Congress of 1931
The First Congress of Nuclear Physics
Between the end of the 1920s and the beginning of the 1930s, nuclear physics was an almost completely new field of research in Rome. The first works in this field were limited to Ettore Majorana’s degree thesis, which was one of the first applications of quantum mechanics to nuclear physics in Italy, which gave a rigorous mathematical justification for the phenomenon of α-decay given by George Gamow in 1928, and to some works by Enrico Fermi, which were however linked to the previous line of research in atomic physics. Apart from these results, which had a certain international resonance, Fermi’s name became famous in the nuclear field when he became secretary general of the first International Congress of Nuclear Physics, organized by the Volta Foundation and held from 11 to 18 October 1931 at the Institute of Physics of the Royal University of Rome. According to the organisers, the need for further study of the nucleus was linked to two issues: the complete development of quantum mechanics, which could provide a tool for the theoretical understanding of nuclear phenomena, and the consolidation of the study of artificial transmutations of elements, a line of research inaugurated in 1919 by Ernest Rutherford. The title chosen was “Nuclei and Electrons”.
The most influential physicists of the time, such as Niels Bohr, Marie Curie and Warner Heisenberg, were invited to Rome. Out of 50 participants, seven Nobel Laureates plus many future winners were present. The Congress was organised into six lectures, which were to provide the impetus for a series of long and fruitful discussions. The topics had been chosen by the organisers to take stock of the situation, with particular attention paid to open problems. The only Italian invited to speak was Bruno Rossi, who in those years was the protagonist of important studies on cosmic rays (and who would establish himself as a true expert in this field), inventing an instrument that acquired great importance.
The topics covered were varied, but the interests centred on two major issues. The first concerned the atomic nucleus, which at that time was thought to consist of electrons and protons. The second issue concerned the theoretical explanation of β decay. Orso Mario Corbino, Acting President of the Congress, in his closing speech, expressed his thoughts on the positive effect that the week that had just passed could have on the international scientific community. Corbino’s predictions would come true a few years later when new and important discoveries were announced, such as the neutron, the positron, the Heisenberg–Majorana nuclear theory and the theory of β decay by Fermi himself.
Franco Rasetti was born in Pozzuolo Umbro in 1901. His father held an itinerant chair of agriculture at the University of Pisa (a sort of itinerant teaching mostly aimed at landowners) and specialised in chemistry, botany and entomology. Rasetti became interested in entomology at an early age, enriching his father’s already extensive collection, and together they also published an article in a specialised bulletin. His uncle, a well-known professor of pathology, also exerted a great influence on him, even getting him interested in mountain excursions, a passion he later shared with Fermi and the entire Via Panisperna group. He did not attend primary school because he was a precocious child: At the age of three he was already trying his hand at drawing and reading. At the age of seven he could distinguish the main families of insects and knew hundreds of scientific names by heart. After graduating from high school, he enrolled in the two-year preparatory engineering course at the University of Pisa. There he met Enrico Fermi and an immediate friendship developed between them. Rasetti repeatedly said that he learned much more physics from Fermi than from his professors.
Having completed the two-year course, he switched to physics, which at that time had only three students enrolled in the faculty. In Pisa there was Luigi Puccianti, director of the physics laboratory, who had the merit of giving students great freedom, providing them with all the material and even the keys to the libraries. In Puccianti, Rasetti found a guide who directed him towards spectroscopy, a field of research in which years later he would become a true expert. After a short period in Florence, he was called by Orso Mario Corbino to the Institute of Physics in Rome where Fermi had obtained one of the first three chairs of theoretical physics in Italy. He also spent a year at the California Institute of Technology, where he specialised: thanks to his measurements, the then version of the atomic model, consisting of protons and electrons, began to be questioned. In 1927 he was again called by Corbino to Rome to work to work alongside Fermi. Only a year later, he won a scholarship to Germany, where he studied the latest techniques in the preparation of radioactive sources and their detection with the leading scientists in this field.
