Bruno Pontecorvo

Bruno Pontecorvo
Bruno Pontecorvo in the 1950s
Born	22 August 1913 Marina di Pisa, Italy
Died	24 September 1993 (aged 80) Dubna, Moscow Oblast, Russia
Citizenship	Italy, Soviet Union
Alma mater	University of Rome La Sapienza
Known for	Neutrino oscillation
Scientific career
Fields	Nuclear physics
Academic advisors	Enrico Fermi

Bruno Pontecorvo (Russian: Бру́но Макси́мович Понтеко́рво, Bruno Maksimovich Pontecorvo; 22 August 1913 – 24 September 1993) was an Italian nuclear physicist, an early assistant of Enrico Fermi and then the author of numerous studies in high energy physics, especially on neutrinos. According to Oleg Gordievsky (the highest-ranking KGB officer ever to defect) and Pavel Sudoplatov (former deputy director of Foreign Intelligence for the Soviet Union), Pontecorvo was also a Soviet agent. A convinced communist, he defected to the Soviet Union in 1950, where he continued his research on the decay of the muon and on neutrinos. The prestigious Pontecorvo Prize was instituted in his memory in 1995.

Early life and education

Enrico Fermi and the Via Panisperna boys in the courtyard of Rome University's Physics Institute in Via Panisperna, about 1934. From Left to right: Oscar D'Agostino, Emilio Segrè, Edoardo Amaldi, Franco Rasetti and Enrico Fermi. Pontecorvo took the photograph.

Pontecorvo was born on 22 August in Marina di Pisa, the fourth of eight children of Massimo Pontecorvo and his wife Maria. He had older brothers Guido (born in 1907), whoi became a geneticist, and Paolo (born in 1909), an engineer who worked on radar during World War II, and an older sister Guiliana (born in 1911), along with younger brother Gillo (born in 1919), the director of The Battle of Algiers, sisters Laura (born in 1921) and Anna (born in 1924) and brother Giovanni (born in 1926). His was a wealthy Italian family; Massimo owned three textile factories employing over 1,000 people. Massimo was Jewish, while Maria was a protestant, a member of the Chiesa Evangelica Valdese.

After attending the first two years of engineering at the University of Pisa, he decided to switch to physics in 1931. On the advice of his brother Guido, he decided to study at the University of Rome La Sapienza, where Enrico Fermi had gathered together a group of promising young scientists known as the Via Panisperna boys after the name of the street where the Institute of Physics of Rome University was then situated. At the age of 18 he was admitted to the third year of Physics. Fermi described Pontecorvo as "scientifically one of the brightest men with whom I have come in contact in my scientific career". THe group nicknamed him Cucciolo, which means "puppy".

In 1934 Pontecorvo contributed to Fermi's famous experiment showing the properties of slow neutrons that led the way to the discovery of nuclear fission. Pontecorvo's name was included on the Via Panisperna boys' patent "To increase the production of artificial radioactivity with neutron bombardment". He was made a temporary assistant at the Royal Institute of Physics on 1 November 1934 and the University of Rome, and on 7 November, he was listed as co-author, along with Fermi and Rasetti, of a landmark paper on slow neutrons that reported that hydrogen slowed neutrons more than heavy elements, and that slow neutrons were more easily absorbed.

Early career

In February 1936 Pontecorvo left Italy and moved to Paris to work in the laboratory of Irène and Frédéric Joliot-Curie at the Collège de France on a one-year scholarship to study the effects of collisions of neutrons with protons and on the electromagnetic transitions among isomers. During this period, influenced by his cousin, it, he adopted the ideals of communism to which he remained loyal for the rest of his life. He formed a relationship with Marianne Nordblom, a Swedish woman working in Paris as a nanny. Whether because of his relationship with Marianne, his interesting work on isomers, or the deteriorating political situation in Italy, he turned down an opportunity in 1937 to apply for a tenured position at the University of Rome to stay in Paris.

