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Gold and platinum nuclei near the $N$ = 104 mid-shell, including $^{182}$Au and $^{182}$Pt, have drawn significant attention owing to the rapid evolution of ground-state deformation relative to heavier isotopes. In even-even platinum isotopes in particular, experimental evidence points to the coexistence of distinct configurations, commonly associated with weakly oblate and more deformed prolate shapes [1,2]. These structural features have been extensively studied using a range of experimental techniques, including laser spectroscopy [3] and $\beta$-delayed $\gamma$-ray spectroscopy [4]. The latter approach often 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 provide insight into shape coexistence and configuration mixing in the daughter nucleus.
In this contribution, we present results of a detailed $\gamma$-ray spectroscopy of the $^{182}$Pt level structure populated in the electron capture/$\beta^+$ decay of $^{182}$Au. The experiment was performed at the ISOLDE facility, where a high-purity $^{182}$Au beam was produced using element-selective laser ionisation and mass separation. The implanted activity was measured at the ISOLDE Decay Station (IDS) [5] equipped 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 populating the first three $2^+$ states in $^{182}$Pt indicate mixing between different band structures. Moreover, a notably strong $\beta$-decay feeding intensity to 4$^+$ levels was observed, which is inconsistent with the second-forbidden non-unique $\beta$ decay expected from the currently assigned $(2^+)$ ground state of $^{182}$Au [7]. We consider several possible explanations, including a reassignment of the $^{182}$Au ground state, the existence of a new isomeric state, and the impact of the Pandemonium effect.
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[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).