[FERMI, Enrico (1901-1954), and others.] Method for Increasing the Efficiency of Nuclear Reactions and Products thereof (caption title). Patent number 465,045. [London: His Majesty's Stationery Office,] 1937.

Very rare original patent specification for the production of artificial radioactivity through slow neutron bombardment. This is the first of the documents listed under the Printing and the Mind of Man entry for the Atom Bomb (PMM 422). Before the outbreak of World War Two, information about nuclear reactions and radioactivity was openly published internationally. Its application to weaponry was not part of the 1930s discourse. On the contrary, "the only practical use suggested for it was "implied in the Fermi patent for producing radioactive isotopes, which has been a continued blessing to medical and physiological research." However, Fermi's process "also isolated as by-products two new elements, heavier than uranium, which by analogy were called 'neptunium' and 'plutonium.' The latter was later found to be fissionable” (PMM).

The patent was submitted on October 25, 1935, based on discoveries made in Italy the year before. The patent was accepted on April 26, 1937, and assigned to G.M. Giannini & Co on behalf of Fermi and his colleagues. A U.S. patent was also applied for at the same time in the United States. Fermi’s work led directly to the 1938 experiments of Hahn and Strassman in Berlin, which in turn led Lise Meitner, who had fled to Copenhagen, to realize that the phenomena they observed were the result of nuclear fission (PMM 422b). Fermi's work, culminating with the present patent, "made him the perhaps the world's leading expert on the subject during the thirties" (Pais). See lots 36, 37, and 38 for Meitner and Frisch's works based on Fermi's discoveries. PMM 422a.

Single folio sheet (280 x 190mm). Printed recto and verso. Inkstamp: "27.Mai 1937."