Neutron-hole states in 131Sn and spin-orbit splitting in neutron-rich nuclei

Journal Article · Mon Oct 01 00:00:00 EDT 2018 · Physics Letters B

DOI:https://doi.org/10.1016/j.physletb.2018.08.005· OSTI ID:1463203

Orlandi, R.; Pain, S. D. ; Ahn, S.; Jungclaus, A.; Schmitt, K. T.; Bardayan, D. W.; Catford, W. N. ; Chapman, R.; Chipps, K. A.; Cizewski, J. A.; Gross, C. G.; Howard, M. E.; Jones, K. L.; Kozub, R. L.; Manning, B.; Matos, M.; Nishio, K.; O' Malley, P. D.; Peters, W. A.; Pittman, S. T. ; Ratkiewicz, A.; Shand, C.; Smith, J. F. ; Smith, M. S.; Fukui, T.; Tostevin, J. A.; Utsuno, Y.

In atomic nuclei, the spin-orbit interaction originates from the coupling of the orbital motion of a nucleon with its intrinsic spin. Recent experimental and theoretical works have suggested a weakening of the spin-orbit interaction in neutron-rich nuclei far from stability. To study this phenomenon, we have investigated the spin-orbit energy splittings of single-hole and single-particle valence neutron orbits of ¹³²Sn. The spectroscopic strength of single-hole states in ¹³¹Sn was determined from the measured differential cross sections of the tritons from the neutron-removing ¹³²Sn(d, t)131Sn reaction, which was studied in inverse kinematics at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The spectroscopic factors of the lowest 3/2⁺, 1/2⁺ and 5/2⁺ states were found to be consistent with their maximal values of (2j + 1) , confirming the robust shell closure at ¹³²Sn. We compared the spin-orbit splitting of neutron single-hole states in ¹³¹Sn to those of single-particle states in ¹³³Sn determined in a recent measurement of the ¹³²Sn(d, p)¹³³Sn reaction. We found a significant reduction of the energy splitting of the weakly bound 3p orbits compared to the well-bound 2d orbits, and that all the observed energy splittings can be reproduced remarkably well by calculations using a one-body spin-orbit interaction and a Woods–Saxon potential of standard radius and diffuseness. The observed reduction of spin-orbit splitting can be explained by the extended radial wavefunctions of the weakly bound orbits, without invoking a weakening of the spin-orbit strength.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC05-00OR22725; FG52-08NA28552; SC0001174; FG02-96ER40963; FG02-96ER40955; NA0002132
• OSTI ID: 1463203
• Alternate ID(s): OSTI ID: 1495976
• Journal Information: Physics Letters B, Journal Name: Physics Letters B Vol. 785 Journal Issue: C; ISSN 0370-2693
• Publisher: Elsevier
• Country of Publication: Netherlands
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS