2016 at the Collinear Resonance Ionisation Spectroscopy (CRIS) experiment

nrpages: 14status: publishe

Quadrupole moment of Fr-203

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 On-Line Device (ISOLDE)facility. A remeasurement of the 207Fr quadrupole momentwas 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.status: publishe

Quadrupole moment of Fr-203

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 On-Line Device (ISOLDE)facility. A remeasurement of the 207Fr quadrupole momentwas 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.status: publishe

Dipole and quadrupole moments of Cu73-78 as a test of the robustness of the Z=28 shell closure near Ni-78

Nuclear spins and precise values of the magnetic dipole and electric quadrupole moments of the ground states of neutron-rich 73–78Cu 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 73,75Cu isotopes were remeasured with similar precision, yielding values that are consistent with earlier measurements. The moments of the odd-odd isotopes, and 78 29Cu (N =49) in particular, are used to investigate excitations of the assumed doubly magic 78Ni 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 78Ni.This is due to weakened dynamical correlations, as clearly probed by the present moment measurements.status: publishe

Laser-spectroscopy studies of the nuclear structure of neutron-rich radium

The neutron-rich radium isotopes, 222−233 Ra, were measured with Collinear Resonance Ionization Spectroscopy (CRIS) at the ISOLDE facility, CERN. The hyperfine structure of the 7s2 1S0 → 7s7p 3P1 transition was probed, allowing measurement of the magnetic moments, quadrupole moments, and changes in mean-square charge radii. These results are compared to existing literature values, and the new moments and change in mean-square charge radii of 231Ra are presented. Low-resolution laser spectroscopy of the very neutron-rich 233Ra has allowed the isotope shift and relative charge radius to be determined for the first time.status: publishe

Measurement and microscopic description of odd-even staggering of charge radii of exotic copper isotopes

Nuclear charge radii globally scale as A1/3, with A the atomic mass number, and isotopes with an odd number of neutrons are usually slightly smaller in size than their even-neutron neighbours. This odd-even staggering, ubiquitous throughout the nuclear landscape, varies with the number of protons and neutrons, and poses a substantial challenge for nuclear theory. Here, we report measurements of the charge radii of short-lived copper isotopes up to the very exotic 78Cu (with proton number Z = 29 and neutron number N = 49), produced at only 20 ions/s, using the Collinear Resonance Ionisation Spectroscopy method at the Isotope mass Separator On-Line facility (ISOLDE) at CERN. We observe an unexpected reduction in the odd-even staggering for isotopes approaching the N = 50 shell gap. To describe the data, we applied models based on nuclear Density Functional Theory and A-body Valence-Space In-Medium Similarity Renormalization Group theory. Through these comparisons, we demonstrate a relation between the global behaviour of charge radii and the saturation density of nuclear matter, and show that the local charge radii variations, which reflect the many-body polarization effects, naturally emerge from A-body calculations fitted to properties of A ≤ 4 nuclei.status: accepte