Emilio Segrè

Emilio Gino Segrè (1 February 1905 – 22 April 1989) was an Italian-American physicist and Nobel laureate, who discovered the elements technetium and astatine, and the antiproton, a subatomic antiparticle, for which he was awarded the Nobel Prize in Physics in 1959 along with Owen Chamberlain.

Born in Tivoli, near Rome, Segrè studied engineering at the University 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 the Via Panisperna boys. From 1936 to 1938 he was director of the Physics Laboratory at the University of Palermo. After a visit to Ernest O. Lawrence's Berkeley Radiation Laboratory, he was sent a molybdenum strip from the laboratory's cyclotron accelerator in 1937, which was emitting anomalous forms of radioactivity. After 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, which was the first artificially synthesized chemical element that does not occur in nature.

In 1938, Benito Mussolini's fascist government passed antisemitic laws barring Jews from university positions. As a Jew, Segrè was now rendered an indefinite émigré. At the Berkeley Radiation Lab, Lawrence offered him a job as a research assistant. While at Berkeley, Segrè helped discover the element astatine and the isotope plutonium-239, which was later used to make the Fat Man nuclear bomb dropped on Nagasaki. From 1943 to 1946 he worked at the Los Alamos National Laboratory as a group leader for the Manhattan Project. He found in April 1944 that Thin Man, the proposed plutonium gun-type nuclear weapon, would not work because of the presence of plutonium-240 impurities. In 1944, he became a naturalized citizen of the United States. On his return to Berkeley in 1946, he became a professor of physics and of history of science, serving until 1972. Segrè and Owen Chamberlain were co-heads of a research group at the Lawrence Radiation Laboratory that discovered the antiproton, for which the two shared the 1959 Nobel Prize in Physics.

Segrè was also active as a photographer and took many photographs documenting events and people in the history of modern science, which were donated to the American Institute of Physics after his death. The American Institute of Physics named its photographic archive of physics history in his honor.

Early life

Emilio Gino Segrè was born into a Sephardic Jewish family in Tivoli, near Rome, 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. His uncle, Gino Segrè, was a law professor. He was educated at the '' ginnasio'' in Tivoli and, after the family moved to Rome in 1917, the ''ginnasio'' and '' liceo'' in Rome. He graduated in July 1922 and enrolled in the University of Rome La Sapienza as an engineering student.

In 1927, Segrè met Franco Rasetti, who introduced him to Enrico Fermi. The two young physics professors were looking for talented students. They attended the Volta Conference at Como in September 1927, where Segrè heard lectures from notable physicists including Niels Bohr, Werner Heisenberg, Robert Millikan, Wolfgang Pauli, Max Planck and Ernest Rutherford. Segrè then joined Fermi and Rasetti at their laboratory in Rome. With the help of the director of the Institute of Physics, Orso Mario Corbino, Segrè was able to transfer to physics, and, studying under Fermi, earned his laurea degree in July 1928, with a thesis on "Anomalous Dispersion and Magnetic Rotation".

After a stint in the Italian Army from 1928 to 1929, during which he was a commissioned as a second lieutenant in the antiaircraft artillery, 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 with Edoardo Amaldi in 1928, and another article with him the following year on the Raman effect.

In 1930, Segrè began studying the Zeeman effect in certain alkaline metals. When his progress stalled because the diffraction grating he required to continue was not available in Italy, he wrote to four laboratories elsewhere in Europe asking for assistance and received an invitation from Pieter Zeeman to finish his work at Zeeman's laboratory in Amsterdam. Segrè was awarded a Rockefeller Foundation fellowship and, on Fermi's advice, elected to use it to study under Otto Stern in Hamburg. Working with Otto Frisch on space quantization produced results that apparently did not agree with the current theory; but Isidor Isaac Rabi showed that theory and experiment were in agreement if the nuclear spin of potassium was +1/2.

Physics professor

Segrè was appointed assistant professor of physics at the University of Rome in 1932 and worked there until 1936, becoming one of the Via Panisperna boys. In 1934, he met Elfriede Spiro, a Jewish woman whose family had come from Ostrowo in West Prussia, but had fled to Breslau when that part of Prussia became part of Poland after World War I. After the Nazi 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. The two were married at the Great 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. The couple had three children: Claudio, born in 1937, Amelia Gertrude Allegra, born in 1937, and Fausta Irene, born in 1945.

After marrying, Segrè sought a stable job and became professor of physics and director of the Physics Institute at the University of Palermo. He found the equipment there primitive and the library bereft of modern physics literature, but his colleagues at Palermo included the mathematicians Michele Cipolla and Michele De Franchis, the mineralogist Carlo Perrier and the botanist . In 1936 he paid a visit to Ernest O. Lawrence's Berkeley Radiation Laboratory, where he met Edwin McMillan, Donald Cooksey, Franz Kurie, Philip Abelson and Robert Oppenheimer. Segrè was intrigued by the radioactive scrap metal that had once been part of the laboratory's cyclotron. In Palermo, this was found to contain a number of radioactive isotopes. In February 1937, Lawrence sent him a molybdenum strip that was emitting anomalous forms of radioactivity. 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. In 1947 they named it technetium, as it was the first artificially synthesized chemical element.

Radiation Laboratory

In June 1938, Segrè paid a summer visit to California to study the short-lived isotopes of technetium, which did not survive being mailed to Italy. While Segrè was en route, Benito Mussolini's fascist government passed racial laws barring Jews from university positions. As a Jew, Segrè was now rendered an indefinite émigré. The Czechoslovakian crisis prompted Segrè to send for Elfriede and Claudio, as he now feared that war in Europe was inevitable. 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.

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—for 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. Working with Glenn Seaborg, Segrè isolated the metastable isotope technetium-99m. Its properties made it ideal for use in nuclear medicine, and it is now used in about 10 million medical diagnostic procedures annually. Segrè went looking for element 93, but did not find it, as he was looking for an element chemically akin to rhenium instead of a rare-earth element, which is what element 93 was. Working with Alexander Langsdorf, Jr., and Chien-Shiung Wu, he discovered xenon-135, which later became important as a nuclear poison in nuclear reactors.

Segrè then turned his attention to another missing element on the periodic table, element 85. After he announced how he intended to create it by bombarding bismuth-209 with alpha particles at a Monday meeting Radiation Laboratory meeting, two of his colleagues, Dale R. Corson and Robert A. Cornog carried out his proposed experiment. Segrè then asked whether he could do the chemistry and, with Kenneth Ross MacKenzie, successfully isolated the new element, which is today called astatine. Segrè and Wu then attempted to find the last remaining missing non- transuranic element, element 61. They had the correct technique for making it, but lacked the chemical methods to separate it. He also worked with Seaborg, McMillan, Joseph W. Kennedy and Arthur C. Wahl

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