The structure of the atomic nucleus In the same way as the electrons surrounding the atomic nucleus are in different energy levels or shells, the nucleons in the atomic nucleus are also in different shells. Among the first to study the energy levels of the atomic nucleus was Helge Tyr?n in Uppsala. Together with his collaborators he studied the energy required to knock out protons from the atomic nucleus. The results confirmed a theory for the shells of the atomic nucleus which had been put forward earlier. At the The Svedberg Laboratory in Uppsala one is still doing research on the shell structure of different atomic nuclei and collective phenomena such as vibrational and rotational excitations. The Gustaf Werner cyclotron at TSL (the The Svedberg Laboratory) The Gustaf Werner cyclotron was built in the late 1940's and was for a short while the most powerful accelerator in Europe. It has since then been upgraded and is today used for medical and nuclear physics research. It is also used as an injector for the so called CELSIUS ring, where research is done both in nuclear and particle physics. Based on fundamental research in nuclear physics a lot of applications have been developed, such as nuclear power and medical applications. Dating of archaeological material can also be made with the help of nuclear technology by exploiting the lifetime of radioactive isotopes. I was born in Copenhagen on June 19, 1922, as the fourth son of Niels Bohr and Margrethe Bohr (n?e N?rlund). During my early childhood, my parents lived at the Institute for Theoretical Physics (now the Niels Bohr Institute), and the remarkable generation of scientists who came to join my father in his work became for us children Uncle Kramers, Uncle Klein, Uncle Nishina, Uncle Heisenberg, Uncle Pauli, etc. When I was about ten years old, my parents moved to the mansion at Carlsberg, where they were hosts for widening circles of scholars, artists, and persons in public life. I went to school for twelve years at Sortedam Gymnasium (H. Adler's f?ellesskole) and am indebted to many of my teachers, both in the humanities and in the sciences, for inspiration and encouragement.
I began studying physics at the University of Copenhagen in 1940 (a few months after the German occupation of Denmark). By that time, I had already begun to assist my father with correspondence, with his writing of articles of a general epistemological character, and gradually also in connection with his work in physics. In those years, he was concerned partly with problems of nuclear physics and partly with problems relating to the penetration of atomic particles through matter. I was born in Chicago, Illinois, on July 9, 1926, the second of three children of Goodman Mottelson and Georgia Mottelson (n?e Blum). My father held a university degree in engineering. My childhood home was a place where scientific, political and moral issues were freely and vigorously discussed. I attended primary school and high school in the village of La Grange, Illinois. Graduating from high school during the second world war, I was sent by the U.S. Navy to Purdue University for officers training (V12 program) and remained there to receive a Bachelor of Science degree in 1947. My graduate studies were at Harvard University and my PhD work on a problem in nuclar physics was directed by Professor Julian Schwinger and completed in 1950. Receiving a Sheldon Traveling Fellowship from Harvard University I chose to spend the year (1950-51) at the Institute for Theoretical Physics in Copenhagen (later the Niels Bohr Institute) where so much of modern physics had been created and where there were such special traditions for international cooperation. A fellowship from the U.S. Atomic Energy Commission permitted me to continue my work in Copenhagen for two more years after which I held a research position in the CERN (European Organization for Nuclear Research) theoretical study group that was formed in Copenhagen. With the founding of the Nordic Institute for Theoretical Atomic Physics in Copenhagen (1957) I received a position as professor which I have held since. The spring term of 1959 was spent as visiting professor in the University of California at Berkeley.
The close scientific collaboration with Aage Bohr was begun in 1951 and has continued ever since. We feel that in this cooperation we have been able to exploit possibilities that lie in a dialogue between kindred spirits that have been attuned through a long period of common experience and jointly developed understanding. The lectures that are published in this volume attempt a discussion of the main influences that we have built on and the viewpoints that have been developed in this collaboration. It has been our good fortune to work closely together with colleagues at the Niels Bohr Institute and Nordita, including the many outstanding scientists who have come from all parts of the world and have so enriched the scientific atmosphere and personal contacts. Married Nancy Jane Reno, 1948 (dec. 1975); 3 children, Malcolm Graham (1950), Daniel John (1953), Martha (1954). Married Britta Marger Siegumfeldt, 1983.*
