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Rabi, Isidor Isaac


(b. Rymanow, Austria-Hungary [later Poland], 29 July 1898; d. New York, New York, 11 January 1988), physics, molecular beams, nuclear physics, physics statesman.

When I. I. Rabi died at age eighty-nine, many of the world’s leading physicists called him the “dean of world physics.” All physicists recognized in Rabi the mark of an unusual man; he brought together that rare combination of a physicist par excellence, a statesman of science with many tangible accomplishments, an advocate for science with direct links to people in high places, and a savant with uncommon wisdom. In 1938 Rabi discovered the magnetic resonance method and for this he was awarded the Nobel Prize in 1944. Rabi could be tough, and his toughness sometimes made people angry; however, even at such times, he was universally admired.

Early Life Rabi grew up in an environment dominated by religion, and the powerful influences of his thorough religious upbringing stayed with him throughout his life. His father, David, came to the United States in late 1898 or early 1899, shortly after his only son was born, and within a few months, he sent for Rabi and his mother, Sheindel.

When Rabi was about one year old, the family was reunited in New York City. Rabi had one sister, Gertrude, who was five years younger. Rabi’s father was uneducated and unskilled; he supported his family through a variety of menial tasks. The family was poor. They lived in a Jewish ghetto on the Lower East Side of Manhattan; more specifically, they lived in a small cultural enclave dominated by other immigrants from their native town, Rymanow, which was in Galicia, the northeastern most province of the old Austro-Hungarian Empire. Rabi spoke English on the streets and Yiddish in his home. When he was nine years old, his family moved to the Jewish community of Brownsville, in Brooklyn.

Rabi’s parents never learned to read or write in English. His given name was Israel Isaac, and in his Yiddish-speaking home he was called Izzy. When Rabi’s mother enrolled him in school, she gave his name as “Izzy” and the teacher wrote down “Isidor”; thus, he became Isidor Rabi. Later, in high school, Rabi brought back the second I. and from then on he was Isidor Isaac Rabi, or more simply, I. I. Rabi. To his family, his associates, and his friends he was always called “Rabi” (pronounced to rhyme with Bobby) or “Rab.”

His parents were devoted to their orthodox Jewish religion both in their temple and their home. Throughout his childhood, Rabi said, “Even in casual conversation, God entered, not every paragraph, more like every sentence” (Rigden, 1987, p. 19). A defining moment came, however, when Rabi, at about age twelve, discovered the public library. He began his exploration of the library shelves in the science section, starting with “A” for astronomy. In one book he encountered the Copernican model of the solar system and quickly grasped its three-dimensional significance. He arrived home on that momentous day and said to his mother, “Who needs God?”

Education After he completed elementary school, Rabi’s parents wanted him to go into Hebrew studies at a yeshiva, but Rabi refused. Nor did he wish to go to Boys High, where all the smart Jewish boys typically went. Rabi, immersed since birth in the Jewish community of his parents, wanted to get into a more typical American environment, so he elected to go to Manual Training High School in Brooklyn. At Manual Training, Rabi started a practice that became a pattern throughout his education: He concentrated and listened carefully while he was in his classes but pursued his own interests outside of class, reading four or five books per week. History was one subject of interest, and during his senior year he got the highest grade in the state on the New York Regents history exam.

Rabi entered Cornell University at Ithaca, New York, in 1916 not only with advanced standing, but also with a scholarship. He was an electrical engineering major until a chemistry course, qualitative analysis, unpopular with most students but an adventure for him, prompted him to switch to chemistry. His extensive reading, outside of class, about the history of science gave him a valuable overview that other students lacked. He graduated in 1919 with a major in chemistry, but chemistry did not satisfy him intellectually, and he decided to get a job rather than continue on to graduate school. For three years Rabi floundered, literally “bumming around” with three friends and reading in the New York Public Library.

In the summer of 1922, one of his friends said to him, “It is time to quit horsing around” (Rigden, 2000, p.34). Rabi returned to Cornell and began a graduate program in chemistry. Still unhappy in that field, he applied for a fellowship in physics but failed to get it. He decided to leave both Cornell and chemistry. Rabi considered applying to Harvard University in Cambridge, Massachusetts, but this decision was altered by the appearance of Helen Newmark, from New York City, who arrived in Ithaca to take a summer course. Helen was an art student at Hunter College. Helen was a New Yorker, Rabi was a New Yorker, and Rabi wanted to be near Helen. In 1923 he entered Columbia University in Manhattan as a graduate student in physics.

