In-beam γ-ray spectroscopy of 35Mg and 33Na

Excited states in the very neutron-rich nuclei Mg-35 and Na-33 were populated in the fragmentation of a Si-38 projectile beam on a Be target at 83 MeV/u beam energy. We report on the first observation of gamma-ray transitions in Mg-35, the odd-N neighbor of Mg-34 and Mg-36, which are known to be part of the 'island of inversion around N = 20. The results are discussed in the framework of large-scale shell-model calculations. For the A = 3Z nucleus Na-33, a new gamma-ray transition was observed that is suggested to complete the gamma-ray cascade 7/2(+) -> 5/2(+) -> 3/2(gs)(+) connecting three neutron two-particle-two-hole intruder states that are predicted to form a close-to-ideal K = 3/2 rotational band in the strong-coupling limit.