Charged-particle branching ratios above the neutron threshold in F19 : Constraining N15 production in core-collapse supernovae

Background: Spatially correlated overabundances of N15 and O18 observed in some low-density graphite meteoritic grains have been connected to nucleosynthesis taking place the helium-burning shell during core-collapse supernovae. Two reactions which identified as important final abundances are F18(n,?)N15 F18(n,p)O18. The relative strengths F18(n,p)O18 depend sensitively on ?0 p0 decay branches from states above neutron threshold F19 addition other properties such spins, parities, widths. However, experimental data charged-particle decays these highly excited lacking or inconsistent. Purpose: We measure around F19. Method: experiments were performed using proton inelastic scattering LiF targets magnetic spectrographs. first experiment used high-resolution Q3D spectrograph at Munich constrain levels A second Orsay split-pole an array silicon detectors was order To Results: number along with their corresponding decays. state has proton-decay branch ground lies 68 keV (Ex=10.5 MeV) threshold. ?-particle neutron-unbound generally be much stronger than Conclusion:Neutron-unbound predominantly by emission, supporting role production Improved resonant-scattering reaction required able determine rates accurately.1 MoreReceived 10 July 2020Revised 5 October 2020Accepted 16 February 2021DOI:https://doi.org/10.1103/PhysRevC.103.035804©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasEnergy & level densitiesExplosive burningH He induced nuclear reactionsNuclear astrophysicsNucleon reactionsNucleosynthesis explosive environmentsProperties6 ? 19Nuclear Physics