Rabi’s real interest was the quantum theory being developed in Europe. No physics professor at Columbia was sufficiently conversant with the new quantum theory to provide guidance, so he had to settle for a dissertation topic that involved measuring the magnetic susceptibility of a series of crystalline salts. The topic bored him, and he procrastinated. He organized a group of students to study quantum theory. Rabi was skeptical about quantum theory; however, the 1922 experiment of Otto Stern and Walther Gerlach that empirically demonstrated what was then called “space quantization” completely contradicted the tenets of classical physics, and Rabi recognized that quantum ideas were needed.

Months passed while Rabi grew crystals and avoided the hard work that his dissertation measurements would require. Then one day, back in the library, Rabi was reading—for pleasure—John Clerk Maxwell’s Treatise on Electricity and Magnetism (1873), and as he read, Rabi recognized a new and simple way to make his measurements. In Rabi’s method the crystal, whose susceptibility was to be determined, was suspended in a solution whose susceptibility could be matched exactly with the suspended crystal, then the solution’s susceptibility was determined by a comparison with water—a simple two-step procedure. In six weeks he not only finished his dissertation, but did so with results of unexcelled accuracy.

On 16 July 1926, Rabi submitted his dissertation to the journal Physical Review. The next day Rabi married Helen Newmark. Three years later their first daughter, Nancy Elizabeth, was born, and in 1934 Helen gave birth to their second daughter, Margaret Joella.

Rabi in Europe From mid-1927 to the fall of 1929, Rabi learned the new physics in Europe. He spent a short amount of time with Arnold Sommerfeld, Erwin Schrödinger, Niels Bohr, and Wolfgang Pauli. However, it was in Hamburg, Germany, that Rabi’s career was determined. At Bohr’s suggestion, Rabi went to Hamburg to work with Pauli. Also at Hamburg was Otto Stern, whose earlier experiment had so impressed Rabi. One day Rabi visited Stern’s molecular-beam laboratory, where two English-speaking physicists worked. As Rabi talked with them, he suggested a different way to do their experiments. Stern invited him to do it. Rabi believed it was an honor to be asked by Stern and felt he could not refuse. Rabi carried out the experiment successfully, and the magnetic field configuration he designed to deflect the beam particles became known as the Rabi field.

After Hamburg, Rabi went to Leipzig to work with Werner Heisenberg. This turned out to be a fortunate decision for Rabi. In 1929 Jewish scholars had great difficulty finding positions as university professors, and because of this, Rabi did not expect to get a faculty position. Heisenberg, who began an extended lecture tour in the United States while Rabi was in Leipzig, began his tour in New York City at the Physics Department of Columbia University. The department was seeking a theoretical physicist who could teach the new quantum physics. Heisenberg strongly recommended Rabi. On 26 March 1929, Rabi received a cable from Columbia University offering him the position of lecturer. Rabi accepted immediately, and the future course of his career was established.

Columbia Professor Rabi came to Columbia University in the fall of 1929 as a theoretical physicist. He taught statistical mechanics and quantum mechanics. Meanwhile, he spent over two years doing theoretical research in solid-state physics. All the time, however, thoughts of molecular beams kept asserting themselves in his mind. He wrote letters to experimentalists raising questions about some of

the troublesome aspects associated with molecular-beam research, asking, for example, about detecting the particles that make up the beam.

In 1931 Harold Urey, Rabi’s Columbia colleague, attempted to determine the nuclear spin of sodium by an analysis of its spectrum. Urey’s results were inconclusive. Rabi was bored with his theoretical solid-state research, so little encouragement was needed for him to change direction. The uncertainty in the nuclear spin of sodium was the challenge, and the experimental method of molecular beams was Rabi’s response.

