| Full text | |
| Author(s): Show less - |
Adsley, P.
;
Hammache, F.
;
de Sereville, N.
;
Alcindor, V
;
Assie, M.
;
Beaumel, D.
;
Chabot, M.
;
Degerlier, M.
;
Delafosse, C.
;
Faestermann, T.
;
Flavigny, F.
;
Fox, S. P.
;
Garg, R.
;
Georgiadou, A.
;
Gillespie, S. A.
;
Guillot, J.
;
Guimaraes, V
;
Gottardo, A.
;
Hertenberger, R.
;
Kiener, J.
;
Laird, A. M.
;
Lefebvre-Schuhl, A.
;
Matea, I
;
Meyer, A.
;
Mahgoub, M.
;
Olivier, L.
;
Perrot, L.
;
Riley, J.
;
Sivacek, I
;
Stefan, I
;
Tatischeff, V
;
Wirth, H-F
Total Authors: 32
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| Document type: | Journal article |
| Source: | PHYSICAL REVIEW C; v. 103, n. 3, p. 13-pg., 2021-03-08. |
| Abstract | |
Background: Spatially correlated overabundances of N-15 and O-18 observed in some low-density graphite meteoritic grains have been connected to nucleosynthesis taking place in the helium-burning shell during core-collapse supernovae. Two of the reactions which have been identified as important to the final abundances of N-15 and O-18 are F-18(n, alpha) N-15 and F-18(n, p) O-18. The relative strengths of the F-18(n, alpha) N-15 and F-18(n, p) O-18 reactions depend sensitively on the relative alpha(0) and p(0) decay branches from states above the neutron threshold in F-19 in addition to other properties such as the spins, parities, and neutron widths. However, experimental data on the charged-particle decays from these highly excited states are lacking or inconsistent. Purpose: We measure the charged-particle decay branches from states around the neutron threshold in F-19. Method: Two experiments were performed using proton inelastic scattering from LiF targets and magnetic spectrographs. The first experiment used the high-resolution Q3D spectrograph at Munich to constrain the properties of levels in F-19. A second experiment using the Orsay split-pole spectrograph and an array of silicon detectors was performed in order To measure the charged-particle decay branches from states around the neutron threshold in F-19. Results: A number of levels in F-19 have been identified along with their corresponding charged-particle decays. The first state above the neutron threshold which has an observed proton-decay branch to the ground state of O-18 lies 68 keV (E-x = 10.5 MeV) above the neutron threshold. The alpha-particle decays from the neutron-unbound levels are generally observed to be much stronger than the proton decays. Conclusion:Neutron-unbound levels in F-19 are observed to decay predominantly by a-particle emission, supporting the role of F-18(n, alpha) N-15 in the production of N-15 in the helium-burning shell of supernovae. Improved resonant-scattering reaction data are required in order to be able to determine the reaction rates accurately. (AU) | |
| FAPESP's process: | 14/14432-2 - Spectroscopic investigation of nuclei for nuclear astrophysics |
| Grantee: | Valdir Guimarães |
| Support Opportunities: | Scholarships abroad - Research |
| FAPESP's process: | 16/50315-6 - Experimental study of nuclear reactions of astrophysical interest |
| Grantee: | Valdir Guimarães |
| Support Opportunities: | Regular Research Grants |