scholarly journals Microscopie Calculations of Nuclear Level Densities and Astrophysical Applications

2019 ◽  
Vol 11 ◽  
Author(s):  
P. Demetriou ◽  
S. Goriely
Keyword(s):  
Cross Sections ◽  
Level Density ◽  
Reaction Cross ◽  
Neutron Resonance ◽  
Thermodynamic Quantities ◽  
Microscopic Approach ◽  
Level Densities ◽  
Hartree Fock ◽  
The Impact ◽  
Reaction Cross Sections

A new level density formula based on a microscopic calculation of the thermodynamic quantities using the deformed Hartree-Fock-BCS method is proposed. In the microscopic approach shell, pairing and deformation effects on the thermodynamic quantities are treated consistently. The final level density formula is shown to be in close agreement with experimental neutron resonance spacings and low energy states. The impact of the newly-determined level densities on nuclear reaction cross sections and rates of relevance in astrophysics applications is presented.

scholarly journals Study of the photon strength functions and level density in the gamma decay of the n + 234U reaction

2019 ◽  
Vol 211 ◽  
pp. 02002 ◽  
Author(s):  
J. Moreno-Soto ◽  
E Berthoumieux ◽  
E Dupont ◽  
F Gunsing ◽  
O Serot ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Cross Sections ◽  
High Efficiency ◽  
Level Density ◽  
Reaction Cross ◽  
Level Densities ◽  
Strength Functions ◽  
Gamma Decay ◽  
Reaction Cross Sections ◽  
Nuclear Applications

The accurate calculations of neutron-induced reaction cross sections are relevant for many nuclear applications. The photon strength functions and nuclear level densities are essential inputs for such calculations. These quantities for 235U are studied using the measurement of the gamma de-excitation cascades in radiative capture on 234U with the Total Absorption Calorimeter at n_TOF at CERN. This segmented 4π gamma calorimeter is designed to detect gamma rays emitted from the nucleus with high efficiency. This experiment provides information on gamma multiplicity and gamma spectra that can be compared with numerical simulations. The code DICEBOXC is used to simulate the gamma cascades while GEANT4 is used for the simulation of the interaction of these gammas with the TAC materials. Available models and their parameters are being tested using the present data. Some preliminary results of this ongoing study are presented and discussed.

scholarly journals Calculations of (γ,n) Reaction Cross Sections using Different Level Density Models for Some Lanthanide Nuclei

2015 ◽  
Vol 128 (2B) ◽  
pp. B-228-B-231 ◽  
Author(s):  
U. Akçaalan ◽  
R. Ünal ◽  
İ.H. Sarpün ◽  
H.A. Yalim ◽  
B. Oruncak
Keyword(s):  
Cross Sections ◽  
Level Density ◽  
Reaction Cross ◽  
Level Density Models ◽  
Reaction Cross Sections

scholarly journals CROSS-SECTIONS IN PHOTONUCLEAR REACTIONS WITH MULTIPLE NEUTRON EMISSION

2019 ◽  
pp. 144-148
Author(s):  
O.A. Bezshyyko ◽  
O.M. Vodin ◽  
L.O. Golinka-Bezshyyko ◽  
A.V. Kotenko ◽  
V.A. Kushnir ◽  
...  
Keyword(s):  
Energy Dependence ◽  
Cross Sections ◽  
Neutron Emission ◽  
Reaction Cross ◽  
Photonuclear Reactions ◽  
Level Densities ◽  
Relative Contribution ◽  
Dipole Resonance ◽  
Talys 1.8 Code ◽  
Reaction Cross Sections

The energy dependence of the reaction cross-sections A(γ,xn)(A-xn) was studied in the energy range 19...70 MeV, i.e. beyond Great Dipole Resonance (GDR) region. Experimental data were taken from international database EXFOR for range of nuclear mases (55 < A < 209). Theoretical values of cross sections were obtained using TALYS-1.8 code. Several models of level densities with both enabled and disabled pre-equilibrium mechanism were considered in our simulations. Obtained results let us to make conclusions about different mechanisms of photonuclear reactions on certain nuclei, energy dependence of their relative contribution.