Molecular beams satisfied Rabi because they enabled him to investigate nature at a fundamental level. Rabi’s approach to physics was strongly influenced by his religious upbringing. Rabi said:

To choose physics in the first place requires a certain direction of interest. In my case it was something that goes to my background, and that is religious in origin … religion as the inspirer of a way of looking at things. Choosing physics means, in some way, you’re not going to choose trivialities. The whole idea of God, that’s real class … real drama. (Rigden, 2000, p. 79)

To determine a basic nuclear property of sodium, element number 11, was for Rabi at the level of the fundamental, or as Rabi expressed it, his molecular-beam experiments measuring basic nuclear properties was “walking the path of God.”

Rabi and his first graduate student, Victor W. Cohen, built the first molecular-beam apparatus in Rabi’s Columbia laboratory and began their investigation of sodium. In this process, Rabi’s personal characteristics had a direct impact on his approach to physics. Rabi’s father had always accused his son of being lazy, and Rabi acknowledged the validity of his father’s accusation. Rabi had been unable to motivate himself to do his dissertation research in the standard labor-intensive way, and so he procrastinated until he found a fast, easy, and accurate way to measure magnetic susceptibilities. In a similar fashion, Rabi and Cohen collected quantities of data, subjected that data to statistical analyses, calculated standard deviations, and so on. Rabi hated it. “This was not for me,” Rabi said. “I’m going to know my answer by the end of the day” (Rigden, 2000, p. 82).

In the molecular-beam method, beam particles are deflected by an inhomogeneous magnetic field. In the Cohen-Rabi experiment, Rabi varied the deflecting fields along the path traversed by the sodium atoms in such a way that the beam of atoms was teased apart into individual beamlets in each of which the sodium atoms were in the same nuclear quantum state. The total number of beamlets depended on the nuclear spin of sodium; therefore, all Rabi had to do was count—count the number of beamlets observed at the detector. In 1933 Cohen and Rabi detected four distinct beamlets reaching the detector, and from this they could infer unequivocally that the nuclear spin of sodium is 3/2. “Count them! It was wonderful. Each one, I suppose, seeks God in his own way” (Rigden, 2000, p. 88). This experimental result was published in 1933 in the Physical Review as “The Nuclear Spin of Sodium”—Rabi’s first experimental result as a molecular-beam physicist.

The series of experiments that dominated the attention of Rabi and his students throughout most of the 1930s was the series on the first two isotopes of the hydrogen atom: hydrogen and deuterium. These experiments began in 1933. Once again, the experiments satisfied something deep within Rabi. The hydrogen atom has the most fundamental nucleus—the single proton—while the nucleus of deuterium, called the deuteron, has the simplest compound nucleus consisting of a single proton and one neutron. “Here you have a system that you could understand,” said Rabi. “Anything I couldn't understand was because there was something to be discovered” (Rigden, 2000, p. 99).

The experiments on the hydrogens actually began in Hamburg in Otto Stern’s laboratory. Stern’s measured result for the magnetic moment of the proton, published in 1933, was a great surprise: It was three times larger than Paul Dirac’s 1928 theory seemed to predict. Stern’s result raised the question of whether the proton is truly an elementary particle in the sense that an electron is an elementary particle. Stern’s unexpected result, plus the importance of understanding the proton, prompted Rabi to initiate his own attempt to measure the proton’s magnetic moment; importantly, he would use a method very different than Stern's. Stern used a beam of molecular hydrogen, while Rabi would use atomic hydrogen. Stern used a strong magnetic field to deflect the hydrogen molecule beam particles, an approach that posed the difficult problem of the accurate calibration of the field strength. Rabi would use a weak magnetic field, whose strength could be directly calculated. Rabi’s experiment avoided many of the difficulties that had complicated Stern’s approach.

Rabi and his students carried out three distinct experiments on the hydrogens during the 1930s. Improved apparatus was designed for each experiment, with accuracy and precision steadily improving. As Rabi had suggested, there were surprises of great significance.

The results of Rabi’s first experiment, published in 1934 (“The Magnetic Moment of the Proton”), indicated an even larger value for the magnetic moment of the proton than had Stern’s surprising result. Furthermore, the two results did not agree within their cited experimental errors. For the proton, there was a 10 percent uncertainty in Rabi’s result and for the deuteron the uncertainty was 26 percent. While there were several sources of error in this first experiment, the largest source of experimental uncertainty was determining exactly how much the hydrogen atoms were deflected by the magnetic field.

