Fritz Strassman
Strassman, Fritz (1902-1980) was a German chemist whose work with fellow German chemist Otto Hahn and with Austrian nuclear physicist Lise Meitner led to the discovery of nuclear fission, the splitting of atoms to release tremendous amounts of energy. This discovery resulted in the development of the first atomic bomb.
Friedrich Wilhelm Strassman, the ninth child of a court clerk, was interested in chemistry as a youth. He attended secondary school at Oberrealschule (now Leibniz-Gymnasium) in Dusseldorf, but after graduating he was unable to go on to university because his family could not afford the tuition. Instead, he enrolled at the Technische Hochschule in Hanover, where he continued his studies in chemistry while earning income as a private tutor. He received his doctorate in physical chemistry from there in 1929. That same year he went on to the Kaiser Wilhelm Institute for Chemistry in Berlin (now the Max Planck Institute in Mainz), on a scholarship offered to him by Hahn, then director of the institute.
Remaining at the Institute for Chemistry through the two-time renewal of his scholarship, Strassmann spent the next decade working closely with Hahn and his collaborator Meitner on their research into radioactivity, the emission of radiant energy by certain elements. The study of radioactivity had been given a boost by the discovery, in 1932, of neutrons, subatomic particles that form the nuclei of all atoms except ordinary hydrogen. The Italian physicist Enrico Fermi had subsequently found that using these particles to bombard other elements often caused new elements to be formed. By the mid-1930's Hahn, Meitner, and Strassmann began bombarding uranium atoms with neutrons to discover what new elements this might produce.
At the time it was believed that the elements produced by such a bombardment would have “atomic numbers”—the number of protons in the nucleus of an atom—close to one another and only one or two places higher in number in the periodic table than uranium itself, whose atomic number is 92. It was expected that the experiment, if successful, would produce transuranic elements or elements with atomic numbers higher than uranium's.
As Strassmann and his colleagues' research continued, Hitler was simultaneously rising to power. Strassmann did not support the Nazi regime and by remaining at the institute was able to avoid becoming a member of the Nazi party, but in 1938 Meitner was forced to flee Germany and joined the Nobel Institute in Stockholm.
Hahn and Strassmann continued their research without her, fully expecting their findings to reflect the results already established by all other then-known nuclear reactions, namely the production of elements only one or two numbers different in the periodic table from uranium. But this did not occur. Puzzled by findings that appeared vastly different, Strassmann investigated more deeply and continually found indications of barium being produced by the neutron bombardment. This was difficult for him to reconcile, because rather than being one or two places from uranium's 92, barium's atomic number is different by 36 places, making it a much lighter element. Both Strassmann and Hahn doubted the accuracy of this result, but ultimately Meitner and her nephew Otto Frisch determined the theoretical explanation to prove it correct and boldly confirmed the Hahn-Strassmann findings—that the neutron bombardment had indeed split the uranium atom, producing barium and nuclear fission.
The discovery of nuclear fission presented dramatic new possibilities, both constructive and destructive. It meant the capability to produce nuclear bombs but also provided a tremendous new source of energy for positive purposes. Although neither Strassmann nor Meitner were named as co-recipients for the 1944 Nobel Prize in chemistry, which Hahn alone received for the discovery of nuclear fission, Strassman was awarded the Enrico Fermi Prize in 1966 for his own contributions in this regard along with Meitner and Hahn.
Strassmann is also known for his discovery of a radioactivity-based process to determine the ages of minerals. This process is now a commonly used tool by geologists. He became professor of inorganic and nuclear chemistry at Mainz University after the war, and was instrumental in the establishment of both the new physical facility for the Max Planck Institute of Chemistry (succeeding the Kaiser Wilhelm Institute in Berlin) and the Institute for Nuclear Chemistry. Strassmann also oversaw the construction of the TRIGA Mark II nuclear reactor in Mainz.