Kusch, Polykarp (1911–1933)

German-born US physicist who was awarded the Nobel Prize for Physics in 1955 for determining the magnetic moment (or magnetic strength) of the electron.

Kusch worked under Isidor Rabi on spectroscopy using atomic and molecular beams. He investigated the interactions of the constituent particles of atoms and molecules with each other and with an external magnetic field. From a study of the energy levels of certain elements, he was able to deduce a very accurate value for the magnetic moment of the electron. He found a small discrepancy between the observed magnetic moment and that predicted by theory. This discrepancy was of great significance to the theory (now known as quantum electrodynamics) describing the interactions of electrons and electromagntic fields. His discovery was confirmed by independent experiments done by Willis Lamb, with whom he shared the Nobel Prize.

Born in Blankenburg, Germany, he went to the USA in 1912. He was educated at Case Institute of Technology, Cleveland, Ohio, and the University of Illinois, where he completed his doctorate in 1936. He spent his career mainly at Columbia University, New York City, rising from associate professor (1946) to dean of faculty (1969) and provost (1970). In 1972 he was appointed professor of physics at the University of Texas at Dallas.