In 1936 the second experiment utilized a new method, the refocusing method, which dramatically improved the experimental results and, more importantly, set the stage for the discovery of the magnetic resonance method. Instead of one deflecting magnet, there were two deflecting fields that each beam particle passed sequentially. Between the two deflecting magnets was the new static, T-shaped field. The effect of this new arrangement was threefold. First, no assumption had to be made about the distribution of particle velocities in the beam as all beam particles, independent of their velocity, reached the detector. Second, because the two deflecting magnets acted in tandem to bring all beam particles to the detector, no measurement of the deflection due to a single magnet had to be made. Third, and finally, the static T-shaped magnetic field allowed, for the first time, the signs—positive or negative—of the magnetic moments of the proton and deuteron to be made. In this second experiment, the uncertainty in the measured value of the proton’s magnetic moment was reduced from 19 percent to 5 percent, while that of the deuteron was reduced from 26 percent to 4 percent.

During the planning for the third experiment in 1939, Rabi invented the magnetic resonance method, which provided a greater improvement in the experimental outcome. The experimental apparatus designed for this experiment was similar to that used in the preceding one. The powerful refocusing method was used again, but in a somewhat modified form. The two deflecting magnets were set up to deflect beam particles in opposite directions, and the field strength of the second magnet was set to exactly undo what the first magnet did, that is, refocus the beam particles into the detector. The new feature of this experiment was that the static T-field was replaced by a weak field that oscillated at an adjustable radio frequency. As particles coursed through the apparatus, the frequency of the oscillatory field was slowly varied. Particles entered the oscillatory magnetic field in a particular quantum state. As beam particles traversed the oscillatory field that was oscillating at a particular frequency, they could undergo a quantum transition to a new state and, in this new state, they would not be refocused into the detector and the observed signal at the detector would decrease. From knowledge of the frequency at which the signal at the detector decreased, magnetic moments could be determined. With this third experiment, Rabi obtained what Hans Bethe called “unprecedented accuracy” (Rigden, 1983, p. 355). The uncertainty in the measured values of both the proton’s and deuteron’s magnetic moments was 0.7 percent.

The sharpness of the signals available with the new resonance method revealed fundamental information that had been hidden to Rabi and his students in the less precise results of the earlier experiments. The signals from the deuteron resonances were disturbingly broad, and one of Rabi’s students, Norman F. Ramsey Jr.—a Nobel Prize winner in physics in 1989—began an investigation. When he refined the experimental procedures by lowering the power level of the radio frequency field, he discovered that the broad signal was actually a series of overlapping signals. The analysis of the deuterium data revealed that the deuteron had, in addition to the known magnetic moment, an unknown electric quadrupole moment. This was a momentous discovery, as it negated the central forces assumed to be acting in the atomic nucleus and revealed a new type of nuclear force, a tensor force, that was needed to account for the new nuclear property.

The high point of Rabi’s physical research came in 1939 with the discovery of the nuclear quadrupole moment. During the period 1939–1941, Rabi and his students applied the magnetic resonance method to a range of other atoms and succeeded in measuring nuclear properties to new levels of accuracy and precision. During these years, however, Rabi’s attention became increasingly diverted from his research.

Wartime In 1933 Otto Stern, a Jew, was ordered by the German authorities to leave his faculty position at the University of Hamburg. This troubled Rabi. As Rabi’s experiments continued to improve, conditions in Europe continued to deteriorate. In 1939 Germany invaded Poland; in 1940 France fell to the Germans. In 1940 Rabi was desperate to do something to counter the powerful German military. Adding to his anxiety was the discovery in 1939 of nuclear fission, coupled with his great respect for German physicists who, he thought, might exploit fission for military purposes. Rabi’s opportunity came in October 1940.

In the fall of 1940, England was being bombed by the German air force. To obtain advanced warning of approaching bombers, a radar system using ten-meter radio waves was employed; however, ten-meter waves required very large equipment, which made them impractical for most military applications. Then, however, the magnetron, a high-power source of ten-centimeter microwaves, arrived in the United States from Britain in September 1940. The British magnetron represented a technical breakthrough because of its power level and short wavelength. While the equipment needed to generate and detect ten-meter radio waves was large, the ten-centimeter magnetron opened the door to radar systems small enough to mount in fighter planes as well as naval ships.

