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128-639: INFN was founded on the 8th of August 1951, to further the nuclear physics research tradition initiated by Enrico Fermi in Rome , in the 1930s. The INFN collaborates with CERN , Fermilab and various other laboratories in the world. In recent years it has provided important contributions to grid computing . During the latter half of the 1950s, the INFN designed and constructed the first Italian electron accelerator—the electron synchrotron developed in Frascati . In

256-402: A deuteron [NP], and also between protons and protons, and neutrons and neutrons. The effective absolute limit of the range of the nuclear force (also known as residual strong force ) is represented by halo nuclei such as lithium-11 or boron-14 , in which dineutrons , or other collections of neutrons, orbit at distances of about 10 fm (roughly similar to the 8 fm radius of

384-478: A particle accelerator , which the Via Panisperna boys did not have. Fermi had the idea to resort to replacing the polonium-beryllium neutron source with a radon -beryllium one, which he created by filling a glass bulb with beryllium powder, evacuating the air, and then adding 50 m Ci of radon gas, supplied by Giulio Cesare Trabacchi  [ it ] . This created a much stronger neutron source,

512-463: A 1932 paper "On the Interaction between Two Electrons" ( German : Über die Wechselwirkung von Zwei Elektronen ). At this time, physicists were puzzled by beta decay , in which an electron was emitted from the atomic nucleus . To satisfy the law of conservation of energy , Pauli postulated the existence of an invisible particle with no charge and little or no mass that was also emitted at

640-438: A charge has a weight equal to U/c , where U is the electrostatic energy of the system, and c is the speed of light . The first paper seemed to point out a contradiction between the electrodynamic theory and the relativistic one concerning the calculation of the electromagnetic masses, as the former predicted a value of 4/3 U/c . Fermi addressed this the next year in a paper "Concerning a contradiction between electrodynamic and

768-647: A committee of professors. Fermi applied for a chair of mathematical physics at the University of Cagliari on Sardinia but was narrowly passed over in favour of Giovanni Giorgi . In 1926, at the age of 24, he applied for a professorship at the Sapienza University of Rome. This was a new chair, one of the first three in theoretical physics in Italy, that had been created by the Minister of Education at

896-448: A diminutive of nux ('nut'), meaning 'the kernel' (i.e., the 'small nut') inside a watery type of fruit (like a peach ). In 1844, Michael Faraday used the term to refer to the "central point of an atom". The modern atomic meaning was proposed by Ernest Rutherford in 1912. The adoption of the term "nucleus" to atomic theory, however, was not immediate. In 1916, for example, Gilbert N. Lewis stated, in his famous article The Atom and

1024-432: A few hours later. The problem was traced to neutron poisoning from xenon-135 or Xe-135, a fission product with a half-life of 9.1 to 9.4 hours. Fermi and John Wheeler both deduced that Xe-135 was responsible for absorbing neutrons in the reactor, thereby sabotaging the fission process. Fermi was recommended by colleague Emilio Segrè to ask Chien-Shiung Wu , as she prepared a printed draft on this topic to be published by

1152-435: A heavier atom into two light element fragments in the manner that Noddack suggested. The Via Panisperna boys also noticed some unexplained effects. The experiment seemed to work better on a wooden table than on a marble tabletop. Fermi remembered that Joliot-Curie and Chadwick had noted that paraffin wax was effective at slowing neutrons, so he decided to try that. When neutrons were passed through paraffin wax, they induced

1280-409: A hundred times as much radioactivity in silver compared with when it was bombarded without the paraffin. Fermi guessed that this was due to the hydrogen atoms in the paraffin. Those in wood similarly explained the difference between the wooden and the marble tabletops. This was confirmed by repeating the effect with water. He concluded that collisions with hydrogen atoms slowed the neutrons. The lower

1408-556: A lecture on the subject at the Navy Department on 18 March 1939. The response fell short of what he had hoped for, although the Navy agreed to provide $ 1,500 towards further research at Columbia. Later that year, Szilárd, Eugene Wigner , and Edward Teller sent the letter signed by Einstein to US president Franklin D. Roosevelt , warning that Nazi Germany was likely to build an atomic bomb . In response, Roosevelt formed

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1536-470: A limited range because it decays quickly with distance (see Yukawa potential ); thus only nuclei smaller than a certain size can be completely stable. The largest known completely stable nucleus (i.e. stable to alpha, beta , and gamma decay ) is lead-208 which contains a total of 208 nucleons (126 neutrons and 82 protons). Nuclei larger than this maximum are unstable and tend to be increasingly short-lived with larger numbers of nucleons. However, bismuth-209

1664-604: A location in the Argonne Woods Forest Preserve, about 20 miles (32 km) from Chicago. Stone & Webster was contracted to develop the site, but the work was halted by an industrial dispute. Fermi then persuaded Compton that he could build the reactor in the squash court under the stands of the University of Chicago's Stagg Field . Construction of the pile began on 6 November 1942, and Chicago Pile-1 went critical on 2 December. The shape of

1792-421: A paper "On the quantization of the perfect monoatomic gas" ( Sulla quantizzazione del gas perfetto monoatomico ), in which he applied the exclusion principle to an ideal gas. The paper was especially notable for Fermi's statistical formulation, which describes the distribution of particles in systems of many identical particles that obey the exclusion principle. This was independently developed soon after by

1920-491: A positively charged core of radius ≈ 0.3 fm surrounded by a compensating negative charge of radius between 0.3 fm and 2 fm. The proton has an approximately exponentially decaying positive charge distribution with a mean square radius of about 0.8 fm. The shape of the atomic nucleus can be spherical, rugby ball-shaped (prolate deformation), discus-shaped (oblate deformation), triaxial (a combination of oblate and prolate deformation) or pear-shaped. Nuclei are bound together by

2048-488: A professor at the Collegio Romano , it presented mathematics , classical mechanics , astronomy , optics , and acoustics as they were understood at the time of its 1840 publication. With a scientifically inclined friend, Enrico Persico , Fermi pursued projects such as building gyroscopes and measuring the acceleration of Earth's gravity . In 1914, Fermi, who used to often meet with his father in front of

