Position of the single-particle 3/2− state in 135Sn and the N=90 subshell closure

• Published in: Physics letters. B 2024-04, Vol.851, p.138561, Article 138561
• Main Authors: Jungclaus, A., Doornenbal, P., Acosta, J., Vaquero, V., Browne, F., Cortes, M.L., Gargano, A., Koiwai, T., Naïdja, H., Taniuchi, R., Tostevin, J.A., Wimmer, K., Algora, A., Baba, H., Fernández, A., Lalović, N., Nácher, E., Rubio, B., Sakurai, H.
• Format: Article
• Language: English
• Subjects: Fysik; Natural Sciences; Naturvetenskap; Physical Sciences; Subatomic Physics; Subatomär fysik
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/j.physletb.2024.138561

The decay of excited states of the nucleus 135Sn, with three neutrons outside the doubly-magic 132Sn core, was studied in an experiment performed at the Radioactive Isotope Beam Factory at RIKEN. Several γ rays emitted from excited 135Sn ions were observed following one-neutron and one-neutron-one-proton removal from 136Sn and 137Sb beams, respectively, on a beryllium target at relativistic energies. Based on the analogy to 133Sn populated via one-neutron removal from 134Sn, an excitation energy of 695(15) keV is assigned to the 3/2− state with strongest single-particle character in 135Sn. This result provides the first direct information about the evolution of the neutron shell structure beyond N=82 and thus allows for a crucial test of shell-model calculations in this region. The experimental findings are in full agreement with calculations performed employing microscopic effective two-body interactions derived from CD-Bonn and N3LO nucleon-nucleon potentials, which do not predict a pronounced subshell gap at neutron number N=90. The occurrence of such a gap in 140Sn, i.e., when the 1f7/2 orbital is completely filled, had been proposed in the past, in analogy to the magicity of 48Ca, featuring a completely filled 0f7/2 orbital one harmonic oscillator shell below.