JAMES FRANCK (1925) 145

JAMES FRANCK (1925) 145

James Franck was born on August 26, 1882, in Hamburg, Germany, the son of a Jewish banker. His mother, Rebecka (née Nachum-Drucker), came from a family of rabbis, while his father, Jacob Franck, was deeply religious. David Nachmansohn used to say that James, in contrast with his father, was not orthodox but very liberal. At a later age James Franck himself would state that science was his god and nature his religion. Still, he was very proud of his Jewish cultural heritage. Most scientists earn recognition from the quality of  their contributions to the development of our understanding of nature, some earn recognition because of the public stances they take, at personal peril, on moral issues, and some earn recognition by the positions they take on important issues at the intersection of science and politics. Only a very few earn recognition for all three reasons. James Franck was one such scientist. He made early very important contributions to the experimental basis for the quantum mechanical description of atoms and molecules, for which he was awarded the Nobel Prize in Physics in 1925, and to the understanding of the physical processes underlying photochemical processes and reactions. He was elected to membership in the National Academy of Sciences in 1944

The early education of James Franck, as was the style of those times, was strong in classics. He studied at the Wilhelm Gymnasium in Hamburg, and as he was fond of relating, he was anything but a brilliant scholar, and only just managed to pass the high-school final examinations, which enabled him to enroll at a university. His father sent him to the University of Heidelberg to study law and economics, to prepare him to eventually join the family firm. However, it was James’s desire to study science, despite his father’s wishes, and for two semesters he studied chemistry and geology in Heidelberg. It was there that he met Max Born. The two became lifelong friends and, as Born wrote, neither the professors nor the romantic atmosphere of the town were the most important things in his life, rather it was his friendship with Franck. Born and other friends supported James Franck in his efforts to persuade his father to agree to change the course of his studies toward science. Then, in 1902 he moved to Berlin to study physics, where his principal tutors were Emil Warburg and Paul Drude.

Franck’s student Werner Kroebel noted that Franck began the scientific work for his thesis by converting on his own initiative a seemingly unimportant subject proposed to him by his professor into highly significant research on ion mobilities. Under the supervision of Warburg, Franck obtained his doctorate degree in 1906, for research on the mobilities of ions in gaseous discharges. Such research themes were very popular at the time, since they were meant to clarify the atomic structure of matter. After a short stay in Frankfurt-am-Main, Franck returned to Berlin as an assistant in Heinrich Rubens’s laboratory. There he began his exploration of the electronic structure of atoms and molecules and the elementary processes associated with collisions between atoms. He invoked his previous studies of ion mobility, as well as spectroscopic investigations with R. W. Wood, on the connection between the quantum hypothesis and fluorescence quenching of iodine by foreign gases, to explore electron affinities of atoms and molecules. Together with his younger  colleague and friend Gustav Hertz he carried out seminal studies of elastic collisions between electrons and inert gas atoms. Franck and Hertz laid the foundation for the development of what we now call electron impact spectroscopy (i.e., the study of inelastic collisions between electrons and atoms and/or molecules). In 1911 James Franck obtained the Venia legendi for physics to lecture at the University of Berlin. When the First World War broke out in 1914, he volunteered to join the army as a private. He was wounded, decorated with the Iron Cross 1st Class, and returned as a lieutenant. In spite of his Jewish origin he became an officer, a sign of his courage and the quality of his military activities. He was then assigned to a research group led by Fritz Haber, Pioneer Regiment 35-36, which was involved in chemical warfare. As Franck reported, he became Haber’s confidential assistant at the front; it was his job to inform Haber of the various battle actions and how they had developed (Stolzenberg, 2004).

In 1920 James Franck moved to Göttingen to serve as professor of experimental physics and director of Physical Institute II. Initially the laboratory was completely bare of equipment, and James Franck bought apparatus from his private resources; it quickly became one of the most important world centers of research in atomic and molecular physics. All reports of the character of Franck’s laboratory emphasize how different it was from almost all other laboratories in German universities by virtue of the warmth and informality of the student-professor interactions, the mutual respect between all laboratory members, and the open and spirited discussions of scientific problems. Franck became a leading scientific and personal figure in Göttingen, and was extremely well liked and respected by the entire university community. In 1925 when he was awarded the Nobel Prize, the students formed a torchlight procession as a celebration in his honor. James Franck was extremely popular as a teacher, selecting the very best applicants to his institute from Germany and other countries. Among his students were Blackett, Hanle, Herzberg, von Hippel, Rabinowitch, and Sponer. His institute also attracted outstanding scientists to Göttingen as visiting professors, some of whom were K. T. Compton, E. U. Condon, J. E. Mayer, and G. Scheibe.

Franck was also involved in the training of graduate students in theoretical physics and was present at the Ph.D. examination of Robert Oppenheimer on the Born-Oppenheimer separation of electronic and nuclear motion. Oppenheimer was quoted to have said: “I got out of there just in time. He was beginning to ask questions.”

