Heavy calcium nuclei weigh in

Abstract

The configurations of calcium nuclei make them good test cases for studies of nuclear properties. The measurement of the masses of two heavy calcium nuclei provides benchmarks for models of atomic nuclei. See Letter p.346 The calcium atom provides an ideal system for the study of nuclear shell evolution, from the valley of stability to the limits of existence. Although predictions for the masses of the neutron-rich isotopes 51Ca and 52Ca have been tested by direct measurements, it is an open question as to how nuclear masses evolve for heavier calcium isotopes. Frank Wienholtz and colleagues report the mass determination of the exotic calcium isotopes 53Ca and 54Ca, using a multi-reflection time-of-flight mass spectrometer. The results provide key information for theoretical models and show that a description of extreme neutron-rich nuclei can be closely connected to a deeper understanding of nuclear forces.