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Title: On microscopic theory of radiative nuclear reaction characteristics

Abstract

A survey of some results in the modern microscopic theory of properties of nuclear reactions with gamma rays is given. First of all, we discuss the impact of Phonon Coupling (PC) on the Photon Strength Function (PSF) because it represents the most natural physical source of additional strength found for Sn isotopes in recent experiments that could not be explained within the standard HFB + QRPA approach. The self-consistent version of the Extended Theory of Finite Fermi Systems in the Quasiparticle Time Blocking Approximation is applied. It uses the HFB mean field and includes both the QRPA and PC effects on the basis of the SLy4 Skyrme force. With our microscopic E1 PSFs, the following properties have been calculated for many stable and unstable even–even semi-magic Sn and Ni isotopes as well as for double-magic {sup 132}Sn and {sup 208}Pb using the reaction codes EMPIRE and TALYS with several Nuclear Level Density (NLD) models: (1) the neutron capture cross sections; (2) the corresponding neutron capture gamma spectra; (3) the average radiative widths of neutron resonances. In all the properties considered, the PC contribution turned out to be significant, as compared with the standard QRPA one, and necessary to explain themore » available experimental data. The results with the phenomenological so-called generalized superfluid NLD model turned out to be worse, on the whole, than those obtained with the microscopic HFB + combinatorial NLD model. The very topical question about the M1 resonance contribution to PSFs is also discussed.Finally, we also discuss the modern microscopic NLD models based on the self-consistent HFB method and show their relevance to explain the experimental data as compared with the phenomenological models. The use of these self-consistent microscopic approaches is of particular relevance for nuclear astrophysics, but also for the study of double-magic nuclei.« less

Authors:
 [1]; ;  [2];  [3]
  1. National Research Centre “Kurchatov Institute” (Russian Federation)
  2. Institute for Physics and Power Engineering (Russian Federation)
  3. Institut d’Astronomie et d’Astrophysique (Belgium)
Publication Date:
OSTI Identifier:
22612639
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Atomic Nuclei; Journal Volume: 79; Journal Issue: 4; Other Information: Copyright (c) 2016 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 74 ATOMIC AND MOLECULAR PHYSICS; CAPTURE; CROSS SECTIONS; ENERGY-LEVEL DENSITY; EXPERIMENTAL DATA; GAMMA RADIATION; GAMMA SPECTRA; LEAD 208; MAGIC NUCLEI; MEAN-FIELD THEORY; NEUTRON REACTIONS; NICKEL ISOTOPES; PHONONS; PHOTONS; RESONANCE; SKYRME POTENTIAL; STRENGTH FUNCTIONS; TIN 132

