Isidor Isaac Rabi

Austrian American physicist

• Born: July 29, 1898; Rymanów, Austria-Hungary (now Poland)
• Died: January 11, 1988; New York, New York

Austrian-born physicist Isidor Isaac Rabi developed the magnetic-resonance method to measure the properties of atomic nuclei with unprecedented accuracy. After World War II, he used the idea of science’s universality to bring peoples of the globe together.

Primary field: Physics

Specialty: Atomic and molecular physics

Early Life

Isidor Isaac Rabi was born in the town of Rymanów in Galicia, the northeasternmost province of what used to be the Austro-Hungarian Empire. His father, David Rabi, left Galicia soon after Rabi’s birth and came to the United States; within a matter of months, Rabi’s father sent for his wife, Sheindel, and his infant son. A turning point in Rabi’s life came when, as a nine-year-old child in Brooklyn, he discovered a book on astronomy in the public library. He read about the Copernican solar system, in which planets orbit the sun, and recognized a natural explanation for events that previously had been explained to him only in terms of religion.

Rabi entered Cornell University in 1916 and graduated three years later with a major in chemistry. In 1921, he returned to Cornell as a graduate student of chemistry and soon discovered his passion for physics. He transferred to the physics department at Columbia University in 1923 and received his doctorate in 1926. The day after he submitted his doctoral dissertation, he married Helen Newmark.

In 1927, Rabi obtained a fellowship and went to Europe, where he studied with Niels Bohr, Werner Heisenberg, Wolfgang Pauli, and Otto Stern. While in Zurich with Pauli, he received an offer from Columbia to join the physics faculty there. He returned from Europe in 1929 and began his career as a lecturer.

Life’s Work

In 1931, Rabi applied the molecular-beam method of studying atoms, which he had learned from Stern, to the study of atomic nuclei. In the molecular-beam method, a stream of atoms or molecules moves through a highly evacuated chamber. Within this chamber, the beam passes between the poles of a magnet designed so that magnetic forces are exerted on individual atoms or molecules. Rabi’s method allows the responses of atoms or molecules to these subtle magnetic forces to reveal basic and unknown properties of the nucleus. Rabi made modification after modification to Stern’s basic method and significantly reduced the percentage of uncertainties in experimental data.

Rabi’s molecular-beam work resulted in the molecular-beam magnetic resonance method. In this method, atoms or molecules pass in succession between the poles of three magnets. The second of these magnets produces an oscillating magnetic field. For certain frequencies of the oscillating field, atoms or molecules are ejected from the beam by the third magnet and thus are not registered by the detector. Since frequencies can be measured with great accuracy, this also allows the properties of the nucleus to be determined accurately. For this work, Rabi was awarded the Nobel Prize in Physics in 1944.

World War II brought Rabi’s molecular-beam research to a sudden halt. Long before the United States entered the conflict, Jewish physicists in Europe were being displaced, many of them moving to England and the United States. Adding to the concerns of American physicists was the discovery of nuclear fission by the Austrian physicists Lise Meitner and Otto Frisch, which made it apparent that nuclear energy was now a possibility. The most pressing question concerned what German scientists were doing about it.

During the summer of 1940, British physicists brought a magnetron, a powerful source of microwave radiation recently invented in England, to the United States. They wanted to enlist the aid of American physicists in the development of microwave radar. The magnetron was demonstrated, the Massachusetts Institute of Technology (MIT) Radiation Laboratory was established in Cambridge, and Rabi left Columbia for the Radiation Laboratory. There, he became the head of the research division and, later, the associate director of the laboratory. He took it upon himself to anticipate the course of the war and the type of radar that would be needed by the military services. By the time the United States entered the war in December 1941, a variety of radar systems had been developed. As the conflict proceeded, radar systems from the MIT Radiation Laboratory were being used by Allied forces throughout the war.

In 1943, another wartime laboratory was established in Los Alamos, New Mexico, to develop the atomic bomb. Rabi and J. Robert Oppenheimer, the director of the laboratory, shared a friendship of deep mutual respect, but to Rabi, the radar project was more pertinent to the war effort than the atomic bomb. Nevertheless, Rabi became one of two senior advisers to Oppenheimer, along with Niels Bohr, and made important contributions to the development of the atomic bomb.

