Otto Hahn

PHYSICIST NAME: Otto Hahn
STUDENT NAME:Angela Mari Peralta

BIOGRAPHY

Otto Hahn (8 March 1879 – 28 July 1968) was a German chemist and Nobel laureate who pioneered the fields of radioactivity and radiochemistry. He is regarded as "the father of nuclear chemistry" and the "founder of the atomic age". Hahn served as the last President of the Kaiser Wilhelm Society (KWG) in 1946 and as the founding President of the Max Planck Society (MPG) from 1948 to 1960.

Hahn was the youngest son of Heinrich Hahn (1845–1922), a prosperous glazier and entrepreneur ("Glasbau Hahn"), and Charlotte Hahn, née Giese (1845–1905). Together with his brothers Karl, Heiner and Julius, Otto was raised in a sheltered environment. At the age of 15, he began to take a special interest in chemistry and carried out simple experiments in the laundry room of the family home. His father wanted Otto to study architecture, as he had built or acquired several residential and business properties. But Otto persuaded him that his ambition was to become an industrial chemist.

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.

CONTRIBUTIONS

Discovery of nuclear fission

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. The German chemist Ida Noddack proposed an exception. She anticipated the paradigm shift of 1938/39 in her article published in the journal Angewandte Chemie, Nr. 47, 1934, in which she speculated:
It is conceivable that when heavy nuclei are bombarded with neutrons these nuclei could break down into several fairly large fragments, which are certainly isotopes of known elements, but not neighbours of the irradiated elements.
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.

Nuclear fission experimental setup, reconstructed at the Deutsches Museum, Munich.
Otto Hahn's notebookHahn 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:
"The discovery of nuclear fission by Otto Hahn and Fritz Strassmann opened up a new era in human history. It seems to me that what makes the science behind this discovery so remarkable is that it was achieved by purely chemical means.”
In an interview on German television (ARD, 8 March 1959), Meitner said:
"Hahn and Strassmann were able to do this by exceptionally good chemistry, fantastically good chemistry, which was way ahead of what anyone else was capable of at that time. The Americans learned to do it later. But at that time, Hahn and Strassmann were really the only ones who could do it. And that was because they were such good chemists. Somehow they really succeeded in using chemistry to demonstrate and prove a physical process."

Fritz Strassmann responded with this clarification:
"Professor Meitner stated that the success could be attributed to chemistry. I have to make a slight correction. Chemistry merely isolated the individual substances, it did not precisely identify them. It took Professor Hahn's method to do this. This is where his achievement lies."

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 from 3 July 1945 to 3 January 1946. 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 1945. 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.

OBJECT OF INTEREST

Hahn is a capital fellow, and has done his work admirably. I am sure that you would enjoy having him to work with you. He is a pleasant fellow, unassuming, completely trustworthy and highly talented and I have come to like him very much. I can strongly recommend him as one of the best physicists I know. Hahn has a special nose for discovering new elements.

Hahn has a special smell for discovering new elements. He is doing the best work in Germany at present. Dr. Hahn is not reliable of speech. He is not learned, not distinguished, not famous as a scientist. He sacrifices truth to modesty and I sympathize with him in his temptation. His discovery has caused a huge sensation in the whole scientific world, and every laboratory which has the necessary means is now working on the consequences of his discovery.