by Gino Segrè
The Boys were, however, cautious in making their claim because of the stir that finding the first transuranic would cause. Corbino had no such hesitation. He wanted to let Italy know what the Boys had accomplished. He soon found a way to do so. The academic year at the Accademia dei Lincei was always brought to a close with a ceremony during which a member would give a formal address on a subject in his or her specialty. The honor in 1934 fell on Corbino; the topic he selected was “Results and Perspectives of Modern Physics.”
On June 4, addressing his fellow Lincei members and King Victor Emmanuel III, who regularly attended the event, Corbino voiced his view of the new element, saying, “The investigation is so delicate that it justifies Fermi’s prudent reserve and a continuation of the experiment before the announcement of the discovery. For what my own opinion on this matter is worth, and I have followed the investigations daily, I believe that the production of this new element is certain.” The press, always on the lookout for a good story, found this one ideal.
With great fanfare, Italian newspapers trumpeted the discovery. The press, by now largely a tool of state propaganda, opined on how magnificently science flourished under Fascism. Some journalists even speculated that the new element should be named Mussolinium. One publication alleged that Fermi had given a vial of element 93 to the Queen of Italy. The international press struck a somewhat more skeptical tone, though the New York Times did print a two-column article under the banner headline ITALIAN PRODUCES 93RD ELEMENT BY BOMBARDING URANIUM.
Fermi did not share Corbino’s certainty. He knew how easy it was to be wrong in making a science claim. Laura remembered being woken in the middle of the night by her normally sound-sleeping husband, torn about what to do. He felt his reputation was at stake. She advised him to speak to Corbino in the morning and see how they could address the situation. Subsequently a joint press release was issued, stating clearly that the announcement of a ninety-third element was preliminary. The disclaimer began with “The public is giving an incorrect interpretation … to Senator Corbino’s speech” and ended with “the principal purpose of this research is not to produce a new element, but to study the general phenomenon.” To counteract the overblown press coverage, Fermi also sent Nature a letter detailing the lingering uncertainties. At the very least, Fermi wanted to alert his science colleagues that he harbored doubts.
Aware that physicists everywhere were closely scrutinizing their publications, the Boys pursued their analyses at a feverish pace, checking and rechecking all their results. By mid-July they were ready to assert with greater certainty that they had observed element 93. Via Panispera, like other Rome laboratories, closed for vacation in August. The Fermis usually scheduled a summer vacation unless Enrico was teaching at the University of Michigan summer school or somewhere else. Fermi’s penchant for working long hours was not always easy on Laura, and getting away was high on her agenda. The Dolomites, where they had met almost a decade earlier, certainly held a special place in their heart, but in August 1935 a stay there would have been less relaxing because of considerable political tensions along the Italian-Austrian border.
Although there were strategic strains with Austria, relations between Italy and Germany were getting cozier. Two months earlier, on his first trip outside Germany or Austria since becoming Chancellor, Hitler had flown to Venice to meet with Mussolini. His German counterpart had not impressed Il Duce. Mussolini possessed, or so he thought, an imposing physique, whereas his visitor seemed pale and thin. Above all, Mussolini viewed himself as an established world leader dealing with an upstart aspiring to follow in his formidable footsteps. Hitler did indeed follow in those footsteps; six weeks after the visit he added the title of Führer, the German translation of Duce, to his designation as Chancellor.
The Fermis heard very little about this since they were en route to Argentina, Uruguay, and Brazil; interest in the new physics was high, and the large Italian colonies in South America desired to hear from a prominent citizen of their homeland. Fermi anticipated there would be lots to do in Rome during the fall, but he felt this excursion, almost two months long, would give him respite from work and be enjoyable for him and Laura.
They left their three-year-old daughter, Nella, in the care of a nursemaid at the home of Laura’s relatives, and the trip had the feel of a deluxe second honeymoon for Enrico and Laura. The Fermis were berthed on a luxury liner during the sixteen-day ocean voyage from Naples to Buenos Aires. Everything about the trip was first class, the ship and hotel accommodations, the dinners and welcoming parties. This was to be expected, because he was, after all, Sua Eccellenza Fermi.
