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International audience; A comprehensive study of the isotope $^{178}$Auhas been made at the CERN-ISOLDE facility, using resonance laser ionization. Two long-lived states in$^{178}$Auwere 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$^{178}$Auwas determined to be$E$$^{*}$=189(14)keV. Theα-decay fine structure patterns of the two states were studied using the Windmill decay station, providing information on the low-lying states in the daughter nucleus$^{174}$Ir. Nuclear spin assignments of$I$($^{178}$Au$^{g}$)=(2,3)and$I$($^{178}$Aum)=(7,8)are made based on the observed$\beta$-decay feeding and hyperfine structure intensity patterns. These spin assignments are used for fitting the hyperfine structures of the two states from which values for the magnetic dipole moments are extracted. The extracted moments are compared with calculations using additivity relations to establish the most probable configurations for$^{178}$Au$^{g,m}$.

International audience; Hyperfine-structure parameters and isotope shifts for the 795-nm atomic transitions in $^{217,218,219}$At have been measured at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy technique. Magnetic dipole and electric quadrupole moments, and changes in the nuclear mean-square charge radii, have been deduced. A large inverse odd-even staggering in radii, which may be associated with the presence of octupole collectivity, has been observed. Namely, the radius of the odd-odd isotope $^{218}$At has been found to be larger than the average of its even-$N$ neighbors, $^{217,219}$At. The discrepancy between the additivity-rule prediction and experimental data for the magnetic moment of $^{218}$At also supports the possible presence of octupole collectivity in the considered nuclei.

The first accurate measurements of the α-decay branching ratio and half-life of the Iπ=1/2+ ground state in $^{181}$Tl have been made, along with the first determination of the magnetic moments and I=1/2 spin assignments of the ground states in $^{177,179}$Au. The results are discussed within the complementary systematics of the reduced α-decay widths and nuclear g factors of low-lying, Iπ=1/2+ states in the neutron-deficient lead region. The findings shed light on the unexpected hindrance of the 1/2+→1/2+, $^{181}$Tl→g177Au$^{g}$ α decay, which is explained by a mixing of π3s1/2 and π2d3/2 configurations in $^{177}$Au$^{g}$, whilst $^{181}$Tl$^{g}$ remains a near-pure π3s1/2. This conclusion is inferred from the g factor of $^{177}$Au$^{g}$ which has an intermediate value between those of π3s1/2 and π2d3/2 states. A similar mixed configuration is proposed for the Iπ=1/2+ ground state of $^{179}$Au. This mixing may provide evidence for triaxial shapes in the ground states in these nuclei.

International audience; Direct mass measurements of the low-spin 3/2− and high-spin 13/2+ states in the neutron-deficient isotopes Po195 and Po197 were performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE-CERN. These measurements allow the determination of the excitation energy of the isomeric state arising from the νi13/2 orbital in Po195,197. Additionally, the excitation energy of isomeric states of lead, radon, and radium isotopes in this region were obtained from α-decay chains. These excitation energies complete the knowledge of the energy systematics in the region and confirm that the 13/2+ states remain isomeric, independent of the number of valence neutrons.

The spectroscopic electric quadrupole moment of the neutron-deficient francium isotope 203 Fr was measured by using high-resolution collinear resonance ionization spectroscopy (CRIS) at the CERN Isotope Separation On-Line Device (ISOLDE) facility. A remeasurement of the 207 Fr quadrupole moment was also performed, resulting in a departure from the established literature value. A sudden increase in magnitude of the 203 Fr quadrupole moment, with respect to the general trend in the region, points to an onset of static deformation at N = 116 in the 87 Fr isotopic chain. Calculation of the static and total deformation parameters show that the increase in static deformation only cannot account for the observed departure of its relative charge radius from the 82 Pb chain. The spectroscopic electric quadrupole moment of the neutron-deficient francium isotope 203Fr was measured by using high-resolution collinear resonance ionization spectroscopy (CRIS) at the CERN Isotope Separation OnLine Device (ISOLDE) facility. A remeasurement of the 207Fr quadrupole moment was also performed, resulting in a departure from the established literature value. A sudden increase in magnitude of the 203Fr quadrupole moment, with respect to the general trend in the region, points to an onset of static deformation at N = 116 in the 87Fr isotopic chain. Calculation of the static and total deformation parameters show that the increase in static deformation only cannot account for the observed departure of its relative charge radius from the 82Pb chain.

