Friedrich Strassmann, co-discoverer of the fission of uranium

February 22, 1902, Boppaard (Germany) - April 22, 1980, Mainz (Germany)

Friedrich Wilhelm "Fritz" Strassmann studied physics and chemistry at the Technical University of Hannover. In 1929, he received his doctorate and began his fruitful career as a teacher and researcher.

Early in his research career, Strassmann was concerned with radioactive elements used in geochronology (the science of dating rocks and geological phenomena). He developed a new method of dating rocks, based on the decay of radioactive rubidium-87, which is converted into 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 (33.6 parts per million) and that its half-life is also the longest (estimated at 47 billion years). Thus, according to his method, the age of rocks can be calculated by analyzing their rubidium and strontium ratios.

Shortly afterward, he joined the prestigious research team at the Kaiser Wilhelm Institute in Berlin, Germany, where he had the opportunity to work together with Otto Hahn and Lise Meitner. Together they undertook a series of experiments involving bombarding various elements with neutrons. In most nuclear reactions, atoms change from a stable form to a radioactive form or are transformed into slightly heavier or slightly lighter atoms. With uranium, however, the results were completely different. For example, copper (element number 29 in the periodic table of elements) can change from a stable form to a radioactive form, or transform into zinc (element number 30) or nickel (element number 28).

During World War II, Otto Hahn and Fritz Strassmann continued to work in the field of nuclear physics, focusing on the study of uranium fission products such as barium and krypton. However, contrary to Hitler's policy, they steadfastly refused to participate in a nuclear weapons programme. Hahn even confessed to Strassmann that if he ever suspected that his work had helped Hitler to get his hands on the atomic bomb, he would unhesitatingly take his own life on the spot.

However, what Strassmann and Hahn observed (at 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, into two elements of much lower atomic number, krypton (element number 36) and barium (element number 56). The reaction was called fission in analogy to 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. Nuclear fission had been discovered.

After the end of the war, both Strassmann and Hahn regained their status. Hahn was thus able to collect the Nobel Prize that had been secretly awarded 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. He was later appointed director of the Max Planck Institute for Chemistry.

During his lifetime, Fritz Strassmann received numerous awards such as the seal of the hometown Boppard (1960), the prestigious Enrico Fermi Prize for his contributions to nuclear chemistry and his extensive experimental studies, culminating in the discovery of fission, by Chairman Johnson of the US Atomic Energy Commission (1966), an honorary citizenship of Mainz (1972) and the posthumous Righteous Among the Nations Award (1985). An asterioid was also named after him in 2001.