Italian-American nuclear physicist and radiochemist (1905–1989)
"Segrè" redirects here. For Emilio's nephew who is also a physicist, seeGino Segrè. For other people with the surname, seeSegre (surname). For other uses, seeSegre.
Born inTivoli, nearRome, Segrè studied engineering at theUniversity of Rome La Sapienza before taking up physics in 1927. Segrè was appointed assistant professor of physics at the University of Rome in 1932 and worked there until 1936, becoming one of theVia Panisperna boys. From 1936 to 1938 he was director of the Physics Laboratory at theUniversity of Palermo. After a visit toErnest O. Lawrence'sBerkeley Radiation Laboratory, he was sent amolybdenum strip from the laboratory'scyclotron accelerator in 1937, which was emitting anomalous forms ofradioactivity. Using careful chemical and theoretical analysis, Segrè was able to prove that some of the radiation was being produced by a previously unknown element, named technetium, the first artificially synthesizedchemical element that does not occur in nature.
Segrè was an active photographer who took many pictures documenting events and people in the history of modern science, which were donated to theAmerican Institute of Physics after his death. The American Institute of Physics named its photographic archive of physics history in his honor.
Emilio Gino Segrè was born into aSephardic Jewish family inTivoli, nearRome, on 1 February 1905, the son of Giuseppe Segrè, a businessman who owned a paper mill, and Amelia Susanna Treves. He had two older brothers, Angelo and Marco.[2] His uncle, Gino Segrè, was a law professor.[3] He was educated at theginnasio in Tivoli and, after the family moved to Rome in 1917, theginnasio andliceo in Rome. He graduated in July 1922 and enrolled in theUniversity of Rome La Sapienza as anengineering student.[4]
After a stint in theItalian Army from 1928 to 1929,[4] during which he was acommissioned as asecond lieutenant in theantiaircraft artillery,[8] Segrè returned to the laboratory on Via Panisperna. He published his first article, which summarised his thesis, "On anomalous dispersion in mercury and in lithium", jointly withEdoardo Amaldi in 1928, and another article with him the following year on theRaman effect.[9]
Segrè was appointed assistant professor of physics at the University of Rome in 1932 and worked there until 1936, becoming one of theVia Panisperna boys.[13] In 1934, he met Elfriede Spiro, a Jewish woman whose family had come from Ostrowo inWest Prussia, but had fled toBreslau when that part of Prussia became part of Poland after World War I. After theNazi Party came to power in Germany in 1933, she had emigrated to Italy, where she worked as a secretary and an interpreter. At first she did not speak Italian well, and Segrè and Spiro conversed in German, in which he was fluent.[14] The two were married at theGreat Synagogue of Rome on 2 February 1936. He agreed with the rabbi to spend the minimal amount on the wedding, giving the balance of what would be spent on a luxury wedding to Jewish refugees from Germany. The rabbi managed to give them many of the trappings of a luxury wedding anyway.[15] The couple had three children: Claudio, born in 1937, Amelia Gertrude Allegra, born in 1942, and Fausta Irene, born in 1945.[16]
After marrying, Segrè sought a stable job and became professor of physics and director of the Physics Institute at theUniversity of Palermo. He found the equipment there primitive and the library bereft of modern physics literature, but his colleagues at Palermo included the mathematiciansMichele Cipolla andMichele De Franchis, the mineralogistCarlo Perrier and the botanistLuigi Montemartini [it].[17] In 1936 he paid a visit toErnest O. Lawrence'sBerkeley Radiation Laboratory, where he metEdwin McMillan,Donald Cooksey,Franz Kurie,Philip Abelson andRobert Oppenheimer. Segrè was intrigued by the radioactive scrap metal that had once been part of the laboratory'scyclotron. In Palermo, this was found to contain a number of radioactiveisotopes. In February 1937, Lawrence sent him amolybdenum strip that was emitting anomalous forms ofradioactivity. Segrè enlisted Perrier's help to subject the strip to careful chemical and theoretical analysis, and they were able to prove that some of the radiation was being produced by a previously unknown element.[18] In 1947 they named ittechnetium, as it was the first artificially synthesizedchemical element.[19][20]