On 6 October 1940 the magnetron was taken to the Bell Telephone Laboratory, in Murray Hill, New Jersey, where it was demonstrated. The potential of the magnetron for radar purposes was recognized immediately, and key events quickly followed. On the weekend of 12–13 October, the Microwave Committee, a committee of the National Defense Research Committee formed by President Roosevelt, decided to establish a central laboratory; on 18 October, the Massachusetts Institute of Technology (MIT) was selected as the site for the laboratory; an earlier planned conference, supposedly on nuclear physics, had been scheduled at MIT for 28–31 October, to which a group of physicists were invited for purposes other than nuclear physics. At a luncheon at the Algonquin Club of Boston, plans for the microwave radar laboratory were revealed. Rabi was in this group. Seven days later, he left his Columbia laboratory, left his students, left his home, and left his beloved New York City to join the MIT Radiation Laboratory in Cambridge, Massachusetts. He did not return home for five years.

Rabi immediately went on a lecture tour to recruit physicists for the Radiation Laboratory. And they came. Rabi, the head of the Research Division, initiated the efforts to develop three-centimeter and one-centimeter magnetrons so that smaller radar systems could be designed. He quickly gained the reputation as being able to anticipate military needs, and Lee DuBridge, the laboratory’s director, appointed him associate director.

On 4 January 1941, less than two months after the formation of the laboratory, a radar beam was bounced off a Boston building across the Charles River from MIT. On 7 February, a plane taking off from East Boston Airport (later Logan International Airport) was detected by a Radiation Laboratory radar system.

Rabi, who became a prominent voice of the Radiation Laboratory, worked directly with military leaders. At first, the military officers were unwilling to reveal how the devices they requested were to be used. Rabi, a tough negotiator, refused to work on that basis because he linked the design of apparatus to its use. Soon a trust was developed and mutual respect opened the door to significant discussions.

A new complication entered Rabi’s life in early 1943. J. Robert Oppenheimer, Rabi’s close friend, had been named the director of the Manhattan Project, located in Los Alamos, New Mexico. Oppenheimer needed first-rate talent, and the Radiation Laboratory was one place to get talented physicists. Oppenheimer first asked Rabi to join him at Los Alamos as the associate director of the Manhattan Project, but Rabi refused: he had doubts that the development of the atomic bomb could be concluded in time to affect the outcome of the war. More significantly, by 1943 Rabi was involved at the policy level with officials in Washington, D.C., and he knew that radar was having a direct impact on the conduct of the war, so he maintained his primary focus on that field. However, Rabi did agree to become an advisor to Oppenheimer, and in the summer of 1944, he and Niels Bohr were named senior consultants to him.

In 1944 Rabi won the Nobel Prize in Physics for his development of the magnetic resonance method. This method became the basis for nuclear magnetic resonance (NMR), discovered independently by Edward Purcell and Felix Bloch in 1945 and 1946. NMR quickly became an indispensable tool for chemists. Later, Rabi’s prize-winning work was the basis for magnetic resonance imaging (MRI), which became an indispensable tool for physicians.

In the fall of 1944, Rabi organized a vast writing project at the Radiation Laboratory. Physicists were assigned topics and were told to write a book that fully described the development work they had done during the war years. The result of this effort was the twenty-eight-volume MIT Radiation Laboratory Series. Published from 1947 to 1953, these books on microwave electronics became primary reference sources after the war and enabled scientists to apply new instrumental techniques in their research. More than sixty years later, some of these books were still used. Rabi described the Radiation Laboratory Series as the “biggest thing since the Septuagint” (Rigden, 2000, p. 164).

When the war ended in 1945, the MIT Radiation Laboratory, unlike the Los Alamos Laboratory, closed down immediately. As the physicists returned to their home laboratories, many of them discovered that the world had changed. Many acknowledged that the atomic bomb ended the war; however, many recognized that radar had actually won the war. Both radar and the nuclear bomb were the handiwork of physicists, and after the war physicists were the darlings of society.

