Nuclear Physics

2017 ◽  
Author(s):  
Nicholas Manton ◽  
Nicholas Mee
Keyword(s):  
Nuclear Physics ◽  
Alpha Decay ◽  
Nuclear Fission ◽  
Nuclear Potential ◽  
Magic Numbers ◽  
Ongoing Research ◽  
Strong Force ◽  
Atomic Nuclei ◽  
Nilsson Model ◽  
Semi Empirical

The chapter gives an overview of nuclear physics from the discovery of the neutron to ongoing research topics. General properties of atomic nuclei are considered: the valley of stability, the nuclear potential, the pairing of nucleons and the strong force. The semi-empirical liquid drop model is presented as a description of relatively large atomic nuclei. The nuclear shell model is described, along with its relationship to magic numbers and beta decay, and is then refined to produce the Nilsson model. Gamow tunnelling is used to explain alpha decay and the Geiger–Nuttall law. It is then applied to nuclear fission and used to calculate rates for thermonuclear fusion in stars. ITER and controlled nuclear fusion are also discussed. Production of superheavy nuclei is detailed and the existence of exotic nuclei, such as halo nuclei, is considered. The Yukawa theory of the strong force is discussed, including its relationship to QCD.

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.

Prediction of Alpha Decay Half-Lives of Z = 118–121 Superheavy Nuclei with A ≤ 300 by Using the Double-Folding Potential

2019 ◽  
Vol 74 (7) ◽  
pp. 551-560 ◽  
Author(s):  
M. Sayahi ◽  
V. Dehghani ◽  
D. Naderi ◽  
S.A. Alavi
Keyword(s):  
Alpha Decay ◽  
Nucleon Nucleon ◽  
Nuclear Potential ◽  
Cluster Decay ◽  
Superheavy Nuclei ◽  
Empirical Formulas ◽  
Folding Potential ◽  
Double Folding ◽  
Semi Empirical ◽  
Double Folding Potential

AbstractThe alpha decay half-lives ofZ= 118–121 superheavy nuclei withA≤ 300 are calculated by using the density-dependent nuclear potential in the framework of the WKB method. The Paris and Ried M3Y nucleon-nucleon potentials are used in the calculation of the double-folding potential, which the Paris potential predicts to be the larger value of the half-lives. The obtained half-lives with Paris parameterisation are compared with those using three semi-empirical formulas, namely the improved Sahu formula, the universal decay law for alpha decay, and the formula for both alpha decay and cluster decay. The predicted half-lives with double-folding lie in between the improved Sahu and universal decay law formulas for both alpha and cluster decay. However, it is closer to the universal decay law formula and obeys its trend in all the studied superheavy nuclei.

4. Odds, evens, and shells

2015 ◽  
Author(s):  
Frank Close
Keyword(s):  
Stable Isotopes ◽  
Binding Energy ◽  
Total Mass ◽  
Mass Formula ◽  
Fundamental Property ◽  
Alpha Decay ◽  
Magic Numbers ◽  
Particle Cluster ◽  
Semi Empirical ◽  
Uranium Fission

‘Odds, evens, and shells’ considers the fundamental property laws governing nuclear structure. It explains element stability and abundance, as well as the quantum rules, magic numbers, shells, and binding energy that explain atomic and element structure. An effective guide to stability, and the pattern of radioactive decays, is given by the semi-empirical mass formula. As nature seeks stability by minimising energy, a nucleus seeks to lower the total mass or increase the binding energy by emitting an alpha particle cluster, by beta decay, or by splitting in two, as in uranium fission. Alpha decay and technetium, the lightest element that is totally radioactive, and thus without any stable isotopes, are also described.

scholarly journals Magic numbers for shape coexistence

2019 ◽  
Vol 26 ◽  
pp. 9
Author(s):  
I. E. Assimakis ◽  
Dennis Bonatsos ◽  
Andriana Martinou ◽  
S. Sarantopoulou ◽  
S. Peroulis ◽  
...  
Keyword(s):  
Harmonic Oscillator ◽  
Three Dimensional ◽  
Wave Functions ◽  
Magic Numbers ◽  
Shape Coexistence ◽  
Quantitative Investigation ◽  
Atomic Nuclei ◽  
Model Wave ◽  
Nilsson Model