Nuclear spins and precise values of the magnetic dipole and electric quadrupole moments of the ground states of neutron-rich Cu73–78 isotopes were measured using the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at the CERN On-Line Isotope Mass Separator (ISOLDE) facility. The nuclear moments of the less exotic Cu73,75 isotopes were remeasured with similar precision, yielding values that are consistent with earlier measurements. The moments of the odd-odd isotopes, and 2978Cu (N=49) in particular, are used to investigate excitations of the assumed doubly magic Ni78 core through comparisons with large-scale shell-model calculations. Despite the narrowing of the Z=28 shell gap between N∼45 and N=50, the magicity of Z=28 and N=50 is restored toward Ni78. This is due to weakened dynamical correlations, as clearly probed by the present moment measurements. Nuclear spins and precise values of the magnetic dipole and electric quadrupole moments of the ground-states of neutron-rich $^{76-78}$Cu isotopes were measured using the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at ISOLDE, CERN. The nuclear moments of the less exotic $^{73,75}$Cu isotopes were re-measured with similar precision, yielding values that are consistent with earlier measurements. The moments of the odd-odd isotopes, and $^{78}_{29}$Cu ($N=49$) in particular, are used to investigate excitations of the assumed doubly-magic $^{78}$Ni core through comparisons with large-scale shell-model calculations. Despite the narrowing of the $Z=28$ shell gap between $N\sim45$ and $N=50$, the magicity of $Z=28$ and $N=50$ is restored towards $^{78}$Ni. This is due to weakened dynamical correlations, as clearly probed by the present moment measurements.

Hyperfine structure and isotope shifts have been measured for the ground and isomeric states in the neutron-deficient isotopes 179–184Tl using the 276.9-nm transition. The experiment has been performed at the CERN-Isotope Separator On-Line facility using the in-source resonance-ionization laser spectroscopy technique. Spins for the ground states in 179,181,183Tl have been determined as I=1/2. Magnetic moments and changes in the nuclear mean-square charge radii have been deduced. By applying the additivity relation for magnetic moments of the odd-odd Tl nuclei the leading configuration assignments were confirmed. A deviation of magnetic moments for isomeric states in 182,184Tl from the trend of the heavier Tl nuclei is observed. The charge radii of the ground states of the isotopes 179–184Tl follow the trend for isotonic (spherical) lead nuclei. The noticeable difference in charge radii for ground and isomeric states of 183,184Tl has been observed, suggesting a larger deformation for the intruder-based 9/2− and 10− states compared to the ground states. An unexpected growth of the isomer shift for 183Tl has been found. ispartof: Physical Review C vol:95 issue:1 pages:1-12 status: published

Collinear laser spectroscopy was performed on the 63,64,66,68−82Ga isotopes with neutron numbers from N = 32 to N = 51. These measurements were carried out at the ISOLDE radioactive ion beam facility at CERN. Here we present the nuclear mean-square charge radii extracted from the isotope shifts and, for the lighter isotopes, new spin and moment values. New ground-state nuclear spin and moments were extracted from the hyperfine spectra of 63,70Ga, measured on an atomic transition in the neutral atom. The ground-state spin of 63Ga is determined to be I = 3/2. Analysis of the trend in the change in mean-square charge radii of the gallium isotopes demonstrates that there is no evidence of anomalous charge radii behavior in gallium in the region of N = 32. peerReviewed

Decay spectroscopy of Tl 184 has been performed at the CERN Isotope Separator On-Line (ISOLDE) facility. An excitation energy of 506.1(1) keV and a half-life of 47.1(7) ms of the intruder based (10 − ) state have been extracted. The internal decay characteristics of this state are determined and discussed, extending the systematics of such states in the even-mass thallium nuclei below neutron midshell at N=104 . The retardation factors of the isomeric M2 and E3 transitions are deduced and compared with retardation factors in neighboring odd-mass and even-mass thallium isotopes. The new information is combined with a review of hindered and unhindered α -decay data of Bi 187–192 populating levels in daughter nuclei Tl 183–188 and supports the interpretation of the intruder character of the (10 − ) state in Tl 184 .