2176-448: A proton + neutron (the deuteron) can exhibit bosonic behavior when they become loosely bound in pairs, which have integer spin. In the rare case of a hypernucleus , a third baryon called a hyperon , containing one or more strange quarks and/or other unusual quark(s), can also share the wave function. However, this type of nucleus is extremely unstable and not found on Earth except in high-energy physics experiments. The neutron has

2304-495: A self-sustaining chain reaction possible. Szilárd came up with a workable design: a pile of uranium oxide blocks interspersed with graphite bricks. Szilárd, Anderson, and Fermi published a paper on "Neutron Production in Uranium". But their work habits and personalities were different, and Fermi had trouble working with Szilárd. Fermi was among the first to warn military leaders about the potential impact of nuclear energy, giving

2432-676: A semester studying under Max Born at the University of Göttingen , where he met Werner Heisenberg and Pascual Jordan . Fermi then studied in Leiden with Paul Ehrenfest from September to December 1924 on a fellowship from the Rockefeller Foundation obtained through the intercession of the mathematician Vito Volterra . Here Fermi met Hendrik Lorentz and Albert Einstein , and became friends with Samuel Goudsmit and Jan Tinbergen . From January 1925 to late 1926, Fermi taught mathematical physics and theoretical mechanics at

2560-444: A single neutron halo include Be and C. A two-neutron halo is exhibited by He, Li, B, B and C. Two-neutron halo nuclei break into three fragments, never two, and are called Borromean nuclei because of this behavior (referring to a system of three interlocked rings in which breaking any ring frees both of the others). He and Be both exhibit a four-neutron halo. Nuclei which have a proton halo include B and P. A two-proton halo

2688-447: A single proton) to about 11.7  fm for uranium . These dimensions are much smaller than the diameter of the atom itself (nucleus + electron cloud), by a factor of about 26,634 (uranium atomic radius is about 156  pm ( 156 × 10  m )) to about 60,250 ( hydrogen atomic radius is about 52.92  pm ). The branch of physics involved with the study and understanding of the atomic nucleus, including its composition and

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2816-431: A sphere of positive charge. Ernest Rutherford later devised an experiment with his research partner Hans Geiger and with help of Ernest Marsden , that involved the deflection of alpha particles (helium nuclei) directed at a thin sheet of metal foil. He reasoned that if J. J. Thomson's model were correct, the positively charged alpha particles would easily pass through the foil with very little deviation in their paths, as

2944-488: A waste of time and money, but Fermi realized that if all 2,004 tubes were loaded, the reactor could reach the required power level and efficiently produce plutonium. In April 1943, Fermi raised with Robert Oppenheimer the possibility of using the radioactive byproducts from enrichment to contaminate the German food supply. The background was fear that the German atomic bomb project was already at an advanced stage, and Fermi

3072-415: Is also stable to beta decay and has the longest half-life to alpha decay of any known isotope, estimated at a billion times longer than the age of the universe. The residual strong force is effective over a very short range (usually only a few femtometres (fm); roughly one or two nucleon diameters) and causes an attraction between any pair of nucleons. For example, between a proton and a neutron to form

3200-472: Is composed of a positively charged nucleus, with a cloud of negatively charged electrons surrounding it, bound together by electrostatic force . Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud . Protons and neutrons are bound together to form a nucleus by the nuclear force . The diameter of the nucleus is in the range of 1.70  fm ( 1.70 × 10  m ) for hydrogen (the diameter of

3328-409: Is due to two reasons: Historically, experiments have been compared to relatively crude models that are necessarily imperfect. None of these models can completely explain experimental data on nuclear structure. The nuclear radius ( R ) is considered to be one of the basic quantities that any model must predict. For stable nuclei (not halo nuclei or other unstable distorted nuclei) the nuclear radius

3456-423: Is exhibited by Ne and S. Proton halos are expected to be more rare and unstable than the neutron examples, because of the repulsive electromagnetic forces of the halo proton(s). Although the standard model of physics is widely believed to completely describe the composition and behavior of the nucleus, generating predictions from theory is much more difficult than for most other areas of particle physics . This

3584-430: Is mostly the main funding agency for high-energy physics in Italy. University personnel can be affiliated with INFN and receive from it research grants. Enrico Fermi Enrico Fermi ForMemRS ( Italian: [enˈriːko ˈfermi] ; 29 September 1901 – 28 November 1954) was an Italian and naturalized American physicist, renowned for being the creator of the world's first artificial nuclear reactor ,

3712-425: Is much more complex than simple closure of shell orbitals with magic numbers of protons and neutrons. For larger nuclei, the shells occupied by nucleons begin to differ significantly from electron shells, but nevertheless, present nuclear theory does predict the magic numbers of filled nuclear shells for both protons and neutrons. The closure of the stable shells predicts unusually stable configurations, analogous to

3840-445: Is preceded and followed by 17 or more stable elements. There are however problems with the shell model when an attempt is made to account for nuclear properties well away from closed shells. This has led to complex post hoc distortions of the shape of the potential well to fit experimental data, but the question remains whether these mathematical manipulations actually correspond to the spatial deformations in real nuclei. Problems with

3968-534: Is proportional to the volume. Surface energy . A nucleon at the surface of a nucleus interacts with fewer other nucleons than one in the interior of the nucleus and hence its binding energy is less. This surface energy term takes that into account and is therefore negative and is proportional to the surface area. Coulomb energy . The electric repulsion between each pair of protons in a nucleus contributes toward decreasing its binding energy. Asymmetry energy (also called Pauli Energy). An energy associated with

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4096-518: Is roughly proportional to the cube root of the mass number ( A ) of the nucleus, and particularly in nuclei containing many nucleons, as they arrange in more spherical configurations: The stable nucleus has approximately a constant density and therefore the nuclear radius R can be approximated by the following formula, where A = Atomic mass number (the number of protons Z , plus the number of neutrons N ) and r 0  = 1.25 fm = 1.25 × 10  m. In this equation,

