Half-life determination of 215^{215}At and 221^{221}Ra with high-purity radioactive ion beams

International audienceAt CERN-ISOLDE, high-purity radioactive ion beams of $^{219}$Fr and $^{221}$RaF were investigated with $\alpha$-decay spectroscopy at the CRIS and ASET experiments in the course of three different experimental campaigns. The half-life of $^{215}$At, $\alpha$-decay daughter of $^{219}$Fr, is measured to be 36.3(3)[9]μs, and that of $^{221}$Ra was determined to be 26.2(1)[6]s, both of which are well in line with the trends in this region of the nuclear landscape but at odds with some of the reported literature

New collective structures in Au-179 and their implications for the triaxial deformation of the Pt-178 core

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New collective structures in 179Au and their implications for the triaxial deformation of the 178Pt core

The extremely neutron-deficient isotope 179Au has been studied by a combination of in-beam γ-ray and isomeric-decay spectroscopy. For in-beam spectroscopy, the recoil-isomer tagging technique was employed, using the known 3/2−, T1/2=328 ns isomer. A new rotational band, associated with the unfavored signature band of the 1h9/2⊕2f7/2 proton-intruder configuration, was revealed. A previously unknown, high-spin isomeric state with an excitation energy of 1743(17) keV and T1/2=2.16(8)µs was discovered. Five decay paths were identified, some of them feeding previously unknown non-yrast excited states, associated with the 1i13/2 proton-intruder configuration. Calculations based on the particle-plus-triaxial-rotor model were performed to interpret the data. On the basis of these calculations, the new 1h9/2⊕2f7/2 rotational band is interpreted as due to triaxial deformation of the underlying configuration with β2≈0.26 and γ≈27∘. Observed non-yrast states of the positive-parity 1i13/2 intruder configuration are interpreted as due to triaxial deformation with β2≈0.26 and γ≈20∘.peerReviewe