Walther Wilhelm Georg Bothe (; 8 January 1891 – 8 February 1957) was a German experimental physicist who shared the 1954 Nobel Prize in Physics with Max Born "for the coincidence method and his discoveries made therewith."
Bothe served in the military during World War I from 1914, and he was a prisoner of war of the Russians, returning to Germany in 1920. Upon his return to the laboratory, he developed and applied coincidence circuits to the study of nuclear reactions, such as the Compton effect, cosmic rays, and the wave–particle duality of radiation.
In 1930, Bothe became Full Professor and Director of the Physics Department at the University of Giessen. In 1932, he became Director of the Physical and Radiological Institute at Heidelberg University; he was driven out of this position by elements of the movement. To preclude his emigration from Germany, he was appointed Director of the Physics Institute of the Kaiser Wilhelm Institute for Medical Research at Heidelberg University. There, he built the first operational cyclotron in Germany. Furthermore, he became a principal in the German nuclear energy project, also known as , which was started in 1939 under the supervision of the Army Ordnance Office.
In 1946, in addition to his directorship of the Physics Institute at the KWImf, Bothe was reinstated as a professor at Heidelberg University. From 1956 to 1957, he was a member of the Nuclear Physics Working Group in Germany.
In the year after Bothe's death, his Physics Institute at the KWImF was elevated to the status of a new institute under the Max Planck Society and it then became the Max Planck Institute for Nuclear Physics. Its main building was later named Bothe laboratory.
Education Walther Wilhelm Georg Bothe was born on 8 January 1891 in Oranienburg, Germany. From 1908 to 1912, Bothe studied physics under Max Planck at the Friedrich Wilhelm University of Berlin, receiving his Ph.D. in 1914.Hentschel, Appendix F; see the entry for Bothe.Mehra, Jagdish, and Helmut Rechenberg (2001) The Historical Development of Quantum Theory. Volume 1 Part 2 The Quantum Theory of Planck, Einstein, Bohr and Sommerfeld 1900–1925: Its Foundation and the Rise of Its Difficulties. Springer, . p. 608
Career and research Early years In 1913, Bothe joined the Physikalisch-Technische Reichsanstalt (PTR – now the Physikalisch-Technische Bundesanstalt), where he stayed until 1930. Hans Geiger had been appointed Director of the newly-established Laboratory for Radioactivity there in 1912; Bothe was an assistant to Geiger from 1913 to 1920, a scientific member of Geiger's staff from 1920 to 1927, and Director of the Laboratory for Radioactivity from 1927 to 1930—in succession to Geiger.Walther Bothe and the Physics Institute: the Early Years of Nuclear Physics, Nobelprize.org.Bothe, Walther (1954) The Coincidence Method, The Nobel Prize in Physics 1954, Nobelprize.org.
In May 1914, Bothe volunteered for service in the German cavalry. He was taken prisoner by the Russians and incarcerated in Russia for five years. While there, he learned the Russian language and worked on theoretical physics problems related to his doctoral studies. He returned to Germany in 1920, with a Russian bride.
On his return from Russia, Bothe continued his employment at the PTR under Hans Geiger in the Laboratory for Radioactivity. In 1924, Bothe published on his coincidence method. The Bothe–Geiger coincidence experiment studied the Compton effect and the wave–particle duality of light. Bothe's coincidence method and his applications of it earned him the Nobel Prize in Physics in 1954.Hentschel, Appendix F; see the entry for Geiger.Fick, Dieter and Kant, Horst Walther Bothe's contributions to the understanding of the wave-particle duality of light.Walther Bothe Biography, The Nobel Prize in Physics 1954, Nobelprize.org.
In 1925, while still at the PTR, Bothe became a (unsalaried lecturer) at the Friedrich Wilhelm University of Berlin, and, in 1929, he became an (extraordinary professor) there.
In 1927, Bothe began the study of the transmutation of light elements through bombardment with alpha particles. From a joint investigation with H. Fränz and Heinz Pose in 1928, Bothe and Fränz correlated reaction products of nuclear interactions to nuclear energy levels.
In 1929, in collaboration with Werner Kolhörster and Bruno Rossi (who were guests in Bothe's laboratory at the PTR), Bothe began the study of cosmic rays.Bonolis, Luisa Walther Bothe and Bruno Rossi: The birth and development of coincidence methods in cosmic-ray physics The study of cosmic radiation would be conducted by Bothe for the rest of his life.
In 1930, Bothe became an (ordinary professor) and Director of the Physics Department at the University of Giessen. The same year, Bothe and his collaborator Herbert Becker bombarded beryllium, boron, and lithium with alpha particles from polonium and observed a new form of penetrating radiation. In 1932, James Chadwick identified this radiation as the neutron.
Heidelberg In 1932, Bothe succeeded Philipp Lenard as Director of the Physical and Radiological Institute at Heidelberg University. It was then that Rudolf Fleischmann became a teaching assistant to Bothe. When Adolf Hitler became Chancellor of Germany on 30 January 1933, the concept of (Aryan Physics) took on more favor as well as fervor; it was antisemitic and against theoretical physics, especially against modern physics, including quantum mechanics and both atomic and nuclear physics. As applied in the university environment, political factors took priority over the historically applied concept of scholarly ability,Beyerchen, pp. 141–167. even though its two most prominent supporters were the LenardBeyerchen, pp. 79–102. and Johannes Stark.Beyerchen, pp. 103–140. Supporters of Deutsche Physik launched vicious attacks against leading theoretical physicists. While Lenard was retired from Heidelberg, he still had significant influence there.
