A COMPOSITE NUCLEAR-LEVEL DENSITY FORMULA WITH SHELL CORRECTIONS

1965 ◽  
Vol 43 (8) ◽  
pp. 1446-1496 ◽  
Author(s):  
A. Gilbert ◽  
A. G. W. Cameron
Keyword(s):  
Lower Energy ◽  
Level Density ◽  
Energy Levels ◽  
Fermi Gas ◽  
Experimental Information ◽  
Shell Correction ◽  
Nuclear Level Density ◽  
Excitation Energies ◽  
Nuclear Level ◽  
Level Densities

At low excitation energies a "constant nuclear temperature" representation of nuclear-level densities is used, and at high excitation energies the regular Fermi gas formula is adopted. A method is developed for determining the parameters of the Fermi gas formula by using both the pairing and the shell-correction energies found by Cameron and Elkin for their semiempirical atomic mass formula in its exponential form. This procedure determines level densities at neutron-binding-energy excitations subject to an average factor error of 1.8. Methods are also developed for determining the parameters for the lower-energy formula in such a way that it best fits the lower-energy levels and joins smoothly to the Fermi gas formula. Correlations of the resulting parameters with shell and pairing effects are found. A composite prescription is given for calculating level densities in nuclei for which no experimental information is known. Tables give level density parameters for a wide variety of nuclei for which some experimental information is known. Some of the derivations of the Fermi gas formula in the literature were found to be slightly incorrect, so new derivations are presented in Appendixes.

scholarly journals Level studies of 73As via 73Ge(p, nγ)73As reaction and density of discrete levels in 73As

2009 ◽  
Vol 24 (2) ◽  
pp. 82-85 ◽  
Author(s):  
Aziz Behkami ◽  
Rohallah Razavi ◽  
Tayeb Kakavand
Keyword(s):  
Proton Beam ◽  
Excited States ◽  
Level Scheme ◽  
Level Density ◽  
Fermi Gas ◽  
Temperature Model ◽  
Nuclear Level Density ◽  
Nuclear Level ◽  
Level Densities ◽  
Experimental Level

The excited states of 73As have been investigated via the 73Ge(p, n?)73As reaction with the proton beam energies from 2.5-4.3 MeV. The parameters of the nuclear level density formula have been determined from the extensive and complete level scheme for 73As. The Bethe formula for the back-shifted Fermi gas model and the constant temperature model are compared with the experimental level densities.

scholarly journals Level studies of 93Mo via 93Nb(p, nγ)93Mo reaction and density of discrete levels in 93Mo

2011 ◽  
Vol 26 (1) ◽  
pp. 69-73 ◽  
Author(s):  
Rohallah Razavi ◽  
Tayeb Kakavand
Keyword(s):  
Proton Beam ◽  
Excited States ◽  
Level Scheme ◽  
Level Density ◽  
Fermi Gas ◽  
Temperature Model ◽  
Nuclear Level Density ◽  
Nuclear Level ◽  
Level Densities ◽  
Experimental Level

The excited states of 93Mo have been investigated via the 93Nb(P,n?)93Mo reaction with proton beam energies of 2.5-4.3 MeV. The parameters of the nuclear level density formula were determined from the extensive and complete level scheme of 93Mo. The Bethe formula for the back-shifted Fermi gas model and the constant temperature model are compared with experimental level densities.

Studying Nuclear Level Densities of 238U in the Nuclear Reactions within the Macroscopic Nuclear Models

2016 ◽  
Vol 71 (2) ◽  
pp. 157-160
Author(s):  
Rohallah Razavi ◽  
Azam Rahmatinejad ◽  
Tayeb Kakavand ◽  
Fariba Taheri ◽  
Maghsood Aghajani ◽  
...  
Keyword(s):  
Constant Temperature ◽  
Nuclear Reactions ◽  
Level Density ◽  
Recent Experimental Data ◽  
Nuclear Level Density ◽  
Nuclear Level ◽  
Excitation Functions ◽  
Level Densities ◽  
Nuclear Models ◽  
Experimental Values

AbstractIn this work the nuclear level density parameters of 238U have been extracted in the back-shifted Fermi gas model (BSFGM), as well as the constant temperature model (CTM), through fitting with the recent experimental data on nuclear level densities measured by the Oslo group. The excitation functions for 238U(p,2nα)233Pa, and 238U(p,4n)235Np reactions and the fragment yields for the fragments of the 238U(p,f) reaction have been calculated using obtained level density parameters. The results are compared to their corresponding experimental values. It was found that the extracted excitation functions and the fragment yields in the CTM coincide well with the experimental values in the low-energy region. This finding is according to the claim made by the Oslo group that the extracted level densities of 238U show a constant temperature behaviour.

