Frisch, Otto

Frisch, Otto. 1939. Physical evidence for the division of heavy nuclei under neutron bombardment. Nature 143 276. 

Frisch, Otto R. Meet the Atoms A Popular Guide to Modem Physics. New York A. A. Wyn, 1947. 

Frisch, Otto R., and John A. Wheeler. "The Discovery of Fission. Physics Today 20, no. 11 (November 1967) 43-52. 

In 1938 Niels Bohr had brought the astounding news from Europe that the radiochemists Otto Hahn and Fritz Strassmann in Berlin had conclusively demonstrated that one of the products of the bom-bardmeiit of uranium by neutrons was barium, with atomic number 56, in the middle of the periodic table of elements. He also announced that in Stockholm Lise Meitner and her nephew Otto Frisch had proposed a theory to explain what they called nuclear fission, the splitting of a uranium nucleus under neutron bombardment into two pieces, each with a mass roughly equal to half the mass of the uranium nucleus. The products of Fermi s neutron bombardment of uranium back in Rome had therefore not been transuranic elements, but radioactive isotopes of known elements from the middle of the periodic table. 

Fermi s overall impact on physics is well summarized by the nuclear physicist Otto Frisch (1979,... 

At the end of 1938, Hahn sent her a description of his experiments on the interaction of neutrons with uranium. He and a young chemist. Fritz Strasstnan. had detennined that one of the reaction products was clearly barium. Meitner was so excited about this that she showed Hahn s letter to her nephew, physicist Otto Frisch. Their discussions on the topic gave birth to the idea of nuclear fission. 

After the war, although now famous, Meitner continued her research in Stockholm, interrupted only by trips to receive honorary degrees and other scientific accolades. She shared in the prestigious Enrico Fermi Prize awarded by the U.S. Atomic Energy Committee in 1966. She retired to Cambridge, England, m 1960, to be near her nephew, Otto Frisch, and died there hi 1968 at the age of ninety. Like so many people all over the world during the Hitler period, Meitner s life had been far from easy, but no reasonable person would ever be tempted to call her life empty. 

Nuclear fission is a process in which a heavy nucleus—usually one with a nucleon number of two hundred or more—separates into two nuclei. Usually the division liberates neutrons and electromagnetic radiation and releases a substantial amount of energy. The discoveiyi of nuclear fission is credited to Otto I lahn and Fritz Strassman. In the process of bombarding uranium with neutrons in the late 1930s, they detected several nuclear products of significantly smaller mass than uranium, one of which was identified as Ba. The theorectical underpinnings that exist to this day for nuclear fission were proposed by Lise Meitner and Otto Frisch. Shortly after Hahn and Strassman s discovery. 

Enrico Fermi (Italian-American), Otto Hahn (German), F. Strassman, Lise Meitner (Austrian), and Otto Frisch (Austrian) discover and describe nuclear fission. 

Shortly after the results of the Stern-Gerlach experiment appeared in the scientific literature. Stern received an invitation to join the faculty at the University of Hamburg, where, over the period 1922 to 1933, he continued his experimental work. In 1932, Stern decided to adapt the molecular beam method to a daunting experiment to measure the magnetic moment of the proton, the nucleus of the hydrogen atom. Joining him is this endeavor was Otto Robert Frisch. 

Hahn and Strassmann reported on their finding to Meitner. In discussion with Otto Frisch (1904-), her nephew and a physicist, Meitner recognized that the neutron bombardment had split the uranium nucleus. She called this process fission, and, in January 1939 with Frisch, she sent a letter to the journal Nature announcing the discovery of nuclear fission. 

In the late 1930s, the Austrian physicist Lise Meitner and her nephew Otto Frisch proposed that the uranium-235 nucleus could be split into smaller nuclei, a process that they called fission because of its similarity to the fission a biological cell undergoes during reproduction. 

On December 19, 1938, Hahn sent Meitner a letter describing how one of the new elements had chemical properties strongly resembling those of barium and asking if she could provide an explanation. The physicist Otto Frisch visited Meitner, his aunt, for Christmas to help dispel her loneliness. While there, the two went for the now famous walk in the snow. During an extended conversation in the woods, they came to realize that if the nucleus was considered a liquid drop, the impact of a subatomic particle could... 

In Germany in 1938, Otto Hahn and Fritz Strassmann, skeptical of claims by Enrico Fermi and Irene Johot-Curie that bombardment of uranium by neutrons produced new so-called transuranic elements (elements beyond uranium), repeated these experiments and chemically isolated a radioactive isotope of barium. Unable to interpret these findings, Hahn asked Lise Meitner, a physicist and former colleague, to propose an explanation for his observations. Meitner and her nephew, Otto Frisch, showed that it was possible for the uranium nucleus to be spfit into two smaller nuclei by the neutrons, a process that they termed fission. The discovery of nuclear fission eventually led to the development of nuclear weapons and, after World War II, the advent of nuclear power to generate electricity. Nuclear chemists were involved in the chemical purification of plutonium obtained from uranium targets that had been irradiated in reactors. They also developed chemical separation techniques to isolate radioactive isotopes for industrial and medical uses from the fission products wastes associated with plutonium production for weapons. Today, many of these same chemical separation techniques are being used by nuclear chemists to clean up radioactive wastes resulting from the fifty-year production of nuclear weapons and to treat wastes derived from the production of nuclear power. 

After the discovery of uranium radioactivity by Henri Becquerel in 1896, uranium ores were used primarily as a source of radioactive decay products such as Ra. With the discovery of nuclear fission by Otto Hahn and Fritz Strassman in 1938, uranium became extremely important as a source of nuclear energy. Hahn and Strassman made the experimental discovery Lise Meitner and Otto Frisch provided the theoretical explanation. Enrichment of the spontaneous fissioning isotope U in uranium targets led to the development of the atomic bomb, and subsequently to the production of nuclear-generated electrical power. There are considerable amounts of uranium in nuclear waste throughout the world, see also Actinium Berkelium Einsteinium Fermium Lawrencium Mendelevium Neptunium Nobelium Plutonium Protactinium Rutherfordium Thorium. 

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