Famous for his work on the German nuclear energy project, which is more popularly known as the Uranium Club, J. Hans D. Jensen was responsible for making contributions to the separation of uranium isotopes. He was a German nuclear physicist who was one of the notable names during World War II.
He was also a Nobel Prize for Physics winner in 1963 where he shared the award with Maria Goeppert-Mayer, when they proposed the model for the nuclear shell which he devised in 1949. Together with the American scientist Goeppert-Mayer, they wrote the book “Elementary Theory of Nuclear Shell Structure”, which explained their findings.
Early Life and Educational Background
J. Hans D. Jensen was born Johannes Hans Daniel Jensen on the 25th of June in 1907. He was the son of Karl Jensen, a gardener and Helene Ohm Jensen.
His earliest academic interests lay in philosophy, physical chemistry, and mathematics. He studied these courses starting in 1926 at the Universities of Hamburg and Freiburg. He obtained his doctorate in physics in 1932 from the University of Hamburg.
He was coached by Wilhem Lenz, a German physicist who was known for his introduction of a lattice model for ferromagnetism. Jensen completed his Habilitation at the University of Hamburg in 1936.
Career and Academic Involvements
Jensen initially worked as a scientific assistant at the Institute of Theoretical Physics in the University of Hamburg. In 1936, obtained his D. Sc. from Hamburg and he became a Privatdozent (unpaid teacher) at the same university. He then began working with the director of the physical chemistry department, Paul Harteck who was also advisor to the Heereswaffenamt or HWA, Army Ordinance Office for explosives.
Harteck contacted the Reich Ministry of War or Reichskriegsministerium on the 24th of April in 1939 to explain to the authorities how nuclear chain reactions may be of use for military applications. Harteck enrolled Jensen into the Uranverein (Uranium Club) which was founded on the first of September in 1939—the same day the Nazis invaded Poland and initiated The Second World War. This gave the military control of the German nuclear energy project. Together with Harteck, Jensen developed the double centrifuge which was based on a rocking process that facilitated the necessary separation effect.
In 1941, Jensen became Professor of Theoretical Physics in Hannover’s Technische Hochschule (now known as the University of Hanover), becoming extraordinarius professor there in 1946. He had a notable academic career, and in 1949 he was appointed professor at the University of Heidelberg, presenting his shell model for the nucleus of an atom the same year.
In 1950 he co-authored “About gas centrifuges: Enrichment of the xenon, krypton and selenium isotopes by the centrifuge method”.
In 1963 Jensen shared half of the Nobel Prize in Physics with Maria Goeppert-Mayer for their independent proposals of the nuclear shell model. This model proposes that an atomic nucleus has a structure of shells or spherical layers which contain the neutrons and protons of an atom.
Together with the American scientist Goeppert-Mayer, they wrote the book “Elementary Theory of Nuclear Shell Structure” in 1955, which explained their findings. The book mainly concerned the ground-state properties of nuclei and the study of reactions with the removal of nucleons from occupied shells.
Jensen became a member of the Heidelberg Academy of Sciences in 1947 and he was one of the corresponding members of the Max Planck Gesellschaft in 1960.
Jensen was also a member of the Sacri Romani Imperii Academia Naturae Coriosorum, which he joined in 1964.
Other academic involvements included being a visiting professor at the University of Wisconsin in 1951, in Princeton’s Institute of Advanced Study and the University of California at Berkeley both in 1952, the California Institute of Technology and the Indiana University in 1953, the University of Minnesota in 1956, and he also visited the University of California in La Jolla in 1961.
Jensen was a scientist when Hitler was rising in power, and choosing sides was necessary for people in Germany, especially for those who were able to make scientific contributions for the movement. Membership for the Nationalsozialistischer Deutscher Dozentenbund, (National Socialist German University Lecturers League or NSDDB), was advantageous for those looking to further their career in academics. Although all of the German universities were under the influence of politics, some were not as strict when it came to enforcing the needed membership to the NSDDB, and fortunately this was the case in the University of Hamburg. Jensen was still, however, a member of the NSDDB for three years.
When the Second World War ended, the denazification process began and when it was time for Jensen to face proceedings, he asked Werner Heisenberg for help. Heisenberg was one of the most prominent members of the Uranium Club, and Heisenberg testified in favor of Jensen’s character. This testimony was necessary for the acquisition of his whitewash certificate or Persilschein. Heisenberg had been a powerful man to approach when there is a need for this document, since he was never a member of the National Socialist German Workers Party or the NSDAP. For Jensen, Heisenberg wrote the needed documentation and stated that Jensen did indeed join the party organizations so that he would be able to avoid the difficulties posed by political affiliations or lack thereof for someone in the academia.
Jensen remained a bachelor, and he died on February 11 in 1973 at Heidelberg, Germany.