The increasing deformation in atomic nuclei leads to the change of the classical magic numbers (2,8,20,28,50,82…) which dictate the arrangement of nucleons in complete shells. The magic numbers of the three-dimensional harmonic oscillator (2,8,20,40,70,…) emerge at deformations around ε=0.6. At lower deformations the two sets of magic numbers antagonize, leading to shape coexistence. A quantitative investigation is performed using the usual Nilsson model wave functions and the recently introduced proxy–SU(3) scheme.

scholarly journals The collision of α-particles with atomic nuclei

1932 ◽  
Vol 137 (832) ◽  
pp. 447-463 ◽  
Keyword(s):  
Nuclear Physics ◽  
Light Nuclei ◽  
Nuclear Potential ◽  
Experimental Investigations ◽  
Virtual Level ◽  
Potential Barriers ◽  
Atomic Nuclei ◽  
Particle Exchange ◽  
Usual Theory ◽  
Α Particles

Since the introduction of the concept of nuclear potential barriers by Gurney and Condon and by Gamow a great deal of attention has been concentrated on the behaviour of such systems. As a consequence of this there has been a considerable increase of knowledge of nuclear phenomena, particularly in so far as these are concerned with α-particles. As a great proportion of experimental investigations in nuclear physics are concerned with the observation of effects due to impacts of α-particles on nuclei, the theoretical investigation of such collisions is of great interest. In this connection difficulties arise owing to the strong perturbation of the α-particle wave by the nuclear potential barrier. This renders the ordinary theory of collisions, due to Born, inapplicable and this failure of the usual theory was not realised for some time. A more suitable theory has never been developed explicitly, though formulæ which one would expect to derive from such a theory have been used. In this paper a suitable theory is developed. Besides establishing the validity of the above formulæ, this theory is also applied to the consideration of the probability of α-particle exchange on impact and to the elastic scattering by light nuclei (Mg, Al, etc.). It is shown that α-particle exchange is of considerable importance when the energy of the incident α-particle coincides with that of a virtual level of the nucleus and will have the effect of broadening the level.

scholarly journals Rapid imaging of special nuclear materials for nuclear nonproliferation and terrorism prevention

2021 ◽  
Vol 7 (21) ◽  
pp. eabg3032
Author(s):  
Jana Petrović ◽  
Alf Göök ◽  
Bo Cederwall
Keyword(s):  
Nuclear Physics ◽  
Imaging Modality ◽  
Three Dimensional ◽  
Nuclear Fission ◽  
Machine Learning Techniques ◽  
Nuclear Materials ◽  
Prototype System ◽  
Fast Time ◽  
Gamma Emission ◽  
Special Nuclear Materials

We introduce a neutron-gamma emission tomography (NGET) technique for rapid detection, three-dimensional imaging, and characterization of special nuclear materials like weapons-grade plutonium and uranium. The technique is adapted from fundamental nuclear physics research and represents a previously unexplored approach to the detection and imaging of small quantities of these materials. The method is demonstrated on a radiation portal monitor prototype system based on fast organic scintillators, measuring the characteristic fast time and energy correlations between particles emitted in nuclear fission processes. The use of these correlations in real time in conjunction with modern machine learning techniques provides unprecedented imaging efficiency and high spatial resolution. This imaging modality addresses global security threats from terrorism and the proliferation of nuclear weapons. It also provides enhanced capabilities for addressing different nuclear accident scenarios and for environmental radiological surveying.

