Speaker
Description
The assumption of universal magic numbers, i.e. closed nuclear shells, all across the nuclear chart has been a fundamental paradigm of the nuclear shell model. However, when exploring nuclides far away from stability, a disappearance of well-established shell closures can be encountered, which, for instance, manifests itself in the island of inversion around $N = 20$ [1]. Describing this shell evolution from first principles is a formidable task for nuclear theory. Recently, nuclear ab-initio methods have been able to expand their reach also into open shell nuclei. This advance now allows for ab-initio calculations of nuclear observables within the $N = 20$ island of inversion [2]. In order to deepen our understanding of this region of nuclides and challenge the predictive power of modern nuclear theory, experimental knowledge about the nuclear charge radii of neutron-rich magnesium (Z = 12) isotopes is crucial.
A powerful tool to access nuclear charge radii is collinear laser spectroscopy (CLS) [3]. However, to extend previous measurements up to $^{32}$Mg [4] and explore the more exotic isotopes $^{33,34}$Mg with very low production yields at radioactive ion beam facilities, more sensitive methods have to be envisioned. The novel Multi-Ion-Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS) at ISOLDE/CERN [5] combines the high spectral resolution of conventional fluorescence-based CLS with high experimental sensitivity. This is achieved by trapping ion bunches in a Multi-Reflection Time of Flight (MR-ToF) device, in which the ions bounce back and forth between two electrostatic mirrors. Hence, the laser-ion interaction time is increased with each revolution in the MR-ToF apparatus, while retaining the high resolution of CLS.
Very recently in November 2024, we had a successful experimental campaign were we measured hyperfine spectra of $^{33,34}$Mg. This oral contribution will introduce the MIRACLS concept and present the first preliminary data of Mg charge radii from the aforementioned measurement.
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