One-neutron removal reactions ofC18andC19on a proton target

Abstract

We have studied the one-neutron removal reactions of $^{18}\mathrm{C}$ at 81 MeV/nucleon and $^{19}\mathrm{C}$ at 68 MeV/nucleon on a liquid hydrogen target. Transverse-momentum distributions of the core fragments $^{17}\mathrm{C}$ and $^{18}\mathrm{C}$, and their partial cross sections, are measured using coincidences with the $\ensuremath{\gamma}$ rays. These are compared to theoretical calculations based on the continuum-discretized coupled-channels (CDCC) method. We have found that the transverse-momentum distributions of $^{17}\mathrm{C}$ are well described by the CDCC calculations, and the agreement provides evidence for the spin-parity assignments of ${J}^{\ensuremath{\pi}}=1/{2}^{+}$ for the 0.21-MeV state and ${J}^{\ensuremath{\pi}}=5/{2}^{+}$ for the 0.33-MeV state in $^{17}\mathrm{C}$. The ${J}^{\ensuremath{\pi}}=(2,3){}^{+}$ assignment for the 4.0-MeV state in $^{18}\mathrm{C}$ is obtained for the first time based on the momentum distribution of $^{18}\mathrm{C}$. The measured partial cross sections are consistent with the CDCC calculations combined with shell-model spectroscopic factors. The present study demonstrates that the transverse-momentum distribution obtained in a one-neutron removal reaction on a proton target is as useful as the conventional longitudinal-momentum distribution measured with the heavier Be or C targets for determining the orbital angular momentum of a removed neutron.