EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH Proposal to the ISOLDE and Neutron Time-of-Flight Committee

The second 0 + state in 34 Si, of high importance for the understanding of the island of inversion at N=20, has been recently observed [Rotaru12] through the beta decay of a predicted long-lived low-lying isomeric 1 + state in 34 Al. We intend to measure the unknown excitation energy of this isomer using the ISOLTRAP Penning-trap mass spectrometer. Since a recent experiment at ISOLDE (IS-530) [Negoita13] showed that the full beta strength in the decay of 34 Mg goes through this 1 + state in 34 Al, we propose to perform a direct mass measurement of the daughter 34 Al ions trapped after the decay of 34 Mg. Mass measurements indicate that the 4 ground state in 34 Al may be an excited state, the ground state being therefore the intruder 1 + state. In another run, we propose to perform a remeasurement of the mass of the 4 ground state.