4224-447: Is successful at explaining many important phenomena of nuclei, such as their changing amounts of binding energy as their size and composition changes (see semi-empirical mass formula ), but it does not explain the special stability which occurs when nuclei have special "magic numbers" of protons or neutrons. The terms in the semi-empirical mass formula, which can be used to approximate the binding energy of many nuclei, are considered as

4352-462: Is that sharing of electrons to create stable electronic orbits about the nuclei that appears to us as the chemistry of our macro world. Protons define the entire charge of a nucleus, and hence its chemical identity . Neutrons are electrically neutral, but contribute to the mass of a nucleus to nearly the same extent as the protons. Neutrons can explain the phenomenon of isotopes (same atomic number with different atomic mass). The main role of neutrons

4480-433: Is to reduce electrostatic repulsion inside the nucleus. Protons and neutrons are fermions , with different values of the strong isospin quantum number , so two protons and two neutrons can share the same space wave function since they are not identical quantum entities. They are sometimes viewed as two different quantum states of the same particle, the nucleon . Two fermions, such as two protons, or two neutrons, or

4608-605: The Advisory Committee on Uranium to investigate the matter. The Advisory Committee on Uranium provided money for Fermi to buy graphite, and he built a pile of graphite bricks on the seventh floor of the Pupin Hall laboratory. By August 1941, he had six tons of uranium oxide and thirty tons of graphite, which he used to build a still larger pile in Schermerhorn Hall at Columbia. The S-1 Section of

4736-614: The Argonne National Laboratory on 1 July 1946, the first of the national laboratories established by the Manhattan Project. The short distance between Chicago and Argonne allowed Fermi to work at both places. At Argonne he continued experimental physics, investigating neutron scattering with Leona Marshall . He also discussed theoretical physics with Maria Mayer , helping her develop insights into spin–orbit coupling that would lead to her receiving

4864-662: The B Reactor at the Hanford Site did so the next year. At Los Alamos , he headed F Division, part of which worked on Edward Teller 's thermonuclear " Super " bomb. He was present at the Trinity test on 16 July 1945, the first test of a full nuclear bomb explosion, where he used his Fermi method to estimate the bomb's yield. After the war, he helped establish the Institute for Nuclear Studies in Chicago, and served on

4992-671: The Chicago Pile-1 , and a member of the Manhattan Project . He has been called the "architect of the nuclear age " and the "architect of the atomic bomb". He was one of very few physicists to excel in both theoretical physics and experimental physics . Fermi was awarded the 1938 Nobel Prize in Physics for his work on induced radioactivity by neutron bombardment and for the discovery of transuranium elements . With his colleagues, Fermi filed several patents related to

5120-825: The Enrico Fermi Award , the Enrico Fermi Institute , the Fermi National Accelerator Laboratory (Fermilab) , the Fermi Gamma-ray Space Telescope , the Fermi paradox , and the synthetic element fermium , making him one of 16 scientists who have elements named after them . Enrico Fermi was born in Rome, Italy, on 29 September 1901. He was the third child of Alberto Fermi, a division head in

5248-466: The Fermi age equation to describe this. After bombarding thorium and uranium with slow neutrons, he concluded that he had created new elements. Although he was awarded the Nobel Prize for this discovery, the new elements were later revealed to be nuclear fission products . Fermi left Italy in 1938 to escape new Italian racial laws that affected his Jewish wife, Laura Capon . He emigrated to

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5376-569: The Interim Committee on target selection. The panel agreed with the committee that atomic bombs would be used without warning against an industrial target. Like others at the Los Alamos Laboratory, Fermi found out about the atomic bombings of Hiroshima and Nagasaki from the public address system in the technical area. Fermi did not believe that atomic bombs would deter nations from starting wars, nor did he think that

5504-655: The Nobel Prize in Physics at the age of 37 for his "demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons". After Fermi received the prize in Stockholm , he did not return home to Italy but rather continued to New York City with his family in December 1938, where they applied for permanent residency. The decision to move to America and become US citizens

5632-668: The Office of Scientific Research and Development , as the Advisory Committee on Uranium was now known, met on 18 December 1941, with the US now engaged in World War II , making its work urgent. Most of the effort sponsored by the committee had been directed at producing enriched uranium , but Committee member Arthur Compton determined that a feasible alternative was plutonium , which could be mass-produced in nuclear reactors by

5760-507: The Pauli exclusion principle . Were it not for the Coulomb energy, the most stable form of nuclear matter would have the same number of neutrons as protons, since unequal numbers of neutrons and protons imply filling higher energy levels for one type of particle, while leaving lower energy levels vacant for the other type. Pairing energy . An energy which is a correction term that arises from

5888-564: The Physical Review . Upon reading the draft, Fermi and the scientists confirmed their suspicions: Xe-135 indeed absorbed neutrons, in fact it had a huge neutron cross-section. DuPont had deviated from the Metallurgical Laboratory's original design in which the reactor had 1,500 tubes arranged in a circle, and had added 504 tubes to fill in the corners. The scientists had originally considered this over-engineering

6016-543: The Scuola Normale Superiore in July 1922, and received his laurea at the unusually young age of 20. The thesis was on X-ray diffraction images. Theoretical physics was not yet considered a discipline in Italy, and the only thesis that would have been accepted was experimental physics . For this reason, Italian physicists were slow to embrace the new ideas like relativity coming from Germany. Since Fermi

6144-409: The Scuola Normale Superiore , Fermi played pranks with fellow student Franco Rasetti ; the two became close friends and collaborators. Fermi was advised by Luigi Puccianti , director of the physics laboratory, who said there was little he could teach Fermi and often asked Fermi to teach him something instead. Fermi's knowledge of quantum physics was such that Puccianti asked him to organize seminars on

