Skip to main content
Select Source:

Segrè, Emilio Gino


(b. Tivoli, Italy, 30 January 1905; d. Lafayette, California, 22 April 1989), nuclear and particle physics, history of science.

Segrè opened the world of antimatter to physical investigation with his discovery of the antiproton, discovered the first of the elements produced by a particle accelerator, provided the critical measurements that established the need for implosion in the ignition of nuclear weapons, and provided important resources for the historical understanding of modern physics. Born Jewish in Italy, he fled because of the Fascist anti-Semitic legislation as did his mentor, Enrico Fermi, whose papers he edited.

Education Born into an industrial family, Emilio Segrè had an early interest in mathematics and physics that was nurtured by his uncle, Claudio Segrè, who was a mining engineer. He was privately educated in addition to attending public school in Tivoli and Rome. After beginning engineering studies in the University of Rome at his father’s behest, he switched to physics after meeting Fermi and sneaking into an International Physics Conference at Como in September 1927. He became part of Fermi’s group at Rome, working with Franco Rasetti, Edoardo Amaldi, and Ettore Majorana, whom Segrè recruited from the engineering school. After completing his military obligation in 1930 he studied transition lines in the atomic spectra of alkaline metals, which should have been forbidden by the laws of quantum mechanics. At Peter Debye’s suggestion, he continued these studies with the Dutch physicist Pieter Zeeman in Amsterdam, which offered superior facilities to those he had in Rome. Perhaps as a result of Zeeman’s intervention, he won a Rockefeller Foundation fellowship that allowed him to study with Otto Stern at the University of Hamburg, who set him to finish an experiment on the dynamics of space quantization and schooled him in the precise experimental techniques that had established Stern’s reputation in molecular beams. Segrè returned to Rome where he worked with Fermi on the explanation of hyper-fine structures in spectra, which they demonstrated resulted from the nuclear magnetic moment as expressed in the Fermi-Segrè formula.

Nuclear Physics Segrè’s generation entered physics at the time quantum mechanics was consolidating thirty years of discovery in atomic physics and the new field of nuclear physics was opening up. Fermi regarded this as a great opportunity to establish a leading school on the frontiers of theoretical and experimental physics. After the Rome group acquired Geiger-Müller counters, a gamma ray spectrograph, a cloud chamber for experimental nuclear studies, and a source of radium, they held an international congress on nuclear physics in Rome in October 1931, which attracted the leading European nuclear physicists. Fermi soon joined them at subsequent international congresses. He quickly made an important contribution to nuclear theory with his theory of beta decay, which explained how some elements transform into others by emitting an electron from the nucleus.

After the discovery of artificial radioactivity by Irène and Frédéric Joliot-Curie, Fermi realized that low-energy neutrons would be an effective tool of nuclear physics. Discovered in 1932 by James Chadwick, neutrons could easily penetrate atomic nuclei since they were not repelled by the positively charged protons, having no charge of their own. Using neutrons produced when alpha particles struck beryllium, the Fermi group began to activate all the elements. Segrè noticed that paraffin, which was used in experiments bombarding silver with neutrons, greatly increased the activity produced. Fermi deduced from this observation that hydrogen atoms, which were abundant in paraffin, had been struck by neutrons, slowing the neutrons down, and that the slower neutrons, contrary to accepted opinion, actually interacted more effectively with the silver atoms. Further experiments showed this to be the case in a number of elements, and a search began for effective moderators of neutrons that would slow them down to increase their effect. At the same time, a patent application was made on the process of slow-neutron activation.

In the fall of 1935, Segrè was appointed to the physics chair at the University of Palermo in Sicily. The following summer, he and his bride, Elfriede, traveled to the United States, where Segrè had spent part of the summer of 1934 at Columbia University in New York City, and visited Ernest Lawrence’s Radiation Laboratory at the University of California, Berkeley. Lawrence had used high-energy neutrons to bombard elements in a program similar to the Fermi group. Returning from Berkeley with discarded fragments of Lawrence’s early cyclotrons, Segrè investigated the radioactive substances produced in them by accelerated deuterons and found them “a true mine of radioactive substances” (Segrè, 1993). More followed from Berkeley, leading Segrè to discover a new

element, technetium, which filled the empty space in the periodic table at atomic number 43, using a molybdenum foil that had been incorporated in a beam deflector. It was the first element created artificially.

