Microscopic investigation of the ${}^8$Li($n,\gamma$)${}^9$Li reaction

Abstract

The ${}^8$Li($n,\gamma$)${}^9$Li reaction plays an important role in several astrophysics scenarios. It cannot be measured directly and indirect experiments have so far provided only cross section limits. Theoretical predictions differ by an order of magnitude. In this work we study the properties of ${}^9$Li bound states and low-lying resonances and calculate the ${}^8$Li($n,\gamma$)${}^9$Li cross section within the no-core shell model with continuum (NCSMC) with chiral nucleon-nucleon and three-nucleon interactions as the only input. The NCSMC is an ab initio method applicable to light nuclei that provides a unified description of bound and scattering states well suited to calculate low-energy nuclear scattering and reactions. Our calculations reproduce the experimentally known bound states as well as the lowest $5/2^{-}$ resonance of ${}^9$Li. We predict a $3/2^{-}$ spin-parity assignment for the resonance observed at 5.38 MeV. In addition to the a very narrow $7/2^{-}$ resonance corresponding presumably to the experimental 6.43 MeV state, we find several other broad low-lying resonances. Our calculated ${}^8$Li($n,\gamma$)${}^9$Li cross section is within the limits derived from the 1998 National Superconducting Cyclotron Laboratory Coulomb-dissociation experiment [Phys. Rev. C {\bf 57}, 959 (1998)]. However, it is higher than cross sections obtained in recent phenomenological studies. It is dominated by a direct E1 capture to the ground state with a resonant contribution at $\sim 0.2$ MeV due to E2/M1 radiation enhanced by the $5/2^{-}$ resonance.

12 pages, 9 figures, version accepted for publication

References in corpus (11)

• Chiral effective field theory and nuclear forces
• Similarity Renormalization Group for Nucleon-Nucleon Interactions
• Evolution of Nuclear Many-Body Forces with the Similarity Renormalization Group
• Unified ab initio approach to bound and unbound states: no-core shell model with continuum and its application to 7He
• Can Ab Initio Theory Explain the Phenomenon of Parity Inversion in ${}^{11}$Be?
• Unitary Correlation Operator Method and Similarity Renormalization Group: Connections and Differences
• The 8Li(d,p)9Li Reaction and the Astrophysical 8Li(n,g)9Li Reaction Rate
• Quantifying uncertainties in neutron-alpha scattering with chiral nucleon-nucleon and three-nucleon forces
• Neutron Transfer reactions induced by 8Li on 9Be
• Coulomb dissociation of 9Li and the rate of the 8Li(n,g)9Li reaction
• Observation of T=3/2 Isobaric Analog States in 9Be using p+8Li resonance scattering

Cited by in corpus (4)

• Ab initio informed evaluation of the radiative capture of protons on ${}^7$Be
• Gamow shell model description of the radiative capture reaction ${}^8$Li$(n,\gamma )$${}^9$Li
• Ab initio investigation of the ${}^7$Li($p,e^{+}{e}^{-}$)${}^8$Be process and the X17 boson
• Microscopic optical potentials from a Greens function approach