Hans Geiger

Johannes Wilhelm Template:NoboldHansTemplate:Nobold Geiger (Template:IPAc-en Template:Respell;<ref>Template:Cite web</ref> Template:IPA; 30 September 1882 – 24 September 1945) was a German experimental physicist. He is known as the inventor of the Geiger counter, a device used to detect ionizing radiation, and for carrying out the Rutherford scattering experiments, which led to the discovery of the atomic nucleus. He also performed the Bothe–Geiger coincidence experiment, which confirmed the conservation of energy in light-particle interactions.

He was the brother of meteorologist and climatologist Rudolf Geiger.

Biography

Early years

Johannes Wilhelm Geiger was born on 30 September 1882 in Neustadt an der Haardt, Germany, the son of Indologist Wilhelm Geiger, who was a professor at the University of Erlangen.

In 1902, Geiger started studying physics and mathematics at the University of Erlangen, where he received his Ph.D. under Eilhard Wiedemann in 1906 with a thesis on electric discharge in gases.<ref>Template:Cite journal</ref><ref name="auto1">Template:Cite journal</ref>

After graduating, Geiger received a fellowship to the University of Manchester, where he worked as an assistant to Arthur Schuster. In 1907, after Schuster's retirement, Geiger began to work with his successor, Ernest Rutherford, and in 1908, along with Ernest Marsden, conducted the famous Geiger–Marsden experiment (also known as the "gold foil experiment"). This process allowed them to count alpha particles<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite book</ref><ref name="auto1"/> and led Rutherford to start thinking about the structure of the atom. He was elected a Member of the Manchester Literary and Philosophical Society on 29 November 1910.

In 1911, Geiger and John Mitchell Nuttall discovered the Geiger–Nuttall law (or rule) and performed experiments that led to Rutherford's atomic model.<ref>H. Geiger and J.M. Nuttall (1911) "The ranges of the α particles from various radioactive substances and a relation between range and period of transformation", Philosophical Magazine, series 6, vol. 22, no. 130, pages 613-621. See also: H. Geiger and J.M. Nuttall (1912) "The ranges of α particles from uranium", Philosophical Magazine, series 6, vol. 23, no. 135, pages 439-445.</ref>

Middle years

In 1912, Geiger was named head of radiation research at the Physikalisch-Technische Reichsanstalt (now the Physikalisch-Technische Bundesanstalt) in Charlottenburg, where he worked with James Chadwick and Walther Bothe (winners of the 1935 and 1954 Nobel Prize in Physics, respectively).<ref name="auto">Template:Cite web</ref> Work was interrupted when Geiger served in the German military during World War I as an artillery officer from 1914 to 1918.

In 1924, Geiger and Bothe carried out the Bothe–Geiger coincidence experiment that confirmed the Compton effect, which helped earn Arthur Compton the 1927 Nobel Prize in Physics.<ref name="auto1" /> Bothe received the Nobel Prize in Physics for their experiment in 1954, after Geiger's death.<ref name=":02">Template:Cite journal</ref>

In 1925, Geiger began a teaching position at the University of Kiel. In 1928, Geiger and his student, Walther Müller, created the Geiger–Müller tube. This new device not only detected alpha particles, but also beta and gamma particles, and is the basis for the Geiger counter.<ref>Template:Cite journal</ref><ref>See also:

1. Geiger, H. and Müller, W. (1928) "Das Elektronenzählrohr" (The electron counting tube), Physikalische Zeitschrift, 29: 839-841.
2. Geiger, H. and Müller, W. (1929) "Technische Bemerkungen zum Elektronenzählrohr" (Technical notes on the electron counting tube), Physikalische Zeitschrift, 30: 489-493.
3. Geiger, H. and Müller, W. (1929) "Demonstration des Elektronenzählrohrs" (Demonstration of the electron counting tube), Physikalische Zeitschrift, 30: 523 ff.</ref> Geiger was awarded the Hughes Medal in 1929 for this work.

In 1929, Geiger was appointed Professor of Physics and Director of Research at the University of Tübingen, where he made his first observations of a cosmic ray shower. In 1936, he took a position at Technische Hochschule Berlin (now Technische Universität Berlin), where he continued to research cosmic rays, nuclear fission, and artificial radiation until his death in 1945.<ref name="auto1"/>

Later years

Beginning in 1939, following the discovery of nuclear fission, Geiger became a member of the Uranium Club, the German investigation of nuclear weapons during World War II. The group splintered in 1942 after its members came to believe that nuclear weapons would not play a significant role in ending the war.<ref name="auto"/>

Although Geiger signed a petition against the Nazi government's interference with universities, he provided no support to colleague Hans Bethe (winner of the 1967 Nobel Prize in Physics) when he was fired for being Jewish.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>

Geiger endured the Battle of Berlin and subsequent Soviet occupation in April/May 1945. A couple of months later he moved to Potsdam, where he died on 24 September 1945.

See also

• Geiger (crater)

External links

• Template:Commons category-inline
• Annotated bibliography for Hans Geiger from the Alsos Digital Library for Nuclear Issues