Born in Austria, I. I. Rabi came to the United States with his parents at an early age. He attended Cornell and Columbia Universities, receiving his Ph.D. in physics from the latter in 1927. During a post-doctoral year in Germany Rabi worked with Otto Stern and learned about Stern's experiments (conducted with Walther Gerlach) on the analysis of atomic and molecular structure by means of atomic and molecular beams. Upon his return to the United States in 1929, Rabi worked on methods for extending and refining the Stern-Gerlach techniques. He eventually made a number of important discoveries regarding the magnetic properties of the nucleus and of subatomic particles--discoveries that later found application in a number of fields, including nuclear magnetic resonance, masers and lasers, and time measurement by means of atomic clocks. During World War II, Rabi worked on the development of radar devices and nuclear weapons. At the war's conclusion, he devoted most of his time and energy to the political aspects of scientific and technological development, serving as chairman of the U.S. Atomic Energy Commission from 1952 to 1956. Rabi died in 1988 at the age of 91.
Isidor Isaac Rabi was born on July 29, 1898, in Rymanow (also given as Raymanou or Rymanov), Galicia, then a part of the Austro-Hungarian empire. Rabi's parents were David Rabi and the former Janet (also given as Jennie or Scheindel) Teig. The senior Rabi emigrated to the United States shortly after his son's birth and, in 1899, sent for his family to join him in New York City. David Rabi has been described by various biographers as an unskilled worker, a tailor, and an owner of a grocery store; Rabi himself said that his father started out by doing odd jobs, such as delivering ice, and then "graduated into work in the sweatshop, making women's blouses." Yiddish was the only language spoken in the Rabi household, and young Isidor learned his English on the streets. He was a quick learner, however, and did well in the public schools of New York City. After graduating from Brooklyn's Manual Training High School in 1916, he entered Cornell University with plans to major in electrical engineering. He eventually changed his major to chemistry, though, graduating with a bachelor of science degree in 1919. He then spent three years working as a chemist before returning to Cornell for graduate work. Rabi soon discovered that his real interest was physics, and in 1923 enrolled in a doctoral program in this field at Columbia University. In order to support himself at Columbia, Rabi took a job teaching physics at the City College (now City University) of New York, a post he held until he received his Ph.D. in 1927.
Pursues Postgraduate Studies in Europe
For his postdoctoral studies, Rabi planned a two-year tour of the most important scientific institutions in Europe, including Munich, Copenhagen, Hamburg, Leipzig, and Zürich. While on tour he studied with such leading figures as Arnold Sommerfeld, Niels Bohr , Wolfgang Pauli , Werner Heisenberg , and Otto Stern . The visit with Stern may have been the most significant stop on the tour, because Stern's work at Hamburg closely corresponded to Rabi's own field of interest and the subject of his doctoral thesis, the effects of magnetic fields on matter. In 1922, Stern and Walther Gerlach had developed methods for creating beams of atoms or molecules that could be used to study the magnetic properties of the atomic nuclei in these beams. For his discoveries in this field, Stern would go on to win the 1943 Nobel Prize in physics.
In 1929, when Rabi returned to the United States, he began his own research on the use of atomic and molecular beams to study nuclear properties. This work took place at Columbia, where he had been appointed lecturer in physics; over the next decade, he worked his way up the professional ladder, being promoted to assistant professor in 1930, associate professor in 1932, and then full professor of physics in 1937. Throughout this period, Rabi refined his methods of atomic and molecular beam analysis, eventually making a number of important discoveries.
Discovers Atomic Spin Properties
The Stern-Gerlach experiment of 1922 had showed that a molecular beam passing through a magnetic field splits into two parts. The discovery of electron spin by George Uhlenbeck and Samuel Goudsmit in 1927 explained this phenomenon: they demonstrated that electrons in an atom can spin in only one of two directions; hence, electrons spinning in one direction split into one beam, while those spinning in the opposite direction split into another.
As Rabi studied this effect in more detail, he realized that the magnetic properties of an atom are more complex than first suggested by the Stern-Gerlach experiment. In the first place, the nucleus itself spins, creating its own magnetic field. Thus, there will be interactions among the magnetic field of the nucleus, the magnetic fields of the orbital electrons, and any external magnetic field that is applied to the atom.
In his research, Rabi was able to sort out and quantify many of these discrete properties. His most important accomplishment was to determine the magnetic moment of the nucleus, an important piece of information essential to the construction of an accurate model of the atom. By 1937, Rabi had made yet another discovery, namely that he could reverse the spin of a nucleus by imposing an external radio-frequency signal on an atomic or molecular beam. That discovery has been used in a number of important applications; one of these, nuclear magnetic resonance (NMR), is now among the most powerful analytical tools available to scientific investigators and medical diagnosticians. Rabi was awarded the 1944 Nobel Prize in physics for his work on "the resonance method for recording the magnetic properties of the atomic nucleus."
During World War II, Rabi took a leave of absence from Columbia to worked on the development of microwave radar devices at the Massachusetts Institute of Technology. Though most of his colleagues in the scientific community were devoting their wartime efforts to the development of atomic weapons, Rabi believed that, of the two projects, radar would be more immediately useful to the U.S. war effort--though he did consult on nuclear weapons projects as part of the Manhattan Project. At the war's conclusion, Rabi returned to Columbia as chairman of the physics department. He devoted his time primarily to administrative responsibilities and to the effort by scientists to restrict military control of nuclear technology. "Speaking for the group of men who created these weapons," Rabi once said in Atlantic Monthly, "I would say that we are frankly pleased, terrified, and to an even greater degree embarrassed when we contemplate the results of our wartime efforts." In order to monitor the use of atomic energy and weapons, Rabi became a member of the General Advisory Committee of the Atomic Energy Commission in 1945 and then served as chairman of the committee from 1952 to 1956 (after the retirement of J. Robert Oppenheimer). He was an advisor to NATO and the United Nations, and served as a member of the American delegation to UNESCO, overlooking the European Center for Nuclear Research (CERN) in Geneva.
Rabi was married to Helen Newmark in 1926. They had two daughters, Nancy Elizabeth and Margaret Joella. In addition to the Nobel Prize, Rabi won a host of other awards, including the Elliott Cresson Medal of the Franklin Institute in 1942, the U.S. Medal for Merit (the country's highest civilian service award) in 1948, the Niels Bohr International Gold Medal in 1967, the Atoms for Peace Award in 1967, the Franklin Delano Roosevelt Freedom Medal in 1985, and the Public Welfare Medal of the National Academy of Sciences in 1985. Rabi died in New York City on January 11, 1988.
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