Franco Rasetti

Franco Rasetti, the last survivor of Enrico Fermi’s “the boys of Via Panisperna,” died of natural causes on 5 December 2001 in Waremme, Belgium, where he lived from 1977 until a few months after his 100th birthday.

Rasetti was born on 10 August 1901 in Pozzuolo Umbro, a small village not far from Perugia in central Italy. As a young boy, he developed a particular inclination toward the natural sciences, thanks to a family background in which scientific interests were widely represented and cultivated. Rasetti’s uncle, Gino Galeotti, a distinguished professor of pathology in Turin, was instrumental in developing those interests.

In 1918, Rasetti enrolled in engineering at the University of Pisa, where he met Enrico Fermi. Primarily because of the influence of his new friend, he decided to switch his major to physics. As Rasetti once said, “I learned from him far more physics than I did from the professors.” He received his PhD in physics in 1922. His doctoral thesis, prepared under the supervision of Luigi Puccianti, a prominent figure of Italian physics in the field of spectroscopy, was on the anomalous dispersion in alkali-metal vapors.

In 1927, after spending a few years as an assistant to director Antonio Garbasso at the physics institute of the University of Florence, Rasetti was invited by Orso Mario Corbino to join the physics institute on the Via Panisperna in Rome, where Corbino was director. Fermi had just been named as the Rome institute’s chair of theoretical physics—the first-ever chair of theoretical physics at any Italian university. Rasetti spent the 1928–29 academic year at Caltech under a Rockefeller Foundation grant. There, he completed his first important work: studying the newly discovered Raman effect in gases. In particular, his results on the nitrogen spectrum showed that the ¹⁴N nucleus was a boson and forced a revision of the prevailing nucleus model that was based on the existence of nuclear electrons. The solution to the problem came later (in 1932) with the discovery of the neutron. While Rasetti was at Caltech, Corbino had managed to create a chair for spectroscopy at the institute in Rome; Rasetti won the competition for that chair in 1930.

By the early 1930s, Fermi’s Rome group was moving from spectroscopy to nuclear physics. Rasetti’s experimental skills proved of vital importance in work that led Fermi and his group, between March and October of 1934, to the discovery of neutron-induced radioactivity and of the unexpected properties of slow neutrons. Rasetti had become the group expert in the preparation of radioactive sources and, on another Rockefeller fellowship, spent 1931–32 learning radioactive techniques under Lise Meitner at the Kaiser Wilhelm Institute for Chemistry outside Berlin.

Rasetti traveled again in 1935 to spend a year at Columbia University, where he worked on slow neutron resonances and taught at Cornell University’s summer school. On his return to Italy, he found a deteriorating environment; as he put it, “Fascism was rapidly turning from the nuisance it had represented up to that time to a tyranny affecting our everyday lives.” When the racial laws promulgated in 1938 forced most of his friends and colleagues to emigrate, Rasetti could no longer find good reasons to stay in Italy and started looking for a position abroad.

In 1939, he accepted an invitation from the Université Laval in Quebec City, Canada, where a science faculty had just been created, to head the new physics department. In a matter of months, Rasetti transformed the two-room department into a modern laboratory. There, he resumed work on slow neutrons, and, in 1941, he turned to cosmic-ray research. He single-handedly built more than 60 Geiger–Müller counters and the electronic circuits by which he was the first to roughly measure the lifetime of the muon—what was then called the mesotron.

Like his spectroscopic work at Caltech, Rasetti’s research on the lifetime of the muon illustrates his style of doing physics: a single, skilled researcher who performed experiments in splendid isolation, shunned large cooperative enterprises, and focused on one project until he had completely mastered it. Not surprisingly then, Rasetti did not look forward to the prospect of being involved in military research during World War II. His dislike for large, controlled enterprises coupled with his ethical objections to the use of science for destructive purposes led him to refuse an offer in early 1943 to take a position with a group of British scientists who had been transferred from England to Montreal and were working on the military use of nuclear energy. As Rasetti later noted, “There are few decisions I ever made in my life that I had less reason to regret.”

Following the war, as physics moved toward the “big science” complex, Rasetti began seeking out work that would fit his styles and rhythms. While at Laval, he resumed his old interest in the Earth sciences, collecting trilobites. That interest soon evolved from a marginal pastime to a full-time endeavor, and he quickly became remarkably competent in paleontology. In 1947, he left Laval for a more attractive professorship in physics at Johns Hopkins University. However, his physics research was reduced to a minimum in the years that followed while he focused almost exclusively on geology and paleontology. His contributions to those fields earned him a reputation in scientific circles comparable to that already earned by his accomplishments in nuclear physics.

Rasetti kept doing fieldwork for a long time after retirement, climbing hills, collecting fossils and flowers, and contributing in various ways to different branches of the natural sciences. A born naturalist-turned-physicist almost by chance, he returned in his later years to that kind of scientific practice—individualistic, free from constraints, and feasible with limited means—that, as he said, could still be found in the natural sciences and that he felt physics had lost. Nonetheless, in the wake of Rasetti’s relatively short trajectory in physics are some of the more remarkable experimental results of the 20th century. Rasetti’s work is a splendid testimony of a style of research that, although by now may be lost, is so much more worth remembering.