The changes in mean-squared charge radii of neutron-deficient gold nuclei have been determined using the in-source, resonance-ionization laser spectroscopy technique, at the ISOLDE facility (CERN). From these new data, nuclear deformations are inferred, revealing a competition between deformed and spherical configurations. The isotopes ^{180,181,182}Au are observed to possess well-deformed ground states and, when moving to lighter masses, a sudden transition to near-spherical shapes is seen in the extremely neutron-deficient nuclides, ^{176,177,179}Au. A case of shape coexistence and shape staggering is identified in ^{178}Au which has a ground and isomeric state with different deformations. These new data reveal a pattern in ground-state deformation unique to the gold isotopes, whereby, when moving from the heavy to light masses, a plateau of well-deformed isotopes exists around the neutron midshell, flanked by near-spherical shapes in the heavier and lighter isotopes-a trend hitherto unseen elsewhere in the nuclear chart. The experimental charge radii are compared to those from Hartree-Fock-Bogoliubov calculations using the D1M Gogny interaction and configuration mixing between states of different deformation. The calculations are constrained by the known spins, parities, and magnetic moments of the ground states in gold nuclei and show a good agreement with the experimental results.

The yield of 18 ion beams of radioactive gold nuclei produced in the thick uranium target at ISOLDE (CERN) by 1.4-GeV protons was measured. The production-efficiency dependence on the half-life (efficiency curve) was derived using the in-target production calculations by the FLUKA-CERN code. The irregularities in the efficiency curve for long-lived high-spin gold isomers (187,191,193Aum) were found. Three release models were tested for the efficiency-curve description.

Recently there has been an increased interest to apply the sensitive β-decay asymmetry detected nuclear magnetic resonance (β-NMR) technique to biological studies. A liquid-sample β-NMR setup was build at ISOLDE to allow such investigations and to use the resolution gain of liquid-state NMR in nuclear physics. As part of this setup a magnetic field locking system, a set of printed circuit board shimming coils, a sample exchange system, a set of compact β-detectors and a custom experimental vacuum chamber were developed. The main magnetic field was stabilized down to the ppm level by the locking system while allowing the direct determination of the absolute magnetic field. The homogeneity of the magnetic field was improved to ≤ 5 ppm over the sample volume by the shimming coils. Time spent on changing samples was reduced by a factor of five by the liquid sample exchange system. During experiments it was possible to continuously observe the liquid sample thanks to the custom chamber and compact β-detectors. The absolute field determination allows for a novel way to reference β-NMR measurements, removing the need for time consuming reference measurements. The improved accuracy and resolution resulting from these innovations allows the study of the distribution of nuclear magnetization and (bio)chemicals using high-accuracy liquid-sample β-NMR.

Recently there has been an increased interest to apply the sensitive $\beta$-decay anisotropy detected nuclear magnetic resonance ($\beta$-NMR) technique to biological studies. A low-field (non-super conducting magnet) liquid $\beta$-NMR setup was build at ISOLDE to allow such investigations and to use the resolution gain of liquid-state NMR in nuclear physics. As part of this setup a magnetic field locking system, a set of printed circuit board shimming coils, a sample exchange system, a set of compact $\beta$-detectors and a custom experimental vacuum chamber were developed. The main magnetic field was stabilized down to the ppm level by the locking system while allowing the direct determination of the absolute magnetic field. The homogeneity of the magnetic field was improved to $\leq$ 5 ppm over the sample volume by the shimming coils. Sample changing times were reduced from hours to mere minutes by the liquid sample exchange system and during experiments it was possible to continuously observe the sample from an accurate reproducible position because of the custom chamber and compact $\beta$-detectors. With these upgrades low-field $\beta$-NMR experiments can be, and have been performed. The absolute field determination allows for a novel way to reference $\beta$-NMR measurements, abolishing the need for time consuming reference measurements. Possible future applications include the study of the distribution of nuclear magnetization and (bio)chemical studies.