When the war ended in 1945, the world faced a powerful new energy source and the issue of establishing policies for its control. In December of that year, Rabi and Oppenheimer formulated a set of ideas that, in the spring of 1946, became the Acheson-Lilienthal report. This document proposed placing atomic energy in the hands of an international agency, thereby dissociating it from the interests of any one nation. In June 1946, these ideas were presented to the United Nations. To Rabi’s great disappointment, the Russian delegate, Andrei Gromyko, rejected the proposal. Three years later, the Russians detonated their first atomic bomb, and the arms race was under way.

The Russian achievement prompted a few influential Americans to propose a crash program to develop the hydrogen bomb. Rabi was then a member of the General Advisory Committee of the Atomic Energy Committee. Chaired by Oppenheimer, the committee was called into session to consider the question of a fusion-bomb program. It unanimously opposed the development of such a weapon, and Rabi and Enrico Fermi wrote a minority opinion in which they expressed their moral disapproval for a weapon that cannot be confined to any military target. Once again, Rabi was on the losing side; the United States detonated a fusion bomb in 1952, and nine months later, the Russians followed suit.

Throughout the postwar years, the culture of science was, for Rabi, a means for joining together peoples of the world. In 1950, as a US delegate to the fifth General Assembly of the United Nations Educational, Scientific, and Cultural Organization, Rabi proposed that European nations unite in the formation of a scientific laboratory. Two years later, the decision was made to establish the European Organization for Nuclear Research (CERN) in Geneva, Switzerland.

In 1954, Rabi proposed an international conference on the peaceful uses of atomic energy. This proposal, inspired by a speech given by US president Dwight D. Eisenhower, was presented to the United Nations by Secretary of State John Foster Dulles. Dag Hammarskjöld, secretary-general of the United Nations, was an enthusiastic supporter of the idea, which Rabi and Hammarskjöld together promoted. In 1955, the first International Conference on the Peaceful Uses of Atomic Energy was held in Geneva. According to Hammarskjöld, this conference was the beginning of détente.

During the mid-1950s, Rabi was the chair of the Science Advisory Committee (SAC) of the Office of Defense Mobilization. The Russian launch of Sputnik in1957 prompted President Eisenhower to consult the SAC. Rabi proposed six specific actions, all of which Eisenhower accepted immediately. Rabi suggested that SAC needed direct access to the president and that the president needed a science adviser. He remained a member of the President’s Science Advisory Committee—the new name for the SAC—until the committee was dissolved by the Nixon administration.

Rabi died on January 11, 1989, in New York City.

Impact

As he began his work in the early 1930s, Rabi was determined to bring American physics out of the shadow of European physics. It was through the work of scientists such as Rabi and Oppenheimer that American physics became preeminent in the early 1940s. Rabi’s influence in this regard is particularly pervasive, as his research continues to be cited by contemporary physicists. He is remembered in particular for his use of nuclear magnetic resonances to examine atomic properties. The new precision of his techniques led to such unanticipated discoveries as the quadrupole moment (a description of the nuclear charge distribution) of the heavy hydrogen nucleus.

Rabi saw clearly the role of science and technology in the modern world and worked to promote that role in the interest of international peace. As a diplomat and advisor, Rabi used science to bridge national, religious, and ideological differences. CERN, the organization that he helped found, remains one of the foremost physics laboratories in the world.

Bibliography

Day, Michael A. “I. I. Rabi: The Two Cultures and the Universal Culture of Science.” Physics in Perspective 6.4 (2004): 428–76. Print. Examines Rabi’s views on the nature of science and society, specifically on the relation of science to government, education, and religion.

Krige, John. “I. I. Rabi and the Birth of CERN.” Physics Today 57.9 (2004): 44–48. Print. Describes Rabi’s role in the conception and creation of the Center for European Nuclear Research (CERN).

Rabi, Isidor Isaac. Science: The Center of Culture. New York: World, 1970. Print. A collection of Rabi’s articles and speeches.

Rigden, John S. Rabi: Scientist and Citizen. 1987. Cambridge, MA: Harvard UP, 2000. Print. A biography tracing Rabi’s life and work.