The first-forbidden decays near the r-process paths at N=50, 82, 126

In addition to numerous problems in the quest of the astrophysical site for the r-process, nuclear physics uncertainties of the r-process modeling are still high. For the β-decay rates predictions, they stem mostly from non self-consistency of the nuclear models. Also, the sole consideration of the allowed β-decay commonly used in large-scale microscopic schemes needs to be revised. The first systematic study of the GT and first-forbidden β-decays near the closed neutron shells at N=50, S2, 126 was performed in the self-consistent, EDF+CQRPA approach. The importance of the first-forbidden decays for Z≥50, N ≈ 82 nuclei and near N=126 closed shell is shown.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Gamow-teller and first-forbidden decays near the r-process paths at N = 50, 82, and 126

The β-decay rates of neutron-rich nuclei relevant to the r-process nucleosynthesis are mostly beyond experimental reach. Their predictions demand a self-consistent extrapolation of various nuclear properties away from the experimentally known regions. The allowed transitions approximation commonly used in large-scale microscopic calculations also needs to be revised in different mass regions. The density functional+continuum QRPA approximation to self-consistent calculations of the ground state properties, Gamow-Teller and first-forbidden β-decay transitions of nuclei far from stability is developed. Systematic calculations are performed of the allowed and first-forbidden β-decay rates for the r-process relevant nuclides near the closed neutron shells at N = 50,82,126. The importance of first-forbidden decays near Z≥50, N≈82 and near N = 126 is shown. The total β-decay half-lives in the region "east" of the 208Pb are estimated. A comparison with recent experimental data, global calculations, and self-consistent microscopic predictions is presented.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Weak interaction processes in stars

Major astrophysical applications involve a huge number of exotic nuclei. An important effort has been devoted during the last decades to the measurements of the masses and β-decay rates of very neutron-rich nuclei at RIB facilities. However, most of them cannot be synthesised in terrestrial laboratories and only theoretical predictions can fill the gap. We concentrate mainly on the β-decay rates needed for the stellar r-process modeling and for performing the RIB experiments. The continuum QRPA approach based on the self-consistent ground state description in the framework of the density functional theory is briefly described. The model for the large-scale calculations of total β-decay half-lives accounts for the Gamow-Teller and first-forbidden transitions. Due to the shell configuration effect, the first-forbidden decays have a strong impact on the total half-lives of the r-process relevant nuclei at N=126, Z=60-70. The performance of existing global models for the nuclides near the r-process paths at N=126 is critically analyzed and confronted with the recent RIB experiments in the region "east" of 208Pb. The possible role of neutrino nucleosynthesis is exemplified by the production of rare isotope 138La via the neutrino process.SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Beta-decay rates

Major astrophysical applications involve a huge number of exotic nuclei. Their beta-decay properties play a crucial role in stellar explosive events. An important effort has been developed in last decades to measure the masses and β-decay properties of very neutron-rich nuclei at radioactive nuclear beam facilities. However, most of them cannot be synthesized in terrestrial laboratories and only theoretical predictions can fill the gap. We will concentrate mainly on the β-decay rates needed for stellar r-process modeling and for performing the RNB experiments. An overview of the microscopic approaches to the β-decay strength function is given. The continuum QRPA approach based on the self-consistent ground state description in the framework of the density functional theory is outlined. For the first time, a systematic study of the total β-decay half-lives and delayed neutron emission probabilities takes into account the Gamow-Teller and first-forbidden transitions. Due to the shell configuration effects, the first-forbidden decays have a strong impact on the β-decay characteristics of the r-process relevant nuclei at Z ≈ 28, N > 50; Z ≥ 50, N > 82 and Z = 60 - 70, N ≈ 126. Suppression of the delayed neutron emission probability is found in nuclei with the neutron excess bigger than one major shell. The effect originates from the high-energy first-forbidden transitions to the states outside the (Qβ - Bn)-window in the daughter nuclei. The performance of existing global models for the nuclides near the r-process paths is critically analyzed and confronted with the recent RIB experiments in the regions of 78Ni, 132Sn and "east" of 208Pb. © 2005 Elsevier B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Delayed neutron emission near the shell-closures

The self-consistent Density Functional + Continuum QRPA approach (DF+CQRPA) provides a good description of the recent experimental beta-decay half-lives and delayed neutron emission branchings for the nuclei approaching to (and beyond) the neutron closed shells N = 28; 50; 82. Predictions of beta-decay properties are more reliable than the ones of standard global approaches traditionally used for the r-process modelling. An impact of the quasi-particle phonon coupling on the delayed multi-neutron emission rates P2n, P3n,… near the closed shells is also discussed

Weak interaction rates for astrophysical applications

An important effort has been developed in recent decades to measure the masses and β-decay rates of very neutron-rich nuclei at radioactive ion beam (RIB) facilities. However, major astrophysical applications involve a huge number of exotic species. Most of them cannot be synthesized in terrestrial laboratories and only theoretical predictions can fill the gap. We concentrate on the self-consistent predictions of the β-decay rates needed for stellar r-process modeling and for performing the RIB experiments. The continuum QRPA approach based on the self-consistent ground-state description in the framework of the density functional theory is briefly described. The model for the large-scale calculations of total β-decay half-lives accounts for the Gamow-Teller and first-forbidden transitions. Due to the shell configuration effect, the first-forbidden decays have a strong impact on the total half-lives of the r-process relevant nuclei at N = 126, Z = 60-70. The performance of existing global models for the nuclides near the r-process paths at N = 126 is critically analyzed and confronted with the recent RIB experiments in the region "east" of 208Pb. © 2004 MAIK "Nauka/ Interperiodica".SCOPUS: cp.jinfo:eu-repo/semantics/publishe

Microscopic Nuclear Models and Nuclear Data for Astrophysics

SCOPUS: re.jinfo:eu-repo/semantics/publishe

Weak interaction rates of neutron-rich nuclei and the r-process nucleosynthesis

Weak interaction rates for very short-lived neutron-rich nuclides involved in the r process are mostly beyond the experimental reach at the present time. Accurate theoretical predictions demand a coherent extrapolation of different nuclear properties away from the experimentally known regions. The β-decay and neutrino-capture rates are estimated within the extended Thomas-Fermi plus Strutinsky integral method and the continuum quasiparticle random phase approximation. This approximation on the self-consistent calculation of the ground-state and β-decay properties is described. The large-scale calculations of the β-strength function for stable and short-lived nuclei are performed to estimate, simultaneously, the β-decay and electron neutrino capture rates for nuclides of relevance to the r-process nucleosynthesis. A comparison of the results with existing experimental data, global calculations, and self-consistent microscopic predictions is presented. © 2000 The American Physical Society.SCOPUS: ar.jSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Microscopic calculations of β-decay characteristics near the A=130 r-process peak

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Ground state properties and β-decay half-lives near 132Sn in a self-consistent theory

The self-consistent finite Fermi-system theory with three different parameter sets is used to calculate decay energies and Gamow-Teller strength distributions of neutron-rich short-lived nuclides near shell closures Z=50, N=82. Among the parameters, the role of a strong surface neutronproton attraction and an isovector spin-orbit force is discussed. The obtained β-decay half-lives are compared with large-scale calculation results and with available experimental data. Some predictions for the ground state properties of other unstable closed-shell nuclei are presented. © 1974, Springer-Verlag. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe