From Calcium to Cadmium: Testing the Pairing Functional through Charge Radii Measurements of 100−130Cd

Differences in mean-square nuclear charge radii of 100–130Cd are extracted from high-resolution collinear laser spectroscopy of the 5s 2S1/2→5p 2P3/2 transition of the ion and from the 5s5p3P2→5s6s3S1 transition in atomic Cd. The radii show a smooth parabolic behavior on top of a linear trend and a regular odd-even staggering across the almost complete sdgh shell. They serve as a first test for a recently established new Fayans functional and show a remarkably good agreement in the trend as well as in the total nuclear charge radius

Frequency-comb referenced collinear laser spectroscopy of Be+ for nuclear structure investigations and many-body QED tests

Transition frequencies of the 2s2S1/2→2p2P1/2,3/2 transitions in Be+ were measured in stable and short-lived isotopes at ISOLDE (CERN) using collinear laser spectroscopy and frequency-comb-referenced dye lasers. Quasi-simultaneous measurements in copropagating and counterpropagating geometry were performed to become independent from acceleration voltage determinations for Doppler-shift corrections of the fast ion beam. Isotope shifts and fine-structure splittings were obtained from the transition frequencies measured with a frequency comb with accuracies better than 1 MHz and led to a precise determination of the nuclear charge radii of 7,10−12Be relative to the stable isotope 9Be. Moreover, an accurate determination of the 2p fine-structure splitting allowed a test of high-precision bound-state QED calculations in the three-electron system. Here, we describe the laser spectroscopic method in detail, including several tests that were carried out to determine or estimate systematic uncertainties. Final values from two experimental runs at ISOLDE are presented, and the results are discussed.28 pages, 12 figuresstatus: publishe

Ground-state electromagnetic moments of calcium isotopes

Background: The neutron-rich calcium isotopes have gained particular interest as evidence of closed-shell structures has recently been found in two exotic nuclei, at N = 32 and N = 34. Additionally, the study of such neutron-rich systems has revealed new aspects of nuclear forces, in particular regarding the role of three-nucleon forces. Purpose: We study the electromagnetic properties of Ca isotopes around the neutron number N = 32. Methods: High-resolution bunched-beam collinear laser spectroscopy was used to measure the optical hyperfine spectra of the 43−51Ca isotopes. Results: The ground-state magnetic moments of 49,51Ca and quadrupole moments of 47,49,51Ca were measured for the first time, and the 51Ca ground-state spin I = 3/2 was determined in a model-independent way. Our experimental results are compared with state-of-the-art shell-model calculations using both phenomenological interactions and microscopic interactions derived from chiral effective field theory. Conclusions: The results for the ground-state moments of neutron-rich isotopes are in excellent agreement with predictions of interactions derived from chiral effective field theory including three-nucleon forces. Lighter isotopes illustrate the presence of particle-hole excitations of the 40Ca core in their ground state. Our results provide a critical test of modern nuclear theories, and give direct answer to the evolution of ground-state electromagnetic properties in the Ca isotopic chain across three doubly closed-shell configurations at N = 20, 28, 32 of this unique system.Accepted as a Rapid Communication in Physical Review Cstatus: publishe

Simple Nuclear Structure in Cd111-129 from Atomic Isomer Shifts

Isomer shifts have been determined in 111–129Cd by high-resolution laser spectroscopy at CERN ISOLDE. The corresponding mean square charge-radii changes, from the 1/2+ and the 3/2+ ground states to the 11/2− isomers, have been found to follow a distinct parabolic dependence as a function of the atomic mass number. Since the isomers have been previously associated with simplicity due to the linear mass dependence of their quadrupole moments, the regularity of the isomer shifts suggests a higher order of symmetry affecting the ground states in addition. A comprehensive description assuming nuclear deformation is found to accurately reproduce the radii differences in conjunction with the known quadrupole moments. This intuitive interpretation is supported by covariant density functional theory.status: publishe

Unexpectedly large charge radii of neutron-rich calcium isotopes

Despite being a complex many-body system, the atomic nucleus exhibits simple structures for certain ‘magic’ numbers of protons and neutrons. The calcium chain in particular is both unique and puzzling: evidence of doubly magic features are known in 40,48Ca, and recently suggested in two radioactive isotopes, 52,54Ca. Although many properties of experimentally known calcium isotopes have been successfully described by nuclear theory, it is still a challenge to predict the evolution of their charge radii. Here we present the first measurements of the charge radii of 49,51,52Ca, obtained from laser spectroscopy experiments at ISOLDE, CERN. The experimental results are complemented by state-of-the-art theoretical calculations. The large and unexpected increase of the size of the neutron-rich calcium isotopes beyond N = 28 challenges the doubly magic nature of 52Ca and opens new intriguing questions on the evolution of nuclear sizes away from stability, which are of importance for our understanding of neutron-rich atomic nuclei.Submitted version. See original publication (doi:10.1038/nphys3645) for final versionstatus: publishe