Study of the \beta^{-} decay of 116m1In: A new interpretation of low-lying 0+ states in 116Sn

The 116Sn nucleus contains a collective rotational band originating from proton \(\pi\) 2p-2h excitations across the proton \(Z=50\) shell gap. Even though this nucleus has been extensively investigated in the past, there was still missing information on the low-energy interband transitions connecting the intruder and normal structures. The low-lying structure of 116Sn was investigated through a high-statistics study of the \(\beta^{-}\) decay of 116m1In with the \(8\pi\) spectrometer and its ancillary detectors at TRIUMF. These measurements are critical in order to properly characterize the \(\pi\) 2p-2h rotational band. Weak \(\gamma\)-decay branches are observed utilizing \(\gamma\)-\(\gamma\) coincidence spectroscopy methods, leading to the first direct observation of the 85 keV \(2_{2}^{+}\rightarrow 0_{3}^{+}\) \(\gamma\) ray with a transition strength of \(B(E2) = 99.7(84)\) W.u. The analysis of these results strongly suggests that the 2027 keV \(0_{3}^{+}\) state should replace the previously assigned 1757 keV \(0_{2}^{+}\) state as the band-head of the \(\pi\) 2p-2h rotational band.