German physicist, also known as Hans Geiger, born on September 30, 1882 in Neustadt an der Haardt died on September 24, 1945, in Potsdam, inventor of the famous counter that bears his name, a device to discover and record energy radioactive particles.
He studied and earned a doctorate at the University of Erlangen, in 1906. Shortly afterwards he moved to the University of Manchester, where he worked with Ernest Rutherford, with whom he collaborated in the determination of the ratio of electric charge to the ground in alpha particles, which turned out to be the same as the of a helium atom that had been stripped of two electrons. Built the first model of its famous particle detector, with whose results Rutherford rightly postulated in 1912, most of the mass of an atom is concentrated in the tiny nucleus.
The alpha particles Geiger counter basically consisted of a full cylinder of gas subject to the action of two electrodes between which established a high electrical potential difference. When you enter an alpha particle gas is ionized and causes a momentary electric shock and a drop in potential that can be measured.
In 1912 he returned to his homeland, with a square at the Physikalisch-Technische Reichsanstalt in Berlin, where he continued his research on atomic structure. Declared the first world war, he went to the front as an artillery officer, and returned to his academic life after the war. In 1924 he collaborated with Walther Bothe in the development of the matches method, allowing to observe longer paths of the most penetrating radiation, and developed the Geiger-Nuttal law which States that in a radioactive family travel of a particle is related to the half-life of the isotope. The characteristics of the Compton effect could be detected. A year later he moved to the University of Kiel as Professor of physics. There he met Walther Müller, who improved the design of your counter, so you should be able to both detect alpha radiation (electrons nuclei) as beta (electrons), and gamma (photons), so the counter has gone down in history as the Geiger-Müller counter.
In 1929 he moved to the University of Tübingen, where he performed early investigations with cosmic rays and participated in the identification of the actinio-A and the torio-A, both isotopes of the same element in the periodic table, polonium. He also did several studies on artificial radioactivity and nuclear fission. In 1936, he accepted a position at the Technische Hochschule in Berlin, where he performed research on the nature of the cosmic radiation until his death, just after the second world war.