On the return voyage the Fermis had as shipmates another Academician and his wife. Ottorino Respighi, the composer of Fountains of Rome and other symphonic pieces, tried to have Fermi share in the joys of music, and in return Fermi tried to explain physics to Respighi. Neither succeeded, but a friendship was struck.
16
THE RISE AND FALL OF THE BOYS
While Fermi was returning from South America, a small change had taken place on Via Panisperna. Bruno Pontecorvo, a young Pisan from a large well-to-do assimilated Jewish family, had been added to the group. Hearing of Rasetti’s physics accomplishments, Pontecorvo had come to Rome to complete his thesis under the guidance of the fellow Pisan and family friend. Intelligent and gifted as an experimentalist, Pontecorvo became one of the Boys in the fall of 1934. As a mark of acceptance, he was given a nickname, Cucciolo (puppy dog).
Pontecorvo worked together with Amaldi in his first set of experiments as a member of the group. They derived a baffling result. Despite using the same target and the same source, the readings of induced radiation differed depending on whether the apparatus was placed on a wooden table or a marble one. Not understanding the inconsistency, Rasetti tried doing the experiments on his own. He obtained the same results Amaldi and Pontecorvo had. Everybody was now confused.
On the twenty-second of October, just back from a London conference, Fermi decided to see if he could discover the cause of the discrepancy. While making final preparations for the experiment, Fermi uncharacteristically hesitated, and then reached for a block of paraffin. At the time paraffin wax was a typical supply in any well-stocked physics laboratory. Without pausing, he put a two-inch-thick slice of the paraffin between the neutron source and the target. He saw at once that this yielded a dramatic effect on the induced radioactivity. The counting rate shot up unimaginably, by a factor of a hundred or more. The rise was simply astonishing. Other members of the Via Panisperna team, alerted by the commotion, swiftly congregated. Their first reaction was that the counters must be broken. They were quickly disabused.
Shortly before one o’clock, Fermi announced it was time for lunch. As was usual in those pre-cafeteria days, Italians went home for a meal with the family. Since Laura and Nella were still with Capon relatives in Tuscany, Fermi had a light lunch by himself. He was happy to be left alone, to think about the morning’s experiment. At three o’clock, when the group reconvened, Fermi was ready with an explanation. But he could not help uttering, “What a stupid thing to have discovered this phenomenon without having known to foresee it.” Fermi said the difference in induced radioactivity was due to the neutrons in the beam being slowed down by hydrogen nuclei in the paraffin. When asked what ever possessed him to reach for the paraffin, Fermi gave them a response he often self-mockingly used when his interventions came out of the blue. He answered he had acted with “intuito fenomenale” (phenomenal intuition).
Fermi then told the group gathered around him that the neutrons probably had thousands of times less energy upon leaving the paraffin than they had upon entering. He continued his explanation, saying that less energy meant the neutrons were far more likely to be captured by the target’s nuclei. More captures meant more induced radioactivity. In addition, by moving slower, the neutrons would stay in the target longer, again increasing their chance of being captured.
Physicists had assumed that fas
ter projectiles produced an increase in induced radioactivity. That was true for alpha particles. The opposite was true for neutrons. When slowed, they became more efficient at inducing radioactivity. Fermi told the other Boys this also explained the difference they had observed between doing the experiment on wood and marble tables. Neutrons that bounced off the wood table and reached the target had been slowed down. Those reflected by the marble had not. If Fermi’s interpretation of how to increase radioactivity was correct, he added, water should have an effect similar to paraffin: they are both rich in hydrogen.
The simplest way to test this was to immerse the source and the target in a water tank. Although her account has been disputed, Laura maintained that the goldfish pond in back of the Institute was used to demonstrate this. She also added that the goldfish were unharmed, though perhaps disoriented by the strange presence in their waters. Whether the goldfish pond story is true or not, water’s effect on neutrons was quickly confirmed.
