HERTZ, GUSTAV

HERTZ, GUSTAV (1887–1975), physicist; with James Franck,* provided proof for Max Planck's* quantum theory. Born in Hamburg, a nephew of physicist Heinrich Hertz, he studied at Berlin,* where he was mentored by Heinrich Rubens and took a doctorate in 1911. While collaborating with Franck in the laboratory of Emil Warburg, he detected quantized energy transfer in collisions between electrons and atoms. This initial proof of the quantum theory, formulated by Planck in 1900, brought both researchers the 1925 Nobel Prize for physics. Although Hertz was wounded in World War I, he completed his Habilitation in 1917 and became Privatdozent at Berlin. After working in Holland at the incandescent-lamp laboratory of the Philips Company, he took a professorship in 1925 at Halle. He moved to Berlin's Technische Hochschule in 1928 and supervised construction of Germany's premier physics institute. A popular teacher, his colloquium with the theorist Richard Becker and the physical chemist Max Vollmer attracted a wide range of scientists. His use of diffusion for the separation of gas mixtures was integral to isolating the uranium isotope 235. Although Hertz was of Jewish ancestry, his status as a wounded war veteran secured him for the early years of the Third Reich. Despite protests from his students, he was finally dismissed in 1935. Allowed to remain and work in Berlin—the Nazis feared that he would take his knowledge elsewhere—he directed the Siemens research laboratory until the end of World War II. He allegedly went to the Soviet Union* in 1945 by choice (sources disagree on this) and supervised construction of a Soviet research institute. Back in East Germany in 1954, he ended his career as director of Leipzig's Physics Institute.