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A study of the laser-ionized and mass-separated neutron-deficient isotopes $^{176,177,179}$Au was performed using the Resonance Ionization Laser Ion Source and the Windmill detection setup at ISOLDE, CERN. New and improved data on complex fine-structure α decays of the three isotopes were deduced, providing insight into the low-lying levels in the daughter nuclei $^{172,173,175}$Ir. New information on the properties of β-decay daughter products $^{177,179}$Pt was also obtained. From the first in-source laser spectroscopy measurements of the hyperfine structure in the atomic 267.6-nm transition of 176Au, the nuclear magnetic moments for both high- and low-spin α-decaying states were deduced. Together with the values determined from the additivity relations, they were used to propose the most probable spins and configurations for both states. The α-decay branching ratios were determined as $b_{\alpha}$ $\left (^{176}\textrm{Au}^{ls}\right)=58(5)$% and $b_{\alpha}$ $(^{176} \textrm{Au}^{hs})=29(5)$%.

Physical review / C 101(6), 064321 (2020). doi:10.1103/PhysRevC.101.064321, Published by APS, Woodbury, NY

We determine for the first time the magnetic dipole moment of a short-lived nucleus with part-per-million (ppm) accuracy. To achieve this two orders of magnitude improvement over previous studies, we implement a number of innovations into our $\beta$-detected Nuclear Magnetic Resonance ($\beta$-NMR) setup at ISOLDE/CERN. Using liquid samples as hosts we obtain narrow, sub-kHz linewidth, resonances, while a simultaneous in-situ $^1$H NMR measurement allows us to calibrate and stabilize the magnetic field to ppm precision, thus eliminating the need for additional $\beta$-NMR reference measurements. Furthermore, we use ab initio calculations of NMR shielding constants to improve the accuracy of the reference magnetic moment, thus removing a large systematic error. We demonstrate the potential of this combined approach with the 1.1 s half-life radioactive nucleus $^{26}$Na, which is relevant for biochemical studies. Our technique can be readily extended to other isotopic chains, providing accurate magnetic moments for many short-lived nuclei. Furthermore, we discuss how our approach can open the path towards a wide range of applications of the ultra-sensitive $\beta$-NMR in physics, chemistry, and biology., Comment: re-submitted

International audience; $β$-delayed fission ($β$DF) decay of a low-spin (ls) and a high-spin (hs) isomer in $^{188}$Bi was studied at the ISOLDE facility at CERN. Isomer-selective laser ionization and time gating were employed to investigate each isomer separately and their $β$DF partial half-lives were determined: $T_{1/2\mathrm{p},β\mathrm{DF}} (^{188}\mathrm{Bi^{ls}})=5.6(8)×10^3$ s and $T_{1/2\mathrm{p},β\mathrm{DF}} (^{188}\mathrm{Bi^{hs}})=1.7(6)×10^3$ s. This work is the first βDF study of two states in one isotope and allows the spin dependence of low-energy fission to be explored. The fission fragment mass distribution of a daughter nuclide $^{188}$Pb, following the $β$ decay of the high-spin isomer, was deduced and indicates a mixture of symmetric and asymmetric fission modes. Experimental results were compared with self-consistent mean-field calculations based on the finite-range Gogny D1M interaction. To reproduce the measured $T_{1/2\mathrm{p},β\mathrm{DF}} (^{188}\mathrm{Bi^{hs}})$, the calculated fission barrier of $^{188}$Pb had to be reduced by ≈30%. After this reduction, the measured $T_{1/2\mathrm{p},β\mathrm{DF}} (^{188}\mathrm{Bi^{ls}})$ was in agreement with calculations for a few possible configurations for $^{188}\mathrm{Bi^{ls}}$. Theoretical $β$DF probabilities for these configurations were found to be lower by a factor of 4–9 than the $β$DF probability of $^{188}\mathrm{Bi^{hs}}$. The fission fragment mass distribution of $^{188}$Pb was compared to the scission-point model SPY and the calculations based on the finite-range liquid-drop model. The first observation of $β$DF for $^{190}$Bi is also reported.