The Boys recognized the significance of their finding: induced radioactivity had entered a new phase. That same evening they gathered at the Amaldis’ house to write a report on their day’s work. This was the natural meeting place because Ginestra had taken a position at La Ricerca, the journal in which they were planning to publish their result. If they wrote quickly, she could deliver it the following morning to the journal’s offices. With Segrè acting as scribe, Fermi dictated the text; Ginestra’s husband, Rasetti, and Pontecorvo paced around the Amaldis’ living room shouting suggestions. Luckily the Amaldis’ two-month-old baby seems to have slept through it all. Laura later heard from Ginestra that the Amaldis’ maid, noting how exhilarated everybody was, had timidly inquired if they had been drinking.
The paper was written that evening. In a departure from the Boys’ custom of listing authors in alphabetical order on their publications, Fermi’s name was put first. It had been his discovery.
The technique discovered that October day would eventually also become a revenue source for the Boys. Upon hearing of the new discovery, Corbino told them it could radically accelerate the production of radioactive isotopes for medical purposes. He recommended they patent the procedure at once. They did so on October 26, 1934, four days after the first experiment. Amaldi, Fermi, Pontecorvo, Rasetti, and Segrè were listed as the five inventors. They agreed to divide any earnings from the patent seven ways, sharing them with Oscar D’Agostino and Giulio Trabacchi. Years later, after many hurdles, they would finally reap modest monetary rewards.
After the slow neutron surprise, the Boys’ research proceeded at such a rapid pace that by the middle of February 1935, they had prepared for publication a lengthy paper describing fully their findings of the previous year. In a change from past patterns, Fermi submitted the forty-page paper to the Proceedings of the Royal Society of London instead of to German journals.
With a regime denouncing Jewish physics and expelling the likes of Einstein, Germany was no longer the physics magnet it had once been. Its publications were less vital, its research in decline, and its influence on the wane. Fully cognizant of this, Fermi was experiencing a greater affinity with the Anglo-Saxon world, particularly the United States, a country that was becoming a great power in physics and where he felt comfortable and appreciated.
The paper’s eleventh section, the last and by far the longest, drew the most attention. It details, element by element, the Boys’ systematic investigation of radioactivity induced by slow neutrons. The impressive list, a chemist’s dream, is staggering in its thoroughness. A testament to how much work the Boys had done in just a few months, it impeccably records slow neutrons’ interaction with almost every element: hydrogen, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, potassium, calcium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, arsenic, selenium, bromine, strontium, yttrium, zirconium, niobium, rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium, iodine, barium, lanthanum, cerium, praseodymium, gadolinium, tantalum, tungsten, rhenium, iridium, platinum, gold, mercury, thallium, lead, bismuth, thorium, and finally uranium. Uranium was given the most exhaustive examination of all because of the importance of possibly having produced transuranics, elements 93 and beyond.
In section 11, the most telling paragraph comes near the end: it refers to research conducted in the Berlin laboratory of Otto Hahn and Lise Meitner. Aside from possibly Curie and Joliot, they were the world’s foremost chemist-physicist team and close attention was always given to their findings. Hahn and Meitner had confirmed the Boys’ observations regarding transuranics. The Boys were relieved.
Years later, they all would be proved wrong. The German chemist Ida Noddack had given what turned out to be the correct interpretation of the discovery of elements 93 and beyond. She suggested that the supposed transuranic might be the nucleus of an element that lay far down the periodic table, a fragment produced by the splitting of the uranium nucleus. Noddack criticized the Fermi group for basing their conclusions about transuranics on tests that had gone only a mere ten steps down the table from uranium.
The Boys dismissed her criticism, not even mentioning it in their paper. She had not conducted any analyses that might confirm her hypothesis. In addition, there was no physical theory in 1934 that would account for a nuclear splitting. There was also a touch of arrogance in the Boys’ attitude toward her: Noddack was a chemist. They probably assumed she would not have understood how improbable such a split appeared to be from a physicist’s point of view.
