Single-neutron excitations in18N

Abstract

States in ${}^{18}$N have been populated in the neutron-adding $(d,p)$ reaction on the short-lived ${}^{17}$N beam. Previously observed levels, found in this work at excitation energies of 0.12(1) MeV and 0.74(1) MeV, have been identified as those expected from a proton $0{p}_{1/2}$ hole coupled to the ${}^{19}$O $5/{2}^{+}$ ground state. A new state at 1.17(2) MeV is consistent with the coupling of the $1/{2}^{\ensuremath{-}}$ proton-hole state to the excited $1/{2}^{+}$ state in ${}^{19}$O. Orbital angular momentum assignments and spectroscopic factors were determined from the measured angular distributions through a distorted wave Born approximation analysis. Systematics for the ${(0{d}_{5/2}1{s}_{1/2})}^{3}$ neutron configurations in the $N=11$ isotones, ${}^{17}$C, ${}^{18}$N, and ${}^{19}$O are discussed and comparisons to $p$-$sd$ shell-model calculations are made.