Sunday, August 26, 2012
After briefly working in Frankfurt-am-Main Frank returned to Berlin to work as an assistant for Heinrich Ruben, where he studied the structure of the electron shells of atoms and molecules, using atomic collisions. In 1911 Franck became a lecturer at the University of Berlin and when World War I broke out he enlisted and served as a private. In the war he was wounded, awarded the Iron Cross, first class, and then was promoted to lieutenant, despite his Jewish heritage. After his promotion he was assigned to a chemical warfare unit led by Fritz Haber, where he became Haber's assistant. After the war, at Haber's suggestion, Franck took a job at the Kaiser Wilhelm Institute of Physical Chemistry and in 1918 he became the head of the physics department.
Franck worked with Gustav Hertz and they studied the nature of electron collisions with atoms. From this work they were able to demonstrate the quantized nature of energy from electron transitions in atoms. In 1900 Max Planck had hypothesized that the energy emitted by excited atoms (atoms with electrons above their ground or lowest energy states) come in discrete amounts. When excited electrons fall back to their ground states they emit energy in the form of electromagnetic radiation. Because there are distinct electronic orbitals around the nucleus when electrons transition between these their emissions only come at certain wavelengths that depend on which orbitals the electrons transition between. Franck and Hertz's experiments were the first experimental demonstration of the quantized nature of electronic transitions. For these experiments Franck and Hertz were awarded the 1925 Nobel Prize in Physics.
In 1920 Franck moved to Gottingen where he was a professor of experimental physics at the Physical Institute. Franck's laboratory in Gottingen became a center for study of atomic and molecular physics and many important physicists studied there. In 1933, when the Nazis came to power in Germany, Franck moved to Baltimore, Maryland, where he was the Speyer Professor of Physics at Johns Hopkins University. He then spent a year in Copenhagen, Denmark, where he was a guest professor. In 1935 he returned to Johns Hopkins as a physics professor. He stayed at Johns Hopkins until 1938, when he moved to the University of Chicago, becoming a professor of physical chemistry. During World War II Franck was the director of the Chemistry Division of the Metallurgical Laboratory, which was part of the Manhattan Project. In 1945 he served as the chairman of the committee that produced the Franck Report, a document signed by several prominent physicists urging the United States Government not to use the atomic bomb on Japan and predicting the arms race. He became a professor emeritus at the University of Chicago in 1947, but continued doing research with the Photosynthesis Research Group until 1956.
Other honors won by Franck include the Planck Medal from the German Physical Society in 1951, the Rumford Medal in 1955 from the American Academy of Arts and Sciences for his work on photosynthesis and election as a foreign member of the Royal Society of London in 1964.
Franck died suddenly while on a brief trip to Gottingen on May 21,1963, at the age of 81.
Rice, Stuart A. and Jortner, Joshua; "James Franck 1882-1964"; National Academy Press; 2010
James Franck Nobel Biography
James Franck Wikipedia Entry