– 4 – Shape Coexistence at the Borderline of the ’Island of Inversion’: First Identification of the E0 Decay from the Deformed 0+2 State in 30Mg ♦

A shape coexistence of spherical and deformed 0+ states is predicted to exist around the,island of inversion ’ in neutron-rich Mg isotopes. While the closed-shell nucleus 32Mg exhibits a highly deformed ground state (β ∼ 0.51), the ground state of 30Mg is expected to be much less de-formed. The (deformed) excited 0+ state is predicted by theory between 1.7 and 2 MeV [1] but has not yet been ob-served experimentally. However, recent experimental find-ings create confidence that the experimental identification of shape coexistence in 30Mg is within reach. Resulting from fast timing γ-spectroscopy studies [2] the 1789 keV level in 30Mg emerged as a strong candidate for the de-formed first excited 0+ state due to its long lifetime of 3.9 ns and the absence of a ground state γ transition, as can be seen in the level scheme of 30Mg shown in Fig. 1. This triggered our search for the deformed 0+2 state in 30Mg via conversion electron spectroscopy within the framework of the ISOLDE IS414 collaboration