February 22, 1902 - Fritz Strassmann is born

Friedrich Wilhelm Strassmann (Boppaard, February 22, 1902 - Mainz, April 22, 1980)

The German physicist and chemist Fritz Strassmann is known for the discovery, together with Otto Hahn and Lise Meitner, of the fission of uranium (1938). In addition, he received the prestigious Enrico Fermi Prize in 1966 for his contributions to nuclear chemistry and his extensive experimental studies, which culminated in the discovery of fission.


Attracted from his adolescence by scientific knowledge, he studied Physics and Chemistry at the Technical University of Hannover, earning his doctorate in 1929. It was at that same University where he began his fruitful career as a teacher and researcher. One of his first successes was the development of a method for dating rocks, based on the analysis of the radioactive elements rubidium and strontium.

His early discoveries allowed him to join the prestigious team of researchers working at the Kaiser Wilhelm Institute in Berlin in the 1930s, where he had the opportunity to work with the aforementioned Hahn and Meitner, making possible the discovery of uranium fission.

During World War II, Otto Hahn and Fritz Strassmann continued to work in the field of nuclear physics, with special attention to the study of uranium fission products (such as barium and krypton). However, as both enemies of Hitler's policy, they flatly refused to participate in a nuclear weapons manufacturing program. Hahn even confessed to Strassmann that if he ever suspected that his work had helped Hitler dispose of the atomic bomb, he would take his own life without hesitation at that point.

Once the war was over, both Strassmann and Hahn regained their status. Thus Hahn was able to collect the Nobel Prize that had been secretly given to him in 1944, and Strassmann was rewarded in 1946 with the chair of Inorganic and Nuclear Chemistry at the University of Mainz, where he founded and directed the Institute for Inorganic and Nuclear Chemistry. Later he was appointed director of the Max Planck Institute for Chemistry.

Strassmann's contributions

In the beginnings of his career as a researcher, Strassmann dealt with radioactive elements used in geochronology (a science dedicated to the dating of rocks and geological phenomena). He developed a new method of dating rocks, based on the decay of radioactive rubidium-87, which becomes strontium-87 by emitting a beta particle. Strassmann showed that rubidium-87 is one of the most abundant radioactive isotopes in the earth's crust (with a presence of 33.6 parts per million), and that its half-life is also the longest (estimated at about 47 billion years). Thus, according to his method, the age of rocks can be calculated by analyzing their proportions of rubidium and strontium.

Already at the Kaiser Wilhelm Institute in Berlin, Fritz Strassmann was requested by Otto Hahn and Lise Meitner to collaborate with them. Together they undertook a series of experiments consisting of bombarding various elements with neutrons. In most nuclear reactions, atoms change from a stable form to a radioactive form, or change into slightly heavier or slightly lighter atoms. However, with uranium, the results obtained were completely different. For example, copper (element number 29 on the periodic table of elements) can change from a stable form to a radioactive form, or be transformed into zinc (element number 30) or nickel (element number 28).

However, what Strassmann and Hahn observed (by that time Meitner had already left Germany because of anti-Semitic persecution), was a much more important nuclear transformation: the splitting of a uranium atom (element number 92), when bombarded by a neutron, in two elements with a much lower atomic number, such as krypton (element number 36) and barium (element number 56). The reaction received the name fission in analogy with the process of cell fission by which a cell divides in two. The phenomenon would be explained by the German physicist Lise Meitner and her nephew Otto Frisch.

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