scholarly journals Statistical Hauser-Feshbach Model Description of (n,α) Reaction Cross Sections for the Weak s-Process

Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 25
Author(s):  
Sema Küçüksucu ◽  
Mustafa Yiğit ◽  
Nils Paar
Keyword(s):  
Cross Sections ◽  
Density Functional ◽  
Experimental Studies ◽  
Reaction Cross ◽  
Model Description ◽  
Energy Density Functional ◽  
Model Calculations ◽  
Level Densities ◽  
Environment Model ◽  
Reaction Cross Sections

The (n,α) reaction contributes in many processes of energy generation and nucleosynthesis in stellar environment. Since experimental data are available for a limited number of nuclei and in restricted energy ranges, at present only theoretical studies can provide predictions for all astrophysically relevant (n,α) reaction cross sections. The purpose of this work is to study (n,α) reaction cross sections for a set of nuclei contributing in the weak s-process nucleosynthesis. Theory framework is based on the statistical Hauser-Feshbach model implemented in TALYS code with nuclear masses and level densities based on Skyrme energy density functional. In addition to the analysis of the properties of calculated (n,α) cross sections, the Maxwellian averaged cross sections are described and analyzed for the range of temperatures in stellar environment. Model calculations determined astrophysically relevant energy windows in which (n,α) reactions occur in stars. In order to reduce the uncertainties in modeling (n,α) reaction cross sections for the s-process, novel experimental studies are called for. Presented results on the effective energy windows for (n,α) reaction in weak s-process provide a guidance for the priority energy ranges in the future experimental studies.

scholarly journals The effect of deformation parameter of heavy nuclei on level density parameter

2019 ◽  
Vol 12 (25) ◽  
pp. 38-43
Author(s):  
Mahdi Hadi Jasim
Keyword(s):  
Cross Sections ◽  
Collective Motion ◽  
Level Density ◽  
Reaction Cross ◽  
Neutron Resonance ◽  
Density Parameter ◽  
Heavy Nuclei ◽  
Nuclear Level Density ◽  
S Wave ◽  
Level Density Parameter

The possible effect of the collective motion in heavy nuclei has been investigated in the framework of Nilson model. This effect has been searched realistically by calculating the level density, which plays a significant role in the description of the reaction cross sections in the statistical nuclear theory. The nuclear level density parameter for some deformed radioisotopes of (even- even) target nuclei (Dy, W and Os) is calculated, by taking into consideration the collective motion for excitation modes for the observed nuclear spectra near the neutron binding energy. The method employed in the present work assumes equidistant spacing of the collective coupled state bands of the considered isotopes. The present calculated results for first excited rotational band have been compared with the accumulated values from the literature for s-wave neutron resonance data, and were in good agreement with those data.

scholarly journals Pygmy and giant resonances: connecting the nuclear structure to stellar astrophysics

2018 ◽  
Vol 194 ◽  
pp. 04001
Author(s):  
Nadia Tsoneva
Keyword(s):  
Cross Sections ◽  
Density Functional ◽  
Reaction Cross ◽  
Giant Resonances ◽  
Energy Density Functional ◽  
Theoretical Investigations ◽  
Dipole Response ◽  
The Impact ◽  
Reaction Cross Sections ◽  
Phonon Model

Systematic theoretical investigations of dipole response in neutron-rich nuclei of importance for day-one photonuclear experiments at ELI-NP are presented. The calculations are performed in advanced mi- croscopic theory based on energy-density functional and three-phonon quasiparticle-phonon model. The model basis accounts for a large range of nuclear excitations with different spin and parity. In the focus of the studies are electric and magnetic dipole modes with energies up to 25 MeV. Of special interest are pygmy dipole and giant dipole resonances. The impact of different low-energy excitations and in particular of the PDR on radia- tive neutron-capture reaction cross sections in nuclei of key importance for nucleosynthesis is investigated.The obtained results are compared to available experimental data.

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