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Bohr told Leon Rosenfeld, who informed Wheeler. [16] Bohr and Wheeler set to work applying the liquid drop model to explain the mechanism of nuclear fission. [23] As the experimental physicists studied fission, they uncovered puzzling results. George Placzek asked Bohr why uranium seemed to fission with both very fast and very slow neutrons.
Bohr and Wheeler overhauled the liquid drop model to explain the mechanism of nuclear fission, with conspicuous success. [118] Their paper appeared in Physical Review on 1 September 1939, the day Germany invaded Poland, starting World War II in Europe. [119] As the experimental physicists studied fission, they uncovered more puzzling results.
George Placzek asked Bohr why uranium seemed to fission with both fast and slow neutrons. Walking to a meeting with Wheeler, Bohr had an insight that the fission at low energies was due to the uranium-235 isotope, while at high energies it was mainly due to the far more abundant uranium-238 isotope. [6]
The 1 September 1939 paper by Bohr and Wheeler used this liquid drop model to quantify fission details, including the energy released, estimated the cross section for neutron-induced fission, and deduced 235 U was the major contributor to that cross section and slow-neutron fission. [42] [5]: 262, 311 [4]: 9–13
John Archibald Wheeler (July 9, 1911 – April 13, 2008) was an American theoretical physicist. He was largely responsible for reviving interest in general relativity in the United States after World War II. Wheeler also worked with Niels Bohr to explain the basic principles of nuclear fission.
The liquid-drop model was first proposed by George Gamow and further developed by Niels Bohr, John Archibald Wheeler and Lise Meitner. [3] It treats the nucleus as a drop of incompressible fluid of very high density, held together by the nuclear force (a residual effect of the strong force ), there is a similarity to the structure of a ...
Bohr and John A. Wheeler set to work applying the liquid drop model developed by Bohr and Fritz Kalckar to explain the mechanism of nuclear fission. [24] George Placzek , who was skeptical about the whole idea of fission, challenged Bohr to explain why uranium seemed to fission with both very fast and very slow neutrons.
The notion of spontaneous fission had been raised by Niels Bohr and John Archibald Wheeler in their 1939 treatment of the mechanism of nuclear fission. [130] The first attempt to discover spontaneous fission in uranium was made by Willard Libby, but he failed to detect it. [131]