Geiger, Hans (Wilhelm) (1882–1945)

German physicist who produced the Geiger counter. He spent the period 1906–12 in Manchester, England, working with Ernest Rutherford on radioactivity. In 1908 they designed an instrument to detect and count alpha particles, positively charged ionizing particles produced by radioactive decay.

In 1928 Geiger and Walther Müller produced a more sensitive version of the counter, which could detect all kinds of ionizing radiation.

Geiger was born in Neustadt, Rheinland-Pfalz, and studied at Munich and Erlangen. On his return from Manchester 1912, Geiger became head of the Radioactivity Laboratories at the Physikalische Technische Reichsanstalt in Berlin, where he established a successful research group. He subsequently held other academic posts in Germany; from 1936 he was at the Technical University, Berlin. Subjects that Geiger studied under Rutherford include the mathematical relationship between the amount of alpha scattering and atomic weight, the relationship between the range of an alpha particle and its velocity, the various disintegration products of uranium, and the relationship between the range of an alpha particle and the decay constant, which is a measure of the rate at which alpha particles are emitted. From 1931 onwards Geiger mainly studied cosmic radiation.