6272-402: The Trinity test on 16 July 1945 and conducted an experiment to estimate the bomb's yield by dropping strips of paper into the blast wave. He paced off the distance they were blown by the explosion, and calculated the yield as ten kilotons of TNT; the actual yield was about 18.6 kilotons. Along with Oppenheimer, Compton, and Ernest Lawrence , Fermi was part of the scientific panel that advised

6400-623: The University of Florence , where he teamed up with Rasetti to conduct a series of experiments on the effects of magnetic fields on mercury vapour. He also participated in seminars at the Sapienza University of Rome, giving lectures on quantum mechanics and solid state physics . While giving lectures on the new quantum mechanics based on the remarkable accuracy of predictions of the Schrödinger equation, Fermi would often say, "It has no business to fit so well!" After Wolfgang Pauli announced his exclusion principle in 1925, Fermi responded with

6528-471: The binding energy that would appear when a nuclide with an odd number of neutrons absorbed an extra neutron. For Fermi, the news came as a profound embarrassment, as the transuranic elements that he had partly been awarded the Nobel Prize for discovering had not been transuranic elements at all, but fission products . He added a footnote to this effect to his Nobel Prize acceptance speech. The scientists at Columbia decided that they should try to detect

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6656-403: The neutron , which James Chadwick had discovered in 1932. In March 1934, Fermi wanted to see if he could induce radioactivity with Rasetti's polonium - beryllium neutron source . Neutrons had no electric charge, and so would not be deflected by the positively charged nucleus. This meant that they needed much less energy to penetrate the nucleus than charged particles, and so would not require

6784-500: The "constant" r 0 varies by 0.2 fm, depending on the nucleus in question, but this is less than 20% change from a constant. In other words, packing protons and neutrons in the nucleus gives approximately the same total size result as packing hard spheres of a constant size (like marbles) into a tight spherical or almost spherical bag (some stable nuclei are not quite spherical, but are known to be prolate ). Models of nuclear structure include: The cluster model describes

6912-401: The "optical model", frictionlessly orbiting at high speed in potential wells. In the above models, the nucleons may occupy orbitals in pairs, due to being fermions, which allows explanation of even/odd Z and N effects well known from experiments. The exact nature and capacity of nuclear shells differs from those of electrons in atomic orbitals, primarily because the potential well in which

7040-554: The British physicist Paul Dirac , who also showed how it was related to the Bose–Einstein statistics . Accordingly, it is now known as Fermi–Dirac statistics . After Dirac, particles that obey the exclusion principle are today called " fermions ", while those that do not are called " bosons ". Professorships in Italy were granted by competition ( concorso ) for a vacant chair, the applicants being rated on their publications by

7168-690: The Fifth Washington Conference on Theoretical Physics began in Washington, D.C. under the joint auspices of George Washington University and the Carnegie Institution of Washington . There, the news on nuclear fission was spread even further, fostering many more experimental demonstrations. French scientists Hans von Halban , Lew Kowarski , and Frédéric Joliot-Curie had demonstrated that uranium bombarded by neutrons emitted more neutrons than it absorbed, suggesting

7296-610: The General Advisory Committee, chaired by J. Robert Oppenheimer , which advised the Atomic Energy Commission on nuclear matters. After the detonation of the first Soviet fission bomb in August 1949, he strongly opposed the development of a hydrogen bomb on both moral and technical grounds. He was among the scientists who testified on Oppenheimer's behalf at the 1954 hearing that resulted in

7424-580: The Italian journal I Rendiconti dell'Accademia dei Lincei  [ it ] . In this article, he examined the Principle of Equivalence , and introduced the so-called " Fermi coordinates ". He proved that on a world line close to the timeline, space behaves as if it were a Euclidean space . Fermi submitted his thesis, "A theorem on probability and some of its applications" ( Un teorema di calcolo delle probabilità ed alcune sue applicazioni ), to

7552-473: The Ministry of Railways, and Ida de Gattis, an elementary school teacher. His sister, Maria, was two years older, his brother Giulio a year older. After the two boys were sent to a rural community to be wet nursed , Enrico rejoined his family in Rome when he was two and a half. Although he was baptized a Catholic in accordance with his grandparents' wishes, his family was not particularly religious; Enrico

7680-567: The Molecule , that "the atom is composed of the kernel and an outer atom or shell. " Similarly, the term kern meaning kernel is used for nucleus in German and Dutch. The nucleus of an atom consists of neutrons and protons, which in turn are the manifestation of more elementary particles, called quarks , that are held in association by the nuclear strong force in certain stable combinations of hadrons , called baryons . The nuclear strong force extends far enough from each baryon so as to bind

7808-602: The Nobel Prize. The Manhattan Project was replaced by the Atomic Energy Commission (AEC) on 1 January 1947. Fermi served on the AEC General Advisory Committee, an influential scientific committee chaired by Robert Oppenheimer. He also liked to spend a few weeks each year at the Los Alamos National Laboratory, where he collaborated with Nicholas Metropolis , and with John von Neumann on Rayleigh–Taylor instability ,

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7936-536: The United States, where he worked on the Manhattan Project during World War II. Fermi led the team at the University of Chicago that designed and built Chicago Pile-1, which went critical on 2 December 1942, demonstrating the first human-created, self-sustaining nuclear chain reaction . He was on hand when the X-10 Graphite Reactor at Oak Ridge, Tennessee went critical in 1943, and when

8064-443: The atomic number of the nucleus it collides with, the more energy a neutron loses per collision, and therefore the fewer collisions that are required to slow a neutron down by a given amount. Fermi realised that this induced more radioactivity because slow neutrons were more easily captured than fast ones. He developed a diffusion equation to describe this, which became known as the Fermi age equation . In 1938, Fermi received

8192-518: The book, having solved all the problems proposed at the end of the book, some of which Adolfo considered difficult. Upon verifying this, Adolfo felt that Fermi was "a prodigy, at least with respect to geometry", and further mentored the boy, providing him with more books on physics and mathematics. Adolfo noted that Fermi had a very good memory and thus could return the books after having read them because he could remember their content very well. Fermi graduated from high school in July 1918, having skipped

