Beta Decay Redux, Slow Neutrons, Bohr and his Realm

2018 ◽  
Author(s):  
Roger H. Stuewer
Keyword(s):  
Beta Decay ◽  
Nuclear Physics ◽  
Nuclear Reactions ◽  
Niels Bohr ◽  
Werner Heisenberg ◽  
Rescue Operation ◽  
Otto Robert Frisch ◽  
Experimental Nuclear Physics ◽  
Large Conference ◽  
Slow Neutrons

A large conference on nuclear physics was held in London and Cambridge from October 1–6, 1934. Six German refugee physicists were present, but Werner Heisenberg was not. Czech theoretical physicists Guido Beck and Kurt Sitte had proposed a theory of beta decay that challenged Fermi’s, which Beck presented but apparently gained no support for. On October 22, Fermi serendipitously discovered the efficaciousness of slow neutrons in producing nuclear reactions. Niels Bohr would be the greatest beneficiary of Fermi’s discovery. In 1935 Bohr, with the assistance of refugee Otto Robert Frisch, began to develop experimental nuclear physics at his institute, which after its inauguration in 1920 became a mecca for young physicists. On September 29, 1943, Bohr and his family were among the 7220 Danish and other Jews who were transported to Sweden in the greatest mass rescue operation of the war.

Nuclear Processes Related to the Ap Stars and the Heaviest Chemical Elements

1976 ◽  
Vol 32 ◽  
pp. 169-182
Author(s):  
B. Kuchowicz
Keyword(s):  
Nuclear Physics ◽  
Nuclear Reactions ◽  
Chemical Elements ◽  
Fission Products ◽  
Abundance Pattern ◽  
Isotopic Shifts ◽  
Processed Material ◽  
R Process ◽  
Ap Stars ◽  
Nuclear Processes

SummaryIsotopic shifts in the lines of the heavy elements in Ap stars, and the characteristic abundance pattern of these elements point to the fact that we are observing mainly the products of rapid neutron capture. The peculiar A stars may be treated as the show windows for the products of a recent r-process in their neighbourhood. This process can be located either in Supernovae exploding in a binary system in which the present Ap stars were secondaries, or in Supernovae exploding in young clusters. Secondary processes, e.g. spontaneous fission or nuclear reactions with highly abundant fission products, may occur further with the r-processed material in the surface of the Ap stars. The role of these stars to the theory of nucleosynthesis and to nuclear physics is emphasized.

The Age of Innocence

2018 ◽  
Author(s):  
Roger H. Stuewer
Keyword(s):  
Nuclear Physics ◽  
Nuclear Reactions ◽  
Alpha Decay ◽  
Nuclear Fission ◽  
Theoretical Physics ◽  
Lise Meitner ◽  
Artificial Radioactivity ◽  
The Great Depression ◽  
Nuclear Disintegration ◽  
Quantum Mechanical Theory

Nuclear physics emerged as the dominant field in experimental and theoretical physics between 1919 and 1939, the two decades between the First and Second World Wars. Milestones were Ernest Rutherford’s discovery of artificial nuclear disintegration (1919), George Gamow’s and Ronald Gurney and Edward Condon’s simultaneous quantum-mechanical theory of alpha decay (1928), Harold Urey’s discovery of deuterium (the deuteron), James Chadwick’s discovery of the neutron, Carl Anderson’s discovery of the positron, John Cockcroft and Ernest Walton’s invention of their eponymous linear accelerator, and Ernest Lawrence’s invention of the cyclotron (1931–2), Frédéric and Irène Joliot-Curie’s discovery and confirmation of artificial radioactivity (1934), Enrico Fermi’s theory of beta decay based on Wolfgang Pauli’s neutrino hypothesis and Fermi’s discovery of the efficacy of slow neutrons in nuclear reactions (1934), Niels Bohr’s theory of the compound nucleus and Gregory Breit and Eugene Wigner’s theory of nucleus+neutron resonances (1936), and Lise Meitner and Otto Robert Frisch’s interpretation of nuclear fission, based on Gamow’s liquid-drop model of the nucleus (1938), which Frisch confirmed experimentally (1939). These achievements reflected the idiosyncratic personalities of the physicists who made them; they were shaped by the physical and intellectual environments of the countries and institutions in which they worked; and they were buffeted by the profound social and political upheavals after the Great War: the punitive postwar treaties, the runaway inflation in Germany and Austria, the Great Depression, and the greatest intellectual migration in history, which encompassed some of the most gifted experimental and theoretical nuclear physicists in the world.