Universal origin of heavy elements

2021 ◽  
Author(s):  
Jose Orce ◽  
Balaram Dey ◽  
Cebo Ngwetsheni ◽  
Brenden Lesch ◽  
Andile Zulu ◽  
...  
Keyword(s):  
Binding Energy ◽  
Symmetry Energy ◽  
Neutron Capture ◽  
Decay Rates ◽  
Heavy Elements ◽  
Capture Process ◽  
Atomic Nuclei ◽  
Radiative Neutron ◽  
Radiative Neutron Capture ◽  
Semi Empirical

Abstract The abundance of heavy elements above iron through the rapid neutron capture process or r-process is intimately related to the competition between neutron capture and $\beta$ decay rates, which ultimately depends on the binding energy of atomic nuclei. The well-known Bethe-Weizsacker semi-empirical mass formula describes the binding energy of ground states in nuclei with temperatures of T~0 MeV, where the nuclear symmetry energy saturates between 23-26 MeV. Here we find a larger saturation energy of ~30 MeV for nuclei at T~0.7-1.3 MeV, which corresponds to the typical temperatures where seed elements are created during the cooling down of the ejecta following neutron-star mergers and collapsars. This large symmetry energy yields a reduction of the binding energy per nucleon for neutron-rich nuclei; hence, the close in of the neutron dripline, where nuclei become unbound. This finding constrains exotic paths in the nucleosynthesis of heavy elements -- as supported by microscopic calculations of radiative neutron-capture rates -- and further supports the universal origin of heavy elements, as inferred from the abundances in extremely metal-poor stars and meteorites.

scholarly journals FERMION-BOSON CLASSIFICATION IN MICROCLUSTERS

2020 ◽  
Vol 2 ◽  
pp. 407
Author(s):  
G. S. Anagnostatos
Keyword(s):  
The Other ◽  
Magic Numbers ◽  
Central Potential ◽  
Atomic Nuclei ◽  
Other Hand ◽  
Alternative Approach ◽  
Valence Electrons ◽  
Quantum Clusters

Mlcroclusters composed of atoms with non delocallzed odd number of valence electrons possess the usual magic numbers for fermions in a central potential and those with an even number of valence electrons possess the magic numbers for bosons coming from the packing of atoms in nested icosahedral or octahedral or tetrahedral shells. On the other hand, mlcroclusters composed of atoms with delocallzed valence electrons, either with an odd or with an even number of electrons, exhibit electronic magic numbers (according to the jelllum model) but also magic numbers coming from the (same, as above) packings of their bosonlc ion cores. Finally, through the present work, an alternative approach to study atomic nuclei as quantum clusters appears possible and promising.

scholarly journals Modification of the nuclear landscape in the inverse problem framework using the generalized Bethe–Weizsäcker mass formula

2018 ◽  
Vol 27 (02) ◽  
pp. 1850015 ◽  
Author(s):  
S. Cht. Mavrodiev ◽  
M. A. Deliyergiyev
Keyword(s):  
Inverse Problem ◽  
Mass Formula ◽  
Maximum Deviation ◽  
Model Parameters ◽  
Magic Numbers ◽  
Systems Of Equations ◽  
Nonlinear Systems Of Equations ◽  
Nuclear Mass ◽  
Nuclear Masses ◽  
Semi Empirical

We formalized the nuclear mass problem in the inverse problem framework. This approach allows us to infer the underlying model parameters from experimental observation, rather than to predict the observations from the model parameters. The inverse problem was formulated for the numerically generalized semi-empirical mass formula of Bethe and von Weizsäcker. It was solved in a step-by-step way based on the AME2012 nuclear database. The established parametrization describes the measured nuclear masses of 2564 isotopes with a maximum deviation less than 2.6[Formula: see text]MeV, starting from the number of protons and number of neutrons equal to 1.The explicit form of unknown functions in the generalized mass formula was discovered in a step-by-step way using the modified least [Formula: see text] procedure, that realized in the algorithms which were developed by Lubomir Aleksandrov to solve the nonlinear systems of equations via the Gauss–Newton method, lets us to choose the better one between two functions with same [Formula: see text]. In the obtained generalized model, the corrections to the binding energy depend on nine proton (2, 8, 14, 20, 28, 50, 82, 108, 124) and ten neutron (2, 8, 14, 20, 28, 50, 82, 124, 152, 202) magic numbers as well on the asymptotic boundaries of their influence. The obtained results were compared with the predictions of other models.

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