had discovered nuclear fission he shared responsibility for the death and suffering of hundreds of thousands of Japanese people. Early in January 1946, the group was allowed to return to Germany.
"There is no doubt at all that Hahn fully deserves the Nobel Prize in Chemistry" wrote Lise Meitner to her friend Eva von Bahr-Bergius in November 1945. Meitner's former assistant Carl Friedrich von Weizsäcker later added: "He certainly did deserve this Nobel Prize. He would have deserved it even if he had not made this discovery. But everyone recognized that the splitting of the atomic nucleus merited a Nobel Prize."
(Citations source: Lise Meitner - Recollections of Otto Hahn. Stuttgart 2005)
Hahn attended the Nobel festivities the year after he was awarded the prize. On 10 December 1946, King Gustav V of Sweden finally presented him with his Nobel Prize medal and diploma.
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.
Hahn was made an honorary citizen of the cities of Frankfurt am Main and Göttingen, and of the land and the city of Berlin. The day after his death, the Max Planck Society published the following obituary notice in all the major newspapers:
Proposals were made at different times, first in 1971 by American chemists, that the newly syntheticized element no. 105 should be named Hahnium in Hahn's honour, although in 1997 the IUPAC (International Union of Pure and Applied Chemistry) finally named it Dubnium, after the Russian research center in Dubna (see Element naming controversy). The intention is, however, that element no. 108, Hassium should be renamed Hahnium in the future. In addition, in 1964 the only European and one of the world's three nuclear-powered civilian ships, the freighter NS Otto Hahn, was named in his honour. In 1959 there were the opening ceremonies of the "Otto Hahn Institute" in Mainz and the "Hahn Meitner Institute for Nuclear Research (HMI)" in Berlin. There are craters on mars and moon, and the asteroid No. 19126 "Ottohahn" named in his honour, as well as the "Otto Hahn Prize" of both the German Chemical and Physical Societies, the "Otto Hahn Medal" of the Max Planck Society and the "Otto Hahn Peace Medal in Gold" of the United Nations Association of Germany (DGVN) in Berlin.
A great many cities and districts in the German speaking countries have named secondary schools of all types after him, and countless streets, squares and bridges throughout Europe bear his name. Several states have honoured Otto Hahn by issuing coins, medals and stamps (among them the Federal Republic of Germany, the German Democratic Republic, Austria, Romania, Angola, Cuba, the Commonwealth of Dominica, Madagascar, St. Vincent & the Grenadines, Chad, Ghana, Guinea and Bissau). An island in the Antarctic (near Mt. Discovery) was also named after him, as were two Intercity trains of the German Federal Railways in 1971, running between Hamburg and Basel SBB, and the "Otto Hahn Library" in Göttingen. In 1974, in appreciation of the special contribution of Otto Hahn to German-Israeli relations, a wing of the Weizmann Institute of Science in Rehovot, Israel, was given the name "Otto Hahn Wing". In several cities and districts busts, monuments and memorial plaques were unveiled, including Berlin (East and West), Boston (USA), Frankfurt am Main, Göttingen, Gundersheim, Mainz, Marburg, Munich (in the hall of honour in the Deutsches Museum), Rehovot (Israel), San Vigilio (Lake Garda) and Vienna (in the foyer of the International Atomic Energy Agency, IAEA). A special honour in 1997 was conferred on Hahn in the Netherlands: after an azalea already bore his name (Rhododendron luteum var Otto Hahn), Dutch rose growers named a new variety of rose "Otto Hahn".
At the end of 1999 the German newsmagazine FOCUS published an inquiry of 500 leading natural scientists, engineers and physicians about the most important scientists of the 20th century. In this poll the experimental chemist Otto Hahn - after the theoretical physicists Albert Einstein and Max Planck - was elected third (with 81 points) and thus the most significant empiric researcher of his time. (FOCUS, No. 52, 1999, p. 103-108).