Refugee During his second visit to Berkeley in the summer of 1938, he learned that, because of his Jewish origins, his professorship at Palermo had been revoked by Benito Mussolini’s government. At Lawrence’s invitation, he became a research associate at the Radiation Laboratory. There, he worked with Glenn Seaborg to develop the field of nuclear chemistry, and participated in the discovery of plutonium and the determination of its fissile properties.

Segrè’s work with Seaborg began with a search for short-lived technetium-isotopes that resulted in the observation of a nuclear isomerism that produced technicium-99, which is used millions of times annually in medical imaging research and diagnosis. Of the many isotopes that were the object of the Radiation Laboratory’s systematic search for medically useful radiopharmaceuticals, it remains the most effective. Segrè also collaborated with Chien-Shiung Wu in a search for another element missing in the periodic table, element 61. With Robert Cornog, Dale Corson, and K. R. McKenzie, he found element 85, astatine, in 1940.

Fission and Plutonium Although Fermi and his group had supposed that the slow-neutron bombardment of uranium had produced previously unknown elements of greater atomic weight and number, for which Fermi received the Nobel Prize in 1938, the discovery of nuclear fission by Otto Hahn and Fritz Strassmann in Berlin with help from the exiled Lise Meitner at the end of 1938 made it clear that fission had produced the results: elements of approximately half the atomic weight of uranium. The discovery was quickly verified around the world, which alarmed many refugees like Fermi (who had also emigrated to the United States at about this time) and Segrè. Edwin M. McMillan at the Radiation Laboratory found that fission in uranium foils bombarded by the cyclotron produced a true transuranium element, neptunium, and this launched a search for others, led by Segrè and Seaborg. At Fermi’s suggestion, Lawrence gave priority for the project on the 60-inch cyclotron. Assisted by Arthur Wahl and Joseph Kennedy, Segrè and Seaborg found element 94, plutonium, and subsequently showed that it was fissionable with both slow and fast neutrons, making it a potential source of nuclear energy. This work, completed in May 1941, stimulated Lawrence to urge the Briggs Committee, which had been founded as a result of Albert Einstein’s letter to President Franklin Delano Roosevelt, to accelerate research leading to the making of nuclear weapons. Plutonium would supply a nuclear fuel similar to the uranium isotope U235 for such weapons, and it could be made in a nuclear reactor, which Fermi and Leo Szilard were then developing at Columbia University. This project was subsequently transferred to the University of Chicago, where the first chain-reacting nuclear pile was completed in December 1942, after Roosevelt endorsed a full-scale, top secret program to develop nuclear weapons, which became the Manhattan Project.

Lawrence’s role in the project was to develop giant mass spectrographs based on cyclotron technology to separate uranium-235 from uranium-238. Segrè set up an analytical laboratory to perform isotopic analyses of the process. In addition, he began systematic studies of spontaneous fission in uranium and plutonium and, in the summer of 1942, of fission cross sections as well. This information was vital to the success of the atomic bomb program, since an explosive chain reaction would have to be instantaneous: if the chain reaction began too early, the material would be dispersed by the explosion before it could achieve significant energy. This required several generations of fission, each new generation producing exponentially more energy. Any stray neutron could thus predetonate the material and create a “dud” rather than a bomb.

Los Alamos When Seaborg went to the University of Chicago at the end of 1941 to develop means of refining plutonium for the Manhattan Project, Segrè and his associates Owen Chamberlain and Clyde Wiegand went to Los Alamos National Laboratory at the invitation of laboratory leader J. Robert Oppenheimer to continue their investigation of spontaneous fission in uranium and plutonium. They conducted exceedingly sensitive measurements in a Pajarito canyon cabin, remote from the main technical area at Los Alamos, where other experiments produced electric fields and stray neutrons that would spoil them. The higher altitude of Los Alamos allowed more cosmic rays to initiate spontaneous fission than had been the case at Berkeley, but it still occurred only a few times a month. Unfortunately, as additional supplies of plutonium arrived from Chicago, Oak Ridge, and Hanford, the count went up.

Painstaking studies established plutonium-239 had too high a spontaneous fission rate to be assembled by firing one fraction of the critical mass into another, as was done in the uranium bomb. Segrè’s group determined this to be the result of an isotopic impurity, plutonium-240, which had not been observed in accelerator-produced plutonium but which was created in nuclear reactors by neutron bombarded plutonium-239. Since plutonium could not be purified of this contaminant in time to be of use, panic struck, and the entire laboratory was reorganized to develop a new technique for igniting the plutonium bomb, the implosion technique. Ironically, the compartmentalization of the Manhattan Project kept this news from reaching Chicago, where DuPont engineers and scientists at the Metallurgical Laboratory were designing reactors to produce plutonium at Hanford, an effort that would have been in vain had the implosion technique not been perfected at Los Alamos.

