Rotational Bands in the Doubly Magic Nucleus N[number sign]<sup location=''pre''>56i

Structures of the medium- to high-spin states in the doubly magic nucleus [sup 56]Ni have been investigated using the reaction [sup 28]Si([sup 36]Ar,thinsp2[alpha]) and the [gamma] -ray spectrometer Gammasphere in conjunction with the 4[pi] 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 [sup 58]Cu , partially decays via proton emission into the ground state of [sup 55]Co . Predictions of extensive large-scale shell-model and cranked Hartree-Fock and Hartree-Fock-Bogolyubov calculations are compared with the experimental data. [copyright] [ital 1999] [ital The American Physical Society]