The changes in the mean-square charge radius (relative to ^{209}Bi), magnetic dipole, and electric quadrupole moments of ^{187,188,189,191}Bi were measured using the in-source resonance-ionization spectroscopy technique at ISOLDE (CERN). A large staggering in radii was found in ^{187,188,189}Bi^{g}, manifested by a sharp radius increase for the ground state of ^{188}Bi relative to the neighboring ^{187,189}Bi^{g}. A large isomer shift was also observed for ^{188}Bi^{m}. Both effects happen at the same neutron number, N=105, where the shape staggering and a similar isomer shift were observed in the mercury isotopes. Experimental results are reproduced by mean-field calculations where the ground or isomeric states were identified by the blocked quasiparticle configuration compatible with the observed spin, parity, and magnetic moment.

We determine for the first time the magnetic dipole moment of a short-lived nucleus with part-permillion (ppm) accuracy. To achieve this 2-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 at CERN. Using liquid samples as hosts, we obtain narrow, subkilohertz-linewidth, resonances, while a simultaneous in situ H-1 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 Na-26, 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 toward a wide range of applications of the ultrasensitive beta-NMR in physics, chemistry, and biology.

Hyperfine-structure parameters and isotope shift of the 9/2(-) isomeric state in Au-187 relative to Au-197 for the 267.6-nm atomic transition have been measured for the first time using the in-source resonance-ionization spectroscopy technique. The magnetic dipole moment and change in the mean-square charge radius for this 9/2(-) isomer have been deduced. The observed large isomer shift relative to the 1/2(+) ground state in Au-187 confirms the occurrence of the shape coexistence in Au-187 proposed earlier from the analysis of the nuclear spectroscopic data and particle plus triaxial rotor calculations. The analysis of the magnetic moment supports the previously proposed 9/2(-), 1/2(-)[541] assignment at moderate prolate deformation for Au-187(m).

beta-delayed fission (beta DF) decay of a low-spin (ls) and a high-spin (hs) isomer in Bi-188 was studied at the ISOLDE facility at CERN. Isomer-selective laser ionization and time gating were employed to investigate each isomer separately and their beta DF partial half-lives were determined: T-1/2p,T-beta DF(Bi-188(hs)) = 5.6(8) x 10(3) s and T-1/2p,T-beta DF(Bi-188(ls)) = 1.7(6) x 10(3) s. This work is the first beta DF 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 Pb-188, following the beta 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-1/2p,T-beta DF(Bi-188(hs)), the calculated fission barrier of Pb-188 had to be reduced by approximate to 30%. After this reduction, the measured T-1/2p,T-beta DF(Bi-188(ls)) was in agreement with calculations for a few possible configurations for Bi-188(ls). Theoretical beta DF probabilities for these configurations were found to be lower by a factor of 4-9 than the beta DF probability of Bi-188(hs). The fission fragment mass distribution of Pb-188 was compared to the scission-point model SPY and the calculations based on the finite-range liquid-drop model. The first observation of beta DF for Bi-190 is also reported.

A comprehensive study of the isotope Au-178 has been made at the CERN-ISOLDE facility, using resonance laser ionization. Two long-lived states in Au-178 were identified-a low-spin ground state and a high-spin isomer-each of which were produced as pure beams. Using the ISOLTRAP precision Penning trap, the excitation energy of the isomeric state in Au-178 was determined to be E * = 189(14) keV. The a-decay fine structure patterns of the two states were studied using the Windmill decay station, providing information on the low-lying states in the daughter nucleus Ir-174. Nuclear spin assignments of I (Au-178(g)) = (2, 3) and I (Au-178(m)) = (7, 8) are made based on the observed beta-decay feeding and hyperfine structure intensity patterns. These spin assignments are used for fitting the hyperfine structures of the two states from which values for the magnetic dipole moments are extracted. The extracted moments are compared with calculations using additivity relations to establish the most probable configurations for Au-178(g,m).

A study of the Hg-180 decay chain performed at the CERN-ISOLDE facility has allowed the ground-state-to-ground-state alpha decay of Pt-180 to be investigated. A more precise alpha-decay branching ratio of b(alpha)(Pt-180) = 0.52(5)% has been deduced. The reduced alpha-decay width calculated using the new value provides a more consistent picture of the systematics for J(pi) = 0(+) -> 0(+) ground-state-to-ground-state state alpha decays of neutron-deficient, eveneven platinum isotopes.