Oppenheimer seems to have appreciated the dogged determination exhibited by Segrè in measuring spontaneous fission, and sent him to the Oak Ridge laboratory where Lawrence’s calutrons had been installed to investigate the DA atomic electrons NG atomic electrons ER of accruing enough enriched uranium in one spot to set off a fission reaction unintentionally. Segrè was able to prevent a possible catastrophe by correcting the situation, which had not been anticipated in the design and construction of the plant. He also undertook a study of the effects to be expected from a nuclear explosion.

After the implosion technique was developed, it was decided that a test must be made of the resulting device at an army bombing range in central New Mexico on the Jornada del Muerto, a bleak desert between the Oscura Mountains and the Rio Grande, near the birthplace of Conrad Hilton at San Antonio, New Mexico. Segrè’s group designed a variety of instruments to diagnose the effect of the blast from the neutron and gamma radiation it produced. He observed the test with Fermi, who was able to estimate the force of the blast by dropping confetti as it passed them at a distance of 10 miles.

Berkeley Professor Offered positions at the University of Chicago, where Fermi headed a new Institute for Nuclear Studies, and Washington University, St. Louis, where many of the nuclear chemists with whom he had worked took jobs after the war, Segrè elected to negotiate a full professorship at the University of California and to return to his studies of elementary nuclear processes using the new generation of accelerators built after the war. McMillan’s principle of phase stability made possible the completion of the Radiation Laboratory’s 184-inch cyclotron as a synchrocyclotron, the building of a new electron-synchrotron opened up new areas of exploration at high energies, and Luis Alvarez’s linear accelerator, based on techniques he conceived after working on radar during the war, provided high-energy protons for studies of proton-proton interactions. Frustrated in his efforts to continue research in spontaneous fission and nuclear chemistry by the growing influence of Seaborg, who had convinced Lawrence to support a major effort in nuclear chemistry under his direction, Segrè chose to study high-energy interactions of nuclear constituents instead. This was to lead him to his most important discovery.

Segrè also resumed his efforts, begun with C. S. Wu before the war, to measure the effect of atomic electrons nuclear K-capture by beta decay. This work was completed in 1947 and was the last of the unfinished work that he was able to complete, because many of the radioactive materials needed for studies of heavy elements were now controlled by the newly formed Atomic Energy Commission and rationed to workers like Seaborg, whom Segrè believed would not collaborate with him as an equal.

The field of nucleon interactions seemed to offer opportunities to revive Ernest Rutherford’s studies of nuclear scattering at much higher energies. Segrè’s group spent several years studying interactions between neutrons and protons and between protons and protons. Polarized proton beams from the 184-inch synchrocyclotron supplemented these data, which were also used to compute the wave phase shifts in nuclear interactions with the Los Alamos computer, MANIAC. In order to make it widely available, along with other unclassified work in the field of nuclear physics, Segrè edited Experimental Nuclear Physics and beginning in 1952, the Annual Review of Nuclear Science.

The death of his mentor Fermi in 1954 sundered the last significant connection with his prewar work, and Segrè paid homage to him by editing Fermi’s Collected Papers(1958) and by writing a scientific biography, Enrico Fermi, Physicist (1970).

William M. Brobeck, with whom Segrè had collaborated in the magnet design of the 184-inch cyclotron before the war, designed a proton synchrotron in 1946, and after the completion of the postwar accelerators, Ernest Lawrence succeeded in winning Atomic Energy Commission funding to build a 6.2-billion-electron-volt (BeV) proton synchrotron at the Radiation Laboratory in 1948. Although the accelerator was delayed by the construction of a one-quarter-scale model (used to test the aperature required) and the laboratory’s involvement in the race for the hydrogen bomb, which led to a second laboratory in Livermore, California, the 6.2 BeV machine finally became operational in 1954.

The energy of the machine had been designed to make antiprotons, which had been predicted by nuclear theorists in the 1930s, through proton-proton interactions. Several groups in the Radiation Laboratory competed to develop the appropriate experiment to identify the particle, which would be concealed in a beam of fifty thousand other particles of negative charge produced by the interaction. The new machine was surrounded by their experimental setups, all of which represented variants on two themes: (1) electromagnetic detection and (2) photographic detection of the rare particles.

