The Nucleus 59Cu - Complex Structure, Shape Evolution, Exotic Decay Modes

Sammanfattning: High-spin states in the mass A~60 region were populated using the state-of-art gamma-ray spectrometers Gammasphere, Euroball, and GASP in conjunction with dedicated ancillary detectors. In particular, the 59Cu nucleus was studied in several experiments, and a very extensive level scheme was determined. It comprises more than 320 transitions connecting about 150 excited states. Relative to mass, it is the most extensive level scheme known to date. Next to the spherical states at low excitation energy eight regular sequences of high-energy gamma-ray transitions have been observed. They form rotational bands with various degree of deformation, which are interpreted in the light of the shell model and the configuration-dependent Cranked Nilsson-Strutinsky approach. One of the experiments was dedicated to the study of prompt particle decays. It revealed five prompt proton decays connecting five deformed states in three of the rotational bands in 59Cu with three spherical states in the daughter nucleus 58Ni. It is the first observation of the fine structure of the newly discovered prompt proton decay mode. The proton decays compete with the gamma decay-out from the second minimum of the nuclear potential into the low-spin spherical states in the first minimum of the potential. The discrete gamma decay-out mechanism of the yrast superdeformed band is investigated in detail. The nucleus 59Zn, the mirror partner of 59Cu, was identified for the first time, and the mirror symmetry of the T=1/2 A=59 pair is discussed.