Geiger, Hans Wilhelm 1882-1945
German physicist

Born in Neustadt-an-der-Haardt, he was educated at the University of Erlangen where he received his PhD in 1906. He then worked under Ernest Rutherford at Manchester (1906-12). With Rutherford, he devised a means of detecting alpha particles (1908), and subsequently showed that two alpha-particles are emitted in the radioactive decay of uranium. With J M Nuttall he demonstrated the linear relationship between the logarithm of the range of alpha-particles and the radioactive time constant of the emitting nucleus, now called the Geiger-Nuttall rule. In 1912 he became head of the Physikalisch Technische Reichsanstalt in Berlin, and in 1925 professor at Kiel University. There, he and Walther M�ller made improvements to the particle counter, resulting in the modern form of the Geiger-M�ller counter, which also detects electrons and ionizing radiation.