Spin and magnetic moment of Mg-33: Evidence for a negative-parity intruder ground state

We report on the first determination of the nuclear ground-state spin of Mg-33, I=3/2, and its magnetic moment, mu=-0.7456(5) mu(N), by combining laser spectroscopy with nuclear magnetic resonance techniques. These values are inconsistent with an earlier suggested 1 particle-1 hole configuration and provide evidence for a 2 particle-2 hole intruder ground state with negative parity. The results are in agreement with an odd-neutron occupation of the 3/2[321] Nilsson orbital at a large prolate deformation. The discussion emphasizes the need of further theoretical and experimental investigation of the island of inversion, a region previously thought to be well understood.We report on the first determination of the nuclear ground-state spin of Mg-33, I = 3/2, and its magnetic moment, mu = -0.7456(5) mu(N), by combining laser spectroscopy with nuclear magnetic resonance techniques. These values are inconsistent with an earlier suggested 1 particle-1 hole configuration and provide evidence for a 2 particle-2 hole intruder ground state with negative parity. The results are in agreement with an odd-neutron occupation of the 3/2[321] Nilsson orbital at a large prolate deformation. The discussion emphasizes the need of further theoretical and experimental investigation of the island of inversion, a region previously thought to be well understood.status: publishe