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13 pags., 5 figs., 2 tabs., The structure of Po208 populated through the EC/β+ decay of At208 is investigated using γ-ray spectroscopy at the ISOLDE Decay Station. The presented level scheme contains 27 new excited states and 43 new transitions, as well as a further 50 previously observed γ rays which have been (re)assigned a position. The level scheme is compared to shell model calculations. Through this analysis approximately half of the β-decay strength of At208 is found to proceed via allowed decay and half via first-forbidden decay. The first-forbidden transitions predominantly populate core excited states at high excitation energies, which is qualitatively understood using shell model considerations. This mass region provides an excellent testing ground for the competition between allowed and first-forbidden β-decay calculations, important for the detailed understanding of the nucleosynthesis of heavy elements., The research leading to these results received funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 654002. Support from the European Union Seventh Framework through ENSAR Contract No. 262010, as well as the Science and Technology Facilities Council (U.K.) through Grants No. ST/P005314/1, No. ST/L005743/1, No. ST/J000051/1, No. ST/L005670/1, and No. ST/P004598/1, the German BMBF under Contract No. 05P18PKCIA and “Verbundprojekt 05P2018” as well as Spanish MINECO Grants No. FPA2015-65035- P and No. FPA2017-87568-P, FWO Vlaanderen (Belgium), GOA/2015/010 (BOF KU Leuven), the Excellence of Science Programme (EOS-FWO), the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (BriX network P7/12), the Polish National Science Centre under Contracts No. UMO-2015/18/M/ST2/00523 and No. UMO-2019/33/N/ST2/03023, National Science Foundation (U.S.) Grant No. PHY1811855, and the Romanian IFA project CERN-RO/ISOLDE is acknowledged. P.H.R. acknowledges support from the U.K. Department for Business, Energy and Industrial Strategy via the National Measurement Office

Decay spectroscopy of the long-lived states in 186Tl has been performed at the ISOLDE Decay Station at ISOLDE, CERN. The � decay from the low-spin (2

The β decay of 207Hg into the single-proton-hole nucleus 207Tl has been studied through γ-ray spectroscopy at the ISOLDE Decay Station (IDS) with the aim of identifying states resulting from coupling of the πs−11/2, πd−13/2, and πh−111/2 shell model orbitals to the collective octupole vibration. Twenty-two states were observed lying between 2.6 and 4.0 MeV, eleven of which were observed for the first time, and 78 new transitions were placed. Two octupole states (s1/2-coupled) are identified and three more states (d3/2-coupled) are tentatively assigned using spin-parity inferences, while further h11/2-coupled states may also have been observed for the first time. Comparisons are made with state-of-the-art large-scale shell model calculations and previous observations made in this region, and systematic underestimation of the energy of the octupole vibrational states is noted. We suggest that in order to resolve the difference in predicted energies for collective and noncollective t=1 states (t is the number of nucleons breaking the 208Pb core), the effect of t=2 mixing may be reduced for octupole-coupled states. The inclusion of mixing with t=0,2,3 excitations is necessary to replicate all t=1 state energies accurately.