When he returned to Rome, he used all the experience he had accumulated for the study of the nuclear physics, making substantial and fundamental contributions to the entire experimental part of the Institute of Physics, both in studies on atomic structure and in the discovery of slow neutrons and the radioactivity induced by them. In fact, while Fermi was known as “the Pope”, Rasetti was nicknamed “the Cardinal”. After the promulgation of racial laws in 1938, Rasetti decided to emigrate accepting a position at the University of Quebec in Canada, where he built from scratch an entire laboratory for cosmic ray physics. But it was in September ’42 that Rasetti stopped collaborating, for ethical reasons, with the scientists involved in the development of nuclear energy for military purposes in the famous Manhattan Project at Los Alamos.
After the war, Rasetti completely detached himself from physics, focusing exclusively on botany and palaeontology at Johns Hopkins University in Baltimore, where he remained for more than 20 years. At the same time, he developed a passion for nature photography, combined with a passion for mountains and mountaineering that never left him. At the end of his biography, he wrote:
“I am well aware that geology and palaeontology do not have the high rank of physics in the hierarchy of the creations of the human intellect. I appreciate the supreme aesthetic value of general relativity and quantum mechanics, and I admire the human minds that have managed to express an infinity of phenomena in a few elegant mathematical equations. In contrast, reconstructing the history of the earth and the evolution of life requires an immense mass of patient observations. For me, however, the contemplation of the wonders of nature, a mountain, a flower, an insect, a fossil, gave me no less pleasure than admiring the creations of our physical and mathematical minds.”
Franco Rasetti died at the age of 100 on 5 December 2001.
Edoardo Amaldi, born in Carpineto Piacentino on 5 September 1908. His father, Ugo, was a mathematician and university lecturer in mathematical analysis and rational mechanics. His first contact with Enrico Fermi, a former professor in Florence, took place in 1925, when the whole Amaldi family was on holiday in the Dolomites, a popular destination for Italian mathematicians and physicists at the time. During his long walks along the trails, the young Edward had the opportunity to talk to some of the leading theoretical physicists who were spending their summer holidays in the same area. It was here that his first interest in physics began.
However, he decided to enroll in the Faculty of Engineering in Rome. But, in 1927, he accepted an appeal from the director of the Via Panisperna Institute, Orso Mario Corbino: All students interested in studying pure physics were asked to change to a degree course in physics. Amaldi accepted and found himself participating actively in the research group of the “Ragazzi di Via Panisperna” where he found himself mentored by Enrico Fermi and Franco Rasetti. But he was not the only one to change faculty, as the group had already been enriched by the presence of Emilio Segrè and Ettore Majorana. Amaldi formed a special bond with the latter.
Amaldi graduated with Rasetti as supervisor in July 1929, the same day as Majorana, with a thesis on the Raman effect, a material analysis technique based on the phenomenon of the diffusion of electromagnetic radiation scattered from the element analysed. Immediately after his military service, he went to Leipzig to study under Peter Debye, where he worked on X-ray diffraction. He then returned to Rome as Corbino’s assistant, where he first worked on spectroscopy and then immersed himself completely in the investigation of radioactive phenomena with the entire Via Panisperna group.
In 1938 the Via Panisperna group broke up. In 1937 Amaldi became the holder of the chair of general and experimental physics at La Sapienza University in Rome, succeeding Corbino after his death. He held this position for 41 years. In 1940 he was called up for military service and transferred to Africa, but the University of Rome managed to get him back after six months. He stopped his research on fission, for fear that it might be exploited by the Axis, and his research in nuclear physics focused on the study of proton–neutron interaction.
After the war he worked hard to rebuild the Italian scientific environment, making important international agreements and becoming a leading figure in the creation of national research centres, such as the National Laboratories at Frascati. It was at Frascati that he attracted a number of foreign physicists, including Bruno Touschek, who laid the theoretical foundations for the construction of a matter–antimatter accelerator machine AdA (Accumulation Ring). In 1952 he made a personal contribution to the construction of the European Nuclear Research Centre (CERN) in Geneva, becoming its Secretary General. His social and political commitment was also notable: A staunch supporter of nuclear disarmament, he created the Commission for Civil Rights and the Working Group on International Security and Arms Control (SICA) at the Accademia dei Lincei. The author of some 200 scientific publications and manuals on general physics, he received numerous honours and awards of all kinds. His incredible qualities as a teacher, his absolute availability and his great clarity of exposition must be remembered. Despite his many institutional commitments, Amaldi never gave up teaching and trained entire generations of physicists, moving from pioneering research in nuclear physics to the emerging physics of particles and cosmic rays.