We have studied the one-neutron removal reactions of C18 at 81 MeV/nucleon and C19 at 68 MeV/nucleon on a liquid hydrogen target. Transverse-momentum distributions of the core fragments C17 and C18, and their partial cross sections, are measured using coincidences with the γ 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 C17 are well described by the CDCC calculations, and the agreement provides evidence for the spin-parity assignments of Jπ=1/2+ for the 0.21-MeV state and Jπ=5/2+ for the 0.33-MeV state in C17. The Jπ=(2,3)+ assignment for the 4.0-MeV state in C18 is obtained for the first time based on the momentum distribution of C18. 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.
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