In June 1938, Segrè paid a summer visit toCalifornia to study the short-lived isotopes of technetium, which did not survive being mailed to Italy. While Segrè was en route,Benito Mussolini'sfascist government passedracial laws barring Jews from university positions. As a Jew, Segrè was now rendered an indefinite émigré.[21] TheCzechoslovak crisis prompted Segrè to send for Elfriede and Claudio, as he now feared that war in Europe was inevitable.[22] In November 1938 and February 1939 they made quick trips to Mexico to exchange their tourist visas for immigration visa. Both Segrè and Elfriede held grave fears for the fate of their parents in Italy and Germany.[23]
At the Berkeley Radiation Lab, Lawrence offered Segrè a job as a research assistant—a relatively lowly position for someone who had discovered an element—forUS$300 (equivalent to $6,800 in 2024) a month for six months. When Lawrence learned that Segrè was legally trapped in California, he took advantage of the situation to reduce Segrè's salary to $116 a month.[24][25] Working withGlenn Seaborg, Segrè isolated themetastable isotopetechnetium-99m. Its properties made it ideal for use innuclear medicine, and it is now used in about 10 million medical diagnostic procedures annually.[26] Segrè went looking forelement 93, but did not find it, as he was looking for an element chemically akin torhenium instead of arare-earth element, which is what element 93 was.[27] Working withAlexander Langsdorf, Jr., andChien-Shiung Wu, he discoveredxenon-135,[28][29] which later became important as anuclear poison innuclear reactors.[30]
The Japaneseattack on Pearl Harbor in December 1941 and the subsequentUnited States declaration of war upon Italy rendered Segrè anenemy alien and cut him off from communication with his parents. Physicists began leaving the Radiation Laboratory to do war work, andRaymond T. Birge asked him to teach classes to the remaining students. This provided a useful supplement to Segrè's income, and he established important friendships and professional associations with some of these students, who includedOwen Chamberlain andClyde Wiegand.[36]
In late 1942, Oppenheimer asked Segrè to join theManhattan Project at itsLos Alamos Laboratory.[37] Segrè became the head of the laboratory's P-5 (Radioactivity) Group, which formed part ofRobert Bacher's P (Experimental Physics) Division.[38] For security reasons, he was given the cover name of Earl Seaman.[39] He moved to Los Alamos with his family in June 1943.[40]
Segrè's group set up its equipment in a disusedForest Service cabin in the Pajarito Canyon near Los Alamos in August 1943.[41] His group's task was to measure and catalog the radioactivity of variousfission products. An important line of research was determining the degree ofisotope enrichment achieved with various samples ofenriched uranium. Initially, the tests usingmass spectrometry, used byColumbia University, and neutron assay, used by Berkeley, gave different results. Segrè studied Berkeley's results and could find no error, whileKenneth Bainbridge likewise found no fault with New York's. However, analysis of another sample showed close agreement.[42] Higher rates of spontaneous fission were observed at Los Alamos, which Segrè's group concluded were due tocosmic rays, which were more prevalent at Los Alamos due to its high altitude.[41]
The group measured the activity ofthorium,uranium-234,uranium-235 anduranium-238, but only had access tomicrogram quantities ofplutonium-239.[41] The first sample plutonium produced in thenuclear reactor atOak Ridge was received in April 1944. Within days the group observed five times the rate ofspontaneous fission as with the cyclotron-produced plutonium.[43] This was not news that the leaders of the project wanted to hear. It meant thatThin Man, the proposed plutoniumgun-type nuclear weapon, would not work and implied that the project's investment in plutonium production facilities at theHanford Site was wasted. Segrè's group carefully checked their results and concluded that the increased activity was due to theplutonium-240 isotope.[44]
In June 1944, Segrè was summoned into Oppenheimer's office and informed that while his father was safe, his mother had been rounded up by the Nazis in October 1943. Segrè never saw either of his parents again. His father died in Rome in October 1944.[45] In late 1944, Segrè and Elfriede becamenaturalized citizens of the United States.[46] His group, now designated R-4, was given responsibility for measuring thegamma radiation from theTrinity nuclear test in July 1945.[47] The blast damaged or destroyed most of the experiments, but enough data was recovered to measure the gamma rays.[48]
In August 1945, a few days before thesurrender of Japan and the end ofWorld War II, Segrè received an offer fromWashington University in St. Louis of an associate professorship with a salary ofUS$5,000 (equivalent to $87,300 in 2024). The following month, theUniversity of Chicago also made him an offer. After some prompting, Birge offered $6,500 and a full professorship, which Segrè decided to accept. He left Los Alamos in January 1946 and returned to Berkeley.[49][50]
