Emilio Segrè

Emilio Gino Segrè's scientific journey began in Rome, Italy, where he initially pursued engineering before transitioning to physics in 1927. His early career was marked by his association with the esteemed 'Via Panisperna boys,' a group of brilliant young physicists at the University of Rome, including Enrico Fermi. Segrè served as an assistant professor from 1932 to 1936, contributing to the vibrant intellectual atmosphere of the time.

His directorship of the Physics Laboratory at the University of Palermo followed, further solidifying his research credentials. This foundational period in Italy equipped him with the rigorous experimental and theoretical skills that would enable his later, world-altering discoveries. His early work laid the groundwork for understanding nuclear processes and the fundamental constituents of matter.

A transformative encounter occurred during a visit to Ernest O. Lawrence's Berkeley Radiation Laboratory. In 1937, Segrè received a molybdenum sample from the lab's cyclotron, exhibiting anomalous radioactivity.

Through painstaking radiochemical analysis and theoretical interpretation, he definitively identified the presence of a new element, which he named technetium (Tc). This was a landmark achievement, as technetium became the first element to be artificially synthesized, proving that the periodic table was not a static list but could be expanded through human ingenuity. His involvement continued with the discovery of astatine (At) while working at Berkeley.

These discoveries fundamentally altered chemists' and physicists' understanding of matter and the potential for creating new substances.

Segrè's life took a dramatic turn in 1938 when Italy's fascist regime enacted antisemitic racial laws. As a Jew, Segrè was barred from academic positions, rendering him an indefinite émigré. He found refuge and continued his research at the Berkeley Radiation Laboratory, initially in a less-than-ideal position.

During this challenging period, he also contributed to the identification of plutonium-239, an isotope that would become crucial for nuclear weapons. From 1943 to 1946, he served as a group leader in the Manhattan Project at Los Alamos, a critical role in the development of the atomic bomb. His sharp analysis in April 1944 identified that plutonium-240 impurities would render the proposed 'Thin Man' gun-type weapon ineffective, necessitating a shift in design strategy.

Following his naturalization as a U.S. citizen in 1944, Segrè returned to Berkeley, eventually becoming a professor of physics and the history of science. His most celebrated achievement came in collaboration with Owen Chamberlain. Leading a research group at the Lawrence Radiation Laboratory, they experimentally discovered the antiproton, the antiparticle of the proton, in 1955.

This discovery provided crucial experimental validation for the existence of antimatter, a concept previously explored theoretically. For this profound contribution, Segrè and Chamberlain were jointly awarded the 1959 Nobel Prize in Physics. Beyond his Nobel-winning work, Segrè was an avid photographer, meticulously documenting the personalities and events that shaped 20th-century physics, leaving behind an invaluable visual archive for future generations.