Carlo Franzinetti (left) and Bruno Pontecorvo (right)

Marianne moved in with Pontecorvo at the Hôtel des Grands Hommes on the Place du Panthéon on 4 January 1938. Their son Gil was born on 30 July. Her visa expired, and she had to return to Sweden in September. Pontecorvo accompanied her, leaving Gil behind in a residential nursery in Paris. Travelling back to Paris alone, he dined with Manne Siegbahn and met with Niels Bohr and Lisa Meitner on 12 October 1938. Pontecorvo was now unable to return to Italy because of the Fascist regime's racial laws against the Jews. This caused the break up of the Via Panisperna boys, with Fermi moving to the United States. Pontecorvo's family also dispersed. Guido moved to Britain in 1938, followed by Giovanni, Laura and Anna in 1939, while Gillo joined Pontecorvo in Paris.

He remained in Paris until the entered the city, then fled with his family to Spain and shortly after to the United States, where he had found employment with an oil company in Tulsa, Oklahoma. While at the oil company he developed a technology and an instrument for well logging, based on the properties of neutrons. This technology may be considered the first practical application of the [[] discovery of slow neutrons.

He was not called upon to participate in the Manhattan Project in the USA for the construction of the atomic bomb, possibly because of his suspected Communist affiliations. But in 1943 he was invited to join the associated Montreal Laboratory in Canada, where he concentrated on reactor design, cosmic rays, neutrinos and the decay of muons.

In 1948, after he obtained British citizenship, he was invited by John Cockcroft to contribute to the British atomic bomb project at AERE, Harwell where he joined the Nuclear Physics Division under Egon Bretscher. In 1950 he was appointed to the chair of physics at the University of Liverpool which he was due to take up in January 1951.

Defection

However, on 31 August 1950, in the middle of a holiday in Italy, he abruptly left Rome for Stockholm with his wife and three sons without informing friends or relatives. The next day he was helped by Soviet agents to enter the Soviet Union from Finland. His abrupt disappearance caused much concern to many of the western intelligence services, especially those of Britain and the USA who were worried about the escape of atomic secrets to the Soviet Union after the then recent case of Klaus Fuchs. But as was pointed out immediately, Pontecorvo had had only limited access to "secret subjects" and even later no allegation of spying or of transferring of secrets to the Soviets has ever been made against him.

In the USSR Pontecorvo was welcomed with honors and given a number of privileges reserved only to the Soviet nomenklatura. He worked until his death in what is now the Joint Institute for Nuclear Research (JINR) in Dubna, concentrating entirely on theoretical studies of high energy particles and continuing his research on neutrinos and decay of muons. In recognition of his research he was awarded the Stalin Prize in 1953, membership to the Soviet Academy of Sciences in 1958 and two Orders of Lenin. In 1955 he appeared in public at a press conference where he explained to the world the motivations of his choice to leave the West and work in the USSR. Pontecorvo did not leave the Soviet Union for many years, the first trip being in 1978 when he travelled to Italy.

Personal life

Pontecorvo was brother of film director Gillo Pontecorvo and geneticist Guido Pontecorvo. He was a great-uncle of Flavio Pontecorvo, the electronics engineer. He had one wife: Marianne Nordblom (born in Sweden) with whom he had three children, and a long-term relationship with Rodam Amiredzhibi (born in Georgia, Soviet Union).

Death

He died in Dubna in 1993, afflicted by Parkinson's disease. Half of his ashes are now buried in the Protestant Cemetery in Rome, and another half in Dubna, Russia, according to his will.

Legacy

In 1995, in recognition of his scientific merits, the prestigious Pontecorvo Prize has been instituted by the Joint Institute for Nuclear Research. The prize, awarded annually to an individual scientist, recognizes "the most significant investigations in elementary particle physics", as acknowledged by the international scientific community.

