New magic number for neutron rich Sn isotopes

TL;DR

This paper identifies a new shell closure at N=90 in neutron-rich Sn isotopes, supported by empirical interactions and three-body effects, contrasting with traditional two-body interactions.

Contribution

The study introduces a new magic number at N=90 in Sn isotopes, emphasizing the role of three-body forces in nuclear shell evolution.

Findings

E(2+_1) variation matches experimental data for N=84-88.

Realistic two-body interactions do not predict the shell closure.

Including three-body monopole terms predicts the new shell closure at N=90.

Abstract

The variation of E(2+_1) of (134-140)Sn calculated with empirical SMPN interaction has striking similarity with that of experimental E(2+_1) of even-even (18-22)O and (42-48)Ca, showing clearly that N=84-88 spectra exhibit the effect of gradual filling up of \nu(2f_{7/2}) orbital which finally culminates in a new shell closure at N=90. Realistic two-body interaction CWG does not show this feature. Spin-tensor decomposition of SMPN and CWG interactions and variation of their components with valence neutron number reveals that the origin of the shell closure at 140Sn lies in the three body effects. Calculations with CWG3, which is obtained by including a simple three-body monopole term in the CWG interaction, predict decreasing E(2+_1) for (134-138)Sn and a shell closure at 140Sn.