Ben Roy Mottelson is an American-Danish nuclear physicist. Brought up in the suburbs of Chicago, he graduated from high school, when the Second World War was at its peak and was immediately enlisted in the military. However, he spent the war years at the University of Purdue, getting trained to become a Navy Officer. After the war, he earned his bachelor’s degree from Purdue University and then his PhD from Harvard University. Subsequently, he traveled to Copenhagen, where he joined the Institute for Theoretical Physics (later the Niels Bohr Institute) on fellowship. There, he began collaborating with Aage Bohr and experimentally confirmed that movement of subatomic particles can alter the shape of the nucleus. This work, which earned them the Nobel Prize in Physics two decades later, not only challenged the established theories, but also stimulated further studies in this field. Soon after this, he obtained employment, first at the Theoretical Study Group of European Organization for Nuclear Researc, and then at Nordisk Institut for Teoretisk Atomfysik, both in Copenhagen. Later he became a naturalized citizen of Denmark and now lives in Copenhagen.
Childhood & Early Life
Ben Roy Mottelson was born on 9 July, 1926 in Chicago, United States of America. His father, Goodman Mottelson, held a university degree in engineering. His mother’s name was Georgia Mottelson (née Blum). He was the second of his parents’ three children.
Ben spent his early years in La Grange, a suburb located just outside the city of Chicago. During that time, the village had a very healthy atmosphere, where political, moral and scientific issues were openly and vigorously discussed and young Ben was highly influenced by this.
In La Grange, Ben Roy Mottelson attended Lyons Township High School. Upon graduating from there in 1943, he joined the U.S. Navy as part of his war service and was sent to Purdue University to be trained as an officer under the V-12 Navy College Training Program.
Once the war ended, he stayed back at the Purdue University to complete his undergraduate studies, finally receiving his Bachelor of Science degree in 1947. Thereafter, he joined Harvard University for his graduate work and working under Professor Julian Schwinger, he earned his PhD in nuclear physics in 1950.
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Soon after receiving his PhD in 1950, Mottelson received one-year Sheldon Traveling Fellowship from the Harvard University. With it, he traveled to Denmark and joined the Institute for Theoretical Physics (later the Niels Bohr Institute) in Copenhagen.
Initially, he planned to spend only the 1950-1951 session at Copenhagen. At that time, the Institute was run by eminent physicist and Nobel laureate Niels Bohr. Under him, the institute grew a tradition of international cooperation and Mottelson enjoyed the atmosphere there.
Fortunately in 1951, he received another fellowship; this time from the U.S. Atomic Energy Commission. It allowed him to stay at Copenhagen for two more years and start collaborating with Aage N. Bohr on the distortions in the shape of a nucleus.
At that time, two principal theories were being circulated. According to Maria Goeppert-Mayer, in a nucleus, independent particles are arranged in shells. This was known as shell theory. The other was liquid drop model, which describes nucleus as a semi-classical fluid made up of neutrons and protons.
However, none of them could explain all aspects of the properties of an atomic nucleus. In 1950, James Rainwater postulated that a nucleus was like a balloon with balls inside.
He theorized that, just as the moving balls distort the shape of the balloon, subatomic particles moving inside a nucleus also cause distortion on its surface. Working independently, Aage Bohr too had come to the same conclusion.
From 1951 onwards, Mottelson and Bohr worked together to establish this theory experimentally. From 1952 to 1953, they published the results of these experiments in three papers.
In 1953, he obtained appointment at the European Organization for Nuclear Research (CERN) as staff member and became attached to its Theoretical Study Group, based in Copenhagen. Concurrently, he continued his collaboration with Bohr.
He remained at CERN till 1957. The same year, Nordisk Institut for Teoretisk Atomfysik (NORDITA) was founded in the premises of the Institute of Theoretical Physics, Mottelson shifted to the new organization as a professor, a position he held till his retirement.
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In 1959, he spent the spring term as visiting professor in the University of California at Berkeley. All the while he kept collaborating with Bohr and published a two-volume monograph, titled ‘Nuclear Structure’ with him.
The first volume titled, ‘Single-Particle Motion’, appeared in 1969 and the second volume titled, ‘Nuclear Deformations’ was published in 1975. Meanwhile in 1971, Mottelson received Danish citizenship. Concurrently, he also holds the American citizenship.
Mottelson is best known for his experimental work with Aage Bohr, which confirmed that movement of subatomic particles can distort the shape of nuclei. The work not only challenged the accepted notion that all nuclei are perfectly spherical, but also merged Maria Goeppert-Mayer’s shell model with James Rainwater’s liquid drop model.
Awards & Achievements
In 1975, Ben R. Mottelson received the Nobel Prize in Physics jointly with Aage Bohr and James Rainwater "for the discovery of the connection between collective motion and particle motion in atomic nuclei and the development of the theory of the structure of the atomic nucleus based on this connection".
Other than the Nobel Prize, he also received Atoms for Peace Award in 1969 and John Price Wetherill Medal in 1974.
Mottelson is a foreign fellow of the Norwegian Academy of Science and Letters and Bangladesh Academy of Sciences. He is also a member of the Board of Sponsors of the Bulletin of the Atomic Scientists.
He also holds honorary degrees from Purdue University and the University of Heidelberg.
In December 1948, Mottelson married Nancy Jane Reno. The couple had three children - two sons, Malcolm Graham and Daniel John and one daughter, Martha. In 1975, shortly before Mottelson received his Nobel Prize, Nancy Jane Reno died from cancer.
In 1983, Mottelson tied the knot for the second time and married Britta Marger Siegumfeldt.
In his spare time, Mottelson likes to listen to music. He also enjoys bicycle riding and swimming.