| Texto completo | |
| Autor(es): Mostrar menos - |
Adsley, P.
;
Hammache, F.
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de Sereville, N.
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Alcindor, V
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Assie, M.
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Beaumel, D.
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Chabot, M.
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Degerlier, M.
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Delafosse, C.
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Faestermann, T.
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Flavigny, F.
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Fox, S. P.
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Garg, R.
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Georgiadou, A.
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Gillespie, S. A.
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Guillot, J.
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Guimaraes, V
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Gottardo, A.
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Hertenberger, R.
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Kiener, J.
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Laird, A. M.
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Lefebvre-Schuhl, A.
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Matea, I
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Meyer, A.
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Mahgoub, M.
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Olivier, L.
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Perrot, L.
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Riley, J.
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Sivacek, I
;
Stefan, I
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Tatischeff, V
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Wirth, H-F
Número total de Autores: 32
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| Tipo de documento: | Artigo Científico |
| Fonte: | PHYSICAL REVIEW C; v. 103, n. 3, p. 13-pg., 2021-03-08. |
| Resumo | |
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) | |
| Processo FAPESP: | 14/14432-2 - Investigação espectroscópica de núcleos de interesse para astrofísica nuclear |
| Beneficiário: | Valdir Guimarães |
| Modalidade de apoio: | Bolsas no Exterior - Pesquisa |
| Processo FAPESP: | 16/50315-6 - Experimental study of nuclear reactions of astrophysical interest |
| Beneficiário: | Valdir Guimarães |
| Modalidade de apoio: | Auxílio à Pesquisa - Regular |