Segrè’s group, which now included Tom Ypsilantis as well as Chamberlain and Wiegand, won the competition. The experimental setup included a mass spectrograph, which used a magnetic field to separate negatively charged protons from other particles, and time-of-flight detectors and a Cerenkov counter, which measured the velocity of the particles thus separated. These detectors had been used in different configurations by other groups involved in the search. Arranging them in sequence with quadrupole focusing magnets allowed the Segrè-Chamberlain group to deduce the mass of the particle from the momentum and velocity. They found their first evidence for antiprotons in September 1955.

Another branch of Segrè’s group, led by Gerson Goldhaber, sought to detect antiprotons in a different way, through the use of photographic emulsions, which had long been employed in cosmic-ray physics in the search for antiprotons. Amaldi’s group at the University of Rome collaborated with this group in processing the resulting films, and in November 1955 the Amaldi group found a single event in their film corresponding to the theoretical mass of the antiproton. Other Radiation Laboratory groups confirmed the discovery within a month, when a complete track of an antiproton ending in an annihilation by collision with a proton was found in a stack of emulsions. These results were collectively published: thirty-five events by eighteen authors! Segrè and Chamberlain were awarded the Nobel Prize in Physics for the discovery in 1959.

Oreste Piccioni, a Brookhaven physicist who had discussed his plans for an antiproton experiment with Segrè and Chamberlain in December 1954, subsequently filed a lawsuit alleging that they had used those plans in the design of their experiment, from which he had been excluded. Because he filed his suit after the relevant statute of limitations permitted, the suit was never heard. Although many scientists claim credit for work done by others who receive the Nobel Prize, this was the first such claim ever filed in a court of law, and continued to cast a shadow on the discovery for many years. Piccioni was a member of the group that subsequently discovered the antineutron, and Segrè’s group confirmed that it resulted from a process called charge exchange whereby the two particles switch identity.

Antiprotons have become important research tools in high-energy particle physics since the invention of stochastic cooling, which makes it possible to store, concentrate, and direct antiproton beams. The Center for European Research in Nuclear Physics (CERN) built a 300 BeV proton-antiproton colliding-beam accelerator, the Super Proton Synchrotron, in the early 1980s. Fermi-lab’s colliding-beam accelerator has energies over 1 trillion electron volts (TeV) produced in the collision of beams of protons and antiprotons. CERN plans a 14 TeV machine. Slowing down antiprotons has also been accomplished and has led to the assembly of antiatoms.

Antiprotons have also figured prominently in cosmology. Although speculation that galaxies made up of antiprotons, antineutrons, and positrons might exist followed the particles’ original discovery, this has not been supported either by observations of antiprotons in cosmic rays or by any convincing theory. Nevertheless, the search goes on since the big bang theory accepted by most cosmologists indicates that, at least in the first few seconds of the universe, the number of particles and antiparticles was equivalent. Proposed experiments using magnetic spectrometers placed in orbit around the earth seek to solve the mystery of antimatter.

The Segrè group lost much of its collegiality after their success, as Chamberlain and Wiegand sought greater independence. Although the group held together for another decade, Segrè no longer figured as the intellectual leader. He wrote a treatise on the field in 1964, and continued to provide professional leadership through his editorship of Annual Review. He became a senior statesman in science rather than the experimentalist he had been since the 1930s. He gave lectures all around the world, served as a trustee to the National Accelerator Laboratory (later called Fermilab) during its formative period, and received a number of honorary degrees and appointments. After reaching retirement age he returned to Rome where he was given a chair in physics for one year—when he reached Italy’s retirement age.

The premature death of Fermi in 1954 and Segrès’ subsequent involvement in preserving and recounting Fermi’s life and work reinforced Segrè’s interest in history of physics. In addition to publishing a two-volume history of twentieth-century physics, Segrè taught courses in history of physics at the University of California annually before and after his retirement and was an active participant in the field. In addition to his participation in Berkeley’s hiring the soon-to-be-world-famous historian of science Thomas Kuhn in 1956 and assisting Kuhn in the preparation of the Archive for the History of Quantum Physics, Segrè was the Sarton Lecturer at the Tenth International Congress of the History of Science. He was one of the initiators of the Lawrence Berkeley Laboratory history project, and welcomed opportunities to advise, as well as criticize, the work of historians of modern physics.

