Speaker
Description
In recent years, significant progress in nuclear structure theory has been driven by the availability of precise experimental data on short-lived nuclei with neutron-to-proton ratios far from those at the valley of stability in the nuclear chart. Collinear Laser Spectroscopy (CLS) is a powerful technique for obtaining nuclear ground-state properties such as spins, electromagnetic moments, and charge radii.
To access exotic radionuclides with very low production yields, the Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS) was conceived to enhance the sensitivity of fluorescence-based CLS. It is based on a unique high-energy (>10 keV) multi-reflection time-of-flight (MR-ToF) device, which utilizes two electrostatic mirrors to reflect ions back and forth for several thousands of revolutions. Hence, at MIRACLS, ion bunches are probed by the spectroscopy laser many times per measurement cycle to obtain higher measurement statistics compared to conventional, single-passage CLS. The resulting improvement in sensitivity allows the probing of isotopes with yields as low as 5 ions per second. In this way, radionuclides that would have been impossible to probe with conventional CLS techniques due to their low production yield and short half-lives now become accessible with the MIRACLS approach.
With MIRACLS, previous measurements have recently been extended to uncharted magnesium ($^{33, 34}$Mg) and cadmium ($^{98,99}$Cd) isotopes. The determination of charge radii of neutron-rich Mg isotopes allows us to probe the structure of nuclei in the $N=20$ island of inversion, an area of the nuclear chart where conventional shell closures disappear. Previously measured magnesium isotopes show a steady increase in charge radii up to $^{32}$Mg [1], with no indication of the shell closure, and our latest results on $^{33, 34}$Mg will provide valuable insight into the trend beyond $N=20$, acting as a stringent benchmark for new ab initio calculations motivated by our measurements.
In this oral contribution, the MIRACLS technique will be introduced and results from recent laser spectroscopy experiments on the aforementioned magnesium and cadmium isotopes will be presented.
References
[1] D. T. Yordanov et al., PRL, 108:042504 (2012)