8320-457: The challenge. The consequences of the Fermi theory are vast. For example, β spectroscopy was established as a powerful tool for the study of nuclear structure. But perhaps the most influential aspect of this work of Fermi is that his particular form of the β interaction established a pattern that has been appropriate for the study of other types of interactions. It was the first successful theory of

8448-464: The creation and annihilation of material particles. Previously, only photons had been known to be created and destroyed. In January 1934, Irène Joliot-Curie and Frédéric Joliot announced that they had bombarded elements with alpha particles and induced radioactivity in them. By March, Fermi's assistant Gian-Carlo Wick had provided a theoretical explanation using Fermi's theory of beta decay. Fermi decided to switch to experimental physics, using

8576-542: The credit to Lamb: I remember very vividly the first month, January, 1939, that I started working at the Pupin Laboratories because things began happening very fast. In that period, Niels Bohr was on a lecture engagement at the Princeton University and I remember one afternoon Willis Lamb came back very excited and said that Bohr had leaked out great news. The great news that had leaked out was

8704-510: The denial of Oppenheimer's security clearance. Fermi did important work in particle physics, especially related to pions and muons , and he speculated that cosmic rays arose when the material was accelerated by magnetic fields in interstellar space. Many awards, concepts, and institutions are named after Fermi , including the Fermi 1 (breeder reactor), the Enrico Fermi Nuclear Generating Station ,

8832-458: The discovery of fission and at least the outline of its interpretation. Then, somewhat later that same month, there was a meeting in Washington where the possible importance of the newly discovered phenomenon of fission was first discussed in semi-jocular earnest as a possible source of nuclear power . Noddack was proven right after all. Fermi had dismissed the possibility of fission on the basis of his calculations, but he had not taken into account

8960-679: The early 1960s, it also constructed in Frascati the first ever electron-positron collider ( ADA - Anello Di Accumulazione ), under the scientific leadership of Bruno Touschek . In 1968, Frascati began operating ADONE ( big AdA), which was the first high-energy particle collider , having a beam energy of 1.5 GeV. During the same period, the INFN began to participate in research into the construction and use of ever-more powerful accelerators being conducted at CERN . The INFN has Sezioni (Divisions) in most major Italian universities and four national laboratories. It has personnel of its own, but it

9088-554: The effectiveness of which declined with the 3.8-day half-life of radon. He knew that this source would also emit gamma rays , but, on the basis of his theory, he believed that this would not affect the results of the experiment. He started by bombarding platinum , an element with a high atomic number that was readily available, without success. He turned to aluminium , which emitted an alpha particle and produced sodium , which then decayed into magnesium by beta particle emission. He tried lead , without success, and then fluorine in

9216-414: The electromagnetic forces that hold the parts of the atoms together internally (for example, the forces that hold the electrons in an inert gas atom bound to its nucleus). The nuclear force is highly attractive at the distance of typical nucleon separation, and this overwhelms the repulsion between protons due to the electromagnetic force, thus allowing nuclei to exist. However, the residual strong force has

9344-402: The end of 1944. He decided to concentrate the plutonium work at the University of Chicago . Fermi reluctantly moved, and his team became part of the new Metallurgical Laboratory there. The possible results of a self-sustaining nuclear reaction were unknown, so it seemed inadvisable to build the first nuclear reactor on the University of Chicago campus in the middle of the city. Compton found

9472-458: The energy released in the nuclear fission of uranium when bombarded by neutrons. On 25 January 1939, in the basement of Pupin Hall at Columbia, an experimental team including Fermi conducted the first nuclear fission experiment in the United States. The other members of the team were Herbert L. Anderson , Eugene T. Booth , John R. Dunning , G. Norris Glasoe , and Francis G. Slack . The next day,

9600-431: The foil should act as electrically neutral if the negative and positive charges are so intimately mixed as to make it appear neutral. To his surprise, many of the particles were deflected at very large angles. Because the mass of an alpha particle is about 8000 times that of an electron, it became apparent that a very strong force must be present if it could deflect the massive and fast moving alpha particles. He realized that

9728-494: The forces that bind it together, is called nuclear physics . The nucleus was discovered in 1911, as a result of Ernest Rutherford 's efforts to test Thomson's " plum pudding model " of the atom. The electron had already been discovered by J. J. Thomson . Knowing that atoms are electrically neutral, J. J. Thomson postulated that there must be a positive charge as well. In his plum pudding model, Thomson suggested that an atom consisted of negative electrons randomly scattered within

9856-423: The form of calcium fluoride , which emitted an alpha particle and produced nitrogen , decaying into oxygen by beta particle emission. In all, he induced radioactivity in 22 different elements. Fermi rapidly reported the discovery of neutron-induced radioactivity in the Italian journal La Ricerca Scientifica on 25 March 1934. The natural radioactivity of thorium and uranium made it hard to determine what

9984-548: The laboratory for whatever purposes they chose. Fermi decided that they should research X-ray crystallography , and the three worked to produce a Laue photograph—an X-ray photograph of a crystal. During 1921, his third year at the university, Fermi published his first scientific works in the Italian journal Nuovo Cimento . The first was entitled "On the dynamics of a rigid system of electrical charges in translational motion" ( Sulla dinamica di un sistema rigido di cariche elettriche in moto traslatorio ). A sign of things to come

10112-461: The law allowed. In September 1944, Fermi inserted the first uranium fuel slug into the B Reactor at the Hanford Site , the production reactor designed to breed plutonium in large quantities. Like X-10, it had been designed by Fermi's team at the Metallurgical Laboratory and built by DuPont, but it was much larger and was water-cooled. Over the next few days, 838 tubes were loaded, and the reactor went critical. Shortly after midnight on 27 September,

10240-541: The near future", he wrote, "to find a way to release these dreadful amounts of energy—which is all to the good because the first effect of an explosion of such a dreadful amount of energy would be to smash into smithereens the physicist who had the misfortune to find a way to do it." In 1924, Fermi was initiated into the Masonic Lodge "Adriano Lemmi" of the Grand Orient of Italy . In 1923–1924, Fermi spent