Segrè was a man of strong views and seldom hesitated to express them. Early in his career, he earned the title of “Basilisk” because, like the mythical beast, his glance made a deep, if not lethal, impression. Segrè’s wife thought him a careful judge of character, although he was not always cautious in expressing his judgments. His eldest son, Claudio, wrote a memoir of his life with his father, which captured Segrè’s difficulty in communicating with him. Although not abusive, he was often remote, preoccupied with work and critical rather than encouraging of his children.

In 1993 his autobiography, A Mind Always in Motion, provided a candid personal view of physics in Rome and Berkeley. Segrè regarded himself as an outsider at the Radiation Laboratory throughout his career, although his use of its accelerators was among the most fruitful for high-energy physics. This detachment not only made him among the more successful physicist-historians of his age, it allowed him to remain aloof from the exigencies of big science and to avoid being captured by the research programs that subsume hundreds of physicists in huge collaborative experiments. It also reflected his perspective, forged in Rome in his work with Fermi, on the human importance and intellectual elegance of doing physics.

Segrè married Rosa Mines in 1972 after the death of his first wife, Elfriede, and remained in good health, living in Lafayette, California, until 1989, when on 22 April he collapsed and died while walking with her, leaving his son, two daughters, and five grandchildren.



“Some Chemical Properties of Element 43.” Journal of Chemical Physics5 (1937): 712–716.

With Glenn T. Seaborg. “Nuclear Isomerism in Element 43.”Physical Review54 (1938): 772.

With Joseph W. Kennedy, Glenn T. Seaborg, and Arthur C.Wahl. “Properties of 94239.” Physical Review70 (1946): 555–556.

Editor. Annual Review of Nuclear Science1–27 (1952–1977).

Editor. Experimental Nuclear Physics. 3 vols. New York: Wiley,1953–1959.

With Owen Chamberlain, Clyde Wiegand, and Thomas Ypsilantis. “Observation of Antiprotons.” Physical Review100 (1955): 947–950.

Nuclei and Particles: An Introduction to Nuclear and Subnuclear Physics. New York: W. A. Benjamin, 1964. Rev. ed. Menlo Park, CA: Benjamin/Cummings Pub. Co., 1977.

Enrico Fermi, Physicist. Chicago: University of Chicago Press,1970.

From X-rays to Quarks: Modern Physicists and Their Discoveries.New York: W.H. Freeman, 1980.

From Falling Bodies to Radio Waves: Classical Physicists and Their Discoveries. New York: W.H. Freeman, 1984.

A Mind Always in Motion: The Autobiography of Emilio Segrè.Berkeley: University of California Press, 1993.


Segrè, Claudio G. Atoms, Bombs & Eskimo Kisses: A Memoir of Father and Son. New York: Viking, 1995.

Seidel, Robert. “Accelerating Science: The Postwar Transformation of the Lawrence Radiation Laboratory.” Historical Studies in the Physical Sciences 13, part 2 (1983): 375–400.

Robert Seidel

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Segrè, Emilio Gino." Complete Dictionary of Scientific Biography. . 28 Jun. 2017 <>.

"Segrè, Emilio Gino." Complete Dictionary of Scientific Biography. . (June 28, 2017).

"Segrè, Emilio Gino." Complete Dictionary of Scientific Biography. . Retrieved June 28, 2017 from

Segrè, Emilio

Emilio Segrè

Physicist Emilio Segrè (1905–1989) made important contributions to the fields of atomic and nuclear physics during his lifetime. He co–discovered three elements, and was part of the scientific team that developed the atomic bomb, which helped to end World War II. Segrè's ultimate honor came in 1959, when he won the Nobel Prize in physics for the antiproton, an honor he shared with colleague Owen Chamberlain.

In the profile found on The National Academies Press Home Page, biographer J. David Jackson described Emilio Segrè as a "complicated man . . . who had high standards and expected others to measure up. He appeared proud, aloof, and somewhat intimidating, but underneath he was welcoming and generous in his support of younger physicists." In Atoms, Bombs, & Eskimo Kisses - A Memoir of Father and Son, a biography written by his son, Claudio, Segrè was remembered as "a world–famous physicist . . . an architect of the atomic age."

Childhood in Italy

Segrè was born on January 30, 1905, in Tivoli, Italy, into a well–to–do Jewish family. He was the youngest son of Giuseppe Segrè, a manufacturer, and Amelia (Treves) Segrè, and arrived late in his parents' life. They were 46 and 37, and his brothers were 14 and 12 when he was born. Because of a slight delay in registering the birth of their new son, authorities listed February 1, 1905 as his official birthday.

