Broad levels in $^{17}$O and their relevance for the astrophysical s-process

TL;DR

This study refines the understanding of $^{17}$O energy levels, crucial for astrophysical s-process modeling, by measuring their properties more accurately using the $^{19}$F($d$,$eta$)$^{17}$O reaction, resolving previous discrepancies.

Contribution

It provides improved excitation energies and widths for $^{17}$O levels up to 8 MeV, clarifying their roles in the s-process and resolving prior measurement inconsistencies.

Findings

Enhanced precision in $^{17}$O level energies and widths.

Resolved discrepancies for the $1/2^+$ level near the reaction threshold.

Improved data for levels affecting neutron production in astrophysics.

Abstract

Levels in $^{17}$O affect the astrophysical s-process in two opposite ways. The neutron production is enhanced by resonances in the $^{13}$C($\alpha$,$n$)$^{16}$O reaction at excitation energies around 7 MeV in $^{17}$O, and the number of available neutrons is reduced by low-lying resonances in the $^{16}$O($n$,$\gamma$)$^{17}$O reaction corresponding to levels in $^{17}$O with excitation energies of $4-5$ MeV. The present work uses the $^{19}$F($d$,$\alpha$)$^{17}$O reaction to determine absolute widths of the relevant levels in $^{17}$O. 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 $^{13}$C($\alpha$,$n$)$^{16}$O reaction. In addition, improved excitation energies and widths are provided for several states in $^{17}$O up to excitation energies close to 8 MeV.