Broad levels in O 17 and their relevance for the astrophysical s process

Faestermann, T. and Mohr, Péter and Hertenberger, R. and Wirth, H.-F. (2015) Broad levels in O 17 and their relevance for the astrophysical s process. PHYSICAL REVIEW C, 92 (5). ISSN 2469-9985

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Abstract

Levels in 17O affect the astrophysical s-process in two opposite ways. The neutron production is enhanced by resonances in the 13C(α,n) 16O reaction at excitation energies around 7 MeV in 17O, and the number of available neutrons is reduced by low-lying resonances in the 16O(n,γ) 17O reaction corresponding to levels in 17O with excitation energies of 4−5MeV. The present work uses the 19F(d,α) 17O reaction to determine absolute widths of the relevant levels in 17O. The results improve the uncertainties of the previously adopted values and resolve a discrepancy between recent studies for the 1/2 + level close to the threshold of the 13C(α,n) 16O reaction. In addition, improved excitation energies and widths are provided for several states in 17O up to excitation energies close to 8 MeV.

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