Gustav Ludwig Hertz (22.07.1887-30.10.1975) was a German physicist and a member of the Academy of Sciences of the GDR. He was a nephew of Heinrich Hertz. He was born in Hamburg. He graduated from the universities of Munich and Berlin (1911). In 1913—20 he worked at the University of Berlin, in 1920—25 in the laboratory of the Philips works (Eindhoven), in 1925—27 he was professor at the University of Halle, in 1928—35 at the Higher Technical School in Berlin, in 1935—45 he headed the Siemens research laboratory in Berlin, in 1945—54 he worked in the USSR, and in 1954—62 he was professor and director of the Physical Institute of the University of Leipzig.
His main research was in the field of spectroscopy. In 1912—14, together with J. Franck, he carried out a series of experiments on the collision of electrons with gas atoms (the Franck — Hertz experiments), which led them to establish certain regularities of these collisions (Nobel Prize, 1925). The Franck — Hertz experiments were the first to prove the existence of discrete energy levels in atoms, which directly confirmed Bohr's quantum theory of the atom.
He studied X-ray absorption spectra. In 1920 he established the rule for irregular doublets (the Hertz rule). He carried out a number of studies on diffusion, electron emission, discharges in gases, plasma physics, ultrasound and semiconductors. He developed a method of separating isotopes by diffusion.
A member of the academies of sciences of a number of countries and a foreign member of the USSR Academy of Sciences (1958). USSR State Prize (1951). National Prize of the GDR (1955).