J. Hans D. Jensen

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J. Hans D. Jensen
Johannes Hans Daniel Jensen (1907-1973).jpg
BornJohannes Hans Daniel Jensen
(1907-06-25)25 June 1907
Hamburg, German Empire
Died11 February 1973(1973-02-11) (aged 65)
Heidelberg, West Germany
Nationality German
Alma mater University of Hamburg
Awards Nobel Prize for Physics (1963)
Scientific career
Fields Physics
Doctoral advisor Wilhelm Lenz
Doctoral students Hans-Arwed Weidenmüller

Johannes Hans Daniel Jensen (25 June 1907 – 11 February 1973) was a German nuclear physicist. During World War II, he worked on the German nuclear energy project, known as the Uranium Club, in which he made contributions to the separation of uranium isotopes. After the war Jensen was a professor at the University of Heidelberg. He was a visiting professor at the University of Wisconsin–Madison, the Institute for Advanced Study, University of California, Berkeley, Indiana University, and the California Institute of Technology. [1]

World War II 1939–1945 global war

World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries. The major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China. It included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, and the only use of nuclear weapons in war.

Uranium Chemical element with atomic number 92

Uranium is a chemical element with symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weakly radioactive because all isotopes of uranium are unstable, with half-lives varying between 159,200 years and 4.5 billion years. The most common isotopes in natural uranium are uranium-238 and uranium-235. Uranium has the highest atomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead, and slightly lower than that of gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite.

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Contents

Jensen shared half of the 1963 Nobel Prize for Physics with Maria Goeppert-Mayer for their proposal of the nuclear shell model.

Nuclear shell model model of the atomic nucleus

In nuclear physics and nuclear chemistry, the nuclear shell model is a model of the atomic nucleus which uses the Pauli exclusion principle to describe the structure of the nucleus in terms of energy levels. The first shell model was proposed by Dmitry Ivanenko in 1932. The model was developed in 1949 following independent work by several physicists, most notably Eugene Paul Wigner, Maria Goeppert Mayer and J. Hans D. Jensen, who shared the 1963 Nobel Prize in Physics for their contributions.

Education

Jensen studied physics, mathematics, physical chemistry, and philosophy at the Albert-Ludwigs-Universität Freiburg and the University of Hamburg from 1926 to 1931, and he received his doctorate at the latter in 1932 under Wilhelm Lenz. Jensen completed his Habilitation in 1936 at the University of Hamburg. [1] [2]

University of Freiburg Public research university in Freiburg, Germany

The University of Freiburg, officially the Albert Ludwig University of Freiburg, is a public research university located in Freiburg im Breisgau, Baden-Württemberg, Germany. The university was founded in 1457 by the Habsburg dynasty as the second university in Austrian-Habsburg territory after the University of Vienna. Today, Freiburg is the fifth-oldest university in Germany, with a long tradition of teaching the humanities, social sciences and natural sciences. The university is made up of 11 faculties and attracts students from across Germany as well as from over 120 other countries. Foreign students constitute about 16% of total student numbers.

University of Hamburg university in Hamburg, Germany

The University of Hamburg is a comprehensive university in Hamburg, Germany. It was founded on 28 March 1919, having grown out of the previous General lecture system and the Colonial Institute of Hamburg as well as the Akademic Gymnasium. In spite of its relatively short history, six Nobel Prize Winners and serials of scholars are affiliated to the university. The University of Hamburg is the biggest research and education institution in Northern Germany and one of the most extensive universities in Germany. The main campus is located in the central district of Rotherbaum, with affiliated institutes and research centres spread around the city state.

Wilhelm Lenz was a German physicist, most notable for his invention of the Ising model and for his application of the Laplace–Runge–Lenz vector to the old quantum mechanical treatment of hydrogen-like atoms.

