100th birthday from James Franck and Max Born - Germany / Federal Republic of Germany 1982 - 80 Pfennig

One of the most momentous steps in the development of thinking about nature was the creation of quantum theory in the first third of our century. It shows that the microscopic background (atoms and electrons) with which we interpret the direct experiential foreground of natural phenomena - including the material properties - is not conceivable in the same way as the latter. With the exact knowledge of the limitations of the concepts thereby given, quantum theory has become the basic science for the understanding of the material world. James Franck (26.08.1882-21.05.1964) and Max Born (11.12.1882-5.05.1970) have made essential contributions to the foundation and design of this theory. In 1913 Franck, together with the young G. Hertz, experimentally proved the fundamental relation between the energy converted by an atomic process and the frequency of a light oscillation (E = hv). Electrons of precisely measured kinetic energy produced a light radiation of a certain frequency when it hits atoms. The role of the electron in the illumination of substances and in chemical processes remained the subject of Franck's research throughout his life, most recently in photosynthesis, the basic process of plant life. Characteristic of his thinking was his intuitive understanding of quantum theory, his working with ideas while at the same time being aware of their limitations. Born set himself the task of explaining and calculating the mechanical, electrical and optical properties of the bodies from their construction of atoms. Turning to fundamental questions of quantum theory, he succeeded in 1925 with W. Heisenberg and P. Jordan in the mathematical design of Heisenberg's first version of a strict quantum mechanics. His interpretation of certain quantities in a second, different version as probabilities contributed significantly to the rapid physical understanding of the theory, which first arose in abstract mathematical form. Characteristic for him was the demand of the mathematical consistency of a theory and the skepticism against still unclear early designs. At the height of their work, from 1921 to 1933, Franck and Born were professors of physics at the University of Göttingen. They have contributed to their world-wide reputation. The almost daily scientific conversation with such different thinking style, the human warmth of the two, the large crowd of students and long-staying young talented researchers have created a unique, hardly repeatable atmosphere in which to grow talents. The happy years came to an end when Franck and Born had to leave Göttingen University in 1933. Franck found in Chicago, Born in Edinburgh, the opportunity to continue the research. Both have become known as callers to political reason and for the correct assessment of the dangerous possibilities offered by the newly unleashed forces of nature. (Text: Department of Physics of the University of Göttingen)