Spectroscopy of neutron-unbound ${}^{27,28}$F

Abstract

The ground state of ${}^{28}$F has been observed as an unbound resonance $2\underline{2}0$ keV above the ground state of ${}^{27}$F. Comparison of this result with USDA/USDB shell model predictions leads to the conclusion that the ${}^{28}$F ground state is primarily dominated by $sd$-shell configurations. Here we present a detailed report on the experiment in which the ground state resonance of ${}^{28}$F was first observed. Additionally, we report the first observation of a neutron-unbound excited state in ${}^{27}$F at an excitation energy of $25\underline{0}0(2\underline{2}0)$ keV.

10 pages, 11 figures, Accepted for publication in Phys. Rev. C