Career

In 1937 Jensen was Privatdozent (unpaid lecturer) at the University of Hamburg and began working with Paul Harteck, director of the university's physical chemistry department and advisor to the Heereswaffenamt (HWA, Army Ordnance Office) on explosives. Harteck and his teaching assistant Wilhelm Groth made contact with the Reichskriegsministerium (RKM, Reich Ministry of War) on 24 April 1939 to tell them of potential military applications of nuclear chain reactions. Military control of the German nuclear energy project, also known as the Uranverein (Uranium Club), began on 1 September 1939, the day that Nazi Germany initiated World War II by invading Poland. Harteck, one of the principals in the Uranverein, brought Jensen into the project. Jensen's main thrust was on double centrifuges for separation of uranium isotopes (see the section below citing internal reports of the Uranverein). Harteck and Jensen developed a double centrifuge based on a rocking process (Schaukelverfahren) to facilitate the separation effect. [1] [3] [4]

Privatdozent or Privatdozentin, abbreviated PD, P.D. or Priv.-Doz., is an academic title similar to Adjunct professor in North America conferred at some European universities, especially in German-speaking countries, to someone who holds certain formal qualifications that denote an ability to teach a designated subject at university level. In its current usage, the title indicates that the holder has permission to teach and examine independently without having a chair. The title is not necessarily connected to a salaried position, but may entail a nominal obligation to teach.

Paul Harteck German chemist

Paul Karl Maria Harteck was a German physical chemist. In 1945 under Operation Epsilon in "the big sweep" throughout Germany, Harteck was arrested by the allied British and American Armed Forces for suspicion of aiding the Nazis in their nuclear weapons program and he was incarcerated at Farm Hall, an English house fitted with covert electronic listening devices, for six months.

Wilhelm Groth German chemist

Wilhelm Groth was a German physical chemist. During World War II, he worked on the German nuclear energy project, also known as the Uranium Club; his main activity was the development of centrifuges for the enrichment of uranium. After the war, he was a professor of physical chemistry at the University of Hamburg. In 1950, he became director of the Institute of Physical Chemistry at the University of Bonn. He was a principal in the 1956 shipment of three centrifuges for uranium enrichment to Brazil.

In 1941 Jensen was named extraordinarius professor of theoretical physics at the Technische Hochschule Hannover (today, the University of Hanover), and in 1946 he became an ordinarius professor there. In 1949 he was appointed ordinarius professor at the Ruprecht Karl University of Heidelberg; since 1969 he was emeritus praecox. He was a guest professor at the University of Wisconsin–Madison (1951), the Institute for Advanced Study (1952), University of California, Berkeley (1952), Indiana University (1953), California Institute of Technology (1953), University of Minnesota, Twin Cities (1956), and University of California, San Diego (1961). [1] [2]

University of Hanover public university located in Hannover, Germany

The University of Hanover, officially the Gottfried Wilhelm Leibniz Universität Hannover, short Leibniz University Hannover, is a public university located in Hannover, Germany. Founded on May 2, 1831, it is one of the largest and oldest science and technology universities in Germany. In the 2014/15 school year it enrolled 25,688 students, of which 2,121 were from foreign countries. It has nine faculties which offer 190 full and part degree programs in 38 fields of study. The University is named after Gottfried Wilhelm Leibniz, the 18th century mathematician and philosopher.

Institute for Advanced Study postgraduate center in Princeton, New Jersey

The Institute for Advanced Study (IAS) located 1 Einstein Drive, Princeton, New Jersey, in the United States, is an independent, postdoctoral research center for theoretical research and intellectual inquiry founded in 1930 by American educator Abraham Flexner, together with philanthropists Louis Bamberger and Caroline Bamberger Fuld.

University of California, Berkeley Public university in California, USA

The University of California, Berkeley is a public research university in Berkeley, California. It was founded in 1868 and serves as the flagship institution of the ten research universities affiliated with the University of California system. Berkeley has since grown to instruct over 40,000 students in approximately 350 undergraduate and graduate degree programs covering numerous disciplines.

In 1963 Jensen shared half of the Nobel Prize in Physics with Maria Goeppert-Mayer for their proposal of the nuclear shell model; the remaining half of the prize was awarded to Eugene Wigner for unrelated work in nuclear and particle physics, especially through the application of fundamental symmetry principles.

Nobel Prize in Physics One of the five Nobel Prizes established in 1895 by Alfred Nobel

The Nobel Prize in Physics is a yearly award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions for humankind in the field of physics. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the others being the Nobel Prize in Chemistry, Nobel Prize in Literature, Nobel Peace Prize, and Nobel Prize in Physiology or Medicine.

Eugene Wigner mathematician and Nobel Prize-winning physicist

Eugene Paul "E. P." Wigner was a Hungarian-American theoretical physicist, engineer and mathematician. He received the Nobel Prize in Physics in 1963 "for his contributions to the theory of the atomic nucleus and the elementary particles, particularly through the discovery and application of fundamental symmetry principles".