10368-430: The neutrons and protons together against the repulsive electrical force between the positively charged protons. The nuclear strong force has a very short range, and essentially drops to zero just beyond the edge of the nucleus. The collective action of the positively charged nucleus is to hold the electrically negative charged electrons in their orbits about the nucleus. The collection of negatively charged electrons orbiting

10496-425: The new physics as widely as possible. Part of his teaching method was to gather his colleagues and graduate students together at the end of the day and go over a problem, often from his own research. A sign of success was that foreign students now began to come to Italy. The most notable of these was the German physicist Hans Bethe , who came to Rome as a Rockefeller Foundation fellow, and collaborated with Fermi on

10624-421: The noble group of nearly-inert gases in chemistry. An example is the stability of the closed shell of 50 protons, which allows tin to have 10 stable isotopes, more than any other element. Similarly, the distance from shell-closure explains the unusual instability of isotopes which have far from stable numbers of these particles, such as the radioactive elements 43 ( technetium ) and 61 ( promethium ), each of which

10752-427: The nucleons move (especially in larger nuclei) is quite different from the central electromagnetic potential well which binds electrons in atoms. Some resemblance to atomic orbital models may be seen in a small atomic nucleus like that of helium-4 , in which the two protons and two neutrons separately occupy 1s orbitals analogous to the 1s orbital for the two electrons in the helium atom, and achieve unusual stability for

10880-457: The nucleus as a molecule-like collection of proton-neutron groups (e.g., alpha particles ) with one or more valence neutrons occupying molecular orbitals. Early models of the nucleus viewed the nucleus as a rotating liquid drop. In this model, the trade-off of long-range electromagnetic forces and relatively short-range nuclear forces, together cause behavior which resembled surface tension forces in liquid drops of different sizes. This formula

11008-412: The nucleus display an affinity for certain configurations and numbers of electrons that make their orbits stable. Which chemical element an atom represents is determined by the number of protons in the nucleus; the neutral atom will have an equal number of electrons orbiting that nucleus. Individual chemical elements can create more stable electron configurations by combining to share their electrons. It

11136-567: The nucleus of uranium-238 ). These nuclei are not maximally dense. Halo nuclei form at the extreme edges of the chart of the nuclides —the neutron drip line and proton drip line—and are all unstable with short half-lives, measured in milliseconds ; for example, lithium-11 has a half-life of 8.8 ms . Halos in effect represent an excited state with nucleons in an outer quantum shell which has unfilled energy levels "below" it (both in terms of radius and energy). The halo may be made of either neutrons [NN, NNN] or protons [PP, PPP]. Nuclei which have

11264-454: The office after work, met a colleague of his father called Adolfo Amidei, who would walk part of the way home with Alberto. Enrico had learned that Adolfo was interested in mathematics and physics and took the opportunity to ask Adolfo a question about geometry. Adolfo understood that the young Fermi was referring to projective geometry and then proceeded to give him a book on the subject written by Theodor Reye . Two months later, Fermi returned

11392-426: The operators began to withdraw the control rods to initiate production. At first, all appeared to be well, but around 03:00, the power level started to drop and by 06:30 the reactor had shut down completely. The Army and DuPont turned to Fermi's team for answers. The cooling water was investigated to see if there was a leak or contamination. The next day the reactor suddenly started up again, only to shut down once more

11520-501: The opportunities provided by the reactor's abundant production of free neutrons. The laboratory soon branched out from physics and engineering into using the reactor for biological and medical research. Initially, Argonne was run by Fermi as part of the University of Chicago, but it became a separate entity with Fermi as its director in May 1944. When the air-cooled X-10 Graphite Reactor at Oak Ridge went critical on 4 November 1943, Fermi

11648-533: The pile could be completed, I added, "the earth was not as large as he had estimated, and he arrived at the new world sooner than he had expected." "Is that so," was Conant's excited response. "Were the natives friendly?" "Everyone landed safe and happy." To continue the research where it would not pose a public health hazard, the reactor was disassembled and moved to the Argonne Woods site. There Fermi directed experiments on nuclear reactions, reveling in

11776-399: The pile was intended to be roughly spherical, but as work proceeded Fermi calculated that criticality could be achieved without finishing the entire pile as planned. This experiment was a landmark in the quest for energy, and it was typical of Fermi's approach. Every step was carefully planned, and every calculation was meticulously done. When the first self-sustained nuclear chain reaction

11904-460: The plum pudding model could not be accurate and that the deflections of the alpha particles could only be explained if the positive and negative charges were separated from each other and that the mass of the atom was a concentrated point of positive charge. This justified the idea of a nuclear atom with a dense center of positive charge and mass. The term nucleus is from the Latin word nucleus ,

12032-443: The possibility of a chain reaction. Fermi and Anderson did so too a few weeks later. Leó Szilárd obtained 200 kilograms (440 lb) of uranium oxide from Canadian radium producer Eldorado Gold Mines Limited , allowing Fermi and Anderson to conduct experiments with fission on a much larger scale. Fermi and Szilárd collaborated on the design of a device to achieve a self-sustaining nuclear reaction—a nuclear reactor . Owing to

12160-412: The postulated particle, which he named the " neutrino ". His theory, later referred to as Fermi's interaction and now called weak interaction , described one of the four fundamental interactions in nature. Through experiments inducing radioactivity with the recently discovered neutron , Fermi discovered that slow neutrons were more easily captured by atomic nuclei than fast ones, and he developed

12288-419: The principle to an ideal gas , employing a statistical formulation now known as Fermi–Dirac statistics . Today, particles that obey the exclusion principle are called " fermions ". Pauli later postulated the existence of an uncharged invisible particle emitted along with an electron during beta decay , to satisfy the law of conservation of energy . Fermi took up this idea, developing a model that incorporated

