Geiger, Hans Wilhelm (1882–1945)
German physicist who, with Ernest Rutherford
devised in 1908 a method of detecting and counting alpha
particles. This device, with modification, became the Geiger
counter (or Geiger-Muller counter). Geiger and Ernest Marsden
measured the deflection of alpha particles by thin metal foil in 1909 (see
experiment and atomic model), and this phenomenon was the basis of Rutherford's
discovery of the atomic nucleus.