Party memberships

Adolf Hitler took power on 30 January 1933. On 7 April of that year the Law for the Restoration of the Professional Civil Service was enacted; this law, and its subsequent related ordinances, politicized the education system in Germany. Other factors enforcing the politicization of education were Nationalsozialistische Deutsche Arbeiterpartei (NSDAP, National Socialist German Workers Party) organizations in academia and the rise of the Deutsche Physik movement, which was anti-Semitic and had a bias against theoretical physics, especially including quantum mechanics. The Party organizations were the Nationalsozialistischer Deutscher Studentenbund (NSDStB, National Socialist German Student League) founded in 1926, the Nationalsozialistischer Lehrerbund (NSLB, National Socialist Teachers League) founded in 1927, and the Nationalsozialistischer Deutscher Dozentenbund (NSDDB, National Socialist German University Lecturers League) founded in 1933. While membership in the NSDDB was not mandatory, it was tactically advantageous, if not unavoidable, as the district leaders had a decisive role in the acceptance of an Habilitationsschrift , which was a prerequisite to attaining the rank of Privatdozent necessary to becoming a university lecturer. [5] [6] [7] [8]

While all German universities were politicized, not all were as strict in carrying out this end as was the University of Hamburg, where Jensen received his doctorate and Habilitationsschrift. Upon his 1936 habilitation he had been a member of NSDDB for three years, the NSLB for two years, and a candidate for membership in NSDAP, which he received the next year. The university leader of NSLB had made it clear that active participation was expected from Jensen, and that is what they got. [9] [10]

After World War II the denazification process began. When Jensen faced the proceedings, he turned to Werner Heisenberg, a prominent member of the Uranverein, for a testament to his character – a document known as a Persilschein (whitewash certificate). [11] Heisenberg was a particularly powerful writer of these documents, as he had never been a member of NSDAP, he had publicly clashed with NSDAP and the Schutzstaffel (SS), and he had been appointed by the British occupation authorities to the chair for theoretical physics and the directorship of the Max-Planck Institut für Physik then in Göttingen. Heisenberg wrote the document and convinced the authorities that Jensen had only joined the Party organizations to avoid unnecessary difficulties in academia. [12]

Honors

Honors conferred upon Jensen include: [1] [2]

Internal reports

The following reports were published in Kernphysikalische Forschungsberichte (Research Reports in Nuclear Physics), an internal publication of the German Uranverein . The reports were classified Top Secret, they had very limited distribution, and the authors were not allowed to keep copies. The reports were confiscated under the Allied Operation Alsos and sent to the United States Atomic Energy Commission for evaluation. In 1971 the reports were declassified and returned to Germany. The reports are available at the Karlsruhe Nuclear Research Center and the American Institute of Physics. [13] [14]

Bibliography

Books

Articles

Notes

  1. 1 2 3 4 5 Johannes Jensen – Nobel Prize Biography (1963)
  2. 1 2 3 Hentschel and Hentschel, 1996, 363-364 and Appendix F; see the entry for Johannes Jensen
  3. Hentschel and Hentschel, 1996, 363-364 and Appendix F; see the entries for Harteck and Johannes Jensen.
  4. Walker, 1993, pp. 121-122
  5. Walker, 1993, pp. 192-204. In these pages, Mark Walker puts into perspective the motivations of and the pressures on students and scientists in the early years of National Socialism in Germany. He addresses the general situation, the Uranverein scientists as a group, and particular cases, e.g., Johannes Jensen, Wilhelm Groth, Karl Wirtz, and Wolfgang Gentner.
  6. Hentschel, 1996, Appendix C; see entries for NSDDB, NSDStB, and the NSLB.
  7. Hoffmann, Dieter Between Autonomy and Accommodation: The German Physical Society during the Third Reich, Physics in Perspective 7(3) pp. 293-329 (2005)
  8. Beyerchen, 1977, pp. 123–167
  9. Walker, 1993, pp. 195-196
  10. Hentschel and Hentschel, 1996, Appendix F; see the entry for Johannes Jensen.
  11. Persilschein a play on words using the name of the German detergent Persil
  12. Walker, 1993, pp. 192-204
  13. Hentschel and Hentschel, 1996, Appendix E; see the entry for Kernphysikalische Forschungsberichte
  14. Walker, 1993, pp. 268-274

Sources

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