12416-472: The proton and neutron potential wells. While each nucleon is a fermion, the {NP} deuteron is a boson and thus does not follow Pauli Exclusion for close packing within shells. Lithium-6 with 6 nucleons is highly stable without a closed second 1p shell orbital. For light nuclei with total nucleon numbers 1 to 6 only those with 5 do not show some evidence of stability. Observations of beta-stability of light nuclei outside closed shells indicate that nuclear stability

12544-406: The rate of absorption of neutrons by the hydrogen in water, it was unlikely that a self-sustaining reaction could be achieved with natural uranium and water as a neutron moderator . Fermi suggested, based on his work with neutrons, that the reaction could be achieved with uranium oxide blocks and graphite as a moderator instead of water. This would reduce the neutron capture rate, and in theory make

12672-460: The relativistic theory of electromagnetic mass" in which he showed that the apparent contradiction was a consequence of relativity. This paper was sufficiently well-regarded that it was translated into German and published in the German scientific journal Physikalische Zeitschrift in 1922. That year, Fermi submitted his article "On the phenomena occurring near a world line " ( Sopra i fenomeni che avvengono in vicinanza di una linea oraria ) to

12800-438: The residual strong force ( nuclear force ). The residual strong force is a minor residuum of the strong interaction which binds quarks together to form protons and neutrons. This force is much weaker between neutrons and protons because it is mostly neutralized within them, in the same way that electromagnetic forces between neutral atoms (such as van der Waals forces that act between two inert gas atoms) are much weaker than

12928-517: The result of nuclear fission . Frisch confirmed this experimentally on 13 January 1939. The news of Meitner and Frisch's interpretation of Hahn and Strassmann's discovery crossed the Atlantic with Niels Bohr , who was to lecture at Princeton University . Isidor Isaac Rabi and Willis Lamb , two Columbia University physicists working at Princeton, found out about it and carried it back to Columbia. Rabi said he told Enrico Fermi, but Fermi later gave

13056-424: The same reason. Nuclei with 5 nucleons are all extremely unstable and short-lived, yet, helium-3 , with 3 nucleons, is very stable even with lack of a closed 1s orbital shell. Another nucleus with 3 nucleons, the triton hydrogen-3 is unstable and will decay into helium-3 when isolated. Weak nuclear stability with 2 nucleons {NP} in the 1s orbital is found in the deuteron hydrogen-2 , with only one nucleon in each of

13184-462: The same time. Fermi took up this idea, which he developed in a tentative paper in 1933, and then a longer paper the next year that incorporated the postulated particle, which Fermi called a " neutrino ". His theory, later referred to as Fermi's interaction , and still later as the theory of the weak interaction , described one of the four fundamental forces of nature . The neutrino was detected after his death, and his interaction theory showed why it

13312-418: The school's lodgings away from Rome for four years. Fermi took first place in the difficult entrance exam, which included an essay on the theme of "Specific characteristics of Sounds"; the 17-year-old Fermi chose to use Fourier analysis to derive and solve the partial differential equation for a vibrating rod, and after interviewing Fermi the examiner declared he would become an outstanding physicist. At

13440-509: The science of what occurs at the border between two fluids of different densities. Atomic nuclei The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom , discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment . After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg . An atom

13568-424: The sum of five types of energies (see below). Then the picture of a nucleus as a drop of incompressible liquid roughly accounts for the observed variation of binding energy of the nucleus: [REDACTED] Volume energy . When an assembly of nucleons of the same size is packed together into the smallest volume, each interior nucleon has a certain number of other nucleons in contact with it. So, this nuclear energy

13696-400: The tendency of proton pairs and neutron pairs to occur. An even number of particles is more stable than an odd number. A number of models for the nucleus have also been proposed in which nucleons occupy orbitals, much like the atomic orbitals in atomic physics theory. These wave models imagine nucleons to be either sizeless point particles in potential wells, or else probability waves as in

13824-459: The theory published in Italian and German before it was published in English. In the introduction to the 1968 English translation, physicist Fred L. Wilson noted that: Fermi's theory, aside from bolstering Pauli's proposal of the neutrino, has a special significance in the history of modern physics. One must remember that only the naturally occurring β emitters were known at the time the theory

13952-692: The third year entirely. At Amidei's urging, Fermi learned German to be able to read the many scientific papers that were published in that language at the time, and he applied to the Scuola Normale Superiore in Pisa . Amidei felt that the Scuola would provide better conditions for Fermi's development than the Sapienza University of Rome could at the time. Having lost one son, Fermi's parents only reluctantly allowed him to live in

14080-618: The time was ripe for world government . He therefore did not join the Association of Los Alamos Scientists . Fermi became the Charles H. Swift Distinguished Professor of Physics at the University of Chicago on 1 July 1945, although he did not depart the Los Alamos Laboratory with his family until 31 December 1945. He was elected a member of the US National Academy of Sciences in 1945. The Metallurgical Laboratory became

14208-474: The topic. During this time Fermi learned tensor calculus , a technique key to general relativity . Fermi initially chose mathematics as his major but soon switched to physics. He remained largely self-taught, studying general relativity, quantum mechanics , and atomic physics . In September 1920, Fermi was admitted to the physics department. Since there were only three students in the department—Fermi, Rasetti, and Nello Carrara —Puccianti let them freely use

14336-511: The urging of professor Orso Mario Corbino , who was the university's professor of experimental physics, the director of the Institute of Physics, and a member of Benito Mussolini 's cabinet. Corbino, who also chaired the selection committee, hoped that the new chair would raise the standard and reputation of physics in Italy. The committee chose Fermi ahead of Enrico Persico and Aldo Pontremoli , and Corbino helped Fermi recruit his team, which

14464-410: The use of nuclear power, all of which were taken over by the US government. He made significant contributions to the development of statistical mechanics , quantum theory , and nuclear and particle physics . Fermi's first major contribution involved the field of statistical mechanics. After Wolfgang Pauli formulated his exclusion principle in 1925, Fermi followed with a paper in which he applied