The Postwar Years Rabi returned to Columbia University as chairman of the Physics Department. Administrative duties coupled with an increasing number of invitations to serve as an advisor in Washington, D.C., meant that Rabi’s postwar research never achieved the intensity of his earlier research. His most important research result came soon after the war and was one of two experimental results that dominated the discussions at the Shelter Island Conference on Long Island, New York. This conference, held on 2–4 June 1947, brought together twenty-four physicists. It has been described by many of the participants as the most important conference they ever attended. Two experiments were reported at the conference: one by Rabi and one by Willis Lamb. Both experiments revealed subtle disparities in the spectrum of hydrogen. These experiments brought the theory of quantum electrodynamics to its current state of refinement, and Rabi’s experimental results led directly to the discovery of the anomalous magnetic moment of the electron.

When the war ended, a new age began: the nuclear age. New policies were needed to guide U.S. leaders as they considered the implications of the awesome power of the nucleus. The General Advisory Committee (GAC), consisting of prominent physicists, was formed by the Atomic Energy Commission (AEC) to advise the federal government. Oppenheimer served as the chairman of the GAC, and Rabi was a member. When the Russians detonated their first atomic bomb on 29 August 1949, David Lilienthal, chairman of the Atomic Energy Commission (AEC), called for a meeting of the GAC, which gathered on 29–30 October.

The principal topic of the GAC meeting was what the U. S. response to the Russian nuclear success should be. One subject dominated the discussions: whether to start a crash program to build a fusion (hydrogen) bomb. The committee, for persuasive reasons, unanimously recommended against developing a hydrogen-fusion bomb. Rabi and Enrico Fermi wrote a minority report in which they opposed the fusion weapon on ethical grounds: They argued that “such a weapon cannot be justified on any ethical ground” and argued further that it was “an evil thing considered in any light” (Rigden, 2000, pp. 205–207.) President Harry S. Truman, however, ignored the advice of the GAC.

The opposition of the GAC to the hydrogen bomb in 1949 was linked directly to Oppenheimer, and this opposition was taken as evidence that Oppenheimer had connections with the Communist Party. In the 1954 hearing that revoked Oppenheimer’s security clearance, this opposition was used by the “prosecution.” In the hearing, instigated by Lewis Strauss, chairman, Atomic Energy Commission, Rabi was one of the most effective witnesses on Oppenheimer’s behalf, but the outcome was foreordained. Rabi’s friend, J. Robert Oppenheimer, had made enemies and these enemies brought him down.

Rabi is the “father” of two major laboratories. The first, the Brookhaven National Laboratory on Long Island, was established in 1947. Rabi was particularly proud that Brookhaven was a national laboratory that any qualified physicists could use provided they had an idea worthy of investigation.

In 1950 Rabi was named a U.S. delegate to the Fifth General Assembly of UNESCO held in Florence, Italy. After carefully laying the appropriate groundwork, Rabi presented a resolution stating that “to keep the light of science burning brightly in Europe” (Laws and Thompson, 1957, p. 194), a high-energy accelerator laboratory be established in Europe available to all European physicists (the comparison with Brookhaven is obvious). The resolution passed, and the establishment of CERN (Conseil Européen pour la Recherche Nucleaire) in Geneva, Switzerland, was the eventual result.

Rabi always believed he could have averted the tragic outcome of the Oppenheimer hearing if he, Rabi, had advised Oppenheimer on what to do. But Rabi faced a difficult dilemma. At the time of the Oppenheimer hearing, Rabi was working with President Dwight Eisenhower and Dag Hammarskjöld, the secretary general of the United Nations, to plan the first International Conference on the Peaceful Uses of Atomic Energy to be held in Geneva, Switzerland, in August 1955. Lewis Strauss, the chairman of the AEC, was also actively involved in the planning. It was this same Strauss who provided the principal impetus in the drive to discredit Oppenheimer and to bring him down. (Oppenheimer had not only recommended against the development of the hydrogen bomb, but had also embarrassed Strauss in June 1949 during a congressional hearing, and Strauss never forgot it.) As a result, Rabi had to maintain a reasonably cordial working relationship with Strauss while, at the same time, he tried to influence the outcome of the Oppenheimer hearing.

Rabi retired in 1967 as the first university professor at Columbia University; however, he remained active for almost another twenty years. Nine months before he died, he was interviewed on the television program, The Open Mind. “Science,” Rabi said, “is much closer to something you might call religion. It’s something for all humanity. It’s a point of view and direction which we’ve never had before” (1987 inverview).


