Shell-model based study of the direct capture in neutron-rich nuclei

Abstract

The radiative neutron capture rates for isotopes of astrophysical interest are commonly calculated within the statistical Hauser-Feshbach reaction model. Such an approach, assuming a high level density in the compound system, can be questioned in light and neutron-rich nuclei for which only a few or no resonant states are available. Therefore, in this work we focus on the direct neutron-capture process. We employ a shell-model approach in several model spaces with well-established effective interactions to calculate spectra and spectroscopic factors in a set of 50 neutron-rich target nuclei in different mass regions, including doubly-, semi-magic and deformed ones. Those theoretical energies and spectroscopic factors are used to evaluate direct neutron capture rates and to test global theoretical models using average spectroscopic factors and level densities based on the Hartree-Fock-Bogoliubov plus combinatorial method. The comparison of shell-model and global model results reveals several discrepancies that can be related to problems in level densities. All the results show however that the direct capture is non-negligible with respect to the by-default Hauser-Feshbach predictions and can be even 100 times more important for the most neutron-rich nuclei close to the neutron drip line.

arXiv comment10 pages, 9 figures, submitted to EPJ A

References in corpus (22)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Modern Theory of Nuclear Forces
• The Shell Model as Unified View of Nuclear Structure
• The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries
• Comprehensive nucleosynthesis analysis for ejecta of compact binary mergers
• R-Process Nucleosynthesis in Dynamically Ejected Matter of Neutron Star Mergers
• Model-independent low momentum nucleon interaction from phase shift equivalence
• Collapse of the N=28 shell closure in ${}^{42}$Si
• Improved predictions of nuclear reaction rates with the TALYS reaction code for astrophysical applications
• A new effective interaction for $0\hslash \omega$ shell model calculations in the sdpf valence space
• ${}^{78}$Ni revealed as a doubly magic stronghold against nuclear deformation
• Impact of weak interactions of free nucleons on the r-process in dynamical ejecta from neutron-star mergers
• Astronuclear Physics: a Tale of the Atomic Nuclei in the Skies
• Prolate-Spherical Shape Coexistence at N=28 in ${}^{44}$S
• Direct radiative capture of p-wave neutrons
• How Robust is the N = 34 Subshell Closure? First Spectroscopy of ${}^{52}$Ar
• Improved Leakage-Equilibration-Absorption Scheme (ILEAS) for Neutrino Physics in Compact Object Mergers
• Discovery of a new isomeric state in ${}^{68}$Ni: Evidence for a highly-deformed proton intruder state
• Nuclear Structure Towards N=40 60Ca: In-beam gamma-ray Spectroscopy of 58,60Ti
• Time-of-flight mass measurements of neutron-rich chromium isotopes up to N = 40 and implications for the accreted neutron star crust
• Measurement of neutron capture on ${}^{48}$Ca at thermal and thermonuclear energies
• ${}^{35,37,39}$S isotopes in $sd-pf$ space : Shell-model interpretation

Cited by in corpus (9)

• The Science of the Einstein Telescope
• The intermediate neutron capture process II.Nuclear uncertainties
• Impact of systematic nuclear uncertainties on composition and decay heat of dynamical and disk ejecta in compact binary mergers
• Synthesis of thorium and uranium in asymptotic giant branch stars
• Impact of level densities and $\gamma$-strength functions on $r$-process simulations
• Shell-model study of ${\beta }^{+}$/EC-decay half-lives for $Z=21-30$ nuclei
• Benchmark of many-body approaches for magnetic dipole transition strength
• Continuum random-phase approximation for (n,γ) reactions on neutron-rich nuclei: collective effects and resonances
• Shell-model study of $\log ft$ values for ${}^{139,140,141}$Ba $\to$ ${}^{139,140,141}$La transitions