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

Abstract

Levels in 17O affect the astrophysical s-process in two opposite ways. The neutron production is enhanced by resonances in the 13C(alpha,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,gamma)17O reaction corresponding to levels in 17O with excitation energies of 4-5 MeV. The present work uses the 19F(d,alpha)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_s16 level close to the threshold of the 13C(alpha,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.