## Abstract

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 ^{132}Sn. The spectroscopic strength of single-hole states in ^{131}Sn was determined from the measured differential cross sections of the tritons from the neutron-removing ^{132}Sn(d, t)^{131}Sn 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 N=82 shell closure at ^{132}Sn. We compared the spin-orbit splitting of neutron single-hole states in ^{131}Sn to those of single-particle states in ^{133}Sn determined in a recent measurement of the ^{132}Sn(d, p)^{133}Sn 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.

Original language | English (US) |
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Pages (from-to) | 615-620 |

Number of pages | 6 |

Journal | Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics |

Volume | 785 |

DOIs | |

State | Published - Oct 10 2018 |

## All Science Journal Classification (ASJC) codes

- Nuclear and High Energy Physics

## Keywords

- Doubly-magic nuclei
- Nuclear structure
- Shell model
- Spin-orbit interaction
- Transfer reactions