Particle accelerators in Mexico

2006 ◽  
Vol 36 (2) ◽  
pp. 297-309
Author(s):  
MARÍÍA DE LA PAZ RAMOS LARA
Keyword(s):  
Latin America ◽  
Nuclear Physics ◽  
Particle Accelerator ◽  
Particle Accelerators ◽  
Van De Graaff ◽  
Experimental Nuclear Physics

ABSTRACT The first Van de Graaff particle accelerator in Latin America was installed at the Universidad Nacional Autóónoma de Mééxico (UNAM) in 1952. This event marked the beginning of experimental nuclear physics, exclusively for peaceful purposes, in Mexico. The acquisition of this accelerator was fundamental for placing other accelerators into operation, which were used for both research and the resolution of national problems.

Werner Heisenberg and the Beginning of Nuclear Physics

Physics Today ◽  
1985 ◽  
Vol 38 (11) ◽  
pp. 60-68 ◽  
Author(s):  
Arthur I. Miller
Keyword(s):  
Nuclear Physics ◽  
Werner Heisenberg

The Crocodile and the Elephant

1997 ◽  
Vol 51 (2) ◽  
pp. 309-316
Author(s):  
A. R. Mackintosh
Keyword(s):  
Nuclear Physics ◽  
Quantum Physics ◽  
Great Majority ◽  
Gold Medal ◽  
Niels Bohr ◽  
Memorial Lecture ◽  
Mcgill University ◽  
Peter Kapitza ◽  
The University ◽  
University Of Manchester

In 1907 Ernest Rutherford (later named ‘The Crocodile’ by Peter Kapitza), 36 years old and already a world–famous physicist, moved from McGill University in Montreal, Canada, to the University of Manchester, England. In the same year Niels Bohr (later known by some as ‘The Elephant’––he was one of the very few non–royal recipients of the Order of the Elephant), a 22–year–old student at the University of Copenhagen, received the gold medal of the Royal Danish Academy for his first research project, an experimental and theoretical study of water jets. During the next 30 years, until Rutherford's death in 1937, these two great scientists dominated quantum physics. Rutherford was the father of nuclear physics; together they founded atomic physics; and, with their students and colleagues, they were responsible for the great majority of the decisive advances made in the inter–war years. This lecture tells the story of the development in quantum physics, and makes some comparisons between Bohr and Rutherford–as men and scientists–drawing especially on their extensive correspondence between 1912 and 1937, the material that Bohr gathered in connection with the publication in 1961 of his Rutherford Memorial Lecture, the interviews that he gave just before his death in 1962, and other published and unpublished material from the Niels Bohr Archive in Copenhagen.

scholarly journals Exploring the astrophysical conditions for the creation of the first r-process peak, and the impact of nuclear physics uncertainties

2020 ◽  
Vol 27 ◽  
pp. 175
Author(s):  
Stylianos Nikas ◽  
G. Martínez-Pinedo ◽  
M. R. Wu ◽  
A. Sieverding ◽  
M. P. Reiter
Keyword(s):  
Beta Decay ◽  
Nuclear Physics ◽  
Decay Rates ◽  
Abundance Pattern ◽  
Nuclear Masses ◽  
The Creation ◽  
R Process ◽  
The Impact

We present a study of nucleosynthesis for conditions of high Ye outflows from NeutronStar Mergers (NSMs). We investigate the effect of new beta-decay rates measurements and uncertaintiesin nuclear masses of the newly measured 84,85 Ga to the r-process nucleosynthesis calculations. The impactof these quantities to the production of the elements of the r-process abundance pattern for A < 100 isquantified and presented.