The scientific work of Bruno Pontecorvo is full of formidable intuitions, some of which have represented milestones in modern physics. These include:

• the intuition of how to detect anti-neutrinos generated in nuclear reactors (methodology used by Frederick Reines who was awarded for this the Nobel prize in 1995);
• the prediction that neutrinos associated with electrons are different from those associated with muons (another Nobel prize was awarded to Jack Steinberger, Leon M. Lederman and Melvin Schwartz in 1988 for the experimental verification of this in 1960s);
• the idea that neutrinos may convert into other types of neutrinos, a phenomenon known as neutrino oscillation.

This last idea was proposed in 1957 and developed in subsequent years by Pontecorvo, until 1967 where it was given its modern form. A hint for this phenomenon was first seen with solar neutrinos in 1968 (see Solar neutrino problem); the existence of the oscillations was finally established by the Super-Kamiokande experiment in 1998 and later confirmed by other experiments. This prediction was recognized by the 2015 Nobel Prize in physics, awarded to Takaaki Kajita and Arthur B. McDonald.

In 2006 Moscow historical society Moskultprog unveiled an artistic plaque celebrating Pontecorvo's Moscow house at 9 Tverskaya Street.

Selected publications

• "Neutron Well Logging – A New Geological Method Based on Nuclear Physics". Oil and Gas Journal. 40: 32–33. 1941.
• Pages in the Development of Neutrino Physics, Usp.Fiz.Nauk 141, 1983, 675 [English ed. Sov. Phys. Usp. 26, 1983, 1087]
• B. Pontecorvo, "Mesonium and anti-mesonium", Sov. Phys. JETP 6 429 (1957)

See also

• PMNS matrix
• Solar neutrino problem
• Sudbury Neutrino Observatory
• Super-Kamiokande

References

• Andrew, Christopher M.; Gordievsky, Oleg (1990). KGB: The Inside Story of its Foreign Operations from Lenin to Gorbachev. New York: HarperCollins. ISBN 0-06-016605-3. OCLC 22579547. {{cite book}}: Invalid |ref=harv (help)
• Close, Frank (2015). Half-Life: The Divided Life of Bruno Pontecorvo, Physicist or Spy. Basic Books. ISBN 9780465069989. OCLC 897001600. {{cite book}}: Invalid |ref=harv (help)
• Sudoplatov, Pavel; Sudoplatov, Anatoli; Schecter, Jerrold L.; Schecter, Leona P. (1995). Special Tasks: the Memoirs of an Unwanted Witness, a Soviet Spymaster. Boston: Little, Brown. ISBN 0-316-82115-2. OCLC 30325282. {{cite book}}: Invalid |ref=harv (help)
• Turchetti, Simone (2003). Atomic Secrets and Governmental Lies: Nuclear Science, Politics and Security in the Pontecorvo case (PDF). Vol. 36. pp. 389–415. Retrieved 9 April 2016. {{cite book}}: |journal= ignored (help); Invalid |ref=harv (help)
• Turchetti, Simone (2012). The Pontecorvo Affair: a Cold War Defection and Nuclear Physics. Chicago: University of Chicago Press. ISBN 9780226816647. OCLC 711050900. {{cite book}}: Invalid |ref=harv (help)

Further reading

• Mafai, Miriam (1992). Il lungo freddo: Storia di Bruno Pontecorvo, lo scienziato che scelse l'URSS. Milan.{{cite book}}: CS1 maint: location missing publisher (link)

External links

• Biography / Scientific Works / Popular Articles / About B. Pontecorvo / Photoalbum (in English and Russian)
• 1950s news of Pontecorvo's disappearance from the BBC archive
• Confessions of an atom spy: Forty years after Bruno Pontecorvo, a British scientist, went to work for Moscow, he tells Charles Richards in Rome why he changed sides
• Annotated bibliography of Bruno Pontecorvo from the Alsos Digital Library for Nuclear Issues