Accurate nuclear radii and binding energies from a chiral interaction. Nuclear charge radii of potassium isotopes beyond N = 28. Evidence for a new nuclear ‘magic number’ from the level structure of 54Ca. Masses of exotic calcium isotopes pin down nuclear forces. Evolution of shell structure in neutron-rich calcium isotopes. Three-body forces and shell structure in calcium isotopes. The magic nature of 133Sn explored through the single-particle states of 133Sn. 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. The experimental results are complemented by state-of-the-art theoretical calculations. Here we present the first measurements of the charge radii of 49,51,52Ca, obtained from laser spectroscopy experiments at ISOLDE, CERN. 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. 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. Despite being a complex many-body system, the atomic nucleus exhibits simple structures for certain ‘magic’ numbers of protons and neutrons.

Charge of calcium