Friedrich Wilhelm Strassmann (German: [fʁɪt͡s ˈʃtʁasˌman]; 22 February 1902 – 22 April 1980) was a German chemist. In December 1938, he and Otto Hahn discovered that barium was produced when uranium was bombarded with neutrons. This finding was important evidence that showed a new process called nuclear fission, which was later explained and published by Lise Meitner and Robert Frisch.
In their next paper about nuclear fission in February 1939, Strassmann and Hahn predicted that more neutrons would be released during fission. This discovery suggested the possibility of a nuclear chain reaction.
Early life
Friedrich Wilhelm (Fritz) Strassmann was born in Boppard, Germany, to Richard Strassmann and Julie Strassmann (née Bernsmann). He was the youngest of nine children. He grew up in Düsseldorf and became interested in chemistry at a young age. He performed chemistry experiments at home. His family had limited money, and his father died when he was young, which made their financial situation worse. Because of money problems, Strassmann had limited choices about where to study and what subjects to pursue.
Strassmann began his formal chemistry studies in 1920 at the Technical University of Hannover. He supported himself by tutoring other students. He earned a diploma in chemical engineering in 1924 and a PhD in physical chemistry in 1929. His PhD research focused on how iodine dissolves and reacts with carbonic acid in gas form, which gave him experience in analytical chemistry. His doctoral advisor was Hermann Braune.
Later, Strassmann received a partial scholarship to the Kaiser Wilhelm Institute for Chemistry in Berlin-Dahlem, starting in 1929. There, he studied radiochemistry with Otto Hahn, who helped renew his scholarship twice. When his scholarship ended in September 1932, Strassmann continued working in Hahn’s laboratory as a research student without a stipend but without having to pay tuition.
Activities during Nazi rule
In 1933, Strassmann left the Society of German Chemists after it became part of a corporation controlled by the Nazi government. He was banned from working in the chemical industry and could not earn his habilitation, which was needed to work as an independent researcher in Germany at that time. Lise Meitner helped Otto Hahn find a job for Strassmann as a special assistant at half pay. Strassmann believed he was lucky because, even though he loved chemistry, he valued his freedom more than anything else. He once said, "I would rather break stones for a living than lose my freedom."
Strassmann’s wife, Maria, supported his decision not to join the Nazi Party. During World War II, the couple hid a Jewish musician named Andrea Wolfenstein in their home for months, even though doing so put their lives and their young son’s life in danger. The housekeeper and neighbors were supporters of the Nazi regime.
During the war, Strassmann continued his research in radiochemistry but did not work on weapons. He strongly opposed the Nazi government and once said, "If my work helped Hitler build an atomic bomb, I would kill myself."
Hahn and Meitner used Strassmann’s skills in chemistry to study the results of bombarding uranium with neutrons. Among the three scientists, only Strassmann stayed focused on their experiments. Meitner had to leave Germany because she was Jewish, and Hahn had many administrative responsibilities.
In 1937 and 1938, scientists Irène Joliot-Curie and Paul Savič reported findings about uranium exposed to neutrons but could not identify the new substances formed. Strassmann and Hahn discovered that barium was a major result of this process. This finding was surprising because uranium has an atomic number of 92, while barium has an atomic number of 56, a large difference.
In December 1938, Hahn and Strassmann sent a report to Die Naturwissenschaften describing their discovery of barium as a product of neutron bombardment of uranium. In January 1939, Robert Frisch confirmed their results. Frisch and Meitner explained that the process was nuclear fission, a term they introduced. In 1944, Hahn was awarded the Nobel Prize for Chemistry for discovering nuclear fission, even though Strassmann was recognized as a key collaborator.
From 1939 to 1946, Strassmann worked at the Kaiser-Wilhelm Institute, studying the fission products of thorium, uranium, and neptunium. His research helped scientists understand the radiochemistry of actinide elements. He developed methods to determine the age of minerals and other non-living materials using the half-life of radioactive elements and the buildup of decay products. In 1936 and 1937, Strassmann and Ernst Walling created the rubidium-strontium dating method, and Strassmann continued this work in 1942 and 1943. His methods, called emanation methods, were important for the field of geochronology.
In 1942, Hahn and Strassmann published a report titled Zur Folge nach der Entstehung des 2,3 Tage-Isotops des Elements 93 aus Uran ["Following the formation of the 2.3-day isotope of element 93 from uranium"] in Kernphysikalische Forschungsberichte, an internal publication of the German Uranverein. These reports were classified as "Top Secret" and had limited distribution. The authors were not allowed to keep copies, and the documents were taken by Allied forces during Operation Alsos in 1945. In 1971, the reports were declassified and returned to Germany. They are now stored at the Karlsruhe Nuclear Research Center and the American Institute of Physics.
In 1944, the Kaiser-Wilhelm Institute was heavily damaged by bombing on February 15 and March 24. Because of the destruction, the institute temporarily moved to Tailfingen (now Albstadt) in the Württemberg district, where it operated in a textile factory owned by the Ludwig Haasis company.
Post-war
In April 1945, Hahn and other German scientists were captured as part of Operation Epsilon and held at Farm Hall, near Cambridge, England. During Hahn’s absence, Strassmann became the director of the chemistry section at the institute. In 1946, Strassmann became a professor of inorganic chemistry and nuclear chemistry at the University of Mainz.
The institute had two departments: Mass Spectrometry and Nuclear Physics, which were led by Josef Mattauch, while Strassmann directed the Nuclear Chemistry department. Mattauch became the institute’s director. Later, Mattauch developed tuberculosis and was absent from his position. In 1948, Strassmann acted as director until Mattauch returned. In 1949, the Kaiser-Wilhelm Institute was renamed the Max Planck Institute for Chemistry and moved from Tailfingen to Mainz, Germany. In 1950, Strassmann officially became the institute’s director. When Mattauch returned in 1951, disagreements arose about how resources were divided between their departments.
In 1953, Strassmann stepped down as director to focus on research and teaching at the University of Mainz. He worked to strengthen the department’s programs and taught students directly. Strassmann began this work with limited space and funding. He negotiated with the university and the company Badische Anilin- und Soda-Fabriken (BASF) to create a new institute at the university focused on nuclear chemistry. He also asked the German government to fund a neutron generator, a nuclear reactor for research, and a special institute for nuclear chemistry. The Institute for Nuclear Chemistry officially opened on April 3, 1967.
In 1957, Strassmann was part of the Göttingen Eighteen, a group of German nuclear scientists who wrote a statement opposing plans to give the German army tactical nuclear weapons.
Strassmann retired in 1970 and died on April 22, 1980, in Mainz.
In 1966, U.S. President Lyndon Johnson honored Hahn, Meitner, and Strassmann with the Enrico Fermi Award. The International Astronomical Union named an asteroid, 19136 Strassmann, after him.
On July 16, 1985, Professor Fritz Strassmann was posthumously recognized by the Yad Vashem Institute in Jerusalem as one of the Righteous Among the Nations.
Personal life
On July 20, 1937, Strassmann married Maria Heckter, who was also a chemist. Strassmann taught himself how to play the violin. He met Maria Heckter through a group of young musicians that both of them were part of. They had a son named Martin.
Maria passed away from cancer in 1956. In 1959, Strassmann married Irmgard Hartmann, a journalist. He had known Hartmann for many years because she was also a member of the same group of young musicians that Strassmann and his wife Maria had been part of.