Nicknamed Pippi, Segrè's mother taught him to read at an early age. In A Mind Always in Motion: The Autobiography of Emilio Segrè, Segrè recalled that he really enjoyed reading as a child, "especially La scienza per tutti, (Science for Everybody), a popular magazine" of the day. He also enjoyed doing science experiments and kept notebooks of the results.

In his autobiography, Segrè remembered, "As a boy, I lacked any special interest in the law or in history, and most of the dead classicism we learned in high school seemed a boring waste of time to me." He added that he really enjoyed the walks he took in the Roman Forum with his uncle. Segrè attended the local elementary school in Tivoli and graduated from high school in 1922, when he was 17 years old.

Physics Student

Upon completing high school, Segrè began to study engineering. In his autobiography, he recalled, "The end of high school materially changed my studies, which were still my primary occupation. No longer was I forced to study subjects in which I was not interested."

In 1927, Segrè met Italian scientist Enrico Fermi. Shortly after that meeting, Segrè decided to switch his major from engineering to physics, so he could become Fermi's first graduate student. This decision met with opposition from his family, as they believed engineering was a field which would provide more opportunities for him. Nonetheless, Segrè entered the Physics Institute.

Biographer Jackson recalled, "Under the tutelage of Rasetti (experiment) and Fermi (theory) and the paternal oversight of O.M. Corbino, director of the institute, Segrè developed laboratory skills and gained much theoretical knowledge before getting his doctorate after only one year as a physics student." He earned his doctorate in the summer of 1928, and then did his one year of required military service in the Italian Army.

Became College Professor

In his autobiography, Segrè reflected, "The laurea that entitled me to call myself Dr. Segrè completed my formal scholastic career, but my study of physics was to be a lifelong occupation." Between 1929 and 1932, Segrè was an assistant to Corbino at the University of Rome, and also served as an instructor.

As noted by Jackson, Segrè also held a Rockefeller Foundation Fellowship, and worked with Professor Otto Stern in Hamburg, Germany, and Professor Pieter Zeeman in Amsterdam, Holland. Jackson continued that in 1932, Segrè became the equivalent of an assistant professor, and was working with Fermi. Jackson added that "in 1934, the Fermi group switched from atomic spectroscopy to nuclear physics . . . making Rome the center of research with this new tool for nuclear transformations." Subsequently, this scientific team discovered the slow neutron.

The year 1936 would be a time of change for Segrè. He had been courting Elfriede Spiro, a German woman, and the couple married in February of that year. In addition, he was appointed director of the physics laboratory and professor at the University of Palermo.

Segrè reminisced in his autobiography, "Marriage and transfer to Palermo signaled significant changes in my life. From being a young man living in his parents' home, I now became head of a new family; from being a subordinate in the physics Institute in Rome, I became chief of an institute of my own in Sicily."

In the spring of 1937, Segrè and his wife welcomed their first child, a son named Claudio. Life was good. Segrè remembered, "At the University of Palermo I was a young, but important, tenured professor, and my career seemed established." Things would soon change, however.

The political situation in Europe was shaky. Adolf Hitler and the Nazi Party ruled in Germany, and Benito Mussolini and the Fascists were in charge in Italy. Both dictators were purging "undesirables" and "annexing" other countries. In 1938, while on a summer visit to the University of California in Berkeley, Segrè learned he was fired from the University of Palermo because he was Jewish. He made the decision to stay in the United States, in Berkeley.

Teacher and Scientist

Between 1938 and 1943, Segrè held various positions at the University of California, Berkeley. He was a research associate in Ernest Lawrence's laboratory, and was also a lecturer, teaching undergraduate and graduate courses in physics. In his personal life, the Segrè family also welcomed a daughter, Amelia, in 1942.

In 1937, Segrè was working with Carlo Perrier, a Palermo chemist, and they co–discovered the element technetium. As recounted in Notable Scientists: From 1900 to the Present, "Segrè and Perrier suggested the name technetium for the element from the Greek word teknetos, for 'artificial'. . . . This was the first artificially produced new element in scientific history."

While working with Dale Corson and Kenneth MacKenzie in 1940, Segrè and his team found the evidence to prove that element 85 existed. The team suggested the name astatine. Biographer Jackson continued, "After the discovery of plutonium in early 1941, Segrè collaborated with [Glenn T.] Seaborg, [Joseph W.] Kennedy, and [Arthur C.] Wahl on the isolation of the isotope 239Pu by slow neutron bombardment of uranium and then studied its chemistry and nuclear fission properties." Plutonium would play a significant role in world history, as it was the main energy source in the atomic bomb.

