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radioactive series

radioactive series

Any of four sets of unstable heavy atomic nuclei that undergo a series of alpha decay and beta decay until a stable nucleus is achieved. The natural series are the thorium series, the uranium series, and the actinium series. These are headed by naturally occurring species of unstable nuclei that have half-lives comparable to the age of the earth. The fourth set, the neptunium series, is headed by neptunium-237, which has a half-life of 2 million years. Its members do not occur naturally but are artificially produced by nuclear reactions and have short half-lives.

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John Ray Dunning (September 24, 1907 in Shelby, Nebraska - August 25, 1975 in Key Biscayne, Florida) was an American physicist who played key roles in the development of the atomic bomb. He specialized in neutron physics and did pioneering work in gaseous diffusion for isotope separation. He was Dean of the School of Engineering and Applied Science at Columbia University from 1950 to 1969.

Education

After graduation from Shelby High School in 1925, Dunning entered Nebraska Wesleyan University and received his B. A. degree in 1929 with highest honors. After graduation, he began a doctoral program at Columbia University. In 1932, James Chadwick discovered the neutron, which influenced Dunning’s career, as he thereafter devoted much of his professional interest to the characteristics and uses of the particle. Dunning’s research was enthusiastically supported at Columbia by George B. Pegram. In 1933, Dunning was an instructor at the University, and he received his Ph.D. in 1934.

Career

After gaining his doctorate at Columbia, Dunning continued teaching and research there. He became assistant professor in 1935, associate professor in 1938, Thayer Lindsley Professor of Applied Science in 1946, and Dean of the School of Engineering and Applied Science in 1950. Appointment to the position of dean ended his active career in research at Columbia. By the time he stepped down as Dean in 1969, he had raised $50 million for the School.

After his promotion in 1935, Dunning became the central figure at Columbia on neutron research, and his activities complemented those of Enrico Fermi in Italy. Fermi and many of his colleagues came to Columbia to work with Dunning and his associates. In 1936, Dunning received a Traveling Fellowship, which he used to meet and discuss his neutron physics research with many eminent European nuclear physicists including Niels Bohr, James Chadwick, Fermi, Werner Heisenberg, and Ernest Rutherford.

Dunning closely followed the work of Ernest Lawrence on the cyclotron. Dunning wanted a more powerful neutron source and the cyclotron appeared as an attractive tool to achieve this end. During 1935 and 1936, he was able construct a cyclotron using many salvaged parts to reduce costs and funding from industrial and private donations.

In December 1938, the German chemists Otto Hahn and Fritz Strassmann sent a manuscript to Naturwissenschaften reporting they had detected the element barium after bombarding uranium with neutrons; simultaneously, they communicated these results to Lise Meitner. Meitner, and her nephew Otto Robert Frisch, correctly interpreted these results as being nuclear fission. Frisch confirmed this experimentally on 13 January 1939. In 1944, Hahn received the Nobel Prize for Chemistry for the discovery of nuclear fission. Some historians have documented the history of the discovery of nuclear fission and believe Meitner should have been awarded the Nobel Prize with Hahn.

Even before it was published, Meitner’s and Frisch’s interpretation of the work of Hahn and Strassmann crossed the Atlantic Ocean with Niels Bohr, who was to lecture at Princeton University. Isidor Isaac Rabi and Willis Lamb, two Columbia University physicists working at Princeton, heard the news and carried it back to Columbia. Rabi said he told Fermi; Fermi gave credit to Lamb. It was soon clear to a number of scientists at Columbia that they should try to detect the energy released in the nuclear fission of uranium from neutron bombardment. On 25 January 1939, Dunning was a member of the experimental team at Columbia University which conducted the first nuclear fission experiment in the United States, which was conducted in the basement of Pupin Hall; the other members of the team were Herbert L. Anderson, Eugene T. Booth, Enrico Fermi, G. Norris Glasoe, and Francis G. Slack.

During the Manhattan Project, Dunning conducted pioneering work at Columbia University on gaseous diffusion to separate uranium isotopes; others working on the project included Booth, Henry A. Boorse, Willard F. Libby, Alfred O. C. Nier, and Francis G. Slack. Due to the secrecy of this work, Dunning and three of his colleagues were awarded $300,000 each in lieu of patent royalties.

