MEITNER, Lise (1878–1968). "Über die b- und g-Strahlen der Transurane." Offprint from: Annalen der Physik. 5th series, vol. 29. Leipzig, 1937. [With:] MEITNER, Lise (1878–1968), HAHN, Otto (1879–1968) and STRASSMANN, Fritz (1902–1980). "Über die Umwandlungsreihen des Urans, die durch Neutronenbestrahlung erzeugt werden." Offprint from: Zeitschrift für Physik 106. Berlin, 1937.

First editions, rare offprint issues, of two crucial papers leading to Lise Meitner and Otto Frisch’s discovery of nuclear fission. The first Meitner paper is on the radiation of the so-called "transuranic" elements, i.e. those with atomic numbers of 93 or higher, obtained by bombarding uranium with neutrons. While Enrico Fermi, and Meitner’s two colleagues the physical chemists Otto Hahn and Fritz Strassmann were certain from their experiments that they had detected evidence of transuranic elements, Meitner was not convinced, as the results could not be plausibly explained by nuclear physics. In the first paper, she demonstrated with cloud chamber experiments that the transuranics emitted beta rays only. In the second paper, published in May 1937 and co-authored with Hahn and Strassmann, their differing interpretations are apparent. Meitner, the lead author of the Zeitschrift paper, concluded that "the process must be neutron capture by uranium-238, which leads to three isomeric nuclei of uranium-239. This result is very difficult to reconcile with current concepts of the nucleus." Simultaneously, an almost identical version of the paper was published in the Chemische Berichte, with Hahn as the lead author. He presented a different conclusion, concluding that "Above all, their chemical distinction from all previously known elements needs no further discussion" (translated).

"Hahn presented what appeared to be ironclad chemical evidence for the existence of transuranes. In contrast, Meitner’s work demonstrated that the uranium problem had become much larger, more difficult, and more significant than the discovery of new elements alone ... As the physicist on the Berlin team, Meitner’s task was to incorporate the data from chemistry, radioactivity, and her own physical experiments into a coherent explanation of the nuclear processes. Her report in Zeitschrift für Physik clearly shows how difficult that was" (Sime, Lise Meitner: A Life in Physics, pp 173-174).

A year after these two papers were published, Meitner had to flee Nazi Germany, escaping first to the Netherlands and then immediately flying to Stockholm. Following further evidence of "transuranic" elements announced by Fermi, and Irene Curie’s own investigations, Hahn and Strassmann attempted to verify these experiments. Hahn travelled to Copenhagen where he met with Meitner and Bohr. Meitner instructed Hahn and Strassmann to redo their experiments. When she received the results, proving that barium was produced in the bombardment of uranium with neutrons, and which Hahn had described as the atom "bursting," Meitner and Frisch knew that a new atomic phenomenon had been discovered. Using the Gamow/Bohr "liquid drop" model of the nucleus, and Einstein’s e = mc2 formula, Meitner concluded that nuclear fission was the only possible explanation.

Two volumes, octavo. The first title illustrated from cloud chamber photographs. Original printed self-wrappers (mild toning). Provenance: "Kern" (for "nucleus") in pencil on both front pages.