Rotational bands in the doubly magic nucleus ⁵⁶Ni

Structures of the medium- to high-spin states in the doubly magic nucleus ⁵⁶Ni have been investigated using the reaction ²⁸Si(³⁶Ar,2α) and the γ-ray spectrometer Gammasphere in conjunction with the 4π charged-particle detector array Microball. Two well-deformed rotational bands have been identified. There is evidence that one of the bands, which is identical to a sequence in the odd-odd neighbor ⁵⁸Cu, partially decays via proton emission into the ground state of ⁵⁵Co. Predictions of extensive large-scale shell-model and cranked Hartree-Fock and Hartree-Fock-Bogolyubov calculations are compared with the experimental data.