Pauli, Wolfgang (vôlfˈgäng pouˈlē) [key], 1900–1958, Austro-American physicist, b. Vienna. He studied first with A. Sommerfeld at Munich and then with Niels Bohr at Copenhagen. After lecturing (1923–28) at the Univ. of Hamburg, Pauli was appointed professor at the Federal Institute of Technology, Zürich, which became famous under his direction. In the United States he was a member (1935–36, 1940–46) of the Institute for Advanced Study at Princeton. In 1946 he became a U.S. citizen. He divided his later years between Princeton and Zürich. He was awarded the 1945 Nobel Prize in Physics for his enunciation (1925) of the Pauli exclusion principle, fundamental to quantum mechanics, according to which no two electrons in an atom may be in the same quantum state. It was later found that certain other particles also are governed by the principle. Among his many other achievements was the postulation of the existence of the neutrino (1930), more than a quarter century before it was directly observed in 1956.