Franck’s remarkable scientific activities in Göttingen were terminated by the rise of the National Socialist (Nazi) party to power in Germany. After the federal election in Germany in 1932 the Nazi party held 37 percent of the seats in the Reichstag, and on January 30, 1933, Adolf Hitler was appointed chancellor of Germany. Although Hitler initially headed a coalition government, he quickly eliminated his government partners and began the process of passing discriminatory legislation. On April 17, 1933, James Franck became the first German academic to resign in protest of the laws excluding Germans of Jewish descent from government office. Franck’s war record exempted him from the racial exclusion laws, but he chose to risk his career and personal safety by resigning his position so as not to be forced to dismiss his Jewish colleagues and students. In his letter of resignation Franck wrote to the minister of education that his action was an inner necessity to him because of the attitude of the German government toward the Jews. In a letter to the rector of the university he stressed that it was intolerable that German Jews should be treated as aliens and enemies of the state. He published his statement of resignation and protest in the national press. As stated by Eugene Rabinowitch: “He was willing to act where others drifted silently.” Franck did not intend to leave Germany immediately, hoping to be able to conduct useful work outside the university and help fight the Nazi regime. But the conditions of the Jews deteriorated rapidly, and no external work or resistance was possible. In the fall of 1933 Franck left Germany. From 1933 to 1938 Franck was successively a visitor at Johns Hopkins University (1933-1934), a visitor at the Bohr Institute in Copenhagen (1934-1935), and then professor of physics at Johns Hopkins University (1935-1938). In 1938 he became a professor of physical chemistry at the University of Chicago, where he remained until retirement as professor emeritus in 1947 while retaining a continued association as head of the Photosynthesis Research Group until 1956 and as a member of the Institute for Radiobiology and Biophysics until his death in 1964.

Franck’s approach toward theories of photochemical processes in complex biological systems was summarized in a 1941 article with K. F. Herzfeld, where he stated that “a theory by its own nature can contain only a partial truth.” His theoretical work addressed the central issues of electronic energy transfer, the functions of independent types of photosynthetic units, and the mechanism of the primary photosynthetic process. In the context of electronic energy transfer to the photosynthetic reaction center, Franck and Teller (1938) considered exciton transfer in a one-dimensional linear array of chlorophyll molecules, reaching the conclusion that this mechanism was too slow to bring the excitation energy to the reaction center. An extension of the excitonic model to two and three dimensions by Bay and Pearlstein (1963) and by Wilse Robinson (1967) demonstrated that electronic energy transfer in higher dimensions is fast enough to induce the primary process within the reaction center. The central question raised by Franck regarding the mechanism of electronic energy transfer, from the antenna to the reaction center in the photosynthetic apparatus, is still under active exploration, using the theoretical concepts and experimental techniques of femtosecond spectroscopy (Scholes and Fleming, 2006).

James Franck’s evolution from dedicated scientist uninterested in politics into a moral leader was driven by his sense of social responsibility. He saw clearly that responding to the discriminatory Nazi regime legislation of 1933 was a fundamental issue, to be based on principle, and he eschewed available compromise and personal expedience. This sense of social responsibility was accompanied by a strong personal charity. From 1933 on, he assisted German scientists and other professionals expelled by the Nazi regime to find employment wherever available. After World War II ended, understanding the devastation wrought by the war and looking beyond the excesses of the Nazi regime, he responded to many appeals from Germany for food, clothing, and money.

James Franck was a great scientist who changed our perception of the world, and he was a symbol and pioneer for a new generation of scientists who recognized their great responsibility toward mankind. His friend Peter Pringsheim (1952) admired Franck’s “obsession with science,” and this predominant quality was described by Lise Meitner (1964) in her obituary statement.

James Franck’s personal life is sketched in David Nachmansohn’s book (1979) and in the records of the Nobel lectures (http://nobelprize.org/nobel_prizes/physics/ laureates/1925/franck-bio.html). In 1911 he married Ingrid Josephson of Goteborg, Sweden, whom he met in Berlin, where she had come to study music; they were deeply devoted to each other. Ingrid died in 1942 in Chicago at age 59. Four years later Franck married Henrietha Sponer, then professor of physics at Duke University, whom he had known for many years. Franck had two daughters, Dagmar and Elizabeth. Dagmar married Arthur von Hippel, who became professor of physics at the Massachusetts Institute of Technology, and Elizabeth married Hermann Lisco, who became professor of anatomy at Harvard University. Franck was always proud of his Jewish heritage. David Nachmansohn recollected that he was not a Zionist. But in 1934 when the Jewish chemist and leader Chaim Weizmann asked Franck whether he would be willing to continue his work in Israel (at that time Palestine), he strongly expressed great interest. Regretfully, many of Weizmann’s plans for building science in Israel at that time were unfeasible, because of lack of funds and infrastructure.

The Israeli science community, recognizing his contributions, paid tribute to James Franck. In 1954 he was awarded an honorary doctorate by the Technion–Israel Institute of Technology. In 1988 the Binational German-Israeli James Franck research program on laser-matter interaction was initiated by Raphael Levine, Edward Schlag, and one of us (J. J.) and established in five Israeli universities: the  Hebrew University of Jerusalem, Tel Aviv University, the Technion–Israel Institute of Technology, Ben Gurion University, and Weizmann Institute of Science.

Franck’s admirable personal character was manifested again after the end of World War II, when he was able to look beyond the horrors of the Nazi regime and renew his personal, cultural and scientific relations with Germany. Only a few years after the end of World War II, he consented to being honored by German academic and research institutions. In 1951 he was the recipient of the Max Planck Medal of the German Physical Society, and in 1957 he was awarded an honorary doctorate (Dr. rer. nat.) by the University of Heidelberg. He remained attached to the city of Gottingen, receiving its honorary citizenship in 1953. At the same time, Born and some other old friends of Franck were awarded, together with him, honorary Doctor’s degrees. It was an odd turn of fate that he died during a visit to Göttingen on May 21, 1964, at the age of 81.