Nuclear Physics(DNP)
Physique nucléaire (DPN)

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Corina ANDREOIU
University of Guelph

Doorway States in the Gamma Decay-Out of the Yrast Superdeformed Band in 59Cu

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Nuclei with atomic mass number around 60 are among the fastest rotating nuclei known in Nature. They can spin with an angular velocity of about 1.5-2.0 MeV. At these rotational frequencies, highly- or super-deformed shapes are favored over the normally deformed shapes. For the superdeformed states to be pure they need to be shielded from the normally deformed states by an energy barrier in the deformation coordinates. These states prefer to decay by emitting gamma-ray radiation to the normally deformed states in the same nucleus, or by fast (prompt) particle decays in spherical states of the corresponding daughter nucleus. The shape change occurring in the decay-out implies a substantial rearrangement of nucleonic states. Especially the nucleonic states from higher shells, which are occupied in the superdeformed bands, need to be vacated. This process is facilitated by vibrational coupling through the barrier between the superdeformed state and doorway states, which in turn typically are coupled to a very large number of normally states.

The decay-out process of the yrast superdeformed band in 59Cu has been recently investigated and compared with decay-out mechanisms in heavier nuclei. The firm determination of spin, parity, excitation energy, and configuration of the states involved in this process constitutes a unique situation for a detailed understanding of the decay-out mechanism. Doorway states involved in this mechanism have been observed and are classified for the first time.