Low-lying single-particle structure of 17C and the N = 14 sub-shell closure

Abstract The first investigation of the single-particle structure of the bound states of 17C, via the d ( 16 C , p ) transfer reaction, has been undertaken. The measured angular distributions confirm the spin-parity assignments of 1 / 2 + and 5 / 2 + for the excited states located at 217 and 335 keV, respectively. The spectroscopic factors deduced for these states exhibit a marked single-particle character, in agreement with shell model and particle-core model calculations, and combined with their near degeneracy in energy provide clear evidence for the absence of the N = 14 sub-shell closure. The very small spectroscopic factor found for the 3 / 2 + ground state is consistent with theoretical predictions and indicates that the ν 1 d 3 / 2 strength is carried by unbound states. With a dominant l = 0 valence neutron configuration and a very low separation energy, the 1 / 2 + excited state is a one-neutron halo candidate.