Neutron-hole strength in N = 81 nuclei
A systematic study of neutron-hole strength in the N = 81 nuclei 137 Ba, 139 Ce, 141 Nd, and 143 Sm is reported. The single-neutron removal reactions (p,d) and ( 3 He,α) were measured at energies of 23 and 34 MeV, respectively. Spectroscopic factors were extracted from measured cross sections through a distorted-wave Born approximation analysis and centroids of single-particle strength have been established. Here, the change in these centroid energies as a function of proton number have been compared to calculations of the monopole shift for the s 1/2 and h 11/2 orbitals, where the majority of the strength has been observed. Significant fragmentation of strength was observed for the d and g 7/2 orbitals, particularly for the latter orbital which is deeply bound, with summed strengths that indicate a significant amount lies outside of the measured excitation energy range.