Walther Bothe
1891–1957, Oranienburg, Germany, Heidelberg, Germany
German physicist who invented the coincidence method in nuclear and particle physics, applying it to cosmic rays and the Compton effect.
Bothe earned his doctorate in Berlin in 1914 under Max Planck, then served in the First World War, during which he was taken prisoner in Russia. After the war he worked with Hans Geiger in Berlin, where he developed the coincidence method. He became a professor at Giessen in 1930 and at Heidelberg in 1934, when he was appointed director of the physics department of the Kaiser Wilhelm Institute for Medical Research, where he supervised the construction of Germany's first cyclotron. He shared the 1954 Nobel Prize in Physics with Max Born.
Nobel-winning work
In 1924–1925, working with Hans Geiger at the German national physics laboratory (PTR), Bothe developed the 'coincidence method' (Zusammenfallmethode): two Geiger–Müller counters wired so that only simultaneous events in both were registered, suppressing background to a minimum. With it, the Bothe–Geiger experiment of 1925 demonstrated that Compton scattering of X-rays conserves energy and momentum in each individual collision — refuting the BKS theory of merely statistical conservation.
Bothe later applied coincidence counting to cosmic rays, measuring their directions of arrival and penetrating power with Werner Kolhörster. 'The coincidence method and his discoveries made therewith' were recognized by the 1954 Nobel Prize in Physics, which he shared with Max Born.
Workplaces: Max Planck Institute for Medical Research (then Kaiser Wilhelm Institute), Heidelberg, University of Giessen
Germany