In 1934, Lenard had managed to get Bothe relieved of his directorship of the Physical and Radiological Institute, whereupon Bothe was able to become the Director of the Institute for Physics of the Kaiser-Wilhelm-Institut für medizinische Forschung (KWImF – Kaiser Wilhelm Institute for Medical Research) in Heidelberg, replacing Karl W. Hauser, who had recently died. Ludolf von Krehl, Director of the KWImF, and Max Planck, President of the Kaiser-Wilhelm-Gesellschaft (KWG – Kaiser Wilhelm Society), had offered the directorship to Bothe to ward off the possibility of his emigration. Bothe held the directorship of the Institute for Physics at the KWImF until his death in 1957. While at the KWImF, Bothe held an honorary professorship at Heidelberg, which he held until 1946. Fleischmann went with Bothe and worked with him there until 1941. To his staff, Bothe recruited scientists including Wolfgang Gentner, Heinz Maier-Leibnitz—who had done his doctorate with the Nobel Laureate James Franck and was highly recommended by Robert Pohl and Georg Joos, and Arnold Flammersfeld. Also included on his staff were Peter Jensen and Erwin Fünfer.Hentschel, Appendix F; see the entry of Fleischmann.Das Physikalische und Radiologische Institut der Universität Heidelberg, Heidelberger Neueste Nachrichten Volume 56 (7 March 1913).States, David M. (28 June 2001) A History of the Kaiser Wilhelm Institute for Medical Research: 1929–1939: Walther Bothe and the Physics Institute: The Early Years of Nuclear Physics, Nobelprize.org.Landwehr, Gottfried (2002) Rudolf Fleischmann 1.5.1903 – 3.2.2002 , Nachrufe – Auszug aus Jahrbuch pp. 326–328.
In 1938, Bothe and Gentner published on the energy dependence of the nuclear photo-effect. This was the first clear evidence that nuclear absorption spectra are accumulative and continuous, an effect known as the dipolar giant nuclear resonance. This was explained theoretically a decade later by physicists J. Hans D. Jensen, Helmut Steinwedel, Peter Jensen, Michael Goldhaber, and Edward Teller.
Also in 1938, Maier-Leibnitz built a cloud chamber. Images from the cloud chamber were used by Bothe, Gentner, and Maier-Leibnitz to publish, in 1940, the Atlas of Typical Cloud Chamber Images, which became a standard reference for identifying scattered particles.
First German cyclotron By the end of 1937, the rapid successes Bothe and Gentner had with the building and research uses of a Van de Graaff generator had led them to consider building a cyclotron. By November, a report had already been sent to the President of the KWG, and Bothe began securing funds from the Helmholtz Society, the Baden Ministry of Culture, IG Farben, the KWG, and various other research oriented agencies. Initial promises led to ordering a magnet from Siemens in September 1938, however, further financing then became problematic. In these times, Gentner continued his research on the nuclear photoeffect, with the aid of the Van de Graaff generator, which had been upgraded to produce energies just under 1 MeV. When his line of research was completed with the 7Li (p, gamma) and the 11B (p, gamma) reactions, and on the nuclear isomer 80Br, Gentner devoted his full effort to the building of the planned cyclotron.Ulrich Schmidt-Rohr Wolfgang Gentner: 1906–1980 (Universität Heidelberg ).
To facilitate the construction of the cyclotron, at the end of 1938 and into 1939, with the help of a fellowship from the Helmholtz Society, Gentner was sent to Radiation Laboratory of the University of California (now the Lawrence Berkeley National Laboratory) in Berkeley, California. As a result of the visit, Gentner formed a cooperative relationship with Emilio G. Segrè and Donald Cooksey.
After the armistice between France and Germany in the summer of 1940, Bothe and Gentner received orders to inspect the cyclotron Frédéric Joliot-Curie had built in Paris. While it had been built, it was not yet operational. In September 1940, Gentner received orders to form a group to put the cyclotron into operation. Hermann Dänzer from the University of Frankfurt am Main participated in this effort. While in Paris, Gentner was able to free both Frédéric Joliot-Curie and Paul Langevin, who had been arrested and detained. At the end of the winter of 1941/1942, the cyclotron was operational with a 7-MeV beam of deuterons. Uranium and thorium were irradiated with the beam, and the byproducts were sent to Otto Hahn at the (KWIC – Kaiser Wilhelm Institute for Chemistry), in Berlin. In mid-1942, Gentner's successor in Paris, was from Bonn.Jörg Kummer Hermann Dänzer: 1904–1987 (University of Frankfurt).Powers, Thomas (1993) Heisenberg's War: The Secret History of the German Bomb. Knopf. . p. 357.
It was during 1941 that Bothe had acquired all the necessary funding to complete construction of the cyclotron. The magnet was delivered in March 1943, and the first beam of deuteron was emitted in December. The inauguration ceremony for the cyclotron was held on 2 June 1944. While there had been other cyclotrons under construction, Bothe's was the first operational cyclotron in Germany.
Uranium Club