Personal

Dunning married Esther Laura Blevins in 1930. They had two children, John Ray, Jr. and Ann. Their son became a Professor of Physics and Astronomy at Sonoma State University.

Honors and positions

Dunning received honors for his work and participated in national scientific leadership organizations.

Selected Literature

  • John R. Dunning The Emission and Scattering of Neutrons, Phys. Rev. Volume 45, Issue 9, 586 - 600 (1934). Institutional citation: Department of Physics, Columbia University. Received 5 March 1934.
  • H. L. Anderson, E. T. Booth, J. R. Dunning, E. Fermi, G. N. Glasoe, and F. G. Slack The Fission of Uranium, Phys. Rev. Volume 55, Number 5, 511 - 512 (1939). Institutional citation: Pupin Physics Laboratories, Columbia University, New York, New York. Received 16 February 1939.
  • E. T. Booth, J. R. Dunning, and F. G. Slack Delayed Neutron Emission from Uranium, Phys. Rev. Volume 55, Number 9, 876 - 876 (1939). Institutional citation: Department of Physics, Columbia University, New York, New York. Received 17 April 1939.
  • E. T. Booth, J. R. Dunning, and F. G. Slack Energy Distribution of Uranium Fission Fragments, Phys. Rev. Volume 55, Number 10, 981 - 981 (1939). Institutional citation: Pupin Physics Laboratories, Columbia University, New York, New York. Received 1 May 1939.
  • E. T. Booth, J. R. Dunning, and G. N. Glasoe Range Distribution of the Uranium Fission Fragments, Phys. Rev. Volume 55, Issue 10, 982 - 982 (1939). Institutional citation: Pupin Physics Laboratories, Columbia University, New York, New York. Received 1 May 1939.
  • A. O. Nier, E. T. Booth, J. R. Dunning, and A. V. Grosse Nuclear fission of separated uranium isotopes, Phys. Rev. Volume 57, Issue 6, 546-546 (1940). Received 3 March 1940. Booth, Dunning, and Grosse were identified as being at Columbia University, New York, New York. Nier was identified as being at the University of Minnesota, Minneapolis, Minnesota.
  • A. O. Nier, E. T. Booth, J. R. Dunning, and A. V. Grosse Further experiments on fission of separated uranium isotopes, Phys. Rev. Volume 57, Issue 8, 748-748 (1940). Received 13 April 1940. Booth, Dunning, and Grosse were identified as being at Columbia University, New York, New York. Nier was identified as being at the University of Minnesota, Minneapolis, Minnesota.
  • E. T. Booth, J. R. Dunning, A. V. Grosse, and A. O. Nier Neutron Capture by Uranium (238), Phys. Rev. Volume 58, Issue 5, 475 - 476 (1940). Received 13 August 1940. Booth, Dunning, and Grosse were identified as being at Columbia University, New York, New York. Nier was identified as being at the University of Minnesota, Minneapolis, Minnesota.
  • A. V. Grosse, E. T. Booth, and J. R. Dunning The Fourth (4n+1) Radioactive Series, Phys. Rev. Volume 59, Issue 3, 322 - 323 (1941). Institutional citation: Pupin Physics Laboratories, Columbia University, New York, New York. Received 11 January 1941.

Books

  • John R. Dunning Matter, Energy and Radiation (Columbia College Natural Science Series) (McGraw Hill, 1941)
  • John R. Dunning and Bruce R. Prentics (editors) Hot Laboratory Operation and Equipment, Volume III. Fifth Hot Laboratories and Equipment Conference (Symposium Publications Division Pergamon Press, 1957)
  • John R. Dunning and Bruce R. Prentics (editors) Advances in Nuclear Engineering, Volume I. Proceedings of the Second Nuclear Engineering and Science Conference (Pergamon Press 1957)
  • John R. Dunning and Bruce R. Prentics (editors) Advances in Nuclear Engineering, Volume II. Proceedings of the Second Nuclear Engineering & Science Congress (Pergamon Press 1957)

Bibliography

External links

Notes

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