Hyperfine-structure constants for the 6s S-2(1/2) and 6p P-2(1/2) atomic states of the I-pi=11/2(-) gold isomers Au-177,191,193,195(m) have been measured at CERN-ISOLDE, using the in-source laser resonance-ionization spectroscopy technique. From the measured hyperfine constants the differences between hyperfine anomalies for these atomic states have been deduced. These differential hyperfine anomaly values have been used to determine the 6s-state hyperfine anomaly relative to the stable Au-197 with advanced atomic calculations. Magnetic dipole moments for the gold isomers in question have been deduced, taking into account the corresponding relative hyperfine-anomaly values. It has been shown that the commonly used prescription for the extraction of the magnetic moment values for the gold isotopes should be reconsidered. The magnetic moments calculated by this prescription have been reevaluated by properly accounting for the hyperfine anomaly, which is as large as 10% for several gold isotopes.

A number of radiogenically produced dysprosium isotopes have been studied by in-source laser spectroscopy at ISOLDE using the Resonance Ionization Laser Ion Source (RILIS). Isotope shifts were measured relative to 152Dy in the 4f106s25I8 (gs) →4f106s6p (8,1)8o (418.8nmvac) resonance transition. The electronic factor, F, and mass shift factor, M, were extracted and used for determining the changes in mean-squared charge radii for 145mDy and 147mDy for the first time.

A study of the ground states of the laser-ionized and mass-separated odd-odd isotopes( 180,182)Au was performed using the Resonance Ionization Laser Ion Source, Windmill detection setup and ISOLTRAP Multi-Reflection Time-of-Flight Mass Spectrometer at ISOLDE, CERN. A complex fine-structure alpha-decay pattern of Au-180 was deduced, providing insight into the low-lying levels in the daughter nucleus Ir-176. An alpha-decay branching ratio of b(alpha)(Au-180) = 0.58(10)% and a half-life of T-1/2 = 7.2(5) s have also been derived, allowing for the calculation of the reduced alpha-decay widths and determining the degree of hindrance of respective alpha-decay branches. From complementary first in-source laser spectroscopy measurements of the hyperfine structure in atomic transitions of Au-180,Au-182 , the nuclear magnetic moments of mu(Au-180) = -0.83(9) mu(N) and mu(Au-182) = 1.66(9) mu(N) were extracted with an inclusion of a correction for the hyperfine anomaly. Based on the observed hyperfine structure patterns, and on the comparison of the measured and calculated p. values, a preferred ground-state spin and parity I-pi(Au-180(gs)) = (1+) is proposed, and the earlier assignment of I-pi(Au-182(gs)) = (2+) is confirmed. For Au-180, the most probable proton-neutron Nilsson configuration of pi/3/2(-)[532] circle times nu 5/2(-)[512] suggests the same proton state as in the heavier deformed odd-odd nuclei Au-182,Au-184.

A study of the Hg180 decay chain performed at the CERN-ISOLDE facility has allowed the ground-state–to–ground-state α decay of Pt180 to be investigated. A more precise α-decay branching ratio of bα(180Pt)=0.52(5)% has been deduced. The reduced α-decay width calculated using the new value provides a more consistent picture of the systematics for Jπ=0+→0+ ground-state–to–ground-state state α decays of neutron-deficient, even-even platinum isotopes.Received 6 October 2019DOI:https://doi.org/10.1103/PhysRevC.101.014314Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAlpha decayNuclear structure & decaysProperties150 ≤ A ≤ 189Nuclear Physics

Cubiss, J.G.; Harding, R.D.; Andreyev, A.N.; Althubiti, N.; Andel, B.; Antalic, S.; Barzakh, A.E.; Cocolios, T.E.; Day Goodacre, T.; Farooq-Smith, G.J.; Fedorov, D.V.; Fedosseev, V.N.; Gaffney, L.P.; Ghys, L.; Huyse, M.; Lynch, K.M.; Marsh, B.A.; Palenzuela, Y. Martinez; Molkanov, P.L.; Rossel, R.E.; Rothe, S.; Seliverstov, M.D.; Sels, S.; Spagnoletti, P.; Van Beveren, C.; Van Duppen, P.; Veinhard, M.; Verstraelen, E.; Zadvornaya, A.

