6$^+$ isomers in neutron-rich Sn-isotopes beyond N$=82$ and effective interaction

TL;DR

This paper demonstrates that the RCDB effective interaction accurately explains 6+ isomers and B(E2) values in neutron-rich Sn isotopes beyond N=82 without requiring core excitations, improving upon previous models.

Contribution

The study shows that a slight reduction of matrix elements in the RCDB interaction suffices to match experimental data, challenging prior modifications needed in other interactions.

Findings

RCDB interaction reproduces observed energy levels and B(E2) values.

Minimal matrix element adjustment (25 keV) improves model accuracy.

Core excitations are unnecessary for explaining data beyond N=82.

Abstract

Recent observation of the 6$^+$ seniority isomers and measurements of the B${(E2)}$ values in the $^{134-138}$Sn isotopes lying close to the neutron drip line have raised some questions about the validity of the currently used effective interactions in the neutron-rich region. Simpson $\it{et}$ $\it{al.}$ [Phys. Rev. Lett. $\textbf{113}$, 132502 (2014)] had to modify the diagonal and non-diagonal ${\nu}f_{7/2}^2$ two body matrix elements of the "${Vlk}$" interaction by ${\sim150}$ keV in their shell model calculations in order to explain the data of $^{136}$Sn. In contrast, we are able to explain the observed energy levels and the B${(E2)}$ values after marginal reduction of the same set of matrix elements by ${25}$ keV in the "RCDB" (Renormalized CD-Bonn) interaction. The observed mismatch in reproducing the data of $^{136}$Sn is due to the seniority mixing. Further, we do not find it necessary to consider the core excitations, and the "RCDB" interaction seems better suited to explain the data beyond N$=82$ magic number.