Atomic physicists Ernest Lawrence, Enrico Fermi, and Isidor Rabi. Ernest Orlando Lawrence (August 8, 1901 - August 27, 1958) was a pioneering American nuclear scientist and winner of the Nobel Prize in Physics in 1939 for his invention of the cyclotron. Enrico Fermi (29 September 1901 - 28 November 1954) was an Italian physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. Isidor Isaac Rabi (July 29, 1898 - January 11, 1988) was an American physicist who won the Nobel Prize in Physics in 1944 for his discovery of nuclear magnetic resonance, which is used in magnetic resonance imaging.