14592-674: Was achieved, Compton made a coded phone call to James B. Conant , the chairman of the National Defense Research Committee . I picked up the phone and called Conant. He was reached at the President's office at Harvard University . "Jim," I said, "you'll be interested to know that the Italian navigator has just landed in the new world." Then, half apologetically, because I had led the S-l Committee to believe that it would be another week or more before

14720-569: Was also sceptical at the time that an atomic bomb could be developed quickly enough. Oppenheimer discussed the "promising" proposal with Edward Teller, who suggested the use of strontium-90 . James B. Conant and Leslie Groves were also briefed, but Oppenheimer wanted to proceed with the plan only if enough food could be contaminated with the weapon to kill half a million people. In mid-1944, Oppenheimer persuaded Fermi to join his Project Y at Los Alamos, New Mexico . Arriving in September, Fermi

14848-561: Was an agnostic throughout his adult life. As a young boy, he shared the same interests as his brother Giulio, building electric motors and playing with electrical and mechanical toys. Giulio died during an operation on a throat abscess in 1915 and Maria died in an airplane crash near Milan in 1959. At a local market in Campo de' Fiori , Fermi found a physics book, the 900-page Elementorum physicae mathematicae . Written in Latin by Jesuit Father Andrea Caraffa  [ it ] ,

14976-945: Was appointed a member of the Royal Academy of Italy by Mussolini, and on 27 April he joined the Fascist Party . He later opposed Fascism when the 1938 racial laws were promulgated by Mussolini in order to bring Italian Fascism ideologically closer to German Nazism . These laws threatened Laura, who was Jewish, and put many of Fermi's research assistants out of work. During their time in Rome, Fermi and his group made important contributions to many practical and theoretical aspects of physics. In 1928, he published his Introduction to Atomic Physics ( Introduzione alla fisica atomica ), which provided Italian university students with an up-to-date and accessible text. Fermi also conducted public lectures and wrote popular articles for scientists and teachers in order to spread knowledge of

15104-536: Was appointed an associate director of the laboratory, with broad responsibility for nuclear and theoretical physics, and was placed in charge of F Division, which was named after him. F Division had four branches: F-1 Super and General Theory under Teller, which investigated the "Super" (thermonuclear) bomb ; F-2 Water Boiler under L. D. P. King, which looked after the "water boiler" aqueous homogeneous research reactor ; F-3 Super Experimentation under Egon Bretscher ; and F-4 Fission Studies under Anderson. Fermi observed

15232-569: Was due primarily to the racial laws in Italy. Fermi arrived in New York City on 2 January 1939. He was immediately offered positions at five universities, and accepted one at Columbia University , where he had already given summer lectures in 1936. He received the news that in December 1938, the German chemists Otto Hahn and Fritz Strassmann had detected the element barium after bombarding uranium with neutrons, which Lise Meitner and her nephew Otto Frisch correctly interpreted as

15360-422: Was happening when these elements were bombarded with neutrons but, after correctly eliminating the presence of elements lighter than uranium but heavier than lead, Fermi concluded that they had created new elements, which he called ausenium and hesperium . The chemist Ida Noddack suggested that some of the experiments could have produced lighter elements than lead rather than new, heavier elements. Her suggestion

15488-619: Was not suitable for the publication of even a new physical theory. More suitable, if anything, would have been the Proceedings of the Royal Society of London . He agrees with some scholars' hypothesis, according to which the rejection of the British magazine convinced his young colleagues (some of them Jews and leftists) to give up the boycott of German scientific magazines, after Hitler came to power in January 1933. Thus Fermi saw

15616-419: Was not taken seriously at the time because her team had not carried out any experiments with uranium or built the theoretical basis for this possibility. At that time, fission was thought to be improbable if not impossible on theoretical grounds. While physicists expected elements with higher atomic numbers to form from neutron bombardment of lighter elements, nobody expected neutrons to have enough energy to split

15744-402: Was on hand just in case something went wrong. The technicians woke him early so that he could see it happen. Getting X-10 operational was another milestone in the plutonium project. It provided data on reactor design, training for DuPont staff in reactor operation, and produced the first small quantities of reactor-bred plutonium. Fermi became an American citizen in July 1944, the earliest date

15872-402: Was proposed. Later when positron decay was discovered, the process was easily incorporated within Fermi's original framework. On the basis of his theory, the capture of an orbital electron by a nucleus was predicted and eventually observed. With time, experimental data accumulated significantly. Although peculiarities have been observed many times in β decay, Fermi's theory always has been equal to

16000-552: Was quite at home in the lab doing experimental work, this did not pose insurmountable problems for him. While writing the appendix for the Italian edition of the book Fundamentals of Einstein Relativity by August Kopff in 1923, Fermi was the first to point out that hidden inside the Einstein equation ( E = mc ) was an enormous amount of nuclear potential energy to be exploited. "It does not seem possible, at least in

16128-458: Was so difficult to detect. When he submitted his paper to the British journal Nature , that journal's editor turned it down because it contained speculations which were "too remote from physical reality to be of interest to readers". According to Fermi's biographer David N. Schwartz, it is at least strange that Fermi seriously requested publication from the journal, since at that time Nature only published short notes on articles of this kind, and

16256-550: Was soon joined by notable students such as Edoardo Amaldi , Bruno Pontecorvo , Ettore Majorana and Emilio Segrè , and by Franco Rasetti, whom Fermi had appointed as his assistant. They soon nicknamed the " Via Panisperna boys " after the street where the Institute of Physics was located. Fermi married Laura Capon , a science student at the university, on 19 July 1928. They had two children: Nella, born in January 1931, and Giulio, born in February 1936. On 18 March 1929, Fermi

16384-555: Was that the mass was expressed as a tensor —a mathematical construct commonly used to describe something moving and changing in three-dimensional space. In classical mechanics, mass is a scalar quantity, but in relativity, it changes with velocity. The second paper was "On the electrostatics of a uniform gravitational field of electromagnetic charges and on the weight of electromagnetic charges" ( Sull'elettrostatica di un campo gravitazionale uniforme e sul peso delle masse elettromagnetiche ). Using general relativity, Fermi showed that

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