Abstract
18 O ( p, γ ) 19 F plays an important role in the AGB star scenarios. The low energy cross section could be influenced by a hypothetical low energy resonance at 95 keV and by the tails of the higher energy broad states. The 95 keV resonance lies in the energy window corresponding to the relevant stellar temperature range of 40-50 MK.Measurements of the direct cross section were performed at the Laboratory for Underground Nuclear Astrophysics (LUNA), including the unobserved low energy resonance, the higher energy resonances and the non-resonant component, taking advantage of the extremely low environmental background. Here we report on the experimental setup and the status of the analysis.
Highlights
The 18O(p, γ)19F reaction (Q 7.99 MeV) represents the bridge between the CNO cycle and other cycles involved in the production of heavier nuclei, which are active during shell H burning
It has been suggested that the low-mass asymptotic giant branch (AGB) stars are an 18O depletion site [3] due to cool bottom processing (CBP) [2], in which the 18O + p reaction occurs
Within the CBP temperature regime (40 MK), the 18O(p, γ)19F reaction rate may be influenced by an unobserved low-energy resonance at Eres = 95 ± 3 keV, that corresponds to the EX=8084 keV±3 keV [4] level in the 19F nucleus
Summary
The 18O(p, γ)19F reaction (Q 7.99 MeV) represents the bridge between the CNO cycle and other cycles involved in the production of heavier nuclei, which are active during shell H burning. It has been suggested that the low-mass asymptotic giant branch (AGB) stars are an 18O depletion site [3] due to cool bottom processing (CBP) [2], in which the 18O + p reaction occurs. Within the CBP temperature regime (40 MK), the 18O(p, γ)19F reaction rate may be influenced by an unobserved low-energy resonance at Eres = 95 ± 3 keV, that corresponds to the EX=8084 keV±3 keV [4] level in the 19F nucleus. Further measurements regarding the off-resonant and on-resonant higher energy range, were done in order to improve our knowledge of levels in the 19F compound nucleus that are relevant to nuclear astrophysics and to complete available data known in literature [7], [8], [9]
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