Strassman, Fritz

Saussure, Nicholas Theodore de, 1 Scheele, Carl Wilhelm, 2-3 Scheuch, Heinrich, 228 Schilbach (Bosch), Else, 86 Schiller, Georg, 113 Schloesing, Theophile, 16 Schmitz, Hermann, 104 Schonherr, Otto, 75-76 Schwann, Theodor, 2 Stern, Georg, 94-95 Strassman, Fritz, 231 Stresemann, Gustav, 224 Suess, Hans, 178... 

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. 

The first scientific attempts to prepare the elements beyond uranium were performed by Enrico Fermi, Emilio Segre, and co-workers in Rome in 1934, shortly after the existence of the neutron was discovered. This group of investigators irradiated uranium with slow neutrons and found several radioactive products, which were thought to be due to new elements. However, detailed chemical studies by Otto Hahn and Fritz Strassman in Berlin showed these species were isotopes of the known elements created by the fission of uranium into two approximately equal parts (see Chap. 11). This discovery of nuclear fission in December of 1938 was thus a by-product of man s quest for the transuranium elements. 

In 1938, Otto Hahn and Fritz Strassman of Germany proved that the bombardment of uranium nuclei with neutrons produces several lighter and stable nuclei, each having about equal sizes. The produced nuclei are the radioisotopes of the lighter elements such as barium (Ba) and cerium (Ce). Thus, the foundations of a new useful method for the production of huge amount of energy were established. 

This was initiated by the first description of the atom structure in 1913 by Ernest Rutherford, a British scientist and Niels Bohr, a Danish scientist. Then came the discovery of the neutron in 1932 by James Chadwick (a British student of Rutherford), the discovery of artificial radioactivity by Irene and Frederic Joliot Curie (Nobel Prize in chemistry in 1935) and finally the discovery of fission in 1938 by Lise Meitner, Otto Hahn and Fritz Strassman (German scientists) which brought Hahn the Nobel Prize for physics in 1944. 

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. 

A vast amount of energy is released when heavy atomic nuclei split—the nuclear fission process—and when small atomic nuclei combine to make heavier nuclei—the fusion process. In 1938, Otto Hahn, Fritz Strassman, Lise Meitner, and Otto Frisch discovered that ggU is fissionable by neutrons (Figure 13.8). In less than a decade, this discovery led to two important applications of this energy release accompanying fission—the atomic bomb and nuclear power plants. 

In 1939 the German scientists Otto Hahn (1879-1968), Lise Meitner (1878-1968) and Fritz Strassman (1902-1980) found that nuclear fission is possible. It was demonstrated in a paper in Die Naturwissenschaften in 1939. Lise Meitner, being both a woman and a Jew, did not have her name on the important paper. She had fled Berlin in July 1938 to escape Nazi persecution. However, in another paper in 1939, in Nature, together with Otto Frisch (1904-1979), she described the disintegration of uranium by neutrons and explained the theory of uranium fission. 

Fermi s experiments caught the attention of a physicist in Berlin, Lise Meitner. Knowing that she could not perform the difficult task of chemically separating radionuclides either, Meitner persuaded a colleague, radiochemist Otto Hahn, to help her explain Fermi s results. Joined by expert chemical analyst Fritz Strassman, Meitner s team began investigating neutron-induced uranium decay at the end of 1934. 

Among the products of the neutron bombardment of uranium, a radioactive element was found that behaved chemically like the elements of Group 2R of the periodic system (strontium, barium, and radium). Among these, only radium had been known to be radioactive, and therefore the new radioactive element was assumed to be radium. However, because its radioactivity differed from that of natural radium, it was thought to be some other isotope of radium, In 1939, Otto Hahn and Fritz Strassman attempted to isolate this "radium by the same chemical methods used in the original discovery of radium by the... 

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