Observations of the Sun

1997 ◽  
Author(s):  
Douglas V. Hoyt ◽  
Kenneth H. Shatten
Keyword(s):  
Nuclear Physics ◽  
Nuclear Reactions ◽  
Stellar Structure ◽  
Heavy Elements ◽  
Helium Nucleus ◽  
The Sun ◽  
Helium Gas ◽  
A Chain ◽  
The One ◽  
The Universe

Our sun is a typical “second generation,” or G2, star nearly 4.5 billion years old. The sun is composed of 92.1% hydrogen and 7.8% helium gas, as well as 0.1% of such all-important heavy elements as oxygen, carbon, nitrogen, silicon, magnesium, neon, iron, sulfur, and so forth in decreasing amounts (see Appendix 3). The heavy elements are generated from nucleosynthetic processes in stars, novae, and supernovae after the original formation of the Universe. This has led to the popular statement that we are, literally, the “children of the stars” because our bodies are composed of the elements formed inside stars. From astronomical studies of stellar structure, we know that, since its beginnings, the sun’s luminosity has gradually increased by about 30%. This startling conclusion has raised the so-called faint young sun climate problem: if the sun were even a few percent fainter in the past, then Earth could have been covered by ice. In this frozen state, it might not have warmed because the ice would reflect most of the incoming solar radiation back into space. Although volcanic aerosols covering the ice, early oceans moderating the climate, and other theories have been suggested to circumvent the “faint young sun” problem, how Earth escaped the ice catastrophe remains uncertain. How can the sun generate vast amounts of energy for billions of years and still keep shining? Before nuclear physics, scientists believed the sun generated energy by means of slow gravitational collapse. Still, this process would only let the sun shine about 30 million years before its energy was depleted. To shine longer, the sun requires another energy source. We now believe that a chain of nuclear reactions occurs inside the sun, with four hydrogen nuclei fusing into one helium nucleus at the sun’s center. Because the four hydrogen nuclei have more mass than the one helium nucleus, the resulting mass deficit is converted into energy according to Einstein’s famous formula E = mc2. The energy, produced near the sun’s center, creates a central temperature of about 15 million degrees Kelvin (°K).

scholarly journals Neutrinoless Double-Beta Decay

2012 ◽  
Vol 2012 ◽  
pp. 1-38 ◽  
Author(s):  
Andrea Giuliani ◽  
Alfredo Poves
Keyword(s):  
Beta Decay ◽  
Particle Physics ◽  
Nuclear Physics ◽  
Experimental Situation ◽  
Neutrinoless Double Beta Decay ◽  
Majorana Neutrino ◽  
Double Beta Decay ◽  
Point Of View ◽  
The Status ◽  
Majorana Neutrino Mass

This paper introduces the neutrinoless double-beta decay (the rarest nuclear weak process) and describes the status of the research for this transition, both from the point of view of theoretical nuclear physics and in terms of the present and future experimental scenarios. Implications of this phenomenon on crucial aspects of particle physics are briefly discussed. The calculations of the nuclear matrix elements in case of mass mechanisms are reviewed, and a range for these quantities is proposed for the most appealing candidates. After introducing general experimental concepts—such as the choice of the best candidates, the different proposed technological approaches, and the sensitivity—we make the point on the experimental situation. Searches running or in preparation are described, providing an organic presentation which picks up similarities and differences. A critical comparison of the adopted technologies and of their physics reach (in terms of sensitivity to the effective Majorana neutrino mass) is performed. As a conclusion, we try to envisage what we expect round the corner and at a longer time scale.

Niels Bohr and nuclear physics

Physics Today ◽  
1963 ◽  
Vol 16 (10) ◽  
pp. 36-45 ◽  
Author(s):  
John Archibald Wheeler
Keyword(s):  
Nuclear Physics ◽  
Niels Bohr
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