Hahn and Meitner also chose to ignore Noddack’s paper. Admittedly they were only saying “probably due to transuranic elements,” but that was also Fermi’s outlook. The presumed existence of transuranics was soon endorsed by Irène Curie in Paris and further confirmed by experimenters in Berkeley, Ann Arbor, Vienna, Cambridge, and Zurich. Their findings having been checked by others, there was solid evidence that the Via Panisperna group had detected element 94 as well.
This prompted the Boys to contemplate what to call elements 93 and 94. The common tradition was for those who had discovered new elements to associate their names with the place where they had been first observed. Mussolini’s advisers recommended littorium as a way of honoring the littori, a class of civil servants in ancient Rome who defended the supreme magistrate with fasces littori, weapons with thirty rods bound together and a protruding ax.
For their new element, the Boys did not want to adopt such a bellicose image, one frequently used as a symbol in Fascist propaganda. Corbino, with his keen sense of humor, told them that in any case the regime might not want to be linked to an element that decayed in minutes. Eventually, the Boys settled on Ausonium and Hesperium, Greek for Italy and for Land to the West.
The Proceedings paper, the apex of the Boys’ research, was also their swan song, the last one they wrote together. Their accomplishments would continue, but largely with other individuals and in other places. After less than ten years, the Boys of Via Panisperna would become a thing of the past.
Part of this was due to the natural migrations of scientists. The group, after such an intense and productive run, was ready to disperse. But there is no doubt that the unraveling took place against the backdrop of a grave political climate.
In early 1935, Il Duce had begun planning a military campaign against Ethiopia, the land-locked independent African state. Since Ethiopia was a member of the League of Nations, founded after World War I explicitly to prevent future wars, the invasion put a severe strain on Italy’s relations with its World War I allies, Britain and France. Mussolini was turning his back on Italy’s historic partners and drawing closer to Germany, a country that had already withdrawn from the League.
The Italian invasion of Ethiopia, begun in early October 1935, drew further international condemnation when the commander of Italy’s armed forces, Pietro Badoglio, ordered copious use of mustard gas. The Geneva Protocol had banned this weapon, an ear
ly example of science being used for corrupt purposes, after the devastation of World War I. Its renewed employment was widely met with opprobrium.
The sanctions imposed on Italy by the League were ineffective and victory in Ethiopia was declared on May 9, 1936. The League’s powerlessness had not been lost on Germany or Spain. It was becoming painfully clear that they, along with Italy, seemed to be preparing for war.
In the summer of 1935, Rasetti had decided to take a year’s leave of absence, opting to once again visit the United States. Segrè, recently married to a Jewish woman from Germany whom he met in Rome, also went to America that summer. Upset by the Italian political situation, he hoped to obtain a long-term position there. He did not succeed, but while in the United States he heard that he had been awarded a physics university professorship in Palermo, Sicily’s largest city. He had entered the competition for the post as a fallback position in case nothing materialized abroad. Rather reluctantly, Segrè set off for Palermo. D’Agostino accepted a chemistry appointment at a government bureau located elsewhere in Rome. Pontecorvo departed for a research position at the Paris institute headed by Curie and Joliot. At age twenty-four, he wanted to see more of the world. By the fall of 1935, Fermi and Amaldi were the only Boys left in Rome.
It was hard still for them to consider moving abroad, especially since both of their wives were reluctant. Nonetheless, they found themselves increasingly unhappy about the direction Italy was taking. The physicists, bastions of rationality, could not fathom Italy’s invasion of Ethiopia any more than they could justify Mussolini’s call to fund the war by having women trade their gold wedding rings for steel rings or bracelets. With patriotic pride, Laura had joined the exchange ritual of Oro alla Patria (Gold for the Fatherland). These maneuvers were dismissed as propagandistic, only fleetingly interrupting the rhythms of domestic and work life.