 He was a postdoctoral research associate with Wolfgang Pauli at the Austrian-German Science Foundation, Federal Institute of Technology (ETH) Zurich and University of Leipzig, with Werner Heisenberg from 1930 to 1931.He was Professor at the University of Vienna (1932–1937) and the University of Notre Dame 1937-1955.He was at Oak Ridge National Laboratory from 1955 to 1971.