Joined "Manhattan Project"

As Segrè wrote in his autobiography, by the early 1940s, the United States government "assumed control of the atomic bomb project." He continued that in September of 1942, the military had taken the lead role in this project. By November of that year, it was determined that a special lab to build the bomb was needed. Segrè's colleague Oppenheimer was selected to be the director, and he asked Segrè to come work at the lab.

Segrè and his family moved to New Mexico, site of the Los Alamos Scientific Laboratory, where he joined the "Manhattan Project." Segrè worked as a physicist and group leader from 1943–1946. In his book, Claudio Segrè described Los Alamos as "a dream scientific community behind barbed wire." He added, "Ironically, atop this mesa in the mountains of New Mexico, my father felt at home. He was a member of the elite." Segrè was committed to the project. He wrote in his autobiography, "I had no choice about going to Los Alamos. War work was a duty to the United States I felt strongly about."

Even though Segrè was a citizen of Italy, an enemy country, he reflected, "My work had put me at the very center of the atomic bomb project. Although I was technically an enemy alien, so were many others who were vital to the enterprise, and I found myself in a relatively important position in the extraordinary adventure that was the Los Alamos laboratory." He continued, "The laboratory had one purpose only: to build the bomb as fast as possible."

On July 16, 1945, the first atomic bomb was exploded near Los Alamos. In August, the United States dropped bombs on Hiroshima and Nagasaki, Japan, ending World War II. In his autobiography, Segrè ruminated, "I have been asked innumerable times my thoughts immediately after the bomb's explosion and the following days . . . I certainly rejoiced in the success that crowned years of heavy work, and I was relieved by the ending of the war."

Back to Berkeley

While in Los Alamos, Segrè and his wife had become U.S. citizens and added a daughter, Fausta, born in 1945, to their family. Segrè had the option to stay in Los Alamos, but he missed the academic life. In early 1946, Segrè and his family headed back to the University of California, Berkeley, where he had accepted a position as a professor in the Physics Department.

Biographer Jackson wrote, "Having left Berkeley in 1943 as a lecturer on a temporary appointment, Segrè returned as a full professor with a regular campus appointment as well as affiliation with the Radiation Laboratory." He was pleased to be teaching physics again.

In many ways, Segrè's life had come full circle. In his autobiography he shared, "I landed in New York on July 13, 1938, expecting to return to Italy in the autumn for the beginning of the school year. Instead, nine years were to elapse before I revisited Italy. By that time, having lost my Italian job, I had built a second career, participated in great historic events, won a superior university position, and become a U.S. citizen and a Californian."

Won Nobel Prize

In 1955, Segrè and his colleagues Owen Chamberlain, Clyde Wiegand, and Thomas Ypsilantis discovered the antiproton, a negatively charged proton. As biographer Jackson noted, "The discovery of the antiproton removed any lingering doubts about the particle–antiparticle symmetry of nature." Many in the scientific community believed this finding might merit the Nobel Prize.

In the biography he wrote about his father, Claudio Segrè recalled, "For eight years, between 1951 and 1959, my father wrestled with frustrations, bitterness, and fear that the Prize would elude him." He added that since his father's friends and colleagues had already won the Nobel Prize, Segrè may have believed his best work was past him.

Jackson continued, "The circumstances surrounding the discovery of the antiproton were not without controversy . . . Even within the group, feelings of injustice prevailed." Only Segrè and Chamberlain were recognized when they announced the 1959 Nobel Prize in Physics. Segrè's son remembered, "Fermi's support in particular—the approbation of his great teacher, his model, perhaps the greatest all–around physicist of his generation—meant almost as much as winning the Prize itself." On December 10, 1959, Segrè and Chamberlain received the Nobel Prize from King of Sweden in Stockholm.

Biographer Jackson wrote, "Segrè's life changed as it does for most upon receiving the Nobel Prize. He became increasingly involved in travel, guest lectures, and committee service, but he was only 54 and stayed as co–head of the research group, now more in an advisory role than as a participant." Segrè also received an honorary degree from the University of Palermo in 1959, and was one of the American scientists named "Men of the Year" for 1960 by Time Magazine on January 2, 1961.

