Coexisting normal and intruder configurations in 32Mg

Situated in the so-called island of inversion, the nucleus Mg-32 is considered as an archetypal example of the disappearance of magicity at N = 20. We report on high statistics in-beam spectroscopy of Mg-32 with a unique approach, in that two direct reaction probes with different sensitivities to the underlying nuclear structure are employed at the same time. More specifically, states in Mg-32 were populated by knockout reactions starting from Mg-33 and Si-34, lying inside and outside the island of inversion, respectively. The momentum distributions of the reaction residues and the cross sections leading to the individual final states were confronted with eikonal-based reaction calculations, yielding a significantly updated level scheme for Mg-32 and spin-parity assignments. By fully exploiting observables obtained in this measurement, a variety of structures coexisting in Mg-32 was unraveled. Comparisons with theoretical predictions based on shell-model overlaps allowed for clear discrimination between different structural models, revealing that the complete theoretical description of this key nucleus is yet to be achieved. (C) 2021 Published by Elsevier B.V.

Automated summary

Research on the Mg-32 nucleus, situated in the island of inversion, utilized two direct reaction probes with different sensitivities to explore its structure. The experiment provided an updated level scheme and structural information, revealing the coexistence of various structures in Mg-32. Further theoretical studies are needed to fully understand the complexity of this key nucleus.