J. Hans D. Jensen


Nobel Prize (1963)
Nobel Prize in Physics


Born in Hamburg on June 25, 1907, J. Hans D. Jensen began studying physics, mathematics, physical chemistry and philosophy at the Universities of Hamburg and Freiburg. He obtained his PhD in 1932 in Hamburg, and became a scientific assistant at the Institute for Theoretical Physics of the University of Hamburg. In 1949 he was appointed Professor at the University of Heidelberg.

Since the early 1930's, scientists had been seeking to construct a theoretical model of the atomic nucleus. During this time, a German physicist, Walter Elsasser, suggested a model portraying protons and neutrons in some kind of orbit with their energy corresponding to the physical laws laid down by quantum theory. Meanwhile, Jensen's first research applied quantum mechanics, the mathematical theory of matter and radiation's interaction, to the study of crystals, whose atoms are arranged in a repetitive pattern. He observed the properties of crystals under high pressure and was also interested in constructing a theoretical model of the atomic nucleus. By 1947, his initial investigation of crystals advanced to an examination of the recoil distribution of radiation in molecules and crystals. Jensen showed that rays or particles discharged by the nuclei of radioactive atoms are caught within a crystal in a backward movement similar to the recoil of a rifle. The importance of the recoil research would advance the world's understanding of science significantly. Several years later, the University of Heidelberg offered Jensen the position of Professor of Physics. Continuing his research while teaching, he proposed a model of a nuclear structure of protons and neutrons grouped in onion-like layers of concentric shells. He suggested that the nucleons spun on their own axis while they moved in an orbit within their shell and that certain patterns in the number of nucleons per shell made the nucleus more stable. Though many physicists were skeptical because of its description of strong spin-orbit coupling, contrary at the time to notions about the motion of nucleons, the years that followed confirmed Jensen's nuclear shell model hypothesis.

Following his groundbreaking work on the structure of the nucleus, Jensen accepted a series of visiting professorships at academic institutions throughout the United States and worked on radioactivity, significantly advancing the understanding of the phenomenon. Throughout the 1950's, he taught at the University of Wisconsin, the Institute for Advanced Study in Princeton the University of California at Berkeley, and Indiana University. While at Indiana University as a visiting professor, for one year Jensen collaborating with other members of the Physics Department, making further advancements in his research. Eventually, his critical discoveries about the structure of atoms led to his Nobel Prize in Physics in 1963.