Jensen, Johannes Hans Daniel (1907-1973)

German physicist who shared the 1963 Nobel Prize for Physics with Maria Goeppert-Mayer and Eugene Wigner for work on the detailed characteristics of atomic nuclei. Jensen was born in Hamburg and studied there and at Freiburg. He became professor at the Institute of Technology in Hanover 1941 and at Heidelberg 1949. Jensen proposed in 1949 the theory that a nucleus has a structure of shells or spherical layers, each filled with neutrons and protons. He explained it in Elementary Theory of Nuclear Shell Structure 1955, written with Goeppert-Mayer, who had developed the shell theory independently. Jensen and his colleagues also suggested that there is a very strong interaction between the spin and the orbit of a particle and that the lower of two states is always the one with angular momentum parallel rather than antiparallel. This may account for magic numbers, certain numbers of neutrons or protons that fill the shells of particularly stable elements.