In the late 1940s, many academics left the University of California, lured away by higher-salary offers and by the university's peculiarloyalty oath requirement. Segrè chose to take the oath and stay, but this did not allay suspicions about his loyalty.Luis Alvarez was incensed that Amaldi, Fermi,Pontecorvo, Rasetti and Segrè had chosen to pursuepatent claims against the United States for their pre-war discoveries and told Segrè to let him know when Pontecorvo wrote from Russia. He also clashed with Lawrence over the latter's plan to create a rival nuclear-weapons laboratory to Los Alamos inLivermore, California, in order to develop thehydrogen bomb, a weapon that Segrè felt would be of dubious utility.[51]
Unhappy with his deteriorating relationships with his colleagues and with the poisonous political atmosphere at Berkeley caused by the loyalty oath controversy, Segrè accepted a job offer from theUniversity of Illinois at Urbana–Champaign.[51] The courts ultimately resolved the patent claims in the Italian scientists' favour in 1953, awarding themUS$400,000 (equivalent to $4,700,000 in 2024) for the patents related to generating neutrons, which worked out to about $20,000 after legal costs. Kennedy, Seaborg, Wahl and Segrè were subsequently awarded the same amount for their discovery of plutonium, which came to $100,000 after being divided four ways, there being no legal fees this time.[52]
After turning down offers fromIBM and theBrookhaven National Laboratory, Segrè returned to Berkeley in 1952.[53] He was elected to the United StatesNational Academy of Sciences that same year.[54] He moved his family from Berkeley to nearbyLafayette, California, in 1955.[55] Working with Chamberlain and others, he began searching for theantiproton, asubatomicantiparticle of theproton.[56] The antiparticle of the electron, thepositron had been predicted byPaul Dirac in 1931[57] and then discovered byCarl D. Anderson in 1932.[58] By analogy, it was now expected that there would be an antiparticle corresponding to the proton, but no one had found one, and even in 1955 some scientists doubted that it existed.[59] Using Lawrence'sBevatron set to 6 GeV, they managed to detect conclusive evidence of antiprotons.[56][60] Chamberlain and Segrè were awarded the 1959Nobel Prize in Physics for their discovery.[61] This was controversial, becauseClyde Wiegand andThomas Ypsilantis were co-authors of the same article, but did not share the prize.[62]
Segrè served on the university's powerful Budget Committee from 1961 to 1965 and was chairman of the Physics Department from 1965 to 1966. He supported Teller's successful bid to separate theLawrence Berkeley Laboratory from theLawrence Livermore Laboratory in 1970.[63] He was elected to theAmerican Philosophical Society in 1963.[64] He was one of the trustees ofFermilab from 1965 to 1968. He attended its inauguration withLaura Fermi in 1974.[65] During the 1950s, Segrè edited Fermi's papers. He later published a biography of Fermi,Enrico Fermi: Physicist (1970). He published his own lecture notes asFrom X-rays to Quarks: Modern Physicists and Their Discoveries (1980) andFrom Falling Bodies to Radio Waves: Classical Physicists and Their Discoveries (1984). He also edited theAnnual Review of Nuclear and Particle Science from 1958 to 1977 and wrote an autobiography,A Mind Always in Motion (1993), which was published posthumously.[66][63]
Elfriede died in October 1970, and Segrè married Rosa Mines in February 1972.[16] He was elected to theAmerican Academy of Arts and Sciences in 1973.[67] That year he reached the University of California's compulsory retirement age. He continued teaching the history of physics.[68] In 1974 he returned to the University of Rome as a professor, but served only a year before reaching the mandatory retirement age.[63] Segrè died from aheart attack at the age of 84 while out walking near his home in Lafayette.[69] Active as aphotographer, Segrè took many photos documenting events and people in the history of modern science. After his death Rosa donated many of his photographs to theAmerican Institute of Physics, which named its photographic archive of physics history in his honor. The collection was bolstered by a subsequent bequest from Rosa after her death from an accident in Tivoli in 1997.[63][70][16]
Hawkins, David (1961).Manhattan District History: Project Y – The Los Alamos Project. Volume I: Inception until August 1945.Los Alamos National Laboratory. LAMS 2532.