Nuclear shell model and level density

2020 ◽  
Vol 29 (06) ◽  
pp. 2030005
Author(s):  
S. Karampagia ◽  
V. Zelevinsky
Keyword(s):  
Shell Model ◽  
Level Density ◽  
Interaction Matrix ◽  
Model Description ◽  
Hamiltonian Matrix ◽  
Matrix Elements ◽  
Nuclear Level Density ◽  
Nuclear Level ◽  
Level Densities ◽  
Moments Method

The accurate knowledge of the nuclear level density is crucial for understanding the nuclear structure and for numerous applications including astrophysical reactions. In this review paper, we discuss the shell-model description of the nuclear level density, the use of the statistical moments method and underlying physics. The level density found with the moments method is shown to agree with the results of the exact diagonalization of the Hamiltonian matrix. The statistical approach is also compared to other standard methods for deriving level densities. The role of specific interaction matrix elements is reviewed in connection to the behavior of the level densities as these evolve. Chaotization and thermalization processes, collective enhancement and phase transitions are discussed with changing strengths of specific groups of two-body interaction matrix elements. The popular phenomenological constant temperature model is compared to the moments method and the effective temperature parameter of the model for different isotopes is discussed.

Back shifted Fermi gas model with temperature dependent pairing energy: Thermal properties of 98Mo

2016 ◽  
Vol 25 (09) ◽  
pp. 1650065
Author(s):  
S. A. Alavi ◽  
V. Dehghani
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Level Density ◽  
Fermi Gas ◽  
Nuclear Level Density ◽  
Temperature Dependent ◽  
Nuclear Level ◽  
Ginzburg Landau ◽  
The Mean ◽  
Good Agreement

The effect of using a temperature dependent pairing term in back-shifted Fermi-gas (BSFG) formula of nuclear level density has been studied. We have used the mean order parameter formula of modified Ginzburg–Landau (MGL) theory as a simple possible choice for temperature dependency of the pairing term. The level density and heat capacity of [Formula: see text]Mo have been calculated with this formalism and compared with the experimental data. We observed good agreement between the heat capacity of this model and the experimental data.

NUCLEAR LEVEL DENSITY AT FINITE TEMPERATURES

2006 ◽  
Vol 15 (02) ◽  
pp. 478-483 ◽  
Author(s):  
J. BARTEL ◽  
K. POMORSKI ◽  
B. NERLO-POMORSKA
Keyword(s):  
Single Particle ◽  
Level Density ◽  
Mean Field ◽  
Skyrme Force ◽  
Nuclear Level Density ◽  
Nuclear Level ◽  
Level Densities ◽  
Relativistic Mean Field ◽  
Single Particle Level ◽  
Particle Level

Selfconsistent mean-field calculations have been performed with the SkM* Skyrme force for 140 spherical even-even nuclei at temperatures 0≤T≤4 MeV . Single-particle level densities for this sample of nuclei are determined for various temperatures. The average dependence of the single-particle level density on mass number A and isospin is given and compared with previous estimates obtained using the relativistic mean-field and different semiclassical approaches.

scholarly journals The nuclear level density parameter

2019 ◽  
Vol 11 (20) ◽  
pp. 35-46
Author(s):  
Rasha S. Ahmed
Keyword(s):  
Level Density ◽  
State Density ◽  
Density Parameter ◽  
Nuclear Level Density ◽  
Excitation Energies ◽  
Nuclear Level ◽  
Level Density Parameter ◽  
Experimental Works ◽  
Experimental Values ◽  
Energy Dependent

The nuclear level density parameter  in non Equi-Spacing Model (NON-ESM), Equi-Spacing Model (ESM) and the Backshifted Energy Dependent Fermi Gas model (BSEDFG) was determined for 106 nuclei; the results are tabulated and compared with the experimental works. It was found that there are no recognizable differences between our results and the experimental -values. The calculated level density parameters have been used in computing the state density as a function of the excitation energies for 58Fe and 246Cm nuclei. The results are in a good agreement with the experimental results from earlier published work.

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