The new nuclides $^{165}\mathrm{Pt}$ and $^{170}\mathrm{Hg}$ were produced in the reactions $^{92}\mathrm{Mo}(^{78}\mathrm{Kr},5n)$ and $^{96}\mathrm{Ru}(^{78}\mathrm{Kr},4n)$ at bombarding energies of 418 MeV and 390 MeV, respectively. For $^{170}\mathrm{Hg}$ an $\ensuremath{\alpha}$-particle energy of ${E}_{\ensuremath{\alpha}}=7590(30)\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$ and half-life of ${t}_{1/2}=0.{08}_{\ensuremath{-}0.04}^{+0.40}\phantom{\rule{0.16em}{0ex}}\mathrm{ms}$ were deduced, while for $^{165}\mathrm{Pt}$ the corresponding values were 7272(14) keV and $0.{26}_{\ensuremath{-}0.09}^{+0.26}\phantom{\rule{0.16em}{0ex}}\mathrm{ms}$. Comparison of the reduced $\ensuremath{\alpha}$-decay widths with systematics indicates that both $\ensuremath{\alpha}$ decays are unhindered. Although combining the measured $\ensuremath{\alpha}$-decay $Q$ values with extrapolated masses suggests that both new nuclides are unbound to two-proton emission by more than 1 MeV, their $\ensuremath{\alpha}$-decay half-lives are too short for this decay mode to compete. Improved data were also obtained for $^{166,167}\mathrm{Pt}$, produced via the $^{96}\mathrm{Ru}(^{78}\mathrm{Kr},\ensuremath{\alpha}4n)$ and $^{96}\mathrm{Ru}(^{78}\mathrm{Kr},\ensuremath{\alpha}3n)$ reactions at bombarding energies of 390 MeV and 418 MeV.

J. Hilton,1,2,* J. Uusitalo,1 J. Sarén,1 R. D. Page,2 D. T. Joss,2 M. A. M. AlAqeel,2,3 H. Badran,1 A. D. Briscoe,2 T. Calverley,1,2 D. M. Cox,1,† T. Grahn,1 A. Gredley,2 P. T. Greenlees,1 R. Harding,4 A. Herzan,5,2,‡ E. Higgins,2 R. Julin,1 S. Juutinen,1 J. Konki,1,§ M. Labiche,6 M. Leino,1 M. C. Lewis,2 J. Ojala,1 J. Pakarinen,1 P. Papadakis,1,‖ J. Partanen,1,¶ P. Rahkila,1 P. Ruotsalainen,1 M. Sandzelius,1 C. Scholey,1 J. Sorri,1,7 L. Sottili,1 S. Stolze,1,** and F. Wearing2 1University of Jyvaskyla, Department of Physics, P.O. Box 35, FI-40014 University of Jyvaskyla, Finland 2University of Liverpool, Oliver Lodge Laboratory, Liverpool L69 7ZE, United Kingdom 3Imam Mohammad Ibn Saud Islamic University (IMISU), Riyadh, 11623, Saudi Arabia 4University of York, Heslington, York YO10 5DD, United Kingdom 5Institute of Physics, Slovak Academy of Science, Bratislava SK-84511, Slovakia 6STFC Daresbury Laboratory, Sci-Tech Daresbury, Warrington WA4 4AD, United Kingdom 7Sodankylä Geophysical Observatory, University of Oulu, FI-99600 Sodankylä, Finland

A beamline dedicated to the production of laser-polarized radioactive beams has been constructed at ISOLDE, CERN. We present here different simulations leading to the design and construction of the setup, as well as technical details of the full setup and examples of the achieved polarizations for several radioisotopes. Beamline simulations show a good transmission through the entire line, in agreement with observations. Simulations of the induced nuclear spin-polarization as a function of atom-laser interaction length are presented for $^{26,28}$Na, [1] and for $^{35}$Ar, which is studied in this work. Adiabatic spin rotation of the spin-polarized ensemble of atoms, and how this influences the observed nuclear ensemble polarization, are also performed for the same nuclei. For $^{35}$Ar, we show that multiple-frequency pumping enhances the ensemble polarization by a factor 1.85, in agreement with predictions from a rate equations model. [1] J. Phys. G: Nucl. Part. Phys./1744084005