Academic Life

Segrè remained at the University of California, Berkeley, as a Professor of Physics. He also wrote almost 200 scientific papers, and held memberships in the National Academy of Sciences, American Physical Society (fellow), American Philosophical Society, American Academy of Arts and Sciences, and Academia Nazionale dei Lincei. He also wrote numerous books and text books, including the biography of his mentor Enrico Fermi, Physicist, in 1970. In addition, he served as the editor of the Annual Review of Nuclear Science for 20 years and received many honorary degrees.

Of his time at the University of California, Berkeley, biographer Jackson noted, "In departmental and university affairs Segrè took an active role . . . He took very seriously the intellectual health of the department and its future development . . . He played a strong role in departmental faculty meetings, even after retirement."

Segrè's wife died of a heart attack in October of 1970, while the couple was traveling in Italy. Shaken by the sudden loss of his wife, Segrè went through a period of mourning, and ultimately recognized (as told by his son), "There's nothing to be done . . . The pain never goes away." At the end of the 1972 spring term, Segrè retired as a college professor. He was 67. During his tenure, Jackson noted, he was responsible for training 30 Ph.D. students.

Later Years

Biographer Jackson stated that after retirement, Segrè "remained active with traveling and writing taking much of his time. He retained an enduring curiosity about new developments in physics and often sought out a colleague to explain their significance." He also continued to write. From X–Rays to Quarks: Modern Physicists and Their Discoveries was published in English in 1980, and From Falling Bodies to Radio Waves: Classical Physicists and Their Discoveries was released in 1984. He also worked on his autobiography. Segrè had also remarried, taking Rosa Mines as his second wife in 1972.

On April 22, 1989, Segrè died of a heart attack in Lafayette, California. His autobiography, A Mind Always in Motion: The Autobiography of Emilio Segrè, was published after his death, in 1993. Publishers Weekly noted that although Segrè's memoirs gave personal insight into the "fathers of fission," it really was "more the story of the man than of an era."


Nobel Lectures, Physics 1942–1962, Elsevier Publishing Company, 1964.

Notable Scientists: From 1900 to the Present, Gale Group, 2001.

The Scribner Encyclopedia of American Lives, Volume 2: 1986–1990, Charles Scribner's Sons, 1999.

Segrè, Claudio G., Atoms, Bombs, & Eskimo Kisses: A Memoir of Father and Son, Viking, 1995.

Segrè, Emilio, A Mind Always in Motion: The Autobiography of Emilio Segrè, University of California Press, 1993.

World of Physics, 2 vols., Gale Group, 2001.

World of Scientific Discovery, 2nd ed., Gale Group, 1999.


New York Times, April 24, 1989.

Publishers Weekly, September 27, 1993.


Contemporary Authors Online, Gale, 2005. Reproduced in Biography Resource Center. Farmington Hills, Mich.: Thomson Gale. 2005., 2003 (April 14, 2005).

"Emilio Gino Segrè – Biographical Memoirs from the National

Academy of Sciences by J. David Jackson," The National Academies Press Home Page, (November 25, 2004).

"Emilio Segrè," Spartacus Educational - Home Page, (November 25, 2004).

"Emilio Segrè," Welcome to Atomic Archive: Explore the History, Science, and the Consequences of the Atomic Bomb website, (November 25, 2004).

"Emilio Segrè – Biography," website,–bio.html (November 25, 2004).

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Segrè, Emilio." Encyclopedia of World Biography. . 28 Jun. 2017 <>.

"Segrè, Emilio." Encyclopedia of World Biography. . (June 28, 2017).

"Segrè, Emilio." Encyclopedia of World Biography. . Retrieved June 28, 2017 from

Segrè, Emilio Gino

Segrè, Emilio Gino (1905–89) US physicist, b. Italy. In 1937, Segrè discovered technetium – the first element to be artificially produced. In 1940, he helped to discover astatine and plutonium-239. He is, however, chiefly remembered for his discovery of the anti-proton. In 1955, using a Bevatron particle accelerator, Segrè and US physicist Owen Chamberlain bombarded copper with high-energy protons to produce the antiparticle of the proton. Chamberlain and Segrè shared the 1959 Nobel Prize in physics. See also antimatter

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Segrè, Emilio Gino." World Encyclopedia. . 28 Jun. 2017 <>.

"Segrè, Emilio Gino." World Encyclopedia. . (June 28, 2017).

"Segrè, Emilio Gino." World Encyclopedia. . Retrieved June 28, 2017 from