Cross-shell excitations in Ca 46 studied with fusion reactions induced by a reaccelerated rare isotope beam

Abstract

Discovering unexplored high-spin states in neutron-rich nuclei can open up a new direction to study band structure and the associated shell structure in isospin-asymmetric many-body systems. However, experimental reach has so far been limited to neutron-deficient or stable nuclei which are preferentially produced in fusion reactions used in such studies. Here, we report the first γ-ray spectroscopy with fusion reactions using a reaccelerated rare-isotope beam of K45 performed at the ReA3 facility of the National Superconducting Cyclotron Laboratory. Using particle and γ-ray coincidence techniques, three new higher-lying states around 6 MeV and five new γ-ray transitions were identified for Ca46, suggesting three independent band structures formed from different particle-hole configurations. The rotational-like band built on the 02+ state is established up to the tentatively assigned 62+ state. New results are compared to large-scale shell model calculations, confirming the validity of the effective interaction describing particle-hole excitations across the Z=20 and N=28 shell gaps in the vicinity of doubly magic Ca48.