Rabi’s papers are in the Library of Congress.


With Victor W. Cohen. “The Nuclear Spin of Sodium.” Physical Review 43 (1933): 582–583.

With Jerome M. B. Kellogg and Jerrold R. Zacharias. “The Magnetic Moment of the Proton.” Physical Review 46 (1934): 157–163.

“On the Process of Space Quantization.” Physical Review 49 (1936): 324–328.

With Jerrold R. Zacharias, Sidney Millman, and Polykarp Kusch. “A New Method of Measuring Nuclear Magnetic Moment.” Physical Review 53 (1938): 318.

With Jerome M. B. Kellogg and Norman F. Ramsey, Jr. “An Electric Quadruploe Moment of the Deuteron: The Radiofrequency Spectra of HD and D2 Molecules in a Magnetic Field.” Physical Review 57 (1940): 677–695.

With John E. Nafe and Edward B. Nelson. “The Hyperfine Structure of Atomic Hydrogen and Deuterium.” Physical Review 71 (1947): 914–915.

“Rabi: Scientist and Citizen.” Interview by Richard Heffner. The Open Mind(WPIX, WNET), 12 April 1987. Video and transcript available from


Bernstein, Jeremy. “Profile: Physicist.” The New Yorker, 13 and 20 October 1975.

Day, Michael A. “I. I. Rabi: The Two Cultures and the Universal Culture of Science.” Physics in Perspective 6 (2004): 428–476.

Laws, Walter H. C., and Charles A. Thomson. UNESCO: Purpose, Progress, Prospects. Bloomington: Indiana University Press, 1957.

“Otto Stern and the Discovery of Space Quantization: I. I. Rabi as Told to John S. Rigden.” Zeitschrift für Physik D – Atoms, Molecules and Clusters 10 (1988): 119–120.

Pais, Abraham. The Genius of Science: A Portrait Gallery of Nineteenth-Century Physicists. Oxford; New York: Oxford University Press, 2000.

Rigden, John S. “Molecular Beam Experiments on the Hydrogens during the 1930s.” Historical Studies in the Physical Sciences 13 (1983): 335–373.

———. “The Birth of the Magnetic Resonance Method.” In Observation, Experiment, and Hypothesis in Modern Physical Science, edited by Peter Achinstein and Owen Hannaway. Cambridge, MA: MIT Press, 1985.

———. Rabi: Scientist and Citizen. Cambridge, MA: Harvard University Press, 2000.

John S. Rigden

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Isidor Isaac Rabi

Isidor Isaac Rabi

The American physicist Isidor Isaac Rabi (1898-1988) pioneered in the development of precision atomic-and nuclear-beam measurements.

Isidor Rabi was born on July 29, 1898, in Rymanov in what was then Austria-Hungary. As an infant, he was brought to the United States, where his father engaged in the real estate business in New York City. Rabi attended Cornell University (1916-1919), obtaining a bachelor's degree in chemistry. Deciding to pursue graduate study in physics, he returned to Cornell (1922-1923) and then transferred to Columbia University, where in 1927 he obtained his doctoral degree. In 1926 he married Helen Newmark. The couple had two daughters.

Rabi studied in Europe (1927-1929), working with some of the most outstanding physicists. Otto Stern, with whom he remained for about a year, made the deepest impression on Rabi.

Work on Atomic and Molecular Beams

Immediately on his return to the United States, where he had accepted a position as lecturer in physics at Columbia, Rabi and his student V. Cohen exploited the atomic-and molecular-beam techniques Rabi had developed in Stern's laboratory. Together they proved that the sodium atom has four "hyperfine-structure" energy levels, which unambiguously fixed the "spin angular momentum" of its nucleus at a definite value, equal to 3/2 in units of 2π/h. A few years later, by using beams of atomic hydrogen and deuterium, Rabi and his coworkers confirmed the surprisingly large value for the magnetic moment of the proton which Stern had found in 1933. It was during the course of this work that Rabi developed still another new method, the resonance method, that has since become the basis for all precision atomic-and molecular-beam measurements.

