High-precision measurements of the hyperfine structure of cobalt ions in the deep ultraviolet range

High-precision hyperfine structure measurements were performed on stable, singly-charged [Formula: see text]Co ions at the IGISOL facility in Jyväskylä, Finland using the collinear laser spectroscopy technique. A newly installed light collection setup enabled the study of transitions in the 230 nm wavelength range from low-lying states below 6000 cm[Formula: see text]. We report a 100-fold improvement on the precision of the hyperfine A parameters, and furthermore present newly measured hyperfine B paramaters

Pinning down electron correlations in RaF via spectroscopy of excited states

We report the spectroscopy of 11 electronic states in the radioactive molecule radium monofluoride (RaF). The observed excitation energies are compared with state-of-the-art relativistic Fock-space coupled cluster (FS-RCC) calculations, which achieve an agreement of >99.71% (within ~8 meV) for all states. High-order electron correlation and quantum electrodynamics corrections are found to be important at all energies. Establishing the accuracy of calculations is an important step towards high-precision studies of these molecules, which are proposed for sensitive searches of physics beyond the Standard Model.Comment: Submitted for publicatio

First demonstration of Doppler-free 2-photon in-source laser spectroscopy at the ISOLDE-RILIS

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Charge radii of exotic potassium isotopes challenge nuclear theory and the magic character of N=32

A Publisher Correction to this article was published on 24 February 2021: https://www.nature.com/articles/s41567-021-01192-5Nuclear charge radii are sensitive probes of different aspects of the nucleon-nucleon interaction and the bulk properties of nuclear matter, providing a stringent test and challenge for nuclear theory. Experimental evidence suggested a new magic neutron number at N = 32 (refs. (1-3)) in the calcium region, whereas the unexpectedly large increases in the charge radii(4,5) open new questions about the evolution of nuclear size in neutron-rich systems. By combining the collinear resonance ionization spectroscopy method with beta-decay detection, we were able to extend charge radii measurements of potassium isotopes beyond N = 32. Here we provide a charge radius measurement of K-52. It does not show a signature of magic behaviour at N = 32 in potassium. The results are interpreted with two state-of-the-art nuclear theories. The coupled cluster theory reproduces the odd-even variations in charge radii but not the notable increase beyond N = 28. This rise is well captured by Fayans nuclear density functional theory, which, however, overestimates the odd-even staggering effect in charge radii. These findings highlight our limited understanding of the nuclear size of neutron-rich systems, and expose problems that are present in some of the best current models of nuclear theory.Peer reviewe

Level structure of <math><mmultiscripts><mi>Ac</mi><mprescripts/><none/><mn>221</mn></mmultiscripts></math> and <math><mmultiscripts><mi>Fr</mi><mprescripts/><none/><mn>217</mn></mmultiscripts></math> from decay spectroscopy, and reflection asymmetry in <math><mmultiscripts><mi>Ac</mi><mprescripts/><none/><mn>221</mn></mmultiscripts></math>

International audiencePa225 and Ac221 were produced at the IGISOL facility through proton-induced fusion-evaporation reactions and have been studied using α-particle spectroscopy, as well as α-γ and α-electron coincidence spectroscopy. The level scheme of Ac221, daughter of Pa225, and of Fr217, daughter of Ac221 were reconstructed. An interpretation of Ac221 levels as K=5/2± and K=3/2± parity-doublet bands is proposed. Such bands appear in reflection-asymmetric models and would be an indication of a static reflection asymmetric shape for Ac221

A compact linear Paul trap cooler buncher for CRIS

© 2019 The Authors A gas-filled linear Paul trap for the Collinear Resonance Ionisation Spectroscopy (CRIS)experiment at ISOLDE, CERN is currently under development. The trap is designed to accept beam from both ISOLDE target stations and the CRIS stable ion source. The motivation for the project along with the current design, simulations and future plans, will be outlined.status: publishe

Optimising the Collinear Resonance Ionisation Spectroscopy (CRIS) experiment at CERN-ISOLDE

© 2019 The CRIS experiment at CERN-ISOLDE is a dedicated laser spectroscopy setup for high-resolution hyperfine structure measurements of nuclear observables of exotic isotopes. Between 2015 and 2018 developments have been made to improve the background suppression, laser-atom overlap and automation of the beamline. Furthermore, a new ion source setup has been developed for offline studies. Here we present the latest technical developments and future perspectives for the experiment.status: publishe

Probing the single-particle behavior above Sn-132 via electromagnetic moments of Sb-133,Sb-134 and N=82 isotones

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High-precision multi-photon ionization of accelerated laser-ablated species

We demonstrate that the pulsed-time structure and high-peak ion intensity provided by the laser-ablation process can be directly combined with the high resolution, high efficiency, and low background offered by collinear resonance ionization spectroscopy. This simple, versatile, and powerful method offers new and unique opportunities for high-precision studies of atomic and molecular structures, impacting fundamental and applied physics research. We show that even for ion beams possessing a relatively large energy spread, high-resolution hyperfine-structure measurements can be achieved by correcting the observed line shapes with the time-of-flight information of the resonantly ionized ions. This approach offers exceptional advantages for performing precision measurements on beams with large energy spreads and allows measurements of atomic parameters of previously inaccessible electronic states. The potential of this experimental method in multidisciplinary research is illustrated by performing, for the first time, hyperfine-structure measurements of selected states in the naturally occurring isotopes of indium, ^{113,115}In. Ab initio atomic-physics calculations have been performed to highlight the importance of our findings in the development of state-of-the-art atomic many-body methods, nuclear structure, and fundamental-physics studies

Analytic response relativistic coupled-cluster theory: the first application to indium isotope shifts

status: publishe