Collective 2p-2h intruder states in $^{118}$Sn studied via $\beta$-decay of $^{118}$In using GRIFFIN

TL;DR

This study investigates shape coexistence and intruder states in $^{118}$Sn through detailed $eta$-decay measurements, revealing new transitions and refining transition probabilities, supported by theoretical IBM-2 calculations.

Contribution

It provides new high-statistics experimental data on intruder states in $^{118}$Sn and compares these with advanced theoretical models, enhancing understanding of shape coexistence.

Findings

99 transitions placed in the level scheme, 43 newly observed

Refined $B(E2)$ value for the 2$^+_{intr.} ightarrow 0^+_{intr.}$ transition

Comparison of experimental data with $sd$ IBM-2 calculations

Abstract

The low-lying structure of semi-magic $^{118}$Sn has been investigated through the $\beta$-decay of $^{118}$In ($T_{1/2}=4.45$ min) to study shape coexistence via the reduced transition probabilities of states in the 2p-2h proton intruder band. This high-statistics study was carried out at TRIUMF-ISAC with the GRIFFIN spectrometer. In total, 99 transitions have been placed in the level scheme with 43 being newly observed. Three low-lying $\gamma$-ray transitions with energies near 285 keV have been resolved from which the 2$^+_{\mathrm{intr.}} \rightarrow 0^+_{\mathrm{intr.}}$ 284.52-keV transition was determined to have half of the previous branching fraction leading to a $B(E2;2^+_2\rightarrow 0^+_2)$ of 21(4) W.u. compared to 39(7) W.u. from the previous measurement. Calculations using $sd$ IBM-2 with mixing have also been made to compare the experimental $B(E2)$ values to the theoretical values and to make comparisons to the $^{114,116}$Sn isotopes previously studied using the same theoretical model.