Instead, he had split the uranium atom into two parts, and his new elements were those parts, barium and krypton. In fact, Fermi had not created any transuranics at all. He had indeed created some new elements that weren’t there before his neutron bombardments, and Fermi and everyone naturally assumed that the uranium atom had absorbed a neutron, spit out an electron, and become element 93. But the fact is, Fermi had been given the Prize primarily for creating elements 93 and 94 by bombardment of uranium with neutrons. In MacMillan’s Nobel lecture, "The Transuranium Elements: Early History", he discretely began his history in 1939 and did not embarrass the Nobel committee by bringing up the 1938 award. Enrico Fermi had been credited with essentially the same discovery when he received the Nobel Prize in Physics in 1938. The Nobel prize citation applauded McMillan for discovering the first transuranic element, but oddly, this was not the first Nobel prize given to someone for discovering the first transuranic. The entire paper, “Radioactive element 94 from deuterons on uranium,” by Edwin McMillan, Glenn Seaborg, and two others, Physical Review, 1946 (paper submitted Jan. McMillan and Abelson published a short paper in Physical Review in 1940 element 93 would later be named neptunium ( third image). So this was a transuranic element, the first produced in the laboratory.
material was an isotope of uranium, U239, and that the 2.3 day residue was the result of beta-decay of U239, where the nucleus emits an electron, increasing the number of protons by one and producing a new element with atomic number 93. Working with a former student turned colleague, Philip Abelson, in the spring of 1940, the two were able to demonstrate using sophisticated chemical separation techniques, that the 23-min. McMillan detected two new radioactive materials in the residues, one with a half-life of 23 minutes and another with a half-life of 2.3 days. As it happened, the new 60-inch cyclotron came online in 1939, providing even more energetic particle bullets ( first and second images). The announcement in 1939 by Otto Hahn and Fritz Strassmann that the uranium atom could be split immediately redirected McMillan’s work at Berkeley, as he subjected uranium to beams of high energy deuterons (nuclei consisting of a proton and a neutron) from the 37-inch cyclotron and examined the fragments. Edwin McMillan at the 60-inch cyclotron at Berkeley, 1939 ()
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