Citation Formats

Kamerdzhiev, S. P., Achakovskiy, O. I., E-mail: oachakovskiy@ippe.ru, Avdeenkov, A. V., and Goriely, S. On microscopic theory of radiative nuclear reaction characteristics. United States: N. p., 2016. Web. doi:10.1134/S106377881604013X.
Kamerdzhiev, S. P., Achakovskiy, O. I., E-mail: oachakovskiy@ippe.ru, Avdeenkov, A. V., & Goriely, S. On microscopic theory of radiative nuclear reaction characteristics. United States. doi:10.1134/S106377881604013X.
Kamerdzhiev, S. P., Achakovskiy, O. I., E-mail: oachakovskiy@ippe.ru, Avdeenkov, A. V., and Goriely, S. 2016. "On microscopic theory of radiative nuclear reaction characteristics". United States. doi:10.1134/S106377881604013X.
@article{osti_22612639,
title = {On microscopic theory of radiative nuclear reaction characteristics},
author = {Kamerdzhiev, S. P. and Achakovskiy, O. I., E-mail: oachakovskiy@ippe.ru and Avdeenkov, A. V. and Goriely, S.},
abstractNote = {A survey of some results in the modern microscopic theory of properties of nuclear reactions with gamma rays is given. First of all, we discuss the impact of Phonon Coupling (PC) on the Photon Strength Function (PSF) because it represents the most natural physical source of additional strength found for Sn isotopes in recent experiments that could not be explained within the standard HFB + QRPA approach. The self-consistent version of the Extended Theory of Finite Fermi Systems in the Quasiparticle Time Blocking Approximation is applied. It uses the HFB mean field and includes both the QRPA and PC effects on the basis of the SLy4 Skyrme force. With our microscopic E1 PSFs, the following properties have been calculated for many stable and unstable even–even semi-magic Sn and Ni isotopes as well as for double-magic {sup 132}Sn and {sup 208}Pb using the reaction codes EMPIRE and TALYS with several Nuclear Level Density (NLD) models: (1) the neutron capture cross sections; (2) the corresponding neutron capture gamma spectra; (3) the average radiative widths of neutron resonances. In all the properties considered, the PC contribution turned out to be significant, as compared with the standard QRPA one, and necessary to explain the available experimental data. The results with the phenomenological so-called generalized superfluid NLD model turned out to be worse, on the whole, than those obtained with the microscopic HFB + combinatorial NLD model. The very topical question about the M1 resonance contribution to PSFs is also discussed.Finally, we also discuss the modern microscopic NLD models based on the self-consistent HFB method and show their relevance to explain the experimental data as compared with the phenomenological models. The use of these self-consistent microscopic approaches is of particular relevance for nuclear astrophysics, but also for the study of double-magic nuclei.},
doi = {10.1134/S106377881604013X},
journal = {Physics of Atomic Nuclei},
number = 4,
volume = 79,
place = {United States},
year = 2016,
month = 7
}
  • A microscopic theory of the structure of four-particle hypernuclei and of the /sup 4//sub ..lambda../ /sup 4/H..--> pi../sup -/+/sup 4/He reaction is worked out using the method of hyperspherical functions in the momentum representation. The scheme of construction of symmetrized hyperspherical functions for systems of three identical particles and a particle with different mass is presented. It is shown that with the well-known relatively smooth potentials of the N and NN interactions one obtains good convergence in the number of included harmonics for both the binding energy and the life-time of the hypernucleus. A satisfactory agreement with existing experimental datamore » is found for these characteristics of four-particle hypernuclei.« less
  • The generator-coordinate method is applied to the study of the three-..cap alpha..-particle system. The choice of the basis functions allows us to calculate the ..cap alpha..+ /sup 8/Be phase shifts. We perform a comparison between the full three-cluster approach and two of its approximations. Distortion effects are shown to be important in the spectroscopic properties of /sup 12/C. We present the /sup 8/Be(..cap alpha..,..gamma..) /sup 12/C S factor derived in the three-..cap alpha..-particle model. At low temperatures, the reaction rate is found to be slightly different from earlier studies.
  • Important effort has been devoted in the last decades to measuring reaction cross sections. Despite such effort, many nuclear applications still require the use of theoretical predictions to estimate experimentally unknown cross sections. Most of the nuclear ingredients in the calculations of reaction cross sections need to be extrapolated in an energy and/or mass domain out of reach of laboratory simulations. In addition, some applications often involve a large number of unstable nuclei, so that only global approaches can be used. For these reasons, when the nuclear ingredients to the reaction models cannot be determined from experimental data, it ismore » highly recommended to consider preferentially microscopic or semi-microscopic global predictions based on sound and reliable nuclear models which, in turn, can compete with more phenomenological highly-parameterized models in the reproduction of experimental data. The latest developments made in deriving such microscopic models for practical applications are reviewed. It mainly concerns nuclear structure properties (masses, deformations, radii, etc.), level densities at the equilibrium deformation, {gamma}-ray strength, as well as fission barriers and level densities at the fission saddle points.« less
  • We give an action integral L (x,X,A/sub ..mu../,..cap alpha../sub ..mu../). The stability of L against the variations deltaA/sub ..mu../(xi), delta..cap alpha../sub ..mu../(xi), deltax/sub ..mu../(theta), and deltaX/sub ..mu../(tau) gives us the coupled Maxwell equations and the Lorentz-Dirac equation for the positron and monopole.