Abstract
The photon strength functions (PSF), neutron capture cross sections and average radiative widths of neutron resonances for three double-magic nuclei 56 Ni, 132 Sn and 208 Pb have been calculated within the self-consistent version of the microscopic theory. Our approach includes phonon coupling (PC) effects in addition to the standard QRPA approach. With our microscopic PSFs, calculations of radiative nuclear reaction characteristics have been performed using the EMPIRE 3.1 nuclear reaction code. Three nuclear level density (NLD) models have been used: the phenomenological so-called GSM, phenomenological Enhanced GSM (EGSM) and microscopical combinatorial HFB model. For all the considered characteristics, we found a noticeable contribution of the PC effects and a significant disagreement between the results obtained with the GSM and the other two NLD models. The results confirm the necessity of using consistent microscopic approaches for calculations of radiative nuclear characteristics in double-magic nuclei.
Highlights
The microscopic approach in the nuclear theory accounts for the specificity of each nucleus through its singleparticle and collective spectra
The double magic nuclei were always a polygon for nuclear theory in low-lying nuclear physics. They have a noticeable specificity caused by the specificity of their single-particle and collective spectra, which determine their individual properties in many fields of low-energy nuclear physics
Since 2006 [1] it has been realized by the nuclear data society that there are structures in the photon strength functions (PSF) negating the simple picture based on the dominance of the generalized Lorentzian dependencies, especially in the energy region below neutron threshold
Summary
The microscopic approach in the nuclear theory accounts for the specificity of each nucleus through its singleparticle and collective (phonon) spectra. Since 2006 [1] it has been realized by the nuclear data society that there are structures in the PSFs negating the simple picture based on the dominance of the generalized Lorentzian dependencies, especially in the energy region below neutron threshold (for photoabsorption cross sections it was discussed within the quasiparticle-phonon model [3]) For this reason, meanfield approaches using effective nucleon interactions, such as the Hartree-Fock-Bogolubov method and the quasiparticle random-phase approximation (HFB+QRPA) [4], have been included in modern nuclear reaction codes like EMPIRE or TALYS. The calculations of PSF have been performed within the selfconsistent version of the extended theory of finite fermi systems in the quasiparticle time blocking approximation (ETFFS(QTBA)) [8, 9] This approach includes the QRPA and PC effects and uses the known Skyrme forces to calculate the mean field, effective interaction and phonon characteristics self-consistently. Our main aims are to study the PSF structures and role of the PC effects in these characteristics for these nuclei
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