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Gold and platinum nuclei near the $N$ = 104 mid-shell, such as $^{182}$Au and $^{182}$Pt, have attracted considerable interest due to rapid changes in ground-state deformation compared to heavier isotopes. Additionally, a coexistence of at least two configurations, a weakly oblate and a prolate, has been observed for platinum isotopes in this region [1,2]. These phenomena have been extensively studied using various experimental methods, including laser spectroscopy [3] and $\beta$-delayed $\gamma$-ray spectroscopy [4]. The latter approach provides access to excited levels in the daughter nucleus up to relatively high excitation energies. Since $\beta$ decay is sensitive to changes in nuclear structure, $\beta$-decay feeding patterns and log $ft$ values can be used to probe shape coexistence and configuration mixing in the daughter nucleus.
In this contribution, we present results of a detailed $\gamma$--$\gamma$ coincidence analysis of $^{182}$Pt deexcitation following the electron capture/$\beta^+$ decay of $^{182}$Au studied at the ISOLDE facility. Element-selective laser ionisation and mass separation were employed, resulting in a high-purity $^{182}$Au sample measured at the ISOLDE Decay Station (IDS) [5], with four HPGe Clover detectors and an array of silicon PIN diodes. Transitions known from the previous $\beta$-decay study [4] were confirmed, and the level scheme of $^{182}$Pt was significantly expanded [6]. Log $ft$ values for decays to the first three $2^+$ states in $^{182}$Pt indicate mixing between different band structures. Moreover, an unexpectedly high $\beta$-decay feeding intensity to 4$^+$ levels was observed, which is inconsistent with the second forbidden non-unique $\beta$ decay expected from the currently known $(2^+)$ ground state of $^{182}$Au [7]. We discuss several possible explanations, namely the reassessment of the $^{182}$Au ground state assignment, the existence of a new isomeric state, and the pandemonium effect.
[1] K. Heyde and J. L. Wood, Rev. Mod. Phys. 83, 1467 (2011).
[2] P. E. Garrett, M. Zielińska and E. Clément, Prog. Part. Nucl. Phys 124, 103931 (2022).
[3] J. G. Cubiss et al., Phys. Rev. Lett. 131, 202501 (2023).
[4] P. M. Davidson et al., Nucl. Phys. A 657, 219 (1999).
[5] ISOLDE Decay Station website. https://isolde-ids.web.cern.ch.
[6] J. Mišt et al., Phys. Rev. C. 112, 024328 (2025).
[7] R. D. Harding et al., Phys. Rev. C 102, 024312 (2020).
