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تسجيل مستخدم جديدShell-model half-lives for r-process waiting point nuclei including first-forbidden contributions
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We have performed large-scale shell-model calculations of the half-lives and neutron-branching probabilities of the r-process waiting point nuclei at the magic neutron numbers N=50, 82, and 126. The calculations include contributions from allowed Gamow-Teller and first-forbidden transitions. We find good agreement with the measured half-lives for the N=50 nuclei with charge numbers Z=28-32 and for the N=82 nuclei 129Ag and 130Cd. The contribution of forbidden transitions reduce the half-lives of the N=126 waiting point nuclei significantly, while they have only a small effect on the half-lives of the N=50 and 82 r-process nuclei.
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We have performed shell-model calculations of the half-lives and neutron-branching probabilities of the r-process waiting point nuclei at the magic neutron number N=82. These new calculations use a larger model space than previous shell model studies
and an improved residual interaction which is adjusted to recent spectroscopic data around A=130. Our shell-model results give a good account of all experimentally known half-lives and $Q_beta$-values for the N=82 r-process waiting point nuclei. Our half-life predictions for the N=82 nuclei with Z=42--46 agree well with recent estimates based in the energy-density functional method.
We have performed large-scale shell-model calculations of the half-lives and neutron-branching probabilties of the r-process waiting point nuclei at the magic neutron number N=82. We find good agreement with the measured half-lives of 129Ag and 130Cd
. Our shell-model half-lives are noticeably shorter than those currently adopted in r-process simulations. Our calculation suggests that 130Cd is not produced in beta-flow equilibrium with the other N=82 isotones on the r-process path.
In the present work we calculate the allowed $beta^-$-decay half-lives of nuclei with $Z = 20 -30$ and N $leq$ 50 systematically under the framework of the nuclear shell model. A recent study shows that some nuclei in this region belong to the island
of inversion. We perform calculation for $fp$ shell nuclei using KB3G effective interaction. In the case of Ni, Cu, and Zn, we used JUN45 effective interaction. Theoretical results of $Q$ values, half-lives, excitation energies, log$ft$ values, and branching fractions are discussed and compared with the experimental data. In the Ni region, we also compared our calculated results with recent experimental data [Z. Y. Xu {it et al.}, emph{Phys. Rev. Lett.} textbf{113}, 032505, 2014]. Present results agree with the experimental data of half-lives in comparison to QRPA.
Heavy neutron-rich nuclei close to N=126 were produced by fragmentation of a 1 A GeV 208Pb beam at the FRS at GSI. The beta-decay half-lives of 8 nuclides have been determined. The comparison of the data with model calculations including an approach
based on the self-consistent ground-state description and continuum QRPA considering the Gamow-Teller and first-forbidden decays provide a first indication on the importance of first-forbidden transitions around A=195. The measured data indicate that the matter flow in the r-process to heavier fissioning nuclei is faster than previously expected.
New recent experimental $alpha$ decay half-lives have been compared with the results obtained from previously proposed formulas depending only on the mass and charge numbers of the $alpha$ emitter and the Q$alpha$ value. For the heaviest nuclei they
are also compared with calculations using the Density-Dependent M3Y (DDM3Y) effective interaction and the Viola-Seaborg-Sobiczewski (VSS) formulas. The correct agreement allows us to make predictions for the $alpha$ decay half-lives of other still unknown superheavy nuclei from these analytic formulas using the extrapolated Q$alpha$ of G. Audi, A. H. Wapstra, and C. Thibault [Nucl. Phys. A729, 337 (2003)].
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