Ben Jamin Mottelson (1926–2022)

Portrait of Ben Mottelson sitting on a sofa with a bookshelf behind him

Credits: Ola Jakup Joensen, Niels Bohr Institute

Benjamin Mottellson was an American-born physicist specializing in theoretical research on the structure of atomic nuclei. In the 1950s, in close collaboration with his Danish colleague Augenirs, Mottellson developed a theory called the collective model. This was much better than the previous nuclear model. This model not only stimulated fresh experiments in nuclear physics, but also proved to be fertile across disciplines by associating nuclei with areas such as superconductivity and neutron star physics. Mottellson and Bohr (whose father Niels won the Nobel Prize in 1922) shared the 1975 Nobel Prize in Physics with American nuclear physicist James Rainwater.

Mottellson, who died at the age of 95, spent almost all of his research career in Copenhagen, where he was a leader in the nuclear physics community. His work revitalized the Institute of Theoretical Physics at the University of Copenhagen, founded by Niels Bohr in 1921 and renamed the Niels Bohr Institute in 1965. Mottellson’s enthusiasm, extroversion and widespread interest have made him a valuable teacher and teacher not only in Denmark but abroad.

Born in Chicago, Illinois in 1926, Mottellson graduated from secondary school during World War II and was subsequently sent by the US Navy to Purdue University in West Lafayette, Indiana for training officers. He earned his bachelor’s degree from Purdue University in 1947 and worked with Julian Schwinger, who won the 1965 Nobel Prize for his contribution to quantum electrodynamics at Harvard University in Cambridge, Massachusetts. I continued. Funded by a fellowship from Harvard University and the US Atomic Energy Commission, Mottellson then left the United States to work in graduate school at the Institute of Theoretical Physics in Copenhagen.

Until 1950, the preferred model of nuclei was the shell model. This is because the nucleons (protons and neutrons) occupy the quantum level, that is, the shell like an atomic electron. However, Ohge Niels suggested that the nucleus could rotate like a viscous liquid ellipsoid. It’s like a spinning raw egg. As soon as Mottelson arrived in Copenhagen and met Bohr, they began to work together on a nuclear model. In his 1975 Nobel Prize lecture, Mottellson described what became his lifelong collaborative research program as “a harmonious dialogue between relatives through years of common experience and co-developed understanding.”

In 1953, in a 174-page essay published by the Royal Danish Academy of Sciences and Literature, Bohr and Mottellson published what became known as a collective or unified model of nuclear structure. It incorporates the functionality of the shell model and the rival droplet model, and the nucleons are drawn to resemble the molecules of a water droplet. Being one of the first things Mottellson pointed out, the model predicted that the interaction of charged particles would result in a phenomenon called Coulomb scattering. This was confirmed by experiments in Copenhagen and elsewhere. The Bohr-Mottellson set model has stimulated a wide range of experiments in nuclear physics, including the study of spectra generated by the rotation of nuclei.

In 1957, the BCS (or Bardeen-Cooper-Schrieffer) theory was proposed to explain the microscopic aspects of superconductivity. Later, Bohr and Mottellson realized that nuclear material had properties similar to those of superconducting solids, and wrote this insight in collaboration with American physicist David Pines (A. Bohr), an important 1958. I made a presentation in the paper of the year. et al.Pastor of Physics 110 110, 936; 1958). By extending BCS theory to the nuclear domain, three physicists were able to explain the difference in stability between isotopes with even and odd numbers of nucleons. In the 1960s, Bohr and Mottellson continued to study nuclear structure, ambitiously aiming for a comprehensive and comprehensive treatment of the entire region. The first result of their efforts appeared in 1969 and had a monumental first volume. Nuclear structure, Completed in Volume 2 six years later — the same year they won the Nobel Prize. This was the latest Nobel Prize awarded for research in nuclear physics.

In 1953, Mottellson took up a research position in the Theoretical Research Group, where CERN, the newly established Center for Nuclear Physics and High Energy Physics, was formed at the Institute of Theoretical Physics in Copenhagen. When the Theoretical Group moved to Geneva, Switzerland in 1957, Mottellson was appointed as a professor at the nearby Nordic Institute for Theoretical Physics (Nordita), which was established in the same year. In 1971, Mottelson became a naturalized Danish citizen. With the exception of his visiting professor, he remained in Nordita until his retirement in 1994.

Although retired, he continued his research as an emeritus professor and a temporary lecturer. In 2015, an 88-year-old physicist contributed a paper on the low-temperature, low-density state of matter known as the Bose-Einstein condensate (JC Cremon). et al. Pastor of Physics A 91, 033623; 2015). Another topic that Mottelson worked on in his later years was the foundation of quantum mechanics, which he investigated in a paper written by Aage Bohr and Ole Wolfbeck. Mottellson and his co-authors wanted to know what quantum mechanics really is and why the equation works so well. They say that the proper basis of quantum mechanics is the “genuine accidental principle”, which has dimensions of space and time but no mass, a new geometric worldview rather than an atom. Insisted that it means. A radical interpretation of non-causal events, such as detector clicks, has led to the claim that Planck’s quantum constants do not exist in the underlying theory.

Ben was an active man who loved swimming, cycling and music. He cycled 12 kilometers daily from his home in the northern suburbs of Copenhagen to the Niels Bohr Institute. He will first be remembered for his original contribution to the theory of nuclear structure. But he will also be remembered and overlooked because of his warm human qualities and widespread interest beyond physics.

Competing profits

The author does not declare competing interests.

Leave a Comment