From the point of view of "pure physics, " perhaps the most important measurements that have been made by exploiting Rabi's method have been those on the anomalous magnetic moment of the electron, the quadrupole moment of the deuteron, and the Lamb shift in hydrogen (which has become of great importance for the development of quantum electrodynamics). From the point of view of "practicality, " Rabi's method has found numerous applications, for example, in the highly precise time measurements associated with "atomic clocks, " in precise measurements of magnetic fields, and in the development of the laser, an exceedingly important and versatile instrument. For his atomic-and molecularbeam work and for his discovery of the resonance method, Rabi was elected to the National Academy of Sciences in 1940 and received the 1944 Nobel Prize.

War Work and Postwar Concerns

In 1937 Rabi achieved the rank of full professor at Columbia. Three years later he became associate director of the radiation laboratory at the Massachusetts Institute of Technology (MIT), recently established to develop microwave radar and related equipment for military uses. This work, which was closely related to Rabi's past researches and which relied heavily on British contributions, was eminently successful. In 1948 he received the United States Medal of Merit and the King's Medal for Service in the Cause of Freedom for his wartime efforts.

Rabi was executive officer of the physics department at Columbia (1945-1948), during which time he increased the strength of the department, especially in high-energy and microwave physics. He was also instrumental in establishing the Brookhaven National Laboratory on Long Island in 1945, and he started the movement that resulted in the large high-energy laboratory (CERN) in Geneva, Switzerland. He was the chairman of the General Advisory Committee of the Atomic Energy Commission and served on the President's Science Advisory Committee and the United Nations Science Committee.

One of Rabi's most satisfying postwar achievements was his organization of a number of international United Nations Conferences on the Peaceful Uses of Atomic Energy. Like most physicists, he was deeply impressed by the awesome destructive power of the atomic bomb and worked unrelentingly to find means to ensure that the bomb would never be used again.

Communication is essential to understanding, and understanding is essential to unity: this was a major theme in Rabi's life, especially after the war. It applies not only to countries but also to intellectual disciplines. "What the scientist really desires, " Rabi wrote, "is for his science to be understood, to become an integral part of our general culture, to be given proper weight in the cultural and practical affairs of the world. Like the poet, the scientist would rather be read than praised." According to Rabi, what people of all disciplines sorely require is wisdom: "Without it, knowledge is dry, almost unfit for human consumption, and dangerous in application. … Wisdom makes itself most manifest in the application of knowledge to human needs."

Granted his sincere search for unity, it is not surprising that Rabi, after holding the Higgins professorship of physics for seven years (1957-1964), became the first university professor at Columbia. This professorship is without ties to any particular department. The last subject Rabi lectured on before his retirement in 1967 was "The Philosophical and Social Implications of 20th Century Physics." Rabi explained to his Columbia students, in reference to atomic weapons, "just because we got their first doesn't mean that we should have the power of life and death over the whole world." Rabi died of a long-term illness on January 11, 1988 in New York City.

Further Reading

Rabi's brief My Life and Times as a Physicist appeared in 1960. Although Rabi did not deliver a Nobel lecture, a short biographical sketch of him appears in the Nobel Foundation, Nobel Lectures in Physics (3 vols., 1964-1967). See also Tina Nellie Levitan, Laureates: Jewish Winners of the Nobel Prize (1960). Norman F. Ramsey, Molecular Beams (1956), contains detailed technical information on Rabi's contributions to physics.

Additional Sources

(Rigden, John) Rabi: Scientist and Citizen Basic Books, 1987.

New York Times Biographical Service (January 1988).

Physics Today (October 1988).

Nature (March 10, 1988). □

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Rabi, Isidor Isaac

Isidor Isaac Rabi (rŏb´ē), 1898–1988, American physicist, b. Austria, grad. Cornell, 1919, Ph.D. Columbia, 1927. A teacher at Columbia from 1929, he became professor of physics in 1937. He is known for his work in magnetism, molecular beams, and quantum mechanics. For his discovery and measurement of the radio-frequency spectra of atomic nuclei whose magnetic spin has been disturbed, he was awarded the 1944 Nobel Prize in Physics. From 1952 to 1956 he was chairman of the general advisory committee to the Atomic Energy Commission. He was appointed (1957) chairman of the President's Science Advisory Committee and served as consultant to many national and international organizations.

See his autobiography (1960); Science: The Center of Culture (ed. by R. N. Anshen, 1970).

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