Semi-empirical interpretation of nuclear fission based on deformed-shell effects

1972 ◽  
Vol 42 (2) ◽  
pp. 141-145 ◽  
Author(s):  
B.D. Wilkins ◽  
E.P. Steinberg
Keyword(s):  
Nuclear Fission ◽  
Shell Effects ◽  
Semi Empirical ◽  
Empirical Interpretation

scholarly journals Shells, Anti-Shells and Modes in nuclear Fission

2018 ◽  
Vol 193 ◽  
pp. 01001
Author(s):  
Friedrich Gönnenwein
Keyword(s):  
Liquid Drop ◽  
Nuclear Fission ◽  
Angular Distributions ◽  
Special Issue ◽  
Shell Effects ◽  
Present Purpose ◽  
Charge Stability ◽  
Characteristic Features

Fission phenomena are surveyed where fragment properties are catching the eye. Beyond the Liquid Drop the relevant properties of fragments are shell effects and nuclear pairing. Shell effects influence on mass, charge, stability and deformability of fragments. Most often only the stabilizing effects of shells are discussed and the equally frequent destabilizing effects are not mentioned. For the present purpose the terms shells and anti-shells are used in case of stabilizing and destabilizing effects, respectively. Fragment shells and anti-shells lead to fission modes with characteristic properties. A special issue is where in the course of fission these modes assume their characteristic features. Surprisingly fragment angular distributions in above- and sub-barrier fission help elucidating this question. The discussion is focussed on fission in the standard actinides.

VIII.—An Objective Criterion of the Limit of Useful Sophistication of the Semi-empirical Mass Equation

1965 ◽  
Vol 67 (2) ◽  
pp. 104-125
Author(s):  
N. Feather
Keyword(s):  
Roughness Parameter ◽  
Objective Criterion ◽  
Charge Number ◽  
Shell Effects ◽  
Unit Structure ◽  
Semi Empirical

SynopsisA “roughness parameter”, first used by the author in 1953 (Feather 1953 b) has been re-calculated for 348 points on the mass surface. Systematic features are identified in relation to the variation of this parameter with charge number (Z) and isotopie number (D). In the region of small Z these regularities provide evidence for the persistence of some degree of alpha-unit structure at least as far as Ca. In the region of greater Z (20 < Z < 50) they provide evidence for neutron-proton interactions among the last-added nucleons. Overall, they indicate that the “residuals” characterizing the various semi-empirical mass equations currently in use very probably arise in large part from sub-shell effects which it would be impracticable to attempt to include in the equations.

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.

scholarly journals Microscopic Calculations of Low and Medium Energy Fission with the CoMD (Constrained Molecular Dynamics) Model

2019 ◽  
Vol 22 ◽  
pp. 67
Author(s):  
N. Vonta ◽  
G. A. Souliotis ◽  
A. Bonasera ◽  
M. Veselsky
Keyword(s):  
Effective Interaction ◽  
Quantitative Description ◽  
Pauli Principle ◽  
Nuclear Fission ◽  
Intermediate Energy ◽  
Recent Experimental Data ◽  
Fission Reactions ◽  
Many Body ◽  
Time Step ◽  
Shell Effects

The investigation of the mechanism of nuclear fission is a topic of current experimental and theoretical interest. In this work, we initiated a systematic study of low and intermediate energy fission calculations using the Constrained Molecular Dynami cs (CoMD) code. The code implements an effective interaction with a soft isoscalar part and with several forms of the density dependence of the nucleon symmetry potential. In addition, CoMD imposes a constraint in the phase space occupation for each nucleon restoring the Pauli principle at each time step of the evolution of the nuclear system. Proper choice of the surface parameter of the effective interaction has been made to describe fission. In this work, we present CoMD calculations for several proton- included fission reactions at low and intermediate energy and compare them with recent experimental data. We found that the CoMD code is able to describe the complicated many-body dynamics of the fission process especially for intermediate and higher-energy fission reactions. Proper adjustment of the parameters of the effective interaction and further improvements of the code are necessary to achieve a satisfactory quantitative description of low-energy fission where shell effects play a definitive role.

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